Abstract: The effects of laser and varying volume fraction of He in Ar+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 arc 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 after adding laser, the arc becomes stable. An additional detaching force provided by the laser improves the metal transfer process, reduces the droplet diameter and increases the metal transfer frequency. Finally the welding stability enhances.

Key words: Laser-arc hybrid welding, Shielding gas, Welding stability