Process measurement and control and material characterization in remelting furnaces

Abstract

The magnetic field components measured around and along the remelt furnace and other measured furnace parameters are used to estimate the concentricity of the electrodes in the furnace crucible, to estimate the distribution of drip shorts across the gap between the electrodes and the molten pool, or to detect, locate, and categorize anomalous events during the remelt process. They may be used to control the operation of the furnace during the remelt process or incorporated into the resulting longitudinal or three-dimensional map of the ingot. Artificial intelligence, machine learning, or neural networks may be employed.

Description

[Technical field]

[0001] Priority claim This application claims priority to (i) U.S. Provisional Application No. 63 / 326,799, filed April 1, 2022, in the name of Cibula et al., and entitled "Process measurement and control and material characterization in a remelting furnace," (ii) U.S. Provisional Application No. 63 / 409,203, filed September 22, 2022, in the name of Cibula et al., and entitled "Characterization of vacuum arc remelting with a high-density magnetic field sensor array," and (iii) U.S. Nonprovisional Application No. 18 / 129,816, filed March 31, 2023, in the name of Cibula et al., and entitled "Process measurement and control and material characterization in a remelting furnace," all three of which are incorporated by reference in their entireties herein.

[0002] The field of the invention relates to remelting furnaces. In particular, an apparatus and method for process measurement and control and material characterization in a remelting furnace is described herein. [Brief description of the drawings]

[0003] [Figure 1] FIG. 1 is a schematic perspective view of an exemplary configuration of a magnetic sensor coupled to a computer system. [Diagram 2] FIG. 2 is a schematic longitudinal cross-sectional view of an exemplary configuration of a remelting furnace with a magnetic sensor. [Diagram 3] FIG. 3 is a schematic longitudinal cross-sectional view of an exemplary configuration of a remelting furnace with a magnetic sensor. [Figure 4]4A, 4B, and 4C are schematic isometric, top, and side views of an exemplary configuration of a magnetic sensor and a magnetic source coupled to a computer system. [Diagram 5] FIG. 5 is a schematic longitudinal cross-sectional view of an exemplary configuration of a remelting furnace with a magnetic sensor and a magnetic source. [Figure 6] FIG. 6 is a schematic side view of an exemplary configuration of a magnetic sensor and a magnetic source. [Figure 7] 7A and 7B are schematic side views of an exemplary configuration of a fixed magnetic sensor and a moveable magnetic source. [Figure 8] 8A and 8B are schematic side views of an exemplary configuration of a moveable magnetic sensor and a moveable magnetic source. [Figure 9] FIG. 9 is a schematic side view of an exemplary configuration of a magnetic sensor and a magnetic source. [Figure 10] FIG. 10 is a schematic side view of an exemplary configuration of a movable magnetic sensor. [Figure 11] 11A and 11B are schematic longitudinal cross-sectional views of an exemplary configuration of a remelting furnace with a movable magnetic sensor before (FIG. 11A) and after (FIG. 11B) during the remelting process. [Figure 12] 12A and 12B are schematic longitudinal cross-sectional views of an exemplary configuration of a remelting furnace with a movable magnetic sensor before (FIG. 12A) and after (FIG. 12B) during the remelting process. [Figure 13] 13A and 13B are schematic longitudinal cross-sectional views of an exemplary configuration of a remelting furnace with fixed and movable magnetic sensors before (FIG. 13A) and after (FIG. 13B) during the remelting process. [Figure 14] 14A and 14B are schematic longitudinal cross-sectional views of an exemplary configuration of a remelting furnace with a movable magnetic sensor and a movable magnetic source before (FIG. 14A) and after (FIG. 14B) during the remelting process. [Figure 15]15A and 15B are schematic longitudinal cross-sectional views of an exemplary configuration of a remelting furnace with an actuator and a movable magnetic sensor before (FIG. 15A) and after (FIG. 15B) during the remelting process. [Figure 16] 16A and 16B are schematic longitudinal cross-sectional views of an exemplary configuration of a remelting furnace with an actuator, a movable magnetic sensor, and a movable magnetic source before (FIG. 16A) and after (FIG. 16B) during the remelting process. [Figure 17] 17A and 17B are schematic longitudinal cross-sectional views of an exemplary configuration of a remelting furnace with an actuator and a movable magnetic sensor before (FIG. 17A) and after (FIG. 17B) during the remelting process. [Figure 18] 18A and 18B are schematic longitudinal cross-sectional views of an exemplary configuration of a remelting furnace with an actuator, a movable magnetic sensor, and a movable magnetic source before (FIG. 18A) and after (FIG. 18B) during the remelting process. [Figure 19] FIG. 19 is a diagram containing plots of simulated longitudinal magnetic field components as a function of longitudinal position along the furnace, calculated using different transverse positions of the electrodes in the furnace and the current segment in the gap. [Figure 20] FIG. 20 contains plots of measured magnetic field components as a function of transverse position of the electrodes within the furnace. [Figure 21] FIG. 21 contains plots of measured current, voltage, and magnetic field components during transverse movement of an electrode within a furnace. [Figure 22] FIG. 22 shows the measured drip short distribution for two different remelt processes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0004] The illustrated embodiments are shown only diagrammatically, all features may not be shown in complete detail or to proper proportion, some features or structures may be exaggerated or reduced relative to others or omitted entirely for clarity, and the drawings should not be considered to be to scale unless expressly indicated to be to scale. The illustrated embodiments are examples only and should not be construed as limiting the scope of the present disclosure or the appended claims, which are subsequently presented.

[0005] The following detailed description should be read with reference to the drawings, in which like reference numerals refer to like elements throughout the different views. The drawings, which are not necessarily to scale, illustrate selected examples and are not intended to limit the scope of the invention. The detailed description illustrates the principles of the invention by way of example, and not by way of limitation.

[0006] The subject matter disclosed herein may be related to subject matter disclosed in one or more of: (i) U.S. Patent No. 8,111,059; (ii) U.S. Patent No. 10,514,413; (iii) U.S. Patent No. 10,761,116; (iv) U.S. Patent No. 11,022,656; (v) U.S. Patent No. 11,236,404; (vi) U.S. Patent No. 11,243,273; (vii) U.S. Patent No. 11,459,627; or (viii) U.S. Patent Application Publication No. 2022 / 0154300, all of which are incorporated by reference in their entirety herein.

[0007] The above-listed references disclose apparatus and methods for estimating and / or controlling the position and / or length of an electric discharge or arc, or other transversely localized electric current segment 30, flowing longitudinally across the gap 115 between two conductive bodies 110 and 120 (as in the various examples shown diagrammatically in Figs. 1-17B). A number of magnetic field sensors 201 (fixed) and / or 202 (movable) are employed to measure magnetic field components resulting from the current segment 30, and a computer system 299 is used to calculate an estimated position based on those measured field components and the corresponding locations at which they were measured. A magnetic field source 300 may be employed to induce transverse movement of the current segment 30, and the magnetic field source 300 and the magnetic field sensors 201 / 202 may be coupled in a feedback configuration or as a servo mechanism to apply a control magnetic field based on the estimated location of the current segment 30. A longitudinal mechanical actuator 130 of any suitable type or configuration (e.g., hydraulic, gear driven, servo motor, etc.) may be employed to control the distance between conductive body 110 and conductive body 120 and therefore the length of current segment 30, and the longitudinal actuator 130 and magnetic field sensor 201 / 202 may be coupled in a feedback configuration or as a servo mechanism to move one or both conductive bodies 110 / 120 based on the estimated length of current segment 30.

[0008] Such apparatus and methods may be usefully employed in a variety of settings. One important setting is in the field of remelting furnaces 100, in which an electric current flows through a conductive metal electrode 110 to be melted, through an ingot 120 formed from molten metal from the electrode 110 dripping into a melt pool 122 on its upper surface, and through one or more localized current segments 30 that span a gap 115 between the electrode 110 and the ingot 120. In some furnaces 100 (e.g., vacuum arc remelting furnaces, also called VAR furnaces), the current segment 30 is an electric discharge or arc, and the gap 115 is a vacuum or at most a diffuse plasma generated by the discharge or arc. In other furnaces 100, a gaseous medium occupies the gap 115 between the electrode 110 and the ingot 120. In still other furnaces 100 (e.g., electroslag remelting furnaces, also called ESR furnaces), molten slag (not shown) occupies the gap 115 between the electrode 110 and the ingot 120. In any of those examples, the localized current segments 30 may also include transient short circuits (called drip shorts) through droplets of molten metal dripping across the gap 115 between the melting electrode 110 and the growing ingot 120. The location or distribution of any or all types of localized current segments 30, as well as other measured or observed behaviors or parameters during the remelting process, may be strongly correlated with the quality of the metal in the ingot 120 resulting from the remelting process. Thus, the methods and apparatus disclosed herein and in the incorporated references may be advantageously employed, for example, to alter, maintain, or otherwise control the remelting process, to assess the quality of the metal in the ingot 120 resulting from the remelting process, to guide subsequent use, handling, or processing of the metal of the ingot 120, or for other purposes.

[0009] A typical configuration of stationary magnetic field sensors 201 is shown in FIG. 1. The sensors 201 are configured around the periphery of a current-containing volume 10 (e.g., the interior volume of the remelting furnace 100) through which current flows generally in a longitudinal direction. The sensors 201 measure magnetic field components in two transverse dimensions in some examples, or (more generally) in all three spatial dimensions in other examples. The sensors 201 are disposed at corresponding sensor locations at a number of different longitudinal positions along the volume 10 and / or at a number of different circumferential positions around the volume 10. In the example of FIG. 1, the sensors 201 are configured as three rings of sensors 201 at three different longitudinal positions along the volume 10, as well as additional sensors 201 at other longitudinal positions, although other suitable sensor configurations may be employed. The sensors 201 are coupled to a computer system 299, which receives electronic signals from the sensors 201 indicative of the measured magnetic field components. Based on one or some or all of the measured magnetic field components, the corresponding positions of the sensor 201, and the corresponding calibration coefficients for the sensor 201, the computer system 299 can calculate an estimated transverse position or estimated transverse distribution of the current flowing through the volume 10. The distribution can take the form of one or more localized current segments 30 in the gap 115 (e.g., electrical discharges or drip shorts in a VAR furnace), or a less localized current distribution in the electrode 110 and ingot 120. The computer system 299 can also calculate an estimated longitudinal position of one or more localized current segments 30 in the volume 10, which correspond to the longitudinal location in the volume 10 of the gap 115 between the electrode 110 and the ingot 120 (moving upward through the crucible 101 during the remelting process).These calculations may be performed in any suitable manner (e.g., analytically, numerically, approximately, etc.) based on Maxwell's equations or any suitable subset or adaptation thereof (e.g., Biot-Savart's law or Jefimenko's equation). It should be noted that "one or more measured magnetic field components," "two or more measured magnetic field components," "multiple measured magnetic field components," "a portion of the measured magnetic field components," "all of the measured magnetic field components," etc. can refer to components in multiple different directions all measured at a single corresponding sensor location, components all in a single direction measured at multiple corresponding sensor locations, or components in multiple different directions measured at multiple different corresponding sensor locations.

[0010] 2 and 3 show an example of a remelting furnace 100, including a crucible 101, an outer wall 102, and a water-cooled cooling jacket 103 therebetween. A sensor 201 is configured around the furnace 100 on the outside of the outer wall 102. A metal electrode 110 in an upper portion of the furnace 100 and a metal ingot 120 in the crucible 101 in a lower portion of the furnace are separated by a gap 115. A current 20 flows through the electrode 110, across the gap 115 (e.g., as an arc or discharge 30 in a VAR furnace, or other localized current segment(s) 30), through the ingot 120, and through the crucible 101 and the upper portion of the furnace 100; alternatively, in these and subsequent examples, the current can instead flow through the crucible 101 in the lower portion of the furnace 100. In some cases, a portion of the current may flow directly between the electrode 110 and the crucible 101 as a so-called side arc 32 (e.g., as in FIG. 3), which is undesirable as it may lead to damage to the furnace 100 or introduce impurities or contaminants into the ingot 120. Heat generated by the current 20 in the gap 115 during the remelting process causes the electrode 110 to melt and shrink and the ingot 120 to grow as molten metal drips from the electrode 110 into a molten pool 122 at the top of the ingot 120. The gap 115 moves upward through the furnace 100 during the remelting process as the ingot 120 grows. Because the electrode 100 has a smaller diameter than that of the ingot 120, the electrode 110 is lowered into the furnace 100 during the remelting process to maintain a relatively constant distance across the gap 115. A longitudinal actuator for that purpose is present in all examples, but is only explicitly shown in Figures 15A-18B (as actuator 130) and is described further below.

