aluminiumwelding_42_0410_0590_200

Course Book

42,0410,0590 012003

Aluminium-Welding GB

TECHNOLOGY CENTRE 3

TABLE OF CONTENTS

Introduction 4

Materials 8

Cracking tendency 13

Easy identification of alloys “in situ” 18

Filler metals for aluminium welding 25

Processes 32

Special features of welding aluminium wires 36

Ignition comparison 39

SynchroPuls 41

Gases 43

Weld-seam preparation 46

Weld defects and cracking sensitivity 49

Applications in the automobile industry 55

Machine settings, program table 57

Except where expressly permitted, it is prohibited to pass on or duplicate this documentation or to

commercially exploit or communicate its contents.

Any infringement hereof shall render the infringing party liable to the payment of damages. Text

and illustrations technically correct at the time of going to print.

TECHNOLOGY CENTRE 4

INTRODUCTION

Discovered from H. Davy 1808. Aluminium has been in use as a light alloy since 1880. It is

produced by electrolysis of aluminium oxide obtained from bauxite.

Areas of use

Utilisation of aluminium and its alloys instead of steel materials is becoming more and more

widespread. Aluminium is thus now found in fields such as:

• Aerospace

• Automotive industry (commercial and passenger vehicles)

• Shipbuilding

• Rail vehicle construction as well as in classical structural-steel fields such

as:

• Hall construction

• Shelving construction

• Conservatories

• Windows etc.

•

Energy demand: ~1950 21KW/h for 1 kg Al

~1990 13KW/h for 1 kg Al

Why ? Always 3 electrodes necessary (in comparison Mg = only one)

Compared with iron, aluminium has the following characteristic differences:

Properties Al Fe

Atomic weight (g/Mol) 26.98 55.84 Crystal lattice Cubic face-centred Cubic body-centred Density (g/cm³) 2.70 7.87 Modulus of elasticity (Mpa) 67 . 103 210 . 103 Coefficient of expansion (1/K) 24 . 10-6 12 . 10-6 Rp0,2 (Mpa) ~10 ~100 Rm (Mpa) ~50 ~200 Specific heat (J/kg.K) ~890 ~460 Fusion heat (J/g) ~390 ~272 Fusion temperature (°C) 660 1536 Thermal conductivity (W/m.K) 235 75 Electrical conductivity (m/Ω.mm²) 38 ~10 Oxides Al2O3 FeO / Fe2O3 / Fe3O4 Fusion temperature (°C) 2050 1400 / 1455 / 1600

TECHNOLOGY CENTRE 5

Advantages of aluminium over steel

• Lower unit-weight (ρ = 2.7 g/cm³), yet great strength (up to 450 N/mm²

possible, Al 99.5 up 65N/mm² to 80 N/mm², depends on the cold-roll

strength,

AlMg 3 ~ 200 N/mm²)

• Resistant to climatic influences

• Good toughness at sub-zero temperatures

• Good-to-very-good suitability for the production of continuous-cast profiles

The most important alloying constituents of aluminium are:

• Magnesium Mg: 0.3 – 7 %, higher strength, finer granulation

• Manganese Mn: 0.3 – 1.2 %, better corrosion resistance (salt water), higher

strength

• Copper Cu: ~ 5 %, higher strength, less corrosion resistance, important for

hardenability

• Silicon Si: 12 %, lowers the melting point down to 577 °C, but the resultant metal

structure is coarse-grained

Coarse grain: - has the lowest shrinkage dimension,

- and thus less propensity to cracking, because

- coarse grain leads to

- fewer grain boundaries

- few impediments to the slip planes

- low strength, high ductility

Fine grain: - many grain boundaries

- many impediments to the slip planes

- increase in strength

- risk of micro-cracking

TECHNOLOGY CENTRE 6

TYPES OF ALUMINIUM

Electricity industry Al 99.5 1...

• Wires for power lines

• Wires for transformers

• Cooling fins

Jewellery industry

• Decorative items

• Motor-car trims

Aircraft industry AlCu 2...

AlMn 3…

Castings AlSi 4...

• Gearbox casings

• Engine blocks*

• Cylinder heads*

• Aluminium wheel rims for cars

* with bismuth and lead, due to the short length of the

shavings created during machining

Metal sheets, tubes AlMg 5...

• Tank construction, shipbuilding

• Dumper truck tipping buckets, apparatus

• Drink can

TECHNOLOGY CENTRE 7

Profiles AlMgSi 6...

• Supporting structure

• Windows, doors, fittings

• Vehicle superstructures

Military industry AlZn 7…

• Pioneer bridge

• Armor trough

• Aeronautical

TECHNOLOGY CENTRE 8

MATERIALS

Categorisation

Non-age-hardenable wrought alloys Age-hardenable wrought alloys

Wrought alloys

A L U

Casting alloys

AlMnMg

AlMgMn

AlMn

AlMg

AlMgSi

AlZnMg

AlCuMg

AlZnMgCu

AlCuMg Li*

G-AlSi

G-AlMg

G-AlMgSi

G-AlCuTi

G-AlSiMg

Sheets Profiles

Good corrosion

characteristic

Without filler

metal weldable

Bad corrosion

characteristic

With filler metal

weldable

TECHNOLOGY CENTRE 9

Möglichkeiten zur Verfestigung von Aluminium

1. Rolling

Methods for work-hardening aluminium

Hard with no further after-treatment

Medium-soft is back-annealed after the hard-rolling process

Soft is back-annealed for rather longer after the hard-rolling process

2. Distortion of the lattice structure by impurity metals

e.g. Li = lithium, which causes strain distortion high strength, but low ductility (is used

in aerospace engineering)

3. Other impediments include precipitation at the grain boundaries.

This also increases the strength. Impurity atoms diffuse at the grain boundaries.

TECHNOLOGY CENTRE 10

Functional principle of age-hardening Al alloys

Artificial ageing will also depend upon the size of the weldment.

Railway wagons are naturally aged. Why? They wouldn’t fit in a hardening furnace!


Age-hardenable wrought alloys

Aluminium alloys with magnesium and silicon, zinc or copper (e.g. AlMgSi 1, AlZn 4.5 Mg1

etc.) can be hardened to around 450 N/mm² by means of thermal treatment.

These materials are hardened by annealing (solution-annealing), then quenched and aged.

This leads to a strength-enhancing precipitation of the alloying elements in the aluminium

microstructure. Ageing can either be performed at room temperature over the course of

several days (natural ageing) or at temperatures of between 80°C and 160°C (artificial ageing)

in a short period, e.g. 60 h at 60 °C / 24 h at 120 °C. Artificial ageing will also depend upon

the size of the weldment. Railway wagons are naturally aged. Why? They wouldn’t fit in a

hardening furnace!

As a result of welding, hardened aluminium alloys lose their hardness in the heat-

affected zone. The greater the thermal input during welding, the more the heat of welding will

reverse the original hardening. Subsequent heat-treatment can give them back their original

strength values. The alloy AlZn 4.5 Mg1 is worth mentioning here - this alloy can be restored

to its original strength values after welding simply by being naturally aged.

⇒ Practical tip: Age-hardenable wrought alloys are most often used in cases where a steel

construction is to be replaced by one made of aluminium. Multiplying by 1.4 is usual.

Nevertheless, weight savings of 40% are possible.

Non-age-hardenable wrought alloys

Non-age-hardenable aluminium materials do not harden following heat treatment. They derive

their higher strength (as against pure aluminium) from solid-solution strengthening. By

alloying with magnesium and manganese, it is possible to increase the tensile strength to

around 280N/mm².

e.g. AlMg1/ AlMg3/ AlMg 4.5 Mn.

⇒ Practical tip: These are used where corrosion resistance is required (e.g. sea-water

resistance). For sheets, vehicle construction, chequered sheets.


Aluminium casting materials

Aluminium casting materials are obtained by additional alloying of the aluminium with silicon.

As a rule, only repair welding jobs are carried out with these casting alloys (electric arc

welding with special rod electrodes, TIG or MIG shielding gas welding). These repair welding

jobs are performed using filler metals of the same composition as the base metal, especially

where the weld must not have any characteristics that differ from the cast grain structure.

Welding filler metals for these alloys must not have a high hydrogen content. After polishing,

the colour of the weld is the same as that of the base metal. In general, the weld seam will

have a slightly different coloration after anodic oxidation (anodisation). This is particularly

noticeable in the case of Si filler materials (becomes grey, due to the superior conductivity of

AlSi).

