EIGA coil with annular windings

Abstract

To provide an EIGA coil, a device for carrying out an EIGA process, and a method for producing high-purity metal powder allowing for contamination and / or damage in / to an EIGA system due to liquid drops from dissolution of an electrode to be avoided.SOLUTION: An EIGA coil 10 comprises a plurality of windings 12A, 12B, 12C arranged coaxially to a center axis M, the windings 12A, 12B, 12C are arranged spaced from one another in an axial direction. The plurality of windings 12A, 12B, 12C are each formed in a ring shape discontinued by a gap 14A, 14B, 14C, are distant equally to the center axis M and are extending in a plane perpendicular to the center axis M. Out of the plurality of windings 12A, 12B, 12C, adjacent windings 12A, 12B; 12B, 12C are mutually connected through connections 20AB, 20BC, respectively.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an EIGA (Electrode Induction Melting (Inert) Gas Atomization) coil for partially melting an electrode in order to produce high-quality and pure metal powder. The EIGA coil refers to an induction coil for an EIGA system for performing the EIGA method. Furthermore, the present invention relates to an apparatus for performing the EIGA method and the EIGA method for producing high-purity metal powder.

Background Art

[0002] The EIGA method for producing high-purity metal or noble metal powder (for example, powder of titanium, zirconium, niobium and tantalum alloys) without ceramics is based on an electrode induction melting process. A rotating electrode suspended vertically is continuously supplied to a conical induction coil (EIGA coil) arranged below the rotating electrode in a vacuum or inert gas atmosphere, and the coil non-contactingly partially melts or fuses it. The rotational movement of the electrode about the longitudinal axis of the electrode itself ensures uniform melting of the electrode. Then, the jet of molten material generated by the partial melting or fusing process flows through an inert gas nozzle arranged below the induction coil (EIGA coil), where the molten jet is atomized or vaporized. Next, the mist of micro droplets solidifies in a downstream atomization tower to form spherical fine powder. The formed powder is collected and accumulated in a vacuum-sealed container.

[0003] Rod electrodes made of the desired metal or special alloy can be used in the EIGA method. Specifically, these electrodes can have a maximum diameter of 150 mm and a maximum length of 1000 mm.

[0004] The conical design of the EIGA coil (induction coil) and the set generator frequency are optimized to melt the electrodes and allow the molten material to drip from one end of the electrodes. Conventional EIGA coils are in the form of a conical spiral or a conical curve extending in a cone shape. For this purpose, the copper tube forming the winding of the EIGA coil is actually wound along a predefined form.

[0005] The above-described type of EIGA method and related EIGA systems are disclosed, for example, in Patent Document 1.

[0006] When performing the EIGA method, in known EIGA systems, it is possible that droplets of molten metal detached from the electrodes may not fall precisely through the inert gas nozzle. Some droplets may not fall precisely, instead landing on, for example, the edge or frame of the low-temperature inert gas nozzle, where they solidify and, under certain circumstances, partially or completely clog the nozzle. Alternatively, detached droplets may strike the induction coil, causing a short circuit and interrupting the process flow. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] German Patent Application Publication No. 4102101 [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, an object of the present invention is to overcome the shortcomings of the prior art. Specifically, one object of the present invention is to provide an EIGA coil, an apparatus for performing the EIGA process, and a method for producing high-purity metal powder that avoid contamination and / or damage to the EIGA system by droplets that have melted off the electrodes. [Means for solving the problem]

[0009] These objectives are achieved by the EIGA coil for cutting electrodes, the apparatus for performing the EIGA method, and the method for producing high-purity metal powder, as defined in the independent claims. Further developments and embodiments of the EIGA coil, the apparatus, and the method are the subject of the dependent claims and the following description.

[0010] The EIGA coil according to the present invention, for partially melting and cutting electrodes, comprises a plurality of windings, which are arranged coaxially with respect to the central axis of the EIGA coil and are spaced apart from each other in the axial direction. The central axis of the EIGA coil extends coaxially with the longitudinal axis of the electrode.

