Stress relief annealing

The cold-finished metal is heated at a temperature lower than the recrystallization temperature to remove internal stress, but still retains the cold hardening effect, which is called stress relief annealing, also called low temperature annealing. The change in metal structure and properties during stress relief annealing corresponds to the recovery phase in the temperature profile. In actual production, the application of the stress relief annealing process is much broader than the above definition. Hot forging, casting, various cold deformation processing, cutting or cutting, welding, heat treatment, even after assembly of machine parts, without changing the state of the structure, retaining cold work, hot work or surface hardening, steel or machine with process in which parts are heated at a lower temperature to remove internal stress and reduce the tendency of deformation and cracking may be referred to as stress relief annealing.

During pressure processing, casting, welding, heat treatment, cutting, and other processes, the article may generate internal stress. In most cases, a portion of the residual stress will remain inside the metal at the end of the process. Residual stress can cause cracking, deformation or dimensional change of the workpiece. Residual stress also increases the chemical activity of the metal. It is particularly prone to intergranular corrosion cracking under the residual tensile stress. Therefore, residual stress will affect the performance of the material or cause premature failure of the workpiece.


During stress relief annealing, the metal undergoes internal local plastic deformation (when the stress exceeds the yield strength of the material at this temperature) or a local relaxation process (when the stress is less than the yield strength of the material at this temperature) at a certain temperature. The residual stress is relaxed to achieve the purpose of elimination. During stress relief annealing, the workpiece is generally slowly heated to a lower temperature (500 to 550 °C for grey cast iron, 500 to 650 °C for steel, and less than the recrystallization start temperature for nonferrous metal alloy stampings). Cool to prevent new residual stresses.

Stress relief annealing does not completely eliminate the residual stress inside the workpiece, but only largely eliminates it. To completely eliminate residual stress, the workpiece needs to be heated to a higher temperature. Under these conditions, other organizational changes may occur, jeopardizing the performance of the material.