车用DP600和DC54D涂胶与未涂胶电阻点焊研究

对异种钢不同板厚涂胶与未涂胶DP600双相钢和超低碳DC54D电阻点焊进行了研究。深入分析了不同焊接时间下焊接接头显微组织、显微硬度、拉剪性能及扫描断口。研究结果表明,随着焊接时间的延长,焊点直径增大。当焊接时间为2周波时,热影响区为"半月形",延长焊接时间,熔核形状由"蝶形"转变为"椭型"。由于DC54D对熔核区碳含量的稀释作用,熔核区显微硬度低于热影响区硬度。拉伸-剪切试验中,当焊接时间为13-19周波时,涂胶与未涂胶接头拉剪强度趋于稳定。未涂胶接头的最大拉剪强度为5.45kN,涂胶接头的最大拉剪强度为5.15kN。当焊接电流为9kA、电极压力为2.6kN、焊接时间为13-19周波时,涂胶的焊接接头能得到优异的力学性能,但是比未涂胶接头略差。未涂胶与涂胶接头断裂均发生在DC54D侧。

Study on Vehicle-used DP600 and DC54D Glued and Un-glued Resistance Spot Welding

Joining of a dual-phase steel DP600 and an ultra-low carbon steel DC54D dissimilar couple was investigated by RSW in current study. The microstructure, micro-hardness and tensile-shear properties were analyzed in-depth. The results show that the weld diameter increased as the welding time prolonged. The heat-affected zone exhibited lune shape when the welding time was 2 cycles. With the increase of welding time, the weld was changed from butterfly shape to elliptic shape. The micro-hardness of the fusion zone was lower than that of the heat-affected zone due to the dilution of DC54D. In tensile-shear testing,the tensile-shear strength tended to be stable when the welding time was 13-19 cycles. The largest tensile-shear strength was 5.15 kN and 5.45 kN of glued and un-glued welded spot, respectively. When the welding current, electrode force was 9 kA and 2.6 kN,and the welding time was 13-19 cycles, the glued resistance spot welded joint could gain a well mechanical properties but worse than the un-glued. Both of the glued and un-glued welds fractured on DC54D side.