METAL FORMING PROCESSES

1. METAL FORMING PROCESSES
Hot working and cold working of metals – Forging processes – Open,
impression and closed die forging – Characteristics of the process – Types of
Forging Machines – Typical forging operations – Rolling of metals – Types
of Rolling mills - Flat strip rolling – Shape rolling operations – Defects in
rolled parts - Principle of rod and wire drawing -Tube drawing –– Principles
of Extrusion – Types of Extrusion – Hot and Cold extrusion – Equipments
used.

2. HOT WORKING OF METALS
Mechanical working of a metal above the recrystallization temperature
but below the melting point.
Plastic deformation of metals and alloys under the condition of
temperature and strain rate.
Recrystallization temperature is 30 to 40% of melting temperature.
In this process, Metal is heated above the RT with 0.7 to 0.9 times of the
melting temperature.
TYPES OF HOT WORKING PROCESS
-Hot forging
-Hot Rolling
-Hot Extrusions
-Drawing
-Swaging
-Hot Spinning

3.  Advantages:
 Force requirement is less when compared to cold working
process
 As grain structure is refined, toughness, ductility and
resistance can be improved
 It is quick and economical process
 Porosity is eliminated and density of the metal is
increased
 Suitable for all metals
 Disadvantages:
 Surface finish may be poor due to oxidation and scaling
 Close tolerance and automation cannot be achieved due
to high working temperature.

4. COLD WORKING OF METALS
Plastic deformation of a metal to the required shape being performed
below the recrystallization temperature.
Process will work under room temperature.
RT – “Minimum temperature at which the complete recrystallization of
a metal takes place with in a specified time”
Materials used for Cold Working Process:
 Low and medium carbon steel.
Copper and light alloys
Materials such as Al, Mg, Titanium
Types of cold working processes:
Drawing
Squeezing
Bending

5. 1.Cold Drawing
- Blank Drawing
Cutting a flat shape from the metal.
-Tube Drawing
Tube piercing is called tube drawing
-Embossing
Process of making raised or projected design
on the surface of the metal.
Producing nameplates tags & designs on the
metal.
-Wire Drawing
Diameter less than 16mm has drawn in the
form of wire coil.
-Metal Spinning

6. 2.0 Squeezing
- Coining
It is used for the production of metals and
coins. Coining process consists of die &
punch.
-Sizing
Size the metal to required shapes
-Swaging
It is used for producing rounded
components through radial impact forces
by reciprocating dies.
Workpieces having low ductility at room
temp. Maximum stock dia 150mm.
-Knurling
The rolls are pressed radially against the
rotating work piece, to make grip on the
handles.

7. 3.0 Bending
Bend into Desired shape like rods, wires, bars
- Plate Bending
Large Plates are bent to shapes
- Roll Forming
-It carries three rolls, Two are fixed and the third one is adjustable.
Diameter of all rolls are same.
- Angle Bending
Angles, Circles, Ovals

8.  Advantages:
 It is widely applied as a forming process for steel
 Better surface finish is being obtained
 This process provides higher dimensional accuracy
 Thin material can be obtained
 It is more suitable for mass production
 Disadvantages:
 The surface finish may be poor
 Close tolerances cannot be achieved
 Stress formation in the metal during cold working is
higher

9. FORGING PROCESSES
The desired shape is obtained by the application of a compressive force.
Types
1.0 Smith or Open die Forging
The forging is done in a heated work at the proper temperature by
placing on flat surface anvil through hammering the metal piece.
a) Hand Forging
b) Power Forging

10. 2.0 Closed die Forging
a) Drop Forging

11. b) Press Forging
Applications

12. c) Upset Forging
3.0 Roll Forging

13. Press forging Drop forging
1 Faster process Slow process
2 Alignment of dies is easier Alignment of dies is very difficult
3 Quite operation Noisy operation
4 Structural quality of the product is
superior
Not superior
5 Simple maintenance Maintenance is difficult
6 The output is high It requires skilled

14. TYPES OF FORGING MACHINES
1.0 Air and Steam Hammer
a) Air Hammer
It using air or steam.
- Single acting hammer – Air pressure is used to lift the ram only.
- Double acting hammer – Air pressure is used to lift the ram and
Impact the work piece.

15. 1.0 Air and Steam Hammer
b) Steam Hammer
It using air or steam.
- Single acting hammer – Air pressure is used for light work.
- Double acting hammer – Air pressure is used for heavy work.

16. 2.0 Mechanical Hammer
a) Helve Hammer
b) Trip Hammer
The reciprocating ram is the main part and it is toggle. The stroke length
various from 175 to 400blows/min.

17.  Power presses:
 Presses involve slow squeezing of plastic metal in closed
impression dies instead of applying repeated severe blows
by hammers.
 Production of forging is the whole operation is completed
in a single squeezing action.
 Main parts of the power press are accumulator and
distributor
 Pressurized water from the pump is delivered on the press
through accumulator and distributor.
 The ram is forced down upon the material to be forged in
the forward stroke.
 Return stroke of the press relatively lower the water
pressure, but large volume of water per unit time is
required to accelerate the ram.

18. TYPES OF FORGING OPERATIONS
1.0 Upsetting
The metal is heated at one end and the force is applied on the other
end by using hammer. The cross sectional area will increase and length will
decrease. Designed that the complete operation is performed in several
stage and the final

19. TYPES OF FORGING OPERATIONS
3.0 Punching
In this process, making of a hole in a
given job.
4.0 Bending
In this process, shapes like angles,
ovals and circle can be made.
2.0 Drawing Down
In this process, the cross
sectional area will decrease and length will
increase.