[0011] In some cases, the estimated position of the current segment 30 may be recorded as a function of the longitudinal position of the gap 115, which corresponds to the longitudinal position along the solidified ingot 120 resulting from the remelting process. In some examples, the measured magnetic field components may indicate the presence of a side arc 32 and possibly also the transverse location of the side arc 32 (e.g., position along the circumference of the furnace). The side arc information may be recorded as a function of the longitudinal position of the gap 115 in the furnace 100, i.e., longitudinal position along the ingot 120, and in some cases, as a function of circumferential position around the furnace 100, i.e., circumferential position around the ingot 120.

[0012] Instead of or in addition to passively recording arc position or side arc occurrence as a function of longitudinal position along the ingot 120, active measures may be taken during the remelting process in response to measured magnetic field components. In some instances, detection of a side arc 32, or the persistence of a side arc 32 longer than a selected time limit, or the occurrence of multiple side arcs 32 above a selected threshold number or within a selected time window, may cause the computer system 299 to, for example, change or interrupt the current 20, change the voltage, or move or retract the electrode 110. In some instances, the interruption or change may be temporary, after which the remelting process may continue as before, in some instances the change may be sustained while the remelting process may continue, and in some instances the remelting process may be halted entirely.

[0013] In some examples, a magnetic field source 300 may be positioned around the arc furnace 100 and configured to allow for alteration, maintenance, or control of the transverse position of the current segment 30 within the gap 115. A typical configuration of the source 300 and sensor 201 is shown diagrammatically in FIGS. 4A-4C, where a pair of conductive coils 300x is configured to apply a magnetic field along the x-direction and a second pair of coils 300y is configured to apply a magnetic field along the y-direction. Both the source 300 (i.e., coils 300x / 300y) and the sensor 201 are operably coupled to a computer system 299. The computer system 299 may be configured and programmed to cause a current to flow through coils 300x and / or 300y in response to the magnetic field measured by the source 201 (i.e., in response to an estimated position of the current 20 flowing through the current-containing volume 10). The source 300 and the sensors 201 and / or 202 may be coupled to each other by the computer system 299 in a feedback arrangement or as a servo mechanism, such that a magnetic field is applied by the source 300 to change, maintain, or control the position of the current 20 in response to the magnetic field measured by the sensors 201 / 202. In some examples, the magnetic field may be applied by the source 300 to produce a desired transverse trajectory or transverse distribution of the current 20. Figures 5-9 show various exemplary configurations of the source 300 and the sensor 201 on the remelt furnace 100 (including the moving source 300 in Figures 7A / 7B and 8A / 8B, the moving sensor 202 in Figures 8A / 8B).

[0014] In the example described above, the longitudinal actuator moves the electrode 110 downward as it melts away to maintain a relatively constant distance across the gap 115 (because the diameter of the electrode 110 is smaller than the diameter of the crucible 101 and ingot 120, the electrode 110 shrinks faster than the ingot 120 grows during the remelting process). In some examples, that may be approximately accomplished, for example, by monitoring the weight of the electrode 110 (which decreases as the electrode 110 melts), by monitoring the voltage drop across the gap 115, or by monitoring the rate of drip shorts, each of which measured quantities are at least loosely correlated with the distance across the gap 115 and the length of the current segment 30 spanning the gap 115.

[0015] FIG. 10 shows a schematic of a typical configuration of movable magnetic field sensors 202 that move longitudinally along the current-containing volume 10. FIGS. 11A-16B show various examples of remelting furnaces 100 with movable sensors 202. The movable sensors 202 are generally spaced closer together than the fixed sensors 201. Actuators of any suitable type or configuration (e.g., hydraulic, gear-driven, servo motors, etc.) are configured to move the sensors 202 and coupled to the computer system 299, such that the sensors 202 can generally be moved in response to magnetic field components measured by those sensors 202 to keep the sensors 202 near the gap 115 as they move along the volume 10, and a feedback configuration or servo mechanism coupling the sensor actuators and the sensors 202 can be implemented by the computer system 299 for that purpose. The computer system 299 may be configured and programmed to calculate an estimated length parameter characterizing the current segment 30 (and thus also characterizing the separation between the conductors 110 and 120 across the gap 115), the calculation being based at least in part on the magnetic field components measured by the sensors 201 and / or 202. In some examples, the length parameter may be recorded as a function of the longitudinal position of the gap 115 (equivalently, the longitudinal position along the ingot 120). In some examples, the sensor 202 may be operatively coupled to the longitudinal actuator 130 through the computer system 299, and in some of those examples, a feedback arrangement or servo mechanism may be employed to maintain the length parameter at a selected value or within a selected range of values. If the furnace 100 also includes a magnetic field source 300, in some examples, the source 300 and the sensor 202 (and in some cases 201) may be used in conjunction to map in detail the topography of the gap 115.Instead of or in addition to a set of sensors 202 that are longitudinally movable along the current-containing volume 10, in some examples a set of magnetic field sensors 201 may be positioned at fixed locations along the current-containing volume 10 with relatively dense longitudinal spacing (e.g., the longitudinal spacing may be similar to that of the movable sensors 202, as in FIGS. 1, 2, 3, and 5). Corresponding magnetic field measurements from those densely spaced sensors 201 may be used to estimate the longitudinal position of the gap 115 and to estimate the length parameter(s) of one or more current segments 30.

[0016] As explained in the above-incorporated references, the above-described systems, apparatus, and methods may be advantageously employed for process measurement and control and material characterization in a remelting furnace, e.g., a VAR furnace or an ESR furnace. Other novel and inventive methods for such process measurement and control and material characterization are disclosed below.

[0017] It is known that solidification defects in the ingot 120 can be caused by, indicated by, and / or correlated with transient conditions due to (i) spatial or temporal variations in the heating or cooling of the molten pool 122 at the top of the ingot 120, (ii) spatial or temporal variations in the flow of electrical current in the electrode 110, between the electrode 110 and the ingot 120, in the ingot 120, or between the ingot 120 and the crucible 101, or (iii) undesirable electrical currents between the electrode 110 and the crucible 101 (e.g., side arcs). Variations that are not cylindrically symmetric and / or not centered with respect to the crucible 101 and the ingot 120 solidifying therein can be particularly problematic. In a VAR furnace, most of the heat deposited in the molten pool 122 is due to the electric arc or discharge (i.e., current segment 30) between the electrode 110 and the ingot 120, and to molten metal dripping from the electrode 110 into the molten pool 122. The transverse distribution of the molten metal drips tends to reflect the transverse spatial distribution of the electric discharge(s) (discussed further below). In an ESR furnace, most of the heat deposited in the molten pool 122 is due to resistive heating of the slag filling the gap 115, and to molten metal flowing through the slag from the electrode 110 into the molten pool 122. Most of the heat flowing from within the molten pool 122 as it solidifies flows radially outward into the crucible 101 near the top of the growing ingot 120, relying on contact between the ingot 120 and the crucible 101.

[0018] A non-concentric geometry of the electrode 110 within the crucible 101 may distort the distribution of the discharge 30 between the electrode 110 and the molten pool 122, and / or metal drips, and / or other localized current segment(s) across the gap 115, or may distort the distribution of heat accumulated in the ingot 120 via the molten pool 122. Such non-concentric geometries may include off-center positioning of the electrode 110 within the crucible 101, tilting of the electrode relative to the crucible 101, a bent or curved shape of the electrode 110, cracks, cavities, inclusions, or other structural irregularities in the electrode 110, or various combinations of any or all of these. As mentioned above, the transverse size of the electrode 110 is necessarily smaller than the transverse size of the interior of the crucible 101. If the lower end of the electrode 110 (at the gap 115) is off-center with respect to the crucible 101 (and therefore with respect to the ingot 120), the distribution of electrical discharge and molten metal drip across the gap 115, or heat flow into the ingot 120, may also be off-center. One result may be asymmetric erosion of the lower end of the melting electrode 110, leading to an undesirable convex, concave, or sloping lower surface of the electrode 110. Another result may be non-uniform, non-homogeneous, or asymmetric solidification of the ingot 120, which may lead to defects, inclusions, undesirable grain boundaries, or spatial variations in the relative concentrations of the alloying metals. It may be desirable to measure and estimate one or more of: (i) the transverse position of the electrode 110 and / or the lower end of the electrode 110 within the crucible 101; (ii) the cross-sectional position and shape of the electrode 110 as a function of longitudinal position (along the electrode 110, of the gap 115 along the crucible 101, or both); or (iii) the transverse spatial distribution of the current 20 in the electrode 110 as a function of longitudinal position (along the electrode 110, along the crucible 101, or both).It may be desirable to vary, maintain, or control the estimated transverse position or angle of the electrode 110 within the crucible 101 to achieve or maintain relative concentricity of one or more of: (i) the current 20 flowing through the volume 10; (ii) the transverse distribution of the positions of the current segments 30; or (iii) the transverse distribution of the molten metal dripping from the electrode 110 onto the ingot 120.

[0019] Non-concentric current flow in and between the ingot 120 and the crucible 101 can exhibit irregularities during the remelting process that can result in material defects or inhomogeneities in the solidified ingot 120 (such as those described above). Generally, the molten pool 122 solidifies radially inward from the inner surface of the crucible 101. As the ingot 120 solidifies, it tends to shrink and move away from the crucible, and thus most of the current flow and heat flow between the ingot 120 and the crucible 101 is localized around the molten pool 122 and near the top of the growing ingot 120. Detection of current flow between the ingot 120 and the crucible 101 at a location longitudinally distant from the molten pool 122, particularly asymmetric current flow, can indicate too rapid or asymmetric cooling or solidification at that longitudinal location, possibly indicating degraded material quality in the ingot 120 at that location. Detection of asymmetric current flow near the top of the growing ingot 120 can indicate a disruption of the desired gradual, orderly solidification of the molten pool 122. For example, a so-called shelf collapse or fall-in may occur, where a portion of the partially solidified surface of the molten pool 122 breaks off and falls into the molten pool (similar to the calving of an iceberg from a glacier). That portion of the solidified ingot 120 will generally exhibit increased potential for defects (e.g., white spots) or variations in alloy composition, and will almost certainly exhibit a higher density of undesirable grain boundaries. Transient asymmetries in current flow into the crucible 101 at the longitudinal position of the molten pool 122 can indicate such a shelf collapse event and can indicate the transverse or longitudinal position along the solidified ingot 120 where corresponding degraded material quality can be found.

[0020] Thus, the apparatus of the present invention may include a first longitudinal electrical conductor 110 and a second longitudinal electrical conductor 120, a plurality of magnetic field sensors 201 and / or 202, and a computer system 299. The apparatus may be configured as a remelting furnace 100, examples of which are shown diagrammatically in Figs. 1-18B. The first longitudinal electrical conductor may be an electrode 110 and the second longitudinal electrical conductor may be an ingot 120. The electrode 110 and the ingot 120 are positioned end-to-end within a current-containing volume 10 inside the remelting furnace 100. A primary current 20 flows primarily longitudinally (i) through at least a portion of the electrode 110 and the ingot 120, and (ii) as one or more localized current segments 30 (e.g., primary electrical discharges 30 in a VAR) that span a gap 115 separating the electrode 110 and the ingot 120. One or more localized current segments 30 can move in two transverse dimensions within the gap 115. A number of magnetic field sensors 201 (fixed) and / or 202 (movable) are configured to measure magnetic field components in one or more spatial dimensions and are positioned at corresponding sensor locations configured around the lateral periphery of the current-containing volume 10. The sensors 201 / 202 are positioned at a number of different longitudinal positions along the furnace 100 and at a number of different circumferential positions around the furnace 100.

