Estimation of Cooling Rate from 800 °C to 500 °C in the Welding of Intermediate Thickness Plates Based on FEM Simulation

FEM (finite element method) simulation for estimating the cooling rate from 800 °C to 500 °C in welding cycle of plates with intermediate thickness is presented. Moving double ellipsoid heat sources were applied to simulate the thermal field of welding process, and the cooling rates were investigated with different welding parameters including plate thickness, heat input and preheating temperature according to the analysis of heat transfer characteristics. The critical condition for defining intermediate thickness of plates was determined through comparison between FEM results and calculation results from conventional analytical solutions of Rosenthal et al. and prediction equations of cooling rate in welding of plates with intermediate thickness were established based on regression analysis of FEM results using polynomial method. The feasible range of the equations with preheating temperature was discussed. The welding experiments with the same parameters were carried out to verify the effectiveness of the prediction equations. The compared results of thermal cycles and microstructures between experiment and FEM showed that a good agreement was obtained.