Design and Fabrication of DIE for Comp Action of Metal Powder in Powder Metallurgy

8/2/2019 Design and Fabrication of DIE for Comp Action of Metal Powder in Powder Metallurgy

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MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY

BHOPAL (M.P.)

DEPARTMENT OF MECHANICAL ENGINEERING

MANIT, BHOPAL [M.P.]

2011-2012

A Major Project report on

Design and Fabrication of DIE for compaction of Metal

Powder in Powder Metallurgy

for the degree of

BACHELOR OF TECHNOLOGY

IN

MECHANICAL ENGINEERING

Submitted By: Under the Guidance of:

Mohit Assudani (081116052) Asst. Professor Dr. Rajesh Purohit

Mirza Amir Ahmed Beg (081116058) Asst. Professor R.S. Rana

Pranay Vyas (081116081)

Aditya Pagare (081116086)


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ACKNOWLEDGEMENT

Words shall never be able to pierce through the gamut of emotions that are

suddenly exposed during the routine of our life. They shall never be able neither to

describe the spirit with which we worked together nor shall they ever be able to

express the feeling we felt towards our guides.

This project was a struggle that was made much more difficult due to several

reasons. Sometimes we were like rudderless boat without knowing what to do next. It

was then the timely guidance of them that has seen us through all these odds. We

would be very grateful to them for their inspiration, encouragement and guidance in

all phases of the discretion.

It is our pleasure that Dr. R.M. Sarvaiya, HOD of Mechanical Engineering for his

constant encouragement and valuable advice during the course of our project.

We would also thank Associate Professor Dr. Rajesh Purohit & Asst. ProfessorR.S. Rana who has tremendously contributed to this project directly or indirectly,

gratitude from the depths of our heart is due for them.

Mohit Assudani

Mirza Amir Ahmed Beg

Pranay Vyas

Aditya Pagare


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MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY

BHOPAL (M.P.)

CERTIFICATE

This is to certify that Mr. Mohit Assudani, Mr. Mirza Amir Ahmed Beg, Mr.

Pranay Vyas and Mr. Aditya Pagare students of final year B.Tech Mechanical

Engineering in the academic year 2011-12 of this institute have completed major

project work entitled Design and Fabrication of DIE for compaction of Metal

Powder in Powder Metallurgy based on the syllabus and have submitted a

satisfactory report on it as a partial fulfillment for the degree of Bachelor of

Technology in Mechanical Engineering.

Project Guide Head of theDepartment

Associate Professor Dr. Rajesh Purohit Dr. R.M. Sarvaiya

& Asst. Professor R.S. Rana Department of Mechanical

Department of Mechanical Engineering, MANIT Bhopal.

Engineering, MANIT Bhopal.


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CONTENTS

S. No. Topic Page No.

1. Introduction

1.1 What are we aiming to do!

1

2. Die 3

2.1 Introduction

2.2 Die Forming

2.3 Components for Die Toolsets

2.4 Die Operation & Types

3. Die Material (High Carbon High Chromium Steel) 7

3.1 Available Options for Die Material

3.2 Properties and Technical Data for High Carbon HighChromium Steel

3.3 Applications

4. Design of Die 13

4.1 Introduction

4.2 Calculations

4.3 Die Design in PRO E


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5. Die Fabrication

5.1 Turning

5.2 Drilling

5.3 Boring

5.4 Internal Grinding

5.5 Oil Quenching

20

6. Aluminum (Metal Powder) 26

6.1 Introduction

6.2 Properties of Aluminum

6.3 Why Aluminum?

6.4 Aluminum - Product Applications

6.5 Aluminum Alloys - Heat Treatment & Welding

6.6 Aluminum Supply

7. Specimen Manufacturing (Powder Metallurgy) 30

7.1 Introduction

7.2 History

7.3 Powder Manufacturing or Atomization

7.4 Zinc Stearate as Lubricant

7.5 Powder Blending

7.6 Powder Compaction

7.7 Sintering

7.8Powder Metallurgy using Aluminum


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7.9Aluminum comparison to other P/M materials

8. Testing of Specimens 44

8.1Introduction to Universal Testing Machine

8.2 Indirect Tensile Test

8.3 Compression Test

8.4 Density Comparisons

8.5 Hardness Test

9. Scope of Improvement 58

10. Final Conclusions 60

11. References 61


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1.Introduction

The word "die" is a very general one and it may be well to define its meaning as it will be employed

in our work. It is used in two distinct ways. When employed in a general sense, it means an entirepress tool with all components taken together. When used in a more limited manner, it refers to thatcomponent which is machined to receive the blank, as differentiated from the component called the

punch which is its opposite member.

The initial data needed to design metal powder compaction die are: compact shape and density,

powder mix composition, compaction and radial pressure, part number and tool materials. The

design targets are: diameters of insert and ring, sometimes number of rings and interference or

interferences. The constraints include: no tensile stresses on the insert, no risk of relative motion at

part ejection, no unwanted alteration of material microstructures and maximum stresses always

below the allowable limits. Usually the design is based on engineering experience, company

knowhow, and approximated the analytical calculations and cost considerations.

This study is focused on the use of numerical methods to determine the design parameters of dies

for powder compaction. Both room temperature and warm compaction have been investigated.

Numerical algorithms, implemented into FEM calculation codes, enable one to optimize the

common diameter of insert and ring, corresponding to the lowest stresses on both items, or to find

the minimum value of the outer diameter. A wide range of compaction pressures, die materials and

geometries, interferences and allowable stresses have been explored. To compare the results,

based either on analytical or numerical methods, circular dies have been investigated. The

differences among the results depend on the consideration of the actual stressed length, or

compact height, and total die length. The calculations by analytical methods overestimate thestresses. The report presents some suitable nomograms for the comparison of results of

calculations performed either by Lames Formula or by sophisticated numerical methods.

Two-piece designs were considered in order to make the dies easier to assemble than the five-piece

dies that were previously used. The two areas of concern were the stresses at the interior corner ofthe die cavity and the distortion of the cavity wall due to the interference fit between the two pieces

and the pressure exerted on the die during the compaction process. A successful die design would

have stresses less than the yield stress of the material.

Design factors that were investigated include the compaction force, the size of the cavity, and the

outer radius.

Adding a FACTOR OF SAFETY of 3 to the compaction force tends to lead to conservativeestimates of the stresses but not for the wall distortion. However, when the FACTOR OF SAFETY

of is removed, the wall distortion is not affected enough to discard the design.


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1.1 What Are We Aiming To Do ! Learn about the working of dies. Selection of a material for die manufacturing based on working conditions & the type of

product to be created using this die.

Calculations for design of die i.e. calculating thickness of the shell to bear the load to beapplied on die in the process.

Fabrication of die by using different processes i.e. turning, drilling, boring etc. Preparing specimens using this die & testing them.


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2.DIE

2.1 Introduction of Die

A die is a specialized toolused inmanufacturing industriesto cutor shapematerialusing a press.

Likemolds, dies are generally customized to the item they are used to create. Products made with

dies range from simplepaper clipsto complex pieces used in advanced technology.