[0011] In the context of the present invention, the term "EIGA coil" means an induction coil for an EIGA system or for performing the EIGA method. The EIGA coil may include at least two windings, preferably at least three windings, or more than three windings.

[0012] According to the present invention, each of the plurality of windings is in the form of a ring interrupted by a gap. Thus, the EIGA coil includes a number of rings corresponding to the number of windings, each of which is interrupted by a narrow gap and therefore not closed. More specifically, each of the rings is a ring segment including a first end and a second end, with the associated gap located between the two ends of the ring segment. Each ring segment is referred to as an interrupted ring or ring in the context of the present invention because the associated gap is so narrow that it forms a nearly complete ring.

[0013] According to the present invention, each of the interrupted rings is equidistant from the central axis and extends in a plane perpendicular to the central axis, and this plane is related to each of the rings. In other words, each of the plurality of windings extends in its respective related plane perpendicular to the central axis. Thus, the planes on which each of the individual rings or windings extends are parallel to each other. That is, the rings or windings are arranged parallel to each other. During operation, the plane on which each of the individual rings or windings extends is horizontal. It will be understood that if the windings or rings are three-dimensional objects and each winding or ring (more precisely, a ring torus) extends in only one plane perpendicular to the central axis, it means that the three-dimensional objects extend in an orientation according to or coincident with this plane. In other words, if each winding or ring extends in only one plane perpendicular to the central axis, it means that the horizontal cross-sectional area of ​​the winding or ring forming a (nearly perfect) circular ring extends in this plane only.

[0014] Adjacent windings among the plurality of windings are connected to each other by connecting portions. These connecting portions can be connected to the adjacent windings in the region of the associated gap. Specifically, each connecting portion can connect the second end of one of the plurality of windings to the first end of a winding adjacent to that one of the plurality of windings.

[0015] The EIGA coil may have an overall conical design. For this purpose, at least two of the windings or annular rings may have different inner diameters. In one embodiment, all the windings of the EIGA coil may have different inner diameters. Alternatively, some windings may have the same inner diameter, or they may have different inner diameters compared to further windings of the EIGA coil. Specifically, the EIGA coil may have an overall tapered shape when viewed along the central axis in the direction of the downstream inert gas nozzle. For this purpose, windings of the EIGA coil located closer to the downstream inert gas nozzle have a smaller inner diameter than, or at most substantially the same as, windings further from the inert nozzle, and the winding closest to the inert gas nozzle has a smaller inner diameter than the winding furthest from the inert nozzle.

[0016] Since each of the plurality of windings extends only within a relevant plane perpendicular to the central axis, an orientation-symmetric Lorentz force acting on the electrode can be generated using the EIGA coil according to the present invention. Because these orientation-symmetric Lorentz forces acting on the electrode are balanced, lateral deflection of the electrode is prevented, and the electrode remains coaxial with the central axis of the EIGA coil throughout the entire EIGA process. This ensures that the lower tip of the electrode, partially melted by the EIGA coil, is precisely positioned above the center of the inert gas nozzle, thereby guaranteeing that the generated jet or droplet of molten metal always passes through the center without contacting the edge of the nozzle.

[0017] In the helical structure of EIGA coils known in the prior art, opposing winding sections are at different distances from the electrode. Therefore, the inventors of the present invention recognized that the Lorentz force generated by such an EIGA coil and acting on the electrode is azimuthally asymmetric, deflecting the electrode from its vertical orientation. As a result, a deflection angle is created between the central axis of the EIGA coil and the longitudinal axis of the electrode. The lower tip of the electrode is no longer centered on the inert gas nozzle. Consequently, droplets detached from the electrode may solidify upon contact with the edge or frame of the low-temperature inert gas nozzle, potentially clogging part or all of the nozzle. Furthermore, molten droplets may contact the induction coil, contaminating or short-circuiting it. Additionally, the electrode itself may come into contact with the EIGA coil, causing a short circuit. These undesirable effects are amplified because the electrode continuously rotates around the deflected longitudinal axis. These drawbacks can be mitigated by the EIGA coil according to the present invention and the Lorentz force acting azimuthally symmetrically on the electrode it can generate.

