永磁体磁场对铝合金电阻点焊力学性能及微观组织的影响

Impact of external magnetic field generated by permanent magnet on mechanical property and microstructure of aluminum alloy resistance spot weld

关键词:  电阻点焊  外加磁场  铝合金  力学性能  断裂模式

Key words:  resistance spot welding  external magnetic field  aluminum alloy  mechanical property  failure mode

摘要:

文中采用永磁体作为磁场源,研究了外加稳定磁场对铝合金电阻点焊的熔核尺寸、焊点力学性能、断裂模式以及微观组织的影响.文中还对熔核直径与峰值载荷之间的关系进行了研究.结果表明,永磁铁的工作距离对熔核直径大小具有重要影响.距离越近,外磁场促进熔核直径增加的效果越明显.外加磁场能够有效增加焊点熔核直径、提高点焊接头的剪切拉伸强度、促进断裂模式由界面断裂向纽扣断裂转变.在不同工艺参数下,熔核直径增长在3.5%~14.1%,剪切拉伸力可提高4%~25%.外加磁场可促进点焊熔核内等轴晶的形成和细化.峰值载荷与熔核尺寸、工件厚度、母材极限抗拉强度的乘积具有良好的线性关系.

Abstract:

This paper systematically analyze the effect of external magnetic field (EMF) generated by permanent magnetic on the nugget size, mechanical properties and failure mode of aluminum alloy resistance spot welds. The relationship between nugget size and peak load was also studied. The results show that the work distance between two permanent magnets has significant effect on the nugget diameter. The smaller the distance is, the larger the nugget diameter is. The nugget diameter and tensile-shear force were increased under the help of EMF. Under different welding parameters, the nugget diameter can be increased by 3.5%~14.1%, and the tensile-shear force enhanced 4~25%. The EMF promotes the failure mode change from interfacial failure to pullout failure. The EMF can improve the strength-toughness properties and refine grain size. The relationship between peak load and the product of nugget diameter, workpiece thickness and base material ultimate tensile strength shows well linear relation.