More Like this

1. CHARACTERIZATION OF VACUUM ARC REMELTING WITH A HIGH-DENSITY MAGNETIC SENSOR ARRAY

   Cibula, Matthew; McCulley, Daniel; Pettinger, Nathan; Motley, Josh; and King, Paul (September 2022, Proceedings of the Liquid Metals Processing & Casting Conference 2022)

   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
2. 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 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
3. 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 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
4. 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 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. 

   more » « less
5. Effects of Controllable Transverse Magnetic Fields During the VAR Melt Process

   Motley, Joshua; Henjum, John; Cibula, Matt; McCulley, Daniel; Pettinger, Nathan; Alanko, Gordon; and King, Paul (September 2022, LMPC 2022 - Proceedings of the Liquid Metals Processing & Casting Conference 2022)

   Krane, Matthew; Kharicha, Abdellah; and Ward, Mark (Ed.)

   This work describes the utilization of applied transverse magnetic fields to influence the arc dynamics during laboratory and industrial VAR melting. The arc motion was monitored with VARmetricTM as an external sensing platform to inform the system on the resultant direction and magnitude of the arcs due to the applied transverse magnetic field. Electromagnetic coils were mounted outside of the VAR in order to produce the near-uniform transverse magnetic field inside the furnace. These fields interact with the arc in a precise and measurable way, providing a control mechanism for arc motions and distributions. Results are provided for conditions where the applied fields were chosen such that the resultant force forces the arcs into non-ideal distributions, replicating potential deleterious operating conditions that could lead to defects. Results at both laboratory and industrial scale are provided and, wherever possible, ingots were sectioned, and the resulting grain structures were analyzed for defects. 

   more » « less