The document discusses the forging process, which involves shaping heated metal through techniques like hammer and press forging, and emphasizes the importance of plasticity in metal deformation. It details types of forging such as cold, hot, and press forging, along with their advantages, disadvantages, and various applications. Additionally, the document covers equipment used, classification of forging methods, common defects encountered, and guidelines for proper forging techniques.

1. Lecture Notes
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2. Forging is the process of shaping heated
metal by the application of sudden blows (i.e.,
hammer forging) or steady pressure (i.e.,
press forging) and makes use of the
characteristic of plasticity of the material.
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3. A metal such as steel can be shaped in a cold
state but the application of heat lowers the
yield point and makes permanent deformation
easier.
Forging may be done by hand or machine.
Forging by machine involves the use of dies
and is generally used in mass-production.
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4. Forging refers to the production of
medium size and heavy parts in large
scale using closed heating furnaces and
heavy hammers, forging presses and
machines.
Forging is the working of metal into a
useful shape by hammering or pressing.
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5. Forging is basically involves plastic
deformation of material between two
dies to achieve desired configuration.
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8.  Cold Forging
 Hot Forging
 Press Forging
 Impact Forging
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9. By equipment
1) Forging hammer or drop hammer
2) Press forging
By process
1) Open - die forging
2) Closed - die forging
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10. Hot or warm forging
most common, due to the significant deformation and
the need to reduce strength and increase ductility of
work metal to produce complex shapes
Cold forging
advantage: increased strength that results from strain
hardening and minimal machining
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11. Based on the nature of material flow and
constraint on flow by the die/punch,
Forging is classified as
Open die forging,
Impression die forging and
Flashless forging.
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12.  There is no constraint to material flow in lateral
direction. Upsetting is an open die forging in which
the billet is subjected to lateral flow by the flat die and
punch.
 Due to friction the material flow across the thickness
is non uniform. Material adjacent to the die gets
restrained from flowing, whereas, the material at
center flows freely.
 This causes a phenomenon called barreling in upset
forging.
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13.  Open die forging is hot mechanical forming between
flat or shaped dies in which the metal flow is not
completely restricted
 The stock is laid on a flat anvil while the flat face of the
forging hammer is struck against the stock.
 The equipment may range from the anvil and hammer
to giant hydraulic presses
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14. a) Solid cylindrical billet upset between two flat dies
b) Uniform deformation of the billet without friction
c) Deformation with friction
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15.  Reduced chance of voids
 Better fatigue resistance
 Improved microstructure
 Continuous grain flow
 Finer grain size
 Greater strength
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16.  "Cogging" is the successive deformation of a bar along its
length using an open-die drop forge. It is commonly used
to work a piece of raw material to the proper thickness.
 Once the proper thickness is achieved the proper width is
achieved via "edging".
 "Edging" is the process of concentrating material using a
concave shaped open-die.
 The process is called "edging" because it is usually carried
out on the ends of the workpiece.
 "Fullering" is a similar process that thins out sections of the
forging using a convex shaped die. These processes prepare
the workpieces for further forging processes.
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FulleringEdging

18.  In closed die forging, the desired configuration is
obtained by squeezing the workpiece between two
shaped and closed dies.
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20. Forge hammer - applies an impact load
Forge press - applies gradual pressure
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22.  Press forging may be defined as the process of shaping a
metal that is placed between two dies by applying
mechanical or hydraulic pressure.
 Press forging is usually done on a forge press - a machine
that applies gradual pressure on the forging dies.
 The shape of the metal is usually accomplished by a single
stroke of the press for each die station.
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23. Coining
This forging method is used to make coins. The metal is
enclosed in a closed die and high pressures (almost 5-6
times the strength of the metal) are applied to obtain
fine details of the die. Lubricants are not used in coining.
Hubbing
In this type of press forging, a pattern is pressed onto the
die, such that the pattern flows into the die cavities. This
process is often used in making of silverware.
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24. The three main types of forging presses used for press
forging are listed below:
 Mechanical Press – converts the rotation of the motor
into linear motion of the ram.
 Hydraulic Press – hydraulic motion of the piston
moves the ram.
 Screw press – screw mechanism actuates the ram
movement.
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25.  Deforms the work piece completely
 Compression rate of the work piece can be controlled
 More economical for high volume productions
 Any size and shape can be created
 Requires less draft and produces lesser scrap.
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26.  Some of the industrial applications of press forgings
are listed below:
 Making of coins and silver articles
 Automatic forging.
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27. Upset forging increases the diameter of the
workpiece by compressing its length .
These rules must be followed when designing parts to be
upset forged
 The length of unsupported metal that can be upset in one blow
without injurious buckling should be limited to three times the
diameter of the bar.
 Lengths of stock greater than three times the diameter may be
upset successfully, provided that the diameter of the upset is not
more than 1.5 times the diameter of the stock.
 In an upset requiring stock length greater than three times the
diameter of the stock, and where the diameter of the cavity is not
more than 1.5 times the diameter of the stock, the length of
unsupported metal beyond the face of the die must not exceed
the diameter of the bar.
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28.  Upset forging is usually done in special high-speed machines
called crank presses.
 The machines are usually set up to work in the horizontal
plane, to facilitate the quick exchange of workpieces from one
station to the next, but upsetting can also be done in a vertical
crank press or a hydraulic press.
 The initial workpiece is usually wire or rod, but some machines
can accept bars up to 25 cm (9.8 in) in diameter and a capacity
of over 1000 tons. T
 he standard upsetting machine employs split dies that contain
multiple cavities.
 The dies open enough to allow the workpiece to move from
one cavity to the next; the dies then close and the heading tool,
or ram, then moves longitudinally against the bar, upsetting it
into the cavity.
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29. Compression of workpart by dies with inverse (negative
impression) of desired part shape
Flash is formed by metal that flows from die cavity into a
small gap between die plates – represents a possible flow
path, flow inside the cavity represents an alternative
Metal will always take the path of least resistance.
Flash is excess material & must be trimmed, but it serves
an important function:
 As flash forms, friction resists continued metal flow into
gap, constraining material to fill die cavity
 Strain rate sensitivity also resists movement in the flash
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30. Advantages of impression-die forging compared to
machining from solid stock:
 Higher production rates
 Less waste of metal
 Greater strength
 Favorable grain orientation in the metal (harder to
shear across the grains)
Limitations:
 Not capable of close tolerances (± 0.030”)
 Machining often required to achieve accuracies and
features needed
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31. 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.
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. It can be removed
by proper cleaning of forged surface.
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32. 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
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33. 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. This can be removed by slow cooling of forged part.
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34.  High cost and high residual stress produced.
 Most forging processes are expensive because of the
cost of making dies, so long production runs are
usually necessary to reduce costs.
 The high residual stresses in forgings are often
released when they are machined and cause warping
when heavy cuts are taken.
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