2.2 Die forming

Forming dies are typically made bytool and die makersand put into production after mounting into

apress. The die is a metal block that is used for forming materials like sheet metalandplastic. Forthevacuum formingof plastic sheet only a single form is used, typically to form transparent plastic

containers (calledblister packs) for merchandise. Vacuum forming is considered a simplemolding

thermoformingprocess but uses the same principles as die forming. For the forming of sheet metal,

such as automobile body parts, two parts may be used, one, called the punch, performs the

stretching, bending, and/or blanking operation, while another part, called the die block, securely

clamps the work piece and provides similar, stretching, bending, and/or blanking operation. The

work piece may pass through several stages using different tools or operations to obtain the final

form. In the case of an automotive component there will usually be a shearing operation after the

main forming is done and then additional crimping or rolling operations to ensure that all sharp

edges are hidden and to add rigidity to the panel.

Components for Die Toolsets

The main components for Die Toolsets are:

Die block - This is the main part that all the other parts are attached to. Punch plate - This part holds and supports the different punches in place. Blank punch - This part along with the Blank Die produces the blanked part. Pierce punch - This part along with the Pierce Die removes parts from the blanked finished

part.

Stripper plate - This is used to hold the material down on the Blank/ Pierce Die and strip thematerial off the punches.

Pilot - This is used to keep the material being worked on in position. Guide / Back gage / Finger stop - These parts are all used to make sure that the material

being worked on always goes in the same position, within the die, as the last one.

Setting (Stop) Block - This part is used to control the depth that the punch goes into the die. Blanking Dies - See Blanking Punch
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Pierce Die - See Pierce Punch. Shank-used to hold in the presses. it should be align and situated at the center of gravity of

the plate.

2.3 Die operations and types

Die operations are often named after the specific type of die that performs the operation. For

example a bending operation is performed by a bending die. Operations are not limited to one

specific die as some dies may incorporate multiple operation types:

Bending: The bending operation is the act of bending blanks at a predetermined angle. Anexample would be an "L" bracket which is a straight piece of metal bent at a 90 angle. Themain difference between a forming operation and a bending operation is the bending

operation creates a straight line bend (such as a corner in a box) as where a form operationmay create a curved bend (such as the bottom of a drink can).

Blanking: A blanking die produces a flat piece of material by cutting the desired shape inone operation. The finish part is referred to as a blank. Generally a blanking die may only cut

the outside contour of a part, often used for parts with no internal features.Three benefits to die blanking are:

1. Accuracy. A properly sharpened die, with the correct amount of clearance between the punchand die, will produce a part that holds close dimensional tolerances in relationship to theparts edges.

2. Appearance. Since the part is blanked in one operation, the finished edges of the part producea uniform appearance as opposed to varying degrees of burnishing from multiple operations.

3. Flatness. Due to the even compression of the blanking process, the end result is a flat partthat may retain a specific level of flatness for additional manufacturing operations.

Broaching: The process of removing material through the use of multiple cutting teeth, witheach tooth cutting behind the other. A broaching die is often used to remove material fromparts that are too thick for shaving.
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Bulging: A bulging die expands the closed end of tube through the use of two types ofbulging dies. Similar to the way a chefs hat bulges out at the top from the cylindrical bandaround the chefs head.

1. Bulging fluid dies: Uses water or oil as a vehicle to expand the part.2.

Bulging rubber dies: Uses a rubber pad or block under pressure to move the wall of a workpiece.

Coining: is similar to forming with the main difference being that a coining diemay formcompletely different features on either face of the blank, these features being transferred from

the face of the punch or die respectively. The coining die and punch flow the metal bysqueezing the blank within a confined area, instead of bending the blank. For example: an

Olympic medal that was formed from a coining die may have a flat surface on the back and a

raised feature on the front. If the medal was formed (or embossed), the surface on the back

would be the reverse image of the front.

Compound operations: Compound dies perform multiple operations on the part. Thecompound operation is the act of implementing more than one operation during the presscycle.

Compound die: A type of die that has the die block (matrix) mounted on a punch plate withperforators in the upper die with the inner punch mounted in the lower die set. An invertedtype of blanking die that punches upwards, leaving the part sitting on the lower punch (after

being shed from the upper matrix on the press return stroke) instead of blanking the partthrough. A compound die allows the cutting of internal and external part features on a singlepress stroke.

Curling: The curling operation is used to roll the material into a curved shape. A door hingeis an example of a part created by a curling die.

Cut off: Cut off dies are used to cut off excess material from a finished end of a part or to cutoff a predetermined length of material strip for additional operations.

Drawing: The drawing operation is very similar to the forming operation except that thedrawing operation undergoes severe plastic deformationand the material of the part extends

around the sides. A metal cup with a detailed feature at the bottom is an example of the
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difference between formed and drawn. The bottom of the cup was formed while the sides

were drawn.

Extruding: Extruding is the act of severely deforming blanks of metal called slugs intofinished parts such as analuminumI-beam. Extrusion dies use extremely high pressure fromthe punch to squeeze the metal out into the desired form. The difference between cold

forming and extrusion is extruded parts do not take shape of the punch.

Forming: Forming dies bend the blank along a curved surface. An example of a part that hasbeen formed would be the positive end(+) of a AA battery.

Cold forming (cold heading): Cold forming is similar to extruding in that it squeezes theblank material but cold forming uses the punch and the die to create the desired form,extruding does not.

Roll forming: a continuous bending operation in which sheet or strip metal is graduallyformed in tandem sets of rollers until the desired cross-sectional configuration is obtained.

Roll forming is ideal for producing parts with long lengths or in large quantities.

Swaging: Swaging (necking) is the process of "necking down" a feature on a part. Swaging isthe opposite of bulging as it reduces the size of the part. The end of a shell casing that

captures the bullet is an example of swaging.

Trimming: Trimming dies cut away excess or unwanted irregular features from a part, theyare usually the last operation performed.
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3. Die Material

(High Carbon High Chromium Steel)

Powders are usually compacted with pressures between approx. 300 and 650 N/mm2.All dies of the

compacting tool have to withstand these high loads not only once but several 100 000 to 1 000 000

times without breaking or getting plastically deformed. Neither may they under these loads expand

elastically to such an extent that they jam in the punch. Even an ever so small amount of plastic

deformation during one compacting cycle would, after a number of cycles, lead to a sizable

shortening and thickening of the punch. It does not take much imagination to realize the

consequences: As the punch gets shorter, the height of the compacts increases correspondingly,

and as the punch gets thicker, it eventually jams in the die and breaks and possibly damages the

entire tool.

Thus, punches must possess high compressive yield strength, high toughness and high fatigue

strength. In cases where punches form part of the side walls of the compacting tool, they must, in

addition to the mentioned properties, have a sufficiently high surface hardness. Surface-hardening

of punches, if necessary, has to be carried out with great care, in order to avoid embrittlement and

surface cracking. Only the toughest types of tool steels are suitable for punches. Ideally, theyshould combine the following properties:

Good machinability when soft-annealed.

Highest possible toughness and fatigue strength after hardening.


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Highest possible dimensional stability and lowest possible susceptibility to cracking in the

hardening procedure.

Highest possible wear resistance.

3.1 Available Options for die material:

O1 tool steel General purpose oil hardening tool steel which hardens at a relatively

low temperature with minimum distortion.

D2 tool steel High carbon high chromium tool steel giving a good hardness withadded toughness. This steel can be vacuum hardened when minimum

distortion is required.

D3 tool steel Similar steel to D2 tool steel, this steel attains a slightly higher

hardness and has good abrasion resistance.

D6 tool steel Popular European high carbon high chromium tool steel, with highhardness achievability and good abrasion resistance, akin to D3 tool

steel.

A2 tool steel Air hardening tool steel which is easier to machine than D2 or D3 butoffers high abrasion resistance with good toughness.

