EIGA coil with circular winding

Abstract

The present invention relates to an EIGA coil (10) for partially fusing an electrode (40). The EIGA coil (10) includes a plurality of windings (12A, 12B, 12C) arranged coaxially about a central axis (M), with the windings (12A, 12B, 12C) spaced apart from one another 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), is equidistant from the central axis (M), and extends in a plane perpendicular to the central axis (M). Adjacent windings (12A, 12B; 12B, 12C) of the plurality of windings (12A, 12B, 12C) are connected to one another via respective connection portions (20AB, 20BC; 120AB, 120BC).

Description

[Technical field]

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

[0002] The EIGA method for ceramic-free production of high-purity metal or noble metal powders (e.g. titanium, zirconium, niobium and tantalum alloy powders) is based on the electrode induction melting process. A vertically suspended rotating electrode is continuously fed under vacuum or inert gas atmosphere to a conical induction coil (EIGA coil) placed below the rotating electrode, which partially melts or cuts the material without contact. The rotational movement of the electrode about its own longitudinal axis ensures uniform melting of the electrode. A jet of molten material generated by the partial melting or cutting process then flows through an inert gas nozzle placed below the induction coil (EIGA coil), where the molten jet is atomized or vaporized. The mist of microdroplets then solidifies in a downstream atomization tower, forming a spherical fine powder. The formed powder is collected and accumulated in a vacuum-sealed container.

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

[0004] The conical design of the EIGA coil (induction coil) and the set generator frequency are optimized to melt the electrode and make the melt drip from one end of the electrode. Conventional EIGA coils are in the form of a conical spiral or a conical curve extending in a cone. For this purpose, in fact, the copper tubes forming the windings of the EIGA coil are wound along a predefined form.

[0005] An EIGA method of the above type and an associated EIGA system are disclosed, for example, in US Pat. No. 5,399,323.

[0006] When performing the EIGA process, it can happen in known EIGA systems that the droplets of molten metal melted from the electrode do not fall precisely through the inert gas nozzle. Some of the droplets may not fall precisely, for example, onto the edge or frame of the cold inert gas nozzle, where they may solidify and, under some circumstances, partially or completely clog the nozzle. Also, melted droplets may strike the induction coil and cause a short circuit, thereby interrupting the process flow. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] DE 4102101 A1 Summary of the Invention [Problem to be solved by the invention]

[0008] It is therefore an object of the present invention to overcome the shortcomings of the prior art. In particular, one object of the present invention is to provide an EIGA coil, an apparatus for performing an EIGA method, and a method for producing high purity metal powders that avoid contamination and / or damage to the EIGA system from droplets melting off the electrodes. [Means for solving the problem]

[0009] These objects are achieved by an EIGA coil for fusing electrodes, an apparatus for performing an EIGA process and a method for producing high purity metal powder according to 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] An EIGA coil for partially melting and fusion cutting an electrode according to the invention comprises a plurality of windings arranged coaxially with respect to a central axis of the EIGA coil and axially spaced from one another, the central axis of the EIGA coil extending coaxially with a longitudinal axis of the electrode.

[0011] In the context of the present invention, the term "EIGA coil" refers to an induction coil for an EIGA system or for carrying out an EIGA method, said EIGA coil comprising at least two windings, preferably at least three windings, or may comprise more than three windings.

[0012] According to the invention, each of the plurality of windings is in the form of a ring interrupted by a gap. The EIGA coil therefore comprises a number of rings corresponding to the number of windings, each of which is interrupted by a gap of small width and therefore not closed. More specifically, each of the rings is a ring segment comprising a first end and a second end, an associated gap being 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 invention, since it forms an almost complete ring due to the associated gap being very narrow.

