Analysis of microstructure and mechanical properties of resistance spot welded 22MnB5 hot stamping steel
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摘要: 采用不同工艺参数对22MnB5热成形钢进行点焊试验，分析工艺参数对焊点性能的影响，并研究22MnB5热成形钢点焊接头组织演变及组织—性能关系. 结果表明，焊点熔核直径与拉剪力两者表现出正相关关系. 与电极压力相比，焊接电流对焊点力学性能具有更大的影响. 焊点各区域的组织演变导致了明显的硬度差异. 熔核区、过临界热影响区、亚临界热影响区及母材区均为马氏体组织. 临界热影响区为铁素体 + 马氏体双相组织，导致硬度显著降低. 该软化区增加了焊点失效时的承载能力及能量吸收能力，促使接头失效以“熔核拔出”方式发生.Abstract: 22MnB5 hot stamping steel was resistance spot welded using different welding procedures. The effects of welding parameters on weldability were investigated, and the microstructural evolution of spot weld and the relation of microstructure-mechanical performance were studied. The results show that there is a positive correlation between nugget diameter and tensile shear load. Compared to electrode force, welding current displays a more critical effect on mechanical performance of spot weld. The difference in micro-hardness across the whole weld is determined by the microstructural evolution. Fully martensitic microstructure appears in the whole weld, except for inter-critical heat affected zone(IC-HAZ), which has the lowest hardness due to a duplex microstructure of ferrite and martensite. This softening phenomenon improves load-carrying capacity and energy absorption of spot weld in mechanical failure condition, leading to the occurrence of pullout failure mode.
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Keywords:
- resistance spot welding /
- hot stamping steel /
- mechanical properties /
- softening zone
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