5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Secondary metallurgical processes such as Vacuum arc remelting (VAR) are extensively used for production of metal ingots with superior quality. The complex VAR process involves a wide range of physical phenomena including heat transfer with phase change (solidification/melting), Plasma arc, and the interplay between flow and electromagnetic field known as magnetohydrodynamics (MHD). The spatial and temporal distribution of the arc has a significant influence on the energy and electric current supplied to the ingot top surface. Thus, the evolution of the ingot is to a great extent controlled by the behavior of the arc. During the process, a notable fraction of current (~ 50%) in the vacuum region is transferred directly between the electrode and mold without flowing through the ingot known as “side-arcing”. The latter influences the electric current path in the whole system that in turn determines the hydrodynamics in the molten pool. Of note, the flow in the molten pool is driven by buoyancy, and self-induced electromagnetic force. Therefore, the amount of current which flows through the molten pool impacts the strength of the electromagnetic force that in turn determines the quality of the final ingot. Most often, the quality of the ingot is characterized by the shape of melt pool, i.e., the depth and thickness of mushy zone. The desired outcome of the VAR is a shallow melt pool that promotes unidirectional (upwards) solidification of the ingot and consequently formation of segregation-minimal alloy. The degree of macrosegregation is dependent on the slope of the solidus/ liquidus isotherms that in turn is related to the mushy zone depth. In fact, deep mushy zone results in a severe macrosegregation and subsequently inadequate mechanical properties, cleanliness, and yield. Therefore, the melt pool profile is often used as an indicator of the internal quality of the ingot. Generally, experimental analysis and measurements are quite difficult during the operation at the elevated temperature (~ 2000 K) of the process. Therefore, simulation tools can be applied to obtain a deeper knowledge of the VAR process. In this paper, a numerical study is performed to investigate the effect of “side arcs” on the pool profile of the VAR ingot. A series of simulations are performed considering different amount of “side arcs” (e.g. 20%, 50%, and 70%). Details of the analysis of the electric current, flow, and thermal/solidification fields are presented.