Development of a Finite Element Model for the HAZ Temperature Field in Longitudinal Welding of Pipeline Steel

In this study, a novel hybrid heat source model was developed to simulate the welding temperature field in the heat-affected zone (HAZ) of X80 pipeline steel. This model replicates welding conditions with high accuracy and allows flexible three-dimensional adjustments to suit various scenarios. Its development involved the innovative integration of microstructural crystallography information with a multi-scale calibration and validation methodology. The methodology focused on three critical aspects: the weld interface morphology, the location of the Ac1 temperature, and the size of prior austenite grains (PAG). The morphology of the weld interface was calibrated to align closely with experimental observations. The model's prediction of the Ac1 location in actual welded joints exhibited a deviation of less than +/- 0.3 mm. Furthermore, comparisons of reconstructed PAG sizes between thermal simulation samples and actual HAZ samples revealed minimal discrepancies (5 mu m). Validation results confirmed that the calibrated model accurately describes the welding temperature field, with reconstructed PAG size differences between simulation and experimental results being less than 9 mu m. These findings validate the accuracy of the calibrated model in predicting welding temperature fields. This research introduces a novel framework for the development of heat source models, offering a robust foundation for improving welding performance and controlling microstructure in different regions during the welding process of high-strength low-alloy (HSLA) steel.