Power supply structure for vacuum arc remelting furnace, vacuum arc remelting furnace, and method for producing titanium-based ingot

Abstract

To provide a power supply structure for a vacuum arc remelting furnace capable of preventing an engaging member from becoming difficult to detach from a stub due to deformation of the engaging member.SOLUTION: A power supply structure 5 for a vacuum arc remelting furnace 1 in accordance with the present invention for performing melting production of a titanium-based ingot, includes: a stub 6 attached to a top edge of a consumable electrode 4; and a stinger rod 7 for hanging and supporting the consumable electrode 4 so as to be elevated or lowered in a casting mold 2 by engaging with the stub 6, and capable of supplying power to the consumable electrode 4 through the stub 6, wherein the stub 6 has an engaging receiving part 60, the stinger rod 7 is provided so as to be displaced in a direction of approaching or separating from the engaging receiving part 60, and has a ceramic-made engaging member 70 configured so as to engage the engaging receiving part 60 when displaced in the direction of approaching the engaging receiving part 60.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply structure for a vacuum arc remelting furnace that supplies power from a stinger rod through a stub to a consumable electrode, a vacuum arc remelting furnace, and a method for producing a titanium-based ingot. [Background technology]

[0002] Vacuum Arc Remelting Furnaces (hereinafter referred to as "VAR Furnaces") are used to melt and produce titanium ingots. In a VAR Furnace, an arc is generated under vacuum between the molten metal in a water-cooled copper mold and a consumable electrode.

[0003] The following Patent Documents 1 to 3 disclose a structure for supporting a consumable electrode by suspending it with a stinger rod via a stub attached to the upper end of the consumable electrode, and a structure for supplying power from the stinger rod to the consumable electrode through the stub. In particular, Figure 4 of Patent Document 2 discloses that a recess (engagement receiving portion) is provided at the upper end of the stub, and a ball chuck (engagement member) provided on the stinger rod fits into (engages with) the recess, thereby engaging the stinger rod with the stub. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-128586 [Patent Document 2] Japanese Patent Application Publication No. 2019-059970 [Patent Document 3] Japanese Patent Application Publication No. 2019-061797 Summary of the Invention [Problem to be solved by the invention]

[0005] In the production of titanium-based ingots, substantial currents are applied to the stub and stinger rods repeatedly to heat the melted portion of the consumable electrode and the molten metal in the mold to temperatures above approximately 1700°C.

[0006] Conventionally, a ball chuck or an engaging member that engages with a stub has been made of a high-carbon steel (e.g., SUJ2) because it has excellent strength at high temperatures and is not easily cracked. However, repeated ingot manufacturing can cause deformation of the high-carbon steel engaging member, making it difficult to remove the engaging member from the stub.

[0007] The present invention has been made to solve the above-mentioned problems, and one of its objects is to provide a power supply structure for a vacuum arc remelting furnace, a vacuum arc remelting furnace, and a method for manufacturing a titanium-based ingot that can prevent deformation of the engaging member from making it difficult to remove the engaging member from the stub. [Means for solving the problem]

[0008] The inventors analyzed a high-carbon steel engaging member that had become difficult to remove, i.e., had become deformed. The Vickers hardness of the deformed high-carbon steel engaging member was found to be approximately half that of a new one. Furthermore, magnetite (Fe3O4) was detected on the surface of the deformed high-carbon steel engaging member. Based on these results, the inventors concluded that the high-carbon steel engaging member had been heated and tempered, reducing its hardness and, as a result, becoming more susceptible to deformation. After various investigations into the cause of the high-carbon steel engaging member heating, the inventors hypothesized that, for some reason, poor conductivity occurred in the main current path between the stub and the stinger rod, causing a portion of the current to flow through the high-carbon steel engaging member to the stub, resulting in Joule heat heating the high-carbon steel engaging member.

[0009] Therefore, in order to improve the insulating properties of the engaging member, the engaging member was changed to one made of ceramic, and it was found that this could prevent the engaging member from becoming difficult to remove from the stub due to deformation of the engaging member. Furthermore, although there was concern that ceramics has poor ductility and may cause cracking and fracture, operation was possible without any problems even when the engaging member was changed to one made of ceramic. Based on this finding, the inventors have completed the following invention.