H13 tool steel 5% chromium hot work tool steel. This steel is air hardening with very

little distortion. H13 tool steel can be vacuum hardened and may bewater cooled in service.

S1 tool steel Excellent tough and shock resisting tool steel, with good abrasion

resistance. When hardened S1 has a good cutting ability with great

toughness

P20 tool steel Pre-hardened high tensile steel which is readily machinable. P20 canalso give a higher hardness than its supply condition and can be

nitrided.

1.2767 tool

steel
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4.25% nickel steel, which achieves a good through hardness. 1.2767 is

capable of taking a good polish and is commonly used as a plasticmould steel.

M2 high speedsteel General purpose high speed steel. M2 which offer good wear resistanceand superior toughness and machinability.

420 stainless

steel13% chromium stainless steel which will achieve a high hardness. 420

stainless steel gives a good polish and is resistant to attack fromcorrosive plastics.

1.2842 tool

steelA cold work tool steel which has high dimensional stability when heat

treated, with good resistance to cracking.

M42 highspeed steel A high quality cobalt molybdenum high speed steel, suitable corecomponents that require high hardness and superior cuttingperformance.

3.2 Properties and Technical Data for High Carbon High Chromium Steel

Chemical Composition:

Typical Analysis

C. Si. Cr. Mo. V.

1.50% 0.30% 12.00% 0.80% 0.90%

Physical Properties:

Temperature:

20C 200C 400C
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Density (kg/dm) 7.70 7.65 7.60

Coefficient of thermal expansion (per C from0C)

-11.0 x 10-

610.8 x 10-

6

Thermal conductivity (cal/cm.s C) 40.9 x 10-350.4 x 10-

3

55.2 x 10-

3

Specific heat (cal/g C) 0.110Modulus of elasticity:Kp/mm 19 700 19 200 17 650

N/mm 193 000 188 000 173 000

Forging:Heat slowly and uniformly to 700C then more rapidly to 900/1040C. After forging cool

slowly.

Annealing:Anneal at 850C and slow furnace cool. Hardness after annealing will be approx. 225 brinell.

Hardening:Pre heat slowly to 750/780C and thoroughly soak. Continue heating to the final hardening

temperature of 1000/1030C and allow the component to be heated through. Quench in oil orcool in air.

Tempering:Heat uniformly and thoroughly at the selected tempering temperature and hold for at leastone hour per inch of total thickness. Double tempering should be carried out with

intermediate cooling to room temperature.

Tempering C150 200 250 300 350 400

HRc 62/61 61/60 60/59 57/56 56/55 56/55


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Stress Relieving:If machining operations have been heavy or if the tool has an unbalanced section, removestresses before hardening by heating up to 700C, equalize then cool slowly.

Hard Chromium Plating:After hard chromium plating tempering of D2 tool steel is recommended at 180C for 4

hours to avoid hydrogen embrittlement. Tempering is to be performed immediately after

chromium plating.

Welding:Due to the high risk of crack formation welding of D2 tool steel should be avoided, ifpossible.

Mechanical Properties

PropertiesConditions

T (C) Treatment

Density (1000 kg/m3) 7.7-8.03 25

Poisson's Ratio 0.27-0.30 25

Elastic Modulus (GPa) 190-210 25

Tensile Strength (Mpa) 1158

25 oil quenched, fine grained, tempered at 425CYield Strength (Mpa) 1034

Elongation (%) 15

Reduction in Area (%) 53

Hardness (HB) 335 25 oil quenched, fine grained, tempered at 425C

Thermal properties

PropertiesConditions

T (C) Treatment


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Thermal Conductivity (W/m-K) 42.7 100

Specific Heat (J/kg-K) 477 50-100

Physical Properties

Quantity Value Unit

Thermal expansion 16 - 17 e-6/K

Thermal conductivity 16 - 16 W/m.K

Specific heat 500 - 500 J/kg.K

Melting temperature 1370 - 1400 C

Service temperature 0 - 500 C

Density 8000 - 8000 kg/m3

Resistivity 0.7 - 0.7 Ohm.mm2/m

3.3 Applications

They can be heat treated to be both tough and hard. They are used for tooling applications likeblocks in stamping dies (particularly when the dies will be used on stainless blanks) and blocks in

draw dies for forming.High carbon High Chromium tool steel gives a good hardness with added

toughness. This steelcan be vacuum hardened when minimum distortion is required.

Typical Applications for high carbon high chromium steel-

Stamping and Forming Dies Punches Forming Rolls Knives, Slitters, Shear Blades Tools Scrap Choppers Tyre Shredders


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4. Design of Die

4.1 Introduction

DESIGNING THE DIEBefore a designer begins to draw, there are a number of things which he must seriously consider. It

is now possible to list all the items which will be required before he can begin designingintelligently.

They are:

1. The part print

2. The operation sheet or route sheet

3. The design order4. A press data sheet.

In addition, he may have a reference drawing of a die similar to the one he is to design or a sketch ofa proposed design prepared by the chieftool designer or group leader suggesting a possible approach

to solution of the problem. Let us consider further the information required:

Part Print: The part drawing gives all necessary dimensions and notes. Any missing dimension

must be obtained from the product design department before workcan proceed.


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Operation Sheet: The operation sheet or route sheet must be studied to determine exactly whatoperations were performed upon the work piece previously. This is very important. When the views

of the stamping are laid out, any cuts which were applied in a previous operation must be shown.

The Design Order: This must be studied very carefully because it specifies the type of die to bedesigned.

Consider particularly the operation to be performed, the press in which the die is to be installed, and

the number of parts expected to be stamped by the die. The latter will establish the class of die to bedesigned.

The Machine Data Sheet: The die to be designed must fit into a particular press and it is importantto know what space is available to receive it and what interferences may be present.

In time you will come to realize the importance of careful and repeated study of the part print,

operation sheet, and design order because there can be no deviation from the specifications given.

DRAWINGIf the information on a drawing is complete, concise, and presented in the simplest possible manner,

the die maker can work to best advantage. The first step in originating plans for a new die is thepreparation ofasketch or sketches ofsignificant features of the proposeddie. These will become a

guide for beginning the actual full-size layout on tracing paper. However, 13 it is a mistake to spend

too much time in this phase of the workor to try to develop the entire design in sketchform becausethen decisions can become too arbitrary and inflexible. Always keep your mind open to possible

improvements as you develop the design in layout form. You will find that, often, the first or second

idea sketched out can be considerably improved by alteration as workprogresses. Often the first

idea provesentirely impractical and another method ofoperation must be substituted.Before beginning the sketch, place the part print, operation sheet, and design order before you on the

drawing table. The three must be studied together so that a complete and exact understanding ofthe

problemwill be realized. This study will form the basis for the creation of a mental picture of a tool

suitable for performing the operations - one which will meet every requirement. The sketch youmake may be a very simple one for simple operations or it may be more elaborate.

In fact, a number ofsketches may be required for more complex operations and intricate designs. In

any event,the sketch will clarify your ideas before a formal layout is attempted. In addition, it willform the basis for a realistic estimate of the size of the finished die so that you may select the proper

sheet size for the layout.

LAYOUTLaying out the die consists of drawing all views necessary for showing every component in its actual

position. In the layout stage, no dimensions are applied and neither is the bill of material nor the

record strip filled out. After the die has been laid out, the steps necessary for completing the set ofworking drawings are more or less a routine.