[0018] In a further embodiment of the EIGA coil, the connection portion may extend in the plane of the central axis, that is, in the plane in which the vertical central axis of the EIGA coil exists. For example, the connection portion may extend parallel to the central axis of the EIGA coil. The connection portion may extend perpendicular to the plane of the winding. More specifically, each of the connection portions connecting adjacent windings may extend with respect to the central axis of the EIGA coil as described above. In the assembled state, the windings may extend, for example, horizontally, and / or the connection portions may extend, for example, vertically.

[0019] According to one embodiment, the gap may be 0.5 mm to 30 mm wide, preferably 2 mm to 20 mm, more preferably 5 mm to 10 mm wide. The gap may be at least 0.5 mm wide, particularly at least 2 mm, preferably at least 5 mm wide. In an embodiment, the gap may be 30 mm or less, particularly 20 mm or less, preferably 10 mm or less. Here, the gap width means the distance between the first end and the second end of the associated winding or ring. The above-mentioned range of the gap width may be applied to the gap of each winding of the EIGA coil. The gaps of different windings may have the same width or may have different widths. A gap width of 0.5 mm to 30 mm, preferably 2 mm to 20 mm, more preferably 5 mm to 10 mm can ensure that the overall arrangement of the EIGA coil is sufficiently azimuthal, thereby ensuring that a substantially and sufficiently azimuthal Lorentz force is applied to the electrodes.

[0020] Of the multiple windings of the EIGA coil, the winding with the largest inner diameter may have an inner diameter of 40 mm to 300 mm. The dimensions of the windings of the EIGA coil, in particular the dimensions of the uppermost winding of the EIGA coil, i.e., the winding closest to the suspension portion of the electrode, may be selected according to the dimensions of the electrode to be cut. Of the multiple windings, the winding with the smallest inner diameter may have an inner diameter of 10 mm to 100 mm, preferably 20 mm to 50 mm. The winding with the smallest inner diameter may have an inner diameter of at least 10 mm, preferably at least 20 mm. The winding with the smallest inner diameter may have an inner diameter of 100 mm or less, preferably 50 mm or less. It will be understood that an EIGA coil with a winding with a relatively large inner diameter may have a relatively large gap width within the above defined range. Correspondingly, an EIGA coil with a winding with a relatively small inner diameter may have a relatively small gap width within the above defined range.

[0021] In a further embodiment, the EIGA coil may have different cross-sectional shapes with respect to shape and / or dimensions. For example, the EIGA coil may have an elliptical, circular, rectangular, square, or other cross-section. For example, the cross-sectional shape of the EIGA coil may vary in shape and / or dimensions within the same winding or between different windings.

[0022] In particular, the EIGA coil can be made from a non-ceramic copper material.

[0023] The EIGA coil may be manufactured using an additive manufacturing process. Specifically, the EIGA coil can be manufactured by the use of a 3D printing process, for example, the use of a selective laser melting process. Alternatively, the EIGA coil can be manufactured using an electron beam melting process, binder jetting, or any other arbitrary additive manufacturing process. The manufacturing of the EIGA coil according to the present invention using an additive manufacturing process is particularly evident in the fact that a very small gap width of the ring can be realized in this way. Further, the additive manufacturing process enables the formation of interconnecting portions that extend perpendicular to the windings between adjacent windings. None of these could be achieved in the conventional EIGA coil manufacturing process. In the conventional EIGA coil manufacturing process, a copper tube filled with sand is bent and the windings of the EIGA coil are formed using a pre-defined form, which highly restricts the formation of the windings.

[0024] Another aspect of the present invention relates to an apparatus or an EIGA system for performing the EIGA method. The apparatus includes an EIGA coil of the type described above. The apparatus includes an electrode of a metal or metal alloy to be melted, disposed coaxially with the plurality of windings. The electrode partially extends into the EIGA coil and is displaceable relative to the EIGA coil along the longitudinal direction of the electrode so as to be melted by the EIGA coil. Further, the electrode is rotatable about its longitudinal axis. Furthermore, the apparatus includes a nozzle or an inert gas nozzle for atomizing the melted electrode material, disposed coaxially with the electrode and the plurality of coils.

