Aluminium Extrusions - Technical Design Guide

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ALUMINIUM EXTRUSIONS

— a technical design guide

i ; c

For free, objective advice on all matters relating to aluminium extrusions contact:

The Shapemakers Information Service Broadway House Calthorpe Road Birmingham B151TN

Tel: 021 4562276 Fax: 021 4562274

ALUMINIUM EXTRUSIONS — a technical design guide

PUBLISHED BY THE SHAPEMAKERS — the information arm of the UK Aluminium Extruders Association

'I

© The Shapemakers

Broadway House Calthorpe Road Birmingham B151TN

DISCLAIMER

This book is intended for use by technically skilled personnel. The use of the information contained herein by such technically skilled personnel, is at the risk of the user. While all reasonable skill and care has been exercised in the preparation of this book, there are no warranties, express or implied, as to the accuracy or completeness of this work, either by the author or the publisher, both of whom deny responsibility or liability for any results obtained or damages caused as a consequ- ence of the use thereof .The publisher and the author hereof grant no licence with this book and disclaim all liability for suitability, practicability, infringement of property rights of third parties or non-conformance with any codes, standards or regulations.

ACKNOWLEDGEMENT TO BSI

Extracts from British Standards are reproduced with the permission of BSI. Com- plete copies of the Standards can be obtained by post from BSI Sales, Linford Wood, Milton Keynes, MK1 4 6LE.

First published October 1989 Reprinted July 1991 Reprinted August 1994

Printed in Great Britain by St Edmundsbury Press Ltd Bury St Edmunds, Suffolk

VI

PREFACE to the 1994 reprint — by Howard Spencer

Since this manual was originally published, British Standards have published a new aluminium structural code, BS 8118 1991, which supersedes BS CP118 1969:

— Part 1: Code of Practice for Design — Part 2: Specification for Materials, Workmanship and Protection

There is at present a change-over period where both design codes are valid, but at some time in the future BS CP118 will be withdrawn. This new code is intended to

bring aluminium structural design into line with other metals and also with European standard codes, which will simplify future preparation of an overall European structural code for aluminium.

I intend here to give users of the manual a very brief outline of how the new codes will

affect the use of aluminium. It is impossible to go into too much detail. Those

requiring additional information should refer to the codes themselves, available from British Standards (see address below).

The New Code

The new code is based around a new design approach, based on the principle of 'limit state design'. This principle is concerned with ensuring that any given structure can carry the loads and forces placed upon it without failure, up to a pre-determined limit. The factored resistance of a structure must therefore never be less than the factored loading. The following equation can be applied:

Y12R = Y4S

= overall resistance factor R = calculated resistance

= overall loading factor S = maximum design load

The resistance is calculated from the effective sectional properties, the limiting stress and a material and connection factor. The loading effect is factored for type of load, i.e. dead load, imposed load, wind load and temperature induced forces.

The new code also covers the calculation of elastic instabilities. Aluminium sections with very wide, thin elements are susceptible to local buckling under high compressive stresses. The relevant calculations have been simplified in the new code by adopting a classification system based upon a factored relationship between the width or depth of the element and the thickness. Three categories are listed for moment resistance — compact, semi-compact and slender. For compact sections,

I

no further check is required as they will not suffer from local buckling. (For example, afl the sections listed in BS 1161 "Aluminium Structural Sections" are compact.) Semi-compact resistance is obtained by using the quoted limiting stress of the material. Sections defined as slender, however, are assessed on the basis of a reduced effective wall thickness and the extent of the reduction can be obtained from a series of curves. Only the compact and slender categories are allowed when calculating the axial resistance of struts.

The recommendation for deflection levels has not changed, but a word of caution is included in the specification against imposing too tight a standard on aluminium structures when the particular application does not merit it.

The section on welding has been greatly extended from that in the original code. Guidance is provided on the design of welds taking into account the strength of the weld metal and a partial reduction in strength in the heat affected zone of the parent metal. The limiting stresses for both filler and parent metal are given with factors for designing butt and lap joints for both traverse and longitudinal welds.

Adhesively bonded joints are only recommended for secondary stressed connections. The factored resistance of a bonded joint can be calculated from an expression containing a failing standard, obtained from testing, and a material connection factor for bonded joints, If validated test data is available, it can be used in the joint resistance expression.

The section on fatigue has also been greatly extended, incorporating information from both UK and European research. The tables for both welded and non-welded structures contain detailed sketches illustrating the type of construction, direction of stress, fluctuation and possible crack locations. The tables are based upon BS 5400 Part 10: Bridges and give the classification for a range of structural detail.

Full supporting data including mathematical formulae relevant to the design calculations and curves used in the code are set out in the appendices of the new code and can be used to assist computer aided design.

All references in the manual to BS CP1 18 now apply to BS 8118 and, as the new code does not cover permissible stress levels, table 3.2 and figure 3.3 are not applicable. Tables 3.4 and 6.11 have also been modified as the standard elastic modulus for all wrought aluminium alloys is now 70,000 N/mm2

Reviewing the worked examples given in the manual, the pedestrian balustrade (pages 113—122) results in marginal modifications to some sections when worked to the new code but gives similar overall results. In the case of the unloading ramp, however (pages 111—112) there could be a slight saving in the thickness of the section when meeting the new code. The column example (pages 123—125) refers to alloy 2014 AT6 which is no longer a standard material in the new code. Although it can be used, the limit state stresses would have to be established and, in this case, the section thickness would have to be slightly increased.

VIII

Competently used, the old code should still give an acceptable level of design. It should be noted, however, that if the calculations are to be officially approved then only the new code is valid. Furthermore, the up-dated information in the new code can result in a more economical structural use of the material.

Codes referred to: BS 8118 Part 1: 1991 Code of Practice for Design BS 8118 Part 2: 1991 Specification for Materials,

Workmanship and Protection

These are available from: Sales Dept, BSI, Linford Wood, Milton Keynes, MK14 6LE, or any HMSO.

ix

INTRODUCTION

Aluminium is a highly versatile, light and strong material which can be produced in a variety of alloys and extruded into an almost infinite number of shapes. This powerful combination of factors enables the user to be more innovative and facilitates cost- effective design.

Comprising 8% of the earth's crust, aluminium is a plentiful resource. It is a modern material, first used in commercial production in 1886. Since then, the list of applications has grown immensely. Now, designers working in a whole range of different sectors, including general engineering, construction, transport, packaging and consumer products, are reaping the benefits gained by using aluminium extrusions.

The Shapemakers was established by the Aluminium Extruders Association (AEA) in 1984 to provide independent guidance on all matters relating to extruded aluminium. Representing the UK's top extrusion companies, The Shapemakers is able to draw upon these companies' considerable resources and expertise.

This technical design guide contains a wealth of information on aluminium itself, as well as giving details on the extrusion process, fabrication and finishing. Also included is a comprehensive design section, which outlines the important design considerations and shows a number of worked examples.

For reasons of clarity, only six alloys have been incorporated into the main body of the manual. These have been carefully selected to illustrate the various uses of alloys — from general purpose to high strength. Additional alloys are listed in the appendices. For details of the availability of any alloy listed in this manual, please contact the Shapemakers Information Service in Birmingham, Tel: 021 456 2276.

The AEA would like to thank The Shapemakers' technical consultant, Howard Spencer, for all his work in compiling this design guide. A special thanks also goes to The Shapemakers' members, Hugo Ravesloot, Jim Peach and Chris Forman.

Derek Phillips

Chairman of The Shapemakers

CONTENTS

PRINCIPLES OF EXTRUSION 1

MATERIAL SPECIFICATIONS 25

MECHANICAL PROPERTIES 33

DURABILITY 45

SURFACE FINISHING 55

FABRICATION 63

CONDUCTIVITY 87

TEMPERATURE 93

FIRE 97

CARE AND CONTROL 101

DESIGN 105

GLOSSARY OF TERMS 127

APPENDICES 133


SECTION 1 - PRINCIPLES OF EXTRUSION

CONTENTS

Title Page No.

EXTRUSION PROCESS 4 Direct Extrusion 4 Indirect Extrusion 5 Hollow Sections 6

EXTRUDABILITY 7 Extrusion Ratio 7 Shape Factor 7

SIZE 8

THICKNESS 8

SLOTS 10

SECTION CLASSIFICATION 11

CORNERS 11

TOLERANCES 12

List of Figures

Fig No. Title Page No.

1.1 The Direct Extrusion Process 4

1.2 The Differing Operating Principles of Direct and Indirect Extrusion 5

1.3 Extrusion of a Hollow Section 6

1 .4 Thick to Thin Transitions in Extrusion Cross Section 10

1.5 Pressure Hinge 10

1.6 Slot Aspect Ratios 10

1.7 Standard Section Types 11

List of Tables

No. Title Page No.

1.1 Shape Factor Value 8

1.2 A Guide to Minimum Thickness 9

1.3 Tolerances on Diameter of Round Bar Intended for use on Automatic Lathes 12

1.4 Tolerances on Widths Across Flats of Hexagonal Bar for the Manufacture of Nut & Bolts 13

1.5 Tolerances on Diameter of Round Bar in the Controlled Stretched Condition 13

2

List of Tables (contd.)

No Title Page No.

1.6 Tolerances on Diameter or Width Across Flats of Bars for General Purposes and on Width of Solid or Hollow Regular Sections 14

1 .7 Angular Tolerances for Extruded Regul& Sections 15

1.8 Permitted Corner Radii 15

1 .9 Tolerances on Wall Thicknesses of Extruded Round Tube (classes A, B and C). 16

1.10 Tolerances on Thickness of Bars and Regular Sections 17

1.11 Tolerances on Open End of Channels and L Beams 18/19

1.12 Tolerances on the Outside Diameter of All Extruded Round Tube and on the Inside Diameter of Class A and Class B Extruded Round Tube 20

1.13 Tolerances on Thickness of Hollow Sections (classes A and B) 21

1 .14 Tolerances on Straightness for Extruded Bar, Regular Sections and Extruded Round Tubes 22

1.15 Tolerances on Length for All Materials Supplied in Fixed Cut Lengths 23

1 .16 Tolerances on Concavity and Convexity for Extruded Solid and Hollow Sections 23

1 .17 Tolerance on Twist for Extruded Solid and Hollow Sections 24

3

EXTRUSION PROCESS

Direct Extrusion

The direct extrusion process can be clearly seen in the schematic diagram in Fig. 1.1. Cylindrical aluminium alloy billets of cast or extruded manufacture are heated to between 4500 and 500° before being loaded into a container and the billet squeezed through a die orifice using ram pressures of up to 68OMPa. The die is supported by a series of back dies and bolsters so that the main press load is transferred to a front platen.

Fig. 1.1 - The Direct Extrusion Process

4

Platen

Ram cross head

Stem

Liner Die slide

Dummy block

Container

Billet

Die

Backer

Sub bolster

Extruded section

On leaving the die the temperature of the section is more than 500°C and with heat

treatable afloys the quenching, or solution heat treatment, takes place in the production line. This can be by water bath, water spray or forced-draught air, with the latter being particularly useful for thin sections. The approximate temperature drop during the traverse of the quench box is 250°C. To avoid distortion care has to be exercised in handling sections with extreme aspect ratios and large variations in thickness.

After extrusion the section is guided down the table by a puller on to a slatted moving belt. Modern Pullers are based on linear motor s,stems and operate on tables up to 40 metres long. On completion of an extruded length, the section is sheared at the

press end and lifted from the slatted table by eccentric pivoted arms. It is then transferred by a walking beam or multi-belt transfer table to the stretcher bay where it is given a controlled stretch to straighten and remove minor mis-alignments. The section is then taken and cut to ordered lengths on high speed tungsten carbide tipped saws.

If the material is required in the solution heat treated condition (T4) it is released at this stage. If the full strength aged material (T6) is required, it is given a precipitation treatment before release. In the case of the T5 temper, there is limited cooling at the press exit and the material goes directly to precipitation treatment.

Indirect Extrusion

In the traditional direct method of extrusion, as described above, the die is stationary and the press ram applies pressure on to the billet. In the indirect method, the ram carries the die and applies pressure on to the stationary billet, in the opposite direction of extrusion. There can be variation to this basic concept, but in every case the billet remains stationary in relation to the container, thereby keeping friction loss to a bare minimum. See Fig. 1.2. Die

Fig. 1.2 - The Differing Operating Principles of Direct and Indirect Extrusion

5

Extrusion

Die Billet

Extrusion Indirect extrusion

Die Billet

Hollow Sections

A bridge or 'port-hole die' is usually used to make hollow sections. A solid billet is forced, under pressure, through a composite die tool that first divides the metal into two or more separate streams which then flows down under the bridge to be pressure welded together and emerge, as an extruded section, through the orifice formed between the mandrel nose and the outer section shape which has been cut in the die. See Fig. 1.3.

Any sample taken across the section would show an integral material quality with no reduction of strength in the weld areas. Inspection methods are usually by destructive test sampling in line with that laid down by the British Standards for scaffold tubing in specification BS 1139. Production methods for this kind of section are well established and extruders will be pleased to advise on the feasibility of producing any hollow section.

Some caution must be exercised, however where thin hollow sections are required in the stronger alloys, particularly from the bridge or port-hole production methods. Hollow sections are usually produced in these alloys by using centre mandrels that are not connected to the die but are passed through a bored or pierced hole in the centre of the billet and either connected or supported by the press rod. In this type of production, the metal flow around the mandrel is not interrupted and there are no extrusion weld planes in the section. There may be some restriction in the availability of this type of production and in the range of sections obtainable from it. As the standard of tolerances may also be wider further information and advice should be sought from the extruder for strong alloy hollow sections.

Pressure

Fig. 1.3 - Extrusion of a Hollow Section

6

area

Bridge Mandrel nose

EXTRUDABILITY

Aluminium alloys offer a wide range of performance characteristics and important amongst these is its extrudability. Linked with modern die-making facilities and traditional expertise the metal offers a virtually unlimited variety of section shapes. The feasibility of any extrusion has both technical and commercial considerations and most extruders use a number of methods to evaluate extrusion complexity. These methods are usually based upon a combination of extrusion theory and experience.

Extrusion Ratio

Extrusion ratio is the value obtained by dividing the cross-section area of the extrusion billet by the cross-section area of the extrusion to be produced. It depends very much on the size and type of press available and is a factor that can only be considered by the extruder. Optimum extrusion ratios for direct extrusion are usually between 30 and 50.

With low values of 7 or under, there is very little working of the material during extrusion. This gives a corresponding drop in mechanical properties and the possibility of coarse

grain bands. Values of 80 and above require high breakthrough pressures which are likely to cause die distortion and possible breakage.

In some cases the extrusion ratio can be improved by using a multi-hole die. In the case of indirect extrusion much higher extrusion ratios are possible because of the relatively low frictional force developed in the system.

Shape Factor

The resistance of a section to extrusion can be influenced by the shape factor. This is the relationship between the periphery and cross-section area of the section being extruded. It is usual for extruders to modify the shape factor value, in terms of extrusion weight, by dividing the periphery by the cross sectional area and multiplying by .0027. The shape factor of a proposed extrusion is usually compared with that of a similar existing extrusion to obtain a measure of extrudability. This is not a precise method, however, as any large difference in wall thickness can alter the ratio substantially. In

general, the higher the value the more difficult the extrusion and the more limited the alloy choice thereby restricting some high strength alloys. Table 1 .1 sets out some general values which can be used for reference.

7

Table 1.1 - Shape Factor Values

Section Type CCD Thickness Shape Factor mm mm

L 142 2.5 300

L 70 1.5 500 I 112 5.0 152

O 142 solid 15

O 70 solid 30

© 50 3.0 247

© 50 1.5 494

ltiiiiiil 210 3.0 190

210 2.0 285

Iii 11J 140 2.0/6.0 183

I- I 40 2.0/1.5 430

SIZE

The size of an extruded shape is determined by the diameterof the circumscribing circle (CCD) required to enclose the cross-section. The maximum CCD for any die size is

governed by the need to keep an unbroken structural ring around the die orifice.The minimum width of that ring can vary from 20 mm on an average size solid die to 60 mm or more on dies for large hollow sections. Most average sections fit into CCDs below 155 mm with a medium range of 250 mm and very large sections up to 400 mm.

The section, should, as far as possible, be distributed around the centre of the CCD. In any extrusion, metal flow is slower towards the outside edge of the die so the placing of thicker parts of the section away from the centre results in a more even metal flow.

THICKNESS

Factors that dictate thickness are influenced by section shape, alloy, die face pressure, extrusion speed and section stability during solution heat treatment and post-extrusion handling. A general guide to minimum thickness is given in Table 1.2 which is based on 6063 material.

8

E E

I- 0) 0)

C-) r 0)

0)

Table 1.2 - A Guide to Minimum Thickness

C C D in mm

a) Values for 6082 should be increased by 25% b) These thickness - GCD ratios represent average values based upon good working

practice. c) The values up to 1 .25 mm thick are for small specialised presses with very high

die face pressure levels. d) When ratios below those shown are required contact extruders.

The extrusion process will tolerate variations in section thickness but it is important to avoid abrupt change. Acceptable transition between thicknesses can be obtained by using radii or blending curves, see Fig. 1 .4. Short spans of local thinning can also be

incorporated in most sections. This is a useful method of introducing pressure hinges in section elements which will be deformed during subsequent fabrication, see Fig. 1 .5.

9

50 200 250 300

p

p I Thin hinge Radius / —

Fig. 1.4 - Thick to Thin Transitions in Fig. 1.5 - Pressure Hinge Extrusion Cross-Section

SLOTS

The formation of slots, or open box channels, in a section requires a finger or box spigot to be retained on the die. As it is not possible to reinforce these spigots, which act as local cantilevers under extrusion pressure, a practical limit must be placed on the size and type of slots available. Fig. 1.6 details the normal method of calculating slot aspect ratios although where gaps are below 3 mm these ratios are even further reduced. The maximum ratios are 3:1. Higher values are possible, particularly in 6063 alloy. Screw ports and bolt slots are detailed under these headings in section 6 Fabrication.

— Gap — Depth

___ _____ Width

Area Depth Aspect Ratio = — Aspect Ratio = — Gap2 Width

Fig. 1.6 - Slot Aspect Ratios.

10

SECTION CLASSIFICATION

There are three standard types of section - solid, semi-hollow and hollow. The first and last are self-explanatory. Semi-hollow describes those solid sections which have open box recesses with aspect ratios (depth/width) less than three. In general, the tooling and production costs increase with section categories from solid to semi-hollow and then hollow.

Solid Semi-hollow Hollow

Fig. 1.7 - Standard Section Types

CORNERS

All corners are normally broken by a radius but where absolutely necessary, sharp corners can be incorporated in a section either internally or externally but the life of the die and the speed of extrusion are both markedly reduced. Such corners also introduce problems where painted finishes are specified, introducing obvious sight lines. The

breaking of the corners, even by 0.5 mm radii is helpful in overcoming these problems but for ideal extrusion conditions, radii should be related to the overall size of the section. Table 1.8 sets out preferred values.

11

TOLERANCES

Tolerance levels for regular sections are laid down in BS 1474, however as the bulk of extrusions are non-standard they are not covered in the standard. The extrusion industry regards BS 1474 as a target level and is prepared to accept if for all general business, apart from very thin or complex sections which will be the subject of special enquiry. Closertolerances can be obtained for some sections but, again, this is a matter between customer and extruder.

In line with most production methods, tolerances are necessary to cover variations in the actual process and wearing of tools and dies.

Most tolerances are quoted as plus or minus around a datum value but, if required, unilateral tolerance can be obtained, either all positive or all negative. It is essential, however, to agree this requirement before die manufacture is commenced as the dimensional datum of the die will be altered.

All tolerances should be measured at 160G. This is particularly significant forthe length tolerances of long bars.

There is no laid-down standard for the surface smoothness or texture of mill finished extruded sections.

Table 1.3 - Tolerances on Diameter of Round Bar Intended for use on Automatic Lathes

Diameter Plus and minimum tolerances on

diameter Over Up to and including

mm 10 18 30 40 60 80

100

mm 18 30 40 60 80

100 160

+mm -mm 0.05 0.10 0.08 0.13 0.14 0.14 0.20 0.20 0.30 0.30 0.40 0.40

± 0.5% of specified diameter

12

Table 1.4 - Tolerances on Width Across Flats of Hexagonal Bar for the Manufacture of Nuts & Bolts

Width across flats Tolerance on width across flats

(all minus) Over Up to and Including

mm mm mm - 4.0 0.08 4.0 19.0 0.10

19.0 36.0 0.13 36.0 46.0 0.15 46.0 80.0 0.20

Table 1.5 - Tolerances on Diameter of Round Bar in the Controlled Stretched Condition*

Diameter Tolerances on diameter

(plus and minus) Over Up to and including

mm mm +mm -mm 10 18 0.05 0.20 18 30 0.08 0.26 30 40 0.14 0.28 40 60 0.20 0.40 60 80 0.30 0.60 80 100 0.40 0.80

100 180 0.5% of 1.0 % of specified specified diameter diameter

* The controlled stretch procedure reduces the level of any residual stresses in a bar and is ideal for machining stock. Special Tempers T6510 and T6511 refers.