A properly prepared assembly drawing contains six general features:1. All views required for showing the contour of every component including the work piece.

2. All assembly dimensions. These are dimensions which will be required for assembling the parts

and those for machining operations to be performed after assembly.


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3. All explanatory notes.

4. Finish marks and grind marks to indicate those surfaces to be machined after assembly.5. A bill of material listing sizes, purchased components, materials, and number required for all

parts.

6. A title block and record strip with identifying information noted properly.

4.2 Calculations

Lames Equation for calculating the thickness of Thick Cylindrical Shells -

( )Where d = internal diameter of shell (mm)

P = internal pressure (MPa or N/mm2)

= tangential stress (MPa or N/mm2)=

(where S = ultimate tensile stress)

We design the thick cylindrical shells to be safe against tangential stress, since for thick cylindrical

shells,

Tangential Stress > Longitudinal Stress > Radial Stress

For High carbon High Chromium Steel,Ultimate Tensile Stress, S = 1757 MPa

Designing for a factor of safety = 3

Tangential Stress, = = = 585.67 MPaTherefore, = 585.67 MPa

Aluminum Powder,For compacting of Al powders, P = 300 MPa


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For compacting various Al alloys, P = 500 MPa (maximum)

Hence designing for P = 500 MPa

Internal diameter chosen for specimens, d = 19.5 mm

Final Calculations,

( )

( )

Therefore, t = 24.9587 mm

t 25 mmHence, Outer diameter, D = d + 2t

D = 19.5 + 2*25

D = 69.5 mm 70 mm

Final Dimensions as per our Design are:

Dimension Value (mm)

Internal Diameter, d 19.50

Thickness of cylindrical shell, t 25.00

Outer Diameter, D 70.00


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Note- This DIE will be safe for maximum internal pressures of 500 N/mm2

4.3 Die Design in PRO E

1. Die-


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2.Punch-


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5. Die Fabrication

5.1 Turning

Turning is a form of machining, a material removal process, which is used to create rotational parts

by cutting away unwanted material. The turning process requires a turning machine or lathe, work

piece, fixture, and cutting tool. The work piece is a piece of pre-shaped material that is secured to the

fixture, which itself is attached to the turning machine, and allowed to rotate at high speeds. The

cutter is typically a single-point cutting tool that is also secured in the machine, although some

operations make use of multi-point tools. The cutting tool feeds into the rotating work piece and cuts

away material in the form of small chips to create the desired shape.

Turning is used to produce rotational, typically axi-symmetric, parts that have many features, such as

holes, grooves, threads, tapers, various diameter steps, and even contoured surfaces. Parts that are

fabricated completely through turning often include components that are used in limited quantities,

perhaps for prototypes, such as custom designed shafts and fasteners. Turning is also commonly

used as a secondary process to add or refine features on parts that were manufactured using a

different process. Due to the high tolerances and surface finishes that turning can offer, it is ideal for

adding precision rotational features to a part whose basic shape has already been formed.


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5.2 Drilling

Drilling is acuttingprocess that uses adrill bitto cut or enlarge a hole in solid materials. The drill

bit is a multipoint, end cutting tool. It cuts by applying pressure and rotation to the work piece,

which formschipsat the cutting edge.

Drilling is the most common machining process whereby the operation involves making round holes

in metallic and nonmetallic materials. Approximately 75% of all metal-cutting process is of the

drilling operation. Drills usually have a high length to diameter ratio that is capable of producing

deep hole, however due to its flexibility, necessary precaution need to be taken to maintain accuracy

and prevent drill from breaking. Drilled holes can be either through holes or blind holes (see Figure

4.1). A through hole is made when a drill exits the opposite side of the work; in blind hole the drill

does not exit the work piece.

5.3 Boring

In machining,boring is the process of enlarging a hole that has already been drilled (or cast), by

means of asingle-point cutting tool(or of a boring head containing several such tools), for example

as in boring a cannonbarrel. Boring is used to achieve greater accuracy of the diameter of a hole,

and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart toturning, which cuts external diameters.

There are various types of boring. The boring bar may be supported on both ends (which only works

if the existing hole is a through hole), or it may be supported at one end. Lineboring (line boring,

line-boring) implies the former. Backboring (back boring, back-boring) is the process of reaching
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through an existing hole and then boring on the "back" side of the work piece (relative to the

machine headstock).

5.4 Internal Grinding

Internal cylindrical grinding is a machining process used to finish machine internal diameters to a

high degree of accuracy with a fine finish. Materials can be ground unhardened or hardened.

Internal cylindrical grinding is used to finish machine internal diameters such as bearing journals,

seal surfaces, bushes, plain bearings, cutting tool guides, jig bushes, or any internal diameter that

needs to be finished to a high level of accuracy.

In the case of materials that are hardened or coated in hard materials such as hard chrome, hard

facing alloys or ceramic, internal cylindrical grinding is often the method of choice to finish machine

the diameter to final size. Particularly in the case of intermittent cuts which can easily break ceramic

cutting tools. Internal grinding provides an easy solution.


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5.5 Oil Quenching

Rapid cooling of a material results in high internal stresses. The transformation from austenite to

martensite involves some volumetric expansion. This adds further stresses particularly in parts ofvarying cross section. These stresses together with the hard, brittle nature of martensite can besufficient to cause cracking. To avoid this, the steel is reheated to an intermediate temperature D to

soften the part to the desired hardness level. This operation known as tempering or drawing also

serves to relieve those residual stresses which otherwise would cause brittleness in the steel.If quenching is not rapid enough, the austenite reverts to ferrite and carbide E, and high hardness is

not obtained. The rate of quenching required to produce martensite depends primarily on the alloy

content. Low alloy steels require rapid cooling in water or oil, while highly alloyed steel usually canbe air-quenched at a much slower rate.

Throughout all these heat-treating reactions, most die steels retain excess or undissolved carbides,

which take no direct part in the hardening. The high carbon high-chromium steels, for example, have

large quantities of excess iron-chromium carbide, which give them in large measure the high degreeof abrasion resistance possessed by this class of steel.

Influence of Heat Treatment on Die Life

Each type of die steel must be handled slightly differently from any other for optimum results.

Different temperatures, different heating and cooling rates and variable tempering procedures must


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be used as recommended. In general, it may be said that the harder a given die, the longer it will

wear, while the softer a die is, the tougher it becomes. Assuming the proper die steel is being used,

dies which are wearing out too quickly should be made harder for improved life and dies which are

breaking or cracking should be made softer.

Within limits, heat treatment can be used to adjust these variables to best advantage. Oil-hardeningsteel may work best on one application at Rockwell C62 and on another involving higher stresses

and shock at Rockwell C58. Adjustments of the drawing temperature easily produce the hardnessdesired.

Double drawing and in some instances triple drawing is desirable for tools in severe applications.

This is because steels retain austenite when quenched. The first temper affects the martensite formed

during quenching and conditions the austenite so that it transforms upon air-cooling from the draw.

Double drawing is necessary to affect the martensite, which forms after the first draw. Triple

drawing eliminates nearly all retained austenite, further increasing toughness.

Process

Quenching metals is a progression; the first step is soaking the metal, i.e. heating it to the required

temperature. Soaking can be done by air (air furnace), or a bath. The soaking time in air furnaces

should be 1 to 2 minutes for each millimeter of cross-section. For a bath the time can range a littlehigher. The recommended time allotment in salt or lead baths is 0 to 6 minutes. Uneven heating or

overheating should be avoided at all cost. Most materials are heated from anywhere to 815 to 900 C

(1,500 to 1,650 F).

