Fast three-dimensional multipass welding simulation using an iterative substructure method

•The analysis code to simulate the 3D multipass welding process quickly was improved.•The improved analysis code provides the same analysis accuracy as a well-known commercial code.•Assumption of annealing effect and the isotropic hardening rule improve simulation accuracy.•The improved analysis code can solve welding problems faster than a well-known commercial code. An iterative substructure method has been proposed as a technique to calculate thermal elastic–plastic problems quickly and efficiently. Based on the iterative substructure method, an analysis code for the multipass welding was developed so as to realize accurate residual stress computation using a 3D precise model within a practical time. In the present study, the fast computation performance of the iterative substructure method was considered as a means to improve the original code. Then analysis accuracy and speed of the improved code were investigated. The proper analysis accuracy of the improved code was demonstrated by comparing with residual stress measurements of a multipass butt-welded pipe joint. The analysis speed of the improved code was clarified to be faster than a well-known commercial code in comparison between their computation times.