Stress Release Annealing Furnace

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1. Principle of Stress Release Annealing

The cold-deformed metal is heated at a temperature lower than the recrystallization temperature to remove internal stress, but still retains the effect of cold work hardening. This heat treatment is called stress relief annealing, or low temperature annealing. The change of metal structure and properties during stress relief annealing is equivalent to the recovery stage in the temperature graph. In actual production, the application of stress relief annealing process is much broader than the above definition. Hot forging, casting, various cold deformation processing, cutting or cutting, welding, heat treatment, and even after assembly of machine parts, without changing the structure state, retaining cold work, hot work or surface hardening conditions, the steel or machine The process of heating the parts at a lower temperature to remove internal stress and reduce the tendency of deformation and cracking can be called stress relief annealing.

2. Stress Release Annealing Process

Stress-relief annealing is a process in which the workpiece is heated to an appropriate temperature below Ac1, and then gradually cooled slowly after holding it for a certain period of time. Its purpose is to remove the residual stresses caused by machining, deformation processing, casting, forging, heat treatment, and welding. See Figure 1 for the stress relief annealing process curve.

Fig 1 Process curve of stress relief annealing

The temperature of stress relief annealing should generally be 20~30℃ lower than the last tempering temperature, so as not to reduce the hardness and mechanical properties.

For thin-walled workpieces and easily deformed weldments, the annealing temperature should be lower than the lower limit.

Low temperature aging is used after semi-processing of the workpiece (such as after rough machining or the first finishing), and generally a lower temperature is used.

3. Technical Parameters of Stress Release Annealing Furnace

Type	Heating rate	Heating temperature	Holding time/h	Cooling time
Welded parts	≤300℃ furnace ≤100~150℃/h	500-550	2-4	Furnace cooled to 300℃, out of the furnace, air-cooled
Eliminate processing stress	To warm furnace	400-550	2-4	Furnace cooling or air cooling
High-precision bushing, bore rod （38CrMoAlA）	≤200℃ furnace ≤80℃/h	600-650	10-12	The furnace is cooled to 200 ℃ and out of the furnace (Cooling rate above 350℃≤50℃/h)
Precision screw （T10）	≤200℃ furnace ≤80℃/h	550-600	10-12	The furnace is cooled to 200 ℃ and out of the furnace (Cooling rate above 350℃≤50℃/h)
Spindle, general lead screw （45、40Cr）	Heat up with the furnace	550-600	6-8	The furnace is cooled to 200 ℃ and out of the furnace
Measuring tools, precision lead screws （T8、T10、CrMn、GCr15）	Heat up with the furnace	130-180	12-16	Air cooling (Aging is best carried out in an oil bath)

Shanghai Geheng Vacuum Technology Co., Ltd. is a vacuum heat treatment furnace manufacturer with many years of experience in design, manufacturing and production. Mainly produce vacuum heat treatment furnace, vacuum sintering furnace, vacuum brazing furnace, New Energy And Environmental Protection Equipment and other vacuum equipments.Provide customized services, equipment work area can be based on customer output.