[0021] The computer system 299 receives corresponding signals from the magnetic field sensors 201 and / or 202 indicative of magnetic field components measured at a plurality of sensor locations, including sensor locations longitudinally offset from the arc gap 115. The computer system 299 can calculate an estimated transverse position of one or more current segments 30 within the gap 115 based at least in part on two or more of the measured magnetic field components. In some examples, the two or more magnetic field components measured at corresponding sensor locations longitudinally displaced from the gap 115 toward the electrode 110 (i.e., toward the top of the furnace 100) can be used by the computer system 299 to calculate an estimated relative tilt or transverse offset of the electrode 110 or portions thereof, an estimated overall shape of the electrode 110, or an estimated spatial distribution of the current flowing within the electrode 110, which may be affected by internal cracks, inclusions, or other electrode defects. In some examples, two or more magnetic field components measured at corresponding sensor positions displaced longitudinally from the gap 115 toward the ingot 120 (i.e., toward the bottom of the furnace 100) may be used by the computer system 299 to calculate an estimated spatial distribution of current within and / or between the ingot 120 and the crucible 101.

[0022] FIG. 19 includes plots of simulated longitudinal magnetic field components as a function of longitudinal position along the furnace 100, calculated using different transverse positions of the right cylindrical electrode 110 within the crucible and different transverse positions of the current segment 30 within the arc gap 115. Curve 1 is for the case where both the electrode 110 and the current segment 30 are centered within the crucible 101, and as expected, the calculated magnitude of the longitudinal magnetic field is zero throughout the furnace 100. Curves 2-4 are for 10 mm, 25 mm, and 45 mm transverse displacements of both the electrode 110 and the current segment 30, respectively (i.e., the current segment 30 remains centered on the electrode 110 as the electrode 110 is displaced). Curves 5-8 are for 0 mm, 10 mm, 25 mm, and 45 mm transverse displacements of electrode 110, respectively, where the current segment is displaced an additional 200 mm in the same direction (i.e., off-center relative to electrode 110 as electrode 110 is displaced). Curves 9-11 are for 10 mm, 25 mm, and 45 mm transverse displacements of the electrode, respectively, where the current segment 30 remains centered within crucible 101.

[0023] As can be seen from the plot in FIG. 19, the longitudinal magnetic field magnitude near the gap 115 is significantly affected by the position of the current segment 30. The current segments furthest from the center of the crucible (curves 5-8) exhibit a pronounced peak in the region of the gap 115. In contrast, at positions sufficiently longitudinally displaced from the gap 115 (e.g., to the right of −1.5 m in FIG. 19), the longitudinal magnetic field magnitude is almost entirely dependent on the transverse offset of the electrode 110. Curves representing the same displacement of the electrode 110 but different displacements of the current segment 30 converge to a common value. For a centered electrode, curves 1 and 5 converge to a longitudinal magnetic field magnitude of essentially zero to the right of −1 m in FIG. 19. For an electrode 110 displaced 10 mm from the center, curves 2, 6, and 9 converge to approximately 0.5 Gauss to the right of −1.5 m. For an electrode 110 displaced 25 mm from the center, curves 3, 7, and 10 converge to about 1.2 Gauss to the right of -1.5 m. For an electrode 110 displaced 45 mm from the center, curves 4, 8, and 11 converge to about 2.2 Gauss to the right of -1.5 m.

[0024] A plot of the magnetic field measured in the VAR furnace is shown in Figure 20. It can be seen that the change in magnetic field strength between 4100 seconds and 4300 seconds results from the deliberate movement of the electrode 110 towards one side of the crucible 101 and back again.

[0025] The magnetic field components measured by some or all of the magnetic field sensors 201 and / or 202 may be recorded as a function of the moving longitudinal position of the gap 115 during the remelting process in the furnace 100. The longitudinal position of the gap 115 may be correlated with a corresponding longitudinal position along the solidified ingot 120 after the remelting process is completed, and thus may serve as an indication of the relative material quality of different portions of the ingot 120. In some examples, an estimated transverse distribution of the positions within the gap 115 of the current segments 30 (e.g., arcs or discharges), or of molten metal drops (described below), calculated from the measured magnetic field components, may be recorded as a function of longitudinal position along the solidified ingot 120 (as described herein and in some of the incorporated references). In some examples, the estimated presence or absence of current flowing between the electrode 110 and the crucible 101 (e.g., one or more side arcs) may be recorded as a function of longitudinal position along the solidified ingot 120 (as described above and in some of the incorporated references), and the circumferential position of such side arcs may be recorded as well. In some examples, the presence or absence of undesirable operating behavior or conditions (e.g., a long arc, a constricted arc, or a glow) may be inferred or estimated from the measured magnetic field components and recorded as a function of longitudinal position along the solidified ingot 120. In some examples, the transverse distribution of current flowing in the electrode 110 may be recorded as a function of longitudinal position along the solidified ingot 120, and in some cases may be recorded as a function of longitudinal position within the crucible 101 or along the electrode 110. These recorded measurements can be employed, for example, to correlate a given longitudinal position along the solidified ingot 120 with, for example, a corresponding transverse position of an end of the electrode 110, or the melting of a cracked, damaged, or otherwise irregular portion of the electrode 110.In some examples, the transverse or circumferential distribution of electrical current flowing in and / or between the ingot 120 and the crucible 101 may be recorded as a function of longitudinal position along the solidified ingot 120, and in some cases as a function of longitudinal position within the crucible 101. These recorded measurements may be employed, for example, to correlate a given longitudinal position along the solidified ingot 120 with, for example, a corresponding shelf collapse event in the molten pool 122, or a portion of the ingot 120 that remained in electrical contact with the crucible after solidification.

[0026] In addition to recording the measured magnetic field components (and estimated quantities calculated therefrom), those measured magnetic field components or calculated quantities may be employed to induce or control active measures taken to maintain, alter, or control the remelting process. In some examples, magnetic field source 300 may be employed to apply a magnetic field to the interior of remelting furnace 100, generally in or near the region of gap 115, to maintain, alter, or control the transverse position of current segment 30 within gap 115 (as described above and in some of the incorporated references). The strength and direction of those applied magnetic fields may be determined based at least in part on the measured magnetic field components or quantities calculated therefrom, and in some of those examples, magnetic field sensors 201 and / or 202 may be coupled to magnetic field source 300 by computer system 299 in a feedback configuration or as a servo mechanism. In some examples, detection or estimation of the presence of one or more undesirable conditions (e.g., a side arc, a long arc, a built up arc, or a glow) in the furnace 100 can cause the computer system 299 to activate one or more magnetic field sources 300 to modify or terminate the undesirable condition.

[0027] In some examples, the remelt furnace 100 can include corresponding additional sensors coupled to or positioned on or in the furnace 100 that can measure (i) the longitudinal or transverse position or velocity of the electrode 110 or one or more actuators 130 / 140 coupled to the electrode 110, (ii) the weight of the electrode 110, (iii) the magnitude of the operating current or a variation thereof, (iv) the difference between the operating current and the primary current 20, (v) the voltage drop between the electrode 110 and the ingot 120 or a variation thereof, (vi) the electrical resistance across the gap 115 or a variation thereof (e.g., For example, through slag filling gap 115 (sometimes referred to as “swing” or “resistance swing”), (vii) temperature within furnace 100, (viii) one or more temperature gradients within or along electrode 110, ingot 120, or along or around crucible 101, (ix) pressure or composition of gas or vapor within furnace 100, (x) optical spectrum characteristic light emitted by one or more current segments 30 / 32, or (xi) an image of the interior of furnace 100. Signals generated by such additional sensors indicative of the corresponding measured quantities are received by computer system 299. In some examples, furnace operating parameters, such as total current, internal steam pressure (e.g., helium pressure between the crucible 101 and the solidified portion of the ingot 120, or argon backflow pressure), internal steam composition, slag depth or composition (in an ESR furnace), etc., may be maintained, altered, or controlled by the computer system 299 in response to the measured magnetic field components or quantities calculated therefrom. In some examples, detection or estimation of the presence of an undesirable operating condition (e.g., such as those described above) may cause the computer system 299 to alter furnace operating parameters (e.g., such as those described above) to reduce or eliminate the undesirable condition. For example, detection of an undesirable glow or constricting arc may result in alteration of the pressure, flow, or composition of the input gases.In some examples, measured magnetic field components or other furnace operating parameters (e.g., current, voltage, gas pressure or composition, excessive or insufficient movement of electrode 110) that indicate a furnace malfunction or improper setup or operation can cause the computer system 299 to modify or terminate operation of the furnace 100.

[0028] As mentioned above, the remelt furnace 100 includes a longitudinal actuator 130 (shown explicitly only in FIGS. 15A-18B, but included in any of the examples of FIGS. 1-18B) for controlling the vertical position of the electrode 110 within the crucible 101 to maintain the distance across the gap 115 within a desired range during the remelt process. The electrode 110 must move downward as it melts because the ingot 120 grows slower than the electrode 110 shrinks during the remelt process. The longitudinal actuator 130 is connected to a computer system 299, which can control the vertical (i.e., longitudinal) movement of the electrode 110 based on one or more of the weight of the electrode 110, the melting duration, the voltage drop across the gap 115, or one or more measured magnetic field components (from which the distance across the gap 115 can be inferred, as described above and in some of the incorporated references).

[0029] In addition to the longitudinal actuator 130, in some examples, the apparatus can include a transverse actuator 140 of any suitable type or configuration (e.g., hydraulic, gear-driven, servo motor, etc.). The transverse actuator 140 is only explicitly shown in FIGS. 17A-18B, but can be included in any of the examples of FIGS. 1-18B. In some examples, the longitudinal actuator 130 and the transverse actuator 140 can be combined into a single dual-axis unit, while in other examples, they can comprise separate units. The transverse actuator 140 can be configured to provide one or both of (i) relative transverse movement of the electrode 110 within the crucible 101, or (ii) relative tilt of the electrode 110 within the crucible 101. The computer system 299 can generate one or more transverse position control signals and transmit those signals to the transverse actuator 140 to effectuate the transverse movement and / or tilt of the electrode 110. The transverse position control signals may be based at least in part on one or both of an estimated transverse position or estimated transverse distribution of the current segment(s) 30, an estimated relative tilt or transverse offset of the electrode 110 within the crucible 101, or an estimated shape of the electrode 110, which may be calculated based on the measured magnetic field components measured by the sensors 201 and / or 202, as described above. In some examples, the magnetic sensors 201 and / or 202 may be operatively coupled to the transverse actuator 140 in a feedback configuration or as a servo mechanism using the computer system 299.

[0030] In some examples (e.g., as in FIGS. 18A and 18B ), the transverse actuator 140 may be used in combination with other features disclosed above, including, for example, one or more of the fixed and / or moving magnetic field sensors 201 / 202, the longitudinal actuator 130 coupled to a computer system 299 for varying, maintaining, or controlling the distance across the gap 115, or the magnetic field source 300 coupled to a computer system 299 for varying, maintaining, or controlling the transverse position or transverse distribution of the current segment(s) 30 in the gap 115. In various examples, the sensors 201 and / or 202 may be operatively coupled to any one, any two, or all three of the longitudinal actuator 130, the magnetic field source 300, or the transverse actuator 140, or other controllers of the furnace 100. For example, the magnetic field source 300 can be operated to center the distribution of discharge locations within the gap 115 while at the same time the transverse actuator 140 is employed to center the electrode 110 within the crucible 101 .

[0031] The dripping of molten metal from the melting electrode 110 into the molten pool 122 on top of the ingot 120 is described above. In addition to estimating the transverse position or distribution of transverse positions of one or more current segments 30 in the gap 115, it may also be desirable to estimate the distribution of transverse positions of the drips onto the ingot 120.