⇒ Practical tip: Because of the low melting point, there is more rapid wetting to the

sidewalls; this in turn means a high welding speed and a clean seam appearance.


Cracking tendency of aluminium – is dependent upon the Si, Cu and Mg content

Warning: The above alloys tend to have a higher cracking tendency use a crater-fill

program!

Zirconium counteracts hot cracking.

0

1

2 3 4 5

Mg

% alloying content

Cra

ck

ing

pro

pe

nsit

y

Greatest risk of hot cracking: In the case of Mg, between 0.5 and 2.5%

In the case of Si, between 0.3 and 1.5%

Cracks

In order to prevent hot cracks, welding is usually performed with over-alloyed filler metals.

Crater cracks occur as a result of the large shrinkage dimension of aluminium. They can be

prevented by using a run-off plate or a crater-fill program (power source must be suitable for

such a program).

Clean seam preparation (deburring, degreasing) also helps to prevent cracking.


The relative cracking sensitivity of a material is influenced by the filler metal. The use of

suitable base-metal / filler-metal combinations can reduce the proneness to cracking.

Fig. 3: Relative cracking sensitivity of selected base-metal / filler-metal combinations of

wrought aluminium alloys.


Hot-cracking propensity of welded AlMg4.5Mn alloys and their behaviour when

subjected to various types of loading *)

By Z. Buray, E.Buray-Milhályi, I. Huber and M. Mórotz **)

1. Introduction

The advantageous properties of AlMg4.5Mn alloys have led to their widespread use for

welded constructions. They have proved particularly suitable for use in the construction of

aircraft and chemical plant, and as containers for the transport of LNG. Developed in Hungary

in the mid-1950’s, this alloy was first used in shipbuilding [1].

When computing the design of components, there is an increasing tendency towards

exploiting the load-bearing capacity of the material to the very full. However, this requires in-

depth knowledge of the behaviour of the material when subjected to various different types of

loading. In the case of AlMg4.5Mn, difficulties occur in that most Standards and regulations

dealing with the magnesium and manganese contents of this particular alloy allow a wide

tolerance range (4.0 % to 4.9 % Mg, 0.4 % to 1 % Mn). This may lead to unforeseeable

fluctuations in the mechanical properties, and thus to an inaccurate assessment of the load-

bearing capacity. Where this material is welded, the problem is exacerbated by the

microstructural anisotropy of the seam and the heat-affected zone [2], although for the

purposes of this paper, only the statical strength values were determined. It should thus also

be expected that the varied composition of the material will also have an influence upon its

weldability.

2. Experimental programme

It was decided to investigate the effects of the above fluctuations in the magnesium and

manganese contents of AlMg4.5Mn, with regard to:

a) the base metal (statical strength, fatigue behaviour and fracture properties)

b) the weldability (influence of the composition of the base and filler metals, the welding

process and the welding parameters on the propensity to hot cracking)

c) the welded joints (statical strength, fatigue behaviour and fracture properties)


The investigations looked at five types of alloy (Table). We report below on how the weldability

was determined, and on the behaviour of the welded joints.

Alloy Chemical composition

Mg % Mn % Cr % Fe % Si % Ti %

AlMg4Mn0,4 4,0 0,47 0,18 0,20 0,06 0,01

AlMg4Mn1,0 3,95 0,99 0,18 0,19 0,15 0,03

AlMg4,9Mn0,4 4,9 0,42 0,19 0,18 0,11 0,02

AlMg4,9Mn1,0 4,85 1,0 0,19 0,21 0,17 0,02

AlMg4,7Mn0,7 4,65 0,65 0,20 0,23 0,16 0,02

SG-AlMg3 3,5 0,46 0,03 0,34 0,11 0,02

SG-AlMg4,5Mn 5,2 0,82 0,10 0,16 0,07 0,09

SG-AlMg5 5,1 0,31 0,17 0,42 0,14 0,08

3. Determining the weldability

3.1. Test procedure

The propensity to hot-cracking was determined in the “Fish-skeleton test”. This is performed

using a self-loading specimen with a stiffness that changes (i.e. decreases) in the longitudinal

direction of the seam. The shrinkage restraint perpendicular to the seam is large at the

beginning of welding, and decreases continuously towards the end of the weld-seam. The

crack length is thus a function of the stiffness of the specimen. The crack sensitivity A1 is

computed by the equation A1 = (measured crack length / weld-seam length) x 100 %. In

order to determine the crack sensitivity of the base metal, the specimens are TIG-welded with

no filler metal. In contrast, TIG and MIG weld-seams are tested using filler metal. The

specimens were 6 mm thick. In the case of TIG-welding with filler metal, a U-shaped groove

was prepared. The welding parameters are given in next table .

Schematic diagram of the “Fish-skeleton test”

Test specimen

Apron plate


Weld process Weld filler metal Ø

mm

Welding parameters 1)

Welding amperage A

Welding voltage

V

Welding speed m/min

“Fish-skeleton test”

Tungsten inert gas welding Tungsten inert gas welding Metal inert gas welding

- SG-AlMg5 SG-AlMg5

- 2.4 1.2

340...3452) 330...3402) 160...165

15...18 15...18 24...25

0.25 0.25 0.25

Butt-seam

Metal inert gas welding Metal inert gas welding Metal inert gas welding

SG-AlMg3 SG-AlMg3 SG-AlMg4,5Mn SG-AlMg4,5Mn SG-AlMg5 SG-AlMg5

1.6 1.6 1.6 1.6 1.6 1.6

2753) 3003) 2703) 2903) 2603) 2753)

26.33) 26.43) 25.83) 26.03) 24.83) 25.03)

0.4 0.8 0.4 0.8 0.4 0.8

1) Nozzle Ø 16 mm, argon flow-rate 16 l/min. 2) Ø of thorium-oxide-containing tungsten electrode 6.3 mm 3) Average values

Pure aluminium

This has high corrosion resistance, but low tensile strength (approx. 80 N/mm²), which can

be increased to around 130 N/mm² by cold-working. In the weld-seam zone, however, the

effects of this strain hardening are lost during welding.

e.g. pure aluminium Al 99.9 / Al 99.5

⇒ Practical tip: Best attainable seam appearance, but lowest strength.


EASY IDENTIFICATION OF ALLOYS “IN SITU”

When mixed with water, non-metallic oxides form acids, while metallic oxides form bases. The

aqueous solutions of metallic hydroxides are known as “lyes” or “caustic solutions”.

Example:

Sulphur trioxide SO3 and water react to form a colourless liquid – sulphuric acid H2SO4:

SO3 + H2O H2SO4

Example:

Dissolved in water, solid white sodium oxide becomes sodium hydroxide (caustic soda

solution):

Na2O + H2O 2NaOH

Caustic solution test

(Separation of the alloy with copper, zinc, nickel and silicon)

e.g. test solution 1:

Caustic soda solution 25% (sodium hydroxide + water; Na2O + H2O 2NaOH.

Let one drop of the sample solution act upon the bright surface of the test specimen for 3 to

5 minutes, then wash it off with water and absorb the drops with filter paper.

Test solution 1 helps in determining the alloying constituents of AlSi. There are 9 different test

solutions, 1 for each of the various alloying compositions.


Al, AlMn, AlMg = no discoloration

Pure aluminium and alloys with magnesium and manganese remain

bright, the difference can only be seen from the surface hardness (e.g.

scratch test with a marking tool, Brinell hardness test). If there is no

reaction, this means that the metal in question is not an Al alloy, but

pure magnesium.

G-AlMg Si = mixture of AlMg + Si = light grey

AlCuMg, AlZnMg = black, can be wiped off

If the alloy contains copper, zinc or nickel, then a black mark is left

behind.

G-AlSi = grey, cannot be wiped off

Where the alloy has a silicon content of over 3%, and none of the

above-mentioned heavy metals, a grey mark is left behind.

The most reliable method is always a spectroscopic analysis (drilling chips are sufficient). In

Austria, this can be performed by e.g. the Rübig company in A-4614 Marchtrenk.


