标准地铁铝合金MIG自动焊气孔缺陷研究

Study on porosity defects of standard metro aluminum alloy MIG automatic welding

针对采用MIG自动焊焊接标准地铁铝合金车顶型材时,易出现较多气孔缺陷的问题进行了分析探讨。通过采用控制变量的方法,保持焊接电流、电弧电压、焊接速度一致,分别改变保护气体流量的大小和焊枪的摆动情况,对焊缝进行成形、焊接性分析,并进行渗透检测,观察研究气孔缺陷的情况。研究发现:当控制焊接电流、电弧电压、焊接速度一定,保护气体流量<22L/min时,焊缝成形不良,同时有较多气孔产生;当保护气体流量在25~28L/min时,焊缝成形均较好,并且肉眼可见气孔明显减少,渗透检测后发现,气孔缺陷基本消失;当保护气体流量过大时,熔池保护效果下降,电弧温度高,有损伤母材的风险。控制焊接电流、电弧电压、焊接速度和保护气体流量一定,使焊枪摆动,焊枪摆动产生的气孔明显比焊枪不摆动产生的气孔少。

This paper analyzed and discussed the problem of porosity defects when MIG automatic welding is used to weld standard metro aluminum alloy roof profiles.By using the method of controlling variable,the welding current,arc voltage and welding speed are kept consistent,and the size of the protective gas flow and the swing of the welding gun are changed respectively.The weld formation and weldability analysis are carried out on the welding seam after welding,and the penetration detection is carried out to observe and study the porosity defects.It is found that when the welding current,arc voltage and welding speed are controlled,and the shielding gas flow is less than 22L/min,the weld is poorly formed and there are more pores.When the shielding gas flow rate is between 25L/min and 28L/min,the weld formation is good,and the visible porosity is obviously reduced,and the porosity defect is basically disappeared after penetration inspection.When the shielding gas flow is too large,the protection effect of the molten pool decreases,the arc temperature is high,and the risk of damaging the base metal is high.Control welding current,arc voltage,welding speed and protective gas flow to make the welding gun swing,the porosity generated by the welding gun swing is significantly less than the porosity generated by the welding gun without swing.