Analysis of arc rotation characteristics in magnetically impelled arc butt welding based on Lorentz force

Magnetically impelled arc butt (MIAB) welding is a cutting-edge joining method developed specifically for tubular components, mainly used in the automotive industry. Arc rotation velocity is an important process parameter which affects welding quality. However, there is a lack of a simple and efficient velocity acquisition method that does not interfere with the welding process. In this paper, the characteristics of arc rotation in magnetically impelled arc butt welding are analyzed from the perspective of Lorentz force for the first time, and a potential simple and efficient velocity acquisition method based on voltage waveform is proposed. The results show that the voltage is different due to the uneven distribution of magnetic flux density on the circumference of the tube end and the different deflection amplitude of arc under different magnetic flux density. Therefore, the periodicity of the voltage waveform is corresponded to the arc rotation. The transmission of plasma in the rotating arc is maintained by collision ionization of electrons and neutral particles. With the increase of exciting current, the arc deflection amplitude and voltage increase, resulting in more heat input being distributed into the gap region, which is conducive to the occurrence of collision ionization and the increase of arc rotation velocity (from 26.2 m/s to 36.2 m/s), the melting uniformity of tube end is improved effectively, and the difference of mechanical properties between the top and bottom of the joint is also reduced.