Alloy designations

Numerical Alphanumerical

(DIN EN 573 T1) (DIN EN 573 TZ)

EN AW-5456A EN AW-AlMg5Mn1(A)

1 2 3 4 1 2 5 6 7 6 4

1 Standardised abbreviation

2 Base metal + form in which supplied: AW = Al wrought alloy AC = Al casting alloy

3 1st digit: series designation

2nd digit: alloy modification minimum part f.e. 1050 = 99,50

1000 + 50

4 National variant

5 Main alloying component

6 Nominal contents

7 Further alloying element

The numerical system consists of 4 digits and corresponds to the designation registered by

the Aluminium Association, USA, giving information on the main alloying element.

Alloy groups – numerical system

1000 series Al ≥99.0% Naturally hard

2000 series Main alloying element = Cu Age-hardenable

3000 series Main alloying element = Mn Naturally hard

4000 series Main alloying element = Si Naturally hard

5000 series Main alloying element = Mg Naturally hard

6000 series Main alloying element = Mg+Si Age-hardenable

7000 series Main alloying element = Zn Age-hardenable

8000 series Main alloying element = other elements f.e. Lithium


An aluminium material is completely defined by its alloy designation and temper designation.

The latter comes after the alloy designation, from which it is separated by a hyphen.

F As fabricated

O Annealed

H Strain hardened

H1x Only strain hardened, without any additional thermal treatment

H2x Strain hardened and re-cooled; slightly improved reformability

H3x Strain hardened and stabilised

H4x Strain hardened and stove-lacquered or painted

The temper designations for age-hardenable alloys are listed below:

T1 Cooled from an elevated temperature shaping process and naturally aged to a

substantially stable condition

T2 Cooled from an elevated temperature shaping process, cold worked and naturally

aged to a substantially stable condition

T3 Solution heat-treated, cold worked and naturally aged to a substantially stable

condition

T4 Solution heat-treated and naturally aged to a substantially stable condition

T5 Cooled from an elevated temperature shaping process and then artificially aged

T6 Solution heat-treated and then artificially aged

T7 Solution heat-treated and over-aged stabilised

T8 Solution heat-treated, cold worked and then artificially aged

T9 Solution heat-treated, artificially aged and then cold worked

T10 Warm worked, solution heat-treated, cold worked, artificially aged

Tx51 Stress relieved by stretching

Tx52 Stress relieved by compressing

Legend: shaping process solution heat-treated

cold worked cold cured

stabilised warm cured

temp.

time


Overview of comparable material designations under various systems. (Composition is not

always exactly identical).

International F GB I

DIN-symbol (to DIN 1700)

Material n°. (to DIN 17007)

Internat. 1) alloy Register

(AA)

ISO

(R 209)

Symbol to NF A02-004

Symbol to BS, BS-L, DT

D 2)

symbol (convezionale) to

UNI 3)

Al 99.98R Al 99.8 Al 99.7 Al 99.5 Al 99 AlMn AlMnCu AlMn 0.5 Mg 0.5 AlMn 1 Mg 0.5 AlMn 1 Mg 1 AlMg 1 Al Mg 1.5 Al Mg 2.5 Al Mg 3 AlMg 4.5 AlMg 5 AlMg 2 Mn 0.3 AlMg 2 Mn 0.8 AlMg 2.7 Mn AlMg 4 Mn AlMg 4.5 Mn AlMgSi 0.5 AlMgSi 0.8 4) AlMgSiCu AlMgSi 1 AlMgSiPb AlCuBiPb AlCuMgPb AlCu 2.5 Mg 0.5 AlCuMg 1 AlCuMg 2 AlCuSiMn AlZn 4.5 Mg 1 5) AlZnMgCu 0.5 AlZnMgCu 1.5

3.0385 2.0285 3.0275 3.0255 3.0205 3.0515 3.0517 3.0505 3.0525 3.0526 3.3315 3.3316 3.3524 3.3535 3.3345 3.3355 3.3525 3.3527 3.3537 3.3545 3.3547 3.3206 3.2316 3.3214 3.2315 3.0615 3.1645 3.1655 3.1305 3.1325 3.1355 3.1255 3.4335 3.4345 3.4365

(1199) 1080A 1070A 1050A 1200 3103 3003 3105 3005 3004 5005

(5050A) 5052 5754 5082

5356A 5221

5454 5086 5083 6060

(6005) 6061 6082

(6262) 2011

(2030) 2117

2017A 2024 2014 7020

(7079) 7075

Al 99.8 Al 99.7 Al 99.5 Al 99 Al-Mn 1 Al-Mn 1 Cu Al-Mg 1 Al-Mg 1.5 Al-Mg 2.5 Al-Mg 3 Al-Mg 4 Al-Mg 5 Al-Mg 2 Al-Mg 3 Mn AlMg 4.5 Mn Al-MgSi Al-Mg 1 SiCu Al-Si 1 Mg Al-Cu 2 Mg Al-Cu 4 Mg Al-Cu 4 Mg 1 Al-Cu 4 SiMg Al-Zn 6 MgCu

A-99 A-8 A-7 A-5 A-4 A-M1 A-MG0.5 A-M1 G A-G0.6 A-G1.5 5052 A-G3M A-G2M A-G2.5MC A-G3MC A-G4MC A-G4.5MC A-GS A-SG0.5 A-GSUC A-SGM0.7 A-SGPb A-U5PbBi A-U4Pb A-U2G A-U4G A-U4G1 A-U4SG A-Z5G A-Z4GU A-Z5GU

1 1A

1B 1C N3

N31

N41

N6 N4

N51 N5/6 N8 H9 H10 H20 H30

FC1

2L69 H14

2L97/98 H15

2L95/96

P-AlP 99.8 P-AlP 99.7 P-AlP 99.5 P-AlP 99.0 P-AlMn 1.2 P-AlMn 1.2 Mg P-AlMg 0.9 P-AlMg 1.5 P-AlMg 2.5 (P-AlMg 3.5) P-AlMg 4.4 P-AlMg 5 P-AlSi 0.5 Mg P-AlMg 1 SiCu P-AlMgSi P-AlSi 1 MgMn P-AlCu 5.5 PbBi P-AlCu 4 MgMn P-AlCu 4.5 MgMn P-AlCu4.4SiMnMg P-AlZn 5 Mg P-AlZn 5.8 MgCu

1) The International Alloy Register (International Registration Record) is kept at the Aluminium Association (AA) in Washington. Most Western

European countries, together with Australia and Japan, are changing over their designations for wrought materials to this system; France

already has changed over (NF A 02-104). The 4-digit designations not enclosed in brackets have an identical composition to DIN.

2) In BS, the type of wrought product is indicated by a preceding code letter in the case of pure aluminium, and in the case of alloys by a

code letter inserted between “N” (non-hardenable) or “H” (hardenable) and the number: S = sheet; E = extruded product; T = tube,

drawn; F = forgings; G = wire. Example: S1C = sheet Al 99; HE30 = extruded profile made of AlMgSi1.

3) In Italy an abbreviated mode of notation (“contressegno”) is also usual, in which the symbols for the chemical elements are reduced to

one letter: Al = A; Mn = M; Mg = G; Cu = C, Si = S; Zn = Z; Example: P-AlZn 5.8 Mg Cu is now P-A/ 5,8 GC (P- = wrought material).

4) Extruded profiles for wagons, age-hardening. If the manufacturer supplies AlMgSi 0.8 for bent components in a naturally hardened

temper, remember that at room temperature, the material will age-harden once again on its own, to a certain extent. Practical tip: Use

immediately, otherwise the material will become too stiff. N.B.: AlMgSi0.8 not standardised (only the extruded profiles are artificially aged)

5) Self-hardening in 1960’s automobile construction (according to Ing. Ruip)


Overview comparing DIN EN Standards with old DIN Standards

DIN EN 573-3 Old DIN norm Number Symbol Symbol

1098 1080A 1070A 1050A 1200 1350A

Al99,98 Al99,8(A) Al99,7 Al99,5 Al99,0 EA199,5(A)