[0013] According to the invention, each of the interrupted rings is equidistant to the central axis and extends in a plane perpendicular to the central axis, which plane is associated with the respective ring. In other words, each of the plurality of windings extends in a respective associated plane perpendicular to the central axis. The planes in which the individual rings or windings extend are therefore parallel to one another. That is to say, the rings or windings are arranged parallel to one another. In operation, the plane in which the individual rings or windings extend is horizontal. It will be understood that the windings or rings are three-dimensional objects, and that the extension of each winding or ring (more precisely a ring torus) in only one plane perpendicular to the central axis means that the three-dimensional object extends according to this plane or with an orientation consistent with this plane. In other words, the extension of each winding or ring in only one plane perpendicular to the central axis means that the horizontal cross-sectional area of ​​the winding or ring forming a (nearly complete) circular ring extends only in this plane.

[0014] Adjacent windings of the plurality of windings are respectively connected to each other by a connection part which may be connected to the adjacent winding in the region of the associated gap, in particular each connection part may connect a second end of one of the plurality of windings to a first end of a winding adjacent to the one of the plurality of windings.

[0015] The EIGA coil may be of an overall conical design. For this, at least two of the windings or annular rings have different internal diameters. In one embodiment, all windings of the EIGA coil may have different internal diameters. Alternatively, some windings may have the same internal diameter and may have different internal diameters compared to further windings of the EIGA coil. In particular, 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, the windings of the EIGA coil that are arranged closer to the direction of the downstream inert gas nozzle have smaller or at most approximately the same internal diameter than the windings that are further from the inert gas nozzle, and the windings closest to the inert gas nozzle have smaller internal diameters than the windings that are furthest from the inert gas nozzle.

[0016] Since each of the windings extends only in an associated plane perpendicular to the central axis, azimuthally symmetric Lorentz forces acting on the electrode can be generated with the EIGA coil according to the invention. These azimuthally symmetric Lorentz forces acting on the electrode are balanced, preventing lateral deflection of the electrode and keeping it coaxial with the central axis of the EIGA coil throughout the EIGA process. This keeps the lower tip of the electrode, partially melted by the EIGA coil, precisely aligned above the center of the inert gas nozzle, thereby ensuring that the generated molten metal jet or droplet always passes through the center without touching the nozzle edge.

[0017] In the helical structure of EIGA coils known in the prior art, opposing winding sections have different distances from the electrode. The inventors of the present invention have therefore realised that the Lorentz forces generated by such EIGA coils acting on the electrode are azimuthally asymmetric and deflect the electrode from its vertical orientation. This results in a deflection angle between the central axis of the EIGA coil and the longitudinal axis of the electrode. The lower tip of the electrode is no longer centrally located above the inert gas nozzle. As a result, droplets melted off from the electrode may strike the edge or frame of the cold inert gas nozzle and solidify, possibly clogging the nozzle partially or completely. The melted off droplets may also strike the induction coil and contaminate or short out the induction coil. Furthermore, the electrode itself may contact and short out the EIGA coil. These adverse effects are further amplified by the continuous rotation of the electrode about its deflected longitudinal axis. These disadvantages can be reduced by the EIGA coil according to the present invention and the Lorentz forces it can generate acting on the electrode azimuthally symmetrically.

[0018] In further embodiments of the EIGA coil, the connections may extend in the plane of the central axis, i.e. in the plane in which the vertical central axis of the EIGA coil lies. For example, the connections may extend parallel to the central axis of the EIGA coil. The connections may extend perpendicular to the plane of the windings. In particular, each of the connections connecting adjacent windings may extend as described above relative to the central axis of the EIGA coil. In the assembled state, the windings may extend, for example, horizontally and / or the connections 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 wide, more preferably 5 mm to 10 mm wide. The gap may be at least 0.5 mm wide, in particular at least 2 mm wide, preferably at least 5 mm wide. In an embodiment, the gap may be 30 mm or less, in particular at most 20 mm wide, preferably at most 10 mm wide. Gap width here means the distance between the first end and the second end of the associated winding or ring. The above ranges of gap width may apply to the gaps 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 azimuthally symmetric, thereby ensuring that a substantial and sufficiently azimuthally symmetric Lorentz force is applied to the electrodes.

