Welding procedure qualification of Q345 grade fire-resistant steel based on Jmat-pro calculation

The welding process of two Q345 grade low Mo (about 0.25 wt.%) fire-resistant steels will be calculated and evaluated in this paper. The continuous cooling transformation (CCT) curve and isothermal transformation (TTT) curve of test steel were calculated by Jmat-pro software. The welding processes of steels were evaluated by measuring the continuous cooling transition (SH-CCT) curves of welding heat affected zone. The test results show that when the actual cooling time of Q1 steel is t 8/5>43s, cracking does not occur in the HAZ of welding and near the fusion zone, while when t 8/5 44s, cracking does not occur in the welding heat affected zone and the vicinity of the fusion zone, while when t 8/5<44s, cracking may occur in the heat affected zone or the fusion zone. In addition, Jmat-pro software has a certain accuracy for the calculation of Ac 3, but has a large error for the continuous cooling transformation (CCT) curve, especially the difference between the calculated value and the measured value of Q2 steel is larger, which only has reference value.