The precision seamless steel tube is heated to a certain temperature (usually below the phase change temperature or recrystallization temperature), held for a period of time, and then slowly cooled to eliminate the internal stress of various precision seamless steel tube annealing process.
In pressure machining, casting, welding, heat treatment, cutting and other processes, products may produce internal stress. In most cases, at the end of the process, a portion of the residual stresses will remain within the metal. Residual stress can lead to workpiece rupture, deformation or dimensional changes, residual stress also improves the chemical activity of the metal, in the residual tensile stress is particularly susceptible to intergranular corrosion rupture. Therefore, the residual stress will affect the performance of precision seamless steel tube or lead to premature failure of the workpiece.
De-stress annealing, precision seamless steel tube at a certain temperature through the internal local plastic deformation (when the stress exceeds the yield strength of the material at that temperature) or local relaxation process (when the stress is less than the yield strength of the material at that temperature) so that the residual stress relaxation to achieve the elimination of the purpose. In the stress relief annealing, the workpiece is generally slowly heated to a lower temperature (gray cast iron for 500 ~ 550 ℃, precision seamless steel pipe for 500 ~ 650 ℃, non-ferrous metal alloy stamping for the recrystallization of the beginning of the temperature below), held for a period of time, slowly cooled in order to prevent the generation of new residual stresses.
De-stress annealing does not completely eliminate the residual stress inside the precision seamless steel tube, but only most of the elimination. For complete elimination of residual stresses, the precision seamless steel tube needs to be heated to a higher temperature. Under these conditions, other organizational changes may be brought about, jeopardizing the performance of the precision seamless steel tube.