[0010] That is, in one embodiment, the power supply structure for a vacuum arc remelting furnace according to the present invention is a power supply structure for a vacuum arc remelting furnace used to melt and produce titanium-based ingots, and comprises a stub attached to the upper end of a consumable electrode, and a stinger rod that engages with the stub to suspend and support the consumable electrode so that it can be raised and lowered within the mold and can supply power to the consumable electrode through the stub, the stub having an engagement receiving portion, and the stinger rod is displaceable toward and away from the engagement receiving portion and has a ceramic engaging member that is configured to engage with the engagement receiving portion when displaced toward the engagement receiving portion.

[0011] In one embodiment, a vacuum arc remelting furnace according to the present invention includes the above-described power supply structure for a vacuum arc remelting furnace.

[0012] In one embodiment, a method for producing a titanium-based ingot according to the present invention includes melting and producing a titanium-based ingot using the above-mentioned vacuum arc remelting furnace. [Effects of the Invention]

[0013] According to one embodiment of the power supply structure for a vacuum arc remelting furnace, the vacuum arc remelting furnace, and the method for manufacturing a titanium-based ingot of the present invention, the engaging member is made of ceramic, which makes it possible to prevent the engaging member from becoming difficult to remove from the stub due to deformation of the engaging member. [Brief explanation of the drawings]

[0014] [Figure 1]1 is an explanatory view showing a vacuum arc remelting furnace including a power supply structure for a vacuum arc remelting furnace according to a first embodiment of the present invention.

[0023] FIG. [Figure 2] FIG. 2 is a cross-sectional view of the power supply structure of FIG. [Figure 3] 3 is a cross-sectional view of the power supply structure in FIG. 2 with the outer tube pulled up. [Figure 4] FIG. 6 is a cross-sectional view of a power supply structure for a vacuum arc remelting furnace according to a second embodiment of the present invention. [Figure 5] 5 is a cross-sectional view of the power supply structure in a state where the inner tube of FIG. 4 is pulled up. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the spirit of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0016] Embodiment 1 FIG. 1 is an explanatory diagram showing a vacuum arc remelting furnace 1 including a power supply structure 5 for the vacuum arc remelting furnace 1 according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view of the power supply structure 5 of FIG. 1; and FIG. 3 is a cross-sectional view of the power supply structure 5 of FIG. 2 with the outer tube 72 pulled up. FIG. 1 shows a partial cross-section of the configuration. The vacuum arc remelting furnace (hereinafter referred to as "VAR furnace") 1 shown in FIG. 1 is equipment for melting and producing titanium-based ingots. Titanium-based ingots include pure titanium ingots and titanium alloy ingots.

[0017] The VAR furnace 1 may include a mold 2 , a cooling jacket 3 , a consumable electrode 4 and a power supply structure 5 .

[0018] The mold 2 is typically a copper container or crucible. The mold 2 of this embodiment has a cylindrical portion 20 with openings at the top and bottom, and a detachable bottom portion 21 that closes the bottom opening of the cylindrical portion 20.

[0019] The cylindrical portion 20 is a cylindrical member extending in the height direction H of the mold 2. The cylindrical portion 20 may be provided with an upper flange 200U and a lower flange 200L extending radially outward from the outer circumferential surface of the cylindrical portion 20. The upper flange 200U may be disposed at the upper end of the cylindrical portion 20, and the lower flange 200L may be disposed at the lower end of the cylindrical portion 20.

