Fu Jun, El-Fallah G M A M, Tao Qing, Dong Hongbiao
School of Engineering, University of Leicester, Leicester LE1 7RH, UK.
Nanjing Iron & Steel United Co., Ltd., Nanjing 210044, China.
Materials (Basel). 2023 Apr 17;16(8):3150. doi: 10.3390/ma16083150.
High heat input welding can improve welding efficiency, but the impact toughness of the heat-affected zone (HAZ) deteriorates significantly. Thermal evolution in HAZ during welding is the key factor affecting welded joints' microstructures and mechanical properties. In this study, the Leblond-Devaux equation for predicting phase evolution during the welding of marine steels was parameterized. In experiments, E36 and E36Nb samples were cooled down at different rates from 0.5 to 75 °C/s; the obtained thermal and phase evolution data were used to construct continuous cooling transformation diagrams, which were used to derive the temperature-dependent parameters in the Leblond-Devaux equation. The equation was then used to predict phase evolution during the welding of E36 and E36Nb; the quantitative experimental phase fractions of the coarse grain zone were compared with simulated results to verify the prediction results, which are in good agreement. When heat input is 100 kJ/cm, phases in the HAZ of E36Nb are primarily granular bainite, whereas for E36, the phases are mainly bainite with acicular ferrite. When heat input increases to 250 kJ/cm, ferrite and pearlite form in both steels. The predictions agree with experimental observations.
高热输入焊接可以提高焊接效率，但热影响区（HAZ）的冲击韧性会显著恶化。焊接过程中热影响区的热演变是影响焊接接头微观结构和力学性能的关键因素。在本研究中，对用于预测船用钢焊接过程中相变的勒布朗德 - 德沃克斯方程进行了参数化。实验中，将E36和E36Nb试样以0.5至75℃/s的不同冷却速率冷却；所获得的热演变和相变数据用于构建连续冷却转变图，进而推导勒布朗德 - 德沃克斯方程中与温度相关的参数。然后使用该方程预测E36和E36Nb焊接过程中的相变；将粗晶区的定量实验相分数与模拟结果进行比较以验证预测结果，二者吻合良好。当热输入为100kJ/cm时，E36Nb热影响区的相主要为粒状贝氏体，而对于E36，相主要为贝氏体和针状铁素体。当热输入增加到250kJ/cm时，两种钢中均形成铁素体和珠光体。预测结果与实验观察结果一致。
