The Numerical Simulation Of Welding Residual Stresses On New High Cr Ferritic Heat-resistant Steel

With the rapid development of China's economic, the demand for electricity continues to increase. Currently,thermal power generation has a particularly important position in China's energy industry and accounting for more than 80% of the total electricity generation. In order to solve the problem of energy shortage and pollution of enviroment, the thermal efficiency of thermal power generating unit must be improved, and this will make higher requirements for hot strong sex and weldabilidy of heat-resistant steel. Large residual stress existing in heat-resistant steel will seriously threat to the safe use and directly affect heat-resistant steel's service life and even cause cracks occur in welding process with inappropriate choice of welding process. For this reason, it is very important to control the welding residual stress by prediction of residual stress residual stress after welding.SYSWELD software and double ellipsoid heat source were adopted to perform FEM simulation of the improved heat-resistant ferritic steel welding thermal process , also considering the thermal-physical properties of the nonlinear material and the effects of the latent heat.The Koistinen-Marburger relationship was employed here in order to trace the martensite fraction during martensitice transformation in the process of thermal cycle. In addition, discuss deeply the influence of solid-state phase transformation on welding residual stress. The results show that the cooling process of the martensitic transformation reduces the residual stress of weld zone and heat affected zone.Multi-layer welding of pipes was simulated to obtained weld residual stress distribution with coupling of three field (temperature field, microstructure field and stress-strain field) , and study the effect of heat treatment on residual stress of improve heat-resistant ferritic steel.