[0020] The inner circumferential surface 201 of the cylindrical portion 20 may include a major inner circumferential surface 201a and a lower inner circumferential surface 201b. The major inner circumferential surface 201a may extend in the height direction H from the upper end of the cylindrical portion 20. The extension length of the major inner circumferential surface 201a in the height direction H of the mold 2 is longer than the extension length of the lower inner circumferential surface 201b. The extension length of the major inner circumferential surface 201a may occupy most of the entire length of the cylindrical portion 20 in the height direction H, and may be 90% or more of the entire length of the cylindrical portion 20. The diameter of the major inner circumferential surface 201a may be uniform in the height direction H of the mold 2. The diameter of the major inner circumferential surface 201a may be simply referred to as the inner diameter of the mold 2. The inner diameter of the mold 2 may be 750 mm or more. The inner diameter of the mold 2 may be 850 mm or more, 1000 mm or more, or 1250 mm or more. The lower inner peripheral surface 201b may extend in the height direction H from the lower end of the cylindrical portion 20. The diameter of the lower inner peripheral surface 201b is wider than the diameter of the main inner peripheral surface 201a. A step 201c extending in the radial direction of the mold 2 is formed between the lower inner peripheral surface 201b and the main inner peripheral surface 201a.

[0021] The bottom portion 21 may have a small diameter portion 210 and a large diameter portion 211 having an outer diameter larger than that of the small diameter portion 210. The small diameter portion 210 may be disposed above the large diameter portion 211. The small diameter portion 210 may be disposed coaxially with the large diameter portion 211. The small diameter portion 210 is inserted into the interior of the cylindrical portion 20 along the lower inner circumferential surface 201b. The tip of the small diameter portion 210 abuts against the step portion 201c, and the upper surface of the large diameter portion 211 abuts against the lower surface of the lower flange 200L. Although not shown, the bottom portion 21 can be attached to the lower part of the cylindrical portion 20 by fastening the large diameter portion 211 to the lower flange 200L with fastening members such as bolts.

[0022] The cooling jacket 3 is attached to the outer periphery of the mold 2. The mold 2 may be cooled by the cooling jacket 3 during the melting and production of the titanium-based ingot. The cooling jacket 3 may be a water-cooled jacket.

[0023] The consumable electrode 4 is suspended and supported within the mold 2 so that it can be raised and lowered. After the mold 2 and consumable electrode 4 are placed within the VAR furnace 1, the VAR furnace 1 is maintained at a vacuum of, for example, approximately 0.1 Pa. With the tip of the suspended consumable electrode 4 placed within the mold 2, an arc is generated from the consumable electrode 4, and the resulting heat melts the consumable electrode 4. The melted consumable electrode 4 accumulates inside the mold 2 as molten metal. As the melting of the consumable electrode 4 progresses, the level of the molten metal rises. The molten metal is gradually solidified within the mold 2 to form an ingot 4a. That is, the ingot 4a is gradually grown from the bottom 21 side upward within the mold 2.

[0024] The melting and production of titanium-based ingots may include a primary melting and at least one secondary melting performed after the primary melting. The consumable electrode 4 used in the primary melting may be a columnar electrode formed by welding together multiple briquettes produced by pressing titanium sponge (and alloy raw materials, if necessary). The consumable electrode 4 used in the secondary melting, which is performed immediately after the primary melting, may be the ingot 4a produced in the primary melting, and in the second or subsequent secondary melting, may be the ingot 4a produced in the previous secondary melting.

[0025] The power supply structure 5 suspends and supports the consumable electrode 4 so that it can be raised and lowered, and also serves to supply power to the consumable electrode 4 when an arc is generated from the consumable electrode 4. The power supply structure 5 has a stub 6 attached to the upper end of the consumable electrode 4, and a stinger rod 7 that engages with the stub 6 to suspend and support the consumable electrode 4 so that it can be raised and lowered within the mold 2, and can supply power to the consumable electrode 4 through the stub 6.

[0026] 2, the stub 6 has an engagement receiving portion 60. The stinger rod 7 is provided so as to be displaceable in a direction toward and away from the engagement receiving portion 60, and has a ceramic engagement member 70 configured to engage with the engagement receiving portion 60 when displaced in a direction toward the engagement receiving portion 60.

[0027] When the engaging member 70 is engaged with the engaging receptacle 60, the stinger rod 7 is engaged with the stub 6. Through this engagement, the stinger rod 7 can suspend and support the consumable electrode 4. As will be described later, the main current path between the stub 6 and the stinger rod 7 is provided separately from the engaging member 70 and the engaging receptacle 60.