13

Table 1.6 - Tolerances on Diameter or Width Across Flats of Bars for General Purposes and on Width of Solid

or Hollow Regular Sections

Diameter, width or width across flats

Tolerances (see notes 1 and 2) Over Up to and

including

mm mm ±mm - 3 0.16 3 10 0.20

10 18 0.26 18 30 0.32

30 40 0.40 40 60 0.45 60 80 0.50 80 100 0.65

100 120 0.80 120 140 0.90 140 160 1.00 160 180 1.10

180 200 1.20 200 240 1.30 240 280 1.50 280 320 1.70

NOTE 1: Tolerances in this table apply to solid materials other than: (a) round bar for use on automatic lathes (see table 1.4) (b) controlled stretched bar (see table 1.6) (c) hexagonal bars for the manufacture of nuts and bolts (see table

1.5)

NOTE 2: Tolerances in this table apply to hollow regular sections

having a wall thickness not less than 1.6mm or 3% of the overall width, whichever is the greater. In the case of non-heat-treated material or 1.6mm or 4% of the overall width, whichever is the greater, in the case of heat treated material. The tolerance should be applied to the width measured at the corners.

14

Table 1.7 - Angular Tolerances for Extruded Regular Sections

Nominal thickness of thinnest leg Allowable deviation from angle

specified (measured at the ex- tremitles of the section)

j-

Over Up to and including

mm mm - 1.6 2°

1.6 5.0 1.5° 5.0 - 1°

Table 1.8- Permitted Corner Radii

For square and rectangular sections

Minor dimension Radius on corner (max.)

Over Up to and Including

mm mm mm - 5 0.4 5 10 0.8

10 25 1.6 25 50 2.5 50 120 3.0

120 - 5.0

For regular sections (e.g. angle, channel, I- and I - sec-

tions)

Thickness of section

Radius on corner (max.)

mm Up to and including 5

Over5

mm

0.8

1.5

15

Table 1.9 - Tolerances on Wall Thickness of Extruded Round Tube (classes A, B and C) (see note 1)

Nominal wall thickness of tube

Class A Class B Class C

Toleranc on mean wall thickness

Wall thickness at any point

(Max.) (Mm.)

Tolerano on mean wall thickness


Tolerance on mean


.

(Max.) (Mm.) (Max.) .

(Mm.)

wall thickness

mm

1.0 1.5 2.0

2.5 3.0 4.0

5.0 6.0 7.0

8.0 10.0 12.0

14.0 16.0 18.0

20.0 22.0 25.0

±mm

0.15 0.16 0.17

0.18 0.20 0.23

0.26 0.28 0.31

0.34 0.40 0.46

0.53 0.58 0.63

0.68 0.74 0.81

mm

1.20 1.71 2.23

2.74 3.27 4.30

5.34 6.38 7.43

8.47 10.52 12.61

14.71 16.76 18.82

20.90 23.00 26.10

mm

0.80 1.29 1.77

2.26 2.73 3.70

4.66 5.62 6.57

7.53 9.48

11.39

13.29 15.24 17.18

19.10 21.00 23.90

±mm

-

0.18 0.20

0.22 0.27 0.31

0.37 0.43 0.51

0.56 0.65 0.77

0.88 1.00 1.13

1.22 1.35 1.49

mm

- 1.74 2.27

2.80 3.36 4.42

5.49 6.58 7.67

8.76 10.85 13.03

15.24 17.34 19.44

21.63 23.81 27.00

mm

- 1.26 1.73

2.20 2.64 3.58

4.51 5.42 6.33

7.24 9.15

10.97

12.76 14.66 16.56

18.38 20.19 23.00

±mm

- - -

- 0.65 0.70

0.75 0.82 0.89

0.94 1.03 1.15

1.30 1.40 1.50

1.60 1.73 1.88

mm

-

-

- 3.87 4.93

6.00 7.09 8.18

9.27 11.36 13.54

15.75 17.88 20.00

22.13 24.32 27.50

mm

- -

-

-

2.13 3.09

4.00 4.91 5.82

6.73 8.64

10.46

12.25 14.12 16.00

17.88 19.68 22.50

NOTE 1: BS tolerance classes A,B and C for round tube denote a descending order of tolerance standard. All classes applicable to 6063, 6063A, 6082, 6101A, 6463, Only Classes B & C are applicable to 2014A

NOTE 2: The tolerances given in this table apply to non-heat-treated tube of wall thickness not less than 1.6mm or 3% of the outside diameter, whichever is the greater and to heat treated tube of wall thickness not less than 1.6mm or 4% of the outside diameter, whichever is the greater.

NOTE 3: These tolerances on wall thickness do not apply where tolerances on both outside and inside diameter are required in which case the eccentricity tolerance on the resultant wall should be agreed between the purchaser and the supplier at the time of the enquiry and order.

NOTE 4: Mean thickness is defined as the sum of the wall thicknesses measured at the ends of any two diameters at right angles, divided by four.

NOTE 5: The tolerance on the wall thickness of intermediate nominal wall thickness should be taken as those of the next lower size.

16

—4

Tab

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.10-

Tol

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on T

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ness

of

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(plu

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Up

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up

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incl

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incl

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g 80

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up

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nd

incl

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g 12

0mm

th

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0mm

up

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and

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up

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and

incl

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g 16

0mm

th

ick

mm

-

mm

10

mm

016

± m

m

018

± m

m

020

± m

m

022

± m

m

-

+ m

m

-

+ m

m

- +

mm

-

+ m

m

-

± m

m

mm

-

+ m

m

-

mm

-

10

18

018

020

022

024

026

.

18

30

022

024

026

028

030

032

- -

- -

- -

.

30

60

0 24

0

26

0 28

0

30

0 33

0

36

0 40

-

- .

.

60

80

0 28

0

30

0 32

03

4 0

37

0 40

04

3 0

45

0 50

-

- -

-

80

120

032

034

036

039

042

045

048

052

057

065

080

- -

120

180

- 03

6 04

0 04

5 05

0 05

5 06

0 06

5 07

0 07

5 08

2 09

0 10

0

180

240

- -

050

055

060

065

070

075

080

085

090

095

105

240

320

- -

060

065

070

075

080

085

090

095

100

105

1 10

NO

TE

:-

For

sec

tions

over

160

mm

thic

k, th

e to

lera

nces

on t

hick

ness

are

tho

se sh

own

for c

ompa

rabl

e wid

ths

(see

Tab

le 1

.6)

Tab

le 1

.11

Tol

eran

ces

on O

pen

End

Cha

nnel

s an

d L

Bea

ms

Ove

rall

wid

th

Wof

ch

anne

l or i

-bea

m

Min

imum

th

ickn

ess

of w

eb or

flang

e In

lern

al or

exte

,nai

tol

eran

ce o

n op

en e

nd d

imen

sion

for v

ario

us d

eplh

s of

open

ing

D(p

ius

and

min

us)

For

0

For

0

For

0

For

D

For

D

For

0

For

0

For

0

For

0

For

0

For

0

up t

o an

d ov

er

over

ov

er

over

ov

er

over

ov

er

over

ov

er

over

in

clud

ing

10m

m

18m

m

30m

m

40m

m

60m

m

80m

m

100m

m

120m

m

140m

m

160m

m

10m

m

up to

and

up

to

and

up to

and

up

to a

nd u

p to

and

up

to

and

up to

and

up

to a

nd u

p to

and

up

to a

nd

deep

in

clud

ing

incl

udin

g in

clud

ing

incl

udin

g in

clud

ing

incl

udin

g In

clud

ing

incl

udin

g in

clud

ing

incl

udin

g 18

mm

30

mm

40

mm

60

mm

80

mm

10

0mm

12

0mm

14

0mm

16

0mm

18

0mm

de

ep

deep

de

ep

deep

de

ep

deep

de

ep

deep

de

ep

deep

Ove

r U

p to

and

in

clud

ing

Ove

r U

p to

and

in

clud

ing

mm

-

mm

10

mm

- 1.5

3.0

mm

1.5

3.0

-

* mm

026

0.23

0

22

+ m

m

032

0.28

0.

26

÷ m

m

0.41

0.

34

0.30

+ m

m

- • -

* m

m

- • -

+ m

m

- • -

+ m

m

- - -

* m

m

- - -

+ m

m

- - -

+ m

m

- - -

+ m

m

- - -

10

18

- 1.5

3.0

1.5

3 0

-

0.31

0

29

0.28

038

0.34

0.

32

0.47

0

40

0.36

0.56

0.

46

0.41

070

0.55

0.

47

- - -

- - -

- - - - - -'

- - -

- - -

18

30

- 3.0

6.0

3.0

6.0

-

037

0.37

0.

35

047

044

0.41

0.57

05

3 04

8

0.68

0.

62

055

0.84

07

6 0.

64

1.05

09

3 0

78

126

1.11

09

1

- - -

- - -

- - -

- - -

30

40

- 3.0

6 0

3.0

6.0

-

0.45

0.

45

0 43

0.55

0.

52

0.49

0.65

0.

61

0 56

0 76

0.

70

0 63

0 92

0.

84

0.72

1.13

1.

01

0 86

1 34

1.

19

0.99

1.55

1.

36

1.12

1 76

1,

54

1.26

- - -

- - -

40

60

- 3 0

6.0

3.0

6 0

-

- - -

060

0.57

0.

54

0.70

0

66

061

081

0.75

0.

68

097

0 89

0,

77

1.18

1

06

0.91

1.39

1

24

1.04

1.60

1.

41

117

181

1 59

1.

30

2.02

1.

76

1 43

- - -

60

80

- 3.0

6.0

3.0

6.0

-

- - -

0.65

0.

62

0.59

0 75

0.

71

0.66

0.86

0.

80

073

1.02

0.

94

0.82

1 23

1.

11

0.96

1 44

1.

29

1.09

165

1.46

1.

22

1.86

16

4 1.

35

2.07

1.

81

148

2.28

1.

99

161

80

100

- 6 6 -

- - - -

0.90

08

6 1.

01

095

1.17

1.

09

1.38

1.

26

1 59

1.

44

1.80

1.

61

2.01

1

79

2.22

1.

96

2.43

2.

14

100

120

- 6 6 -

- - - -

1.05

1.

01

1.16

1.

10

1 32

1.

24

1.53

1.

41

1 74

1

59

1.95

1.

76

2.16

1.

94

2.37

2.

11

2.58

2.

29

120

140

- 6 6 -

- - - -

1.15

1.

11

126

120

1,42

13

4 1.

63

1,51

1.

84

1.69

20

6 1.

86

2.26

2.

04

247

221

265

2.39

140

160

- 6 6 -

- - - -

1.25

1.

21

1 36

1.

30

1.52

1.

44

1 73

1.

61

1.94

1.

79

2.15

1.

95

2.36

2.

14

2.57

2.

31

2.78

2.

49

-L

(0

Tab

le 1

.11

(con

tinue

d)

Dep

th o

f

Ope

n en

d dl

men

s!on

Flo

nqe

Web

Ope

n

0 D

epth

of

opee

ng

Ove

rall w

idth

Wof

M

inim

um th

ickn

ess

inte

rnal

or

exte

rnal

tol

eran

ce o

n op

en e

nd d

imen

sion

fo

r va

rious

dept

hs o

f ope

ning

D

(plu

s an

d m

inus

) ch

anne

l or I

-bea

m

of w

eb o

r fla

nge

or D

F

or D

F

or D

F

or D

F

or 0

F

or 0

F

or D

F

or D

F

or 0

F

or 0

F

or 0

O

ver

Up

to a

nd

Ove

r U

p to

and

up

to a

nd

over

ov

er

over

ov

er

over

ov

er

over

ov

er

over

ov

er

Incl

udin

g in

clud

ing

Incl

udIn

g 10

mm

18

mm

30

mm

40

mm

60

mm

80

mm

10

0mm

12

0mm

14

0mm

16

0mm

10

mm

up

to

and

up t

o an

d up

to a

nd u

p to

and

up

to

and

up t

o an

d up

to

and

up t

o an

d up

to a

nd

up to

and

de

ep

Incl

udin

g In

clud

ing

incl

udin

g in

clud

ing

incl

udin

g in

clud

ing

incl

udin

g in

clud

ing

incl

udin

g in

clud

ing

18m

m

30m

m

40m

m

60m

m

80m

m

100m

m

120m

m

140m

m

160m

m

180m

m

deep

de

ep

deep

de

ep

deep

de

ep

deep

de

ep

deep

de

ep

mm

160

mm

180

mm

- 6

mm

6 -

mm

- -

+ m

m

- -

+ m

m

1.35

1

31

+ m

m

146

1.40

+ m

m

162

1.54

+ m

m

183

1 71

+ m

m

204

1.89

+ m

m

225

2.06

+ m

m

246

2.24

+ m

m

2.67

24

1

+ m

m

288

259

180

200

- 6 6 -

- - - -

1.45

14

1 1

56

150

1.72

1.

64

1.93

18

1 21

4 19

9 2.

35

2.16

25

6 2.

34

277

251

298

269

200

240

- 6 6 -

- - - -

1 55

15

1 1

66

160

1 82

1.

74

2 03

19

1 2,

24

209

2 45

2.

26

2 66

2.

44

2 87

26

1 3

08

279

240

280

6 -

- -

1 71

18

0 19

4 21

1 22

9 24

6 26

4 28

1 29

9

280

320

6 -

- -

1.91

2.

00

2 14

23

2 2.

40

2.66

28

4 3.

01

3.19

Table 1.12 - Tolerances on the Outside Diameter of All Extruded Round Tube and on the Inside Diameter of Class A and class B

Extruded Round Tube (see note 1)

Outside diameter, or inside diameter

Tolerance on the actual diameter (see notes 5 and 6)

Tolerance on the mean diameter (see notes 5 and 6)

Over Up to and Including

mm 12 18 30

40 50 60 80

mm 18

30 40

50 60 80

300

±mm 0.25 0.30 0.36

0.45 0.54 0.60

1%of diameter

±mm 0.19 0.23 0.27

0.34 0.40 0.45

314%of diameter

NOTE 1. For details concerning the applicability of tolerance class (A or B) to alloy, see 1.9.

NOTE 2. The tolerances are applicable to non-heat-treated tubing of wall thickness not Iessthan 1.6mm or 3% ofthe outside diameter, whichever is the greater, and to heat-treated tubing of wall thickness not less than 1.6 mm or 4 % of the outside diameter, whichever Is the greater.

NOTE 3. In the case of tubing in straight lengths, the above tolerance limits are Inclusive of ovality.

NOTE 4. Where a tolerance on wall thickness is required, the tolerances on diameter are to be applied either to the outside diameter or to the Inside diameter, but not to both.

NOTE 5. Tolerances on the actual diameter Indicate the amount by which the diameter (inside or outside, as appropriate measured in any direction may depart from the specified diameter. Tolerances on the mean diameter (inside or outside, as appropriate) Indicate the amount by which the mean of two diameters measured In two directions at right angles in the same plane may depart from the specified diameter.

NOTE 6. The given tolerances on the actual diameter do not apply to annealed tube, coiled tube, or tube having a wall thickness less than 2.5 % of outside diameter. The tolerances of these products and of controlled stretched tube are subject to agreement between purchaser and supplier.

20

Tab

le 1

.13-

Tol

eran

ces

on T

hick

ness

of

Hol

low

Sec

tions

(cla

sses

A a

nd B

(

Wid

th o

r w

idlh

ac

ross

fla

ts

Tol

eran

ces

on s

peci

fied

thic

knes

s

Cla

ss A

C

lass

B

Ove

r U

p to

and

In

clud

ing

Up

to a

nd

incl

udin

g 1.

6 m

m

thic

k

Ove

r 1.

6mm

up

to

and

incl

udin

g 3.

0mm

th

ick

Ove

r 3.

0mm

up

to a

nd

Incl

udin

g 6.

0mm

th

ick

Ove

r 6.

0mm

up

to a

nd

incl

udin

g 10

mm

th

ick

Ove

r 10

mm

up

to

and

incl

udin

g 18

mm

th

ick

Ove

r 18

mm

up

to

and

Incl

udin

g 30

mm

th

ick

Up

to a

nd

incl

udin

g 1.

6mm

th

ick

Ove

r 1.

6mm

up

to a

nd

incl

udin

g 3.

0mm

th

ick

Ove

r 3.

0mm

up

to

and

incl

udin

g 6.

0mm

th

ick

Ove

r 6m

m

up t

o an

d

incl

udin

g 10

mm

th

ick

Ove

r 10

mm

up t

o an

d

incl

udin

g 18

mm

th

ick

Ove

r 18

mm

up

to

and

incl

udin

g 30

mm

th

ick

mm

m

m

10

10

18

18

30

+ m

m

- 0.20

02

6

* m

m

. 0.22

0.

28

* m

m

. - 032

+ m

m

. . -

* m

m

- - .

mm

- - -

* m

m

- 022

0.28

+ m

m

- 0.28

03

6

* m

m

- - 0.54

mm

- . -

mm

- .

+

nm

-

30

60

60

80

80

120

032

0,36

.

036

041

0.48

0.41

04

8 0

58

048

058

0.68

. 062

0 82

- - 1 00

036

045

-

0.45

05

5 0.

65

065

075

0 80

090

095

1 00

1 40

14

5 1.

50

- - 2 00

120

180

180

240

240

320

. - -

0.65

- -

075

095

-

0.85

1

05

1 25

0.95

1

20

1 45

110

1 40

1

80

. - - 07

5 - -

0.85

1

00

- 11

0 1

20

1 40

1 60

1

80

2 00

2.20

24

0 2

60

NO

TE

1.

For

det

ails

conc

erni

ng th

e ap

plic

abili

ty of

tole

ranc

e cl

ass

(A to

B) t

o al

loy,

see

Not

e 1

of T

able

1,9

NO

TE

2.

The

tole

ranc

es ap

ply t

o no

n-he

at-t

reat

ed se

ctio

ns o

f wal

l th

ickn

ess

not

less

tha

n 1.

6 m

m o

r 3%

of

the

over

al w

idth

, whi

chev

er

is th

e gr

eate

r, a

nd

to h

eat-

trea

ted

sect

ions

of w

all

thic

knes

s no

t le

ss t

han

1.6m

m o

r 4%

of

the

over

all w

idth

, whi

chev

er is

the

grea

ter.

N) -'

Table 1.14 - Tolerances on Straightness for Extruded Bar, Regular Sections and Extruded Round Tubes (see below)

For bars, tubes or sections within a

circumscribing circle

Temper Nominal length of bar, tube or section L

Maximum derivation S from straightness of length L (metres) (see below)

Maximum localized kink in any 300 mm

portion

mm Up to and including 100

All tempers m

over 0.4 mm 1.5 L

mm 0.6

Over 100 F

All other tempers

over 0.4

over 0.4

2.0 L

2.5 L

0.8

1.0

NOTE 1. The straightness is measured by determining the maximum deviation from straightness S over length 1, when the bar, section or tube is supported on a flat table such that the deviation is minimized by Its own mass.

NOTE 2. Kink Is measured using a straight edge 300 mm in length (see below).

NOTE 3. Tolerances on straightness for annealed and controlled stretched materials should be subject to agreement between the purchaser and the supplier at the time of the enquiry and order.

Localized kink 300mm straightedge Bar, tube or section ot length L

V 7/ / / / ///V/ ////4// // /// // / //

Maximum Section through - deviation S

tiatness measuring table

Length L

22

Table 1.15 - Tolerances on Length for All Materials Supplied in Fixed Cut Lengths

Diameter, width across flats or overall width

Tolerances on length for given length (plus and minus) (see notes 1 and 2)

Over Up to and including

Over 300 mm up to and including 1000 mm long



Over 5000 mm up to and including 7000 mm

long

Over 7000 mm up to and including 10000 mm

long

Over 10000 mm long

mm

- 60

100 140 180

mm

60 100 140 180 240

jmm

2.0 2.0 3.0 3.5 4.5

jmm

2.5 2.5 3.5 4.0 5.0

jmm

2.5 3.5 4.0 5.0 6.5

jmm

3.5 4.0 5.0 6.5 8.0

jmm

4.0 5.5 6.5 8.0 9.5

jmm

6.5 7.5 8.0 9.5

11.0

NOTE 1. Tolerances on length are measured at a temperature of 16 5 C. They provide for out-of-squareness of cut to the extent of 10.

