Study of forging , its classification & types

Study of forging , its classification & types present by Engr. umair raza

1. Umair Raza Study of Forging 19013386-002
BS-MECHANICAL ENGINEERING & TECHNOLOGY 54


Introduction:-
 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.
 Forging is the working of metal into a useful shape by hammering or pressing.
 The oldest of the metalworking arts (primitive blacksmith).
 Replacement of machinery occurred during early the Industrial revolution.
 Forging machines are now capable of making parts ranging in size of a bolt to a turbine rotor.
 Most forging operations are carried out hot, although certain metals may be cold-forged.
Forging Operation:-
 Edging.
 Drawing.
 Piercing and punching.
 Fullering.
 Swaging.
Edging:
Edging is used to shape the ends of the bars and
to gather metal. The metal flow is confined in the
horizontal direction but it is free to flow laterally
to fill the die.


Drawing:
Drawing is used to reduce the cross-sectional
area of the work-piece with concurrent increase
in length.

Piercing and punching:
Piercing and punching are used to produce holes
in metals.

Fullering:
Fullering is used to reduce the cross-sectional
area of a portion of the stock. The metal flow is
outward and away from the centre of the fuller.
i.e., forging of connecting rod for an internal
combustion engine. Fullers come in different
shapes Fuller move fast and moves metal
perpendicular to the face

2. Umair Raza Study of Forging 19013386-002
BS-MECHANICAL ENGINEERING & TECHNOLOGY 55

Swaging:
Swaging is used to produce a bar with a smaller
diameter (using concave dies).
 Swaging is a special type of forging in
which metal is formed by a succession of
rapid hammer blows
 Swaging is a special type of forging in
which metal is formed by a succession of
rapid hammer blows Swaging at the ends,
ready for next forming process



Classification of Forging:-
 By equipment:
1) Forging hammer or drop hammer.
2) Press forging.
 By process:
1) Open - die forging.
2) Closed - die forging.
There are two basic types of forging hammers used;
 Board hammer.
 Power hammer.
There are two basic types of forging presses available;
 Mechanical presses.
 Hydraulic presses.
Board hammer-forging hammer:
 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 size and capacity.
 The board hammer is an energy restricted machine. The blow energy supplied equal the potential
energy due to the weight and the height of the fall.
 This energy will be delivered to the metal work- piece to produce plastic deformation.
Forging hammer or drop hammer:
 Provide rapid impact blows to the surface of the metal.
 Dies are in two halves - Lower : fixed to anvil - Upper : moves up and down with the TUP.
 Energy (from a gravity drop) is adsorbed onto the metal, in which the maximum impact is on the
metal surface.
 Dies are expensive being accurately machined from special alloys (susceptible to thermal shock).
 Drop forging is good for mass production of complex shapes.

3. Umair Raza Study of Forging 19013386-002
BS-MECHANICAL ENGINEERING & TECHNOLOGY 56

Open-die forging:
 Open-die forging is carried out between flat dies or dies of very simple shape.
 The process is used for mostly large objects or when the number of parts produced is small.
 Open-die forging is often used to perform the work-piece for closed- die forging.
Close-die forging:
Closed-die forging (or impression-die forging).
 The work-piece is deformed between two die halves which carry the impressions of the desired final
shape.
 The work-piece is deformed under high pressure in a closed cavity.

Forging types:-
 Smith forging.
 Drop forging.
 Press forging.
 Machine or upset forging.
Smith forging:
Forging worked between flat or simple contour dies by repeated strokes and manipulation of workpiece.
Drop forging:
 Metal shape is formed by forcing hotmetal into impressions formed in solid blocks of hardened alloy
steel, the forging dies.
 Produces a parting line and flash on the workpiece, flash must be removed.
 Typically requires machining to obtain dimensional tolerance and good surface finish
Machine or upset forging:
 Increases the diameter of the end of central portion of work piece by compressing its length.
 Usually requires no trimming.
 Complex parts are usually formed gradually in a sequence of separate die cavities.
 May produce diameter up to three times the original diameter
Press forging:
 Metal is shaped between dies by mechanical or hydraulic pressure.
 Unlike drop hammer forging, press forges work slowly by applying continuous pressure or force.
 This can be done either cold or hot.

4. Umair Raza Study of Forging 19013386-002
BS-MECHANICAL ENGINEERING & TECHNOLOGY 57

Advantages of Forging:-
 Produce a piece that is stronger than an equivalent cast or machined part.
 Its refines the internal grain structure and improves physical properties of the metal (such as
strength, ductility and toughness).
 These are consistent from piece to piece, without any of the porosity, voids, inclusions and other
defects.
 Have high strength to weight ratio (design of aircraft frame members.).

Disdvantages of Forging:-
 Production forging involves significant capital expenditure for machinery, tooling, facilities and
personnel.
 A high-temperature furnace is required to heat ingots or billets

Forging Applications:-
Applications of forging include.
1. Bolts.
2. Disks.
3. Gears.
4. Turbine disk.
5. Crank shaft.
6. Connecting rod.
7. Valve bodies.
8. Small components for hydraulic circuits etc.
Forging Machine:-
There are four (4) basic types of forging machine.

5. Umair Raza Study of Forging 19013386-002
BS-MECHANICAL ENGINEERING & TECHNOLOGY 58


Conclusion:-
Forging process gives better quality product than the part produced by any other processes
with implementation of preventive actions to reduce the rejection rate. Forging process is
accomplished by hammering or pressing the metal.