The next item on the progression list is the cooling of the part. Water is one of the most efficient

quenching media where maximum hardness is acquired, but there is a small chance that it may cause

distortion and tiny cracking. When hardness can be sacrificed, whale, cottonseed and mineral oils are

used. These often tend to oxidize and form a sludge, which consequently lowers the efficiency. Thequenching velocity (cooling rate) of oil is much less than water. Intermediate rates between water

and oil can be obtained with water containing 10-30% Ucon, a substance with an inverse solubility

which therefore deposits on the object to slow the rate of cooling.To minimize distortion, long cylindrical work pieces are quenched vertically; flat workpieces are

quenched on edge; and thick sections should enter the bath first. To prevent steam bubbles the bath

is agitated.

Effect of Oil Quenching

Before the material is hardened, the microstructure of the material is a pearlite grain structure that is

uniform and laminar. Pearlite is a mixture offerrite andcementite formed when steel or cast iron aremanufactured and cooled at a slow rate. After quench hardening, the microstructure of the material

form into martensite as a fine, needle-like grain structure.Before using this technique it is essential to look up the rate constants for the quenching of the

excited states of metal ions.

Equipment
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There are three types of furnaces that are commonly used in quench hardening: salt bathfurnace, continuous furnace and box furnace. Each is used depending on what other processes or

types of quench hardening are being done on the different materials.

Quenching media

When quenching, there are numerous types of media. Some of the more common include: air, brine

(salt water), oil and water. These media are used to increase the severity of the quench.

Quenching Distance

Quenching distance is an important property in the study of combustion. It is defined as the smallest

hole a flame can travel through. For example hydrogen has a quenching distance of 0.64 mm.


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6. Aluminum

(Metal Powder)

6.1 Introduction

The element aluminum (Al) has a specific gravity of 2.7, placing it among the light-weight structuralmetals. It is used as a base for die casting alloys with three primary constituents: silicon, copper and

magnesium. Eight available aluminum die casting alloys give the designer the widest choice among

the four primary alloy groups, and they account for the majority of die castings in terms of tons ofcomponents produced.

Seven of the eight alloys are based on the aluminum-silicon system. The eutectic (system)

composition, 11.7% silicon, is a convenient reference point for grouping them. The seven alloys arefurther grouped as either controlled copper content or restricted copper content. Other major alloying

elements in the aluminum-silicon system are magnesium and iron. Some constituents are considered

impurities, and maximum limits, expressed as a single number, are imposed.

6.2 Properties of Aluminum:

Mechanical and Performance Properties of Powder Metal Aluminum:

Powder metal aluminum parts can be produced with a range of property levels. Mechanicalproperties such as tensile strength can vary from 20 ksi (130 MPa) to 50 ksi (330 MPa) depending

upon the composition and density of the alloy, sintering practices and thermal treatments. Further

secondary processing such as hot or cold forming can yield properties approaching those ofconventional wrought aluminum materials. Powder metallurgy aluminum mechanical properties are

very good and typically are a significant factor in the material selection process.

Base

powder

Alloying

powder

YS, MPa UTS,

MPa

Elong. % RA, % Oxygen

content,

%


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Al

ASM

Standard

Al-V master

alloy

850-930

828

960-990

897

10-12.5

10

23-29

20

0.11-0.25

0.20

6.3 Why Aluminum?

Aluminum is:

Light in weight - about a third as heavy as copper or steel. Highly resistant to corrosion Strong, and it can be made stronger by alloying and heat treatment An excellent conductor of heat and electricity Nonmagnetic, a valuable property around sensitive electronics Outstanding in cryogenic properties - strong, not brittle, in intense cold Good machinability Good response to a variety of finishing processes, such as anodizing Completely recyclable (and, therefore, energy-efficient)

The combination of aluminum's light weight and moderate strength give it an excellent strength-to-

weight ratio. Aluminum offers product forms and alloys that surpass any other material. The design

flexibility of aluminum is unparalleled, allowing designers to engineer optimum shape and

performance for each specific application. Powder metal aluminum can compete successfully withless costly materials because of the advantages it brings in primary and secondary weight savings,

structural performance and design flexibility.

When you link the usual advantages of powder metallurgy to the attributes of an exceptional

material like aluminum, you have a winning combination. Aluminum powder metallurgy offers a

number of additional advantages related to the specific properties of basic aluminum.

Light Weight

Lighter weight is a distinguishing characteristic of powder metal aluminum. In fact, aluminum

enjoys better than a 3 to 1 weight advantage over iron, nickel, and copper.

Conductivity

Excellent conductivity, both electrical and thermal, is also a hallmark of powder metal

aluminum. Aluminum powder metallurgy parts are comparable to their wrought counterparts and

can be utilized as heat sinks or electrical conductors. See Figure 2 (next page) for a comparison.


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Corrosion Resistance

Powder metal aluminum alloys have excellent resistance to corrosion. In particular, the Al-Mg-Si

alloys exhibit extremely high resistance to general corrosion, when compared to ferrous-based

products. Parts may also be chromate conversion coated or anodized for increased resistance to

corrosion. Hard type anodize finishes can be applied for water-resistant applications.

Appearance

The natural appearance of powder metal aluminum parts is suitable for most applications wheregood appearance is a requirement. In addition, a wide range of decorative finishes is available. Many

of the decorative and protective treatments currently employed for wrought and cast aluminum

alloys can also be applied to aluminum powder metallurgy parts. These include mechanical finishing

and etching to achieve textures, coloring for decorative or functional purposes, electroplating, andpainting.

Machining

Powder metallurgy aluminum parts also offer many of the important advantages of wroughtaluminum in machining operations, including high cutting speeds, smooth surface finish and

superior tool life.

Joining and Bonding

Powder metal aluminum lends itself to a variety of joining and bonding techniques. Sinteredaluminum parts can be successfully fastened by adhesive bonding, although the use of threaded

fasteners is a more conventional method of joining multiple parts. Excellent thread characteristics

can be obtained in powder metallurgy aluminum parts above the 90% density level. The ductility ofparts in the upper density range is also sufficient for self-tapping fasteners.

6.4 Aluminum Alloys - Heat Treatment & Welding

Aluminum alloy die castings are not usually solution heat treated. Low-temperature aging

treatments may be used for stress relief or dimensional stability. A T2 or T5 temper may be given toimprove properties. Because of the severe chill rate and ultra-fine grain size in die castings, their

as-cast structure approaches that of the solution heat-treated condition. T4 and T5 temper results

in properties quite similar to those which might be obtained if given a full T6 temper.


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As stated above aluminum alloy die castings are not usually heat treated; however, there are heat

treatable specialty alloys available for structural applications, such as the Silafonts. Die castings arenot generally gas or arc welded or brazed; however, developments in high integrity die casting

processes coupled with specialty alloys has enabled the successful welding of die castings in specific

applications. Contact your die caster or alloy producer for more information.

6.6 Aluminum Supply

Aluminum die casting alloys are made from recycled metal. Secondary (recycled) aluminum is more

economical to produce than primary because it requires only 5% as much energy to produce apound. Current projections indicate that the supply of recycled aluminum will be adequate to meet

the needs for aluminum die casting into the foreseeable future. Used beverage cans (UBC) comprise

a large portion of the aluminum available recyclers. The supply has been enhanced by the

widespread recycling of beverage cans.1

Aluminum smelters are widely dispersed across

internationally.