[0020] Among the plurality of windings of the EIGA coil, the winding having 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 topmost winding of the EIGA coil, i.e. the winding closest to the hanging part of the electrode, may be selected according to the dimensions of the electrode to be fused. Among the plurality of windings, the winding having the smallest inner diameter may have an inner diameter of 10 mm to 100 mm, preferably 20 mm to 50 mm. The winding having the smallest inner diameter may have an inner diameter of at least 10 mm, preferably at least 20 mm. The winding having 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 having a winding with a relatively large inner diameter may have a relatively large gap width within the above-defined range. Correspondingly, an EIGA coil having a winding with a relatively small inner diameter may have a relatively small gap width within the above-defined range.

[0021] In further embodiments, the EIGA coils may have different cross-sectional shapes and / or dimensions. For example, the EIGA coils may have elliptical, circular, rectangular, square, or other cross-sections. For example, the cross-sectional shapes of the EIGA coils may vary in shape and / or size within the same winding or between different windings.

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

[0023] The EIGA coil may be manufactured using an additive manufacturing process. In particular, the EIGA coil may be manufactured using a 3D printing process, for example, using a selective laser melting process. Alternatively, the EIGA coil may be manufactured using an electron beam melting process, binder jetting, or any other additive manufacturing process. The manufacturing of the EIGA coil according to the 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. Furthermore, the additive manufacturing process makes it possible to form interconnects between adjacent windings that extend perpendicularly to the windings. None of this is possible with conventional EIGA coil manufacturing processes. In conventional EIGA coil manufacturing processes, a copper tube filled with sand is bent to form the windings of the EIGA coil using predefined forms, which greatly limits the formation of the windings.

[0024] Another aspect of the invention relates to an apparatus or EIGA system for performing an EIGA method, the apparatus comprising an EIGA coil of the type described above. The apparatus comprises an electrode of the metal or metal alloy to be fused, arranged coaxially with the plurality of windings, the electrode extending partially within the EIGA coil and displaceable relative to the EIGA coil along the longitudinal axis of the electrode to be fused by the EIGA coil. The electrode is also rotatable about its longitudinal axis. The apparatus further comprises a nozzle or inert gas nozzle for atomizing the fused electrode material, arranged coaxially with the electrode and the plurality of coils.

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

[0026] Another aspect of the present invention relates to an EIGA method for producing high purity metal powders, the method comprising: - displacing an electrode relative to the EIGA coil, thereby introducing said electrode partially inside said EIGA coil; - applying an alternating current to the EIGA coil to partially melt the electrodes by generating a Lorentz force that is azimuthally symmetric about the longitudinal axis of the electrodes; - atomizing the fused electrode material with an inert gas nozzle positioned downstream of said EIGA coil.

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

[0028] The electrode may be rotated about its longitudinal axis during the method.

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

[0030] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying schematic drawings, in which: FIG. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a perspective view of an EIGA coil according to an exemplary embodiment. [Diagram 2] FIG. 2 is a front view of the EIGA coil according to the exemplary embodiment of FIG. 1. [Diagram 3] FIG. 2 is a side view of an EIGA coil according to the exemplary embodiment of FIG. 1. [Figure 4] FIG. 2 is a schematic top view of an EIGA coil according to the exemplary embodiment of FIG. 1. [Diagram 5] 13 is a schematic diagram of a connection of an EIGA coil according to a further exemplary embodiment. FIG. [Figure 6] 2 is a schematic cross-sectional view of an EIGA coil according to the exemplary embodiment of FIG. 1; [Figure 7] 1 is a schematic cross-sectional view of an EIGA system according to an exemplary embodiment in an initial state. [Figure 8] 8 is a schematic cross-sectional view of the EIGA system of FIG. 7 in a further state during operation. [Figure 9] FIG. 1 is a schematic cross-sectional view of a prior art EIGA system in its initial state. [Figure 10] FIG. 10 is a schematic cross-sectional view of the EIGA system of FIG. 9 in a deflected state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The same reference numbers in the figures indicate the same, similar functions and / or similar elements.

[0033] 1-3 show an exemplary embodiment of an EIGA coil 10 according to the present invention for partially melting and fusing an electrode in a perspective view (FIG. 1), a front view (FIG. 2), and a side view (FIG. 3), and FIG. 4 is a schematic top view of the EIGA coil 10.