[0025] The apparatus may further include an atomization tower in which the atomized electrode material can solidify to form spherical fine particle powder.

[0026] Another aspect of the present invention relates to an EIGA method for producing high purity metal powder. The method includes - displacing an electrode relative to an EIGA coil, thereby partially introducing the electrode into the interior of the EIGA coil; - applying an alternating current to the EIGA coil to partially melt the electrode by generating a Lorentz force azimuthally symmetric with respect to the longitudinal axis of the electrode; and - atomizing the melted electrode material using an inert gas nozzle disposed downstream of the EIGA coil.

[0027] In particular, the electrode can be partially melted using an EIGA coil of the type described above.

[0028] The electrode can be rotated about its longitudinal axis during execution of the method.

[0029] Although some aspects and features have been described only with respect to the EIGA coil, they are equally applicable to the apparatus or EIGA system, and / or the EIGA method, and corresponding further embodiments, and vice versa.

[0030] Exemplary embodiments of the present invention will be described in more detail below with reference to the attached schematic diagrams. [Brief explanation of the drawing]

[0031] [Figure 1] This is a perspective view showing an EIGA coil according to an exemplary embodiment. [Figure 2] Figure 1 is a front view of an EIGA coil according to an exemplary embodiment. [Figure 3] Figure 1 is a side view of an EIGA coil according to an exemplary embodiment. [Figure 4] Figure 1 is a schematic top view of an EIGA coil according to an exemplary embodiment. [Figure 5] This is a schematic diagram of the connection section of an EIGA coil according to a further exemplary embodiment. [Figure 6] Figure 1 is a schematic cross-sectional view of an EIGA coil according to an exemplary embodiment. [Figure 7] This is a schematic cross-sectional view of the EIGA system in its initial state according to an exemplary embodiment. [Figure 8] Figure 7 is a schematic cross-sectional view of the EIGA system in a further operating state. [Figure 9] This is a schematic cross-sectional view of the initial state of the prior art EIGA system. [Figure 10] Figure 9 is a schematic cross-sectional view of the EIGA system in its deflection state. [Modes for carrying out the invention]

[0032] Identical reference numerals in the figures indicate the same or similar functions and / or similar elements.

[0033] Figures 1 to 3 show exemplary embodiments of the EIGA coil 10 according to the present invention for partially melting and cutting electrodes, in perspective view (Figure 1), front view (Figure 2), and side view (Figure 3). Figure 4 is a schematic top view of the EIGA coil 10.

[0034] The EIGA coil 10, which is an induction coil for the EIGA system used to perform the EIGA method, includes multiple windings 12A, 12B, and 12C. In the illustrated exemplary embodiment, the EIGA coil 10 includes three windings 12A, 12B, and 12C. In other exemplary embodiments, the EIGA coil may include more than three windings.

[0035] The windings 12A, 12B, and 12C are arranged coaxially with respect to the central axis M of the EIGA coil 10. Furthermore, the windings 12A, 12B, and 12C are spaced apart axially when viewed from the direction of the central axis M. Each of the windings 12A, 12B, and 12C has a different inner and outer diameter. The uppermost winding 12A in Figures 1 to 3 has the largest inner and outer diameters among the three windings 12A, 12B, and 12C, while the lowermost winding 12C in Figures 1 to 3 has the smallest inner and outer diameters among the three windings 12A, 12B, and 12C. The inner and outer diameters of the middle winding 12B, positioned between the uppermost winding 12A and the lowermost winding 12C, are between the inner and outer diameters of the uppermost winding 12A and the lowermost winding 12C, respectively. Thus, the EIGA coil 10 has a conical shape when viewed as a whole. During operation, the EIGA coil 10 is positioned such that the uppermost winding 12A, which has the largest inner and outer diameters, faces the electrode suspension section (not shown), and the lowermost winding 12B, which has the smallest inner and outer diameters, faces the inert gas nozzle (not shown). Exemplary inner diameters are shown numerically with respect to Figure 6.

