Li Shuoshuo, Wang Yanjun, Hu Bin, Tao Wu, Yang Shanglu, Luo Haiwen
State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China.
Department of Ferrous Metallurgy, University of Science and Technology Beijing, Beijing 100083, China.
PNAS Nexus. 2022 Aug 18;1(4):pgac161. doi: 10.1093/pnasnexus/pgac161. eCollection 2022 Sep.
For many decades, several classical formulas on carbon equivalent (CE) have been widely used for evaluating the weldability of steels. Unfortunately, a single CE is impossible for various types of steels. In this study, the resistance spot weldability of medium-Mn steels was investigated. In particular, the influences of paint baking processes at different temperatures on the mechanical properties, fracture mode, and microstructure of weldment were studied. It was found that the paint baking above 170°C can change the tensile-shear failure of weldment from the undesired interfacial failure to the desired pull-out one, because the shrinkage of weldment during welding was compensated by the thermal expansion during the baking, leading to the "cold welding" realized for solid joining. Furthermore, a shrinkage-based criterion (∆) was established for evaluating the weldability of greater range of alloyed steels more accurately and robustly than CE. The proposed criterion on measuring the weldability of high alloyed steels opens a promising path forward for designing a new generation of advanced high strength steels requiring good weldability.
几十年来，几个关于碳当量（CE）的经典公式被广泛用于评估钢材的可焊性。不幸的是，对于各种类型的钢材，单一的碳当量是不可能的。在本研究中，对中锰钢的电阻点焊可焊性进行了研究。特别地，研究了不同温度下的烤漆工艺对焊件力学性能、断裂模式和微观结构的影响。结果发现，170°C以上的烤漆可以使焊件的拉伸剪切失效从不理想的界面失效转变为理想的拉脱失效，因为焊接过程中焊件的收缩被烘烤过程中的热膨胀所补偿，从而实现了固态连接的“冷焊”。此外，还建立了一个基于收缩的准则（∆），用于比碳当量更准确、更可靠地评估更大范围合金钢的可焊性。所提出的测量高合金钢可焊性的准则为设计新一代要求良好可焊性的先进高强度钢开辟了一条充满希望的道路。