Al99,98R* Al99,8 Al99,7 Al99,5 Al99 E-Al

2007 2011 2014 2017A 2117 2024

AlCu4PbMgMn AlCu6BiPb AlCu4SiMg AlCu4MgSi(A) AlCu2,5Mg AlCu4Mg1

AlCuMgPb AlCuBiPb AlCuSiMn AlCuMg1 AlCu2,5Mg0,5 AlCuMg2

3003 3103 3004 3005 3105 3207

AlMn1Cu AlMn1 AlMn1Mg1 AlMn1Mg0,5 AlMn0,5Mg0,5 AlMn0,6

AlMnCu AlMn1 AlMn1Mg1 AlMn1Mg0,5 AlMn0,5Mg0,5 AlMn0,6

5005A 5505 5305 5605 5110 5310 5019 5049 5051A 5251 5052 5454 5754 5082 5182 5083 5086

AlMg1(C) Al99,9Mg1 Al99,85Mg1 Al99,98Mg1 Al99,85Mg0,5 Al99,98Mg0,5 AlMg5 AlMg2Mn0,8 AlMg2(B) AlMg2 AlMg2,5 AlMg3Mn AlMg3 AlMg4,5 AlMg4,5Mn0,4 AlMg4,5Mn0,7 AlMg4

AlMg1 Al99,9Mg0,5 Al99,85Mg1 AlRMg1 Al99,85Mg0,5 AlMg0,5 AlMg5 AlMg2Mn0,8 AlMg1,8 AlMg2Mn0,3 AlMg2,5 AlMg2,7Mn AlMg3 AlMg4,5 AlMg5Mn AlMg4,5Mn AlMg4Mn

6101B 6401 6005A 6012 6060 6061 6082

EAlMgSi(B) Al99,9MgSi AlSiMg(A) AlMgSiPb AlMgSi AlMg1SiCu AlSi1MgMn

E-AlMgSi0,5 Al99,9MgSi AlMgSi0,7 AlMgSiPb AlMgSi0,5 AlMg1SiCu AlSi1MgMn

7020 7022 7072 7075

AlZn4,5Mg1 AlZn5Mg3Cu AlZn1 AlZn5,5MgCu

AlZn4,5Mg1 AlZnMgCu0,5 AlZn1 AlZnMgCu1,5

8011A AlFeSi(A) AlFeSi

*) Composition is not identical with DIN EN


DE 50 (SG-Al99,98R)* 1199 A99 - -

DE 51 SG-Al99,8 1080A A8 G1A -

DE 52 SG-Al99,5 1050A - G1B -

DE 53 SG-Al99,5Ti - - - -

DE 54 SG-AlMn1 3103 - NG3 -

DE 55

DE 57

SG-AlMg2,5Mn0,8

SG-AlMg2Mn0,8Zr

(5049) - - -

DE 56 SG-AlMg3 5754 - - -

DE 58 SG-AlMg5 5356 A-G5MC NG6 ER5356

DE 59 SG-AlSi5 4043 A-S5 NG21 ER4043

DE 60 SG-AlSi12 4047 A-S12 4047A ER4047

DE 61 SG-AlSi10Mg 4045 - -- -

DE 63

DE 64

SG-AlMg4,5Mn

SG-AlMg4,5MnZr

5183 (5556) A-G4,5MC 5183 ER5183

(ER5556)

DE 65

DE 67

SG-AlMg2,7Mn

SG-AlMg2,7MnZr

5554 - NG52 ER5554

DE 68 (SG-AlSi7Mg)* - - - -

DE 76 (L-AlSi12)* - - - -

For example basic materials

2014 AlCu4SiMg 3003 AlMn1Cu 1060 Al99,6 2036 AlCu2Mg0,5 3004 AlMn1Mg1 1100 Al99,0Cu 2219 AlCu6Mn 1350A EAl99,5(A) 5101 EAlMgSi 7005 AlZn4,5Mg1,5Mn 5005 AlMg1(B) 6005 AlSiMg 7020 AlZn4,5Mg1 5050 AlMg1,5(C) 6063 AlMg0,7Si 7021 AlZn5,5Mg1,5 5052 AlMg2,5 6201 EAlMg0,7Si 7039 AlZn4Mg3 5454 AlMg3Mn 6351 AlSiMg0,5Mn 7046/7146 AlZn7Mg1 5086 AlMg4 6061 AlMg1SiCu 5083 AlMg4,5Mn0,7 6082 AlSi1MgMn 5456A AlMg5Mn1(A) 5356 AlMg5Cr(A)

For example filler metals

2319 AlCu6Mn(A) 3003 AlMn1Cu 5554 AlMg3Mn(A) 1080A Al99,8(A) 5654 AlMg3,5Cr 4043A AlSi5(A) 1050A Al99,5 5183 AlMg4,5Mn0,7(A) 4145 AlSi10Cu 1450 Al99,5Ti 5356 AlMg5Cr(A) 4047A AlSi12(A) 5556A AlMg5Mn

Standards & datasheets: - Filler metals, DIN 1732 Part 1

- Weld-seam preparation, DIN 8552 Part 1

- MIG welding of Al; Datasheets DVS 0913 and DVS 0933


FILLER METALS FOR ALUMINIUM WELDING

DVS Datasheet 1608 lays down the strengths of the combinations, although these only apply

to artificially aged tempers.

Al99.9 S-Al99.9

Al99.8

Al99.7

Al99.5 S-Al99.5 S-Al99.5

Al99 S-Al99.5Ti S-Al99.5Ti

AlMnCu S-Al99.5Ti S-Al99.5Ti S-AlSi5

S-AlMn S-AlMn

AlMg1 S-Al99.5Ti S-Al99.5Ti S-AlMg3 S-AlMg3

AlMg1.5 S-AlMg3 S-AlMg3

AlMg1.8

AlMg2.5

AlMg3 S-Al99.5Ti S-Al99.5Ti S-AlMg3 S-AlMg3 S-AlMg3

AlMg5 S-AlMg3 S-AlMg3

AlMg2.7Mn S-AlMg3 S-AlMg3 S-AlMg3 S-AlMg3 S-AlMg3 S-AlMg3

AlMg2Mn0.3

AlMg2Mn0.8

AlMg4Mn S-AlMg3 S-AlMg3 S-AlMg5 S-AlMg5 S-AlMg5 S-AlMg5 S-AlMg4.5Mn

AlMg4.5Mn S-AlMg4.5MnS-AlMg4.5Mn S-AlMg4.5Mn

AlMg4Mn S-AlMg3 S-AlMg3 S-AlMg3 S-AlMg3 S-AlMg3 S-AlMg3 S-AlMg5 S-AlSi5

AlMg4.5Mn A-AlSi5 A-AlSi5 A-AlSi5 S-AlMg5 S-AlMg4.5Mn S-AlMg3

AlZn4.5Mg1 S-AlMg5 S-AlMg5 S-AlMg5 S-AlMg5 S-AlMg5 S-AlMg5 S-AlMg4.5Mn S-AlMg4.5Mn S-AlMg4.5Mn

S-AlMg4.5MnS-AlMg4.5Mn S-AlMg4.5Mn S-AlMg5

BASE METAL

Al99.9

Al99.8

Al99.7

Al99.5

Al99

AlMn

AlMnCu

AlMg1

AlMg1.5

AlMg1.8

AlMg2.5

AlMg3

AlMg5

AlMg2.7Mn

AlMg2Mn0.3

AlMg2Mn0.8

AlMg4Mn

AlMg4.5Mn

AlMgSi0.5

AlMgSi1.0

AlZn4.5Mg1

Overview table

Filler metal Available diameter Base materials

designation MIG TIG DIN-designation

SG - Al 99.5 DIN 1732 W.Nr. 3.0259 AWS ER 1100

0.8mm 1.0mm 1.2mm 1.6mm

2.0mm 3.0mm

Al 99.5 Al 99 Al 99.8 Al 99.7

SG - AlMg 5 DIN 1732 W.Nr. 3.3556 AWS ER 5356

0.8mm 1.0mm 1.2mm 1.6mm

2.0mm 3.0mm

AlMg 5, AlMg 3, AlMgMn, AlZnMg 1 Cast alloys with magnesium as main alloying-constituent. G-AlMg 3, G-AlMg 3 Si, G-AlMg 5, G-AlMg 5 Si, G-AlMg 10, G-AlMg 3 (Cu), AlMgSi 1

SG - AlSi 5 DIN 1732 W.Nr. 3.2245 AWS ER 4043

0.8mm 1.0mm 1.2mm 1.6mm

2.0mm 3.0mm

AlSi 5, AlMgSi 0.5; AlMgSi 0.8; AlMgSi 1 Pure aluminium and Al alloys whose main alloying constituents account for less than 2 % by weight. Al casting alloys with up to ~7% Si. With over 7%, use AlSi 12 !


Essentially, all weldable aluminium base materials can be processed with the above alloys.

