The residual stress in the weldment is inevitable because of the uneven temperature distribution on the weldment, the shrinkage of the deposited metal, the rigid constraint of the welding structure and the transformation of the metal structure of the welded joint. For parts with strict requirements, we should try to eliminate the welding stress. There are three common methods to eliminate the stress. The first is the heat treatment method, which is to heat the weldment to a certain temperature and cool it after insulation. It is widely used, divided into overall heat treatment and local heat treatment. The second method is mechanical method, which applies external force to make the cooled weld expand to eliminate stress. The third is vibration method, which can eliminate the stress by shaking the whole component at low frequency.
The argon recovery project of DEAR Air Separation has three major innovations: 1. This project uses cryogenic method to purify argon, which can make the purity of argon reach the standard of high-purity argon; 2. In the process of organizing the project, the method of expansion refrigeration is not adopted for obtaining the cooling capacity, but the method of liquid argon reinjection is adopted, because it is unable to recover all the argon itself, and it is necessary to replenish the liquid argon. The cooling capacity of this part of liquid argon is just used, and the vaporization part of liquid argon is also omitted; 3. The whole process is through hydrogenation to produce oxygen and rectification to remove nitrogen.