[0028] As described above, an arc is generated from the consumable electrode 4, and the resulting heat melts the consumable electrode 4. Therefore, during the production of the ingot 4a, a substantial amount of current is continuously applied to the stub 6 and the stinger rod 7, repeatedly heating the melted portion of the consumable electrode 4 and the molten metal in the mold 2 to temperatures exceeding approximately 1700°C. For this reason, a high-carbon steel (e.g., SUJ2) member was conventionally used as the engaging member 70 because of its high strength and resistance to cracking at high temperatures. However, repeated production of the ingot 4a can cause the high-carbon steel engaging member 70 to deform, making it difficult to remove the engaging member 70 from the stub 6. This slowdown in stub 6 replacement forced changes to the ingot 4a production schedule. Furthermore, there is a risk of an arc occurring between the stub 6 and the stinger rod 7, causing the consumable electrode 4 to fall.

[0029] The inventors analyzed a high-carbon steel engaging member 70 that had become difficult to remove, i.e., had been deformed. They found that the Vickers hardness of the deformed high-carbon steel engaging member 70 was approximately half that of a new one. Furthermore, magnetite (Fe3O4) was detected on the surface of the deformed high-carbon steel engaging member 70. Based on these results, they concluded that the high-carbon steel engaging member 70 had been heated and tempered, reducing its hardness and making it more susceptible to deformation. After extensive investigation into the cause of the high-carbon steel engaging member 70 heating, the inventors hypothesized that, for some reason, poor conductivity occurred in the main current path between the stub 6 and the stinger rod 7, causing current to flow through the high-carbon steel engaging member 70 to the stub 6, resulting in Joule heat heating the high-carbon steel engaging member 70.

[0030] Therefore, in order to improve the insulation of the engaging member 70, the engaging member 70 was changed to one made of ceramic as in the power supply structure 5 of this embodiment, and it was possible to prevent the engaging member 70 from becoming difficult to remove from the stub 6 due to deformation of the engaging member 70. Furthermore, although there was concern that ceramics have poor ductility and may cause cracking and fracture, operation was possible without any problems even when the engaging member 70 was changed to one made of ceramic.

[0031] An engaging member 70 made of ceramic may be understood to have ceramic as its main component. When the mass percentage of ceramic in each engaging member 70 is greater than 50%, it may be understood to have ceramic as its main component. The mass percentage of ceramic in each engaging member 70 is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. For example, the mass percentage of ceramic in each engaging member 70 may be 95% or more. The engaging member 70 may be made of ceramic and unavoidable impurities.

[0032] The ceramics constituting the engaging member 70 may be oxide-based ceramics. Examples of oxide-based ceramics include alumina (aluminum oxide (Al2O3)), magnesia (magnesium oxide (MgO)), silica (silicon dioxide (SiO2)), titania (titanium dioxide (TiO2)), and barium titanate (BaTiO3). It is preferable to use alumina as the ceramics constituting the engaging member 70, as it is inexpensive and has little risk of becoming a source of HDI or LDI.

[0033] The ceramics constituting the engaging member 70 may be other ceramics such as nitride ceramics. An example of nitride ceramics is silicon nitride (Si3N4). However, depending on the type of titanium-based ingot being manufactured, it may be preferable to use the oxide ceramics described above to avoid the inclusion of nitrides.

[0034] As shown in FIGS. 2 and 3 , the engaging member 70 may be spherical. A plurality of spherical engaging members 70 may be arranged in a line in the circumferential direction of the stub 6. The stinger rod 7 has an inner tube 71 and an outer tube 72 arranged on the outer periphery of the inner tube 71. One of the inner tube 71 and the outer tube 72 is provided so as to be displaceable relative to the other. The engaging member 70 may be configured so as to be displaced toward and away from the engagement receiving portion 60 due to the relative displacement of one of the inner tube 71 and the outer tube 72 relative to the other. When one of the inner tube 71 and the outer tube 72 is displaced in a first direction, the engaging member 70 may approach the engagement receiving portion 60. When one of the inner tube 71 and the outer tube 72 is displaced in a second direction opposite to the first direction, the engaging member 70 may be displaced from the engagement receiving portion 60. When the engaging member 70 is displaced in a direction approaching the engaging receiving portion 60, the engaging member 70 engages with the engaging receiving portion 60, and when the engaging member 70 is displaced in a direction away from the engaging receiving portion 60, the engagement between the engaging member 70 and the engaging receiving portion 60 is released. The engaging receiving portion 60 may be a recess into which the spherical engaging member 70 fits.

