Low temperature annealing is a heat treatment method that heats steel parts to a temperature below Ac1. It is mainly used to eliminate residual stress, improve stability, and prevent quenching deformation and cracking. It includes softening annealing and recrystallization annealing. The commonly used softening annealing temperature is 650-720℃12.
The changes in metal structure and properties during stress relief annealing are equivalent to the recovery stage in the temperature curve. In actual production, the application of stress relief annealing process is much more extensive than the above definition. Hot forging, casting, various cold deformation processing, cutting or cutting, welding, heat treatment, and even after assembly of machine parts, the steel or machine parts are heated at a lower temperature to remove internal stress and reduce the tendency of deformation and cracking without changing the organizational state and retaining cold work, hot work or surface hardening. The process can be called stress relief annealing.
The purpose of low temperature annealing is to soften the steel parts to facilitate cutting or subsequent cold deformation. Through short-term heat preservation, the stress in the material is released, the grain boundaries are adjusted, the oxides are reduced, and the mechanical properties and microstructure of the material are improved.
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