When selecting the optimum filler metal for a particular application, it is important to choose

an alloy of the same type as the base metal wherever possible.

Remember that when the workpiece is given subsequent anodic treatment, you should never

use filler wires that contain silicon, as this would cause a dark discoloration of the weld-

seams!

The choice of the filler metal will depend on the type of base metal, having regard to the

mechanical and chemical stresses to be expected.

e.g. ICE base metal AlMgSi 0.7; filler metal AlMg 4.5Mn Zr

Filler metal Base metal

Al 99.5 Ti Al 99.8 Al 99.5 AlMn

AlMg 5 Al 99.5 AlMg 4.5 Mn AlMg 3 AlMg 5 AlMgSi 1 AlZn 4.5 Mg AlCuMg

AlSi 5 AlMgSi 1 AlZn 4.5 Mg AlCuMg G-AlSiMg G-AlSiCu

AlSi 12 G-AlSi 12 G-AlSiMg G-AlSiCu

Consideration should be given to the price differences obtaining between 1.0 and 1.2 mm

wire electrodes on the one hand, and 1.6 mm wires on the other. If you are working with a

high-grade pulsing power source, you can change over to the next larger diameter. Another

advantage of thicker wires is that they are easier to feed!

1.2 mm diameter wire has 44% more volume than wire of 1.0 mm diameter

• less oxidation surface and thus

• less contamination of the surface


Treatment of the wire:

• Store at room temperature

• Should be used as immediately as possible

• After you have finished welding, repack the wire in a hermetically sealed container. (Tip:

add silica gel or rice to absorb any moisture in the container)

• Protect wire from dirt and contamination

These measures will reduce hydrogen absorption (which can lead to porosity, hot cracking,

ageing, hardness) and thus increase the quality of your welding results.

Corrosion resistance

When welding joints are made on pure aluminium and non-age-hardenable alloys, little or no

reduction takes place in their corrosion resistance. “Little or no” reduction, because in the

case of materials with a high Mg content (>3.5% Mg), the welding heat means that there will

not normally be any microstructural changes which would reduce the corrosion resistance of

these materials. In fact anodic precipitations (Al8Mg5 phase) could theoretically form at the

grain boundaries if the metal were left too long in the 100 °C – 230 °C temperature range, and

these anodic precipitations would impair the material’s resistance to intercrystalline (stress)

corrosion. However, relatively long holding times in the critical temperature range would be

needed in order to bring this about, which is why it is highly unlikely to occur in the course of

normal welding.

With many age-hardenable aluminium alloys, the highest resistance to stress corrosion is

achieved by artificial ageing or even overageing. For this reason, the corrosion resistance of

these alloys is adversely affected by the welding heat (especially in the HAZ).

Furthermore, a deterioration of corrosion resistance may also be caused by a potential

difference between the base metal and the filler metal. For example, on 7000-series materials,

a suitably influenced HAZ will react in a strongly anodic manner to the base metal and to a

5000-series filler metal. The result is an intensified local corrosion attack.


Weldability

Material-specific peculiarities

The welding of aluminium is fundamentally different from that of steel. The melting

temperature of steel is around 1500 °C, that of aluminium around 660 °C and that of Al alloys

around 570 °C – 660 °C.

• Al 99.5: 658 °C – 659°C (almost at fusion point): The pores cannot degas in time.

• AlMg 4.5Mn: 575 °C – 640 °C (longer solidification range): The longer time period enables

the pores to degas better.

• The thermal conductivity is four times as high, necessitating high thermal input during

welding.

• Because the thermal expansion is around twice as large, increased tension and distortion

occur in the weldment.

Another problem that must be taken into account is the high-melting oxide layer (fusion

temperature around 2040 °C) which envelops the weldment and impedes welding.

Aluminium cannot become brittle, or age-harden in the heat-affected zone. On the contrary –

a loss of strength may be expected on strain-hardened and age-hardenable alloys.

Pure aluminium (Al 99.9; Al 99.5; etc.) Good weldability

Naturally hard alloys (AlMg and AlSi alloys) Good weldability

Age-hardenable alloys (AlMgSi and AlZnMg) Good weldability

AlCu (approx. 6 % Cu and Zr) AlCuMg and AlZnMgCu (approx. 1.4 – 3.0 % Cu hot cracking)

Only limited suitability

Casting alloys are basically weldable, although this will be affected by the presence and nature of any casting defects (except in the case of die-casting).

Physical properties of common aluminium materials:

Material abbreviation Electrical conductivity at 20°C

S m/mm²

Thermal conductivity at 20°C W/cm K

Solidification range °C

Al 99.5 AlMg 5 AlMg 4.5Mn AlMgSi 0.5 AlMg 1 SiCu AlZn 4.5 Mg 1 G-AlSi 12 G-AlSi 10 Mg

33.5...35.5 14.0...19.0 15.0...19.0 26.0...35.0 23.0...26.0 21.0...25.0 17.0...26.0 17.0...26.0

2.26...2.29 1.20...1.34 1.20...1.30 2.00...2.40

1.63 1.54...1.67 1.30...1.90 1.30...1.90

659...658 625...590 640...575 650...615 640...595 655...610 580...570 600...550


Influence of the electrical conductivity of different wire-electrode alloys on the seam

geometry:

1 = SG-AlMg 5 2 = SG-AlSi 5 3 = SG-Al99.5 Ti

Electr. conductivity Sm*)/mm² 15...19 24...32 34...36

Welding amperage **) A 250 300 340

Welding voltage V 26 28 29

1 Sm = 1/p p= resistivity Ω/mm²

i.e.: the higher the Sm, the better the current transfer in the material.

Result:

The penetration profile depends very much on the type of filler metal that is used !

*) Siemens

**) The changes in the amperage arise as a result of the different electrical conductivities of the filler metal alloys.

Trial:

carried out at constant

- wirefeed speed

- welding speed

- power-source settings

and with a different filler

metal in each case.


Physical properties

a.) The expansion coefficient is twice as big as with steel. This means severe distortion and

high internal stresses:

Counter-measures:

• Optimised welding sequence (Back-step): Transverse welding ahead of the

longitudinal seam

• Choice of weld process

• Transverse shrinkage should be possible (as long as possible)

b.) The thermal conductivity is 4 times as great as in steel. There is a risk of fusion defects on

thick sheets, and of gas inclusions in the melt. Attention should also be paid to the

quenching behaviour of AlZn 4.5 Mg 1.

Important: With AlZnMg alloys, traverse the 200 °C – 300 °C range as quickly as

possible!

The Rm drops from 390 N/mm²

⇒ to 350 N/mm² after 2 min

⇒ to 320 N/mm² after 6 min

⇒ to 280N/mm² after 10 min

Maintaining the temperature for too long leads to a coarse-grained microstructure = risk of

intercrystalline corrosion Caution! Do not input too much heat

High temp.: Low temp.:

Do not overheat the metal! Loss of strength! Why?

Because the grain boundaries serve as a natural impediment to the slip planes. If the

metal becomes too hot, the grain size changes (becomes larger). For this reason, the

intergranular surface becomes smaller, there is a lack of slip-plane impediments and the

metal has lost its strength.

Alternative: Re-ageing at a later stage

Counter-measures: per DVS 1608

• Do not pre-heat to more than the recommended temperature

150 °C = 80% of the strength at room temperature

200 °C = 60% of the strength at room temperature

at 400 °C, only 10% of the strength at room temperature !


• Use measuring apparatus:

Thermometers, thermal marker pins, thermal chalks or fluxes with the desired reaction

temperature

In-situ solution: Small piece of spruce wood (350 °C = light brown, 400 °C = brown,

450 °C dark brown, 500 °C = black)

• Use a reducing C2H2 flame

Influence of the oxide layer

The oxide layer (Al2O3) can cause fusion defects, leads to a notch effect from flushed-in oxide

particles (warning: has the same effect as slag inclusions in steel) and favours the formation

of pores, as the oxide layer is only liquid in the immediate vicinity of the MIG arc and also

solidifies immediately.

Counter-measures:

• Mechanical removal of the oxide layer (grinding, brushing, scraping)

• Chemical removal (pickling)

• Cleansing action of the arc (positive polarity)

• Fluxes (gas, electrode or submerged-arc powders, solders etc.)

• Deburring the sheets

NOTE:

The weld process influences the heat input, the cleansing action of the arc (AC) and

the energy concentration.

