Shape control of TIG arc plasma by cusp-type magnetic field with permanent magnet

Abstract

The shape of arc plasma in gas-shielded arc welding is an important factor for the quality and efficiency of the welding. The arc plasma changes its shape by an external magnetic field because the arc is a flow of electricity and is subjected to the electromagnetic force. In this study, we examined the control of arc plasma by a cusp-type magnetic field. The field produces a high and low magnetic area alternatively, and changes the cross-section of the arc plasma from a circular to an elliptical shape. The previous study using solenoid coils to produce a cusp-type magnetic field reported that magnetized arc plasma provided deeper penetration. However, the solenoid device developed for the cusp magnetic field was too large in comparison with the size of the welding torch used for production welding. Therefore, this study investigated the magnetic control of arc plasma with permanent magnets that have recently become smaller in size and higher in intensity. Theoretical analysis model was constructed to determine the optimum arrangement of the magnets. This analysis requires a threedimensional numerical model because the temperature-, velocity-, and electromagnetic fields of arc plasma change threedimensionally by the additional magnetic field. It was analytically and experimentally shown in TIG arc welding that the arc shape could be elliptical cross-section even using the permanent magnets. Furthermore, our analysis showed that the effective magnetization direction of magnets was vertical, and this result was confirmed experimentally. As a result, we obtained the good bead appearance in the high-speed welding with this magnetic control.

Review of Thermal Plasma Simulation Technique

“…Nomura et al . investigated a 3D analysis model of an arc compacted using a cusp‐type magnetic field . In this case, the heat input is concentrated by tightening the shape of the arc on the ellipse along the moving direction, which is alternately affected by arranging four magnetic poles with different polarities.…”

Influence of the Longitudinal Magnetic Field on the Formation of the Bead in Narrow Gap Gas Tungsten Arc Welding

“…When an extra magnetic field is applied to the arc welding, many physical fields will be changed, such as the current density, heat flux, and fluid flow [17][18][19], and all these factors have a critical influence on the weld formation. To better apply the LMF in NG-GTAW, it is essential to study the heating characteristics of the magnetically oscillation arc (MOA) and the fluid flow in the molten pool.…”

Analysis and Characterization of the Weld Pool and Bead Geometry of Inconel 625 Super-TIG Welds

“…Therefore, studies were focused on arc characteristic improvements and performance of the arc pressure by developing various methods. Initially, some researchers tried the application of an external magnetic effect to regulate the arc characteristics and increased the travel speed to enhance the productivity of the welding [7].…”