Three-dimensional Monte Carlo simulation of grain growth in the heat-affected zone of a 2.25Cr-1Mo steel weld

We report here the first three-dimensional (3-D) Monte Carlo (MC) modeling of grain growth in the heat-affected zone (HAZ) of a weldment. Computed grain-size distributions in the HAZ of a 2.25Cr-1Mo steel, for different heat inputs in the range from 1.1 to 4.8 MJ/m, were compared to independent experimental results. The simulated mean grain size for different heat inputs agreed well with the corresponding independent experimental data. The mean grain size at various locations equidistant from the fusion line were different. The predicted grain size from the 3-D model matched the experimental results more closely than that from a two-dimensional (2-D) model. When the whole calculation domain was subjected to a single thermal cycle experienced by a monitoring location within the HAZ, the computed grain size was larger than that calculated at the monitoring location by taking into account the prevailing temperature gradient due to thermal pinning. The good agreement between the simulated grain structure and the corresponding experimental results indicates significant promise for understanding grain-growth phenomena in the entire HAZ by using the MC technique.