Ingeniero

Chapter 2

Forging
Subjects of interest
• Introduction/objectives • Classification of forging processes - Hammer or drop forging - Press forging - Open-die forging - Closed-die forging • Calculation of forging loads • Effect of forging on microstructure • Residual stresses in forgings • Typical forging defects
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Objectives• This chapter provides fundamental of metal working process for forging in order to understand mathematical approaches used in the calculation of applied forging loads required to cause plastic deformation to give the final product. • Classification of metal forging methods is also provided with descriptions of defects observed from the forging processes. • The solutions to tackle suchdefects will also be addressed.

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Tapany Udomphol

Jan-Mar 2007

Introduction
• 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 insize of a bolt to a turbine rotor. • Most forging operations are carried out hot, although certain metals may be cold-forged.
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Tapany Udomphol

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Forging operations
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 freeto flow laterally to fill the die.

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

Piercing and punching are used to produce holes in metals.

Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2007

Forging operations
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 internalcombustion engine.

• Fuller move fast and moves metal perpendicular to the face
Fullers come in different shapes
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Fullers
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Tapany Udomphol

Jan-Mar 2007

Forging operations

Swaging is used to produce a bar with asmaller diameter (using concave dies). • Swaging is a special type of forging in which metal is formed by a succession of rapid hammer blows • Swaging provides a reduced round cross section suitable for tapping, threading, upsetting or other subsequent forming and machining operations.

Swaging at the ends, ready for next forming process.

Suranaree University of Technology

Tapany UdompholJan-Mar 2007

Classification of forging processes
By equipment
1) Forging hammer or drop hammer 2) Press forging

By process
1) Open - die forging 2) Closed - die forging

Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2007

Forming machines
There are four basic types of forging machines

Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2007Hammer and press forging processes
Forging hammers
There are two basic types of forging hammers used;

• Board hammer • Power hammer Forging presses
There are two basic types of forging presses available;

• Mechanical presses • Hydraulic presses

Suranaree University of Technology

Tapany Udomphol

Jan-Mar 2007

Board hammer –forging hammer
• The upper die and ram are raised byfriction 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 energyrestricted machine. The blow energy supplied equal the potential energy due to the weight and the height of the fall.

Potential energy = mgh

…Eq 1

Board...