A Parametric Study of the Vacuum Arc Remelting (VAR) Process: Effects of Arc Radius, Side-Arcing, and Gas Cooling

E Karimi-Sibaki,J Bohacek,A Ludwig,A Kharicha,M Wu

doi:10.1007/s11663-019-01719-5

E Karimi-Sibaki, J Bohacek + Show 3 more

Open Access

https://doi.org/10.1007/s11663-019-01719-5

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Abstract

Main modeling challenges for vacuum arc remelting (VAR) are briefly highlighted concerning various involving phenomena during the process such as formation and movement of cathode spots on the surface of electrode, the vacuum plasma, side-arcing, the thermal radiation in the vacuum region, magnetohydrodynamics (MHD) in the molten pool, melting of the electrode, and solidification of the ingot. A numerical model is proposed to investigate the influence of several decisive parameters such as arc mode (diffusive or constricted), amount of side-arcing, and gas cooling of shrinkage gap at mold–ingot interface on the solidification behavior of a Titanium-based (Ti-6Al-4V) VAR ingot. The electromagnetic and thermal fields are solved in the entire system including the electrode, vacuum plasma, ingot, and mold. The flow field in the molten pool and the solidification pool profile are computed. The depth of molten pool decreases as the radius of arc increases. With the decreasing amount of side-arcing, the depth of the molten pool increases. Furthermore, gas cooling fairly improves the internal quality of ingot (shallow pool depth) without affecting hydrodynamics in the molten pool. Modeling results are validated against an experiment.

Highlights

THE vacuum arc remelting (VAR) process is extensively used to purify numerous alloys such as stainless steel, Nickel-based, and Titanium-based alloys
The distribution of arc in the vacuum plasma region is dependent on the arc radius and the amount of side-arcing
Those parameters are chosen within the reported values

Summary

Introduction

THE vacuum arc remelting (VAR) process is extensively used to purify numerous alloys such as stainless steel, Nickel-based, and Titanium-based alloys. It is a method of refining an impure alloy (electrode in VAR) through vacuum as heated by a DC arc. The tip of the electrode melts resulting in the formation of droplets. Droplets drip through the vacuum and reach the molten pool. Droplets carry low-density oxide inclusions to the molten pool. Inclusions are transferred to the solidification rim (more precisely the surface of ingot) near the mold.

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