热冲压高强钢电阻+激光组合点焊工艺

Study on combination process of resistance and laser spot welding for hot stamping boron steel

为避免热冲压高强钢电阻点焊在热输入较大时产生飞溅和满足激光点焊装配要求,提出一种将电阻点焊和激光点焊组合的新焊接工艺方法.通过电阻+激光组合点焊工艺获得了热冲压高强钢焊接接头,分析了接头各区域的显微组织、显微硬度分布、力学性能,并分析了断裂模式及其断裂机理.结果表明,电阻+激光组合点焊接头明显分为电阻焊接区和激光焊接区.母材和激光焊核区硬度值较大,与回火区对应的软化区硬度值下降约60%,激光环外侧软化区为拉剪断裂薄弱环节.此种组合工艺获得的焊接接头相对于单独电阻点焊或激光点焊强度和韧性都有明显提高.

In order to avoid splash when large amount of heat of resistance spot welding is input for hot stamping high strength steel and meet the strict requirements for assembly under laser spot welding,a new welding process that is combination of resistance spot welding and laser spot welding is proposed.The welding joints were obtained through the combination of resistance and laser spot welding process.The microstructures of various regions for welding joints were analyzed with scanning electron microscopy.The micro-hardness distribution of welding joints was tested by micro-hardness testing.The mechanical properties of welded joints under different welding process were obtained by using universal tensile machine,and the fracture mode and fracture mechanism were analyzed.The results show that the welding area under process of combination of resistance and laser spot welding is composed of resistance welding zone and laser welding zone.The microstructure of laser nugget zone and base metal are lath martensite.The heat affected zone locates outside of laser ring and near the base metal,and the nug-get of original resistance spot welding are tempering organization.The hardness of laser nugget zone is the same as that of base metal,and the hardness of softening zone corresponding to the tempering zone decreases to 60% of that of base metal.The softening zone outside of laser ring is the weak region for tensileshear fracture.The obtained welding joints by this combination process have better load carrying capacity and toughness than those by individual resistance spot welding or laser welding.