A Coupled Magnetohydrodynamics (MHD) and Thermal Stress-Strain Model to Explore the Impact of Gas Cooling on Ingot Solidification Shrinkage in Vacuum Arc Remelting (VAR) Process

An advanced 2D axisymmetric magnetohydrodynamics model, including calculations for electromagnetic, thermal, and flow fields, fully coupled with a thermal stress-strain model, allowing the computation of solid mechanical parameters like stress, strain, and deformation within the ingot of the vacuum arc remelting process is presented. This process encounters challenges due to solidification shrinkage, which causes losing contact between the ingot and the mold, reducing the cooling efficiency of the system, resulting in a deeper melt pool and decreasing ingot quality. Herein, the width of the air gap along the ingot, the precise position of contact between the ingot and mold, and the profile of the melt pool, affected by gas cooling, are calculated. The global pattern of transport phenomena, such as (electro-vortex) flow and electromagnetic fields in the bulk of the ingot, is insensitive to helium gas cooling through the shrinkage gap. However, including gas cooling significantly improves heat removal through the mold, which consequently reduces the pool depth of the Alloy 718 ingot, leading to an improvement in the quality of the ingot.