Application of DC Plasma Driven by AC Magnetic Field to Surface Melting of Steels

摘要

In this paper, a novel application of thermal plasma to melt the surface of steels is investigated through fundamental experiments and theoretical analyses. In the experiments, the effects of basic parameters such as direct current (DC) plasma current, alternative current (AC) magnetic flux density, argon gas flow rate and nozzle diameter on the drive stroke of plasma were analyzed. Then, the results were compared to simulations obtained by the three dimensional magnetohydrodynamics (MHD) analyses, which enabled fully coupled analysis between electromagnetic field and thermo-fluid flow field using finite volume method. The simulation results showed good correspondence with experimental data. On the basis of these results, application experiments were carried out, in which steel sample was moved perpendicular to the direction of DC plasma driven by AC magnetic field so as to enable to fuse widely. The length of the melted zone was about 150mm. The melted zone at the surface of the steel specimen was 50-100mm in width and 5-8mm in depth. The surface of the melted zone was smooth and had good cleanliness evaluated in the cross-sectional observation by a microscope.