铍青铜薄片预置镍中间层的微电阻点焊

Micro-resistance spot welding of Ni interlayer of QBe_2 sheets

为提高铍青铜薄片微电阻点焊的接头性能,采用0.05 mm厚纯镍作为中间层对0.1 mm厚铍青铜进行焊接,对比分析预置镍层与未预置镍层时的点焊接头性能,并综合研究中间层的作用机理。结果表明:铍青铜薄片预置镍中间层后,点焊接头焊核尺寸增大,接头抗拉剪力提高79.2%,断口结合面撕裂区呈韧性断裂特征,接头热影响区组织为细小的胞状晶、焊核中心及底部区域为等轴晶;镍中间层的添加改变接头连接机制,整个接头由熔化焊及钎焊连接组成。另外,通过产热分析发现,预置镍中间层增加镍与铍青铜之间的接触电阻和镍层体电阻,接头总产热电阻增大;镍中间层通过增大焊接热输入以及扩大接头连接区域面积使得接头的质量提高。

In order to improve the micro-resistance spot welding （MRSW） joint performance,two beryllium bronze sheets with thickness of 0.1 mm were welded with 0.05 mm-thick pure nickel foil as interlayer.The effects of interlayer on joint properties were investigated by the comparison of joints welded with or without Ni interlayer.The results show that the larger size of nuggets welding with Ni interlayer is observed,correspondingly,the shearing force increases by 79.2%.The ductile fracture is shown at faying surface.The cross section morphology of typical MRSW joint with Ni interlayer is characterized as fine cellular crystal in HAZ and equiaxed crystal in the centre or bottom area of joint.When welding with nickel interlayer,the joint is comprised of the fusion welding at center and brazing at peripheral region.As result,the bounding mechanism is changed.Further,the analysis results of thermal generation during MRSW show that Ni interlayer bring forth the contact resistance between Ni foil and beryllium bronze sheet and the bulk resistance of Ni foil which results in the increased resistance participated in whole heat generation.The improved MRSW joint performance results from the increased heat generation and enlarged brazing bonding area.