Fundamentals of metal or mechanical working. Reference- Mechanical Metallurgy by George Dieter

1. A presentation on
FUNDAMENTALS OF METAL WORKING
Submitted by:
Raghav Saxena
2014PMT5403
Submitted to:
Dr. V K Sharma
Associate Professor
MNIT,Jaipur
Department of Metallurgical & Materials Engineering

2. What is Metal
Working?
Metalworking is the process
of working with metals to
create individual parts,
assemblies, or large-scale
structures.

3. 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.)

4. 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

5. 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.

6. 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.

7. Tension type processes:
 The primary force for this type of process is Tension
force.
 Example: Stretch Forming, etc.

8. Bending processes:
 This process involves the application of bending
moments to the sheet.
 Example: Bending, etc.

9. 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.

10. Factors affecting
metal working:
 Flow stress
 Temperature
 Strain Rate
 Metallurgical Structure
 Friction
 Lubrication
 Composition

11. 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.

12. 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.

13.  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.

14.  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.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.