NOTE 2. Total tolerances (i.e. the sum of the plus and minus limits) may be applied unilaterally by agreement between the supplier and the purchaser.

Table 1.16 - Tolerances on Concavity and Convexity for Extruded Solid

and Hollow Sections

Width of section W Maximum allowable deviation D (see figure)

mm mm

Up to and including 25 0.125

Over25 0.l2Sper2Smm increment in width (e.g. for 150 mm width maximum deviation D permitted is 0.75 mm)

23

Coo cool ty

Under 20

20 up to and including 40

Over 40 up to and including 80

Over 80:

Lengths upto and including 8000 mm

Lengths over 8000 mm

degrees

3

0.5

degrees

7

5

3

Table 1.17- Tolerances on Twist for Extruded Solid and Hollow Sections

Twist T

24


SECTION 2- MATERIAL SPECIFICATIONS

CONTENTS

Title Page No.

ALLOYS 27

TEMPER 29 Solution Heat Treatment 30 Precipitation Heat Treatment 30

25

List of Figures


2.1 Temper Cycles 29

2.2 Solubility Diagram 31

List of Tables

No. Title Page No.

2.1 Chemical Composition 27

2.2 Alloy Characteristics and Uses 28

26

ALLOYS

High purity aluminium, 99.00% and above, has excellent durability together with high thermal and electrical conductivity. It is easily worked and afthough it can be strengthend by cold working it remains a low stength material.

For more general use, alloying elements are introduced, producing materials that retain the general characteristics of pure aluminium but have greater structure strength (refer to Table 2.2). In the extrusion industry, the alloys most widely used

throughout the world are in the International Standards 6000 series, to which the British Standards alloys also conform. The main alloying constituents in this series are silicon and magnesium (refer to Table 2.1).

Table 2.1 - Chemical Composition

COMPOSITION (%) ALLOY BS 1474 Others (1987) SI Fe Cu Mn Mg Cr NI Zn TI Each Total Al

0.20- 0.45- 6063 0.60 0.35 0.10 0.10 0.90 0.10 - 0.10 0.10 0.05 0.15 REM

0.30- 0.15- 0.60- 6063A 0.60 0.35 0.10 0.15 0.90 0.05 - 0.15 0.10 0.05 0.15 REM

0.70- 0.40- 0.60- 6082 1.30 0.50 0.10 1.00 1.20 0.25 - 0.20 0.10 0.05 0.15 REM

* 0.30- 0.40- 6101A 0.70 0.40 0.05 - 0.90 - - - - 0.03 0.10 REM

0.20- 0.45- 6463 0.60 0.15 0.20 0.05 0.90 - - 0.05 - 0.05 0.15 REM

0.50- 3.90- 0.40- 0.20- 0.15-

2014A 0.90 0.50 5.00 1.20 0.80 0.10 0.40 0.25 0.20 0.05 0.15 REM

* 6101A comforms to BS 2898 ** T + Zr

27

Table 2.2 - Alloy CharacteristIcs and Uses

BS CHARACTERISTICS TYPICAL USES

6063 Suitable for intricate extruded sections of mid-strength. Forms well in T4 condition. High corrosion resistance. Good surface finish.

6063A A stronger version of 6063 but retaining most of that alloy's good surface finish and formability.

6082 The recommended alloy for structural purposes with good strength and general corrosion resistance.

6101A The best combination of electrical and mechanical conductor properties with conductivity of 55% of the International Annealed Copper Standard.

6463 Based on high purity (99.8%) aluminium, this alloy was developed to respond well to chemical or electro-chemical brightening or anodizing. It has excellent formability.

2014A A high strength alloy with moderate corrosion resistance.

28

The most widely used alloy. Architectural members i.e. glazing bars and window frames; windscreen sections, road transport.

Road and rail transport, general engineering, ladders and light structures.

Road and rail transport, scaffolding, bridges, cranes and heavy structures.

Busbar, electrical conductors and fittings

Motor car trim and other applications requiring a bright finish.

Structures, aerospace, general engineering.

TEMPER

The properties of alloys in the 6000 and 2000 range can be improved by heat treatments after extrusion.

These alloys, although available in the F, "as manufactured", condition, are more

usually produced in one of the following three tempers:-

T4 - solution heat treated

T5 - precipitation treated (artificially aged)

T6 - solution heat treated and precipitation treated (fully heat treated)

T5 PRECIPITATION

HEAT ___________ SOLUTION TREATMENT

EXTRUSION_F (QUENCHING)

(AGEING)

:

F

Fig. 2.1 - Temper Cycles

The current procedure for producing the T4 temper is usually 'on-line". An extrusion, emerging from the die at about 500°C, is rapidly cooled by air, water spray or water immersion, depending upon the section shape and extrusion speed. The temper, although stronger than in the F condition, is still of relatively low strength and, with its high elongation value, it is an excellent choice where severe forming is required. Some natural ageing or hardening will occur which will, in some alloys, curtail the time available for forming.

For thin sections a stronger temper, T5, is available. T5 is given greater strength by carrying out precipitation treatment without any solution heat treatment. This is

provided by heating the material up to about 180°C and soaking for several hours in an oven.

29

The final and strongest temper available (without the application of cold work) is T6 which combines both the solution heat treatment and the precipitation treatment.

The relationship between mechanical properties and heat treatment of a range of aluminium alloys was first discovered by Wilm in 1906. Overthe years, the process has been developed with improvements and innovations being introduced which have

helped to make the "heat treated" alloys the most widely used extrusion materials in the world.

in recent years, much greater use has been made of reheat treatment following low temper or heat induced fabrication operations such as bending and welding. This is

a property of aluminium that is well worth considering at the design and material selection stage of fabricated components.

It is not the purpose of this manual to deal with detailed metallurgical aspects of aluminium and its alloys, but the following simplified explanation of heat treatment may be of background interest:-

The thermal treatment consists of two phases:

a) solution heat treatment b) precipitation heat treatment

Solution Heat Treatment

The chemical constituents of aluminium alloys are to a greater or lesser extent soluble in aluminium. The degree of absorption varies with the amount and type of constituent and temperature. The higher the temperature, the greater the amount dissolved. Fig. 2.2 shows a typical solubility diagram where, at temperatures above point A , (the Solvus temperature) the atoms are in solid solution and designated by the prefix "solute". These atom phases of constituents are thus dissolved in solid solution and a rapid temperature drop, through quenching, will prevent the solute atoms from diffusing out of solution. This condition, however, is not totally stable and a natural ageing will take place, varying from several days to several weeks depending upon the alloy. During the ageing process a fine dispersion of clusters of solute atoms will occur. The final stable condition is defined as T4 temper.

Precipitation Heat Treatment

The precipitation heat treatment process, also known as artificial ageing, speeds up and greatly increases the rate of precipitation and fine dispersion of the constituent atoms, which are distributed in clusters over the whole matrix. The alloy will now tend to resist material dislocation, resulting in a marked improvement in both strength and hardness, usually to a level well above that obtained by natural ageing.

30

0 U)

CU

U) 0 E U)

I—

Liquid

% Constituent

Figure 2.2 - Solubility Diagram

31

Liquid - solid

5

Solid



SECTION 3- MECHANICAL PROPERTIES

CONTENTS

Title Page No.

INTRODUCTION 35

STRESS 36 Axial Loading 38

STIFFNESS 41

HARDNESS 43

FATIGUE 43

33

List of Figures


3.1 Yield Point 36

3.2 Typical Stress Strain Curves 37

3.3 Permissible Compressive Stresses in Struts 39

3.4 Relationship Between Hardness Number and Tensile, Yield Strengths 42

3.5 Fatigue Curves For Some Aluminium Alloys (Rotating Cantilever Tests) 44

List of Tables

No. Title Page No.

3.1 Properties to BS 1474 35 (1987)

3.2 Permissible Stresses 38

3.3 Effective Lengths of Struts 40

3.4 Moduli of Elasticity 41

34

INTRODUCTION

A wide range of mechanical properties is available from aluminium and its alloys with the level of performance varying with the degree of alloying and temper. The property range for the more generally available commercial alloys is given in Table 3.1.

Table 3.1 - Properties to BS 1474(1987)

ALLOY TEMPER MAX THICKNESS

mm 0.2% Ps N/mm2

ULT. STRESS N/mm2

%ELONGATION b)

5.65y' 50 mm

6063

Fe) T4 T5 16

200 150 25

150

- 70 110 160

100 130 150 195

13 16 8 8

12 14 7 7

6063A T4 15 T6

25 25 25

90 160 190

150

200 230

14 8 8

12 7

7

6082

Fe) T4 15 T6

200 150

6

20a)

- 120 230 255

110 190 270 295

13 16 -

8

12 14

8 7

6lOlAd) T6 - 170 200 10 8

6463 T4 T6

50 50

75

160

125 185

16 10

- -

2014A 14 T6

20a) 20a)

230 370

370 435

11

7 10 6

a) Thicker sections are possible and give higher mechanical properties. For details contact extruder.

b) The elongation is obtained from a tensile test sample on which a gauge length is marked prior to testing. The gauge length is specified, being either 50 mm

long or 5.65 / cross-sectional area. (So) C) The properties of aluminium vary with temperature outside an approximate

range of -50°C to +80°C. They will increase at low temperatures and decrease at high temperatures. The values vary with the alloy, see Table 8.2.

d) Alloy 6101A conforms to BS 2898. e) Values given for F condition are not specified properties in British Standards

and are given for information only.

35

STRESS

Aluminium does not exhibit a yield point. Stress/strain behaviour is similar to that of a numberof other metals, including some alloy steels. It is necessary, therefore, to advise a recognisable point of departure from elastic to plastic behaviour. In the method chosen, the stress level registered at 0.2%. Permanent strain is regarded as the yield point. The yield point can be obtained from the stress/strain curve by drawing the offset of O.2% strain parallel to the elastic line for the alloy under consideration. The 0.2% proof stress can be read at the point of intersection of the two lines, see Fig. 3.1. Alloy curves will have a different point of departure for each temper condition.

E E

z 0, CO

U)

Fig. 3.1 - Yield Point

36

0.70

200

/ /

0.2 Ordinate

NB. for reasons of clarity the alloy curve is exaggerated

/ / /

20 / 0.50 0.60

% Strain

500- 2014A T6

Mild Steel

400 —— / / /

E 300- //'7 6082 T6

z a, / ci) /

'—'—I

(I)

200-

100-

I I I

0 5 10 15 20

% Strain

Fig. 3.2 - Typical Stress Strain Curves

37

Table 3.2 - Permissible Stresses

ALLOY TEMPER AXIAL e) N/mm2 Pt Pc

BENDING N/mm2 Pbt Pbc

SHEAR N/mm2

BEARING N/mm2

s

6063

6063

6082

2014A

2014A

15

T6

16

T4

16

62

87

139

135 124

154d) 20

69

96

154

153 142

154d) 224

37

52

83

81

108

117

139

222

239

278

106

81

61

71

49

Pt AXIAL TENSION Pc AXIAL COMPRESSION Pbt BENDING TENSION Pbc BENDING COMPRESSION s SLENDERNESS RATIO AT EULER BLEND POINT SEE FIG. 3.3

a) Permissible stress levels are laid down in BS CP1 18 The Structural Use of Aluminium".

b) 6063 values are applicable to 6101A and 6463.

C) 6063A is a new alloy, not yet allocated a value but from experience it should be slightly in excess of 6063 values (8%).

d) Arbitrarily reduced values to allow for inferior crack-propagation resistance. e) Applies only when buckling is not the criterion.

AxIal Loading

For axial loading, in columns and struts, the permissible compressive stress is obtained by inserting the appropriate slenderness ratio into the alloy/temper curves given in

Fig. 3.3, and using the effective length factor from Table 3.3.

38

CM

E E z 'a CM a)

(1)

a) > U) (a a) 0. E 0 0 a) .0 0) 0) E a)

Fig. 3.3 - Permissible Compressive Stresses in Struts

= K!.

whore = slenderness ratio K = end fixity factor (effective length) L = spaninmm r = radius of gyration of section in mm

also r =

= inertia A = cross sectional area

39

100 1 A Slenderness Ratio

Table 3.3 - Effective Lengths of Struts

End Condition Effective Length of Strut

Effectively held in position and restrained in direction at both ends 0.7 L

Effectively held in position at both ends and restrained in direction at one end 0.85 L

Effectively held in position at both ends, but not restrained in direction L

Effectively held in position and restrained in direction at one end and partially restrained in direction but not held in position at the other end

1.5 L

Effectively held in position and restrained in direction at one end, but not held in

position or restrained at other end 2.0 L

NOTE. L is the length of strut between points of lateral support.

The extensive range of shapes and, over the last few years, the ability of the industry to produce thinner extrusions has encouraged the use of slender sections. Because of low aspect ratios (width/depth) and high element thickness ratios (width/thickness) of the thinner extrusions they require examination for possible modes of elastic instability. The modes of failure listed below are particularly relevanttothin-walled open sections of asymmetrical shape in aluminium alloys.

a) Torsional warping b) Lateral instability C) Local buckling

All the factors are influenced by the shape and dimensions of the section and, whilst (a) and (b) are also relevant to span, (C) is not.

Although safe values are often quoted in simple terms for aspect and element thickness ratios, they are not entirely reliable and should not be used. If there is any doubt about the robustness of a section in the form of failures list above, it should be checked, using appendices F, G, H and Kin BS CP 118- The Structural Use of Aluminium". The design approach uses equivalent slenderness ratios in conjunction with alloy compression curves. The strut curves in Fig. 3.3 can be used for torsional warping but will give pessimistic values for lateral instability and local buckling, where the equivalent slenderness ratio falls on the straight line parts of the graphs: See BS CP1 18 Fig. 2 for modified compression curves suitable for solving lateral instability and local buckling.

40

STIFFNESS

The stress/strain relationship is given by Hooke's Law which states that intensity of stress is proportional to strain. This is applicable to aluminium alloys to a level just below the 0.2% proof stress, the slope of the line being obtained from:

Table 3.4 - Modull of Elasticity

E = Stress where E is the modulus of elasticity Strain

ALLOY MODULUS OF ELASTICITY E N/mm2

6063 65,500 6063A 65,500 6082 68,500 6101A 65,500 6463 65,500 2014A 72,000

These values are approximately one third of that of mild steel, 210,000 N/mm2. Aluminium under elastic bending will therefore give deflections three times greater than those obtained from mild steel under similar loading conditions. This is not true for self weight loading where the light weight of aluminium counteracts the effect of the lower elastic modulus of aluminium. The advantage to be obtained from a low modulus are greater impact absorption with shock loads and lower imposed stress levels from movement in static structures caused by temperature variation or support settlement. The modulus of elasticity will vary with temperature, see Table 8.2.

In applications where deflection is the controlling design factor, the performance of aluminium can be dramatically improved by utilising the advantages of the extrusion

process to position materials strategically around the section. The geometric properties can also be increased by small additions to section depth.

This modification applies to all materials but can be more readily incorporated into extruded aluminium sections. Examples are given in Section 11, Design.

The relationship between lateral and longitudinal strain, within the elastic limit, is given by Poisson's Ratio which, for aluminium alloys, is usually 0.34.

41

30 x E E 25 z -c 0) c 20 )2)

(0 D .; 15-

(0 C 10 a I-

HARDNESS TESTER SETTINGS Brinell

lOmm.Steel ball penetrator - 500kg.load Vickers

Diamond penetrator - various loadings Rockwell 'F'

1.6mm Steel ball penetrator - 6Okg.load Rockwell 'E'

3.2mm, Steel ball penetrator - lOOkg.load

Rockwell 'B' 1.6mm Steel ball penetrator - lOOkg.load

Rockwell 'K' 3.2mm Steel ball penetrator - l5Okg.load

Webster Model 'B'

Note: As this table shows, a hardness value covers a range of stress levels and must not therefore be used to give precise measurements of strength.

Fig. 3.4 - Relationship Between Hardness Number and Tensile, Yield Strengths

42

35

Tensile

Relationship between hardness number and tensile strength for magnesium - silicide alloy extrusions in the artificially aged condition

Yield

(1/6063 T5 & T6 6082 T6 F

j"1 i'• •1

Brinell 6063A

T6 Vickers 45 055 6065 707580 85 9095100105110

46 51 56 61 66 71 76 82 87 92 98103 109115 Rockwell 'F' Rockwell 'E' 54 61 67 71 76 79 82 85 87 89 91 -

Rockwell 'B' 47 55 62 68 72 77 80 83 86 88 90 92 94 96 I I I

Rockwell 'K' - - - - 12 23 32 39 45 50 55 60 63 66

— 15253441485358826670737678 Webster 5 7 9 10 11 12 13131414—151515161616—1717

Hardness number

HARDNESS

The surfaces hardness of aluminium alloys can be assessed by most of the general methods of measurement, Brinell, Vickers and Webster etc. The accuracy of the results can vary, particularly with those methods that use manual pressure to obtain the surface indentation.

The trend to relate mechanical properties to hardness values is not to be recommended as there is no accurate constant relationship. The curves shown in Fig. 3.4 are for general guidance only and indicate that there are given ranges of stress levels for each hardness value.

FATIGUE

Aluminium is similar in its fatigue behaviour to other non-ferrous metals in that the stress/cycle curves never totally flatten out. An arbitrary maximum endurance level is therefore imposed,. usually 50 million cycles. Curves are drawn up for alloy and temper groups against semi-range of stress levels (see Fig. 3.5). Fatigue curves are usually based upon actual test results from Wohler type beam machines which subject the specimens to sinusoidal reversed bending. The results are generally plotted for high cycle applications, above 1 O cycles, and any high strain/low cycle applications should be discussed with the extruder.

The surface finish and geometric aspects of components, particularly joints, can influence performance. Shot blasting of the surface can improve fatigue resistance, whilst notches can reduce it. With welded connections, it is usual to obtain better results from butt joints than those which are lapped and continuous welds give a superior performance to that of intermittent welds. Some data based upon nine different classifications of structural components is given in BS CP1 18.

43

300-

270-

240-

210- E E

z 180-

a

a

0 a a, 150- C C,,

E

120-

90-

60 -

i0 106 i07 108

Endurance (cycles)

Similar results are obtained for alloy 6082T6

Fig. 3.5- Fatigue Curves for Some Aluminium Alloys (Rotating Cantilever Tests)

44


SECTION 4- DURABILITY

CONTENTS

Title Page No.

INTRODUCTION 47

ATMOSPHERIC 47

CHEMICAL 49

MATERIALS 49 Bi-MetaIlic 49 Wood 53 Insulating Materials 53 Concrete 53

45

List of Figures


4.1 6082 T6 Alloy (Mill Finish) Exposure Graph (1) 48

4.2 6082 T6 Alloy (Mill Finish) Exposure Graph (2) 48

4.3 Principle of Galvanic Reaction 49

4.4 Typical Bi-metallic Connections Between Aluminium and Steel 52

List of Tables

4.1 Electro-Chemical Series 50

4.2 Guide to Bi-metallic Corrosion Effects at Junction of Aluminium and Other Metals 51

46

INTRODUCTION

Aluminium and its alloys have, in general, excellent durability and corrosion resistance. Like most materials, however, their behaviour can be influenced by the way in which

they are used. In this section the manner in which aluminium responds to various environments and design situations is reviewed with advice on use in specific applications.

ATMOSPHERIC

Aluminium's natural affinity with oxygen results in the formation of an oxide layer when exposed to air. The resulting film is generally 50 Ang thick, extremely hard, chemically stable, corrosion resistant and adheres strongly to the parent metal surface, producing an integrated material. Once formed, it prevents further oxidisation and, if

damaged in any way, will reform, oxygen availability permitting. The only practical reason for removing this film is to facilitate anodizing or welding. In the first instance, a thicker, more controlled deposition of the oxide layer can be carried out and in the latter case, the oxide film would be a deterrent to good metal fusion.

The behaviour under atmospheric exposure can therefore be described as self- stifling. If the surface layer is pitted by any of the air-borne pollutants usually found in industrial or marine atmospheres, such as sulphuric acid and sodium chloride, the resulting chemical reaction produces a larger volume of powdered corrosion product than the volume of the original pit, thereby sealing off the surface of the aluminium and inhibiting any further corrosive reaction. In general, the ratio of corrosion product to pit volume is 240:1.

With time, existing pits, which are usually of a shallow hemispherical shape, are sealed and the rate of formation of new pits is reduced so that eventually all reaction can be assumed to have ceased. This process can be described as weathering, for the depth of pitting is extremely small. The level of pollution of course will determine the general appearance, which will appear to be a soft blueish-grey colour in rural areas and dark grey to black in industrial areas. Regular maintenance and washing down should prevent the permanent discolouration from industrial pollutants. Anodized surfaces, however, will retain their original appearance for a much longer period, providing that regular maintenance is carried out. See Section 10.

