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Magnetic measurements coupled with traditional VAR process measurements have enabled the characterization of the spatial distribution of electrical current through the furnace; a process variable that today’s VAR furnaces do not measure. This work presents data acquired by VARmetric, a high density magnetic sensor array, on an industrial VAR furnace processing Fe and Ni- based alloys. VARmetric is used to identify events which would go undetected through traditional process signal analysis, and importantly, can be used to distinguish between distinct arc modes, e.g. diffuse arcs, constricted arcs, and glows. This information facilitates a new method to assess the quality of an ingot in terms of the probability of segregation defects along the ingot axis. 

Magnetic measurements coupled with traditional VAR process measurements have enabled the characterization of the spatial distribution of electrical current through the furnace; a process variable that today’s VAR furnaces do not measure. This work presents data acquired by VARmetric, a high density magnetic sensor array, on an industrial VAR furnace processing Fe- and Ni- based alloys. VARmetric is used to identify events which would go undetected through traditional process signal analysis, and importantly, can be used to distinguish between distinct arc modes, e.g. diffuse arcs, constricted arcs, and glows. This information facilitates a new method to assess the quality of an ingot in terms of the probability of segregation defects along the ingot axis. 

Ampere Scientific’s VARmetricTM measurement system for Vacuum Arc Remelting (VAR) furnaces passively monitors the distribution of arcs over time during VAR in real time. The arc behavior is known to impact both product yield and quality and can pose potentially catastrophic operating conditions. Arc position sensing with VARmetricTM enables a new approach to control the heat input to the melt pool. Transverse external magnetic fields were applied to push the arcs via the Lorentz force while measuring the arc location to control the arc distribution over time. This has been tested on Ampere Scientific’s small-scale laboratory arc furnace with electromagnets used for control for up to 60 seconds while monitoring the arc location with VARmetricTM. The arc distributions were shown to be significantly different from the uncontrolled distributions with distinct thermal profiles at the melt pool. Alternatively, this type of control can be periodically applied to react to undesirable arc conditions.