2. Hot working and cold working of metals –
Forging processes – Open, impression
and closed die forging – forging
operations. Rolling of metals– Types of
Rolling – Flat strip rolling – shape rolling
operations – Defects in rolled parts.
Principle of rod and wire drawing – Tube
drawing – Principles of Extrusion – Types
– Hot and Cold extrusion.YoucaN
9. • Forming ???....
Forming, or metal forming, is the
metalworking process of fashioning metal
parts and objects through mechanical
deformation.
The workpiece is reshaped without adding
or removing material, and its mass
remains unchanged.
YoucaN
10. • Metal forming process Is an economical
process to obtain desired shape form the
given material.
• To improve mechanical properties (bez it
improves microstructure & directional grain flow)
• To minimize defects such as holes, crack
etc.
• To distribute impurities equally in metal.
YoucaN
11. • Die- The die is a metal block that is used for forming
materials like sheet metal and plastic.( hot worked tool
steels, medium carbon alloy steels)
a) Reducing the thickness of the bar by
hammering YoucaN
12. • Forge- Make or shape (a metal object) by heating it in a
fire or furnace and hammering it.
YoucaN
13. • Forge- Make or shape (a metal object) by heating it in a
fire or furnace and hammering it.
(Closed die forging)
YoucaN
15. • Recrystallization is a process by which deformed grains are
replaced by a new set of defects-free grains that nucleate and
grow until the original grains have been entirely consumed.
YoucaN
16. • Toughness
It is the ability of a material to absorb energy and plastically
deform without fracturing
YoucaN
17. • Ductility
It is the ability of a solid material to deform under tensile
stress.
YoucaN
18. • Hot forging
• Forging operation is carried at elevated or warm
condition.
• Here lower forces are used.
YoucaN
19. • Cold forging
• Cold Forging operation is carried at less than recrystallize
temperature. Mostly it is done in room temperature (400
C).
• Here higher forces are used.
YoucaN
20. • Casting: There is no grain flow, so that it has poor
mechanical properties.
• Machining: Here the fibre is affected by interrupted due to
machining.
• Forging: The fibre of the metal has not been interrupted
and continues along the entire length.
YoucaN
21. YoucaN
When you melt metal to cast it, the grain size is free to expand.
When it cools back to a solid, the grain structure is courser and
more random, decreasing its strength.
Forged parts had a 26% higher tensile strength than the cast
parts. This means you can have stronger shackles at a lower
part weight.
Forged parts have a 37% higher fatigue strength resulting in
a factor of six longer fatigue life. This means that a forged
shackle is going to last longer.
Cast iron only has 66% of the yield strength of forged steel.
Yield strength is an indicator of what load a shackle will hold
before starting to deform.
The forged parts had a 58% reduction in area when pulled to
failure. The cast parts only had a 6% reduction in area. That
means there would be much greater deformation before failure
in a forged part.
28. • Bolts, disks, gears, turbine disk, crank shaft,
connecting rod, valve bodies, small components
for hydraulic circuits etc.
• Advantages:
• Closer dimensional accuracies achieved require very little
machining after forging. Material saving is the result. Higher
strength, greater productivity, favorable grain orientation, high
degree of surface finish are other merits. However, complex die
making is costly.
YoucaN
35. CLASSIFICATION OF
FORGING
FORGING & PRESS WORKING 35
• On the basis of
process :
1. Open die Forging
2. Closed die Forging
• On the basis of
equipment :
1. Drop Forging
2. Power (Hammer &
press) Forging
3. Hand Forging
4. Machine Forging
Forging
Process
Open (smith)die
Forging
Hand
Forging
Power
Forging
Power Hammer Press Forging
Closed
(Impression)die
Forging
Drop
Forging
Press
Forging
Machine
Forging
36. • Open die forging:
• Closed die forging:
• Hand forging :- Hand forging is emplayed
only to shape a small number of light
forgings chiefly in repair shops.
• Hammer forgings :- Usually used for small
item forging.
• Press forging :- Usually used for heavy
item forging.
• Machine forging :- For medium sized and
large articles requiring very heavy blows.
• Drop forging :- For mass production of
identical parts.
36
YoucaN
37. • Open die forging is
performed on ingot, billets,
bar or a w/p and the
deformation a w/p between
flat or shaped dies
without completely
restricting the metal
flow.
• Few “cm” w/p to 30 m w/p
can be processed.
• Several hundred “kg” w/p
can also be worked in open
die forging.
YoucaN
38. OPEN DIE
FORGING
38
• This process also known as smiths
die forging or flat die
forging.
• The operation is carried out between
two flat dies of very simple shape
generally b/w the bottom surface of
hammer & top surface of anvil..
