What is stress relief annealing What is the principle of stress relief annealing
Annealing is a very important process in metal smelting, and there are many methods of annealing, such as rapid annealing, stress relief annealing, etc. Now Kehua will talk to you about what is stress relief annealing and what is the principle of stress relief annealing? What is stress relief annealing? The metal after cold deformation is heated below the recrystallization temperature to remove the internal stress, but still retain The heat treatment of cold work hardening effect is called stress relief annealing, also known as low temperature annealing. The change of metal structure and properties during stress relief annealing is equivalent to the recovery stage in the temperature curve. In actual production, the application of stress relief annealing process is much broader than the above definition. According to Kehua's understanding, after hot forging, casting, various cold deformation processing, cutting or cutting, welding, heat treatment, and even the assembly of machine parts, without changing the organizational state and retaining cold work, hot work or surface hardening, The process of heating steel or machine parts at a lower temperature to remove internal stress and reduce the tendency of deformation and cracking can be called stress relief annealing. Stress relief annealing What is the principle of stress relief annealing? Stress relief annealing does not completely eliminate the residual stress inside the workpiece, but only mostly eliminates it. To completely eliminate residual stress, the workpiece needs to be heated to a higher temperature. Under such conditions, other tissue changes may be introduced, compromising the performance of the material. During stress relief annealing, the metal undergoes internal local plastic deformation (when the stress exceeds the yield strength of the material at the temperature) or local relaxation process (when the stress is less than the yield strength of the material at the temperature) under the action of 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 gray cast iron, 500 to 650 °C for steel, and below the recrystallization start temperature for non-ferrous metal alloy stampings), after a period of time, slowly Cooling to prevent new residual stress. In the process of metal smelting, stress relief annealing is the most widely used annealing method. After stress relief annealing, the probability of deformation and cracking of the metal product can be reduced.