1200 MPa级双相钢电阻点焊接头失效原因

FAILURE CAUSES OF RESISTANCE SPOT WELDED JOINTS OF 1200 MPa DUAL PHASE STEEL

对厚度1.4 mm、1200 MPa高强双相钢进行了电阻点焊工艺试验,结合拉伸试验结果,分析了接头界面断裂及纽扣断裂失效的原因。结果表明:相同焊接工艺下,纽扣断裂吸能效果较好,高达45 kJ左右。缩孔类焊接缺陷的存在会导致接头结合面处可承受的极限剪切力降低,实际熔核直径变小,裂纹容易在此处萌生,倾向于界面断裂失效;焊核无缺陷情况下,熔核强度高,焊点圆周附近产生较大的应力集中,裂纹最先在此处产生,随加载力增大,裂纹向热影响区扩展,并贯穿整个板材厚度,最终表现为纽扣断裂失效。

the resistance spot welding process test of high-strength dual phase steel with thickness of 1.4 mm and 1200 MPa was carried out.Combined with the tensile test results,the causes of joint interface fracture and button fracture failure were analyzed.The results show that under the same welding process,the energy absorption effect of button fracture is better,up to about 45 kJ.The existence of shrinkage welding defects will lead to the reduction of the ultimate shear force at the joint interface,the reduction of the actual nugget diameter,the crack is easy to initiate here,and tends to interface fracture failure;When the nugget is free of defects,the nugget strength is high,and a large stress concentration occurs near the circumference of the solder joint.The crack first occurs here.With the increase of loading force,the crack extends to the heat affected zone and runs through the whole plate thickness,and finally shows as button fracture failure.