Abstract: A direct current flash butt welding (DC FBW) process is analyzed for an ultra fine grain steel using finite element method. According to the computed temperature field and the relation between real welding time and Monte Carlo (MC) simulation time established from the experimental data based (EBD) model, microstructure evolution model is built up for the DC FBW. Then, the Austenite grain growth of the welded joints for the ultra fine grain reinforcement steel bar is simulated. At the same time the heat pinning effect of temperature gradient on the grain growth in the heat affected zone is considered. The results indicate that the grain size and distribution can be predicted using the Monte Carlo simulation technology for the DC FBW process. Also, the technology is a powerful tool for determining welding parameters and improving welds quality.

Key words: DC flash butt welding, Microstructure, Monte Carlo simulation, Ultra-fine grain steel