[0035] In the illustrated embodiment, the outer tube 72 is provided so as to be able to advance and retreat relative to the inner tube 71, and the advance and retreat of the outer tube 72 displaces the engaging member 70 in a direction toward and away from the engagement receiving portion 60. The outer tube 72 may be provided so as to be able to advance and retreat in the extension direction 7a of the stinger rod 7. The extension direction 7a of the stinger rod 7 may be along the height direction H of the mold 2, the up-down direction, or the vertical direction. In the illustrated embodiment, when the outer tube 72 is pulled down as shown in FIG. 2, the engaging member 70 is displaced in a direction toward the engagement receiving portion 60, and when the outer tube 72 is pulled up as shown in FIG. 3, the engaging member 70 is displaced in a direction away from the engagement receiving portion 60.

[0036] As shown in FIG. 1 , the stinger rod 7 may be connected to a driving device 8. The inner tube 71 may be fixedly connected to the driving device 8, and the outer tube 72 may be connected to the driving device 8 so as to be movable back and forth in the extension direction 7a of the stinger rod 7. The driving device 8 may be an air cylinder having a housing and a movable part that is movable back and forth relative to the housing. The inner tube 71 may be fixed to the housing, and the outer tube 72 may be fixed to the movable part. Alternatively, the inner tube 71 may be fixed to a structure separate from the driving device 8.

[0037] 2 and 3, the inner pipe 71 may have an inner pipe main portion 710 and a ball seat pipe 711 attached to the lower part of the inner pipe main portion 710 and supporting a spherical engaging member 70. One or more through holes 711a that communicate between the inside and outside of the ball seat pipe 711 are provided in the peripheral wall of the ball seat pipe 711, and the engaging member 70 may be housed in the through holes 711a.

[0038] The spherical seat tube 711 may have a base portion 711b disposed in the center of the spherical seat tube 711 in the extension direction 7a of the stinger rod 7, an upper cylindrical portion 711c extending upward from the base portion 711b, and a lower cylindrical portion 711d extending downward from the base portion 711b. The outer diameter of the base portion 711b may be larger than the inner diameter of the inner pipe main portion 710, and the lower end surface of the inner pipe main portion 710 may be placed on the upper surface of the base 711b. The upper cylindrical portion 711c has an outer diameter equal to the inner diameter of the inner pipe main portion 710, and may be inserted into the inner pipe main portion 710 from a lower opening of the inner pipe main portion 710 and extend along the inner surface of the inner pipe main portion 710. A through hole 711a in which the engaging member 70 is accommodated may be provided in the lower cylindrical portion 711d. The spherical seat tube 711 may have an annular rib 711e that protrudes radially inward from the inner circumferential surface of the base portion 711b.

[0039] The outer pipe 72 may have an outer pipe main portion 720 and a bushing 721 attached to the inner circumferential surface of the lower portion of the outer pipe main portion 720. The inner diameter of the upper portion of the bushing 721 is smaller than the inner diameter of the lower portion of the bushing 721. As shown in Fig. 2, when the outer pipe 72 is pulled down to a position where the upper portion of the bushing 721 contacts the spherical engaging member 70, the engaging member 70 is displaced in a direction approaching the engaging receptacle 60. As shown in Fig. 3, when the outer pipe 72 is pulled up to a position where the lower portion of the bushing 721 contacts the spherical engaging member 70, the engaging member 70 is displaced in a direction away from the engaging receptacle 60.

[0040] The stub 6 has a stub power receiving portion 61 that is in contact with one of the inner tube 71 and the outer tube 72 to receive power from one of the inner tube 71 and the outer tube 72, and the contact position between the stub 6 and the stinger rod 7 through the stub power receiving portion 61 may be different from the contact position between the stub 6 and the stinger rod 7 through the engaging member 70.

