Stress Relief Annealing

The precision seamless steel tube to a certain temperature (usually in the phase transition temperature or recrystallization temperature below), the insulation for some time, and then slowly cooling, to eliminate stress in a variety of precision seamless steel tube annealing process.

In press working, casting, welding, heat treatment, cutting and other processes, the product may produce internal stress. In most cases, the metal will retain a portion of its residual stress after the process has ended. Residual stress can lead to fracture, deformation or size change of the workpiece, residual stress also improve the metal chemical activity, in the residual tensile stress is particularly vulnerable to intergranular corrosion caused by rupture. Therefore, the residual stress will affect the performance of precision seamless steel pipe or lead to premature failure of the workpiece.

When the stress is less than the yield strength of the material at the temperature below which the stress is less than the yield strength of the material at the temperature of the stress relaxation temperature, When the residual stress relaxation to achieve the purpose of elimination. In the stress relief annealing, the workpiece is generally slowly heated to a lower temperature (gray cast iron is 500 ~ 550 ℃, precision seamless steel pipe is 500 ~ 650 ℃, non-ferrous metal alloy stamping parts for the recrystallization temperature below), to maintain a period of time , And then slowly cooled to prevent the generation of new residual stresses.

Stress-relief annealing does not completely eliminate the residual stress inside the precision seamless steel tube, but is largely eliminated. For the complete removal of residual stress, precision seamless steel tubes need to be heated to a higher temperature. In this condition, may bring other organizational changes, endangering the use of precision seamless steel pipe performance.