For the purposes of assessment, the various types of environmental conditions are divided into 3 categories:

a) RURAL b) MARINE

c) INDUSTRIAL

47

E E

1) 0. D

3-

Fig. 4.2- 6082 T6 Alloy (Mill Finish) Exposure Graph (2)

48

6

Exposure time - years

Marine Industrial

Rural

Fig. 4.1 - 6082 T6 Alloy (Mill Finish) Exposure Graph (1)

The exposure trials on which Fig. 4.1 is based also provided samples for testing the mechanical properties of the materials. As can be seen in Fig. 4.2 there is very little drop in these properties, even after prolonged exposure of 12 years. In both figures, the graph line is virtually horizontal and therefore durability and mechanical properties can be assumed to have reached stable conditions.

i:: stri:l 0 6 8 10 12

Exposure time - years

CHEMICAL

The behaviour of aluminium alloys in contact with a wide range of chemicals is well- documented arid requests for specific information can usually be dealt with by your material supplier. In general, corrosion of aluminium only occurs to any great degree where the ph is be'ow 3 or above 9, i.e. under strong acidic or alkaline conditions. t is

therefore necessary to know the concentration of the chemical underconsideration and

also the temperature at which it will operate, as in some cases the temperature can be

the major consideration by altering the normal behaviour pattern.

MATERIALS

When aluminium will be in contact with other materials under wet or moist conditions, it is necessary to check whether some form of protection is required.

Bi-Metallic

When dissimilar metals are coupled together in the presence of moisture, there is a likelihood of a galvanic reaction in which one metal will corrode see, (Fig. 4.3). In this

situation an electrolytic couple is formed in which a current flows from the less noble

metal, acting as an anode, to the more noble metal, acting as a cathode, with corrosion concentrated on the less noble metal. This behaviour is usually consistent with the relative placings in the electro chemical series, see Table 4.1.

Corrosion Electrons

— ri Positive + Base or less noble metal

1 ions 2

Electrolyte Noble metal Anode Cathode

Corrosion cell

Fig. 4.3 - Principle of Galvanic Reaction

49

The severity of the galvanic action also depends on the degree of separation, electrical resistance of the metal path, conductivity of the solution and the area ratio between the two dis-similar metals. In practice, however, reaction between the metals can be avoided by insulating them from each other with an electrically inert non-abosrbent barrier. An excellent example of this kind of connection is between the aluminium super-structure and steel decking on ships. Reference can be made to B.S. publication PD 6484 - 1984.

Table 4.1 - Electro-Chemical Series

BASE Magnesium Zinc Aluminium Cadmium Mild Steel Cast Iron Lead Tin Nickel Brasses Copper Bronze Monel Silver solders (70% Ag. 30% Cu) Nickel Stainless Steel (Type 304) PASSIVE Silver Titanium Graphite Gold

NOBLE Platinum

50

Table 4.2 - Guide to Bi-metallic Corrosion Effects at Junction of Aluminium and Other Metals

Metals Coupled With Aluminium Of Aluminium Alloy

Bi-metallic Effect

Gold.platinum, rhodium,silver.

Attack accelerated in most environments

These metals, and especially those at the top of the list are generally cathodic to aluminium and its alloys, which therefore suffer preferential attack when corrosion occurs.

Copper, copper afloys. irwnersion. silver solder

Attack accelerated in most atmospheres to aluminium and its and conditions of total

Solder coatings on steel or copper

Attack accelerated at the interface in severe or moderate atmospheres and under conditions of total immersion,

Nickel, nickel alloys

—_____________

Attack accelerated in marine and industrial

atmospheres and conditions of total irmtersion but not in mild environments, —---

Steel, cast iron Attack accelerated in marine and industrial atmospheres and conditions of total immersion but not in mild environments.

Lead, tin Attack accelerated only in severe environments, such as marine and some indiatrial.

Tin I zinc plating (80 /20) on steel

Attack accelerated only in severe atrrspheres and condtions of total Immersion.

Pure aluminium and

alloys not containing si,stantial additions of copper or zinc

When aluninium is alloyed with appreciable amounts of copper becomes moe noble and when alloyed with appreciable

amounts of zinc it becomes less noble. In marine or industrial

atmospheres or when totally immersed, alunnium alloy suffers accelerated attack when In good electrical contact with another aluminium alloy that contains substantial copper, such ax wrought alloys 2024 and 2014 and cast alloys LM 4-M and BS L92. The aluminium-zinc alloys, being less noble, are used as cladding for the protection of the stronger aluminuim alloys,

Cadmium No acceleration of attack on cadmium except in fairly severe atmospheres in contact with an aluminium alloy containing copper and under conditions of total immersion,

Attack on zinc accelerated in severe environments such as marine and industrial and under conditions of total immersion,

These metals are generally anodic to aluminium and suffer attack when corrosion occurs, thereby protecting the aluminium,

Zinc and zinc alloys

Magnesium and magnesium- base alloys

Attack on magnesium accelerated in severe environments such as marine and industrial and under conditions of total immersion,

Attack on alurntnium may also be accelerated.

Titanium Not many data available, but attack on alurTinium is known to be accelerated in severe marine and industrial conditions and when immersed in seawater.

These metals form protective films that tend to reduce bi-metallic effects. Where attack occurs the aluminium base material suffers.

Stainless steel

(18 / 8. 18/8/2 and 13%, Cr)

No acceleration of attack on aluminium in moderate atmospheres, but attack may be accelerated in severe marine and industrial atmospheres and under conditions of total irrynertion. —- No acceleration of attack on aluminium when plating is not less than 0.0025 mm thick. except in severe atmospheres; also provlded the

preliminary nickel costing us in accordance with requirements of BS 1224.

Chromium plate

51

Steel bracket and 150mm mm. Steel foundation bar

Treatment as for A but with plate lapped to inside of foundation bar. Steel rivets

Outside

Aluminium plate lapped to joggled steel flat bar.

) Galvanised steel bolts with insulating washers and ferrules. Treatment otherwise as for A.

Figure 4.4 - Typical Bi-metallic Connections Between Aluminium and Steel

52

Bulb plate stiffener

Aluminium plating

between

A

Outside Inside

C

Inside

B C

Wood

In dry conditions there is usually no reaction on the aluminium but if the wood is unseasoned or in damp conditions, it should be coated with aluminium or bituminous paint. In very aggressive environments (immersion) a non-absorbent insulating gasket should be fitted as with bi-metallic joints. Where timber is treated with preservative advice should be obtained from your aluminium supplier.

Insulating Materials

In the unusual event of insulating materials becoming saturated, some protection of the aluminium would be necessary for, apart from the possibility of attack from leached-out chemicals, some poultice corrosion could occur, activated mainly by the reduced availability of oxygen. Protection can be afforded by using an inert barrier.

Concrete

Under perfectly dry conditions, aluminium buried in concrete would need no protection. In practice, however, such conditions are rarely achieved therefore it is recommended that in all cases the contact area of the aluminium is coated with a bituminous paint. In no circumstances should the steel reinforcement used in concrete be allowed to come in direct contact with the aluminium as this will result in a bi-metallic reaction which in turn could cause spalling of the concrete.

53



SECTION 5- SURFACE FINISHING

CONTENTS

Title Page No.

INTRODUCTION 57

PRE-TREATMENT 57

ANODIZING 57 Specification Factors for Architectural Type Anodizing 59 Chromic Acid Anodizing 61 Hard Anodizing 61

PAINTING 61

Electrophoretic 61 Electrostatic 61

Paint Performance 62

55

List of Figures

Fig No.Titie Page No.

5.1 Anodizing Programme 58

5.2 Deposition of Colouring 59

List of Tables

5.1 Suitability for Anodizing 60

5.2 Paint Performances 62

56

INTRODUCTION

One of the most important considerations relating to surface finish is the need to have a sound and permanent bond between any applied film or coating and the parent material. In this respect aluminium and its alloys are particularly suitable, providing as they do integral bonding with anodizing and excellent paint keys when suitably etched and de-greased.

PRE-TREATMENT

The surface textures on aluminium, like those on other metals, will be visible through all but the thickest coating so it is as well to consider this aspect before deciding on the final surface treatment. Where positive relief features are required, like ribbing or serrations, these can be easily incorporated into the extrusion shape. The usual cycle for pre-treatment incorporates a de-greasing dip, followed by a rinse and then an etch dip. The make-up and chemical concentration of this etch can be varied to produce a range of surfaces that will affect the final appearance of an anodized finish. These can be graded from the natural metal appearance, through a light grey satin finish to a darker grey frosted appearance.

Specialised surface finishes can be applied, such as chemical brightening, mechanical polishing, scratch brushing and shot or vapour blasting. The special finishes extend from bright reflective polished surfaces, through to heavy peened rough textures.

Aluminium provides an excellent surface for paint. After degreasing, a light etch is used followed, when necessary, by a chemical conversion coating to improve the paint key even further.

All of these services are available directly or indirectly through extrusion suppliers. In

general the level of concentration of pre-treatment chemicals makes them unsuitable for manual non-dip application.

ANODIZING

Anodizing is a controlled surface oxidisation by immersion in an electrolyte, usually dilute sulphuric acid. A low voltage, high amperage direct current is passed through the metal, using the aluminium as the anode and a hard, non-corroding oxide film builds

up on the surface of the aluminium. A less dense layer is subsequently formed in which there are capillary pores. These pores provide the means for further oxidisation, building up the thickness from the base. This film is an integral part of the metal and is not an applied coating.

57

Pro- OPTIONAL TREATMENTS Treatment

Mechanically Chemically Metallic Polish Brighten Colour

Organic Colour

Degrease Scratch Brush

Vapour Blast

Rinse r r

Shot Blast

Light Etch Natural Etch Rinse Anodize Finish Seal

I I I I

FIg. 5.1 - Anodizing Programme

After the actual anodizing operation, the surface film is porous and in a condition to accept colouring agents, if required. If a natural aluminium finish is desired then the material proceeds directly to the final tank which is usually boiling water. The chemical reaction of immersion seals the pores against further moisture penetration, giving a hard, weather resisting surface.

Where colour is required, the choice lies between those obtained from organic dies, as used with textiles, and those obtained from metallic salts. The former gives a range of primary colours, whilst the latter offers colours varying from grey through umber to dark brown and black. As will be seen from Fig. 5.2 the organic dies tend to remain at the top and the metallic salts at the bottom of the surface pores.

58

H Ratio d

= 1500:1

Fig. 5.2 Deposition of Colouring

Specification Factors for Architectural Type Anodizing

M

l7nm

25 micron (25,000nm)

British Standards lay down specifications to govern the quality of anodizing. BS 1615 covers general anodized coatings in aluminium and BS 3987 covers external architectural applications. European standards are covered by the Qualanod quality control scheme.

The average thicknesses readily available are usually designated in AA values, the figures conforming directly to the film thickness in microns.

Applications

5 Furniture and other indoor products. Also used with chemically brightened material where a thicker coating would tend to reduce reflectivity.

101 Internal applications likely to have more robust

155 handling such as hand-railing and internal partitions.

25 All external applications such as window frames etc.

59

Natural Organic Metallic dies salts

c) The most appropriate extrusion alloys fordecorative and architectural anodizing are in the 6063 range. Other alloys can be anodized but the finish cannot be guaranteed to meet the requirements of British Standards architectural specifications.

Table 5.1 - Suitability For Anodizing

Alloy Natural Colour Brightened Protective *

6063 V V G-V V

6063A V V G-V V

6082 F F F G

6463 V V E V

2014A F F U G

*This also includes "hard" anodizing

E = excellent V = very good G = good F = fair U = unsuitable

d) In component anodizing, the heat affected zone of welded or brazed joints will show some colour variation from that on the rest of the section. This can vary from slightly darker tone to a very dark grey or even black if a silicon filler wire is used in brazing.

e) There can be slight variation in colour between production batches, so top and bottom colour limits should be agreed with the anodizer. This is particularly so where cast and wrought components are concerned, because an exact colour match is rarely possible due to the marked difference in the chemical composition of the two materials.

f) Electrical contact is extremely important between the loading bars and the aluminium section during anodizing. It is obtained by jigging with non- metallic clamps. The contact areas, however, do not anodize or colour and will therefore leave a light-coloured area even on naturally anodized material. Non-visible surfaces should be shown on drawings so that the clamps can be placed in the best possible position. If all surfaces are visible, then an extra 50 mm should be allowed at each end of the bar for clampings, which can be cut off after anodizing.

60

Chromic Acid Anodizing

The original commercially developed anodizing process used chromic acid as the electrolyte. The procedure is similar to that employed with sulphuric acid but the bath

temperature is higher. The resultant film is softer and thinner (max. 10 microns) but for equal thicknesses it offers more corrosion resistance which makes it ideal for aggressive industrial environments where the relatively soft surface is no disadvantage. As the chromic acid is passive with aluminium, it is also recommended lorfinished components where there are laps or crevices which could retain electrolyte.

Hard Anodizing

Hard anodizing is a low temperature operation, using considerably higher voltage than other anodizing processes. The relatively rough surface produced is extremely dense and hard and is available up to 125 microns thick. The film is normally left unsealed but can be waxed or treated with mineral oil. In either case, the abrasion resistance is very high, comparing favourably with that of tooled steel and chromium plate. Hard anodized films have good electrical insulation properties and their excellent corrosion resistance and durability make them ideal for use even in aggressive environments.

PAIN11NG

Aluminium rarely needs to be painted for protection but where colour is necessary on aesthetic grounds a number of high-quality paints and methods of application are available. The surface presented by aluminium is ideal for coating when the correct pre- treatment is carried out. As most coatings are applied by commercial coating companies, the basic pre-treatments are usually varied to suit their particular paint formulations and methods of application. In general, the oxide film is removed and the material de- greased, etched and rinsed. This is adequate preparation for electrophoretic paints but there is an additional chemical conversion coating which is then applied for electrostatic application.

Electrophoretic

The pre-treated workpieces are made anodic and dipped into electrically charged paint tanks. This ensures that the paint is attracted to the metal surface and deposited in an even coating. After rinsing, the material passes through stoving ovens at approximately 160°C for a duration of 15 minutes. During this operation the paint is fused and strongly bonded to the aluminium.

Electrostatic

After pre-treatment, the workpieces are passed through an electrostatic field during which time paint, in the form of wet or powder particles, is sprayed on to the surfaces. The workpieces are then transferred to a tunnel oven where they are stoved at 200°C for 10 minutes.

61

Paint Performance

Comparing paint surfaces and their respective performance is always somewhat subjective, nevertheless Table 5.2 attempts to provide generalised information. Paint and coating companies are always pleased to advise on the best system of application. For all paints and systems, sharp corners provide a challenge in that either a metal or a shadow line appears, depending upon the thickness of the paint. This can be avoided by following good extrusion design although for paint the minimum recommended corner radius is 1mm.

Table 5.2 - Paint Performances

PAINT Method Mean Colour Surface Gloss Colour Hardness Inside Post of Thickness Range Texture Level Fastness Groove Painting Application (Microns) Coating Fabrication

Acrylic Electro-

Poly- phorec urethane (Wet Bath)

25 White Smooth 70% Moderate Hard V. good Good

Poly- Electro- ester static

(Powder Spray)

60-80 Wide

Range Slightly Textured

20%-

93% Good Moderate Shallow

Channels

Only

Excellent

PVF2 Electro- static

(Powder Spray)

30-100

(a)

Small

Range V.good

Fluoro- Electro- Carbon static

(Wet Spray)

25(a) Wide

Range

Smooth 9%- 70%

Excellent Moderate Moderate

Acrylic Electro-

Polyesterstatic (Wet Spray)

25 Full

Range

Smooth 9%- 90%

Good Hard V. good

(a) Suitable for multi-coat applications

Further information is available from: Aluminium Coating Association

Broadway House

Calthorpe Road

Birmingham B15 1TN

62


SECTION 6- FABRICATION

CONTENTS

Titles Page No.

BENDING 65 Machine Types 65 Alloy/Temper 67 Shape Factors 67 Tube Bending 69

Springback 70 Lubrication 70

MACHINING 70 Routing 72 Drilling 73 Sawing 74

JOINING 75 Welding 75 Joint Design 79 Screwing 81

Crimping 82 Riveting 83 Bolting 85 Adhesives 86

63

List of Figures


6.1 Bending Methods 65/66 6.2 Routing (Profiling and

Facing) 72 6.3 Drills 73 6.4 Types of Saw 74 6.5 TIG Welding 77 6.6 MIG Welding 78 6.7 Recommended Diameters

of Screw Grooves 81 6.8 Longitudinal Screw

Grooves 82 6.9 Crimping 82 6.10 Blind Rivets 83 6.11 Self-Piercing Rivets 84 6.12 Clench Rivets 84

List of Tables

No. Title Page No.

6.1 Bending Characteristics 67 6.2 Minimum Bend Radii (1) 68 6.3 Minimum Bend Radii (2) 68 6.4 Minimum Bend Radii (3) 69 6.5 Minimum Bend Radii (4) 69 6.6 Minimum Root Radii R in

Terms of Tube Diameter 71

6.7 Basic Saw Tool Data 74 6.8 Process Capacity 76 6.9 Recommended Filler Alloys

for Welding Parent Metal Combinations 79

6.10 Edge Preparation and Fit Up forTiG and MIG 80

6.11 Permissible Stress Levels 81

64

BENDING

There are several types of torming machine suitable for bending aluminium sections. The choice depends upon the class of section, whether solid open or hollow; the range of support tooling available; the alloy and the temper.

Machine Types

Bending may be carried out by four main methods, as shown in Fig. 6.1. The three roll bender has a central moveable roller which is gradually depressed until the desired radius is obtained. The point bender has a similar method of operation, the load either

being applied gradually or impacted. The roll and point methods of bending are usually applied to robust sections.

In the wrap and the mandrel benders, it is possible to provide formers and other support tools which enable tighter radii to be obtained and minimise the amount of buckling.

As the name implies, the stretch former puts the section into tension and then, moving laterally, wraps it around a former: this method reduces the likelihood of compression failure.

As well as the above basic machines, a number of specialist benders are available, such as the rotating disc, which is suitable for tube bending.

I Wrap Bender

Former Moves Around Section Draw Mandrel Bender

Section Moves Around Former

Fig. 6.1 - Bending Methods

65

-Former

Clamp Guide

FIg. 6.1 - Bending Methods (continued)

66

Section

Fixed Position Drive Rolls

Three Roll Bender

Bending Roll

Bending Point Fixed Position Drive Points

Three Point Bender

L Stretch Former

Alloy/Temper

Heat treated aluminium alloys in the T6 condition have relatively short plastic ranges with proof-stress/ultimate-stress ratios of 0/86: 1 and minimum elongation values of 7% - 10%. Although these values do not provide the whole picture of ductile performance, they give a reliable indication of bendability. Where bending is a primary requirement, it is usual to use material in the T4 solution treated condition. The plastic stress range ratios are then improved to 0.6:1 with minimum elongation values of between 14% and 16%. The slow rate of natural ageing in the 6000 series alloys does not appreciably affect the bending characteristics, except in the most severe bending cases.

Bending at raised temperatures is not usually recommended as the mechanical properties would be affected. It is possible to carry out post-bending heat treatment on T4 temper material that will increase its properties towards those of the T6 condition. Care should be exercised with thin sections as some distortion could occur under this treatment.

Table 6.1 - Bending Characteristics

Alloy Temper Bending Index

6063 T4 T6

V G

6063A 14 T6

V G

V=very good

6082 T4 T6

G F

G = good

6101A T6 G F=fair

6463 T4 T6

V G

2014A 14 T6

G F

Shape Factors

The complexity of shapes available in aluminium alloys makes it very difficult to provide information to cover every situation. By considering the behaviour of the various elements of the shape in relation to the bending axis it is possible to predict the most likely mode of failure when bent through too tight a radius. In most cases, the neutral axis of the section and the bending axis almost coincide but this is not true for stretch- forming where, because of longitudinal tension, the bending axis is assumed to move outside of the section.

67

The following tables give minimum bend radii for section elements under the various forms of bending stresses.

Radii values are to the neutral axis and are given in multiples of y.

y is the maximum distance from outer fibres of the element to the neutral axis of whole section. t is thickness of element.

Flange denotes shaded element parallel to the plane of bending.

Web denotes shaded element vertical to the plane of bending.

The use of support tooling in the buckling modes can reduce the minimum radii below the levels shown in the tables. The extent of the reduction depends upon the type of tooling used.