[0041] In the illustrated embodiment, the stub 6 has a stub body 62 and a stub protrusion 63 protruding upward from the upper surface of the stub body 62. The stub body 62 may be a cylindrical body connected to the consumable electrode 4. The stub protrusion 63 may be arranged coaxially with the stub body 62. The maximum outer diameter of the stub protrusion 63 may be smaller than the outer diameter of the stub body 62.

[0042] The stub power receiving portion 61 may be the upper surface of the stub body 62 at the outer peripheral position of the stub protrusion 63. The stub power receiving portion 61 may be in contact with the lower surface of the outer tube 72 to receive power from the outer tube 72. The lower portion of the outer tube 72 may be thicker than the upper portion of the outer tube 72. This increases the contact area between the lower surface of the outer tube 72 and the stub power receiving portion 61. The lower portion of the outer tube 72 that comes into contact with the stub power receiving portion 61 may be a ring body detachably attached to the outer tube main portion 720.

[0043] 2 and 3, the engaging member 70 of the stinger rod 7 may be disposed on the outer periphery of the engaging receiving portion 60 of the stub 6. In other words, the concave stinger rod 7 may be disposed so as to surround the convex stub 6. The stub protrusion 63 may be inserted into the inner tube 71 (spherical seat tube 711), and the engaging receiving portion 60 may be the outer periphery of the stub protrusion 63.

[0044] The stub protrusion 63 may have a head 630 and a neck 631 extending downward from the head 630. The outer diameter of the head 630 may be larger than the outer diameter of a central portion of the neck 631 in the extension direction 7a of the stinger rod 7. The engagement receiving portion 60 may be composed of the head 630 and an upper portion of the neck 631. The upper portion of the neck 631 may have any shape, but may be a concave curved surface when viewed from the side as shown in FIG. 2. The upper portion of the neck 631 may have a radius of curvature equal to the radius of the spherical engagement member 70.

[0045] The stub 6 may be a titanium-based stub. In other words, the stub 6 may be made of metallic titanium or a titanium alloy. This reduces the risk of contamination of the ingot 4a even if the stub 6 melts along with the consumable electrode 4. The metallic titanium or titanium alloy constituting the stub 6 may have the same composition as the ingot 4a to be produced. Metallic titanium may be understood as pure titanium. Pure titanium includes not only strictly pure titanium but also pure titanium of industrially acceptable purity. Examples of titanium alloys include Ti-Al-based alloys such as Ti-6Al-4V, Ti-5Al-1Fe, and Ti-5Al-2Fe. A stub 6 made of metallic titanium or a titanium alloy may be understood to be primarily composed of metallic titanium or a titanium alloy. When the mass ratio of metallic titanium or a titanium alloy in the entire stub 6 or the stub body 62 is greater than 50%, it may be understood to be primarily composed of metallic titanium or a titanium alloy. The mass ratio of metallic titanium or titanium alloy in the entire stub 6 or in the stub body 62 is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. For example, the mass ratio of metallic titanium or titanium alloy in the entire stub 6 or in the stub body 62 may be 95% or more. The stub 6 may be made of metallic titanium or a titanium alloy (particularly a Ti-Al alloy) and inevitable impurities.

[0046] Embodiment 2 Fig. 4 is a cross-sectional view of a power supply structure 5 for a vacuum arc remelting furnace according to a second embodiment of the present invention, and Fig. 5 is a cross-sectional view of the power supply structure 5 in a state in which the inner tube 71 of Fig. 4 is pulled up. In the first embodiment, the engaging member 70 of the stinger rod 7 is disposed on the outer periphery of the engaging receiving portion 60 of the stub 6, but as shown in Figs. 4 and 5, the engaging member 70 of the stinger rod 7 may be disposed on the inner periphery of the engaging receiving portion 60 of the stub 6. Furthermore, in the first embodiment, the concave stinger rod 7 is disposed so as to surround the convex stub 6, but the convex stinger rod 7 may be inserted into the concave stub 6, as shown in Figs. 4 and 5.