[0036] Each of the windings 12A, 12B, and 12C has the shape of a ring (more precisely, a ring torus) interrupted by its respective associated gaps 14A, 14B, and 14C. Compared to the dimensions of the EIGA coil 10, particularly the dimensions of the windings 12A, 12B, and 12C, each of the gaps 14A, 14B, and 14C has a very small width B. For example, each of the three gaps 14A, 14B, and 14C may have a width B of 0.5 mm to 30 mm. Preferably, each of the gaps 14A, 14B, and 14C has a width of at least 2 mm to minimize the risk of short circuits and / or sparking. Because gaps 14A, 14B, and 14C interrupt rings 12A, 12B, and 12C, the rings are not closed, and therefore each of rings 12A, 12B, and 12C has first ends 16A, 16B, and 16C and second ends 18A, 18B, and 18C. In the illustrated exemplary embodiment, the width B of the three gaps 14A, 14B, and 14C is the same. However, in an alternative exemplary embodiment, different gaps may have different widths.

[0037] As can be seen in Figures 1 to 3, and especially in Figure 4, each of the rings 12A, 12B, and 12C is equidistant from the central axis M of the EIGA coil 10. That is, each of the rings 12A, 12B, and 12C has approximately the same distance from the central axis M when viewed along its inner circumferential surface.

[0038] Furthermore, as shown in Figures 1 to 4, each of the windings 12A, 12B, and 12C, or each of the rings 12A, 12B, and 12C, is oriented only horizontally. That is, each of the windings 12A, 12B, and 12C extends only in a plane perpendicular to the central axis M, and this plane is associated with each winding 12A, 12B, and 12C. More specifically, these windings extend in the same orientation as this associated plane. The windings 12A, 12B, and 12C are aligned parallel to each other. This is a significant difference from the prior art EIGA coil, which has helical windings in which the windings extend helically in all three spatial directions.

[0039] In the EIGA coil 10 according to the present invention, each of the windings 12A, 12B, and 12C is aligned according to a related plane perpendicular to the central axis M, and each of the windings or each of the rings 12A, 12B, and 12C is equidistant from the central axis M. Therefore, it is possible to generate an orientation-symmetric Lorentz force acting on the electrodes using the EIGA coil 10 according to the present invention. The resulting effects and advantages will be described in more detail below with reference to Figures 7 to 10.

[0040] Adjacent windings 12A and 12B, or 12B and 12C, of ​​the EIGA coil 10 are connected to each other by connecting portions 20AB and 20BC, respectively. More specifically, connecting portion 20AB connects the second end 18A of winding 12A to the first end 16B of winding 12B. Thus, connecting portion 20BC connects the second end 18B of winding 12B to the first end 16C of winding 12C. In the exemplary embodiment of Figure 1, the connecting portions 20AB and 20BC are arranged to extend laterally with respect to the central axis M, but in other exemplary embodiments, different orientations of the connecting portions may be preferably provided, which will be described in more detail with reference to Figure 5.

[0041] The first end 16A of the uppermost winding 12A and the second end 18C of the lowermost winding 12C are connected via terminals 22A and 22C to a voltage source for applying an AC voltage to the EIGA coil 10, respectively.

[0042] The windings 12A, 12B, 12C, the connectors 20AB, 20BC, and the terminals 22A, 22C are made from non-ceramic copper material. In detail, the windings 12A, 12B, 12C, the connectors 20AB, 20BC, and the terminals 22A, 22C of the EIGA coil 10 in the illustrated exemplary embodiment are hollow cylindrical.

[0043] As can be seen from Figure 1, the connecting portions 20AB and 20BC have different cross-sectional shapes from the windings 12A, 12B, and 12C. However, in further exemplary embodiments, the windings and the connecting portions may have the same cross-sectional shape.