100%

80%

60%

10%

150 200 400°C


PROCESSES

The decision as to which weld process to use for aluminium welding will be influenced by the

following factors:

• Quality requirements

• Cost effectiveness

• Welding position

• Type of workpiece

• Thickness of material

TIG AC welding

In TIG welding of aluminium and its alloys, AC (alternating current) is generally used. This is

necessary because the aluminium base metal (melting point approx. 550 °C – 660 °C) is

overlain by a higher-melting oxide layer (melting temperature approx. 2040 °C – 2100 °C).

This layer is removed during the plus half-wave of the AC (with reference to the torch), in order

to permit proper fusion of the base metal in the subsequent minus phase.

This periodic alternation of the welding current makes two demands of the power source:

Firstly, to ensure re-ignition of the arc after the zero crossing; and secondly, to keep the noise

emissions from the arc column as small as possible.


Advantages:

• Controlled through-welding from one side without weld-pool backup

• Good positional weldability

• Very good weld-seam appearance

• No re-working needed

Disadvantages:

• Low welding speed

• Difficult root fusion on fillet welds

• Preheating is advisable for wall thicknesses of 8 mm and upward

• High distortion

• Relatively wide softening zones

TIG DC helium welding

TIG DC welding with a negatively poled electrode was first patented in the USA in the early

1940’s, under helium shielding gas.

The high heat concentration (70% of the arc energy is concentrated on the workpiece) quickly

creates a small, fluid weld-pool from which the oxides are forced aside by surface tension.

The surface of the seam thus mostly has a dull grey appearance. TIG welding with DC is

mostly performed in a mechanised manner.

Advantages:

• High welding speed

• Low weld reinforcement

• Low distortion

• Insignificant de-hardening in the HAZ, as there is only low thermal-input

• Low risk of porosity and fusion defects

• Deep penetration

Disadvantages:

• Required arc length must be exactly ensured

• Exact weld-seam preparation is needed


Aluminium manual electrode (MMA) welding

The flux and arc-stabilising additives needed for MMA welding of aluminium are provided by

the coating of the melting rod electrode. Welding is performed with DC, and the workpiece is

connected to the minus pole.

As the seams welded by manual electrode welding solidify very quickly, they are heavily

infiltrated with gas inclusions and so are considerably inferior in quality to seams welded by

gas-arc welding. For this reason, manual electrode welding is irrelevant to welded structures.

It is used for repairing castings made of AlSi alloys. Electrodes are practically only available in

S-AlSi 12 and S-AlSi 5.

MIG welding

In this case, it is mainly the pulsed-arc technique that is used. Where the parameters have

been correctly selected, exactly one droplet of filler metal per pulse is detached from the wire

electrode. The result is virtually spatter-free welding.

Investigations have shown that for different filler metals and shielding gases, differentiated

pulse-forms greatly improve the welding result. Particularly in the field of aluminium, where the

thicknesses of the material are becoming ever smaller, the central requirement made of the

power source is that it should deliver a very steady arc at the lower end of the power range

(approx. 30 A). It is just as important here to be able to set a low background current as it is

to have a fast-responding arc-length regulation facility, i.e. when the wire stick-out length is

changed, the length of the arc must remain constant.

Variable pulse form


Arc-length regulation

Advantages:

• Small material-thicknesses can be welded (0.8 mm)

• Wires of bigger diameter can be used (better wirefeed properties)

• Good positional weldability

• Low heat input

• Low distortion

• Fully mechanisable

Disadvantages:

• Higher incidence of porosity

• With thicker material, through-welding in PA (gravity) position tends to be

difficult without weld-pool backup

• Welding over tacks can lead to welding defects


SPECIAL FEATURES OF WELDING ALUMINIUM WIRES

Torch equipment

• To work with soft aluminium wires, torches are needed with plastic or Teflon inner

liners and with suitable liner inserts in the torch neck.

• For aluminium wires, contact tubes of the next-larger diameter must be used.

• For pure aluminium or Si-alloyed wires, push-pull systems are advantageous

Wirefeed:

Compared to steel wires, aluminium wires are very soft. This makes very special demands of

the wirefeed arrangements, which must ensure abrasion-free wire travel.

A four-roller drive - with suitable feed rollers - will apply sufficient force to the wire that is to be

fed, even at low contact pressures. In most cases, smooth, polished semicircular-grooved

rollers are used.


⇒ Practical tip for pressure adjustment of the contact pressure rollers

Set more pressure to the front contact pressure rollers than to the rear ones.

If you stop the wire by hand, the rollers should “slip” on the wire! The cast (the diameter of the

unreeled wire coil) should not be less than 800 mm. The wire helix (the distance one end of a

strand of wire lying on a flat surface rises off this surface) should not be more than 30 mm

NOTE:

If it is less than 800 mm

- the friction in the wire inner liner is too great (F2 motor current load test)

- the friction in the drive rollers is too great

- the friction in the contact tube is too great

- the drive rollers are out of alignment

- there is too much contact pressure on the contact pressure rollers, causing deformation

of the wire

Feed rolls:

Error: If the surface of the rollers is too rough, this will ruin the wire

As seen in: Shavings

Error: If the edges of the rollers are too sharp, this will ruin the wire

As seen in: Aluminium wool

Correct: The surface of the rollers is polished, and the edges of the rollers are

smoothed

As seen in: Perfect wirefeed is possible


Start and end of welding in aluminium welding

Welding program for preventing lack of fusion in

aluminium at the beginning of the seam

Aluminium not only has low density, but it is also a good thermal conductor. These properties

tend to cause lack of fusion at the start of welding. To counteract this, there is a special

function (supported by the power source) which delivers higher welding power at the start of

the weld. In this way, the base metal starts to be melted even during the ignition phase. Once

sufficient heat has been inputted into the weld pool, the power is reduced to the nominal

welding power. When the heat runs ahead towards the end of the seam and there is a risk of

"drop-through", the welding power is reduced again, to a lower “crater-fill” current.

⇒ Practical tip: The start and end settings depend on the thickness of the sheet. As a

universal parameter, I-S 135% with a slope time of 1.0 second, and I-E 50%, have been found

to work very satisfactorily.

If your power source does not offer any such function, then run-on and run-off plates must be

used, as stipulated by DVS 1608.

In the welder has to interrupt the welding of the seam, he should increase the welding speed

so that the end of the seam tapers off in a wedge shape.

Crater-fill

current

COMMAND

welding current

Starting

current


The problem with ignition:

During the ignition phase, a short-circuit occurs. With conventional ignition, the amperage

may now rise to as much as 700 A during this short circuit. Due to this high amperage, the

short circuit is now resolved in an “explosive” manner, resulting in spatter around the start of

the weld.

This problem can be prevented by the Spatter Free Ignition (SFI) option.

Advantages of conventional ignition

• No push-pull drive needed

• When the ignition functions well, it permits short starting times

Disadvantages:

• No reproducible ignition

• Spatter ejection

• The thicker the wire, the higher the arc starting current.

• The high arc starting current (the highest current to occur during the entire

process) places great stresses and strains on the contact tube, resulting in

shortened contact-tube lifetime

The power source must be able to supply the current necessary for breaking open a short-

circuit bridge. This current is generally higher than the pulsing current!

SPATTER-FREE IGNITION OPTION

The Spatter Free Ignition option (SFI) enables the arc to be ignited with virtually no spatter. At

the beginning of welding, the wire is slowly fed as far as the surface of the workpiece and

stopped as soon as it touches down. Next, the welding current is activated and the wire is

retracted. Once the correct arc length has been reached, the wire starts being fed at the

wirefeed speed specified for this particular weld process.

To activate the SFI option, proceed as follows:

- Select SFI (parameter Fdc – feeder-creep) in the Set-up Menu

- Exit from the Set-up Menu

- Select the welding program


+ Note! The Spatter Free Ignition option can only be factory-enabled via software. At

present, only Fronius push-pull wirefeed systems (Robacta Drive and Pull-

MIG), are supported.