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7. Specimen Manufacturing

(Powder Metallurgy)

7.1 Introduction

Powder metallurgy is concerned with the production of metal powders and converting them to

useful shapes. It is a material processing technique in which particulate material are consolidate to

semi finished and finished products. Generally the emphasis is on the metallic material but the

principal of the process apply with little modification to ceramic, polymers and a variety of

composite materials composed ofmetallicand non metallic phases. Nowadays

powdermetallictechniques are increasingly used to provide exceptional properties that are

required in highly sophisticated aerospace electronic and nuclear energy industries. However an

automobiles industry is the major consumer of powder metallurgy product today. There are two

important reasons to use powder metallurgy by industries.Productslike tungsten filament,

tungsten carbide, porous self lubricating bearings etc. are either difficult or impossible to make by

other methods. The other reason is that powder metallurgy process of manufacturing structural

components competes with other manufacturingproductssuch as casting machining and forging.

Powder metallurgy process minimizes or eliminates the machining, and scrap losses at the same

time is suited to high volume production of components. The process offers economy, savings in

energy and raw materials along with mass production of quality precision components.

Powder metallurgy is the process of blending fine powdered materials, pressing them into a desired

shape (compacting), and then heating the compressed material in a controlled atmosphere to bond

the material (sintering). Compacting is generally performed at room temperature, and the elevated-

temperature process of sintering is usually conducted at atmospheric pressure. Optional secondaryprocessing often follows to obtain special properties or enhanced precision.

Two main techniques used to form and consolidate the powder are sintering and metal injection

molding. Recent developments have made it possible to use rapid manufacturing techniques which

use the metal powder for the products. Because with this technique the powder is melted and not

sintered, better mechanical strength can be accomplished.
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The powder metallurgy process generally consists of four basic steps:

Powder manufacturing. Powder blending. Compacting. Sintering. Finishing operations.

7.2 History

Powder metallurgy principle of shapingmetallicobjects without melting from powdered materials

can be traced back to the early civilizations. These include the ancient Egyptian iron implants which

date from at least 3000 B.C. In Greece the manufacture of iron components were widespread in

800-600 B.C. The manufacture of large objects were known to Indians as early as 300A.D. and the

famous Delhi iron pillar weighing more than six tons is a typical master piece indeed . These are

processed by direct reduction of iron oxide without melting, since the technology to obtain

temperature high enough to melt pure iron was not available until about 1800. The significant

development in the use of the powder metallurgy principle took place during the early part of

nineteenth century for processing platinum and the credit to this is to be given to Wollaston in

England and Sobolevskiy in Russia. These developments ultimately led to the modern renaissance

of powder metallurgy in the beginning of twentieth century with the manufacture of tungsten

filaments for the incandescent lamp industry. The invention of electric lamp by Thomas Edison and

Swan a century ago has contributed substantially to the rapid progress of this field. Powder

metallurgy emerged as a new dimension in materials technology in twentieth century particularly

during the world war period and subsequent years. Today the technology is used advantageouslyto process advanced material for the nuclear, electronics and aerospace industries. But in modern

India the progress made in this field is mainly during the past two decades.

Thus, powder metallurgy has behind it a long and anything but straight road. However, as can be

seen from the present review, its history has received little study. The historical notes in the books

considered above provide merely a background or introduction to the analysis of each specific

topic. Yet it is precisely today, when the role of powder metallurgy has grown so enormously, that


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it is particularly important to discover links between present-day practice and historical experience.

A thorough study should be made of all the relevant facts, events, and scientific ideas of the past,

involving their objective interpretation, precise documentation, and full analysis.

Basic Flow chart of Powder Metallurgy

7.3 Powder Manufacturing or Atomization

Atomization is accomplished by forcing a molten metal stream through an orifice at moderate

pressures. A gas is introduced into the metal stream just before it leaves the nozzle, serving to

create turbulence as the entrained gas expands (due to heating) and exits into a large collection

volume exterior to the orifice. The collection volume is filled with gas to promote further

turbulence of the molten metal jet. On Earth, air and powder streams are segregated using gravity

or cyclonic separation. Most atomized powders are annealed, which helps reduce the oxide and

carbon content. The water atomized particles are smaller, cleaner, and nonporous and have a

greater breadth of size, which allows better compacting.

Metal PowderPreparation

Blending Compaction

Sintering

START

STARTAuxiliary

Operations


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7.4 Zinc stearate as Lubricant

Zinc stearate(Zn(C18H35O2)2) is a zinc soap that repels water. It is insoluble in polar solvents such

as alcohol and ether but soluble in aromatic hydrocarbons (e.g.,benzeneand chlorinated

hydrocarbons) when heated. It is the most powerful mold release agentamong all metal soaps. It

contains no electrolyte and has a hydrophobic effect. Its main application areas are the plastics and

rubber industry where it is used as a releasing agent and lubricant which can be easily

incorporated.

Structural Formula:

Applications of Zinc Stearate:

As a synergic stabilizer for Ba/Cd and Pb stabilizer systems. As a gloss imparting agent in paint industry. As a metal release agent in rubber, polyurethane and polyester processing system. As a die release agent inpowder metallurgy. As a chief ingredient in "fanning powder", used by magicians performingcard

manipulationto decrease the friction between the cards.

As a lubricant in cosmetics to improve texture. As an activator system for rubber vulcanization by sulfur and accelerators.
http://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Benzenehttp://en.wikipedia.org/wiki/Benzenehttp://en.wikipedia.org/wiki/Benzenehttp://en.wikipedia.org/wiki/Mold_release_agenthttp://en.wikipedia.org/wiki/Mold_release_agenthttp://en.wikipedia.org/wiki/Mold_release_agenthttp://en.wikipedia.org/wiki/Powder_metallurgyhttp://en.wikipedia.org/wiki/Powder_metallurgyhttp://en.wikipedia.org/wiki/Powder_metallurgyhttp://en.wikipedia.org/wiki/Card_manipulationhttp://en.wikipedia.org/wiki/Card_manipulationhttp://en.wikipedia.org/wiki/Card_manipulationhttp://en.wikipedia.org/wiki/Card_manipulationhttp://en.wikipedia.org/wiki/Card_manipulationhttp://en.wikipedia.org/wiki/Card_manipulationhttp://en.wikipedia.org/wiki/Powder_metallurgyhttp://en.wikipedia.org/wiki/Mold_release_agenthttp://en.wikipedia.org/wiki/Benzenehttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Zinc


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Specifications:

Characteristics Properties

Appearance White Fine Powder

Melting Point 120C - 124C

Solubility Insoluble in Water, Ethanol & Ether

Moisture Content Less than 2%.

Total Ash Content Between 14-16%.

Free Stearic Acid Less than 3%.

Zinc Content (as ZnO) 13-15 %

Bulk Density App.0.10 Gm/CC

Fineness through 240 mesh 99% passes

pH 6.57.5

7.5 Powder Blending

Blending and mixing are carried out to achieve uniformity of the product manufactured. Distribution

of properly sized particles is attained by mixing elementary powder with alloy powders to obtain ahomogeneous mixture. Lubricants are also mixed with powders to minimize the wear of dies and

reduce friction between the surfaces of dies and the particles of powder during compaction. Mixingtime depends upon the results desired, and over-mixing should be prevented, or otherwise the size ofparticles will be decreased, and they will be hardened.


