Role of Intercritical Annealing in Enhancing the Cross-Tension Property of Resistance Spot-Welded Medium Mn Steel
Role of Intercritical Annealing in Enhancing the Cross-Tension Property of Resistance Spot-Welded Medium Mn Steel
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DOI：
10.1007/s11665-020-05440-2
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发表时间：
2021-01
影响因子：
2.3
通讯作者：
Bing Zhao;Yuanfang Wang;Kai Ding;Guanzhi Wu;Tao Wei;H. Pan;Yulai Gao
中科院分区：
文献类型：
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作者：
Bing Zhao;Yuanfang Wang;Kai Ding;Guanzhi Wu;Tao Wei;H. Pan;Yulai Gao
在第三代先进高强度钢中，中锰钢是现代汽车工业中最有前途的候选者之一。然而，它们的可焊性和相应的较差的力学性能给其应用带来了挑战。本研究采用电阻点焊（RSW）技术连接7Mn钢。焊后热处理包括临界间退火，以调整熔核组织。在这种情况下，在RSW过程中被捕获的C和Mn能够充分扩散，从而减小了晶界脆化。同时，接头发生奥氏体的逆转转变，有利于形成由铁素体和奥氏体组成的混合组织。在此基础上，RSW 7Mn钢的抗拉强度（CTS）最高可达11.6 kN，塑性变形显著，呈扣拉断裂模式。本研究为中Mn钢RSW接头的微观组织和最终CTS的定制提供了一种可行的方法，可以指导RSW工艺的优化。
Among the third-generation advanced high-strength steels, medium Mn steels are one of the most promising candidates in the modern automotive industry. However, their application is challenged by the weldability and corresponding poor mechanical property. In this study, the resistance spot welding (RSW) technique was used to join 7Mn steels. A post-weld heat treatment containing intercritical annealing was followed to tune the nugget microstructure. In this case, the trapped C and Mn during RSW can fully diffuse, diminishing the grain boundary embrittlement. Meanwhile, the austenite reversion transformation occurs in the joint, facilitating the formation of a mixed microstructure consisting of ferrite and austenite. With these efforts, the cross-tension strength (CTS) of the RSW 7Mn steel can reach as high as 11.6 kN with outstanding plastic deformation, giving rise to a button pullout fracture mode. This study provides an accessible approach to tailor the microstructure and final CTS of RSW joints of the medium Mn steel, which can guide the optimization of the RSW process.