[0032] Each molten drop may cause a so-called drip short when the dripping metal creates a transient conductive path between the electrode 110 and the ingot 120. The presence of that conductive path causes a transient spike or waveform in the voltage drop across the gap 115 or in the current 20 flowing through the furnace 100. In the inventive method, the magnetic field components may be measured at multiple longitudinal positions along the furnace 100 and / or multiple circumferential positions around the furnace 100. Estimates of the transverse positions or distribution of transverse positions of one or more current segments 30 may be calculated as described above. However, if drip shorts are present, those transverse position estimates will necessarily be affected by the presence of those drip shorts. The computer system 299 may be connected to monitor the voltage drop between the electrode 110 and the ingot 120 and the current flowing through the furnace 100. Detection of a sudden transient decrease in the voltage drop and a sudden transient increase in the current indicates the occurrence of a drip short. It should be noted that transients in the furnace current and voltage may last only a few milliseconds. In some examples, the sampling rate of the magnetic field sensors 201 and / or 202 may be fast enough (e.g., 500 Hz, 1 kHz, or even faster) to capture those transients. In other examples, a lower sampling rate may be employed if the time constant in the detection system is long enough that the transient features are detectable at the lower sampling rate. FIG. 21 shows some examples of measured current, voltage, and magnetic field components during operation of a remelting furnace, where the transient features in the voltage and current traces are clearly discernible, as are the corresponding transient features in the magnetic field traces.

[0033] The computer system can use the measured magnetic field components at the time of the detected voltage and current transients to calculate an estimated transverse position of the current segment 30 (as described above). However, the estimated position calculated in this manner indicates the location of the drip short that caused those voltage and current transients, not an electrical discharge. During the remelting process, for each detected drip short, a corresponding estimated longitudinal position (the longitudinal position of the gap 115 at the time of the drip short) and a corresponding transverse position (calculated from the measured magnetic field components at the time of the drip short) can be recorded for the ingot 120. Two examples are shown in FIG.

[0034] The transverse location of the drip shorts cannot be controlled, but the average distribution of the drip shorts can be altered, maintained, or controlled using the magnetic field source 300 described above. Drip shorts occur where melting occurs on the electrode 110 that is heated by one or more current segments (e.g., discharge 30). Using the magnetic field source 300 to alter, maintain, or control the location or distribution of the current segment(s) 30 (as described above), the transverse spatial distribution of the drip shorts can also be altered, maintained, or controlled (at least on average; the formation of drip shorts is a somewhat random process). The computer system 299 can monitor the occurrence and distribution of drip shorts and can cause the source 300 to apply a magnetic field to (indirectly) alter, maintain, or control the drip short spatial distribution. In some examples, the magnetic field source 300 can be employed to move the discharge(s) 30, or the distribution of the drip shorts, to diffuse the accumulation of heat into the molten pool 122 of the ingot 120. In some examples, the magnetic field source may be operated to move the discharge or drip short distribution(s), for example, in a spiral, circular, or star pattern to achieve that result. In some examples, spreading the heat distribution can result in an ingot 120 with improved "skin quality," i.e., a thinner layer of metal around the circumference of the solidified ingot 120 that must later be removed due to its poor quality.

[0035] The inventive method for measuring the location or distribution of drip shorts may be used in combination with other features disclosed above including, for example, one or more of fixed and / or moving magnetic field sensors 201 / 202, a longitudinal actuator 130 coupled to a computer system 299 for varying, maintaining or controlling the distance across the gap 115, a magnetic field source 300 coupled to a computer system 299 for varying, maintaining or controlling the transverse position or transverse distribution of the current segment(s) 30 within the gap 115, or a transverse actuator 140 coupled to a computer system for varying, maintaining or controlling the transverse position of the electrode 110 within the crucible 101.

[0036] As mentioned above, in some examples, the remelt furnace 100 may include additional sensors for measuring or detecting various properties of the furnace 100 or the remelt process occurring therein. The computer system 299 may receive signals indicative of some or all of the magnetic field components measured using the sensors 201 and / or 202 and / or may receive signals indicative of some or all of the quantities measured by the additional sensors. In some examples, based at least in part on some or all of those received signals, or on quantities or parameters calculated, estimated, or derived therefrom (e.g., transverse or longitudinal positions or distributions of the current segments 30), the computer system 299 may be used to modify, maintain, or control one or more operating parameters of the furnace 100 during the remelt process. In some examples, based at least in part on some or all of those received signals, or on quantities or parameters calculated, estimated, or derived therefrom, the computer system 299 may be used to generate and store a longitudinal or three-dimensional map of the ingot 120 resulting from the remelt process.

[0037] In some examples, altering, maintaining, or controlling one or more operating parameters of the furnace 100 during the remelt process may include (i) stopping the remelt process; (ii) temporarily suspending and then resuming the remelt process; (iii) rejecting or downgrading only the ingot, or selected portions of the ingot; (iv) performing certain post-melt treatments on only the ingot, or certain portions of the ingot; (v) applying a magnetic field to change, maintain, or control the transverse position or transverse distribution of one or more current segments in the gap 115; (vi) applying a magnetic field to change, maintain, or control the transverse distribution of a plurality of drip shorts in the gap 115; (vii) applying a magnetic field to change, maintain, or control the transverse distribution of heat accumulated on the surface of the ingot; (viii) applying a magnetic field to dampen or terminate a side arc, a constricting arc, a glow, or a long arc; (ix) changing, maintaining, or controlling the distance between the electrode and the ingot across the gap 115; (x) applying a magnetic field to the crucible 101 (xi) changing, maintaining, or controlling the angle or transverse position of the electrode 110 within the gap 115; (xii) changing, maintaining, or controlling the current flowing through the electrode 110 and the ingot 120; (xiii) changing, maintaining, or controlling the electrical resistance across the gap 115 (e.g., through the molten slag filling the gap 115, sometimes referred to as a "swing" or "resistance swing"); (xiv) changing, maintaining, or controlling the immersion depth of the electrode 110 into the molten slag filling the gap 115; or (xv) changing, maintaining, or controlling the gas pressure or composition within the furnace 100.

[0038] Measurements of magnetic field components and / or other properties of the furnace 100 or the remelting process occurring therein may be recorded as a function of time during the remelting process, which corresponds to longitudinal position along the ingot 120. In some examples, one or more of the following may be recorded as a function of longitudinal position along the ingot 120 formed by the remelting process in the remelting furnace 100: (i) the transverse position or distribution of one or more current segments; (ii) the transverse position or distribution of multiple drip shorts; (iii) the angle or transverse position of the electrode within the crucible; (iv) the distance across the gap 115 between the electrode 110 and the ingot 120; (v) a surface profile of the electrode 110 obtained by estimating the distance across the gap 115 as a function of the transverse position of the current segments 30; (vi) the presence or duration or position of one or more side arcs 32; (vii) the presence or duration or position of one or more constricting arcs, glows, or long arcs; (viii) detection of the presence or location of cracks or defects in the electrode during the corresponding time portion of the remelting process that resulted in the ingot; (ix) the longitudinal geometry of the electrode; (x) the gas pressure or composition in the furnace; (xi) the slag depth or composition in the furnace; (xii) the occurrence or location of a shelf collapse event into the molten pool; or (xiii) transient variations in current or voltage across the gap 115.

[0039] One or more of those measured quantities may be used to generate and store a map of the ingot 120 that indicates the remelt conditions, metal quality, or specified or recommended post-melt processing as a function of longitudinal or three-dimensional position within the ingot 120. For example, the metal quality as a function of position in the ingot 120 may be classified based on the suitability of the metal for subsequent applications, e.g., jet turbine blades or nuclear power plants versus golf clubs. Note that higher quality metals and lower quality metals may be obtained from the same ingot 120 and directed to different end uses, which reduces waste or the need for further remelting. In another example, the metals of the ingot 120 may be classified (as a function of position) based on their suitability for different post-melt processing steps (e.g., machining versus extrusion versus hot or cold forging).

[0040] In some examples, conventional computer algorithms may be executed by the computer system 299 to control the remelting process and / or to map the resulting ingot 120. In some examples, quantities measured by the magnetic field sensors 201 or 202, or by other additional sensors, may be used as direct inputs to the process control algorithms or recorded as part of an ingot map. In some examples, quantities estimated, calculated, or derived from the measured quantities may be employed, such as the spatial distribution of drip shorts estimated from magnetic field and voltage measurements, or side arc positions estimated from magnetic field measurements and the difference between the input current and the primary current.

[0041] In some examples, the computer system 299 may include an artificial intelligence subsystem (AI), a machine learning subsystem (ML), or a neural network (NN). In such examples, the AI, ML, or NN may be provided with training data including (i) signals received from the magnetic field sensors 201 and / or 202 and additional sensors during the multiple remelting processes, and (ii) observed or measured metal qualities as a function of three-dimensional location within the corresponding ingot 120 resulting from those multiple remelting processes. In some examples, the training data may include magnetic field components applied by the source 300. In some examples, the signals of the various sensors may serve as training data, and in other examples, quantities estimated, calculated, or derived from the sensor signals (e.g., estimated location or distribution of the current segments 30) may be included in the training data. Once the AI, ML, or NN is properly trained, in some examples, it may be used to alter, maintain, or control one or more operating parameters of the furnace 100 during a subsequent remelting process in response to signals received from the various sensors during that process. In some examples, a trained AI, ML, or NN may be employed to map the ingot 120 based on signals received from various sensors during the remelting process that resulted in the ingot 120. In some examples, an AI, ML, or NN may be employed for both purposes. In some examples, the AI, ML, or NN may employ so-called explainable algorithms, such that the behavior of the computer system 299 during the remelting process, or the mapping of the ingot 120, may be analyzed and understood, and in other examples, such analysis may not be possible to extract from the AI, ML, or NN. In some examples, an AI, ML, or NN system may be trained to recognize and locate (longitudinally or in three dimensions) anomalies that occur during the remelting process during operation of the furnace 100.Anomaly detection may be implemented in any suitable manner, including, for example, observing changes in the mean or standard deviation (or other statistical parameter(s)) of one or more measured or estimated / calculated / derived quantities, or the time frequency of such changes.

[0042] Some specific examples may be illustrative. In a first specific example, magnetic field measurements (e.g., vertical component near gap 115), furnace gas composition (e.g., copper detected by mass spectrometry), or spectral characteristics of light generated within furnace 100 (e.g., atomic copper emission) may indicate a side arc at a given longitudinal and circumferential position of ingot 120. Computer system 299 may modify the magnetic field applied by source 300 and temporarily reduce the voltage across gap 115 until signs of side arc 32 subside or disappear, and then return furnace 100 to the previous operating condition. Alternatively or additionally, a map of ingot 120 may indicate that a volume of metal around the estimated location of side arc 32 should be discarded. In a second particular example, magnetic field measurements (both near and longitudinally displaced from the gap 115) and voltage measurements can indicate a skewed distribution of drip shorts toward the edge of the ingot 120 and a corresponding transverse displacement of the electrode 110 (which can also be shown by images collected within the furnace 100). The computer system 299 can change the transverse position or tilt of the electrode 110 as needed to re-center the drip short distribution, with or without applying a magnetic field using one or more of the sources 300. Alternatively or additionally, a map of the ingot 120 can indicate that the volume of metal surrounding the observed skewed distribution of drip shorts is downgraded for use in non-critical applications only. In a third particular example, asymmetric heating of the crucible 101 near the gap 115, asymmetric current flow into the crucible 101 near the gap 115, or images collected within the furnace 100 may indicate a so-called shelf collapse event. A map of the ingot 120 may indicate that a volume of metal around the estimated location of the shelf collapse should be discarded. Countless other examples may be implemented within the scope of this disclosure or the appended claims.

[0043] The remelt process control and ingot mapping enabled by the disclosed apparatus and methods provides several advantages including, but not limited to, one or more of improved safety, higher overall material quality, reduced waste of off-spec ingot material, and the like.

[0044] The systems and methods disclosed herein may be implemented as or by a general purpose or special purpose computer or server, or other programmable hardware device programmed through software, or as hardware or equipment "programmed" therewith or through hardwiring, or as a combination of the two. A "computer" or "server" may comprise a single machine, or may comprise multiple interacting machines (located at a single location or at multiple remote locations). The computer program or other software code, if used, may be implemented in a tangible, non-transitory, temporary or permanent storage medium or exchangeable medium, such as by including programming in microcode, machine code, network-based or web-based or distributed software modules operating together, RAM, ROM, CD-ROM, CD-R, CD-R / W, DVD-ROM, DVD±R, DVD±R / W, hard drive, thumb drive, flash memory, optical media, magnetic media, semiconductor media, or any future computer readable storage alternative. An electronic representation of a dataset may be read from, received from, or stored in any of the tangible, non-transitory computer readable media mentioned herein.

