研究目的

Understanding the arc dynamics during VAR is important for controlling the final quality of the ingot, as the spatial and temporal distribution of the arc dictates the electric current and energy inputs at the ingot top, which in turn affect the hydrodynamics of the metal in the molten pool and the solidification conditions of the ingot.

研究成果

The main finding of the present study is that the motion of the arc luminosity centroid describes three regular patterns during the melt. The arc dynamics was found to be most of the time periodic, asymmetrical, and strongly correlated to the evolution of the stirring magnetic field. The arc centroid exhibited three regular displacement patterns throughout the melt. A common characteristic to all three patterns was the relative stability of the centroid during stirring plateaus and its rapid motion during stirring ramps. An evolution towards a much more centered distribution of the centroid was observed with the arc power decrease during the hot-topping phase. Possible implications of the observed arc dynamics on the final quality of the VAR ingot are discussed.

研究不足

The existence of an asymmetrical arc motion has important implications for the modelling of the VAR ingot. It puts under question the classical assumption made in most models of a time-averaged axisymmetric and quasi-stationary arc distribution. Models based on a 2D axisymmetric geometry might thus be not sufficient. A realistic representation of the arc behaviour would require turning to models based on a 3D geometry.