Research Of Mechanical Behaviors Of Stainless Thin-wall Pressed Part Welding

Welding of pressed part is widely implemented in manufacturing fields of vehicles, pressure containers, et al. However, in some structures, initial stress induced by pressing can result in crack or quality problems like unequal contractions at welding joint. Existing studies mostly focus on single process, either pressing or welding.In this article, the object studied is a structure of lap welding of thin pressed part, which is a part of a CO2 gas tank. The material is SUS444L ferritic stainless steel. By means of experiments and simulations, the processed including both pressing and welding are analyzed as a whole.Then the results of axial stress, induced by pressing, is applied in the calculation of welding structures as initial stresses. The method of calculations is thermoelasto-plasticity FEM, implemented in the software MSC.Marc. During the simulation, we use re-developed function in MSC.Marc for welding heat source, heat transfer coefficient parameter and et al.The results under two conditions with or without initial stress are calculated and compared. It is implicated that the welding residual stresses in fusion zone are close in two conditions, but in HAZ, Axial residual stress is negative on the outer side and positive on the inner side. So the concept of bending stress is introduced, defined as the difference between stress on inner surface and outer surface. Results show that the level of bending stress is much larger with initial stress than that without stress.Calculation also indicates that bending stress in HAZ decrease by using SUS316L austenite stainless steel as filler metal.Finally, we evaluate the tendency during welding by implementing criterions as J2 and BS7910. It indicates high tendency of heat crack propagation during welding process.