Stress relieving is a general term in heat treating, describing a wide range of processes. Generally, metal stress relieving involves heating a part to a temperature at which the yield strength is sufficiently low to the point which internal stresses can relieve themselves. Higher temperatures and longer times are beneficial and will yield a part with lower internal stress. Temperatures are always below the point at which there is a change of phase in steel.
Process of Stress Relieving Heat Treatment – Points to Consider
Stress relieving is a heat treatment process used for materials ranging from plastics and steel to non-ferrous materials, such as copper alloys and aluminum. For non-ferrous materials, temperatures are comparatively low, ranging from about 200F for plastics and 900F for copper alloys.
Stress Relieving Recommendations from ThermTech
Typically, there is very little distortion during stress relieving. However, some considerations may be required for long slender components or plates that are heavily cold worked. If shot blasting is done after stress relieving, this operation does impart compressive stresses at the surface of the material and can cause distortion. Cast materials with low ductility or with geometries that include stress risers can increase the probability of cracking during the heating portion of the stress relief cycle. These materials may need a slow ramp rate to the stress relieving temperature.