[0045] In addition to the foregoing, the following exemplary embodiments are within the scope of the present disclosure or the appended claims: Any given example below that references multiple prior examples shall be understood to refer only to prior examples with which the given example does not conflict, and to implicitly exclude prior examples with which the given example conflicts.

[0046] Example 1. (a) first and second longitudinal electrical conductors positioned end-to-end within a current-containing volume, through which a primary current flows primarily in a longitudinal direction as one or more transversely localized current segments (i) through at least a portion of the first and second conductors and (ii) spanning a gap separating the first and second conductors, the one or more current segments being movable in two transverse dimensions within the gap; and (b) a magnetic field measuring device configured to (i) measure magnetic field components, or magnitudes, in one or more spatial dimensions and (ii) at a plurality of different longitudinal locations and a plurality of different circumferential locations. and (c) a computer system having one or more electronic processors and one or more digital storage media coupled thereto, the computer system structured, connected and programmed to: (i) receive from the magnetic field sensors corresponding signals indicative of measured magnetic field components at a plurality of corresponding sensor locations longitudinally offset from the gap; and (ii) calculate an estimated transverse spatial distribution of current in or through one or both of the first conductor and the second conductor based at least in part on two or more of the measured magnetic field components.

[0047] Example 2. The apparatus of example 1, wherein at least one of the current segments is an electrical discharge or arc formed across a gap between the first conductor and the second conductor.

[0048] Example 3. The apparatus of Example 1, wherein the current-containing volume is an interior volume of a remelting furnace, the first conductor is an electrode of the remelting furnace, and the second conductor is an ingot formed by the remelting process in a crucible of the remelting furnace.

[0049] Example 4. The apparatus of Example 3, wherein at least one of the one or more current segments is an electrical discharge or arc formed across the gap between the electrode and the ingot.

[0050] Example 5. The apparatus of example 3 or 4, wherein at least one of the current segments is a transient short circuit through a droplet of molten metal dripping across the gap between the electrode and the ingot.

[0051] Example 6. The apparatus of any one of Examples 3 to 5, wherein a layer of molten slag at least partially fills the gap between the electrode and the ingot, and one or more current segments pass through the slag layer.

[0052] Example 7. The apparatus of any one of Examples 3 to 6, wherein the computer system is structured, connected, and programmed to calculate a longitudinal or transverse position of a shelf collapse event of a solidifying portion of the molten pool at the top surface of the ingot based at least in part on two or more of the measured magnetic field components.

[0053] Example 8. The apparatus of any one of Examples 1 to 7, wherein the computer system is further structured, connected, and programmed to: (i) receive corresponding signals from the magnetic field sensors indicative of measured magnetic field components at a plurality of corresponding sensor locations; and (ii) calculate an estimated transverse position or an estimated transverse distribution of one or more current segments in the gap based at least in part on two or more of the measured magnetic field components.

[0054] Example 9. The apparatus of any one of Examples 1 to 8, further comprising a transverse actuator configured to provide transverse or angular movement of the first conductor or the second conductor relative to one another, and wherein the computer system is further structured, connected, and programmed to: (i) generate one or more transverse position control signals based at least in part on one or both of an estimated transverse position or estimated transverse distribution of the one or more primary electrical discharges or an estimated relative transverse offset between the first conductor and the second conductor; and (ii) send the one or more transverse position control signals to the transverse actuator to change, maintain, or control the relative transverse position or angle of the first conductor and the second conductor.

[0055] Example 10. The apparatus of any one of Examples 1 to 9, further comprising a longitudinal actuator configured to provide longitudinal movement of the first conductor or the second conductor relative to one another, and wherein the computer system is further structured, connected, and programmed to: (i) calculate an estimated gap distance between the first conductor and the second conductor based at least in part on two or more of the measured magnetic field components; (ii) generate one or more longitudinal position control signals based at least in part on the estimated gap distance; and (ii) transmit the one or more longitudinal position control signals to the longitudinal actuator to alter, maintain, or control the estimated gap distance between the first conductor or the second conductor.

[0056] Example 11. The apparatus of any one of Examples 1 to 10, further comprising one or more magnetic field sources disposed at corresponding source locations configured around a lateral periphery of the current-containing volume and configured to apply corresponding applied magnetic fields having corresponding non-zero components directed in a transverse direction across at least a portion of the current-containing volume including the gap, and wherein the computer system is further structured, connected, and programmed to: (i) generate one or more applied magnetic field control signals based at least in part on one or both of an estimated transverse position or an estimated transverse distribution of one or more current segments in the gap; and (ii) transmit the one or more applied magnetic field control signals to the magnetic field sources to alter, maintain, or control the position or distribution of the one or more current segments in the gap.

[0057] Example 12. The apparatus of any one of Examples 1 to 11, wherein the computer system is structured, connected, and programmed to calculate, based at least in part on two or more of the measured magnetic field components, (i) an estimated relative transverse offset or relative angle between the first conductor and the second conductor, (ii) a longitudinal shape profile of one or both of the first conductor or the second conductor, or (iii) a corresponding location, size, or shape of one or more cracks, inclusions, cavities, or structural defects in one or both of the first conductor or the second conductor.

[0058] Example 13. The apparatus of any one of Examples 3 to 12, wherein the computer system is structured, connected, and programmed to: (i) receive from the magnetic field sensors corresponding signals indicative of magnetic field components measured at a plurality of corresponding sensor locations; (ii) receive signals indicative of a magnitude of the primary current and of the furnace voltage across the electrode and the ingot; (iii) detect a drip short between the electrode and the ingot based on a measured transient deviation in the primary current or the furnace voltage indicative of a drip short; and (iv) calculate an estimated transverse position of the detected drip short within the gap based at least in part on two or more of the measured magnetic field components at the time of the detected drip short.

[0059] Example 14. A method for producing a magnetic field measuring device comprising: (a) a longitudinal first conductor configured as an electrode and a longitudinal second conductor configured as an ingot positioned end-to-end within a current-containing volume within an arc furnace, through which a primary current flows primarily in the longitudinal direction as one or more primary electrical discharges (i) through at least a portion of the electrode and the ingot, and (ii) spanning a gap separating the electrode and the ingot, the one or more primary electrical discharges being movable in two transverse dimensions within the gap; and (b) a plurality of magnetic field measuring devices (i) configured to measure magnetic field components in two or more spatial dimensions and (ii) positioned at corresponding sensor locations configured around a lateral periphery of the arc furnace at a plurality of different longitudinal positions and a plurality of different circumferential positions. and (c) a computer system having one or more electronic processors and one or more digital storage media coupled thereto, the computer system structured, connected and programmed to: (i) receive from the magnetic field sensors corresponding signals indicative of magnetic field components measured at a plurality of corresponding sensor locations; (ii) receive signals indicative of a magnitude of the primary current and of a furnace voltage across the electrode and the ingot; (iii) detect a drip short between the electrode and the ingot based on a measured transient deviation in the primary current or the furnace voltage, which is indicative of a drip short; and (iv) calculate an estimated transverse position of the detected drip short within the gap based at least in part on two or more of the measured magnetic field components at a time of the detected drip short.

[0060] Example 15. The apparatus of example 13 or 14, wherein the computer system is further structured, connected, and programmed to calculate estimated transverse locations for a plurality of detected drip shorts, and to calculate a transverse spatial distribution of the plurality of estimated drip short locations.

[0061] Example 16. The apparatus of any one of Examples 13 to 15, wherein the computer system is further structured, connected, and programmed to: (i) receive corresponding signals from the magnetic field sensors indicative of measured magnetic field components at a plurality of corresponding sensor locations; and (ii) calculate an estimated transverse position or an estimated transverse distribution of one or more primary electrical discharges in the gap based at least in part on two or more of the measured magnetic field components.

[0062] Example 17. The apparatus of any one of Examples 13 to 16, further comprising one or more magnetic field sources disposed at corresponding source locations configured around a lateral periphery of the arc furnace and configured to apply corresponding applied magnetic fields having corresponding non-zero components directed in a transverse direction across at least a portion of the arc furnace including the gap, and wherein the computer system is further structured, connected, and programmed to: (i) generate one or more applied magnetic field control signals based at least in part on the estimated distribution of drip shorts or one or both of the estimated transverse positions or estimated transverse distributions of the one or more primary electrical discharges; and (ii) send the one or more applied magnetic field control signals to the magnetic field sources to alter, maintain, or control the positions or distribution of the one or more primary discharges, thereby altering, maintaining, or controlling the distribution of the drip shorts.

[0063] Example 18. The apparatus of any one of Examples 1 to 17, further comprising one or more magnetic field sources disposed at corresponding source locations configured around a lateral periphery of the current-containing volume and configured to apply corresponding applied magnetic fields having corresponding non-zero components directed in a transverse direction across at least a portion of the current-containing volume including the gap, and wherein the computer system is further structured, connected, and programmed to: (i) generate one or more applied magnetic field control signals based at least in part on one or both of an estimated transverse position or an estimated transverse distribution of one or more current segments; and (ii) transmit the one or more applied magnetic field control signals to the magnetic field sources to alter, maintain, or control the transverse position or transverse distribution of the one or more current segments within the gap.

[0064] Example 19. The apparatus of example 17 or 18, wherein the one or more magnetic field sources include one or more stationary sources.

[0065] Example 20. The apparatus of any one of Examples 17 to 19, wherein the one or more magnetic field sources include one or more sources that are longitudinally movable along the current-containing volume.

[0066] Example 21. The apparatus of any one of Examples 1 to 20, wherein the plurality of magnetic field sensors includes one or more fixed sensors.

[0067] Example 22. The apparatus of any one of Examples 1 to 21, wherein the plurality of magnetic field sensors includes one or more sensors that are longitudinally movable along the current-containing volume.

[0068] Example 23. The apparatus of any one of Examples 1 to 22, wherein the calculation based on the magnetic field components measured by the sensors includes correction for one or more of: (i) magnetic fields due to external conductors carrying currents to or from the first conductor and the second conductor; (ii) earth's magnetic field; (iii) other external magnetic fields; or (iv) misalignment of one or more sensors.

[0069] Example 24. The apparatus of any one of Examples 3 to 23, further comprising a corresponding additional sensor coupled to or positioned on or in the furnace, the corresponding additional sensor configured to measure one or more or all of: (i) a longitudinal or transverse position or velocity of the electrode or one or more actuators coupled to the electrode; (ii) a weight of the electrode; (iii) a magnitude of the operating current or a variation thereof; (iv) a difference between the operating current and the primary current; (v) a voltage drop between the electrode and the ingot or a variation thereof; (vi) an electrical resistance across the gap or a variation thereof; (vii) a temperature within the furnace; (viii) one or more temperature gradients in or along the electrode, in or along the ingot, or along or around the crucible; (ix) a pressure or composition of a gas or vapor within the furnace; (x) an optical spectral characteristic light emitted by one or more current segments; or (xi) an image of the interior of the furnace.

[0070] Example 25. A method employing the apparatus of any one of Examples 3 to 24, the method comprising: measuring, as a function of longitudinal position along an ingot formed by a remelting process in a remelting furnace, (i) a transverse position or transverse distribution of one or more current segments; (ii) a transverse position or transverse distribution of a plurality of drip shorts; (iii) an angle or transverse position of an electrode within a crucible; (iv) a distance across a gap between the electrode and the ingot; (v) a surface profile of the electrode obtained by estimating the distance across the gap as a function of transverse position of a current segment; (vi) the presence or duration or position of one or more side arcs; (vii) a (viii) detecting the presence or location of cracks or defects in the electrode during the corresponding time portion of the remelting process which resulted in the ingot; (ix) the longitudinal geometry of the electrode; (x) the gas pressure or composition in the furnace; (xi) the slag depth or composition in the furnace; (xii) the occurrence or location of a shelf collapse event into the molten pool; (xiii) the transient variation of current or voltage or electrical resistance across the gap; (xiv) the immersion depth of the electrode into the molten slag filling the gap; (xv) the measured magnetic field component; or (xvi) the applied magnetic field component.