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Horizontal Ball Mill (Tumbler ball mill):

Specifications:

Diameter: 320 mm (Approx.) Width: 120 mm (Approx.) Speed: 100 rpm (Approx.) (With speed regulator) Material of the ball mill: Stainless steel Material of Balls: Stainless steel. Two or three different diameter balls should be provided. Extra balls should be provided to replace for the worn out balls. Hose pipes for filling Argon gas should be provided. Provision for filling Argon gas for creating inert atmosphere through non return valves in the

ball mill is available.

7.6 Powder Compaction

Powder compaction is the process of compacting metal powder in a die through the application of

high pressures. Typically the tools are held in the vertical orientation with the punch tool forming thebottom of the cavity. The powder is then compacted into a shape and then ejected from the die

cavity. In a number of these applications the parts may require very little additional work for their

intended use; making for very cost efficient manufacturing. The cavity of the die is filled with aspecified quantity of blended powder, necessary pressure is applied, and then the compacted part isejected. Pressing is performed at room temperature; the pressure depends upon the material,

properties of the powder used, and the density required of the compaction. Friction between the

powder and the wall of the die opposes the pressure applied; the pressure decreases with depth and

causes uneven density in the compact. Thus the ratio of length and diameter is kept low to preventsubstantial variations in density.


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There are four major classes of tool styles: single-action compaction, used for thin, flat components;

opposed double-action with two punch motions, which accommodates thicker components; double-action with floating die; and double action withdrawal die. Double action classes give much better

density distribution than single action. Tooling must be designed so that it will withstand the extreme

pressure without deforming or bending. Tools must be made from materials that are polished and

wear-resistant.

Die compaction represents the most widely used method and is considered as the conventional

technique. This involves rigid dies and special mechanical or hydraulic presses. Densities of up to 90% of full density can be achieved following the compaction cycle, the duration of which may be of

the order of just a few seconds for very small parts.

Powders do not respond to pressing in the same way as fluids and do not assume the same densitythroughout the compact. The friction between the powder and die wall and between individual

powder particles hinders the transmission of pressure. A high uniformity in green parts can be

achieved depending on:

the kind of compacting technique

the type of tools

the materials to be pressed and the lubricant.

The compacting techniques used may be characterised by references to the movement of theindividual tool elementsupper punch, lower punch and die relative to one another.

Pressing within fixed dies can be divided into:

Single action pressing

Double action pressing

In the former the lower punch and the die are both stationary. The pressing operation is carried out

solely by the upper punch as it moves into the fixed die. The die wall friction prevents uniform


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pressure distribution. Compact has a higher density on top than on the bottom. In the latter type of

pressing only the die is stationary in the press. Upper and lower punches advance simultaneouslyfrom above and below into the die (Fig.5.1). The consequence is high density at the top and

undersides of the compact. In the centre there remains a neutral zone which is relatively weak.

Pressing Operation:

The pressing operations can be sequenced as follows:

1. Filling of the die cavities with the required quantity of powder.2. Pressing in order to achieve required green density and part thickness.

3. Withdrawal of the upper punch from the compact: Here the risk of cracking of green parts is

felt. As the upper punch withdraws, the balance of forces in the interior of the die ends. In the caseof parts with two different thicknesses, e.g. flange with a hub, the elastic spring back of the lower

punch is the greatest danger. Other problems are protrusions required on the upper face of the part.

In the case of thin parts with large projected area, cracking is common due to elastic spring back of

the lower punch and the part itself. The former pushes the part still lying in the die cavity upwards,

while the latter tends to expand the part.

Ejection:

The tooling must be done in such a manner so that the ejection of part is feasible. Ejection of a part

of complex forms is rather problematic, as it involves friction between the green part and tool walls.The green strength must be high to resist the bending stresses introduced by the ejection force.

There is another type of compaction involving upper punch pressing with floating die. This is

characterized by a stationary lower punch the upper punch moves into a die supported by spring. As

soon as the friction between the powder and the die wall exceeds the spring power, the die wall iscarried down. The friction will vary slightly from stroke to stroke. It also depends on the degree of

wear in the tools so that a constant density distribution is difficult to maintain over a period.

During second world war another tooling method was developed in Germany, known as

withdrawal tooling. In this case, the lower punch does not move during compacting cycle. Afterthe upper punch has entered the die cavity, both upper punch and die plate move downwards. After

the compact has been pressed, the upper punch moves up but the die plate and lower coupler move

further down until the top of the die plate is flush with the lower punch. The compact is ejected andcan be moved out of the way by the loading shoe. Die plate and lower coupler then move back into

the filling position and the cycle repeats.

The major advantage of withdrawal system of tooling is that the lower punches are relatively shortand are well supported during compaction and ejection. When there are multiple lower punches, as

many of them as possible rest directly on the base plate. Withdrawal tooling can be built for very

complex parts. On the other hand, in the tooling system with ejection by the lower punches the

motions of the punches are built into the multiple action presses. In many cases no tool holders arerequired.


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7.7 Sintering

Solid state sintering is the process of taking metal in the form of a powder and placing it into a mold

or die. Once compacted into the mold the material is placed under a high heat for a long period of

time. Under heat, bonding takes place between the porous aggregate particles and once cooled thepowder has bonded to form a solid piece.

Sintering can be considered to proceed in three stages. During the first, neck growth proceeds

rapidly but powder particles remain discrete. During the second, most densification occurs, thestructure recrystallizes and particles diffuse into each other. During the third, isolated pores tend to

become spheroidal and densification continues at a much lower rate. The words Solid State in Solid

State Sintering simply refer to the state the material is in when it bonds, solid meaning the materialwas not turned molten to bond together as alloys are formed.


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One recently developed technique for high-speed sintering involves passing high electrical current

through a powder to preferentially heat the asperities. Most of the energy serves to melt that portionof the compact where migration is desirable for densification; comparatively little energy is absorbed

by the bulk materials and forming machinery. Naturally, this technique is not applicable to

electrically insulating powders.

To allow efficient stacking of product in the furnace during sintering and prevent parts sticking

together, many manufacturers separate ware using Ceramic Powder Separator Sheets. These sheets

are available in various materials such as alumina, zirconia and magnesia. They are also available infine medium and coarse particle sizes. By matching the material and particle size to the ware being

sintered, surface damage and contamination can be reduced while maximizing furnace loading.

CONTROLLED ATMOSPHERE FURNACE SPECIFICATIONS:

1. Maximum temperature: 1500 C2. Dimension of Heat Zone: Diameter = 100 mm, Length = 180 mm3. Length of Furnace = 500 mm (Approx.)4. Arrangement to remove the air by vacuum pump and purge the inert gas (Argon).5. Provision to run the furnace at vacuum, without purging inert gas, with vacuum pump

continuously on while heating.

6. Cooling arrangement for gas or air before entering the vacuum pump.7. Suitable vacuum pump (10-3 torr vacuum).8. Provision to measure the vacuum.9. The furnace should be programmable to control the rate of heating and cooling.


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10.Arrangement to set at maximum desired temperature.11.One Argon cylinders (for inert gas supply).12.One argon regulator for Argon cylinder and Hoses.13.Outside skin temperature of furnace should be as low as possible (not more than 60 C).14.Guarantee of 3 years.

7.8 Powder Metallurgy using Aluminum

Increased demand for light weight components, primarily driven by the need to reduce energy

consumption in a variety of societal and structural components, has led to increased use of

aluminum. Additionally, the cost of fabrication coupled with a need to improve part recovery has led

to significant growth in the net-shaped component manufacturing processes.