[0044] Figure 5 schematically shows an enlarged cross-section of an EIGA coil according to a further exemplary embodiment. The enlarged cross-section shows a specific design of the connectors 120AB and 120BC, where each connector extends in the plane of the central axis M and is therefore essentially perpendicular to the windings 12A, 12B, and 12C. Thus, the windings 12A, 12B, and 12C extend horizontally during operation and in the illustrated depiction, while the connectors 120AB and 120BC extend vertically. This structural design of the connectors 120AB and 120BC perpendicular to the windings 12A, 12B, and 12C enables the provision of an EIGA coil having gaps 14A, 14B, and 14C with a particularly small width B. By making the width B of the gaps 14A, 14B, and 14C particularly small, the windings 12A, 12B, and 12C can be formed in the form of a slightly interrupted, and therefore nearly complete ring, thereby increasing the overall symmetry of the arrangement and further improving the application of azimuthal symmetric Lorentz forces to the electrodes.

[0045] Figure 6 is a schematic cross-sectional view of the EIGA coil 10 according to the exemplary embodiment described above. In the EIGA coil 10 of Figure 6, the uppermost winding 12A has the largest inner diameter L1, i.e., a maximum length of 300 mm, among the multiple windings 12A, 12B, and 12C. The lowermost winding 12C has the smallest inner diameter L3, i.e., a length of at least 10 mm, among the multiple windings 12A, 12B, and 12C.

[0046] The EIGA coil 10 has a conical shape in appearance due to the illustrated configuration (windings 12A, 12B, and 12C, having different diameters, are arranged coaxially with respect to each other and spaced apart in the axial direction). Two wires K1 and K2 are symmetrical with respect to the central axis M and extend over an angle β, passing through the center point P of the vertical cross-section of the windings 12A, 12B, and 12C, respectively. The angle β is between 30 and 180 degrees, preferably 90 degrees. The center point P through which wire K1 passes is located on the opposite side of the center point P through which wire K2 passes with respect to the central axis M.

[0047] Figure 7 is a schematic cross-sectional view of an EIGA system 30 for performing the EIGA method, which comprises an EIGA coil 10, an electrode 40 having a longitudinal axis A, and an inert gas nozzle 50. In Figure 7, the EIGA system is in its initial state at time t=0, which corresponds to the initial power-on of the EIGA coil 10. To better illustrate the orientation of the components of the EIGA system relative to each other, a virtual cone C formed by the winding of the EIGA coil is shown as a dashed line in each of Figures 7 to 10.

[0048] The electrode 40 is a rod-shaped electrode made of metal or a metal alloy, including a lower tip 42. The electrode 40 extends into the EIGA coil 10 in the region of the lower tip 42 and is partially melted or cut by the EIGA coil 10 to which an AC voltage is applied. The electrode 40 is coaxial with the windings 12A, 12B, and 12C of the EIGA coil 10, i.e., the longitudinal axis A of the electrode 40 coincides with the central axis M of the EIGA coil. During the EIGA process, the electrode 40 can be continuously repositioned along the longitudinal axis A of the electrode 40 toward the inert gas nozzle 50, according to the amount of cutting indicated by arrow P1. Furthermore, during the EIGA process, the electrode 40 is rotatable about the longitudinal axis A of the electrode 40 to ensure uniform cutting indicated by arrow P2.

[0049] The inert gas nozzle 50 is located downstream of the EIGA coil 10 and electrode 40, that is, below the EIGA coil 10 and electrode 40 in the figure. The inert gas nozzle 50 includes an orifice 52, which is also coaxial with the electrode 40 and the windings 12A, 12B, and 12C of the EIGA coil 10. In other words, the longitudinal axis A of the electrode 40 and the central axis M of the EIGA coil 10 extend precisely through the center of the orifice 52 of the inert gas nozzle 50.

[0050] As shown in Figure 7, the winding 12A is at the same minimum distance h from the electrode 40 at each position of the winding 12A. l ,h rThis is because the electrode 40 and the EIGA coil 10 are coaxially aligned, and the windings 12A, 12B, and 12C extend in planes perpendicular to the central axis M. The same applies to winding 12B and winding 12C of the EIGA coil 10, which are also shown in Figure 7, but are not labeled with reference numerals for clarity.

