超声辅助熔化极惰性气体保护(Ultrasonic assisted metal inert gas，U-MIG)焊是一种新型熔化极焊接方法，利用外加声场将相应声学效果引入焊接熔池达到改善接头性能的目的。通过试验系统化研究超声对电弧形态、熔滴过渡以及接头宏观形貌的作用规律，主要目标是更好地理解超声在不同焊接条件下的作用特点。对高速摄像采集的电弧数据进行处理，结果发现随电弧电压增加，超声对电弧的压缩效果也逐渐增大；而随送丝速度增加，焊接电流增大，电弧压缩效果减弱。针对熔滴受力特点分析，可以看出超声作用后熔滴会受到一个促进熔滴过渡的附加力作用。在焊接电流为200 A时，该附加力达到最大，约为2.8×103 N，继续增大焊接电流，该附加力逐渐降低。对比不同送丝速度时焊缝宏观形貌，结果显示为了获得更高的焊接效率不能无限提高送丝速度，存在一个最佳的参数匹配值。结合平面驻波理论分析，随温度增加，声辐射力逐渐减弱，这在一定程度上也会削弱附加力作用效果。利用熔池薄膜模型探讨电弧、熔滴过渡以及熔池振荡三者之间的关系，超声对电弧形态、熔滴过渡的影响均可改变熔池的振荡特性，这间接表现为接头形貌的改变。通过试验与理论分析，为U-MIG焊接方法进一步发展与应用打下坚实基础。
Ultrasonic assisted metal inert gas welding (U-MIG), as a new welding method, introduces corresponding acoustic effects to weld pool applying added ultrasonic field. Systematic experiments researched the effect of ultrasound on arc shape, droplet transfer and joints macroscopic morphology is designed to better understand the characteristics of ultrasonic under different welding conditions. Arc images recorded by high-speed camera are processed and analyzed. It revealed that the compression effect of ultrasound on arc increases with the welding voltage increases. However, with the increase in the wire feed speed, welding current increases, the arc compression effect becomes smaller and smaller. The analysis of force mechanism of droplet transfer shows that an additional force is provided to promote droplet transfer under the action of the ultrasonic wave. When the welding current is 200 A, this additional force reaches its maximum, the value is about 2.8×103 N. If the welding current is continuously increased, the additional force will be gradually decreased. Compared with macro-morphology of weld with different wire feed speeds, it reveals the variations welding current can not be infinitely increased, and there is an optimum parameter values. The acoustic field analysis is conducted based on plane standing theoretical. With increasing temperature, acoustic radiation force gradually decreases, which may counteract the effect of the additional force. The weld pool film model is applied to investigate the relationship between arc, droplet transfer and weld pool oscillation. The effects of ultrasound on arc and droplet transfer can change the oscillation characteristics of weld pool. It shows indirectly the changes of the macro-morphologies of weld joints. By experiments and theoretical analysis, this result has laid a solid foundation for the further development and application of U-MIG welding process.
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