Advantages of the Spatter Free Ignition option

• Virtually spatter-free ignition

• No undue stressing of the contact tube by high arc start currents

(= prolonged contact-tube life)

• 100% reproducible ignition

• Trouble-free ignition, even with thicker wires

• Improved wire feeding resulting from the use of a push-pull drive

• The max. short-circuit current that the power source has to deliver can be

smaller than the pulsing current (below 50 A, as against approx. 500 A with

conventional ignition)

Ignition comparison

Conventional Spatter Free Ignition


“SYNCHRO PULS” OPTION

The “SynchroPuls” option is also recommended for welds using aluminium alloys where a

rippled appearance is desired for the weld seams, especially in the field of mechanised and

automated welding.

Mode of operation:

The SynchroPuls option involves a pulsed arc which alternates between two operating points

on a synergic characteristic line.

The two operating points result from the wirefeed speed (vD) being changed – positively and

negatively – by a value dFd (0 to 2 m/min), that can be adjusted in the Set-up Menu.

e.g: vD = 10.0 m/min and dFd = 1.5 m/min

=> Operating point 1: = 8.5 m/min Operating point 2: = 11.5 m/min

The frequency F (0.5 to 5 Hz) determines how often the alternation between the two operating

points takes place, and is also specified in the Set-up Menu

If the frequency is set to F = 0, the SynchroPuls option is switched off.

The arc-length correction for the lower of the two operating points is made via the arc-length

correction parameter (e.g. on the Jobmaster torch, wirefeeder, remote-control unit, ...)

However, the arc-length correction for the higher of the two operating points must be made in

the Set-up Menu, via the parameter “Arl”.

The graph below shows how SynchroPuls works, in this case when used with the “Aluminium

welding start-up” mode (I-S = Starting current, SL = Slope, I-E = Final current):


Press and hold the torch trigger

Release the torch trigger

Time

Current

Wel

din

g c

urr

ent


GASES FOR ALUMINIUM WELDING

Pure argon delivers a quiet, steady metal transfer, but is inferior to argon-helium mixtures in

terms of penetration intensity and safety from hydrogen-induced porosity.

Argon-helium mixtures with helium components of between 30 % and 70 % have proved

most advantageous. The most widely used mixture is one consisting of 50 % helium and

50 % argon.

The higher the helium-component, the higher the arc voltage that is needed for the same arc

length.

Shielding gases with O2 (oxygen = less porosity) and N2 (nitrogen) admixtures in the Vpm

(ppm) range have also come onto the market. O2 and N2 admixtures do not improve the

penetration behaviour, however.

Shielding gases

Argon: (l 1 to DIN 32 526 / EN 439) is the standard shielding gas for general

welding jobs.

Argon 70/He 30: (l 3 to DIN 32 526 / EN 439) is used wherever more advanced

requirements are made with regard to the porosity behaviour, as well as

for pure aluminium and larger wall thicknesses.

Argon 50/ He 50: (l 3 to DIN 32 526 / EN 439) is used wherever extremely stringent

requirements are made in respect of freedom from porosity, especially

with pure aluminium, e.g. Al 99.5 or Al 99.8, or with greater wall

thicknesses.


Shielding gas consumption (with reference to argon):

• Dip-transfer arc: 12 - 15 l/min

• Spray and pulsed arc: 15 - 20 l/min

For mixed gases, the following data apply:

Shielding gas Correction factor *) Minimum flow rate

Ar 70/ He 30 1.17 20 l/min

Ar 50/ He 50 1.35 28 l/min

Ar 30/ He 70 1.70 35 l/min

100% He 3.16 40 l/min

The higher the helium content, the more degassing is facilitated (higher thermal input).

The purity and mixing accuracies correspond to DIN 32 526 / EN 439. These gases can be

used for all types of arc, and all welding power ranges. Other welding shielding gases are

available on request.

*) Gas flow rate as per read-out x Correction factor = Actual flow rate

The bigger the helium-component mixed with the argon, the less

the porosity

Base metal: Al 99.5, 10 mm th., closed square

butt weld

Wire electrode: S-Al 99.5 Ti, diameter 1.6 mm

Torch: 15°, leading

Wirefeed speed 8.4 m/min

Welding speed: 62 cm/min


Penetration form

The higher the helium content, the wider (and thus flatter) the seam. The penetration is no

longer "finger-shaped", as it is with argon, but becomes rounder and deeper.

The more favourable penetration behaviour makes it easier to be sure of achieving through-

welding in the root zone, and permits higher welding speeds.

Table 5: Influence of increasing helium content in argon shielding gas

Composition of shielding gas 100% Ar________________________100%He Arc behaviour Somewhat smoother Seam width Increases, seam becomes flatter Weld appearance Becomes more finely rippled, on Mg wire ⇒ greyish-

brown precipitation* ⇒ not a disadvantage Penetration Becomes deeper and more rounded Welding speed Can be increased Propensity to fusion defects Decreases Propensity to porosity Decreases Pre-heating Can be reduced or dispensed with altogether Temperature control Workpiece becomes hotter ⇒ must be compensated for

by higher welding speed Shielding-gas costs Increase (but consider overall cost picture!)

* Cause: The higher the helium content, the narrower the cleaning zone becomes


WELD-SEAM PREPARATION

Working

The very greatest cleanliness is required in the working and welding of the seam, as

otherwise its corrosion resistance may be impaired and it will tend to form pores. Work with

aluminium should take place completely separately from work with steel.

Tools that have been used for steel must not be used for aluminium. Aluminium should be

worked and stored in a dust-free, dry and splashwater-free environment. Clean clothing and

gloves are also necessary.

Aluminium is highly sensitive to notch impact (even when under static loading) and should

thus not be scribed with a sharp scribing tool or stamped with a marking punch. Usually, a

pencil is used for tracing. It is possible to straighten aluminium by pressing, hammering or

flame-straightening - still following the above rules, however. Moreover, flame-straightening

should only be carried out after consultation with the manufacturer. All these points also

particularly apply to the weld-seam preparation. If there is not to be a root gap, the root

penetration side should be chamfered.

In open-root welding, the oxide inclusions collect in the middle. Subsequent root-pass

chipping and capping, or a weld-pool back-up, are helpful measures here.

⇒ Practical tip: Brush the area around the seam first (CrNi brush) and/or degrease it (with

acetone alcohol).

Weld shapes

The shape of the weld will be largely dictated by the thickness of the material and the design

of the weldment. For fully mechanised welding, extruded profiles with an integrated pool

backing support are usual. For water-tight Y- or U-welds, the root pass should be TIG-

welded, and all other passes (to fill the groove) should be MIG-welded.


Thickness of

workpiece mm Shape of groove

Wire Ø mm

Weld current A

Welding speed cm/min

Argon consumption

l/min

Number of passes

2 3 4 5 6 8 10 12 16 20

II II II II II V V V V V

0.8 1.0 1.2 1.2 1.6 1.6 1.6 1.6 1.6 1.6

110 130 160 180 200 240 260 280 300 320

80 75 70 70 65 60 60 55 50 50

12 12 15 15 15 16 16 18 20 20

1 1 1 1 1 2 2 2 3 3

Guideline values for manual welding:

These values will be influenced by the type of shielding gas, the material and the type of arc.

Advice on making settings

Weld-seam preparation:

• Root notches can be prevented by chamfering the edges on the root-side of the weld.

Oxides in aluminium behave like slag in steel and must also be prevented.

• Only use a forming cutter for preparing the edges. Also, do NOT use any plastic-bound

grinding discs, even for root-preparation of the capping pass POROSITY DEFECTS !

• Clean using ACETONE and CrNi hand brushes

Wrong: Edges not chamfered Right: Edges chamfered

Oxides not fully flushed off

the end faces –

root notch

Oxides fully flushed off the end

faces –

good root-side drop-through


Table 1: Shapes of groove for TIG and MIG welding

Dimensions

Workpiece

thickness “s”

[mm]

One or both

sides

Name Symbol Cross-sectional view of

groove

α - β

Degrees

Gap b Root height c Weld process

Up to 2 One side Flange-

weld

- - - TIG

Up to 4 One side Edge joint

weld

- - - MIG

TIG

Up to 4 - 0 to 1 - TIG

2 to 4

One side - 0 to 2 - MIG

- - TIG 4 to 16 Both sides

Square butt

weld

0 to 3

MIG

4 to 10

90 to 100 0 to 1 TIG

6 to 20

One or

Both sides

V weld 50 to 70 0 to 2

Up to 2 MIG

Over 6

One side

Y weld

15 to 30

3 to 7

2 to 4

MIG

60 to 70

~3 TIG

Over 10

One or

Both side

Y weld 50 to 70

0 to 4 2 to 6 MIG

Over 10

One side

U weld

Up to 10

0 to 1

2 to 4

MIG

Over 10

Both side

Double

Y weld

50 to 70

0 to 2

3 to 4

MIG

Remember that larger weld preparation angles are needed on aluminium than on steel!