[0047] The stub 6 may have a recess 64 recessed from the upper end surface of the stub 6 and a stub power receiving portion 61 located at the bottom of the recess 64. The stub power receiving portion 61 may have a recess on its upper surface. Such a stub power receiving portion 61 is sometimes called a stub socket. The engagement receiving portion 60 may be a recess provided on the inner circumferential surface of the recess 64. The stinger rod 7 may have an inner tube 71 and an outer tube 72 whose outer diameters are smaller than the inner diameter of the recess 64, and a rod plug 73 attached to the tip of the inner tube 71. The tip of the inner tube 71 is tapered. The outer tube 72 may have one or more through holes 72a, and a spherical engagement member 70 may be fitted in the through holes 72a.

[0048] The inner tube 71 may be displaceable relative to the outer tube 72. When the inner tube 71 is pulled down to a position where the rod plug 73 is pressed against the stub power receiving portion 61 as shown in Fig. 4, the outer peripheral surface of the inner tube 71 may press the engaging member 70 of the stinger rod 7 radially outward, thereby engaging the engaging member 70 of the stinger rod 7 with the engaging receiving portion 60 of the stub 6. Furthermore, when the inner tube 71 is pulled up as shown in Fig. 5, the pressing force by the outer peripheral surface of the inner tube 71 may be released, thereby releasing the engagement between the engaging member 70 of the stinger rod 7 and the engaging receiving portion 60 of the stub 6. The other configurations are the same as those of the first embodiment.

[0049] The method for producing a titanium-based ingot according to the embodiment of the present invention includes melting and producing a titanium-based ingot using the VAR furnace 1 of the first and second embodiments.

[0050] In the first and second embodiments, it has been explained that the engaging member 70 is spherical and the engaging receiving portion 60 is a recess into which the spherical engaging member 70 fits, but the engaging member 70 and the engaging receiving portion 60 are not limited to this. For example, the engaging member 70 may be a claw and the engaging receiving portion 60 may be a recess into which the claw catches. Also, the engaging member 70 may be a pin and the engaging receiving portion 60 may be a hole through which the pin is inserted.

[0051] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Example]

[0052] As an example, the inventors repeatedly melted and produced titanium-based ingots in a VAR furnace 1 having a ceramic engaging member 70 as described in embodiment 1. The ceramic constituting the engaging member 70 was alumina. As a comparative example, the inventors also repeatedly melted and produced titanium-based ingots in a VAR furnace 1 having a steel engaging member 70. The steel constituting the engaging member 70 was high-carbon steel (SUJ2).

[0053] In the comparative example using a steel engaging member 70, the engaging member 70 deformed during the 16th melting and production of a titanium-based ingot, necessitating replacement of the engaging member 70. In contrast, in the example using a ceramic engaging member 70, no deformation of the engaging member 70 was observed even during the 470th melting and production of a titanium-based ingot, and the engaging member 70 could continue to be used as is. From this result, it was confirmed that by using a ceramic engaging member 70, it is possible to prevent the engaging member 70 from becoming difficult to remove from the stub 6 due to deformation of the engaging member 70.

[0054] The inventors also prepared a stub 6 made of metallic titanium and a stub 6 made of a titanium alloy (Ti-6Al-4V alloy), and used them together with a ceramic engaging member 70. Whether the stub 6 made of metallic titanium or the titanium alloy was used, as described above, no deformation of the engaging member 70 was observed over a long period of time, and it was confirmed that the ceramic engaging member 70 has a long lifespan.

