Microstructure and Tensile-Shear Properties of Resistance Spot-Welded Medium Mn Steel

Metals

Guisheng Zou¹  Qiang Jia¹  Lei Liu¹  Y. Norman Zhou²  Wei Guo³  Zhiling Tian⁴  Yun Peng⁴ 

[1] Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada;School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, China;Welding Research Institute, Central Iron and Steel Research Institute, Beijing 100081, China;

关键词: resistance spot-welding;    medium manganese steel;    weldability;    microstructure;    tensile-shear properties;   

DOI  :  10.3390/met8010048

来源: DOAJ

【 摘 要 】

The medium Mn steels are gaining increasing attention due to their excellent combination of mechanical properties and material cost. A cold-rolled 0.1C5Mn medium Mn steel with a ferrite matrix plus metastable austenite duplex microstructure was resistance spot-welded with various welding currents and times. The nugget size rose with the increase of heat input, but when the welding current exceeded the critical value, the tensile-shear load increased slowly and became unstable due to metal expulsion. The fusion zone exhibited a lath martensite microstructure, and the heat-affected zone was composed of a ferrite/martensite matrix with retained austenite. The volume fraction of retained austenite decreased gradually from the base metal to the fusion zone, while the microhardness presented a reverse varying trend. Interfacial failure occurred along the interface of the steel sheets with lower loading capacity. Sufficient heat input along with serious expulsion brought about high stress concentration around the weld nugget, and the joint failed in partial interfacial mode. Pull-out failure was absent in this study.

【 授权许可】

Unknown