The behavior of vacuum arcs during VAR processing is known to impact product yield and contribute to ingot defects. Ampere Scientific’s VARmetricTM system has demonstrated non-invasive detection of the spatio-temporal properties of vacuum arcs, including the detection of side-arcing conditions, by utilizing measurements of the magnetic field external to the furnace.
Here we present an analysis of spatio-temporal arc distributions measured by VARmetricTM on a production VAR furnace. Analysis of the arc over different timescales provides new insights into the operating characteristics of VAR furnaces, and on how power is transferred to the molten pool. For example, even under similar steady state operating conditions within a given melt, we have identified significantly different arc distributions, information that may be useful in further understanding the characteristics of the molten metal pool.
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MEASUREMENT OF THE SPATIO-TEMPORAL DISTRIBUTION OF ARCS DURING VACUUM ARC REMELTING AND THEIR IMPLICATIONS ON VAR SOLIDIFCATION DEFECTS
The behavior of vacuum arcs during VAR processing is known to impact product yield and contribute to ingot defects. For example, it has been shown that constricted arcs during the processing of segregation prone nickel-based alloys can lead to defects in ingots. Despite this knowledge, the role of arc distributions in VAR processing has not been considered in controlling the furnaces. In addition, computational models of the process have typically assumed that the arc provides an axisymmetric, Gaussian heat input to the ingot, while acknowledging that this is the biggest unknown variable. Here we present the theory behind VARmetricTM and present analyses of the spatio-temporal arc distributions measured on a production VAR furnace. We then use the measured axisymmetric arc distributions to provide updated boundary conditions for solidification of the ingot to investigate the implications of the changing distributions on solidification and the relationship between arc distributions and defects.
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- Award ID(s):
- 1831255
- NSF-PAR ID:
- 10120903
- Date Published:
- Journal Name:
- Proceedings of the Liquid Metals Processing & Casting Conference
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The behavior of vacuum arcs during VAR processing is known to impact product yield and contribute to ingot defects. Ampere Scientific’s VARmetricTM system has demonstrated non-invasive detection of the spatio-temporal properties of vacuum arcs, including the detection of side-arcing conditions, by utilizing measurements of the magnetic field external to the furnace. Here we present an analysis of spatio-temporal arc distributions measured by VARmetricTM on a production VAR furnace. Analysis of the arc over different timescales provides new insights into the operating characteristics of VAR furnaces, and on how power is transferred to the molten pool. For example, even under similar steady state operating conditions within a given melt, we have identified significantly different arc distributions, information that may be useful in further understanding the characteristics of the molten metal pool.more » « less
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Krane, Matthew ; Kharicha, Abdellay ; and Ward, Mark (Ed.)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.more » « less
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Krane, Matthew ; Kharicha, Abdellah ; and Ward, Mark (Ed.)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.more » « less
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Peng, Zhiwei ; Hwang, Jiann-Yang ; Downey, Jerome P. ; Gregurek, Dean ; Zhao, Baojin ; Yucel, Onuralp ; Keskinkilic, Ender ; Jiang, Tao ; Mahmoud, Morsi Mohamed (Ed.)Ampere Scientific has previously developed and provided industrial validation of the VARmetricTM measurement system to measure the location of electric arcs during vacuum arc remelting (VAR) of high temperature specialty alloys. With the advent of VARmetricTM, it is nowpossible to continuously monitor and control arc distributions in order to tailor the heat flux that drives solidification during the VAR process. Laboratory experiments have applied transverse magnetic fields to generate specified Lorentz forces as a control mechanism across the arc gap in order to drive arc locations to predetermined distributions. This type of control makes it possible to react to undesirable arc conditions during VAR operations or to provide a continuous control to specify a thermal profile for heat input to the melt pool necessary for ensuring defect-free ingots.more » « less
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Accepted Manuscript1.0
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