Numerical simulation of Pearlite formation during welding of rails

In this work, a thermo-metallurgical coupled simulation model of welding of R350HT pearlitic rail steel was realized to estimate the mechanical properties in the HAZ. The applied approach was to estimate the hardness of pearlitic phase fractions by calculating the interlamellar spacing. This was realized in a methodology of multiple
calculation steps. Therein, MATLAB®-routines are used to calculate parameters for a metallurgical model to be used in SYSWELD®, based on a simulated TTT-diagram from JMatPro® and an experimentally determined welding- CCT-diagram of R350HT rail steel. This so established metallurgical model was verified by a simulation of dilatometry tests in SYSWELD® and subsequent quantitative comparison to experimental results. In a final step three more MATLAB®-routines are used to calculate phase fractions, interlamellar spacing and hardness for a practical example. Therefore, measured temperature curves from instrumented flash-butt welding (FBW)
experiments of standard rails were used as input. The results of the simulation are compared to real welds’ phase fractions and hardness values in the HAZ and showed very good agreement.