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Why forgings must be heat treated

Feb 13, 2019

Why is the heat treatment after the forging is forged? The purpose is to refine the coarse grains caused by the forging process, eliminate the work hardening and residual stress, reduce the hardness, improve the cutting performance, and prevent the occurrence of white spots inside the forging. Obtain the desired metal structure and mechanical properties to prepare for the final heat treatment.

There are six commonly used types:

Complete Annealing - Eliminates coarse uneven microstructure and Wei's structure caused during forging, refines the grain, and eliminates residual stress and hardness of the forging.

Spheroidizing Annealing---Spherical cementite and ferrite structure are obtained, which not only has a low hardness, but also is easy to obtain a smooth processed surface during cutting, and is not susceptible to deformation cracking in subsequent quenching. <High carbon steel, high carbon alloy tool steel,>

Isothermal annealing - not only shortens the annealing time, but also obtains a uniform structure and reduces hardness. In important large forgings, it can also be used to diffuse hydrogen to prevent white spots.

The post-forging heat treatment of aluminum alloys and copper alloys is generally performed by an annealing process. The purpose is to eliminate work hardening, stress, and plasticity.

Normalizing - can obtain finer pearlite, which can improve the mechanical properties of forgings suitable for machining. <Low carbon steel (including stainless steel, heat resistant steel), medium carbon steel and low carbon alloy steel>

Normalizing and tempering at high temperature---eliminating the stress generated during normalizing cooling and improving plasticity and toughness.

Tempering---Forgings have good comprehensive mechanical properties.