Due to the melting point, root-welds on pure aluminium are more difficult to manage – keep

the arc on the root face !


WELD DEFECTS

Consequences of inadequate gas shielding

Insufficient shielding of the weld pool leads to reactions between the air and the weld pool,

and to porous welds with inadequate stability.

Fault:

Draughts (e.g. out on construction

sites) interfere with

the shielding gas coverage

Consequence:

Insufficient gas shielding, pore-

formation in the weld-seam

The main cause of pores in aluminium is the inclusion of hydrogen and nitrogen (from 0.5%

N2 upwards => high susceptibility to pore-formation).

Sources of hydrogen:

• Damp or dirty weld region

• Damp or dirty filler metal

• Hydrogen in the filler metal

• Leaky torch system

• Blown-in air

• Unstable arc

• Damp shielding gas due to the use of the wrong quality of hose or to a leaky system

Air

Air Air

Air


Fusion defects

Only the arc (not the weld-pool) has sufficient energy to fuse the groove face and create a

stable join.

Other influential criteria

• Thermal input

• Electrical conductivity of the wire electrode

• Characteristic curve in the control response of the power source

• Type of arc

• Composition of shielding gas

If fusion defects are to be prevented, then, the seam to be welded must be expertly prepared

and worked.

The following mistakes can be made here:

Weld preparation angle is too small

Correct: 60° to 70°

Root-face height is too great

Root opening gap is too large

Edge misalignment is too great

Overwelding of strongly reinforced beads

Correct: Before overwelding, grind the

bottom bead so that this is trough-shaped


Attachment fusion defect when welding at low arc power;

attachment point not ground;

not welded with sufficient overlap.

Correct: Grind end of seam, ignite before the end of the

seam and continue welding.

Fusion defects may occur when the arc is prevented from reaching the weld edges, or the

already-welded pass, by the weld pool running ahead.

Welding speed is too low or deposition rate is too high. Do not weld over-thick beads!

Welding in the PG position (vertical-down). The deposition rate must be limited. Do not weld too slowly!

Excessively “pushing” torch angle.

Pores remain in the weld pool. With

vertical-up (PF) welds, better

degasification is needed!

If the torch position is incorrect, the arc fuses the weld-edges on one side only.

This results in fusion defects, and thus in unstable joins.


The torch is not being held over the middle.

The torch is being inclined too much towards one weld edge.

Faulty torch position caused by restricted accessibility

Oxide inclusions

A small quantity of oxides is necessary for the stability of the arc. However, too much will

cause oxide inclusions, which can become the starting points of cracks when subjected to

dynamic loading.

Preheating table

Preheating

Preheating is necessary in situations where the high thermal conductivity of aluminium makes

it difficult or impossible to achieve sufficient penetration. Make sure that the oxide layer on the

weld edges does not grow to become too thick as a result of over-long preheating times or of

excessive O2 in the fuel gas. Attention should also be paid to the influence of the preheating

temperature and time on the properties of the material, especially with age-hardenable alloys

and cold-worked materials with a high Mg content.


Guideline values for the preheating temperatures and times for welding wrought aluminium

alloys.

Material Thickness range of sheet or wall, in mm Max. preheating temp.

°C

Max. preheating time

min

TIG MIG

AlMgSi 0,5

AlMgSi 1

AlMgSi 0,7

≥ 5 to 12

(>12)

>20

180

200

220

250

60

30

20

10

AlZn4,5Mg1 1) ≥ 4 to 12

(>12)

>16

140

160

30

20

AlMg 4,5Mn

AlMg 3 2)

≥ 6 to 12

(>12)

>16 150 to 200 10

1) Prolonged dwell-times at temperatures of between 200 °C and 300 °C lower the alloy’s ability to self-harden.

2) Care is needed with this alloy due to its susceptibility to intergranular corrosion!

Types of preheating torch for use on steel: With aluminium, always use the next-larger size of

torch!

Type of preheating torch Oxygen consumption Workpiece thickness

L/h mm

Single-flame torches

Size 2 160 <15

Size 4 500 <15

Size 5 800 <15

Size 6 1250 <15

Size 8 2500 <40

Size 10 4000 <40

Multi-flame torches

Size 9 4000 30...100

Size 11 7500 30...100

Torches with flame selection

3 or 2 flames, size 3 1000 5...30

5 or 2 flames, size 3 1500 5...30

3 or 2 flames, size 4 1500 30...60

5 or 2 flames, size 4 2500 30...60

Special torches >60


A good method of roughly estimating the temperature of the spot under the torch flame is to

observe the incandescent colours of the materials. If these are not manifesting any

incandescent colours, or if these colours have not yet appeared, or not appeared sufficiently

clearly, then the rough temperature estimate can often be made with sufficient accuracy in

practice by briefly rubbing various agents across the surface. The residues on the heated

surface will then discolour differently in different temperature ranges. This procedure has long

been used with aluminium materials, for example.

When rubbed across a hot surface, a small piece of spruce wood will leave behind a light

brown mark at 350 °C, a brown one at 400 °C, a dark brown one at 450 °C and a black one at

500 °C.

A more finally gradated, and more accurate, method of determining the temperature in the 65

°C – 670 °C range is by using coloured chalks. In this case, too, the temperatures are

indicated by colour changes, as set out in the table below:

Colour n° Initial colour changes to: at a temperature of (°C):

2815/ 65 Pink Blue 65 2815/ 75 Pink Blueish-green 75 2815/100 Pink Blue 100 2815/120 Light green Blue 120 2815/150 Green Mauve 150 2815/175 Mauve Blue 175 2815/200 Blue Black 200 2815/220 White Yellow 220 2815/280 Green Black 280 2815/300 Green Brown 300 2815/320 Green White 320 2815/350 Yellow Reddish-brown 350 2815/375 Pink Black 375 2815/420 White Brown 420 2815/450 Pink Black 450 2815/500 Brown Black 500 2815/600 Blue White 600 2815/670 Green White 670

Practical tip: For more exact temperature measurement,

measuring apparatus with a display is required.


APPLICATIONS IN THE AUTOMOBILE INDUSTRY

AUDI A2

AUDI A8

BMW FERRARI


ALFA

LANCIA

Bibliography:

DIN 17007 / SLV Duisburg GmbH

Deutscher Verband for Schweisstechnik (German Welding Society):

Gas-shielded metal arc welding

Linde publication: Gas-shielded arc welding of aluminium

Oerlikon Zusatzwerkstoffe

Alcotec

Aluminium Pocketbook (Publisher: Düsseldorf Aluminium Centre)

www.audi.com

www.lancia.com

www.alfaromeo.com


Program Table Variostar 317

Aluminium AlMg5 Ø1,0

Setting voltage stages and WFS

Wirefeed speeds and deposition rates in MIG welding (according to Messrs. Linde,

Höllriegelskreuth, Germany)

amperage [= (+) ] in A

w

iref

eed

sp

eed

in m

/min

d

epo

siti

on

rat

e in

kg

/h


Extract from the TPS special-program list

Program Type of wire Gas Base material

0209 Al99,5 100% Ar Al99,5

0176 Alloy 2319 Al 70% Ar 30% He Al99,5

0362 AlMg4,5Mn 100% Ar AlMg3

0556 AlMg4,5MnZr 100% Ar AlMg3

0145 AlMg5 100% Ar AlMg3

0288 AlSi12 100% Ar AlMgSi

0510 AlSi5 100% Ar Al Guß

0557 AlMg4,5MnZr 70% Ar 30% He AlMg3

0222 AlMg4,5Mn 50% Ar 50% He AlMg3

0443 AlMg4,5Mn 25% Ar 75% He AlMg3

0487 Alloy 2319 Al 15% Ar 85% He Al 1201

0481 Alloy 2319 Al 100% He Al 1201

0247 AlSi5 100% Ar AlMgSi1

0307 AlSi5 50% Ar 50% He AlMg3

0109 AlSi5 100% Ar Al99,5

This list is continually updated – for more detailed information, please contact your Fronius

technician.

Documents

aluminiumwelding_42_0410_0590_200