Effect of Preheating on Martensitic Transformation in the Laser Beam Welded AH36 Steel Joint: A Numerical Study

In this work, the effects of preheating temperatures on martensitic transformations in a laser beam-welded AH36 steel joint were observed using a numerical study. In the same weld, the martensitic contents increased slightly from the upper area, the middle area to the lower area, and simulated martensite contents in the fusion zone were slightly lower than that in the HAZ (Heat Affected Zone). Under different preheating temperatures, simulated martensitic contents decrease with the increase of the preheating temperature. According to the simulated results, the average cooling rate and the CCT (Continuous Cooling Transformation) diagram were drawn to analyze the relationships between preheating temperatures and martensitic transformations. Simulated martensitic contents agreed well with the experimental metallographic microstructures. Moreover, the measured microhardness was reduced with the increasing preheating temperature, and measured microhardness in HAZ was higher than that in the fusion zone. The accuracy of the simulation results was further confirmed. The main significance of this work is to provide a numerical model to design martensitic contents in order to control the performances of the weld, avoiding many tests.