A thermal-metallurgical-mechanical model for laser welding Q235 steel

Austenization, austenite-pearlite/ferrite transformation, austenite-bainite transformation, and austenite-martensite transformation for laser welding Q235 steel were modeled. The physical properties of thermal-metallurgical-mechanical (TMM) model were determined using linear interpolation based on the phase fractions and physical properties of each pure phase. The volume change and the plastic strain caused by the phase transformations were considered in the TMM model to represent the influence of phase transformations on the stress field. The temperature, phase fraction, and equivalent stress fields during and after laser welding were predicted using a three-dimensional finite element (FE) code developed by the authors to solve the TMM model. To validate the simulation results, temperature, phase fraction, and stress measurement experiments were carried out to study the influence of the phase transformations on both the temperature and stress fields during welding.