中文摘要：

研究激光和Ar＋He混合气体中He气体体积分数对激光＋双丝脉冲MAG复合焊焊接稳定性的影响。搭建激光＋双丝脉冲熔化极活性气体保护（Metal active-gas，MAG）复合焊焊接系统，利用LabVIEW信号采集系统采集焊接电流和电弧电压波形，借助高速摄像系统同步拍摄电弧形态和熔滴过渡过程，实时监测焊接过程。观察后丝短路和前丝断弧情况并对前丝电弧电压进行单因素方差分析，研究Ar＋He混合气体中He气体体积分数对焊接稳定性影响；比较焊接过程中激光的有无对熔滴过渡的影响，分析激光对焊接稳定性影响。结果发现随着He气体体积分数增大，后丝对应短路次数增多，当He气体体积分数为50％时，前丝出现断弧现象，大于50％，断弧时间随之增加，焊接稳定性变差；激光＋双丝脉冲MAG复合焊和双丝脉冲MAG复合焊相比，加入激光可稳定电弧，为熔滴提供一附加力，该力促进熔滴过渡，使熔滴过渡尺寸减小，加大过渡频率，改善熔滴过渡，提高焊接稳定性。

英文摘要：

The effects of laser and varying volume fraction of He in At＋He gas mixture on welding stability in laser＋ twin-electrode pulsed metal active-gas（MAG） hybrid welding are investigated. A laser＋twin-electrode pulsed MAG hybrid welding system is developed. In the welding process, the waveforms of welding current and arc voltage are acquired through LabVIEW signal acquisition system while the arc behavior and metal transfer process are monitored by high-speed photography system synchronously. Then the whole welding process can be monitored constantly. The conditions of short circuit and arc interruption for the trailing wire and leading wire are studied respectively and one-way anova analysis is made for are voltage of the leading wire. So the effect of He gas volume fraction in Ar＋He gas mixture on welding stability is studied. The change of metal transfer in the welding process is investigated to analyze the effect of laser on welding stability. Experimental results show that with the increase of He gas volume fraction, the number of short circuit for the trailing wire increases. When He gas volume fraction is equal to 50%, arc interruption occurs. The number of arc interruption times increase rapidly with increasing He gas volume fraction when He gas volume fraction is over 50%. The welding stability becomes bad. Compared laser＋twin-electrode pulsed MAG hybrid welding and twin-electrode pulsed MAG welding, it shows that af~ adding laser, the arc becomes stable. An additional detaching foree provided by the laser improves the metal transfer process, reduces the droplet diameter and increases the metal transfer frequency. Finally the welding stability enhances.