Aluminum Powder Metallurgy (P/M) offers components with exceptional mechanical and fatigue

properties, low density, corrosion resistance, high thermal and electrical conductivity, excellent

machinability, good response to a variety of finishing processes, and which are competitive on a costper unit volume basis. In addition, aluminum P/M parts can be further processed to eliminate

porosity and improve bonding yielding properties that compare favorably to those of conventional

wrought aluminum products.

The primary driver for the use of aluminum P/M is the unique properties of aluminum coupled with

the ability to produce complex net or near net shape parts which can reduce or eliminate the

operational and capital costs associated with intricate machining operations. Aluminum P/M can

replace other P/M in certain applications on a direct basis. However, in terms of the potential forferrous based product substitution, each potential application needs to be considered on a case by

case basis.Typical economics tend to favor iron parts but the unique characteristics of aluminum such as

strength, weight, corrosion resistance, and machinability can make the aluminum parts economically

viable.

The aluminum P/M process consists of three basic steps:

1. Aluminum powders of controlled purity and particle size are mixed with alloying metal powders

in precisely controlled quantities. Generally a powdered lubricant is added to permit the consistentproduction of high density parts without seizing of the punches or cold welding to the die walls.

This lubricant is carefully chosen to ensure that there is no residual ash to interfere with bonding

during sintering.

2. The premix is compacted using precision metal dies in specially designed P/M presses to yield a

green compact. Aluminum premixes exhibit excellent compressibility and yield high density parts at

low compaction and ejection pressures. Premixes can be compacted to 90% density at only 12 tsi


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and 95% at 25 tsi. Typical green strengths range from 450 to 1500 psi which is sufficiently strong to

withstand normal handling without chipping or breaking.

3. The green compacts are sintered in a controlled atmosphere furnace at closely regulated

temperatures. This process metallurgically bonds the powder particles together and develops the

desired physical and mechanical properties. Aluminum powder sintering is difficult to achievebecause the aluminum oxide is not reduced by common furnace atmospheres at sintering

temperatures. However, successful sintering is accomplished in environments containing hydrogen,

nitrogen and dissociated ammonia as long as the following conditions are observed:

The lubricant is essentially free of moisture and low in ash contact. Atmospheres contain low levels of moisture and oxidizing gases. Alloying elements having a high solubility in aluminum are added to generate low melting

phases.

Most aluminum P/M alloys are sintered between 1000 and 1200F with a sintering time of 7 to 20

minutes. The recommended atmosphere is nitrogen with a furnace dew point range of -40 to -60F.

Higher dew points yield reduced properties and very high dew points can result in gross expansion

of the compact.

7.9 Aluminum comparison to other P/M materials


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A direct comparison of mechanical properties of aluminum P/M with ferrous based products reveals

that, like its wrought aluminum counterpart, has lower, but competitive, strength levels. However,there are many major property advantages associated with aluminum P/M alloys.

A major advantage is the density of aluminum which is translatable into many property, processing

and economic benefits. Parts will weigh less and relatively small changes in part dimensions can

yield bulk properties comparable to the ferrous based parts while still maintaining an overall weightadvantage. This is a major benefit in todays energy conscious world. In addition, because of the

lower density, the relatively high cost per pound of aluminum P/M raw materials becomes lesssignificant and more competitive with typical P/M materials, when considered on a cost per unit

volume or individual part weight basis. This lighter weight can also be translated into a potentially

higher volume of parts per inch of belt in the sintering operation (i.e., greater productivity), and also

lowers shipping costs.

Other significant property advantages associated with aluminum P/M include corrosion resistance,

conductivity and finishing characteristics. The excellent corrosion resistance of aluminum alloys has

been well established through years of experience in marine, aerospace and chemical industryapplications. In normal outdoor exposure aluminum P/M alloys will provide corrosion resistance

equivalent to brass, bronze and stainless steel P/M parts and significantly better than ferrous based

products. This corrosion resistance also means that no special coatings are necessary for normalshipping and storage. Aluminum has excellent conductivity values, both thermal and electrical.

Aluminum P/M is comparable to its wrought counterparts and significantly better than brass, bronze

and ferrous based materials. The natural appearance of aluminum P/M parts after chemical ormechanical cleaning is suitable for most applications where good appearance is a requirement. In

addition, a wide range of decorative and functional finishes are available with aluminum P/M that

are not possible with other P/M materials.

Aluminum P/M also offers economic advantages in the parts fabrication area. These blends exhibit

excellent compressibility and yield high density parts at low compaction and ejection pressures.

Aluminum P/M blends can be compacted to 90% theoretical density at only 12 tsi and 95% at 25 tsiwhich is much lower than comparable ferrous based materials. These lower pressures permit the use

of smaller, faster presses to produce larger parts and in some cases allow the use of multiple cavity

tooling.

Lower compaction pressures reduce the possibility of damage in fragile tool designs and tool

breakage is less likely with aluminum. Sintering temperatures for aluminum P/M parts are much

lower (1100-1200F) than other P/M parts (>2000F). This yields significant energy savings in the

production process. The sintering in presence of atmospheric gases for aluminum part productionalso tends to be more economical. The atmosphere of choice for aluminum tends to be low dew

point nitrogen while other P/M parts use a combination of hydrogen (5-15%) and nitrogen. Sincehydrogen gas is 3-4x more expensive than nitrogen, the use of nitrogen alone can translate into

further cost savings. Aluminum P/M parts offer many advantages over other P/M products. In

addition to properties such as low density, thermal and electrical conductivity, finishingcharacteristics and corrosion resistance not available with other P/M products, aluminum can be

economically viable on a direct part replacement basis. An analysis of a hypothetical P/M flange


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part with a flange diameter of 1 inch and the length of 0.06 inches coupled with an overall length and

body OD of 0.75 inches suggests a 30% lower cost than 316L SS, a 20% lower cost than Bronze 90-10 and a comparable cost with FC0008 at a density of 6.6.

8. Testing Of Specimens

8.1 Introduction to Universal Testing Machine (UTM):

A universal testing machine, also known as a universal tester,materials testing machine or materials

test frame, is used to test the tensile stress and compressive strength ofmaterials. It is named after

the fact that it can perform many standard tensile and compression tests on materials, componentsand structures.
http://en.wikipedia.org/wiki/Physical_testhttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Materialshttp://en.wikipedia.org/wiki/Materialshttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Tensile_stresshttp://en.wikipedia.org/wiki/Physical_test


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Components:

Load frame - usually consisting of two strong supports for the machine. Some small machineshave a single support.

Load cell - A force transducer or other means of measuring the load is required.Periodic calibration is usually called for.

Cross head - A movable cross head (crosshead) is controlled to move up or down. Usually this isat a constant speed: sometimes called a constant rate of extension (CRE) machine. Some

machines can program the crosshead speed or conduct cyclical testing, testing at constant force,

testing at constant deformation, etc. Electromechanical, servo-hydraulic, linear drive, and

resonance drive are used.

Means of measuring extension or deformation- Many tests require a measure of the response ofthe test specimen to the movement of the cross head. Extensometers are sometimes used.

Output device - A means of providing the test result is needed. Some older machines have dial ordigital displays and chart recorders. Many newer machines have a computer interface for

analysis and printing. Conditioning

Documents

Design and Fabrication of DIE for Comp Action of Metal Powder in Powder Metallurgy