In the welding process, due to the unevenness of heatin […]
In the welding process, due to the unevenness of heating and cooling, as well as the constraints or additional constraints of the component itself, welding stress will always be generated in the component after the welding work is completed. The existence of welding stress in the component will reduce the actual load-bearing capacity of the welded joint area and produce plastic deformation. In severe cases, it will also lead to the destruction of the component.
Stress-relieving heat treatment is to reduce the yield strength of the welded workpiece at a high temperature to achieve the purpose of relaxing the welding stress.
There are two commonly used methods: one is the overall high temperature tempering, that is, the whole weldment is put into a heating furnace, slowly heated to a specified temperature, and then kept for a period of time, and then cooled in the air or in the furnace. With this method, 80%-90% of the welding stress can be removed.
Another method is local high temperature tempering, that is, only heating the weld and its nearby area, and then slowly cooling it to reduce the peak value of the welding stress, so that the stress distribution is relatively gentle, and the purpose of partially removing the welding stress is achieved.
After some alloy steel materials are welded, their welded joints will have a hardened structure, which will deteriorate the mechanical properties of the material. In addition, this hardened structure may cause damage to the joint under welding stress and hydrogen.
After heat treatment, the metallographic structure of the joint is optimized, which improves the plasticity and toughness of the welded joint, thereby improving the comprehensive mechanical properties of the welded joint.