Table 6.2 - Minimum Bend Radii (1) y t 1 2 4 8 12

WEB TENSILE

Alloy Temper =1

6063 T4 O.7y 0.7y O.8y 2.Oy 3.5y L T6 O.8y 0.By l.4y 3.Sy 7.Oy L

6082 T4 2.5y 2.5y 2.5y 3.Oy 5.Oy

T6 2.5y 2.5y 2.5y 3.5y 7.Oy

Table 6.3 - Minimum Bend Radii (2) y WEB t 2 3 4 6 BUCKLING

Alloy Temper C1

6063 T4 l.Oy 3.5y 8.Oy 20.Oy

T6 l.Oy 4.Oy 1O.Oy 20.Oy

6082 T4 l.8y 4.Oy 1O.Oy 20.Oy F1 T6 l.8y 5.Oy 1O.Oy 25.Oy

68

Table 6.4 - Minimum Bend Radii (3) FLANGE WIDTH

THICKNESS 4 8 FLANGE TENSILE

Alloy Temper

6063 14

T6

7.Oy 8.Oy

10.Oy lO.Oy

6082 14 8.Oy Boy

T6 10.Oy lO.Oy

Table 6.5 - Minimum Bend Radii (4) FLANGE WIDTH

THICKNESS 4 8 FLANGE

BUCKLING

Alloy Temper

6063 T4

T6

6082 T4

5.Oy 8.OY

8.Oy 20.OY

7.Oy l2.Oy

J

16 8.Oy 2O.Oy

N.B. Where flanges have bulbs greater than 3t thick they can be bent to radii 60% of those shown in the table.

Tube Bending

The recommended methods of tube bending are wrap and draw mandrel. Although three point bending can be used, there is less control particularly with thin-walled tubes in the stronger alloys and tempers. Aluminium tubes can be readily bent but, like all materials, there are limits and the key to successful bending is to understand them and take appropriate action at both the design and fabrication stages.

Failure modes are, once again, tensile tearing and compression buckling but there are in-between situations where wrinkling, necking and flattening can occur without causing fracture of the tube. To prevent these surface defects or to restrict them to an acceptable level, the tubes can be filled with sand, springs or low melting materials such as Wood's metal.

69

These are all established methods of providing internal support which, together with the use of external groove formers and followers, provide the maximum level of bending control.

Table 6.6 shows the minimum root radii for a range of tube sizes based upon diameter! wall thickness ratios, alloys and tempers but ignoring flattening.

Sprlngback

Although the degree of springback can be calculated for a specific section that has been bent around a given radius, it involves a lengthy process. The more usual method of establishing springback is to carry out trials prior to a production run. Generally, sections which are symmetrical and have the major portion of their material away from the neutral axis exhibit less springback than a heavy centred cruciform section or an asymmetrical T-bar.

Lubrication

Friction between the surfaces of steel forming tools and the natural surface oxide of the aluminium creates the need to lubricate both work and tools. This helps to reduce tool wear and prevent damage to the surface finish of the formed parts. Depending upon tool shape, section size and alloy, the lubricants commonly used include mineral oil, lard oil, proprietary water soluble compounds and waxes.

MACHINING

Aluminium alloys are amongst the most machinable metals and can be cut at high speeds. Two basic properties influence the machining operation:

a) the high co-efficient of linear expansion of aluminium.

b) the friction generated between small tools and aluminium.

The problems associated with the above characteristics can easily be overcome by using a combined lubricant and coolant.

Machines normally found in a workshop are suitable for use on aluminium. The best results are obtained with relatively high speeds and it is frequently found that woodworking machines can be employed for machining, providing they have sufficient power and rigidity. High speed steel tools may be used on all the aluminium alloys. Plain carbon steels may also be used for short runs but they do not have sufficient life for quantity production. For long production runs tungsten carbide tips are recommended but even these tools would require regular resharpening particularly when used with anodized material. A chip breaker should be used on alloy 6082 for high speed operations to avoid the formation of long spiral swart.

70

Table 6.6 - Minimum Root Radii R In Terms of Tube Diameter

30

tr

o 20

Ill S - ——--———- ———-

lEt 2D 3D 4D 50

Minimum Root RodS In Terms Of lobe Diomneter

Wrap Bends

MATERIAL CHARACTERISTIC CURVE DESIGNATION AND TEMPER WRAP MANDREL

6063 F B B T4 B B T6 C C

6082 F B B T4 C C T6 D D

6101A T6 C C

4U -

30

C

o 20

10

S

15 5

lD 2D 3D 4D 5D

Minimum Rout Rods In Terms Of Tube Diameter

Mandrel Bend

71

Where extensive removal of metal is to be carried out, there is always the possibility of distortion occurring. Machining practices will also affect the amount of distortion that takes place. Cooling and lubrication should be generous but even so, over-tightened chucks could add to other stresses occurring through thermal expansion. If there is any doubt, the material supplier should be consulted.

Routing

One of the best methods of machining aluminium is by routing. This resembles a milling operation, giving a good surface finish, as fine as 0.75 micron, and can be used with spindle speeds up to 24,000 rpm. The high operating speed, in conjunction with low loading, ensures smooth, easy control which is essential when following the contours of a complex template. See Fig 6.2.

Helix angle

Radial rake Primary

clearance

Fig. 6.2 - Routing (Profiling and Facing)

72

CUlliNG SPEED FEED HELIX RADIAL CLEARANCE rn/mm rn/mm ANGLE RAKE

Profiling Up to 6 600-2100 Reduced

speeds Facing: necessary Upto with 25° 5-7° 5-10° 6000 increase

in work thickness

Drilling

As with other aluminium machining operations, drilling can be carried out at very high speeds. Special machines for use with small diameter drills work at 80,000 rpm, most

drilling operations, however, are carried out at more modest speeds. The cutting performance ot a drill is influenced by its peripheral speed and this should be taken into

account when deciding upon the spindle speed for a given drill diameter.

Drills should be inspected regularly to ensure that they keep their bright finish and

polished flutes to ensure rapid chip removal and prevent build-up. When necessary, the drills should be reground with care being taken to ensure thatthe chisel edge retains its correct length and the web atthe drill point does not thicken. Should thickening occur there will be increased end pressure on the drill with the possibility of drill breakage.

When drilling deep holes, particularly of large diameter,excessive heat is generated and if not dissipated by the coolant, hole contraction could take place.

DRILL ELEMENT TOOL ANGLE

PointAngle,H 118°

Helix AngIe 20 - 25°

Clearance Angle, 0 12 - 20°

Flutes Polished

Web Thickness Thiner than that used for other metals

Fig. 6.3 - Drills

73

Sawing

Modern saws used in the fabrication of aluminium sections give clean, virtually burr-free cuts provided that the correct tooth size and rotation speed are used and the teeth kept sharp. This is particularly so for tungsten carbide tipped blades which are in general use for aluminium. This type of blade gives excellent results on the hard surface of pre- anodized sections. Feed will vary with the type of saw, section size, alloy and temper but should never be below 0.05mm per tooth. When cutting thin sections, it is advisable to have two or more teeth engaging at the same time.

Table 6.7 sets out basic tool data. The lower speed range is recommended for high speed steel blades and the higher range for tungsten carbide tipped blades. It is always advisable to use a cutting fluid.

High speed steel Segmental teeth

Top clearance

Th Fig. 6.4 - Types of Saw

Table 6.7 - Basic Saw Tool Data

74

Top clearance

Depth of Top rake gullet

Depth of gullet

Type of Blade Cutting Teeth Angles Saw & Size Speed Pitch Gullet Top Clearances Blade Depth Rake Top Side Material mm m/min mm mm

Circular 250-460 8.5-13 Handfeed: High dia 1500 6.4 12-18° 20-30° Speed x to Hollow to Powerfeed: 1-2° Steel 2.3-3.7 2400 Ground 12.7 15-24° 25-35°

thick Circular 560- 1200 coarse Handfeed: Seg- 1220 to 25-50 5-12° 7-9° mental dia 4500 Chip- 12.7- Powerfeed: 1.2° Inserted x breaker 57 10-20° 5-7° Carbide 64-12.7 teeth Tips thick

JOINING

Aluminium alloys can be connected in a variety of ways. The usual methods, all well- established, are welding, riveting, bolting, screwing, corner crimping and glueing (but aluminium alloys have also been explosively bonded to other materials)..

The combination of material flexibility and the extrusion process enables mating sections to be manufactured in a range covering both permanent and releasable types of sliding, rolling or straight clip connections. Details of this type of joining are given under Section 11, Design.

Welding

Aluminium welding is a widely accepted method of fabrication, with no shortage of competent personnel in the engineering and manufacturing industries. There are several methods available, the basic ones being Tungsten Inert Gas (hG) and Metal Inert Gas (MIG). As the titles suggest, both are inert gas shielded systems where the weld area is shrouded from the air to prevent the reformation of an oxide film.

Preparation

Cleanliness and the removal of the oxide film are most important. The proposed weld areas has to be de-greased, using white spirit or acetone and the joints wiped dry. Adequate ventilation must be provided for any solvents used but is particularly applicable to industrial cleaning solvents, such as carbontetrachloride etc. After degreasing the joint is deaned, using stainless steel wire brushes or a chemical etch cleaner to remove the oxide film. Welding should be carried out as soon as possible afterwards. Carborundum wheels are not recommended as grit particles can become embedded in the surface causing contamination of the completed weld. Filler wire is cleaned by wiping with wire wool; pre-packed spool wire is supplied in a clean condition.

Tungsten Inert Gas

In the tungsten inert gas (TIG) process, the arc is struck between the workpiece and a non-consumable tungsten electrode. The filler wire is fed independently. Although mechanised TIG is available the process is more widely used as a manual system where close control of the welding conditions can be readily maintained. The resulting welds are usually of good appearance and penetration, particularly where no backing plate is available. Fig. 6.5 shows a schematic layout of a typical TIG system and Table 6.8 shows the thickness range.

75

Metal Inert Gas

In the metal inert gas (MIG) process, the arc is struck between the workpiece and a consumable electrode which is constantly fed from a wire spool. The arc is self- adjusting and takes into account small movements of the torch. Penetration and appearance are not so easy to control as in the TIG system, although the addition of pulsed arc equipment will improve the penetration and reduce the need for backing plates. Fig. 6.6 shows a schematic layout of a typical MIG system and Table 6.8 shows the thickness range. Small spool hand guns, sometimes called fine wire, are also available with MIG systems. These dispense with the need for long wire feed leads thereby increasing the area of work accessible from the base unit.

Table 6.8 - Process Capacity

PROCESS

PARENT METAL THICKNESS

EQUIPMENT

Mm I Max. (mm) (mm)

Item

TIG 1.2 9.5 (1)

Composite unit (350 A) Transformer (350 A) H.F. or Surge Injector unit Suppressor Welding Torches

MIG 0.5 kg 1.6 8.0 (2)

Composite unit (250 A) with Wire Feed unit and

Welding Gun for 1 lb Spool

MIG 5kg

4.8 None Composite unit (350 A) with Wire Feed unit and Welding Gun for 10 lb spool

NOTES: (1) Although the TIG process can weld thicker material, for economic reasons it is not normally used for aluminium over 9.5 mm thick.

(2) In theory there is no upper limit for 'one-pound 'MIG, but it is more economical to use 'ten-pound

' MIG for material over 8.0 mm thick.

76

NOTES

1 Composite TIG welding units include all the necessary auxiliaries: argon and water shut-off valves are usually controlled by solenoids, although they may be manually operated.

2 The main power cable, fuse and torch can be air-or water-cooled.

Fig. 6.5 - TIG Welding

77

NOTES

1 The a.c. supply is 11OV for 'one

pound' MIG and 220V tot 'ten-pound' MPG welding.

2 Composite MIG welding units have the contactor and control box built in.

3 The filler wire feed unit is integral with the gun in 'one-pound' MIG and

independent of it in 'ten-pound MIG

Systems.

Dry Bobbin Flowmeter Pressure Reducing Valve Pressure Gauge

4 Voltage pick-up lead for 'one-pound' MIG.

5 The main power cable and gun of 'ten-pound MIG can be water cooled.

6 Arc Voltage in MIG Welding Procedures is measured with a voltmeter connected between the contact tube and the workpiece.

Fig. 6.6 - MPG Welding

78

Wire Feed Unit

Workpiece

Filler Wire

6063 and 6082 alloys can be readily welded to a wide range of other aluminium alloys. Table 6.9 shows the preferred weld filler wire in bold print. An alternative, where given can be used when the finished component is to be anodized and a close colour match is required between the weld area and the parent metal. Alloy 2014A is not shown in the table as this alloy is not recommended for welding using the TIG and MIG

processes.

Table 6.9 - Recommended Filler Alloys for Welding Parent Metal Combinations

PARENT ALLOY

6063 6082

1050a 4043 5356

3103 4043 5356

5083 5356

5251 5356

5454 5356

6061 6063 6082

4043 5356

Alloy 2014A is Not Recommended for Fusion Welding

Joint Design

Good joint design encompasses both the practicalities of the welding process and the structural requirements of the joints in service. The edge preparation will depend upon the type of joint, butt or lap, thickness of material to be joined and the welding process to be employed. Table 6.10 shows typical edge preparation for both TIG and MIG

processes.

The strength of welds is covered by BS CP1 18 which gives permissible stress levels for both 6063 and 6082 alloys in both butt and filled applications see Table 6.11. The reduction in strength from the 0.2% proof stress levels is very marked, allowing for

79

Table 6.10 - Edge Preparation and Fit Up for Tig and Mig

p= Permanent Backing Plate c= Temporary Backing Plate

THICKNESSt (1) g n a NOMINAL MAXIMUM ROOT INCLUDED JOINT

GAP GAP FACE ANGLE DETAIL (mm) (mm) (mm) (deg.)

MIG TIG

- 0.8c Nil Nil - - $

- - -

3.2c 4.8c 3.2p

1.2c 1.6c 4.8c

- - -

Nil Nil - - Nil 0.8 - -

Nil 1.6 - -

1.6 2.4 - - g 2.4 3.2 - -

4.8 6.4 - - 8.0 6.4c 4.8P

-

- -

6.4c

Nil 0.8 1.6 60 1.6 2.4 1.6 60 4iit 3.2 4.8 Nil 60 Nil 1.6 1.6 75

12.7 15.9

- -

Nil 0.8 1.6 90 Nil 0.8 1.6 90

-

3.2 4.8

1.6 2.4 6.4

Nil Nil - - I Nil 0.8 - -

Nil 1.6 - - jj 6.4p - 1.6 3.2 0.8 60

9.5 - Nil 0.8 0.8 60 HL -

3.2 4.8

1.6 -

8.9

Nil Nil - -

Nil 0.8 - - g

Nil 1.6 - -

12.7 19.0 25.4

- - -

Nil 1.6 3.2 60 r Nil 1.6 4.8 60 Nil 1.6 6.4 60

Li - 0.8 Nil Nil - -

[JJ - -

- -

1.2c 2.4c

1.6 3.2c

Nil Nil - - Nil 0.8 - -

flu

Nil Nil - - Nil 0.8 - - g n

1) Minimum Thickness of Parent Metal 80

contingencies in the welding process and the reduced property levels of the weld heat affected zones. The most cost effective way of designing welded structures, therefore, is to keep the welded connections clear of maximum stress points, as far as possible.

Table 6.11- Permissible Stress Levels

Screwing

ALLOY

BUTT WELDED JOINTS &

REDUCED HAZ.

FILLET JOINTS (WELD METAL)

TENSION COMPN TRANSVSL LONGITL

6063

6082

31

51

19

31

54

54

31

31

Permissible Stresses for Table Welded Joints in N/mm2 HAZ = Heat affected zone

The ease with which aluminium alloys can be drilled or punched and the incorporation of screws ports or channels in extrusions has encouraged the use of stainless steel self-tapping screws as the standard method of joining, particularly in the window and door industries. The stainless steel threads bite into the aluminium to give a very positive connection. A typical patio door will use two self-tapping screws per kilogram of aluminium section used.

Screw ports are rarely fully closed as the use of 300 degree ports, (Fig. 6.8), gives a very marked improvement in extrudability with very little loss in pullout strength. The dimensional accuracy of the port diameter is very important and all extruders have standard bore dimensions for each screw size. It is advisable to contact extruders at the die design stage and where possible provide sample screws.

— \ — \

__ \ 1.78mm (mm) 60°

/ I

N / .. / .... /

Screw Size

Screw Dia. (mm)

Screw Groove Int. Dia. (mm)

6 3.45 3.20 8 4.17 3.56

10 4.88 4.32

12 5.59 5.03

14 6.25 5.74

FIg 6.7 - Recommended Diameters of Screw Grooves

81

The use of longitudinal screw grooves, (Fig. 6.8), is not so widespread but the correct combination of slot width and screw size can ensure high pullout values. Some care is necessary if self-tapping screws of triangulated cross-section are used as full engagement of threads may not be possible on both sides of the groove. Advice from the extruder is recommended.

Crimping

Li

Fig. 6.8 - Longitudinal Screw Grooves

In this method of corner connection, the extrusion has a built-in channel recess and afterthe sections have been mitred, the crimping angle is fitted and the joint assembled and held in a rigid jig. Two pressure prongs then upset the section flange into the corner angle, producing a very stable frame assembly, see Fig 6.9. Most crimped corners rely on mechanical connections, but, if required, a slow setting adhesive can be used to seal the corners and provide some extra strength.

Crimping is most likely to be found in the door and window industry but is applicable to any component or form of construction where mitred corners are used.

Fig. 6.9 - Crimping

82

Crimping flange

Riveting

Aluminium can be riveted with aluminium rivets, which are usually driven cold. As there is a tendency for these to work harden during the process they should be closed with the minimum number of blows. It is advantageous to use a long stroke hammer, a size larger than would be used with equivalent diameter hot steel rivets. The rivets should be driven square, not rolled round the edges. Larger diameter rivets (over 12 mm.) can have pre-formed end recess points to assist initial forming. Power operated squeeze riveters are ideal for aluminium as the heads are formed in a single stroke.

Where aluminium is to be riveted to steel structures, the faying (contact) surfaces should be treated with a zinc-chromate primer and brought together while still wet. Hot driven steel rivets should be used but these must be given at least one coat of primer in way of the aluminium, after driving and cooling.

Blind Riveting

This form of joining is well established and uses rivets of tubular construction which enable the workto be carried outfrom one side only. This is particularly attractive where access to the reverse side is difficult. Only one operator is required and there is choice of setting tools - pneumatic, hydraulic or hand held. There are a number of proprietary systems available, in diameters upto 6.5 mm. Rivet lengths are available for combined joint thickness of up to 13 mm. Further details are available from rivet manufacturers.

ELE Mandrel breaks and falls free

Setting tool Clinching mandrel

Fig. 6.10 - Blind Rivets

83

Self-Piercing Riveting

This is a relatively new development which can be used on combined thicknesses of up to 6.5 mm.

T

Clench Riveting

L = 9.5mm

1=6.5mm S = 5.0mm

Fig. 6.11 - Self-Piercing Rivets

A numberof proprietary fastening systems use the gripof threaded bolts with the closing mechanism of clench riveting. Fig. 6.12 shows atypical pin and collet assembly. The bolts are closed from one side in a similar manner to blind riveting, although access to the non-closing side is necessary to install the rivet. The collet deforms around the threaded pin before the pin breaks off at the waisted neck under a pre-determined load. As well as the advantage of ease of installation, these fastenings have excellent vibration resistance.

Fig. 6.12 - Clench Rivets

84

Max.

Countersunk

Bolting

In this method o construction stainless steel, aluminium or mild steel bolts can be used. If stainless steel to 18/8 specification is used, no extra protection is used and the bolts can be used in the conventional manner. The best aluminium materials are 6082 and 2014A but the latter will need painted protection in heavy industrial and marine environments. Alloy 2011 is a widely used and available bolt material but would certainly need protection in any external application. In the case of mild steel bolts, galvanized steel washers MUST be fitted.

All bolts are best used in close-fitting holes and the appropriate tolerance levels will be found in BS CP118.

Where possib'e, control torque levels shoud be specified for aluminium bolts and the indiscriminate use of "tommy bars' is an unacceptable practice. In line with good bolting practice, no part of the threaded portion should be within the thickness of the joint flanges.

The extrusion process allows captive bolt head slots to be built into the extrusion. The bolt can be positioned anywhere along the slot, thus requiring hole accuracy in one dimension only. The internal width of the slot should be dimensioned to suit the maximum width of the boithead across flats thereby locking the bolthead against turning when tightening up the nut. See Fig. 11.3

85

Adhesives

This method of joining has found favour in the high-tech industries, i.e. electronics and aero-space where product cleanliness and close fabrication control were already well- established practices. In more recent years, adhesives tolerant of imperfect joint conditions have been developed and have been taken up, particularly by transport, engineering and even structural industries.

