The Three Primary Stages of the Annealing Process

25 January 2022

Manufacturers can maximise a wide array of heat treatment processes to ensure that their parts and products can boast improvements over their general characteristics and properties. One heat treatment process that manufacturers often utilise is annealing.

Annealing is a heat treatment process that is well-known for soft metals. The primary purpose of the annealing process is to increase the ductility of the metals. It can likewise ensure that the metals can be formed and shaped more effectively and efficiently. Soft metals tend to lose their ductility as they undergo work hardening, especially when they are exposed to bending, cold forming, or drawing processes. With annealing, the original properties of the materials can be obtained again.

To date, the annealing process can be done through three primary stages. These stages are recovery, recrystallisation, and gain growth.

Recovery Stage

The recovery stage of annealing recovers the physical properties of the metals. Some metal properties that are expected to be recovered during this stage are electrical conductivity, internal energy, and thermal expansion. During this stage, the furnace or other heating devices is maximised to increase the temperature of the materials, softening the metals and relieving their internal stresses.

Recrystallisation Stage

The recrystallisation stage, on the other hand, is a restorative process wherein the materials are heated above their recrystallisation temperature but below their melting point. During this particular stage, any deformed grains of the metal’s crystal structures are substituted with new stress-free grains, which came from the recovery stage. Once the stress-free cells nucleate and grow, the materials would possess new grains without residual stresses. 

Not all materials, however, must be heated into a critical temperature range to undergo this stage. Mild steel products, for instance, can already be softened at 500 to 650°C.

Gain Growth Stage

One more stage of annealing that the materials often undergo is the gain growth stage. The grain growth stage is carried out whenever the annealing process continues with the involved materials. Once the recrystallisation has been done, the gain growth stage follows, making the microstructure of the metals coarse as they are cooled. During this stage, the materials may lose some of their strength. However, the lost strength can be regained through hardening processes like quenching and tempering. 

Even though they tend to consume a lot of time, the annealing process and its accompanying stages are essential since they can make the materials workable. Without this particular process, the materials may crack and incur other damages that would only affect industrial operations.

To know more about the annealing process and its stages, you can call us at Alpha Detroit Heat Treatment. Our expertise allows us to suggest the most appropriate process for your heat treatment requirements. We pride ourselves on providing quality service and reliability.

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