22MnB5热成形钢点焊接头组织演变与性能分析
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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.
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(ICHAZ), 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.
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(ICHAZ), 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.
引文
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[2]Lu Y,Peer A,Abke T,et al.Subcritical heat affected zone softening in hot-stamped boron steel during resistance spot welding[J].Materials and Design,2018,155:170-184.
[3]Naderi M,Ketabchi M,Abbasi M,et al.Analysis of microstructure and mechanical properties of different high strength carbon steels after hot stamping[J].Journal of Materials Processing Technology,2011,211(6):1117-1125.
[4]George R,Bardelcik A,Worswick M J.Hot forming of boron steels using heated and cooled tooling for tailored properties[J].Journal of Materials Processing Technology,2012,212(11):2386-2399.
[5]赵洪运,刘洪伟.22MnB5超高强钢焊接组织与性能[J].焊接学报,2014,35(2):67-69,78.Zhao Hongyun,Liu Hongwei.Microstructure and properties of TIG welded 22MnB5 ultra high strength steel[J].Transactions of the China Welding Institution,2014,35(2):67-69,78.
[6]Karbasian H,Tekkaya A E.A review on hot stamping[J].Journal of Materials Processing Technology,2010,210(15):2103-2118.
[7]Merklein M,Lechler J.Investigation of the thermo-mechanical properties of hot stamping steels[J].Journal of Materials Processing Technology,2006,177(1-3):452-455.
[8]Choi H S,Park G H,Lim W S,et al.Evaluation of weldability for resistance spot welded single-lap joint between GA780DP and hotstamped 22MnB5 steel sheets[J].Journal of Mechanical Science and Technology,2011,25(6):1543-1550.
[9]Zhao D W,Wang Y X,Liang D J,et al.Modeling and process analysis of resistance spot welded DP600 joints based on regression analysis[J].Materials and Design,2016,110:676-684.