In general, bonding systems still require clean etched surfaces; some respond to unsealed, anodized or conversion coated surfaces. The range of adhesives available covers cold, impact or heat curing together with single or two-part mixes. Each has its own characteristic and therefore advice on suitability for any specific application should be sought from adhesive manufacturers.

86


SECTION 7- CONDUCTIVITY

CONTENTS

Title Page No.

THERMAL 89 Thermal Barriers 89

ELECTRICAL 90

87

List of Figures


7.1 Mechanically Closed Insulating Web 90

7.2 Poured Resin

Insulating Web 90

List of Tables

No. Title Page No.

7.1 Thermal Conductivity 90 0-100°C

7.2 Electrical Conductivity 91

88

THERMAL

Aluminium has a high co-efficient of conductivity. It varies with the different alloys but the value for pure aluminium is 244 W/m0C. See Table 7.1. This property is extremely useful when designing heat transfer products, such as radiators and electrical heat sink units. It is obviously less attractive in those applications where low heat transfer is

required and it is then often necessary to in-corporate components to improve the thermal resistance, e.g. thermally broken window sections.

Thermal Barriers

This solution to the therma transfer problem has been used in the building and construction industries for nearly thirty years. During this time, design and manufacture has been refined so that now two major types of systems are in general use.

In the first, Fig. 7.1, the thermal insulating web, or webs, is made from strip material -

nylon, polyamide etc. - fixed into position by mechanical closing of dovetail type channels in the aluminium sections. Two separate sections are used enabling different surface finishes or colours to be used. The closing methods vary between rolling, pressing and broaching, depending upon individual manufacturers. Internal broaching, can only be used in the case of double web sections.

The second system is frequently referred to as the "pour and cut" method, Fig. 7.2. A specially formulated liquid resin is poured into a semi-closed channel in the single aluminium section. After the resin has solidified, the connecting aluminium strip "a" is cut away leaving the thermal barrier or barriers. As with the first system, a double web section can be produced, in this case by using either a proprietary instantaneous double pour machine or by a two pass procedure on conventional machines.

The structural properties of thermal barrier materials will generally be below those of aluminium and will vary not only between different materials but also over atemperature range of -20°C to +80°C. It is good design procedure, therefore, to keep the thermal barrier material as close as possible to the neutral axis of the final composite section. In practice, this is not always possible and examples can be seen in existing window systems where the thermal barrier is offset. In these cases it is essential that extensive laboratory proving tests are carried out to confirm that the composite section has sufficient strength and stiffness as well as thermal performance.

89

Lips Mechanically Closed On Insert

Solid Insulating Inserts

Aluminium Holding Web

Cut Out "a"

Table 7.1 - Thermal Conductivity 0- 1000C

* International Annealed Copper Standard

ELECTRICAL

Materials that are good thermal conductors are in general also good electrical conductors and this is certainly true of aluminium. The copper/aluminium ratio values for thermal conductivity run virtually parallel to those for electrical conductivity. A special alloy has been developed for electrical use -6101 A. This medium strength alloy has excellent electrical conductivity and good fabricating characteristics. It is available in the T6 temper only.

Compared with copper, an aluminium conductor of equal current-carrying capacity will have cross-sectional area 84% larger but will be only 54% of the weight of the copper bar.

90

Resin Webs

Mechanically Closed

Fig. 7.1 - Mechanically Closed Insulating Web

Poured Resin

Fig. 7.2 - Poured Resin Insulating Web

ALLOY TEMPER W/m°C % IACS

6063 T4 197 50 T6 201 51.1

6063A T4 197 50 T6 201 51

6082 14 172 43.7 T6 184 46.7

2014A T4 142 36.1 T6 159 39.8

Table 7.2 - Electrical Conductivity

Electrical Temperature Resistivity Conductivy Coefficient of (20°C) (200C) Resistance

ALLOY Microhm %IACS per°C

6101AT6 3.133 max. 55.1 mm. 0.00364

91



SECTION 8- TEMPERATURE

CONTENTS

Title Page No.

EXPANSION 95

MECHANICAL PROPERTIES 95

Creep 96 Melting Point 96

93

List of Tables

No. Title Page No.

8.1 Coefficient of Linear

Expansion (200 C - 1000 C) 95

8.2 Influence of Temperature on Properties as % of 25° C Values 96

94

EXPANSION

Although aluminium has a relatively high co-efficient of linear expansion, 24 x 10-6 per degree C in its pure form, the low modulus of elasticity enablesthetemperature induced stresses to be held at a low level. These are usually two thirds of those induced in a similar steel structure. It is still recommended, however, that all long restrained structures likely to be subjected to temperature variation and particularly those in dark colours are checked out in the design stage. Any excessive stresses can be reduced

by fitting simple expansion joints. The general effect of alloying is to reduce the co- efficient of expansion and relevant values for the more common aluminium alloys are shown in Table 8.1.

Table 8.1 - Coefficient of LInear Expansion (20°C - 100°C)

ALLOY TEMPER 106/0C

6063 T4 24 T6 23.5

6063A T4 24

16 23.5

6082 T4 23

T6 23

6101A T6 23.5 6463 T4 24

16 23.5

2014A T4 22

T6 22

MECHANICAL PROPERTIES

Variation in temperature also directly affects the mechanical properties of aluminium alloys. At low temperatures the structural strength and elastic modulus values are actually increased, whilst at higher temperatures they are reduced. A further important characteristic is that at low temperatures aluminium and its alloys show no brittleness which makes them extremely useful in cryogenic applications such as containers for low temperatures liquid gases. The more important properties are given for each of the alloys in Table 8.2. The dotted line inTable 8.2 signifies the maximum temperature at which it is recomended each alloy can continuously be used. Some official codes will accept higher temperatures in specific applications - BS5222 "Aluminium Pressure Piping" sanctions temperatures up to 2000C.

Note: special alloys have been developed for high temperatures applications, contact extruders for performance data and availability.

95

Table 8.2 - Influence of Temperature on Properties as % of 25°C Values

Alloy Temoerature Temper Stress -200 -100 25 100 150 200 300

606316 Ult 130 110 100 95 65 20 10 0.2% PS 115 105 100 95 65 I 20 10

608216 Ult 130 110 100 95 70 I 40 10

0.2% PS 115 105 100 95 L40 5 2014AT6 Ult 124 108 100 85 44 191 11

0.2% PS 125 109 100 87 41 17 10

Modulus I

of Elasticity 110 105 100 100 95 90 70

Creep

At elevated temperatures under the prolonged application of a stress of sufficient magnitude, metal will "creep" and may eventually rupture. This behaviour, the progres- sive deformation without increase in load, does not enter into the design considerations for structures operating below 100°C but may require study in high temperature applications. When creep is considered to be a design factor, more information should be obtained from the material supplier.

Melting Point

As aluminium approaches its melting point it does not change colour, so other means such as temperature sensitive crayons, must be employed if a visual check on the temperature is required. While pure aluminium has a well-defined melting point of 660°C, aluminium alloys have a melting range which, for the alloys listed in the Table 8.2, varies from 570°C to 660°C.

96


SECTION 9- FIRE

CONTENTS

Title Page No.

ALUMINIUM AND FIRE 99

97

List of Tables

No. Title Page No.

9.1 BS 476 Fire Test Series 99

98

ALUMINIUM AND FIRE

ALUMINIUM DOES NOT BURN. It will not ignite. It will not add to the fire load. It will not spread surface flame.

Although aluminium melts at around 620°C, it has a thermal conductivity of four times that of steel and a specific heat twice that of steel. Heat is conducted away faster and therefore a greater heat input is necessary to bring aluminium upto a given temperature than required for steel.

In any application requiring a structural fire resistance measured against time, a test certificate is usually necessary. Although aluminium components have obtained ap- provals above 30 minutes in tests it is not possible to make accurate predictions. It is necessary, therefore, to obtain a test approval for each type of application. Where

higher time ratings are required, aluminium must be used in conjunction with other conventional fire-resisting materials.

The more usual fire performance requirements for aluminium extrusions can be obtained from the results of the British Standards tests shown in Table 9.1.

Table 9.1 - BS 476 Fire Test Series

Part No. Title Aluminium Results

* 4 Non-Combustibility Test Non-Combustible

* 5 ignitibility Test P, not easily ignited

* 6 Fire Propagation Test P. actual index will

vary with thickness

* 7 Surface Spread of Flame Test Class 1. Painted surfaces will reduce performance rating

21 1 Time/Structural 22 Resistance & Insulation ** individual 23 Test component testing

required

99

The British Standard fire tests are laid down in BS 476 and define results irrespective of materials. Aluminium and its alloys achieve the highest possible ratings for parts 4, 5, 6 and 7 and are therefore widely used throughout the construction and other industries where the highest standards of performance are required. Painted surfaces could, however, reduce the levels of performance.

Tests 21, 22 and 23 are used to obtain the performance of a component or unit for strength, integrity and insulation, all compared to time against closely calibrated temperature levels.

** It is usual for aluminium extrusions, in these instances, to be used in conjunction with other materials to obtain resistance times in excess of 30 minutes.

* Indicated highest possible rating.

100


SECTION 10- CARE AND CONTROL

CONTENTS

Title Pag No.

INTRODUCTION 102

HANDLING 102

STORAGE 102

MAINTENANCE 103

101

INTRODUC11ON

In post-extrusion handling, every care is taken by extruders to minimise damage. It is essential that this "good house-keeping" is continued in customers' works and ware- houses. As with other high quality materials, carelessness can cause unnecessary rejection, resulting in higher production costs.

HANDLING

The following recommended practices should be followed:-

(1) Single lengths should never be pulled longitudinally from the middle of a bundle of aluminium sections as the entrapped end will score adjacent sections.

(2) Cleanliness is very important, particularly with sections to be anodised. Gloves should be worn whenever dealing with this type of section as the natural oil from the hands can cause finger print corrosion which will become apparent at the etching stage of the process.

(3) When lifting by crane, double slings should be used as single slings can cause bending damage particularly with bundles of long, light sections.

(4) The sections should always have adequate support when lifted by a fork-lift truck.

STORAGE

Although aluminium alloys are very resistant to atmospheric corrosion, certain simple precautions should be taken during their storage. All materials should be stored away from excessive dust or fumes; particularly when portable gas or oil heaters are used, for as well as pollutants these heaters also produce moisture. Storage spaces should be dry and well ventilated and kept at a constant temperature above 16°C. Any superficial corrosion that occurs on extrusions is usually easily removed by hand cleaning with white spirit. Even the most severe superficial corrosion responds to cleaning with fine wire wool and white spirit.

The more troublesome form of staining is water marking, caused by moisture ingress between sections that are closely nested, e.g. angle bars. This can occur directly or by condensation. In the latter case, it is possible for the moisture to work upwards by capillary action. Stacking in a self-draining position is therefore no solution. It is, however, easily avoided by spacing the sections and ensuring that moisture can not bridge the gap. The stain can be removed by wire-brushing and chemical treatment.

Storage staining and corrosion will not usually have any detrimental effect on the mechanical properties of the material.

102

Vertical racks are preferred for storage. If horizontal storage is unavoidable, care should be taken not to overload racks and to support light sections adequately to avoid local damage at the points ot support. Timber rubbing bars should be fitted to steel racks to minimise abrasion and to avoid spots which could cause condensation under adverse storage conditions.

Racking should be arranged to facilitate easy inspection which should be carried out at regular intervals. As most aluminium alloys look alike, materials should be stamped or colour-coded so that different alloys and tempers can easily be identified. This would not be necessary where an alloy or temper is consistent with a special shape. It is also useful to mark batches on arrival in store to ensure that they are used in the

original delivery sequence.

MAINTENANCE

Aluminium alloys require little or no maintenance to retain their original mechanical properties. Without regular cleaning, however, surfaces can become stained particularly under prolonged exposure on industrial sites. Mill-finished aluminium can be cleaned by rubbing down with fine wire wool and white spirit. Anodised surfaces are more resistant to staining but, nevertheless, benefit from regular washing down with soapy water. Proprietary cleaners are available for both mill finished and anodised surfaces but should they be used, it is absolutely essential that the manufacturer's instructions are strictly adhered to.

103



SECTION 11 - DESIGN

CONTENTS

Title Page No.

DESIGN PROCEDURE 107

VALUE ANALYSIS 107

PRACTICAL DESIGN FEATURES 109

WORKED EXAMPLES 111

Unloading Ramps 111

Pedestrian Balustrade 113 Columns 123

105

List of Figures


11.1 Steel and Aluminium Beams 108

11.2 Examples of Solid Section Aluminium 108

11.3 Built-in Mechanical Fastener 110

11.4 Advantages of Aluminium Versus Steel 110

11.5 Various Snap Fit Connections 110

106

DESIGN PROCEDURE

In designing a section, it is usualto have a performance specification setting out the total requirements of both section and material. This could be part of a much wider

specification for a complete finished product of which the aluminium extrusion is only one of the components. The extent and detail required for such a specification will vary with the application and also within different industries. It is good design practice to have such a "check list" providing, as it does, a target of what needs to be achieved and a logical procedure for assessing different ideas. A comprehensive list of design considerations is set out in Appendix 1.

Rarely will all these factors need to assessed and a more general approach is given in the following flow chart.

Idea

Performance Specification

I I I I•• I. I. .1.. Material Fabrication Appearance Mechanical Durability Special Unit Availability Selection Properties Requirements Cost

4 Machining Shape Strength Atmospheric Electrical

I Conductivity

Forming Surface Stiffness Chemical Unit Weight Finish

Jointing Hardness Fatigue

VALUE ANALYSIS

Although basic material cost is important, it should be balanced against the overall cost of fabrication and subsequent service performance. This is particularly relevant to aluminium extrusions where shapes can be produced that require little or no further fabrication and the aluminium alloys available have characteristics suitable for a wide range of applications.

Aluminium extrusions are usually sold by weight which tends to encourage comparison with other materials on a straight weight/cost basis. This in unrealistic as compared with steel, allowing for the lower elastic modulus, aluminium/steel weight ratios of 1 : 2 are easily attained to equal performance specifications.

107

Ag. 11.1 - Steel and Aluminium Beams

The two beams in Fig. 11.1 have been designed for equal stiffness in both xx and yy axes. The strength of the aluminium beam is well over twice that of mild steel if alloys 2014A 16 or 6082 T6 are used.

It is important always to check the actual deflection requirement as in many cases the steel design has been stress based and the corresponding level of deflection is

automatically accepted without consideration of the real level required.

The economic use of aluminium alloys is not just confined to comparisons with steel and other materials. The proficient use of extrusions can frequently result in comparisons with other aluminium profiles to obtain the optimum shape. Fig. 11.2 illustrates the design of solid sections to give good strength and stiffness in both major axes instead of a more expensive hollow section.

[1 ii

ft_ 11

Fig. 11.2- Examples of Solid Section AluminIum

108

145 .. 100

Steel 21.7 kg/M

0L 150

Aluminium 10.6 kg/M

In other cases, the use of standard structural sections is more appropriate. Two ranges of I beams, channels, T bars and angles are available, namely the specially designed lipped sections conforming to BS 1161 and the range covering structural sections similar to the universal sections used in the steel industry.

in manufacture, the availability of sections that require little or no fabrication can be a major factor in reducing final component costs. This equally applies to site erection

where, apart from light weight, the ability to use hidden fixings can simplify procedure.

PRACTICAL DESIGN FEATURES

Replace several parts

One extrusion can often do the work of several structural shapes joined together and produce a neater, sounder

design, at less cost.

Place metal where It is most effective

Thus, bulbs, fillets and variations in thickness can easily be incorporated for structural advantage and local increases of thickness can be introduced to counter wear and abrasion or permit tapping of screws.

The two bulbs, and root buteress improve inertia and section modulus values as well as increasing torsional resistance.

Hinge Fits

Continuous hinges with built in stop bars plus screw groove for end stops.

A slide fit which allows one shape to move in a circular arc with respect to the other.

109

Slots, holes and threads for mechanical fasteners can be extruded as integral features.

Typical early steel frame section. Typical aluminium frame section.

FIg. 11.4- Advantages of Aluminium Versus Steel

Locking Cover

Fig. 11.5 - Various Snap Fit Conections

110

Adjustable locking connection.

FIg. 11.3 - Built-in Mechanical Fastener

Retractable Cover Adjustable Locking

WORKED EXAMPLES

Unloading Ramps

Single lengths of channel bar are frequently used in tandem to unload wheeled vehicles. In the interests of good working practice, they should always be longitudinally and

transversely restrained.

There are several ways of calculating the size required. The following method is based upon simple point load bending without any axial component. it is assumed that unloading is always controlled and no unusual dynamic loads will occur.

Specification. The ramps should be a maximum weight of 50 kg each. Span 2.5 metres. Operating angle up to 30 degrees. Maximum vehicle load 2.0 tonnes equally shared on four wheels. Maximum tyre width 200 mm with 25 mm clearance.

The initial choice of section size is governed by the final specification requirement, that of type width and clearance.

Channel Section : 254 x 88 x 11 web x 14 flanges (all in mm)

Section properties:

Area 5030 mm2

Modulus Zxx 54620 mm3

Inertia

Radius of Gyration Weight/metre Alloy

lxx 3459100 mm4- Note: as section is used in

this plane check with

property tables to confirm

26.2 mm the way x & y axes are given 13.39 kg/m 6082 T6

111

Slope Q in degrees

Loading. As the vehicle is unloaded it moves out of the horizontal with a considerable shift in its neutral axis and the loading on the first set of wheels increasing. This will be a feature of the individual vehicle. For the purposes of this calculation it is assumed to be 10%, hence -

Maximum individual wheel load = 1 9640N (2 tonnes) x 1 10 = 5400N 4 100

Bending Stresses. The ramp acts as a simply supported beam and with normal wheelbased vehicles will have a central load as the worst condition. (Load Case 2.)

M = WL = 5400N x 2500mm 4 4

Maximum bending moment = 3375000 Nmm

Maximum Stress = 3375000= fbc= 61.8N/mm2 54620

Allowable Stress Levels. See Table 3.2 (From British Standards CP1 18)

6082 T6 alloy

Bending p, 154N/mm2

Deflection

8 = For 6082 E = 68,900N/mm2 48El

8 = 5400x 2500 48 x 68900 x 3459100

8 = 7.45mm

The deflection/span factor = 336

which is well inside the recommended value of 200

Lateral Instability. It is usually advisable to check the ramp for lateral instability. The method for calculating this can be found in BS CP1 18. The cross-tying of the two ramps together with lateral ties will dramatically increase the resistance to lateral instability, but in this case, with the stronger axis of the section acting transversally, instability will not occur.

112

Pedestrian Balustrade

Specification. To enclose an external paved area within the confines of an office block. The railings must meet the requirements of the appropriate British Standards and whilst being functional should have an attractive appearance. Low maintenance is also essential.

BS 3049 Pedestrian guardrail BS 6180 Protective barriers in and around buildings. In this instance BS 6180 applies.

As it is a possible area of assembly, although in an office development, two categories of use are applicable.

From BS 6180 Table 1

Type 4 Office building Type 7b Place of assembly

LOAD FACTORS Tables 2 and 3 from BS 6180

TYPE HORIZONTAL INFILL INFILL MINIMUM U.D.L. IJ.D.L. POINT LOAD BARRIER HEIGHT kN/M kN/M2 kN mm

4 0.74 1.0 0.50 1100 7b 1.5 1.5 1.50 800

Access will be controlled and private so that type 4 will apply.

Material. Aluminium alloy 6063 T6 will meet all the requirements of -

surface finish durability low maintenance

It is also an approved material in BS 6180 and its structural characteristics are set out in BSCP 118.

113

Fabrication Details

76x50 Top rail 70x70x2.5 Posts

1lOOmm

1500mm

E E 0 0

Main stanchions: These are to be set directly into concrete foundations. The stanchion base over the area to be bedded into the ground is to be given two coats of bituminous paint.

Top and bottom rails: These are to be connected to the stanchions using bolted lugs. Bolts to be stainless steel to 18/8 specification.

Balusters: These are to be slotted into the top rail and into punched slots in the bottom rail, then welded into position on both top and bottom rails.

Surface finish: A natural anodized finish is required to AA 25 suitable for external application. This will necessitate the infill panels being anodized as single units. Check availability of suitable facilities.

114

.r 50 x 54

—30x30x2 Balusters

—100mm Max Gap

1500mm

Section Design

The following sections have been drawn up to meet the requirements of the performance specification.

