A study on the numerical analysis of magnetic flux density by a solenoid for magnetically impelled arc butt welding

Abstract

The magnetically impelled arc butt (MIAB) welding process uses a rotating arc as its heat source and is known as an efficient method for pipe butt welding. The arc in the gap of the pipe butt joints is rotated along the circumferential weld line by the electromagnetic force resulting from the interaction of the arc current and the magnetic field in the gap. The electromagnetic force is determined by the magnetic flux density in the gap, the arc current and the arc length (i.e. gap size). In particular, the radial magnetic flux density is an important factor in arc rotation and weld quality. This paper proposes a two-dimensional finite element model for the analysis of magnetic flux density distributions in the MIAB welding process. The magnetic flux density is mainly dependent on the gap size between two pipes, the position of the exciting coil that generates the magnetic field, the exciting current in the coil, and the relative permeability of the pipes. Thus, the relations between the magnetic flux density and the above main factors were investigated through experiments and analyses. Experiments were performed on the steel pipes (outer diameter 48.1mm and thickness 2.0mm). From the analyses and experiments, it was revealed that the magnetic flux density in the gap between the pipes increases when there is an increasing exciting current and relative permeability, and a decreasing distance from the gap centre to the coil and gap size. It is considered that the numerical analysis model proposed in this study can be used as a useful means when designing an electromagnetic system for the MIAB welding machine.