[0034] EIGA coil 10, which is an induction coil for an EIGA system for performing the EIGA method, includes multiple windings 12A, 12B, and 12C. In the illustrated exemplary embodiment, 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. The windings 12A, 12B, and 12C are spaced apart from each other in the axial direction when viewed from the direction of the central axis M. The windings 12A, 12B, and 12C each have a different inner diameter and outer diameter, with the winding 12A at the top in FIGS. 1 to 3 having the largest inner diameter and outer diameter among the three windings 12A, 12B, and 12C, and the winding 12C at the bottom in FIGS. 1 to 3 having the smallest inner diameter and outer diameter among the three windings 12A, 12B, and 12C. The inner and outer diameters of the middle winding 12B, which is disposed between the top winding 12A and the bottom winding 12C, are between the inner and outer diameters of the top winding 12A and the bottom winding 12C, respectively. Thus, the EIGA coil 10 is generally cone-shaped. In operation, the EIGA coil 10 is disposed such that the top winding 12A, which has the largest inner and outer diameters, faces the electrode suspension (not shown), and the bottom winding 12B, which has the smallest inner and outer diameters, faces the inert gas nozzle (not shown). Exemplary inner diameters are shown quantified with respect to FIG. 6.

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

[0037] 1-3, and particularly FIG. 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] Moreover, as shown in Figures 1-4, each of the windings 12A, 12B, 12C, or each of the rings 12A, 12B, 12C, is oriented only in the horizontal direction. That is, each of the windings 12A, 12B, 12C extends only in a plane perpendicular to the central axis M, which plane is associated with the respective winding 12A, 12B, 12C. More specifically, the windings extend in the same direction as the associated plane. The windings 12A, 12B, 12C are aligned parallel to one another. This represents a significant difference from prior art EIGA coils, which have helical windings that extend helically in all three spatial directions.

[0039] Since in the EIGA coil 10 according to the invention, each of the windings 12A, 12B, 12C is aligned according to an associated plane perpendicular to the central axis M, and each of the windings or rings 12A, 12B, 12C is equidistant to the central axis M, it is possible to generate azimuthally symmetric Lorentz forces acting on the electrodes with the EIGA coil 10 according to the invention. The resulting effects and advantages are explained in more detail below in conjunction with 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 connections 20AB, 20BC, respectively. More specifically, the connection 20AB connects the second end 18A of the winding 12A to the first end 16B of the winding 12B. Thus, the connection 20BC connects the second end 18B of the winding 12B to the first end 16C of the winding 12C. In the exemplary embodiment of FIG. 1, the connections 20AB, 20BC have an arrangement extending transversely to the central axis M, but in other exemplary embodiments, different orientations of the connections may be preferably provided, which will be described in more detail in connection with FIG. 5.

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

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

[0043] 1, the connections 20AB, 20BC have a different cross-sectional shape than the windings 12A, 12B, 12C. However, in further exemplary embodiments, the windings and the connections may have the same cross-sectional shape.

[0044] 5 is a schematic diagram of an enlarged cross section of an EIGA coil according to a further exemplary embodiment. The enlarged cross section shows a particular design of the connections 120AB, 120BC, according to which the connections 120AB, 120BC each extend in the plane of the central axis M and are therefore essentially perpendicular to the windings 12A, 12B, 12C. The windings 12A, 12B, 12C therefore extend horizontally in operation and in the illustrated depiction, while the connections 120AB, 120BC extend vertically. This structural design of the connections 120AB, 120BC in the direction perpendicular to the windings 12A, 12B, 12C allows the provision of an EIGA coil with gaps 14A, 14B, 14C of a particularly small width B. By making the width B of the gaps 14A, 14B, 14C particularly small, the windings 12A, 12B, 12C can be formed in the form of only slightly interrupted and therefore nearly complete rings, which increases the symmetry of the overall arrangement and further improves the application of azimuthally symmetric Lorentz forces to the electrodes.

