Research On Arc Behavior And Bead Appearance Of Narrow Gap Gas Metal Arc Welding Process With Strip Electrodes

Narrow gap MAG welding with Strip electrode is a new method of narrow gap welding. In this method,traditional circular welding wire is replaced by Strip electrode. The unique shape of strip electrode, the arc shape and dynamic features can improve the problem that it is difficult to heat the sidewalls and bottom of narrow gap groove. In our study, stainless steel strip electrode is applied, which size is 0.2×6mm2. The arc characteristics, dynamic features, weld forming characters and their influence factors of narrow gap MAG welding with Strip electrode are investigated. The process parameters, in which steady welding and fine bead appearance can be achieved, are also studied.At first, we describe the arc behavior and characteristic of droplet transfer. The principle of NG-MAG welding with strip electrodes is presented. Welding torch of NG-MAG welding with strip electrode is designed to meet the special require of narrow gap welding. Experimental results show that structure of the welding torch is simple and water, gas, electricity are feasible to connect. The deliver of strip electrode are stable and easy to dismantle and maintain. The experiment system of NG-MAG welding with strip electrodes is established, including welding system, high speed camera system, current and voltage acquisition system and gas protection system.Second, electrical signal in the welding process is acquired by current and voltage acquisition system. The arc in narrow gap is filmed by high speed camera system. The stability of arc combustion is analysed according to the wave shape of current and voltage. The arc movement in narrow gap is investigated with high speed camera system. The results show that arc oscillation is more obvious and the fluctuate of current and voltage would increase, as the strip feeding speed increases when the other parameters are constant. As the width of the gap increases, the arc would burn more steadily and its oscillation decreases,the fluctuate of current and voltage would decrease too. As arc voltage increases, the length of arc increases, arc oscillation is more obvious and the fluctuate of current and voltage increase. The research shows that arc burning has something to do with its oscillation, the basic reason is that the cathode spot moves, looking for the shortest electric pathway to suit for the least energy principle.Further more, bead appearance of NG-MAG with strip electrode under some typical process parameters is researched. The results show that when other parameters are settled, to some extent, as the strip feeding speed increases, bead appearance and sidewall fusion get better. As the width of the gap increases, arc oscillation decreases, the sidewall is less heated , thus its fusion and bead appearance are worse. As arc voltage increases, the length of arc increases, sidewall can be heated more, which leads to better fusion and bead appearance.At last, multiple layers welding experiments of NG-MAG with strip electrodes are performed, bead appearance is good, sidewall fusion and fusion between layers are fine, too. The results show that as a new welding method, NG-MAG is practicable when its welding parameters are appropriate matched.