[0051] Because the distance from electrode 40 to windings 12A, 12B, and 12C is uniform, an azimuthal symmetric Lorentz force acting on electrode 40 is generated by the EIGA coil 10. The azimuthal symmetric Lorentz force is illustrated by arrows LK1 and LK2 of equal length. The asymmetry caused by the gap can be ignored because the gap width is very small.

[0052] Figure 8 shows the EIGA system 30 in Figure 7 at time point t=n in the later stages of the melting process. At this point, a nearly continuous flow of molten material droplets 44, resulting from the cutting of the electrode 40, is falling or flowing from the electrode 40. Because the Lorentz force generated by the EIGA coil 10 is azimuthally symmetric with respect to the electrode 40, the Lorentz forces acting on the electrode 40 cancel each other out, and therefore, the electrode 40 in the state shown in Figure 8 continues to maintain the orientation according to its initial state. Thus, the electrode 40 remains coaxially aligned with the EIGA coil throughout the EIGA process without being deflected with respect to the central axis M. Therefore, the electrode 40 remains coaxially aligned with the inert gas nozzle 50 during the cutting process. Thus, the molten jet or droplet 40 always falls vertically (along the longitudinal axis A or the central axis M) through the center of the orifice 52 of the inert gas nozzle 50, and therefore does not come into contact with the wall of the inert gas nozzle 50 or the windings 12A, 12B, 12C of the EIGA coil 10. This improves process reliability and reduces potential contamination or damage to the EIGA system 30.

[0053] The droplets 44 that fall through the inert gas nozzle 50 are atomized by the inert gas nozzle 50 and then solidified in the atomization tower downstream. As a result, the solidified droplets form spherical fine powder, which is collected and stored in a vacuum-sealed container.

[0054] The advantages of the EIGA coil 10 according to the present invention over the prior art are further evident from the considerations in Figures 9 and 10 (showing the prior art EIGA system 70 in the operating state shown in Figures 7 and 8).

[0055] The prior art EIGA system 70 includes a helical EIGA coil 72, an electrode 74, and an inert gas nozzle 76. In the initial state t=0 shown in Figure 9, the EIGA coil 72, the electrode 74, and the inert gas nozzle 76 are coaxially aligned with each other. That is, the central axis V of the EIGA coil 72 is aligned in a straight line with the longitudinal axis W of the electrode 74, which extends through the center of the inert gas nozzle 76.

[0056] Unlike the arrangement according to the present invention, the windings of the prior art EIGA coil 72 have a different distance from the electrode 74 due to the helical structure of the EIGA coil 72. This is the distance h o ,h p This is illustrated by the following: Different distances of the winding from electrode 74 result in strong Lorentz forces acting differently on electrode 74, i.e., azimuthal asymmetry of the Lorentz force. This is shown in Figures 9 and 10 by arrows LK3 and LK4 of different lengths.

[0057] Due to the aforementioned azimuthal asymmetry of the Lorentz force acting on electrode 74, electrode 74 (more precisely, the longitudinal axis W of electrode 74) is deflected by an angle α. This can be seen in Figure 10. Figure 10 shows the EIGA system 70 in Figure 9 at time t=n in the latter half of the melting process.

[0058] In the illustrated state, droplets 78 of the molten material forming the molten jet fall vertically from the electrode 74, which is deflected by an angle α, toward the inert gas nozzle 76. Due to this deflection, the droplets 78 or the molten jet do not fall through the center of the orifice of the inert gas nozzle 76, but are offset from the central axis V. As a result, the droplets 78 may fall onto the edge of the inert gas nozzle 76, where they may solidify and completely or partially block the orifice of the inert gas nozzle 76. This undesirable effect can be further amplified by the rotation of the electrode 74 that generally occurs. In addition, the deflection of the electrode 74 may cause the droplets 78 or the electrode 74 itself to come into contact with the windings of the EIGA coil 72, which could result in a short circuit and damage to the EIGA system 70.