• The workpiece reduces their
height/plastically deform by
compressing it.
• The process is used for mostly large
objects
• Tooling is simple, inexpensive and
allows the production of a large
variety of shapes.
39. • Kinetic energy = ½(mv2)
• v=(2gh)^(1/2)
• H- stroke of the hammer
YoucaN
41. • Complex shapes with great accuracy forgings cannot
be obtained in open die forging.
• The complex forging can be made in impression die
forging.
• Impression die forging both die and punch have
impressions, shapes which are imparted onto the work
piece.
• There is more constrained flow in this process.
Moreover, the excess metal flows out of the cavity,
forming flash.
YoucaN
44. YoucaN
The formation of metal flash is an important part of
impression die forging manufacture.
First, flash provides a way for excess material from the work
stock to exit the forging die.
If this material could not escape during the compression the
build up of pressure, as the volume of work metal exceeded
the volume of the die cavity, could easily crack the die.
Flash, while allowing material to escape, does increase the
pressure within the die cavity. Flash must travel through a
narrow passage, called land, before it opens up into a gutter.
As it flows through land, the
friction between the metal flash
and the mating surfaces resists
further flow of material out of the
die cavity, increasing pressure
within the forging die.
45. YoucaN
In addition, the cooling of the flash from the mating surfaces
increases resistance to flow of material out of the die,
thus also increasing pressure within the die cavity.
A longer land will cause the metal flash to have to flow
further under resistance, increasing the die pressure.
Decreasing the width of land will also increase pressure
within the forging die by increasing the cooling rate of the
flash, as the temperature goes down the metal's resistance to
flow goes up.
More resistance to metal flow will cause a thinner land to
create higher die pressure.
The pressure within the
forging's die cavity is often
controlled by varying the
width of land.
46. • Single impression die
• Contains one cavity which is the finishing impression.
• Preliminary forging operations are done by hand or on forge
hammers.
• Multi-impression die:
• Contains finishing operation and one more auxiliary
impressions for preliminary forging operatioins.
YoucaN
48. CLOSED DIE
FORGING
48
• In this metal is deformed
under high pressure between
two dies (called tooling) or in
a closed cavity that contain a
profile of the desired part.
• Closed die forging are
commonly use where mass
production of identical &
more complex shapes of
greater accuracy are
required.
• The process provide
precision forging with close
dimensional tolerance.
• Normally used for smaller
components.
• Closed dies are expensive.
49. • Hand forging
• Heated metal is placed in anvil with the help of tongs.
Repeated blows are given by a sledge hammer to obtain
the metal into required shape.
YoucaN
50. DROP
FORGING
50
• It is also called as stamping. It
consists of special type of
hammer known as drop
hammer or drop stamp.
• Perfectly made steel dies are
used for forging.
• The top part of the die is raised
by mechanical links to a certain
height.
• The heated metal placed
accurately in the bottom part of
the die.
• The top part of the die is then
allowed to fall suddenly.
• This gives a high blow and
completes the workpiece in a
single operation.
51. HAMMER
FORGING
51
• Machine which is work by blow or impact to
perform forging process is known as hammer
forging.
Steam drop
hammer
•
• Power hammer
provides greater
capacity, in which
the ram is
accelerated on
the down stroke
by steam or air
pressure in
addition to
gravity.
• Steam or air
pressure is also
used to raise the
ram on the
upstroke.
• The upper die
and ram are
raised by
friction rolls
gripping the
board.
• After releasing
the board, the
ram falls under
gravity to
produce the blow
energy.
• The hammer can
strike between
60-150 blows
per minute
depending on
52. PRESS
FORGING
52
• Machine which is work on pressure to perform
forging process is known as press forging.
• The material gets uniformly deform throughout its
entire depth.
•
• Hydraulic presses are
load-restricted machines
in which hydraulic
pressure moves a piston
in a cylinder.
• The full press load is
available at any point
during the full stroke of
the ram.
• Due to slow speed,
contact time is longer at
the die-metal interface,
which causes problems
such a heat lost from
•
•
53. FORGING & PRESS WORKING 53
• Crank press translates
rotary motion into
reciprocating linear
motion of the press slide.
• The ram stroke is shorter
than in a hammer or
hydraulic press.
• The blow press is more
like squeeze than like
the impact of the
hammer, therefore, dies
can be less massive and
die life is longer than
with a hammer. MECHANICAL
PRESS
55. MACHINE
FORGING
55
• In machine forging the
material is only upset to
get the desire shape.
