A presentation on

FUNDAMENTALS OF METAL WORKING

Submitted by:Raghav Saxena2014PMT5403

Submitted to:Dr. V K SharmaAssociate ProfessorMNIT,Jaipur

Department of Metallurgical & Materials Engineering

What is Metal

Working?

Metalworking is the process

of working with metals to

create individual parts,

assemblies, or large-scale

structures.

Useful shapes in metal can be

generated in two basic ways:

By plastic deformation process

i.e. Metal Forming Process (Example- Forging,

Rolling, Extrusion, etc.)

By metal removal or machining process

(Example- Shaping, milling, etc.)

Classification of Metal working

processes on the basis of the type of

forces applied:

Direct compression type processes

Indirect compression processes

Tension type processes

Bending processes

Shearing processes

Direct compression type processes:

Force is applied to the surface of the work piece,

and the metal flows at right angle to the direction

of the compression.

Examples: Forging, Rolling, etc.

Indirect compression processes:

The primarily applied forces are tensile, but the

indirect compressive forces developed by the

reaction of the work piece with the die reach

high values.

Examples: Wire Drawing, Tube Drawing, Extrusion,

Deep Drawing, etc.

Tension type processes:

The primary force for this type of process is Tension

force.

Example: Stretch Forming, etc.

Bending processes:

This process involves the application of bending

moments to the sheet.

Example: Bending, etc.

Shearing processes:

This process involves the application of shearing

forces of sufficient magnitude to rupture the

metal in the plane of shear.

Example: Sheet metal operations like Blanking,

Piercing, etc.

Factors affecting

metal working:

Flow stress

Temperature

Strain Rate

Metallurgical Structure

Friction

Lubrication

Composition

Flow stress:

Flow stress is the true stress acting inside the

material.

It differs from engineering stress as it takes into account the changes in the dimensions of the

work piece.

To accurately predict the forming loads, we need

accurate values of stresses i.e. flow stress.

Flow curve is desirable to be drawn for actual

working conditions as the operations involve large

plastic strains.

Temperature:

On the basis of temperature, forming processes

are classified into Hot-working, Cold-working, &

Warm-working operations.

Hot working of metals is defined as deformation of

metal above recrystallization temperature, so that

recovery processes takes place simultaneously.

Cold Working of metals is defined as working of metals below recrystallization temperature, so that no recovery process is possible.

Warm Working of metals is plastic deformation of metal at temperature above room temperature but below recrystallization temperature.

If a metal is cold worked, its strength increases & ductility decreases with increase in percentage cold worked.

If a metal is hot worked, its strength decreases but ductility increases with increase in annealing temperature.

Strain Rate Effects:

Flow stress of metal increases with strain rate.

Temperature of the work piece is increased because of adiabatic heating.

Improved lubrication at tool-metal interface.

Metallurgical Structure:

The presence of preferred orientation causes

anisotropy of mechanical properties.

If the work piece is an alloy, the structure of other phases present inside the alloy may cause

softening or hardening.

Precipitation occurs with time & it changes the

mechanical properties depending upon their

nature.

These alterations in mechanical properties

ultimately changes flow stress.

Friction

Friction is the force resisting the relative motion of

solid surfaces, fluid layers, and material elements

sliding against each other.

It changes the normal pressure distribution over a

work piece & sometimes perform cold welding.

In hot working, sticking friction (where there is no relative motion between work piece & tool) is a

usual case.

Lubrication

Extra forces can be avoided if we use proper

lubrication.

Cold welding & heating is controlled when there exists a lubrication film between the tool-job

interface.

It improves surface finish of the product & thus

saving extra cost for finishing.

Boundary lubricants with extreme pressure (EP)

must be added to the fluid to form a boundary

film at the interface.

Composition:

The dependency of required load & mechanical

properties undoubtedly depends of the

composition of the job.

Metal with different alloying elements shows an

entirely different range of properties.

To attain desired characteristics, proper

composition of work piece must be selected with

minimum amount of impurities.