[0071] Example 26. A method employing the apparatus of any one of Examples 3 to 24, the method comprising, in response to one or more magnetic field components measured by one or more corresponding sensors during the remelting process, or one or more estimates calculated therefrom, (i) stopping the remelting process, (ii) temporarily pausing and then resuming the remelting process, (iii) rejecting or downgrading the ingot, (iv) rejecting or downgrading only a selected portion of the ingot, (v) applying a magnetic field to alter, maintain, or control a transverse position or transverse distribution of one or more current segments within the gap, (vi) applying a magnetic field to alter, maintain, or control a transverse distribution of a plurality of drip shorts within the gap, (vii) modifying a transverse distribution of heat accumulated on a surface of the ingot, (viii) applying a magnetic field to modify, maintain, or control a transverse position or transverse distribution of one or more current segments within the gap, (viv) applying a magnetic field to modify, maintain, or control a transverse distribution of a plurality of drip shorts within the gap, (vvii) modifying a transverse distribution of heat accumulated on a surface of the ingot, (viii) applying a magnetic field to modify, maintain, or control ... (viii) applying a magnetic field to dampen or terminate a side arc, a constricting arc, a glow, or a long arc; (ix) changing, maintaining, or controlling the distance between the electrode and the ingot across the gap; (x) changing, maintaining, or controlling the angle or transverse position of the electrode within the crucible; (xi) changing, maintaining, or controlling the voltage across the gap; (xii) changing, maintaining, or controlling the electrical resistance across the gap; (xiii) changing, maintaining, or controlling the current flowing through the electrode and the ingot; (xiv) changing, maintaining, or controlling the immersion depth of the electrode into the molten slag filling the gap; or (xv) changing, maintaining, or controlling the gas pressure or composition in the furnace.

[0072] Example 27. A method employing the apparatus of Example 24, the method comprising: (a) supplying an operating current to the furnace during a remelting process using a remelt furnace, at least a portion of the operating current flowing through the furnace as a primary current; (b) using a plurality of magnetic field sensors to measure magnetic field components, or magnetic field magnitudes, in one or more spatial dimensions at some or all of the corresponding sensor locations as a function of time during the remelt process; and (c) using corresponding additional sensors to measure, as a function of time during the remelt process, (i) the longitudinal or transverse position or velocity of the electrodes, or one or more actuators coupled to the electrodes; (ii) the weight of the electrodes; (iii) the magnitude of the operating current or its variation; (iv) the difference between the operating current and the primary current; (v) the voltage drop between the electrodes and the ingot or its variation; (vi) the electrical resistance across the gap or its variation; (vii) the temperature within the furnace; (viii) one or more temperature gradients in or along the electrodes, in or along the ingot, or along or around the crucible; (ix) a gas or vapor within the furnace. (x) an optical spectrum characteristic light emitted by one or more current segments; (xi) an immersion depth of the electrode into or variation of the molten slag filling the gap; or (xii) an image of the interior of the furnace; and (d) using a computer system to do one or both of: (i) receive signals indicative of some or all of the magnetic field components measured in part (b); (ii) receive signals indicative of some or all of the quantities measured in part (c); and (iii) alter, maintain, or control one or more operating parameters of the furnace during the remelting process based at least in part on the received signals of parts (b) or (c), or a quantity or parameter calculated, estimated, or derived therefrom; or (iv) generate and store a longitudinal or three-dimensional map of the ingot resulting from the remelting process based at least in part on the received signals of parts (b) or (c), or a quantity or parameter calculated, estimated, or derived therefrom.

[0073] Example 28. (a) providing an operating current to a remelt furnace during a remelting process using the furnace, where at least a portion of the operating current flows generally longitudinally as a primary current as one or more transversely localized current segments (i) through at least a portion of a metal electrode positioned within a crucible of the remelt furnace, (ii) through at least a portion of a metal ingot formed in the crucible by melting of the electrode during the remelt process, and (iii) across a gap separating the electrode and the ingot, where the one or more current segments are movable in two transverse dimensions within the gap; (b) measuring magnetic field components, or magnetic field magnitudes, in one or more spatial dimensions at some or all of the corresponding sensor locations as a function of time during the remelt process using a plurality of magnetic field sensors disposed at corresponding fixed or movable sensor locations configured around a lateral periphery of the crucible at a plurality of different longitudinal positions and a plurality of different circumferential positions; and (c) measuring magnetic field components, or magnetic field magnitudes, in one or more spatial dimensions at some or all of the corresponding sensor locations as a function of time during the remelt process using a plurality of magnetic field sensors coupled to or on or in the furnace. using corresponding sensors positioned on the primary current to measure, as a function of time during the remelting process, one or more or all of: (i) a longitudinal or transverse position or velocity of the electrode or one or more actuators coupled to the electrode; (ii) a weight of the electrode; (iii) a magnitude of an operating current or a variation thereof; (iv) a difference between the operating current and the primary current; (v) a voltage drop between the electrode and the ingot or a variation thereof; (vi) an electrical resistance across the gap or a variation thereof; (vii) a temperature within the furnace; (viii) one or more temperature gradients within or along the electrode, within or along the ingot, or along or around the crucible; (ix) a pressure or composition of a gas or vapor within the furnace; (x) an optical spectral characteristic light emitted by one or more current segments; (xi) an immersion depth of the electrode into the molten slag filling the gap or a variation thereof; or (xii) an image of the interior of the furnace; and (d) one or more electronic processors and one or more digital storage media coupled thereto, configured, connected and programmed therefor.1. A method comprising using a computer system to do one or both of: (i) receive signals indicative of some or all of the magnetic field components measured in part (b); (ii) receive signals indicative of some or all of the quantities measured in part (c); and (iii) modify, maintain, or control one or more operating parameters of the furnace during the remelting process based at least in part on the received signals, or quantities or parameters calculated, estimated, or derived therefrom; or (iv) generate and store a longitudinal or three-dimensional map of the ingot resulting from the remelting process based at least in part on the received signals, or quantities or parameters calculated, estimated, or derived therefrom.

[0074] Example 29. Based at least in part on the received signals or quantities or parameters calculated, estimated, or derived therefrom, during the remelting process, (i) stopping the remelting process; (ii) temporarily pausing and then resuming the remelting process; (iii) rejecting or downgrading only the ingot, or selected portions of the ingot; (iv) specifying or recommending a particular post-melting treatment of only the ingot, or certain portions of the ingot; (v) applying a magnetic field to alter, maintain, or control the transverse position or transverse distribution of one or more current segments within the gap; (vi) applying a magnetic field to alter, maintain, or control the transverse distribution of a plurality of drip shorts within the gap; (vii) altering or maintaining the transverse distribution of heat accumulated on the surface of the ingot. (viii) applying a magnetic field to dampen or terminate a side arc, a constricting arc, a glow, or a long arc; (ix) changing, maintaining, or controlling the distance between the electrode and the ingot across the gap, or the immersion depth of the electrode into the molten slag filling the gap; (x) changing, maintaining, or controlling the angle or transverse position of the electrode within the crucible; (xi) changing, maintaining, or controlling the voltage across the gap; (xii) changing, maintaining, or controlling the electrical resistance across the gap; (xiii) changing, maintaining, or controlling the current flowing through the electrode and the ingot; or (xiv) changing, maintaining, or controlling the gas pressure or composition within the furnace.

[0075] Example 30. A method includes measuring, as a function of longitudinal position along an ingot formed by a remelting process in a remelting furnace, (i) a transverse position or transverse distribution of one or more current segments, (ii) a transverse position or transverse distribution of a number of drip shorts, (iii) an angle or transverse position of an electrode within a crucible, (iv) a distance across a gap between the electrode and the ingot, (v) a surface profile of the electrode obtained by estimating the distance across the gap as a function of transverse position of a current segment, (vi) the presence or duration or position of one or more side arcs, (vii) the presence or duration of one or more constricted arcs, glow, or long arcs, (viii) detecting the presence or location of cracks or defects in the electrode during a corresponding time portion of the remelting process that resulted in the ingot; (ix) the longitudinal geometry of the electrode; (x) the gas pressure or composition in the furnace; (xi) the slag depth or composition in the furnace; (xii) the occurrence or location of a shelf collapse event into the molten pool; (xiii) the transient variation of current or voltage or electrical resistance across the gap; (xiv) one or more magnetic field components; (xv) one or more applied magnetic field components; or (xvi) the immersion depth of the electrode into the molten slag filling the gap.

[0076] Example 31. The method of example 30, wherein the map indicates remelt conditions, metal quality, or specified or recommended post-melt treatment as a function of longitudinal or three-dimensional position within the ingot.

[0077] Example 32. The method of any one of Examples 25 to 31, wherein the computer system includes an artificial intelligence subsystem, a machine learning subsystem, or a neural network, and the method further includes: (A) providing, as training data, (i) the received signals of parts (b) and (c) for the multiple remelt processes and (ii) the observed or measured metal quality as a function of three-dimensional location within the corresponding ingot resulting from the multiple remelt processes to the artificial intelligence subsystem, machine learning subsystem, or neural network; (B) during a subsequent remelt process, providing the received signals of parts (b) and (c) to the artificial intelligence subsystem, machine learning subsystem, or neural network; and (C) using the artificial intelligence subsystem, machine learning subsystem, or neural network to alter, maintain, or control one or more operating parameters of the furnace during the subsequent remelt process.

[0078] Example 33. The method of any one of Examples 25 to 31, wherein the computer system includes an artificial intelligence subsystem, a machine learning subsystem, or a neural network, and the method further includes: (A) providing as training data to the artificial intelligence subsystem, the machine learning subsystem, or the neural network (i) the received signals of parts (b) and (c) for the multiple remelt processes and (ii) the observed or measured metal quality as a function of three-dimensional position within a corresponding ingot resulting from the multiple remelt processes; (B) providing the received signals of parts (b) and (c) to the artificial intelligence subsystem, the machine learning subsystem, or the neural network during a subsequent remelt process; and (C) using the artificial intelligence subsystem, the machine learning subsystem, or the neural network to generate and store a map of the ingot resulting from the subsequent remelt process, the map indicating the remelt conditions, metal quality, or specified or recommended post-melt treatment as a function of longitudinal or three-dimensional position within the ingot.

[0079] The present disclosure is illustrative and not restrictive. Further modifications will be apparent to those skilled in the art in light of the present disclosure and are intended to fall within the scope of the present disclosure or the appended claims. Equivalents of the disclosed exemplary embodiments and methods, or modifications thereof, are intended to fall within the scope of the present disclosure or the appended claims.

[0080] In the above detailed description, various features may be grouped together into several exemplary embodiments to streamline the disclosure. This method of disclosure should not be interpreted as expressing an intention that the claimed embodiments require more features than are expressly recited in the corresponding claims. Rather, as the appended claims expressly indicate, inventive subject matter may lie in less than all features of a single disclosed exemplary embodiment. Thus, the present disclosure shall be interpreted as implicitly disclosing any embodiment having any preferred subset of one or more features shown, described, or claimed in this application, including any subset that may not be expressly disclosed herein. A "preferred" subset of features includes only those features that are not incompatible or mutually exclusive with respect to other features of that subset. Thus, the appended claims are hereby incorporated in their entirety into the detailed description, with each claim standing on its own as a separate disclosed embodiment. In addition, each of the appended dependent claims shall be construed as if written in multiple dependent form and dependent on all preceding claims with which there is no conflict with that dependent claim, solely for purposes of disclosure by said incorporation of the claims into the Detailed Description. It should be noted further that the cumulative scope of the appended claims may, but does not necessarily, encompass the entirety of the subject matter disclosed in this application.

[0081] The following interpretations shall apply for purposes of this disclosure and the appended claims: The words "comprising," "including," "having," and variations thereof, wherever they appear, unless expressly stated otherwise, shall be interpreted as open-ended terms having the same meaning as if a phrase such as "at least" were added after each instance of it. The article "a" shall be interpreted as "one or more," unless "only one of," "single," or other similar limitation is expressly stated or implied in the particular context, and similarly, the article "the" shall be interpreted as "only one of the," "a single one of the," or "one or more of the," unless other similar limitation is expressly stated or implied in the particular context. The conjunction "or" should be interpreted inclusively unless (i) expressly stated otherwise, for example, by use of "either...or," "only one of," or similar phraseology, or (ii) it is understood or disclosed (implicitly or explicitly) that two or more of the listed alternatives are to be incompatible or mutually exclusive within the particular context. In the latter case, "or" will be understood to encompass only those combinations with the non-mutually exclusive alternatives. In one example, each of "dogs or cats," "one or more of dogs or cats," and "one or more dogs or cats" would be interpreted as one or more dogs with no cats, or one or more cats with no dogs, or one or more of each.

