This physical weld simulation study deals with the coarse grain heat-affected zone (CGHAZ) region's microstructure and the mechanical properties of naval bainitic steel after multi-pass welding. A welding thermal physical simulation experiment has been carried out by simulating different subzones (temperature range between 1100ý and 600 °C) in reheated coarse-grained heat-affected regions. The weld thermal cycles were tested between these temperature ranges using a thermo-mechanical simulator Gleeble®3800. The fixed low heat input 15 kJ/mm was used. The hardness, impact toughness at −50 °C, and notched tensile properties of the sub-CGHAZ regions were tested, and average results are reported. The altered CGHAZ microstructures were analyzed through optical microscopy, SEM, and TEM facility. This CGHAZ microstructure consisted of granular bainite, martensite, bainitic ferrite, and martensite austenite (M/A) islands, while base metal steel consisted of tempered bainite and martensite, and M/A islands. The first-pass CGHAZ region's mechanical properties were found worst due to coarse microstructure, whereas improved mechanical properties were obtained after the subsequent pass (second pass). The improvement in mechanical properties of sub-CGHAZ regions was attributed to the microstructure of soft granular bainite, shorter length and coarser width of bainitic ferrite, soft M/A islands, and carbides as well as changes in prior austenite grain size. The correlation between CGHAZ structure and mechanical properties is established in detail.

这种物理焊缝模拟研究涉及粗晶热影响区 (CGHAZ) 区域的显微组织和多道焊后海军贝氏体钢的机械性能。通过模拟再加热粗晶粒热影响区的不同子区（温度范围在 1100 至 600 °C 之间），进行了焊接热物理模拟实验。使用热机械模拟器 Gleeble®3800 在这些温度范围内测试焊接热循环。使用固定的低热输入 15 kJ/mm。测试了-50°C 下的硬度、冲击韧性和亚 CGHAZ 区域的缺口拉伸性能，并报告了平均结果。通过光学显微镜、SEM 和 TEM 设备分析了改变的 CGHAZ 微观结构。该 CGHAZ 显微组织由粒状贝氏体组成，马氏体、贝氏体铁素体和马氏体奥氏体（M/A）岛，而贱金属钢由回火贝氏体和马氏体以及M/A岛组成。由于显微组织粗大，第一道 CGHAZ 区域的机械性能最差，而在随后的道次（第二道次）后获得了改善的机械性能。亚 CGHAZ 区域力学性能的改善归因于软粒状贝氏体的显微组织、贝氏体铁素体的更短的长度和更粗的宽度、软 M/A 岛和碳化物以及原始奥氏体晶粒尺寸的变化。详细建立了CGHAZ结构与力学性能之间的相关性。和 M/A 岛。由于显微组织粗大，第一道 CGHAZ 区域的机械性能最差，而在随后的道次（第二道次）后获得了改善的机械性能。亚 CGHAZ 区域力学性能的改善归因于软粒状贝氏体的显微组织、贝氏体铁素体的更短的长度和更粗的宽度、软 M/A 岛和碳化物以及原始奥氏体晶粒尺寸的变化。详细建立了CGHAZ结构与力学性能之间的相关性。和 M/A 岛。由于显微组织粗大，第一道CGHAZ区域的机械性能最差，而在随后的道次（第二道次）后获得了改善的机械性能。亚 CGHAZ 区域力学性能的改善归因于软粒状贝氏体的显微组织、贝氏体铁素体的更短的长度和更粗的宽度、软 M/A 岛和碳化物以及原始奥氏体晶粒尺寸的变化。详细建立了CGHAZ结构与力学性能之间的相关性。亚 CGHAZ 区域力学性能的改善归因于软粒状贝氏体的显微组织、贝氏体铁素体的更短的长度和更粗的宽度、软 M/A 岛和碳化物以及原始奥氏体晶粒尺寸的变化。详细建立了CGHAZ结构与力学性能之间的相关性。亚 CGHAZ 区域力学性能的改善归因于软粒状贝氏体的显微组织、贝氏体铁素体的更短的长度和更粗的宽度、软 M/A 岛和碳化物以及原始奥氏体晶粒尺寸的变化。详细建立了CGHAZ结构与力学性能之间的相关性。