Forgeability of Metals

Forgeability is a Combination of the Following Characteristics

• The flow stress
• The ability to fill a die
• The degree of deformation that can be carried out without failure (due to surface or internal cracking)

Although in general the forgeability of metals increases with increasing temperature, for certain metals there is a maximum temperature above which some undesirable phenomena occur, such as fast grain growth or melting of a phase.

Fine grain metals have better forgeability. Metals with insoluble inclusions tend to be brittle and have low forgeability.

Two popular tests for determining the forgeability of materials are the ‘upset test’ (where cylindrical specimens are upset in steps until they start cracking radially or circumferentially) and the hot ‘twist test’ where a round bar is heated in a tubular furnace then twisted. The number of twist turns to failure is a relative measure of forgeability. Testing can be carried out in a range of temperatures and strain rates to determine the best conditions for practical forging.

The table below ranks metals / alloys in order of decreasing forgeability and approximate hot forging temperature range