[0082] For purposes of this disclosure or the appended claims, when a numerical quantity is recited (with or without terms such as "about," "equal to," "substantially equal to," "greater than about," "less than about"), standard conventions regarding measurement precision, rounding errors, and significant digits shall apply unless a different interpretation is expressly stated or where a different interpretation is implicit or inherent (e.g., some small integer quantities). For null quantities described by phrases such as "equal to zero," "absent," "eliminated," "negligible," "prevented," etc. (with or without terms such as "about," "substantially"), each such phrase shall indicate, for practical purposes in the context of the intended operation or use of the disclosed or claimed device or method, if the quantity in question is reduced or made smaller to an extent that the overall behavior or performance of the device or method is no different from that which would have occurred if the null quantity had been virtually completely removed, strictly equal to zero, or otherwise strictly nulled. Terms such as "parallel," "perpendicular," "orthogonal," "coplanar," and "aligned" (with or without terms such as "about," "substantially") are to be construed in an analogous manner.

[0083] For purposes of this disclosure and the appended claims, labeling of elements, steps, limitations, or other parts of an embodiment, example, or claim (e.g., first, second, third, etc., (a), (b), (c), etc., or (i), (ii), (iii), etc.) is for clarity only and is not to be construed as implying any ordering or priority of the parts so labeled. If any such ordering or priority is intended, it will be explicitly recited in the embodiment, example, or claim, or in some instances it will be implicit or inherent based on the particular content of the embodiment, example, or claim.

[0084] In the appended claims, if the provisions of 35 U.S.C. 112(f) are desired to be invoked in an apparatus claim, then the word "means for" shall appear in that apparatus claim. If those provisions are desired to be invoked in a method claim, then the word "step for" shall appear in that method claim. Conversely, if the words "means for" or "step for" do not appear in a claim, then the provisions of 35 U.S.C. 112(f) are not invoked for that claim.

[0085] If any one or more disclosures are incorporated herein by reference and such incorporated disclosures are in conflict with or differ in scope from this disclosure, either in part or in whole, then this disclosure shall control to the extent of the conflict, broader disclosure, or broader definition of a term. If such incorporated disclosures are in conflict with each other, either in part or in whole, then to the extent of the conflict, the later-dated disclosure shall control.

[0086] The Abstract is optionally provided as an aid to those searching for particular subject matter within the patent document. However, the Abstract does not imply that elements, features, or limitations recited herein are necessarily covered by any particular claim. The scope of subject matter covered by each claim shall be determined by the recitation of that claim alone.

Claims

1. (a) first and second longitudinal electrical conductors positioned end-to-end within a current-containing volume, through which a primary current flows primarily in a longitudinal direction as one or more transverse localized current segments (i) through at least a portion of the first and second conductors, and (ii) spanning a gap separating the first and second conductors, the one or more current segments being movable in two transverse dimensions within the gap; (b) a plurality of magnetic field sensors (i) configured to measure magnetic field components, or magnetic field magnitudes, in one or more spatial dimensions, and (ii) disposed at corresponding sensor locations configured around a lateral periphery of said current-containing volume at a plurality of different longitudinal positions and a plurality of different circumferential positions; (c) a computer system comprising one or more electronic processors and one or more digital storage media coupled thereto, the computer system structured, connected and programmed to: (i) receive from the magnetic field sensors corresponding signals indicative of measured magnetic field components at a plurality of corresponding sensor locations longitudinally offset from the gap; and (ii) calculate an estimated transverse spatial distribution of current in or through one or both of the first conductor and the second conductor based at least in part on two or more of the measured magnetic field components. An apparatus comprising:

2. The apparatus of claim 1 , wherein at least one of the current segments is an electrical discharge or arc formed across the gap between the first conductor and the second conductor.

3. 2. The apparatus of claim 1, wherein the current-containing volume is an interior volume of a remelt furnace, the first conductor is an electrode of the remelt furnace, and the second conductor is an ingot formed by a remelting process in a crucible of the remelt furnace.

4. The apparatus of claim 3 , wherein at least one of the one or more current segments is an electrical discharge or arc formed across the gap between the electrode and the ingot.

5. 4. The apparatus of claim 3, wherein at least one of the current segments is a transient short circuit through a droplet of molten metal dripping across the gap between the electrode and the ingot.

6. The apparatus of claim 3 , wherein a layer of molten slag at least partially fills the gap between the electrode and the ingot, and the one or more current segments pass through the slag layer.

7. 4. The apparatus of claim 3, wherein the computer system is structured, connected, and programmed to calculate a longitudinal or transverse position of a shelf collapse event of a solidifying portion of a molten pool at an upper surface of the ingot based at least in part on two or more of the measured magnetic field components.

8. 4. The apparatus of claim 3, wherein the computer system is structured, connected and programmed to: (i) receive from the magnetic field sensors corresponding signals indicative of magnetic field components measured at a plurality of corresponding sensor locations; (ii) receive signals indicative of a magnitude of the primary current and of a furnace voltage across the electrode and the ingot; (iii) detect a drip short between the electrode and the ingot based on a measured transient deviation of the primary current or the furnace voltage indicative of a drip short; and (iv) calculate an estimated transverse position of the detected drip short within the gap based at least in part on two or more of the magnetic field components measured at a time of the detected drip short.

9. 13. The apparatus of claim 1, wherein the computer system is further structured, connected, and programmed to: (i) receive corresponding signals from the magnetic field sensors indicative of measured magnetic field components at a plurality of corresponding sensor locations; and (ii) calculate an estimated transverse position or an estimated transverse distribution of the one or more current segments within the gap based at least in part on two or more of the measured magnetic field components.

10. 2. The apparatus of claim 1, further comprising a transverse actuator configured to provide transverse or angular movement of the first conductor or the second conductor relative to one another, wherein the computer system is further structured, connected and programmed to: (i) generate one or more transverse position control signals based at least in part on one or both of an estimated transverse position or estimated transverse distribution of one or more primary electrical discharges or an estimated relative transverse offset between the first conductor and the second conductor; and (ii) transmit the one or more transverse position control signals to the transverse actuator to change, maintain or control the relative transverse position or angle of the first conductor and the second conductor.

11. 2. The apparatus of claim 1, further comprising a longitudinal actuator configured to provide longitudinal movement of the first conductor or the second conductor relative to one another, wherein the computer system is further structured, connected and programmed to: (i) calculate an estimated gap distance between the first conductor and the second conductor based at least in part on two or more of the measured magnetic field components; (ii) generate one or more longitudinal position control signals based at least in part on the estimated gap distance; and (ii) transmit the one or more longitudinal position control signals to the longitudinal actuator to alter, maintain or control the estimated gap distance between the first conductor or the second conductor.

12. 2. The apparatus of claim 1 , further comprising one or more magnetic field sources disposed at corresponding source locations configured around the lateral periphery of the current-containing volume and configured to apply corresponding applied magnetic fields having corresponding non-zero components directed in a transverse direction across at least a portion of the current-containing volume including the gap, wherein the computer system is further structured, connected and programmed to: (i) generate one or more applied magnetic field control signals based at least in part on one or both of the estimated transverse position or the estimated transverse distribution of the one or more current segments within the gap; and (ii) transmit the one or more applied magnetic field control signals to the magnetic field sources to alter, maintain or control a position or distribution of the one or more current segments within the gap.

13. 2. The apparatus of claim 1, wherein the computer system is structured, connected, and programmed to calculate, based at least in part on two or more of the measured magnetic field components, (i) an estimated relative transverse offset or relative angle between the first conductor and the second conductor, (ii) a longitudinal shape profile of one or both of the first conductor or the second conductor, or (iii) a corresponding location, size, or shape of one or more cracks, inclusions, cavities, or structural defects in one or both of the first conductor or the second conductor.

14. (a) a longitudinal first conductor configured as an electrode and a longitudinal second conductor configured as an ingot positioned end-to-end within a current-containing volume within an arc furnace, through which a primary current flows primarily in a longitudinal direction as one or more primary electrical discharges (i) through at least a portion of the electrode and the ingot, and (ii) spanning a gap separating the electrode and the ingot, the one or more primary discharges being movable in two transverse dimensions within the gap; (b) a plurality of magnetic field sensors (i) configured to measure magnetic field components in two or more spatial dimensions, and (ii) disposed at corresponding sensor locations configured around a lateral periphery of the arc furnace at a plurality of different longitudinal positions and a plurality of different circumferential positions; (c) a computer system comprising one or more electronic processors and one or more digital storage media coupled thereto, the computer system structured, connected and programmed to: (i) receive from the magnetic field sensors corresponding signals indicative of magnetic field components measured at a plurality of corresponding sensor locations; (ii) receive signals indicative of a magnitude of the primary current and of a furnace voltage across the electrode and the ingot; (iii) detect a drip short between the electrode and the ingot based on a measured transient deviation of the primary current or the furnace voltage indicative of a drip short; and (iv) calculate an estimated transverse position of the detected drip short within the gap based at least in part on two or more of the magnetic field components measured at a time of the detected drip short. An apparatus comprising:

15. 15. The apparatus of claim 14, wherein the computer system is further structured, connected and programmed to calculate estimated transverse locations for a plurality of detected drip shorts and to calculate a transverse spatial distribution of the plurality of estimated drip short locations.

16. 15. The apparatus of claim 14, wherein the computer system is further structured, connected and programmed to: (i) receive corresponding signals from the magnetic field sensors indicative of measured magnetic field components at a plurality of corresponding sensor locations; and (ii) calculate an estimated transverse position or an estimated transverse distribution of the one or more primary electrical discharges in the gap based at least in part on two or more of the measured magnetic field components.

17. 15. The apparatus of claim 14, further comprising one or more magnetic field sources disposed at corresponding source locations configured around the lateral periphery of the arc furnace and configured to apply corresponding applied magnetic fields having corresponding non-zero components directed in a transverse direction across at least a portion of the arc furnace including the gap, wherein the computer system is further structured, connected and programmed to: (i) generate one or more applied magnetic field control signals based at least in part on the estimated distribution of drip shorts or one or both of the estimated transverse positions or the estimated transverse distribution of the one or more primary electrical discharges; and (ii) send the one or more applied magnetic field control signals to the magnetic field sources to alter, maintain or control a position or distribution of the one or more primary discharges, thereby altering, maintaining or controlling the distribution of drip shorts.

18. (a) first and second longitudinal electrical conductors positioned end-to-end within a current-containing volume, through which a primary current flows primarily in a longitudinal direction as one or more transverse localized current segments (i) through at least a portion of the first and second conductors, and (ii) spanning a gap separating the first and second conductors, the one or more current segments being movable in two transverse dimensions within the gap; (b) a plurality of magnetic field sensors (i) configured to measure magnetic field components, or magnetic field magnitudes, in one or more spatial dimensions, and (ii) disposed at corresponding sensor locations configured around a lateral periphery of said current-containing volume at a plurality of different longitudinal positions and a plurality of different circumferential positions; (c) a computer system comprising one or more electronic processors and one or more digital storage media coupled thereto, the computer system structured, connected and programmed to: (i) receive from the magnetic field sensors corresponding signals indicative of measured magnetic field components at a plurality of corresponding sensor locations; and (ii) calculate an estimated transverse spatial distribution of a current segment in the gap, or of a current in or through one or both of the first conductor and the second conductor, based at least in part on two or more of the measured magnetic field components. An apparatus comprising: (d) the current-containing volume is an interior volume of a remelt furnace, the first conductor is an electrode of the remelt furnace, and the second conductor is an ingot formed by a remelting process in a crucible of the remelt furnace; (e) the apparatus further comprises a corresponding additional sensor coupled to or positioned on or in the furnace, the corresponding additional sensor configured to measure one or more or all of: (i) a longitudinal or transverse position or velocity of the electrode or one or more actuators coupled to the electrode; (ii) a weight of the electrode; (iii) a magnitude of an operating current or a variation thereof; (iv) a difference between the operating current and the primary current; (v) a voltage drop between the electrode and the ingot or a variation thereof; (vi) an electrical resistance across the gap or a variation thereof; (vii) a temperature within the furnace; (viii) one or more temperature gradients in or along the electrode, in or along the ingot, or along or around the crucible; (ix) a pressure or composition of a gas or vapor within the furnace; (x) an optical spectral characteristic light emitted by the one or more current segments; or (xi) an image of the interior of the furnace.