[0059] These drawbacks can be effectively reduced by the EIGA coil according to the present invention and the azimuthal symmetric Lorentz force acting on the electrodes that may be generated by the EIGA coil. [Explanation of Symbols]

[0060] 10 EIGA Coil 70 EIGA System (Prior Technology) 12A, 12B, 12C windings 72 EIGA Coil (Advanced Technology) 14A, 14B, 14C gap 74 Electrodes (prior art) First end of windings 16A, 16B, 16C 76. Inert gas nozzle (prior art) 18A, 18B, 18C windings, second end 78 Droplets (prior art) 20AB, 20BC connection part V center axis (prior art) 22A, 22B terminal section W Longitudinal axis 120AB, 120BC connection part α Deflection angle (prior art) 30 EIGA System LK3, LK4 Lorentz force (prior art) 32 Output aperture h o ,h p Distance (prior art) 40 electrodes 42 Electrode tip 44 Droplets 50 Inert Gas Nozzles 52 Orifice M center axis B Width K1,K2 line P center point L1 Maximum inner diameter L3 Minimum inner diameter β span angle P1 Arrow indicating position change operation P2 Arrow indicating rotational motion A Longitudinal axis C Virtual Cone LK1, LK2 Lorentz force h l ,h r distance

Claims

1. An EIGA coil (10) for melting an electrode (40) comprises a plurality of windings (12A, 12B, 12C) arranged coaxially with respect to a central axis (M) and spaced apart from each other in the axial direction. Each of the plurality of windings (12A, 12B, 12C) is formed in the shape of a ring interrupted by a gap (14A, 14B, 14C), and the ring is equidistant from the central axis (M) and extends in a plane perpendicular to the central axis (M). Among the plurality of windings (12A, 12B, 12C), adjacent windings (12A, 12B; 12B, 12C) are connected to each other via connecting parts (20AB, 20BC; 120AB, 120BC). An EIGA coil (10) in which at least one of the plurality of windings (12A, 12B, 12C) has an elliptical, circular, rectangular, or square cross-section in at least a portion thereof.

2. The EIGA coil (10) according to claim 1, wherein at least two of the plurality of windings (12A, 12B, 12C) have different inner diameters (L1, L3).

3. The EIGA coil (10) according to claim 1 or 2, wherein the connecting portion (120AB, 120BC) extends parallel to the central axis (M).

4. The EIGA coil (10) according to any one of claims 1 to 3, wherein the width of the gap (14A, 14B, 14C) is 0.5 mm to 30 mm.

5. The EIGA coil (10) according to any one of claims 1 to 4, wherein the winding (12A) having the largest inner diameter (L1) among the plurality of windings (12A, 12B, 12C) has an inner diameter of 40 mm to 300 mm.

6. The EIGA coil (10) according to any one of claims 1 to 5, wherein the winding (12C) having the smallest inner diameter (L3) among the plurality of windings (12A, 12B, 12C) has an inner diameter of 10 mm to 100 mm.

7. An EIGA coil (10) according to any one of claims 1 to 6, having a cross-sectional shape that differs in terms of shape and / or dimensions.

8. An EIGA coil (10) made from a ceramic-free copper material, according to any one of claims 1 to 7.

9. An EIGA coil (10) according to any one of claims 1 to 8, manufactured using an additive manufacturing process.

10. An apparatus (30) for executing the EIGA method, An EIGA coil (10) according to any one of claims 1 to 9, An electrode (40) is arranged coaxially with the plurality of windings (12A, 12B, 12C), partially extends within the EIGA coil (10), and is displaceable along the longitudinal axis (A) of the electrode (40) relative to the EIGA coil (10) so as to be melted by the EIGA coil (10), An apparatus (30) comprising an electrode (40) and a nozzle (50) arranged coaxially with the plurality of windings (12A, 12B, 12C) for atomizing the fused electrode material (44).

11. A method for producing high-purity metal powder, The steps of displacing the electrode (40) relative to the EIGA coil (10) described in any one of claims 1 to 8, The steps include: generating Lorentz forces (LK1, LK2) that are azimuthally symmetric with respect to the longitudinal axis (A) of the electrode (40), thereby applying an alternating current to the EIGA coil (10) to melt the electrode (40); A method comprising the step of atomizing a fused electrode material (44).

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