2mm

Stanchion

Baluster

STANCH ION

BALUSTER

Area CCD

Shape factor

—I

215 mm2 43mm 370

76

lop rail

TOP RAIL

54

BOTTOM RAIL

Area CCD Shape factor

300 mm2 74mm 370

50

:: Rad.:

70

70 Overall thickness 2.5mm

Bottom rail

Area 661 mm2 Area 585 mm2 CCD 99mm CCD 89mm Shape factor 298 Shape factor 334

115

The CCDs are well within the capacity of most medium sized presses with container diameters of 150 mm.

The shape factors are slightly above average, but still acceptable.

The thicknesses have been checked out against Table 1.2 and are within the level

required for 6063 material.

A further check is necessary on the top rail for both the extrudability ratios of the semi- enclosed area and the depth/width ratio of the side channels.

Large recess = 59 mm x 45 mm = 2655 mm2

Gap = 31 mm Gap2 = 961 mm2

Area/gap2 ratio = 2.76: 1

The section can be classed as a solid and the extrudability is acceptable.

Side channels Depth 17.5 mm

Gap = 3.5 mm

Depth/gap ratio = 5:1

This is not acceptable so it is necessary to reduce the outer flange from 20 mm to 13 mm.

The internal depth of the channel is now 10.5 mm The depth/gap ratio is now 3 : 1

This is now acceptable and the new top rail section details are as follows:

Area = 550 mm2 CCD = 89mm Shape factor = 314

Section Properties

STANCHION - Area 661 mm2 Modulus Z 14190 mm3 Inertia I 496680 mm4

TOP RAIL - Area 550 mm2

(modified) Modulus Zy 11150 mm3 Inertia ly 423740 mm4

BOTTOM RAIL - Area 300 mm2 Modulus Zy* 5650 mm3 Inertia ly * 152500 mm4

*effective area values (less slot area)

116

BALUSTERS - Area 215 mm2 Modulus Z 1838 mm3 Inertia I 27600 mm4

Loading

STANCHIONS The load is applied to the stanchion through the top rail.

Hence load 740N1M x 1.5M = 111ON

RAILS The load for the top and bottom rails is the same as that for the stanchions.

Hence load = 111ON

BALUSTERS Central point load 500N

STANCH IONS Load Case Cantilever

f = ..WL = lllQNxllQOmm = 86.OON/mm2 Z 14190 mm3

TOP RAIL Load Case Two span, simply supported UDL

f = - YL. = lllONxl500mm =1886N/mm2 8Z 8 x11150 mm3

BOTTOM RAIL Load Case Simply supported UDL

f = WI. = lllONxl500mm = 36.BON/mm2 8Z 8x5650mm3

BALUSTERS Load Case Simply supported central point load

f = Y.L. = 500N x 100mm = 68.OON/mm2 4Z 4x1838mm3

117

From CP 118 "Structural Use of Aluminium", the allowable stress levels for 6063 T6 are as follows (see Tables 3.2 and 6.11)

Bending 96N/mm2

Shear 52N/mm2

Welded areas

Heat affected zones Bending 31N/mm2

Shear 19N/mm2

Welds (throat area) 31 N/mm2

Assessment of bending stresses.

STANCH IONS No welding. Allowable bending stress 96N/mm2 Section acceptable

TOP RAIL Heat affected zone is in maximum bending position. Allowable stress level 31 N/mm2. Section acceptable.

BOTTOM RAIL Heat affected zone in maximum bending position. Allowable stress level 31 N/mm2. Section not acceptable - re-design

BALUSTER Heat affected zone clear of maximum bending position. Allowable stress level 96N/mm2. Section acceptable.

Redesign of Bottom Rail.

Large bulbs placed at toes of flanges and merged into 2 mm thickness by 45 degrees fillet to ease transition.

New extrudability factors

Area = 350 mm2 CCD = 74mm Shape factor = 335

118

54

New geometric properties (effective less slot area)

ModulusZy = 6830mm3 Inertialy = 184410 mm4

Re-check bending stress

= = lllONxl500mm =30.5Nfmm2 8Z 8 x6830

Allowable stress for heat affected zone material from Table 6.11

= 31N/mm2

New section acceptable. Weld

Weld Strenath

The balusters are slotted into the top channel and welded B a luster in position. They stand on the top of the bottom channel web and are welded into position. The top welds hold the baluster in the line of the top rail and do not directly take Weld 25mm each side the full load. This is also the case at the bottom of the (no transverse welds) baluster and it is reasonable, therefore, to consider only the bottom rail.

Consider aweld leg length of 3 mm. The critical dimension weld design is the throat width. It is usual to define this Throat dimension as a fraction of the leg length.

Leg I For 90 degrees angle throat factor = 0.7.

Weld Throat width = 0.7 leg length = 2.1

Effective weld area = length of weld x throat width 5Ommx2.1 mm=105mm2

Shear load on weld = QQII = 250N/mm 2

Stress in weld = QJ = 2.3NImm2 105 mm2

Allowable stress in weld material = 19N/mm2

With such a high safety factor, the baluster can be welded to the bottom rail in a similar manner to that at the top, on the longitudinal sides only.

Weld strength acceptable, top and bottom welds resisting downward load with top weld also resisting sideways load.

119

TIG WELDING

Electrode Filler Nozzle Argon Alt. Weld Weld dia. rod dia. Bore flow current speed passes mm mm mm Llmin A mm/mm

2.4 2.4 9.5 5.7 110 190 1

No edge preparation and no gap between sections.

Filler rod material - 4043 or 5356 This material would give better colour match after

anodising

Deflections.

STANCHIONS Load Case Cantilever

6 = WL3 = 1110x11003 = 15.14mm 3E1 3 x 65500 x 496680

TOP RAIL Load Case Two span, simply supported UDL

8 = WL3 = lllOx 1500 = 0.73 mm 1 85E1 185 x 65500 x 423740

BOTTOM RAIL Load Case Simply supported UDL

8 = = 5x1110x15003 = 3.93mm 384EI 384x65500x 184410

BALUSTERS Load Case Simply supported central load

8 = 1.3 = 500x l000 = 5.70 mm 48E1 48 x 65500 x 27600

Allowable Deflection.

BS6180 sets out a maximum deflection standard of 12 mm but calculated on the basis of:

Aoolied load + wind load 2

120

This requires a wind load assessment to be made using BS CP3 chapter V "Wind

Loading". It is necessary to know where the installation is to be, as the wind code lays down a map of basic wind speeds related to area and on which the dynamic wind pressure is based.

Birmingham and the West Midlands are in the 44m/sec area.

This value is, however, factored for there are other considerations:

Si Topography (site exposure) For urban areas the value is i .00.

S2 Ground roughness and height For urban areas the value is 0.56 in this case.

S3 Probability levels The probability of the maximum design wind speed being exceeded. The usual factor is once in 50 years and the value is 1.00.

Wind speed is therefore:

44 x 1.00 x 0.56 x 1.00 = 25 m/s.

Dynamic Pressure = 383N/m2

Total area per panel span of balustrading

= 0.59m2

Wind load = 383 x 0.59 = 226N

The worst case is the stanchion with an actual deflection of 15.14 mm.

Therefore consider the stanchion.

Code BS61 80 requires the deflection to be considered using an equivalent total load which equals:

Basic load + Wind load 2

121

And where the resulting deflection should not exceed:

Span between stanchions 125

Equivalent design load = 111ON + 226N = 668N 2

Stanchion deflection with load 668N = 9.20 mm

Permissible deflection = j.QQ = 12mm 125

Stanchion is acceptable.

It is obvious that all the other sections will meet the deflection standard.

Temperature.

In hot sheltered sites thermal expansion should be considered and in general it is preferable to fit expansion joints in long runs of balustrading.

Assumed erection temperature 16°C

*Max surface temp. on aluminium 36°C

Temperature rise 20°C

*This will vary on the degree of sun and wind as well as on the colour of the aluminium.

Thermal expansion of 6063 = 23.5 x 1 061°C

Fit expansion joints at 15 metre intervals

Expansion = 23.5 x 10-6 x 20°C x 15000 mm

= 7.1 mm

Stress induced in the rails if this expansion is not relieved can be obtained from:

Stress = E Strain

= 69000M/mm2 x 7.1 mm = 32.4N/mm2 15000mm

If expansion joints are not fitted, the 32.4N/mm2 stress will be absorbed axially down the rail. To check the ability of the rail to withstand this stress it will be necessary to calculate the combined bending and axial compression in a similar mannerto that given

122

in the column example page 11.20. The bottom rail, however, is performing very close to its allowable stress level e.g. 30.5N/mm2 to 31.ON/mm2. Therefore it will not withstand the extra temperature induced stress. Expansion joints at 15 metre intervals are therefore necessary. The above proposed design meets all the requirements of BS 6108 and is therefore

acceptable.

Columns

a) An aluminium alloy column, 1 metre long, is fixed and restrained at both ends. The cross section is a 50 mm x 50 mm x 2 mm hollow box and subjected to a 62 kN concentric load. It is necessary to confirm the most appropriate alloy and

temper.

Section Properties

Section Area 384 mm2 Section Modulus 5910 mm3 Radius of gyration 19.6 mm

Actual axial stress f = Load Cross sectional area

= 62000 = 161.5N/mm2 384

As the column is rigidly held at both ends the effective length from Table 3.3

= o.7L = 700 mm

X = Effective Lenath = 700 mm = 35.7 Radius of gyration 19.6 mm

Using this value in the strut curve Fig 3.3 the 35.7 vertical ordinate gives the

permissible axial stress for a number of alloys and tempers.

Pc = 163N/mm2 for 2014A T6

A 50 x 50 x 2 mm box hollow in 2014A T6 is acceptable.

b) If the load in the above column is offset by 10 mm, will the column still be strong enough?

The load eccentricity will induce bending stresses as well as axial stresses into the column.

123

The simplest way to check is to considerthe axial and bending stresses individually and then check against the requirements of the combined stresses.

The axial stress at 161 .5N/mm2 is 99% or the permissible stress of 1 63N/mm2 so there is obviously no allowance left for bending in the original section.

Increase section size to 70 x 70 x 2.5 mm box alloy 2014A T6.

Section properties

Section Area 675 mm2 Section Modulus 14670 mm3 Radius of gyration 27.6 mm

= 700mm = 25.4 27.6 mm

From Fig. 3.3 25.4 ordinate for 201 4A T6 Gives the permissible stress = 1 77N/mm2

Actual axial stress from concentric load

f c Load = 62.000mm Cross sectional area 675mm2

f c = 92N/mm2

Induced bending stress = f bc

Moment = 62,000N x 10mm = 620,000 N mm

f bc Moment = 620.000N mm Section modulus 14,670 mm3

f bc = 42.3N/mm2

Permissible compressive bending, stress for 2014A 16 from Table 3.2

= 202N/mm2

Individually the bending and axial stress levels are within the permissible stresses laid down in BS CP 118, but the should be checked against combined stress allowances.

124

For combined bending and axial compression

+ I bc must not exceed 1

Pc Pbc(1-J Pe

Where f c axial compressive stress Pc permissible axial compressive stress

5 bc compressive stresses due to bending Pbc permissible bending compressive stress Pe Euler critical stress for buckling

where Pe =

Pe it2 x 72.400 = 1108N!mm2 25.42

fc = 92N/mm2 Pc = 177N/mm2

5 bc = 42.3N/mm2 Pbc = 202N/mm2

Combined stresses = .52 + .23 < 1

= .75 < 1

New 70 x 70 x 2.5 mm box section in 2014A T6 is within combined stress

requirements in BS CP 118.

Further modifications could be carried out by reducing the size of the section in order to obtain a more efficient solution and thereby approximating the combined stress ratios towards unity.

125



GLOSSARY OF TERMS

Term Definition

Ageing Precipitation from solid solution resulting in a change in properties of an alloy, usually occurring slowly at room temperature (natural ageing) and more rapidly at elevated temperatures (artificial ageing).

Angularity Conformity to, or deviation from, specified angular dimensions in the cross section of a shape or bar.

Annealing Thermal treatment intended to soften a metal or alloy hardened by cold work or artificial ageing.

Anodizing An electrochemical method of producing an integral oxide film on aluminium surfaces. See Section 5.

Anodizing Describes material with characteristics that make it suitable for Quality decorative anodizing after suitable preliminary treatment.

Billet A cast aluminium product suitable for subsequent extruding. Usually of circular cross-section but also may be rectangular.

Bow The deviation, in the form of an arc, of the longitudinal axis of a product.

Bright A process used to obtain highly reflective and bright anodized anodizing surfaces using alloy 6463.

Buffing A mechanical finishing operations in which fine abrasives are applied to a metal surface by rotating fabric wheels for the purpose of developing a lustrous finish.

Burr A thin ridge or roughness left by a cutting operation such as routing, punching, drilling and sawing.

Chemical Treatment to improve the reflectivity of a surface. brightening

Circumscribing (CCD) A circle that will just contain the cross section of an extrusion, circle diameter usually designated by its diameter.

127

Cold work Plastic deformation of metal at such temperature and rate that strain hardening occurs.

Concavity A concave departure from flat.

Concentricity Conformity to a common centre as, for example, the inner and outer walls of round tube.

Container A hollow cylinder in an extrusion press from which the billet is extruded.

Conversion Treatment of material with chemical solutions by dipping or spraying coating to increase the surface adhesion of paint. See Section 5.

Corrosion The deterioration of a metal by chemical or electrochemical reaction with its environment. See Section 4.

Direct extrusion A process in which a billet in the container is forced under pressure through an aperture in a stationary die.

Drift test A routine sampling test carried out on hollow sections produced by bridge or porthole methods, in which a tapered mandrel is driven into the end of the section until it tears or splits.

Drawing The process of pulling material through a die to reduce the size, change the cross section or shape, or work harden the material.

Etching The production of a uniform mafl finish by controlled chemical (acid or alkali), treatment.

Etching test The treatment of a sample using a chemical reagent to reveal the macro-structure of the material.

Extrusion ratio The ratio of the cross-sectional area of the extrusion container to that of the extruded section (or sections in the case of multi-cavity dies).

Fillet A concave junction between two surfaces.

Flutes Longitudinal concave corrugations with sharp cusps between them used to break up the surface decoratively.

Free machining An alloy designed to give small broken chips, superior finish and/or alloy longer tool life.

Full heat Solution treatment followed by artificial ageing. treatment

128

Grain growth The coarsening of the grain structure occurring under certain conditions of heating.

Grain size The mean size of the grain structure usually expressed in terms of the number of grains per unit area or as the mean grain diameter.

Hardness The resistance of a metal to plastic deformation usually by controlled indentation.

Heat treatable An alloy capable of being strengthened by suitable heat treatment. alloy

Homogenization A high temperature soaking treatment to eliminate or reduce segregation by diffusion.

Indirect extrusion A process whereby a moving die located at the end of a hollow ram is forced against a stationary billet.

Mean diameter The sum of any two diameters at right angles divided by two.

Mean wall The sum of the wall thickness of tube measure at the ends of any thickness two diameters at right angles, divided by four.

Mechanical Those properties of a material that are associated with elastic and properties inelastic reaction when force is applied, orthat involve the relationship

between stress and strain. These properties are often incorrectly referred to as physical" properties.

Modulus of The ratio of stress to corresponding strain throughout the range Elasticity where they are proportional. Also referred to as "Young's Modulus".

Modulus of The ratio of the unit shear stress, in atorsion test, to the displacement Rigidity caused by it per unit length in the elastic range.

Non-heat An alloy incapable of being strengthened by thermal treatment. treatable

Ovality The departure of the cross section of a round tube, bar or wire from a true circle.

Percentage The increase in distance between two gauge marks that results

elongation from stressing the specimen in tension to fracture.

Physical The properties, other than mechanical, that pertain to the physics properties of a material; for example, density, electrical conductivity, thermal

expansion.

129

Pitting Localised corrosion resulting in small pits or craters in the metal corrosion surface. See Section 4.

Porthole die An extrusion die that incorporates a mandrel as an integral part of its assembly. Bridge and spider are special forms of this type of die, which are used to produce extruded hollow products from solid extrusion billets.

Proof stress The level of stress used to signify the limit of proportionality designated at the point of 0.2% strain for aluminium and it alloys. See Section 3.

Quenching Controlled rapid cooling of a metal from an elevated temperature by contact with a liquid, gas or solid.

Residual stress That internal stress which is left in afinished product afterfabrication.

Sealing A treatment applied after anodizing to reduce the porosity of the surface.

Segregation Non-uniform distribution or concentration of impurities or alloying constituents that arises during the solidification of a billet.

Solution heat A thermal treatment in which an alloy is heated to a suitable treatment temperature and held for sufficient time to allow soluble constituents

to enter into solid solution wherethey are retained in a supersaturated state after quenching. See Section 2.

Stabilizing A thermal treatment to reduce internal stresses in order to promote dimensional and mechanical property stability.

Stepped An extruded shape whose cross section changes abruptly in area at extrusion intervals along its length.

Stretching The straightening of extruded and drawn materials by imparting sufficient permanent extension to remove distortion. Specific levels of stretching (permanent set) can be imparted to relieve internal stresses.

Tempers Stable levels of mechanical properties produced in a metal or alloy by mechanical or thermal treatments.

Twist A winding departure from flatness.

Ultimate tensile The maximum stress which a material is capable of sustaining in strength tension under a gradual and uniformly applied load.

130

Waterstains Superficial surface oxidization due to the reaction of water films held between closely adjacent metal surfaces such as nested angle sections. The appearance varies from iridescent in mild cases, to white, grey or black in more severe instances.

ABBREVIATIONS

E = Young's modulus of elasticity * N = Newton = kiloaramme

G = Torsion modulus gravity r = Radius of gyration k = End fixity co-efficient

* P = Pascal = N/m2 = Slenderness ratio = Micron

8 = Deflection P = Stress suffix - t - tension c - compression * iN/mm2 = 1MPa

both terms are used to define stress levels

131



LIST OF APPENDICES

No. Title Page No.

APPENDIX 1 DESIGN CONSIDERATIONS 135

APPENDIX 2 BEAM STRESS AND DEFLECTION TABLES 139

APPENDIX 3 PREVIOUS B.S. DESIGNATIONS 153

APPENDIX 4 COMPARISON OF NATIONAL SPECIFICATIONS- WROUGHT ALLOYS 155

APPENDIX 5 CHEMICAL COMPOSITION LIMITS AND MECHANICAL PROPERTIES 159

133



APPENDIX 1 - DESIGN CONSIDERATiONS

135

The following list contains most potential considerations likely to arise in the design of aluminium extruded products.

ALLOY

TEMPER

MECHANICAL PROPERTIES - 0.2% proof stress Ultimate stress % elongation Compressive strength

Axial loading - column length end fixing load eccentricity

Shear stress Bearing stress (jointing) Surface hardness Torsion Fatigue Stiffness

SECTION DESIGN - Size, shape and thickness Production availability and section extrudability Geometric properties Weight Tolerance Value engineering

SURFACE FINISH - Mill Etched Shot blasted Anodised - Natural

Colour (organic) Colour (metallic) AA thickness Protective anodizing

Paint - Colour Electrostatic (Powder Spray

or Wet Spray) Electrophoretic (Wet Dip)

136

JOINING - Welding - TIG Filler wire MIGJ

Gas Welding Brazing Rivetingi Bearing strength Bolting I Choice of fastening material

Screwing - Screw material and size Pull out strengths

Corner crimping Adhesives - Type

Strength Application details

FABRICATION - Bending - Alloy and temper Tooling Twisting Necking Springback

Machir;ing - Routing Drilling Sawing

TEMPERATURE - Expansion/Contraction Effect on mechanical properties

CONDUCTIVITY - Heat transfer Electrical

DURABILITY - Atmospheric - Environment - Rural Marine Industrial

Chemical - Substance Concentration Temperature

Compatibility - Design of Bi-metallic connections

FIRE - Melting point Non-combusibility Non-ignitability Fire propogation Surface spread of flame Structural resistance

137



APPENDIX 2- BEAM STRESS AND DEFLECTION TABLES

139

Type of Beam

Stresses

General Formula for Stress at any Point

Stresses at Critical Points

Case 1.- Supported at Both Ends, Uniform Load

TOTAL LOAD W

fjfjjfijf4 2 2

s=-

Stress at centre, - If cross-section is

constant, this is the maximum stress.

Case 2.- SupportedatBoth Ends, Load at Center

2 2

Betweeneachsupport and load,

2Z S = -

Stress at centre, - If cross-section is


Case 3.- Supported at Both Ends, Load at any Point

I I ab1

For segment of length a,

5=-x ZI

For segment of length b,

Way S —-

- wa Stress at load

If cross-section is constant, this is the maximum stress.