[0045] 6 is a schematic cross-sectional view of an EIGA coil 10 according to the above exemplary embodiment. In the EIGA coil 10 of FIG. 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 general appearance due to the configuration shown (windings 12A, 12B, 12C with different diameters arranged coaxially with respect to each other and spaced apart from each other in the axial direction). Two lines K1 and K2 are symmetrical about a central axis M and extend through a central point P of a vertical cross section of the windings 12A, 12B, 12C, respectively, over an angle β. The angle β is between 30 degrees and 180 degrees, preferably 90 degrees. The central point P through which the line K1 passes is located on the opposite side of the central axis M to the central point P through which the line K2 passes.

[0047] Figure 7 is a schematic cross-sectional view of an EIGA system 30 for performing the EIGA method, the EIGA system 30 comprising 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 an initial state at time t = 0, which corresponds to the initial power-up of the EIGA coil 10. To better illustrate the orientation of the components of the EIGA system relative to one another, an imaginary cone C formed by the windings of the EIGA coil is shown in dashed lines in each of Figures 7-10.

[0048] The electrode 40 is a rod-shaped electrode made of metal or metal alloy and includes a lower tip 42. The electrode 40 extends into the interior of the EIGA coil 10 in the region of the lower tip 42 and is partially melted or fused by the EIGA coil 10 to which an alternating voltage is applied. The electrode 40 is arranged coaxially with the windings 12A, 12B, 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. The electrode 40 can be continuously repositioned during the EIGA process along the longitudinal axis A of the electrode 40 in the direction of the inert gas nozzle 50 according to the amount of fusion indicated by the arrow P1. Furthermore, the electrode 40 can be rotated about the longitudinal axis A of the electrode 40 to ensure uniform fusion indicated by the arrow P2 during the EIGA process.

[0049] The inert gas nozzle 50 is disposed downstream of the EIGA coil 10 and the electrode 40, i.e., below the EIGA coil 10 and the electrode 40 as shown. The inert gas nozzle 50 includes an orifice 52, which is also coaxial with the electrode 40 and the windings 12A, 12B, 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 exactly through the center of the orifice 52 of the inert gas nozzle 50.

[0050] As can be seen in FIG. 7, the winding 12A has the same minimum distance h from the electrode 40 at each location on the winding 12A. l ,h rThis is due to the coaxial alignment of electrode 40 and EIGA coil 10, and the fact that windings 12A, 12B, and 12C each extend in a plane perpendicular to central axis M. The same is true for winding 12B and also for winding 12C of EIGA coil 10, which are also shown in FIG. 7 but are not numbered for the sake of clarity.

[0051] Due to the uniform distance from electrode 40 to windings 12A, 12B, 12C, an azimuthally symmetric Lorentz force acting on electrode 40 is generated by EIGA coil 10. The azimuthally symmetric Lorentz forces are illustrated by the equal length arrows LK1, LK2. The asymmetry caused by the gap is negligible because the gap width is very small.

[0052] FIG. 8 shows the EIGA system 30 of FIG. 7 at a later time t=n in the melting process. At this time, a substantially continuous molten stream of melted material droplets 44 from the electrode 40 falls or flows from the electrode 40. Because the Lorentz forces generated by the EIGA coil 10 are azimuthally symmetric about 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 FIG. 8 continues to maintain its orientation according to the 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. Thus, the electrode 40 also remains coaxially aligned with the inert gas nozzle 50 during the melting process. Thus, the molten jet or droplets 40 always fall vertically (along the longitudinal axis A or central axis M) through the center of the orifice 52 of the inert gas nozzle 50 and therefore do not contact the walls of the inert gas nozzle 50 or the windings 12A, 12B, 12C of the EIGA coil 10. This improves process reliability and reduces possible 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 downstream atomization tower, whereupon the solidified droplets form spherical fine powder that is collected and accumulated in a vacuum sealed container.

[0054] The advantages of the EIGA coil 10 according to the present invention over the prior art are further apparent from a consideration of FIGS. 9 and 10, which show a prior art EIGA system 70 in the operational configuration shown in FIGS.