• The die consists of two
parts, one called the
stationary gripper die
which is fixed to the
machine frame and the
other movable gripper die
which moves along with
the die slide of the up
setter. The stock is held
then between these two
gripper dies.
• It is used for making
gears, blanks, shafts,
excels, and similar parts.
57. FORGING TOOLS
57
• TONGS :
Tongs are used mainly
for holding work of many
section.
• FLATTER :
Flatter is used to give
smoothness & accuracy
to articles which have
already been shaped by
fullers and swages.
• SWAGE :
Swage is used to
reduce/finish to round,
square/hexagonal form. It
consists of two parts-The
top part having a handle.
The bottom part having
a square shank.
58. 58
58
• ANVIL :
Anvil is used for supporting hot
job while hammering is done for
shaping it into various shapes. It is
made of cast steel.
• SWAGE BLOCK :
It is used for holding hot bars
during bending, support for
punching holes in a job &
various holes.
• FULLERS :
Fullers are used for necking
down/to form depressions.
61. YoucaN
Defects of metal forged product include exterior cracking, interior
cracking, laps, cold shuts, warping of the part, improperly formed
sections and dead zones. Cracking both interior and exterior is
caused by excessive stress, or improper stress distribution as the
part is being formed. Cracking of a forging can be the result of
poorly designed forging die or excess material in the work piece.
Cracks can also be caused by disproportionate temperature
distributions during the manufacturing operation. High thermal
gradients can cause cracks in a forged part.
62. • 1.) Unfilled Section:
• As the name implies in this type of defect some of the forging
section remain unfilled. This is due to poor design of die or poor
forging technic. This is also due to less raw material or poor
heating.
• This defect can be removed by proper die design, proper
availability of raw material and proper heating.
YoucaN
63. • 2.) Cold Shut:
• Cold shut includes small cracks at corners. These defects occur
due to improper design of forging die. It is also due to sharp
corner, and excessive chilling in forge product.
• The fillet radius of the die should be increase to remove these
defects.
• 3.) Scale Pits:
• Scale pits are due to improper cleaning of forged surface. This
defect generally associated with forging in open environment. It
is irregular deputations on the surface of forging.YoucaN
64. • 4.) Die Shift:
• Die shift is caused by misalignment of upper die and lower die.
When both these dies are not properly aligned the forged
product does not get proper dimensions.
• This defect can be removed by proper alignment. It can be done
by provide half notch on upper die and half on lower die so at
the time of alignment, both these notches will matched.
• 5.) Flakes:
• These are internal cracks occur due to improper cooling of forge
product. When the forge product cooled quickly, these cracks
generally occur which can reduced the strength of forge
product.
• This defect can be removed by proper cooling.
• 6.) Improper Grain Growth:
• This defect occurs due to improper flow of metal in casting
which changes predefine grain structure of product.
• It can be removed by proper die design
YoucaN
65. • 7.) Incomplete Forging Penetration:
• This defect arises due to incomplete forging. it is due to light or
rapid hammer blow.
• This defect can be removed by proper control on forging press.
• 8.) Surface Cracking:
• Surface cracking occurs due to exercise working on surfaces at
low temperature. In this defect, So many cracks arise on work
piece.
• This defect can be removed by proper control on working
temperature.
• 9.) Residual Stresses in Forging:
• This defect occurs due to improper cooling of forged part. Too
much rapid cooling is main causes of this type of defects.
YoucaN
69. YoucaN
The location of the parting
line of C will better facilitate
the flow of metal through
the die cavity, since unlike A
or B, location C makes use
of the maximum periphery
of the forging. It is easier to
fill material near the forging
plane than in the further
recesses of the die cavity. In
addition to being a major
factor in the flow of metal
during the forging process,
the location of the parting
line is also critical in the
formation of the grain
structure of the forged
work. The parting line acts
to disrupt the metal's grain
71. YoucaN
The placement of the parting line in A and B acts to disrupt the
grain structure of the metal at the plane through which it
passes. Locating the parting line at the top of the forging as in
C eliminates the rupture of the forging's grain structure. Also
this particular location of the parting line will allow for the entire
impression to be formed in one die, while the other die can be
flat. Design of the die as in C is both more economical and
provides superior grain structure of the metal forging.
73. YoucaN
As the work material fills the die cavity, the flow of metal will
have to change directions depending upon the part's geometry.
Smooth, large filleted turns will allow the metal flow to change
directions while adhering to the die's dimensions. If corners
within the metal forging are too sharp then the material may not
completely follow the path of those corners, resulting in
vacancies, laps, or cold shuts.
Sharp corners will also
act as stress raisers
within the die cavity.
Good forging die design
should provide
adequate enough fillet
and corner radius to
allow for easy metal
flow.