Case 4.- Supported at Both Ends, Two Symmetrical Loads

w w TId w w

Between each support and adjacent load,

s = -- z Between loads,

z

Stress at each load, andatallpointsbetween,

Wa

140

Deflections

General Formula for Deflection at any Point Deflections at Critical Points

W(I-) '12÷x(I-x)J 24E11

Maximum deflection, at centre,

—— V3 384 El

Between each support and load,

(312-4x2) 4BEl Maximumdeflection,atload, WI3 4E7


(I2--b) — 6E11


Way y= (12-v2-a2)

Deflection at load, Wa 2b2 3E II

Let a be the length of the shorter segment and b of the longer one. The maximum deflection is in the longer segment, at

v = bv'jj = v1, and is

Between each support and adjacent load,

f3a (I - a) - x 2) = 6E I

Between loads,

Wa " 6E1 (3v(I-v)-a21

Maximum deflection at centre,

Wa '312-4a2)

Deflection at loads (3/- 4a)

141

Type of Beam

Stresses



Case 5.- Both Ends Overhanging Supports Unsymmetrically,

UniformLoad

TOTAL LOADW

2(/-d-c) w ÷d-c) 2!

Foroverhanging end of

length c,

w s— X(c-u)2

Between supports,

C2Lx L2ZL

÷d2X(!X)} Foroverhangingendof

lengthd,

W S= 2ZL

Stress at support next end of length c,

Wc2 2ZL

Critical stress between

supports is at /2÷ c2- d2

X 2/ =1 andis (C2- 2)

2ZL X7

Stress at support next endoflengthd,

Ld2 2ZL

If cross-section is constant, the greatest of these three is the maximum stress.

If x,>' the stress is zero at points .f 2 - c2 on both sides of x = Xr

Case 6..- Both Ends Overhanging Supports, Load at any Point

Between

ba I

(a+b=I)

Between supports: For segment of length

a, s=_x

ZI


Way S7f Beyond supports s=o.

Stress at load,

Wa!) 7i If cross-section is


142

Deflection at end c,

24E1L (21(d2÷ 2c2)÷3c3-13J

Deflection at end d,

24E1L (21(c2÷ 2d2)÷3d3-131

This case is so complicated that convenient

general expressions for the critical deflections between supports cannot be obtained.

General Formula for Deflection at any Point

Defiections

Deflections at Critical Points

For overhanging end of length c,

Wv 24E1L (21(d2÷ 2c2)

i-6c2u-u2(4c-u)-13J

Between supports,

Wx (I - x) I' 24E1L x(I-9+I2--2(d2÷c2)

- fd÷ c2(Ix)J}

For overhanging end of length d,

)24EILt2+2c) ÷6d2w-w2(4d-w)-13J

Between supports, same as Case 3. For overhanging end of length c,

Wabu y=

For overhanging end of length d,

WaLw y = - (1÷ a)

Between supports, same as Case 3.

Deflection at end c, Wabc

Deflection at end d,

(I + a) 6E II

143

Type of Beam

Stresses



Case 7.- Both Ends Overhanging Supports, Single Overhanging

Load

Between load and adjacent support,

W(c U) -

Between supports, Wc S = - (I - x)

Between unloaded end and adjacent support, s = 0.

Stress at support adjacent to load,

WC z


Stress is zero at other support.

Case 8.- Both Ends Overhanging Supports, Symmetrical Overhanging

Loads

w w

W W

Between each load and adjacent support,

W s= --(c-u)

Between supports

S = - Wc

Stress at supports and at all points between,

Wc 1

constant, this is the If cross-section is

maximum stress.

Case 9.- Fixed at One End, Uniform Load

TOTAL LOAD W

W thi-2 Stress at support,

WI -- If cross-section is


144

Deflections


Between load and adjacent support,

Wu (3cu-u2÷2c!) all

Between supports,

Wcx Y= —y (I-x)(2I-x)

Betweenunloadedendandadjacentsupport, Wc/w y=

Deflection at load, !.1 (a + I) 3E I

Maximum upward deflection is at

Wc12 x=042265 I, and 5 15.55E1

WcId Deflection at unloaded end,

Between each load and adjacent support,

= (3c (I + U) - u 2]

(I-x) Between supports,y 2E1

Deflections at loads, -W- (2c + 3/) 6E I Deflection at center, — Wa!2 7

The above expressions involve the usual approximations of the theory of flexure, and hold only for small deflections. Exact expressions for deflections of any magnitude are as follows:

Between supports the curve is a circle of radius r =E y = V'r2 1/412 /2 (l/2 I- x)2 __________ Wc

Deflection at centre, /r 2 - / 2 -

y = -'--—f2! + (2!- x) 2] 24E1! Maximum deflection, at end, WI3

8E1

145

146

wI

Type of Beam

Stresses



Case 10. - Fixed at One End, Load at Other

wI( w W s= -y (i-x)

Stress at support,


Case 11. - Fixed at One End, Intermediate Load

Between support and load,

W S = Z

Beyond load, s = o.

Stress at support,


Case 12. - Fixed at One End, Supported at the Other, Uniform Load

TOTAL LOAD W

5

S1)r/4Ix) 2Z1

Maximum stress at wi

point of fixture,y Stress is zero at

=V4L Greatest negative

stress isatx=6/.Iand 9 WI r

Deflections


y (3!- x) Maximum deflection, at end,


Y= - (31-x)

Between unloaded end and adjacent support,

y = (3v -I)

WI3 Deflections at load,

Maximum deflection, at end,

WI2 (2! ÷ 3b)

W2 (I - x) = 48E (31- 2x)

Maximum deflection is at x = 05785 I,

and is Y?I_ 185E I

Deflection at center, 192E I

Deflection at point of greatest negative

stress, atX= — us WI3 8 187E1

147

148

w

Type of Beam

Stresses



Case 13. - Fixed at One End, Supported at the Other, Load at Center

I 16

Between point of fixture and load,

w s= -(3I- lix) Between support and

load,

5 Wv s=_T Z

Maximum stress at

point of fixture, 3 14'!

16 Z Stress is zero at

3 x = - I Greatest negative

stress at center, 5 Wi 32Z

Case 14. - Fixed at One End, Supported at the Other, Load at

any Point m_—(I÷a)(I+b)+a/

n=aI(I÷b)

Wab(/÷b) 2/2

a2 wa2(31-a) w[i--(sI-a)] 2I


Wb s= 2(n-mx) Between support and

load,

-Wa 2v s = 2(3I a)

Greatest positive stress, at point of fixture,

V.P(J÷) /2 Greatest negative

stress, at load, Wa2b (3!- a) 2Z13

If a <0.5858 I, the first is the maximum stress. If a = 0.5858!, the two are equal and are

5.83Z If a 0.5858 I, the

second is the maximum stress. n

Stress is zero atX = Case 15. - Fixed at Both Ends,

Uniform Load

TOTAL LOAD W

2 2

Will x x 21 s=

Maximum stress at ends, WI

Stress is zero at x=0-78871 and at x=O.2li31

Greatest flegative wi stress, at centre, -

Deflections



W2 = 96E (9!- lix)


Wv 96E1 (312-5v2)

Maximum deflection is at v=0.4472 I, and is WI3

107.33E I

Deflection at load, i_ !tV 768 El


Wx2b 12E1/3 (3n-mx)


Wa 2v 12E1/3 1312b-v2(3!-a)J

Deflection at load, Wa3b2 (3! + b) 12E113

If a < 0.5858 1, maximum deflection is between load and support, at

v=!/andis 6E1 21÷b

If a = 0.58581, maximum deflection is at load and is WI3

1Oi.9E I If a >0.5858!, maximum deflection is between

load and point of fixture, at

2n Wbn3 and '53EIm2I3

Wx2 (/-x)2 24E1!

Maximum deflection, at centre,

— 384E1

149

Type of Beam

Stresses



Case 16.- Fixed at Both Ends, Load at any Point

Wab2 Wab /2

Tb2(/2) Wa2(/2;f fT


s= 3(aI-x(I÷2a)] Forsegmentof length

b,

S 32(bI - V (I + 2b)j

Stress at end next segmentof length a,

Wab2 r2

Stress at end next segment of length b,

Wa2b Z12

Maximum stress is at end next shorter segment.

Stress is zero for

a! = I÷2b

Greatest negative stress, at load

2Wa2b2 ---p-

Case 17. - Continuous Beam,with Two Equal Spans, Equal Loads

at Center of Each TOTAL LOAD ON EACH SPAN,W J'I-j) (I/i) -

2Z!

Maximum stress at point A, WI -

Stress is zero at x=4I

Greatest negative stress isatx=5/5! and

is,_ 9 WI -- Case 18. - Continuous Beam,with

Two Equal Spans, Equal Loads at Center of Each

w

-_____ Between point A and

load, w s= j-(3I-llx)

Between point B and load,

5 Wv 5iT

Maximum stress at

point A, 3 WI 16 Z

Stress is zero at 3

X

Greatest negative stress at center of span

5 WI ----r

150

Deflections



2b2 (2a(I-x)÷I(a-x)]


Wv2a2 = 6E J/3 (2b (I - v) + I(b - v)J

Deflection at load, Wa

Let b be the length of the longer segment and aoftheshorterone.

The maximum deflection is in the longer segment, at

2N V1 and is

2Wa2b3 3E I (I ÷ 2b)2

— Wv2(I-) '3/ 2 - 48E II - Xi

Maximum deflection is at x = 0.5785!, and is

WI3 185E1

Deflectionatcenterof span, WI3 192E I

Deflection at point of greatest negative

stress, atx £ I is WI3 8 187E1

Between point A and load,

W y= -j.(9I-11x) Between point Band load,

wv = 9J(3I 2-5v2)

Maximum deflection is at v= 0.4472!, and is WI3

107.33E1

Deflection at load, L !! 768 El

151



APPENDIX 3- PREVIOUS BS DESIGNATIONS

153

PREVIOUS B.S. DESIGNATIONS (PROPERTIES IN IMPERIAL UNITS)

OLD B.S.

NUMBER

NEW B.S.

NUMBER TEMPER

OLD NEW

0.2 % PROOF STRESS

TONS/IN2

ULT. STRESS

TONS/IN2

% ELONG ON

50 MM

HE9 M F 6.5 12

HE9 -

6063 TB T4 4.5 8.5 14

HE9 TE T5 7.1 9.7 7

HE9 IF T6 10.4 12.0 7

HE3O 1 M F 7.5 12

HE3O 6082 TB 14 7.8 12.4 14

HE3O TF 16 16.5 19.1 7

E91E 6101A TF T6 11.3 13.3 8

BTRE6 6463 TF T6 10.4 12.0 9

HE15 2014A TB 14 15.3 24.7 10

HE15 TF T6 24.7 29 6

6063A TB T4 6.0 10.0 12

6063A TE 15 10.4 13.3 7

6063A IF 16 12.6 15.3 7

These designations and properties are for guidance only. All orders are manufactured to the existing British Standards alloy numbers and tested in metric units.

154


APPENDIX 4- COMPARISON OF NATIONAL SPECIFICA11ONS

155


01

BS

and

In

tern

atio

nal

Allo

y T

ype

as D

epic

ted

by O

ld IS

O N

umbe

r F

orm

ar BS

D

esig

natio

n F

ranc

a F

orm

er N

F

Wan

t Ger

man

y

Italy

S

wed

en

Sw

itcer

land

U

SS

R

Inte

rnat

iona

l Num

ber

Wer

ksto

tt Num

ber

DIN

Des

igna

tion

1OS

OA

A

199-

S

lB

A5

3.02

55

A19

9 5

1440

07

A19

9,5

1050

5

1080

A

A19

9-5

IA

AS

14

4004

10

80A

1199

1

A99

11

99

1200

A

199

1C

A4

3.02

05

Al9

9 U

N13

567

1440

10

A19

9.0

1200

1350

1E

A

5/L

3.02

57

E-A

l E

-Al9

9,S

13

50

2011

A

l Cu

6 D

i Fb

EC

1 A

-U 5

Pb

Bi

3.16

55

Al C

u S

i Pb

UN

1636

2 14

4355

A

l Cu

6 B

i P

b 20

11

2014

A

Al C

u 4 S

i Mg

H15

A

-U4S

G

3,12

55

Al C

u S

i Mn

UN

13S

O1

1443

38

Al C

u 45

1 M

n A

K8

2014

5

2017

A

2017

5 A

ICu

4Mg

Si

A-U

4G

3.13

25

AlC

u Mgi

.

2024

A

l Cu

4Mg

1 2L

97,

2L 9

8, L

109

, Li 1

0 D

TO

510

0A

A-U

4GI

3,13

55

Al C

u M

g2

LJN

1358

3 A

l Cu

4Mg

1.5

1316

20

24

2031

—

H

12

A-U

2N

2031

2117

A

l C

u 2

Mg

3L86

A

-U 2

0 3.

1305

A

l Cu

Mg

0.5

UN

1357

7 13

18

2117

2218

7L

25

2218

2618

5 H

16

A-U

2GN

A

K4-

1 26

185

3103

A

l Mn

1 N

3 3,

0515

A

l M

n U

N13

568

1440

54

Al M

n 31

03

3105

N

31

3.05

05

Al M

n 0.

5 M

g 0,

5 31

05

4043

N

21

A-S

5

4043

4047

14

2 A

-S 1

2 45

47

5005

A

l Mg

1 14

41.

A-C

0.6

U

N15

764

1441

06

Al M

gi

5005

5056

5 51

Mg

5 N

6 3.

3555

A

l Mg

5 U

14l1

3576

50

585

5083

50

83

Al M

g 4.

5 M

n N

8 A

-C 4

.5 M

C

3354

7 A

l M

g 4.

5 M

n U

N17

790

1441

40

Al M

g 5

5154

A

145

UN

1357

5 A

MG

3 51

54A

5251

A

l Mg 2

N4

A-G

2 M

3.

3525

A

l M

g 2

Mn

0.3

Al M

g 2

0201

5454

A

l Mg

3.6

1451

—

A

-G 2

,5 M

C

3.35

37

Al

Mg 21

Mn

UN

1778

9 A

l M

g 2.

7 M

n 54

54

5554

14

52

5554

5556

5

6061

N61

55

565

AIM

5IS

1Cu

H20

A

-CS

UC

U

N16

170

AD

3 60

61

6063

A

l Mg

0.5

Si

H9

UN

1356

9 14

4104

A

D3I

60

63

6082

A

ISi I

Mg

Mn

H30

A

-S G

M0.

7 3.

2315

A

l Mg

Si

1 U

N13

571

1442

12

Al

Mg S

il M

n 60

82

6101

A

916

Al M

g S

i 0.

5 61

01A

6463

E

6 64

63

7010

D

TD

0I3O

:512

0A

7010

7014

D

TD

502

5: 5

104A

: 509

45

—

7014

7020

A

l Zn

4.5

Mg

Hi7

A

-Z 5

G

3.43

35

Al Z

n M

gi

UN

1779

1 A

l Z

n 45

Mg

1

—

7020

7075

A

l Zn

6Mg

Cu

2L95

; L16

0;L1

61;

L162

A

-Z 5

G U

3.

4365

A

l Zn

Mg

Cu

1.5

UN

1373

5 G

rang

es

SM

695

8 A

l Z

n 6M

g C

u 1

5 V

95

7075



APPENDIX 5- CHEMICAL COMPOSITION LIMITS AND MECHANICAL PROPERTIES

159


Che

mic

al c

ompo

sitio

n lim

its

'1 a

nd m

echa

nica

l pr

oper

ties

°1 o

f he

at-t

reat

able

Alu

min

ium

al

loy

bars

, ex

trud

ed r

ound

tub

e an

d se

ctio

ns

(Fig

ures

in p

aren

thes

es re

fer t

o th

e no

tes

at th

e en

d of

this

tab

le)

____

____

Mat

eria

l de

sign

atio

n S

mlio

on

iron

Cop

pe

Man

gane

se

Mag

nesi

um

Chr

omiu

m

Nic

kel

Zin

c O

ther

re

stric

tions

T

itani

um

—

Eac

h T

otal

Alu

min

ium

(bar

) or

th

ickn

ess

(tub

e!

sect

ion)

—

— pr

oof

stre

ss

(mm

.)

stre

ngth

Mm

. M

ax,

On

On

5.65

'JS

o (r

rrin

.(

50 m

m

(mn.

)

6060

%

0.30

- 06

0

%

0.10

- 03

0

¾

0.10

¾

0.10

%

0.35

- 0.

60

¾

0.05

¾

-

%

0_is

¾

¾

0_to

¾

005

¾

0.15

¾

Ren

t. T

4 T

5 T

6

mm

- -

mm

150

150

150

N/m

m'

60

100

150

N/m

m'

120

145

190

N/m

m'

- - -

%

16

8 8

¾

- - -

6061

0,40-

080

0.70

0.15-

0.40

0.15

0.80-

120

0.04-

035

-

0.25

- 0.15

0.05

0.15

Rem.

T4

T6

T65i0

- -

150

iSO

itS

240

190

280

- -

16

8

14

7

6063

0.20-

0.60

0.35

0_to

0.10

0.

45-

0.90

0.

10

- 0_

ia

- 0.

10

0.05

0.

15

Ren

t. 0 F

T4

5

T5

T6

I

l,

- - 150

- - iSO

200

200

150

200 25

15

0 20

5

. - 70

70

110

160

130

- (100

) 13

0 12

0 15

0 19

5 15

0

140

- - - - - -

15

(13)

16

13

8

8

6

13

(12)

14

- 7 7 -

6063

A

0.30-

060

0.15-

035

atO

075

0,50-

090

005

-

015

' 0.

10

0,05

0.

15

Ren

t T

4 T

5 T

6

- - -

25

25

25

90

160

190

150

200

230

- - -

14

8 8

12

7 7

6082

0.

70-

130

0.50

0.

10

0.40

- 1.

00

0.60

- 1.

20

025

- 0.

20

- 0.

15

0.05

0.

15

Rem

. 0 F

T

4

T5

T6

T65

t0

- - - 150

- - 20

150

205

200

150

200 6 20

ISO

200

' - 120

100

230

255

270

240

- (100

) 19

0 17

0 27

0 29

5 31

0 28

0

170

- - - - - - -

16

(13)

16

13

8 8 S

14

(12)

14

- 8 7 - -

6101A

030-

070

0.40

0.05

- 0,40-

090

-

-

-

. -

0.03

0.10

Rem.

T6

- .

170

200

- 10

8

6463

0,20-

060

0.15

0.20

005

0.45-

0.90

- -

005

-

-

0.05

0,15

Rent.

T4

T6

- - 50

50 78

150

125

185

- - 16

tO

14

9

20i4A

0.50-

0.90

0,50

3.90-

5 00

0.40-

1.20

0.20-

0.60

0.10

0.10

0,25

0.20

Zr e

Ti

0.15

0.05

0,15

Rem.

T4

T6

T65i0

- 20

75

150

- 20

7S

150

20

75

150

200

20

75

150

200

230

250

250

230

370

435

420

390

370

390

390

370

435

480

465

435

- - - - - - - - -— ii ii 8 8 7 7 7 7

10

- - - 6 - - -

7020

0.35

0.40

0.20

0.05-

0.50

1.00-

1.40

0,10-

0.35

- 4.00-

5.00

008-0.25

Zr

Ti

- 0.05

0.15

Rent

T4

T6

- -

25

25

190

280

300

340

- 12

10

10

8

( IN

DIV

IDU

AL PERCENTAGE VALUES OF CONSTITUANTS ARE M

AX

IMU

M

(2) ALL MECHANICAL PROPERTIES ARE TYPICAL.

(3) TEMPER T6510 APPLIES ONLY TO CONTROLLED STRETCHING OF SO

LID BARS

a)


Aluminium extrusions are used in a wide variety of engineering

and architectural applications. As a strong, light, non-corrosive

material which can be extruded into complex shapes, aluminium

provides the solution to a whole range of design problems.

This concise technical guide provides the reader with the

information necessary to design effectively with aluminium

extrusions. It presents brief details on the extrusion process,

outlines aluminium's material specifications and mechanical

properties and covers such design considerations as conductivity,

temperature, fabrication and finishing. The book also contains

specific guidance on design procedure, including worked

examples, and concludes with an extensive glossary.

"It's a true working manual...a must for every

drawing office which uses or might use

aluminium extrusions"

Chris Rand, Industrial Technology magazine

"A valuable document...four star rating out of

fve" Andy Pye, Design Engineering magazine

"A much needed source of reference"

Roy Woodwarci, Aluminium Industry magazine

Published by The Shapemakers — the information arm of the UK

Aluminium Exfruders Association

Aluminium

Documents

Aluminium Extrusions - Technical Design Guide