[0055] 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 one another, i.e., the central axis V of the EIGA coil 72 is aligned 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 different distances from the electrodes 74 due to the helical structure of the EIGA coil 72. This is due to the distance h o ,h p Different distances of the windings from the electrode 74 cause the strong Lorentz force to act differently on the electrode 74, i.e. resulting in an azimuthal asymmetry of the Lorentz force. This is illustrated in Figures 9 and 10 by the arrows LK3 and LK4 of different lengths.

[0057] The above-mentioned azimuthal asymmetry of the Lorentz force acting on the electrode 74 causes the electrode 74 (or more precisely the longitudinal axis W of the electrode 74) to be deflected by an angle α, which can be seen in Figure 10, which shows the EIGA system 70 of Figure 9 at a later time t=n during the melting process.

[0058] In the illustrated situation, droplets 78 of fused material forming a molten jet fall vertically from the deflected electrode 74 at an angle α toward the inert gas nozzle 76. This deflection causes the droplets 78 or molten jet to fall off of the center of the orifice of the inert gas nozzle 76, but are offset relative to the central axis V. This can cause the droplets 78 to fall onto the edge of the inert gas nozzle 76, where they can solidify and completely or partially block the orifice of the inert gas nozzle 76. This adverse effect can be further amplified by the rotation of the electrode 74, which typically occurs. The deflection of the electrode 74 can also cause the droplets 78 or the electrode 74 itself to come into contact with the windings of the EIGA coil 72, which can 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 invention and the azimuthally symmetric Lorentz forces acting on the electrodes that can be generated by the EIGA coil. [Explanation of symbols]

[0060] 10 EIGA coil 70 EIGA System (Prior Art) 12A, 12B, 12C windings 72 EIGA coil (prior art) 14A, 14B, 14C Gap 74 Electrodes (prior art) 16A, 16B, 16C First ends of windings 76 Inert Gas Nozzle (Prior Art) 18A, 18B, 18C Second ends of windings 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 Nozzle 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 Position change action arrow P2 Rotational movement arrow A Longitudinal axis C Virtual cone LK1, LK2 Lorentz force h l ,h r distance

Claims

1. An EIGA coil (10) for fusing an electrode (40), comprising a plurality of windings (12A, 12B, 12C) arranged coaxially with respect to a central axis (M) and spaced apart from one another in the axial direction; each of said plurality of windings (12A, 12B, 12C) is formed in the shape of a ring interrupted by a gap (14A, 14B, 14C), said ring being equidistant to said central axis (M) and extending in a plane perpendicular to said central axis (M); Adjacent windings (12A, 12B; 12B, 12C) of the plurality of windings (12A, 12B, 12C) are connected to each other via respective connection parts (20AB, 20BC; 120AB, 120BC), The EIGA coil (10), wherein the connection portions (120AB, 120BC) extend parallel to the central axis (M).

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

3. The EIGA coil (10) of claim 1 or 2, wherein the width of the gap (14A, 14B, 14C) is between 0.5 mm and 30 mm.

4. The EIGA coil (10) according to any one of claims 1 to 3, 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.

5. The EIGA coil (10) according to any one of claims 1 to 4, 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.

6. 6. The EIGA coil (10) of any one of claims 1 to 5, having cross-sectional shapes that vary in shape and / or size.

7. The EIGA coil (10) of any one of claims 1 to 6, made of a ceramic-free copper material.

8. An apparatus (30) for carrying out the EIGA method, comprising: An EIGA coil (10) according to any one of claims 1 to 7; an electrode (40) arranged coaxially with the plurality of windings (12A, 12B, 12C) and extending partially within the EIGA coil (10) and displaceable along a longitudinal axis (A) of the electrode (40) relative to the EIGA coil (10) so as to be fused by the EIGA coil (10); and a nozzle (50) disposed coaxially with said electrode (40) and said plurality of windings (12A, 12B, 12C) for atomizing fused electrode material (44).

9. A method for producing a high purity metal powder, comprising the steps of: displacing an electrode (40) relative to the EIGA coil (10) of any one of claims 1 to 7; applying an alternating current to the EIGA coil (10) to generate Lorentz forces (LK1, LK2) that are azimuthally symmetric about a longitudinal axis (A) of the electrode (40) to melt the electrode (40); and atomizing the fused electrode material (44).

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