20. 2.0 Mechanical Hammer
c) Level Spring Hammer
d) Pneumatic Hammer
An elastic rod is used to operate the ram. The stroke length various from 40
to 200blows/min.

21. TYPES OF FORGING OPERATIONS
6.0 Forge Welding
Joining the work pieces by forging
operation.
7.0 Piercing
Making a blind or through holes with the help of a punch in the metal.
5.0 Cutting
Removal of excess metal from the work.

22. TYPES OF FORGING OPERATIONS
8.0 Swaging
Reducing or changing the cross sectional area of the metal.
9.0 Flattering
Used to flat the stock and that the stock is fitted properly in the closed die.
10.0 Fullering
Reducing the stock and increasing the length of the work piece by applying
pressure.

23. ROLLING OF METALS
Deforming the metal into semi finished or finished condition by passing the metal
piece in between the two rollers.

24. FLAT STRIP ROLLING

25. FLAT STRIP ROLLING

26. Classification of Rolling Based on Number of Rolls
1.0 Two high rolling mill 2.0 Three high rolling mill

27. Classification of Rolling Based on Number of Rolls
3.0 Four high rolling mill 4.0 Multiple roll mills

28. Classification of Rolling Based on Number of Rolls
5.0 Universal rolling mill

29. SHAPE ROLLING OPERATIONS
Straight and long structural shapes, solid bars, I –Beams, Channels, Railroad rails.

30. SHAPE ROLLING OPERATIONS
1.0 Ring rolling
A thick ring is expanded into a large diameter ring with a reduced cross
section. The ring is placed in between two rolls and one of the roll is driven , ring
thickness is reduced.
Advantages:
-Close tolerances
-Material Saving
- Short production times

31. SHAPE ROLLING OPERATIONS
2.0 Thread rolling
Straight or tapered threads are formed. Threads are formed on the rod ,
with each stroke of a pair of flat reciprocating dies
Advantages:
-Surface finish
good
-Long life
- Thread strength
is good

32. DEFECTS IN ROLLED PARTS
1.0 Surface Defects
It includes scale, rust, cracks and pits due to impurities and inclusion
2.0 Internal Structural Defects
Strain on the material should adjust.

34. DEFECTS IN ROLLED PARTS
3.0 Other Defects
a) Homogeneous deformation of element across the width
Due to decrease in thickness for the elements near the centre will be mainly converted
into increase in length and near the edge the decrease in thickness is converted into
lateral spread.
b) Homogeneous deformation in the thickness section
Due to reduction in height is converted into increase in length and the thickness of the
sheet does not undergo the same lateral deformation.
c) Folds
It is created during plate rolling if the reduction per pass is very small.
d) Lamination
Due to incomplete welding of pipe and blowholes during the rolling process the internal
defects such as fissures are created.

35.  PRINCIPLE OF DRAWING:
 This process is used to reduce the diameter of metal is
called drawing.
 It is cold working process in which the material to the
drawn is pulled through a tapered hole in a die.
 In this process requires very high force to pull the metal
through the die.
 Applications:
 To produce round, rectangular square and hexagonal
shapes.
 Electrical wire, wire frame structures
 To make hydraulic systems of vehicles and industrial
machineries.

36. CLASSIFICATION OF DRAWING
1.0 WIRE DRAWING
Diameter less than 16mm has drawn in the form of wire coil.

37. CLASSIFICATION OF DRAWING
2.0 ROD DRAWING
Placing the hot drawn bar through a die of which the bore size conforms to the
finished size of product.

38. CLASSIFICATION OF DRAWING
3.0 TUBE DRAWING
Cylinders and Tubes are made by extrusion process.
a) Tube Sinking b) Tube mandrel

39. CLASSIFICATION OF DRAWING
3.0 TUBE DRAWING
c) Tube Plug

40. CLASSIFICATION OF DRAWING
4.0 DEEP DRAWING
To draw the cup shaped parts from the metals.

41. EXTRUSION
Heated metal is compressed
and forced through a suitable
shaped die – Hot Extrusion.
Cold extrusion is non heated
metal but force is required
and used for commercial
metals.

42.  Hot Extrusion:
 Metals such as lead, copper, Al and Mg are having low
yield strength and extrusion temp
 This process is hydraulically operated.
 The sizes are rated from 250 to 5500 tones.
 Presses are used in hot extrusion process.
 Steel is most extruded at high temp.
 Hot extrusion process has following characteristics:
 No fracture of metal is due to tensile stress
 Extrusion size depends upon the size of the cylinder.
 Hollow shapes can also be extruded.
 Types:
 Forward or direct extrusion
 Backward or indirect extrusion.

43. TYPES OF EXTRUSION
1.0 HOT EXTRUSION
a) Forward or direct extrusion.

44. TYPES OF EXTRUSION
1.0 HOT EXTRUSION
b) Backward or Indirect extrusion.

45. TYPES OF EXTRUSION
2.0 COLD OR IMPACT EXTRUSION

46.  Work material placed between the die and ram
 The punch is connected with the ram
 Sudden impact is given to the ram, the metal flows
plastically in the upward direction.
 Metals – Al , tins
 Various items of daily use such as tubes for saving
creams, tooth pastes and paints, condenser cans and
thin walled products.
 When the punch moves up, the compressed air is used
to separate the component from the punch.
 Advantages: speeds up the product uniformly and
lowers scrap yield.