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1. Feedback-Based Control Over the Spatio-Temporal Distribution of Arcs During Vacuum Arc Remelting via Externally Applied Magnetic Fields

   https://doi.org/10.1007/s11663-020-01959-w  

   Cibula, Matt ; King, Paul ; Motley, Josh ( September 2020 , Metallurgical and Materials Transactions B)

   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 electromagnetsmore »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.« less
2. Control of the Distribution of Vacuum Arcs Within Vacuum Arc Remelting with Externally Applied Magnetic Fields

   https://doi.org/10.1007/978-3-030-36540-0_25  

   King, Paul E. ; Cibula, Matthew ; Motley, Joshua ( April 2020 , The minerals metals materials series)

   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 undesirablemore »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.« less
3. Investigation into the spatio-temporal properties of arcs in vacuum arc remelting furnaces

   Cibula, M. ( September 2017 , Proceedings of the Liquid Metals Processing & Casting Conference)

   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 similarmore »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.« less
4. Investigation into the spatio-temporal properties in arcs in vacuum arc remelting furnaces

   Cibula, M. ( September 2017 , Proceedings of the Liquid Metals Processing & Casting Conference)

   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 similarmore »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.« less
5. MEASUREMENT OF THE SPATIO-TEMPORAL DISTRIBUTION OF ARCS DURING VACUUM ARC REMELTING AND THEIR IMPLICATIONS ON VAR SOLIDIFCATION DEFECTS

   Joshua Motley, Kanchan Kelkar ( January 2019 , Proceedings of the Liquid Metals Processing & Casting Conference)

   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 andmore »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.« less