19. 20. A method employing the apparatus of claim 18, the method comprising: measuring, as a function of longitudinal position along the ingot formed by a remelting process in the remelting furnace, (i) the transverse position or transverse distribution of one or more current segments; (ii) the transverse position or transverse distribution of a number of drip shorts; (iii) the angle or transverse position of the electrode within the crucible; (iv) the distance across the gap between the electrode and the ingot; (v) a surface profile of the electrode obtained by estimating the distance across the gap as a function of transverse position of the current segments; (vi) the presence or duration or position of one or more side arcs; (vii) one or more side arcs; (viii) detecting the presence or location of cracks or defects in the electrode during a corresponding time portion of the remelting process that resulted in the ingot; (ix) the longitudinal geometry of the electrode; (x) gas pressure or composition in the furnace; (xi) slag depth or composition in the furnace; (xii) occurrence or location of a shelf collapse event into a molten pool; (xiii) transient variations in current or voltage or electrical resistance across the gap; (xiv) immersion depth of the electrode into molten slag filling the gap; (xv) measured magnetic field components; or (xvi) applied magnetic field components.

20. 20. A method employing the apparatus of claim 18, the method comprising the steps of: (i) stopping the remelting process; (ii) temporarily pausing and then resuming the remelting process; (iii) rejecting or downgrading the ingot; (iv) rejecting or downgrading only a selected portion of the ingot; (v) applying a magnetic field to alter, maintain, or control a transverse position or transverse distribution of one or more current segments in the gap; (vi) applying a magnetic field to alter, maintain, or control a transverse distribution of a plurality of drip shorts in the gap; (vii) altering, maintaining, or controlling a transverse distribution of heat accumulated on a surface of the ingot; (viii) applying a magnetic field to dampen or terminate a side arc, a constricting arc, a glow, or a long arc; (ix) changing, maintaining, or controlling the distance between the electrode and the ingot across the gap; (x) changing, maintaining, or controlling the angle or transverse position of the electrode within the crucible; (xi) changing, maintaining, or controlling the voltage across the gap; (xii) changing, maintaining, or controlling the electrical resistance across the gap; (xiii) changing, maintaining, or controlling the current flowing through the electrode and the ingot; (xiv) changing, maintaining, or controlling the immersion depth of the electrode into the molten slag filling the gap; or (xv) changing, maintaining, or controlling the gas pressure or composition in the furnace.

21. 20. A method employing the apparatus of claim 18, the method comprising: (a) providing an operating current to the remelt furnace during a remelting process using the furnace, at least a portion of the operating current flowing through the furnace as the primary current; (b) using the plurality of magnetic field sensors to measure magnetic field components, or magnetic field magnitudes, in one or more spatial dimensions at some or all of the corresponding sensor locations as a function of time during the remelting process; (c) using the corresponding additional sensors to measure, as a function of time during the remelting process, one or more or all of: (i) a longitudinal or transverse position or velocity of the electrode or one or more actuators coupled to the electrode; (ii) a weight of the electrode; (iii) a magnitude or variation of the operating current; (iv) a difference between the operating current and the primary current; (v) a voltage drop between the electrode and the ingot or a variation thereof; (vi) an electrical resistance across the gap or a variation thereof; (vii) a temperature within the furnace; (viii) one or more temperature gradients within or along the electrode, within or along the ingot, or along or around the crucible; (ix) a pressure or composition of a gas or vapor within the furnace; (x) an optical spectral characteristic light emitted by the one or more current segments; (xi) an immersion depth of the electrode into the molten slag filling the gap or a variation thereof; or (xii) an image of the interior of the furnace; (d) using the computer system to one or both of: (i) receive signals indicative of some or all of the magnetic field components measured in part (b); (ii) receive signals indicative of some or all of the quantities measured in part (c); and (iii) modify, maintain, or control one or more operating parameters of the furnace during the remelting process based at least in part on the received signals of parts (b) or (c), or quantities or parameters calculated, estimated, or derived therefrom; or (iv) generate and store a longitudinal or three-dimensional map of the ingot resulting from the remelting process based at least in part on the received signals of parts (b) or (c), or quantities or parameters calculated, estimated, or derived therefrom. A method comprising:

22. (a) supplying an operating current to a remelt furnace during a remelting process using the furnace, at least a portion of the operating current flowing generally longitudinally as a primary current as one or more transverse localized current segments (i) through at least a portion of a metal electrode positioned within a crucible of the remelt furnace, (ii) through at least a portion of a metal ingot formed in the crucible by melting of the electrode during the remelt process, and (iii) spanning a gap separating the electrode and the ingot, the one or more current segments being movable in two transverse dimensions within the gap; (b) using a plurality of magnetic field sensors disposed at corresponding fixed or movable sensor locations configured around a lateral periphery of the crucible at a plurality of different longitudinal positions and a plurality of different circumferential positions, measuring magnetic field components, or magnetic field magnitudes, in one or more spatial dimensions at some or all of the corresponding sensor locations as a function of time during the remelting process; (c) using corresponding sensors coupled to or positioned on or in the furnace, to measure, as a function of time during the remelting process, (i) the longitudinal or transverse position or velocity of the electrode or one or more actuators coupled to the electrode, (ii) the weight of the electrode, (iii) the magnitude of the operating current or its variation, (iv) the difference between the operating current and the primary current, (v) the voltage drop between the electrode and the ingot or its variation, (vi) the electrical resistance across the gap or its variation, (vii) the longitudinal or transverse position or velocity of the electrode or one or more actuators coupled to the electrode, (ii) the weight of the electrode, (iii) the magnitude of the operating current or its variation, (iv) the difference between the operating current and the primary current, (v) the voltage drop between the electrode and the ingot or its variation, (vii) the electrical resistance across the gap or its variation, (viii ... electrical resistance across the gap or its variation, (viiii) the longitudinal or transverse position or velocity of the electrode or one or more actuators coupled to the electrode, (ii) the weight of the electrode, (iii) the magnitude of the operating current or its variation, (iv) the difference between the operating current and the primary current, (v) the voltage drop between the electrode and the ingot or its variation, (viiii) the electrical resistance across the gap or its variation, (viiii) the electrical resistance across the gap or its variation, (viiii) the electrical resistance across the gap or its variation, (viiii) the electrical resistance across the gap or its variation, (viiii) the electrical resistance across the gap or its variation, (viiii) the electrical resistance across the gap or its variation, (viiii) the electrical resistance across the gap or its variation, (viiii) the electrical resistance across the gap or its (viii) one or more temperature gradients in or along the electrode, in or along the ingot, or along or around the crucible; (ix) pressure or composition of gas or vapor in the furnace; (x) optical spectrum characteristic light emitted by the one or more current segments; (xi) immersion depth or variation of the electrode into the molten slag filling the gap; or (xii) images of the interior of the furnace; (d) using a computer system, comprising one or more electronic processors and one or more digital storage media coupled thereto, and structured, connected, and programmed therefor, to do one or both of: (i) receiving signals indicative of some or all of the magnetic field components measured in part (b); (ii) receiving signals indicative of some or all of the quantities measured in part (c); and (iii) modifying, maintaining, or controlling one or more operating parameters of the furnace during the remelting process based at least in part on the received signals, or quantities or parameters calculated, estimated, or derived therefrom; or (iv) generating and storing a longitudinal or three-dimensional map of the ingot resulting from the remelting process based at least in part on the received signals, or quantities or parameters calculated, estimated, or derived therefrom. A method comprising:

23. Based at least in part on the received signals, or quantities or parameters calculated, estimated, or derived therefrom, during the remelting process, (i) stopping the remelting process; (ii) temporarily pausing and then resuming the remelting process; (iii) rejecting or downgrading the ingot, or only selected portions of the ingot; (iv) specifying or recommending a particular post-melting treatment for the ingot, or only certain portions of the ingot; (v) applying a magnetic field to alter, maintain, or control a transverse position or transverse distribution of one or more current segments within the gap; (vi) applying a magnetic field to alter, maintain, or control a transverse distribution of a plurality of drip shorts within the gap; (vii) altering, maintaining, or controlling a transverse distribution of heat accumulated on a surface of the ingot.

23. The method of claim 22, comprising performing one or more of: (viii) applying a magnetic field to attenuate or control a side arc, a constricting arc, a glow, or a long arc; (ix) changing, maintaining, or controlling the distance between the electrode and the ingot across the gap, or the immersion depth of the electrode into the molten slag filling the gap; (x) changing, maintaining, or controlling the angle or transverse position of the electrode within the crucible; (xi) changing, maintaining, or controlling the voltage across the gap; (xii) changing, maintaining, or controlling the electrical resistance across the gap; (xiii) changing, maintaining, or controlling the current flowing through the electrode and the ingot; or (xiv) changing, maintaining, or controlling the gas pressure or composition in the furnace.

24. The method further comprises: (i) a transverse position or distribution of one or more current segments; (ii) a transverse position or distribution of a number of drip shorts; (iii) an angle or transverse position of the electrode within the crucible; (iv) a distance across the gap between the electrode and the ingot; (v) a surface profile of the electrode obtained by estimating the distance across the gap as a function of transverse position of the current segments; (vi) a presence or duration or position of one or more side arcs; (vii) one or more constricting arcs, glows, or long arcs; 23. The method of claim 22, comprising recording one or more of: (i) the presence or duration or location of cracks in the electrode during a corresponding time portion of the remelting process that resulted in the ingot; (ii) the presence or duration or location of cracks in the electrode during a corresponding time portion of the remelting process that resulted in the ingot; (iii) the longitudinal geometry of the electrode; (x) the gas pressure or composition in the furnace; (xi) the slag depth or composition in the furnace; (xii) the occurrence or location of a shelf collapse event into a molten pool; (xiii) transient variations in current or voltage or electrical resistance across the gap; (xiv) one or more magnetic field components; (xv) one or more applied magnetic field components; or (xvi) the immersion depth of the electrode into the molten slag filling the gap.

25. 25. The method of claim 24, wherein the map indicates remelt conditions, metal quality, or prescribed or recommended post-melt treatments as a function of longitudinal or three-dimensional position within the ingot.

26. the computer system includes an artificial intelligence subsystem, a machine learning subsystem, or a neural network, and the method further comprises: providing as training data to the artificial intelligence subsystem, the machine learning subsystem, or the neural network: (i) the received signals of parts (b) and (c) for a plurality of remelting processes, and (ii) observed or measured metal qualities as a function of three-dimensional position within a corresponding ingot resulting from the plurality of remelting processes; providing the received signals of parts (b) and (c) to the artificial intelligence subsystem, the machine learning subsystem, or the neural network during a subsequent remelting process; using the artificial intelligence subsystem, the machine learning subsystem, or the neural network to modify, maintain, or control one or more operating parameters of the furnace during the subsequent remelting process; 23. The method of claim 22, further comprising:

27. and wherein the computer system includes an artificial intelligence subsystem, a machine learning subsystem, or a neural network, and the method further comprises: providing, as training data to the artificial intelligence subsystem, the machine learning subsystem, or the neural network, (i) the received signals of parts (b) and (c) for a plurality of remelting processes and (ii) observed or measured metal qualities as a function of three-dimensional position within the corresponding ingot resulting from the plurality of remelting processes; providing the received signals of parts (b) and (c) to the artificial intelligence subsystem, the machine learning subsystem, or the neural network during a subsequent remelting process; using the artificial intelligence subsystem, the machine learning subsystem, or the neural network to generate and store a map of the ingot resulting from the subsequent remelting process, the map indicating remelting conditions, metal quality, or specified or recommended post-melting treatments as a function of longitudinal or three-dimensional position within the ingot; 23. The method of claim 22, further comprising:

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