[0055] The invention described in this specification can also be described as follows. [1] A power supply structure for a vacuum arc remelting furnace for melting and producing titanium-based ingots, a stub attached to the upper end of the consumable electrode; a stinger rod that engages with the stub to suspend and support the consumable electrode in the mold so that the consumable electrode can be raised and lowered, and that can supply power to the consumable electrode through the stub; Equipped with The stub has an engagement receiving portion, The stinger rod is provided so as to be displaceable in a direction toward and away from the engagement receiving portion, and has a ceramic engaging member configured to engage with the engagement receiving portion when displaced in a direction toward the engagement receiving portion. Power supply structure for vacuum arc remelting furnace. [2] The engaging member is spherical, the stinger rod has an inner tube and an outer tube disposed on the outer periphery of the inner tube, one of the inner tube and the outer tube being displaceable relative to the other, The engaging member is configured to be displaced in a direction toward and a direction away from the engaging receiving portion by a relative displacement of one of the inner tube and the outer tube with respect to the other. 2. A power supply structure for a vacuum arc remelting furnace according to claim 1. [3] the stub has a stub power receiving portion that is in contact with one of the inner tube and the outer tube and receives power from the one of the inner tube and the outer tube, a contact position between the stub and the stinger rod through the stub power receiving portion is different from a contact position between the stub and the stinger rod through the engaging member; 3. A power supply structure for a vacuum arc remelting furnace according to claim 2. [4] The ceramic constituting the engaging member is an oxide-based ceramic. 4. A power supply structure for a vacuum arc remelting furnace according to any one of claims 1 to 3. [5] The engaging member of the stinger rod is disposed on the outer periphery of the engaging receiving portion of the stub. 5. A power supply structure for a vacuum arc remelting furnace according to any one of claims 1 to 4. [6] The stub is a titanium-based stub. 6. A power supply structure for a vacuum arc remelting furnace according to any one of claims 1 to 5. [7] A vacuum arc remelting furnace comprising the power supply structure for a vacuum arc remelting furnace according to any one of claims 1 to 6. [8] 8. A method for producing a titanium-based ingot, comprising melting and producing a titanium-based ingot using the vacuum arc remelting furnace according to claim 7. [Explanation of symbols]

[0056] 1: Vacuum arc remelting furnace (VAR furnace) 2: Mold 4:Consumable electrode 4a: Ingot 5: Power supply structure 6: Stub 60: Engagement receiving portion 61: Stub receiving part 7: Stinger Rod 70: Engagement member 71: Inner tube 72:Outer tube

Claims

1. A power supply structure for a vacuum arc remelting furnace for melting and producing titanium-based ingots, a stub attached to the upper end of the consumable electrode; a stinger rod that engages with the stub to suspend and support the consumable electrode in the mold so that the consumable electrode can be raised and lowered, and that can supply power to the consumable electrode through the stub; Equipped with The stub has an engagement receiving portion, The stinger rod is provided so as to be displaceable in a direction toward and away from the engagement receiving portion, and has a ceramic engaging member configured to engage with the engagement receiving portion when displaced in a direction toward the engagement receiving portion. Power supply structure for vacuum arc remelting furnace.

2. The engaging member is spherical, the stinger rod has an inner tube and an outer tube disposed on the outer periphery of the inner tube, one of the inner tube and the outer tube being displaceable relative to the other, The engaging member is configured to be displaced in a direction toward and a direction away from the engaging receiving portion by a relative displacement of one of the inner tube and the outer tube with respect to the other. The power supply structure for a vacuum arc remelting furnace according to claim 1.

3. the stub has a stub power receiving portion that is in contact with one of the inner tube and the outer tube and receives power from the one of the inner tube and the outer tube, a contact position between the stub and the stinger rod through the stub power receiving portion is different from a contact position between the stub and the stinger rod through the engaging member; The power supply structure for a vacuum arc remelting furnace according to claim 2.

4. The ceramic constituting the engaging member is an oxide-based ceramic. The power supply structure for a vacuum arc remelting furnace according to claim 1.

5. The engaging member of the stinger rod is disposed on the outer periphery of the engaging receiving portion of the stub. The power supply structure for a vacuum arc remelting furnace according to claim 1.

6. The stub is a titanium-based stub. The power supply structure for a vacuum arc remelting furnace according to claim 1.

7. A vacuum arc remelting furnace comprising the power supply structure for a vacuum arc remelting furnace according to any one of claims 1 to 6.

8. A method for producing a titanium-based ingot, comprising melting and producing the titanium-based ingot using the vacuum arc remelting furnace according to claim 7.

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