Crucible furnace

Abstract

In a crucible furnace that generates heat by energization, a crucible furnace is provided that can reduce the occurrence of problems due to high heat in the upper electrode portion and its peripheral portion. 【Solution means】The crucible furnace 1 includes a crucible 2 that generates heat by energization, a lower electrode portion 55 electrically connected to the lower portion of the crucible 2, an upper electrode portion 51 electrically connected to the upper portion of the crucible 2, a heat insulator that covers the upper portion of the crucible 2, and an upper cooling portion 72 that cools the upper electrode portion 51.

Description

Technical Field

[0001] The present invention relates to a crucible furnace, and more particularly to a crucible furnace having a crucible that generates heat by energization.

Background Art

[0002] Patent Document 1 describes a conventional crucible furnace. The crucible furnace described in Patent Document 1 includes a crucible that generates heat by energization, a crucible stand that supports the crucible, an electrode (lower electrode) electrically connected to the crucible stand, and an electrode (upper electrode) electrically connected to the upper part of the crucible. The crucible generates heat by applying a voltage between the lower electrode and the upper electrode, and thereby can melt the metal in the crucible or hold the molten metal.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, a flange portion is formed at the upper end portion of the crucible. Since the flange portion has an extension, heat is easily radiated from the flange portion. Therefore, in order to prevent heat radiation from the flange portion, it is common to cover the flange portion including the flange portion with a heat insulator.

[0005] However, by being covered with a heat insulator, the flange portion and the upper electrode become hot, so there is a possibility that problems such as deformation or melting of the parts of the upper electrode and its peripheral portions due to heat may occur.

[0006] In view of the above circumstances, the present invention is made, and an object of the present invention is to provide a crucible furnace capable of reducing the occurrence of problems due to high heat in the upper electrode portion and its peripheral portions in a crucible furnace that generates heat by energization.

Means for Solving the Problems

[0007] One aspect of the crucible furnace according to the present invention includes a crucible that generates heat by energization, a lower electrode portion electrically connected to the lower portion of the crucible, an upper electrode portion electrically connected to the upper portion of the crucible, a heat insulating material that covers the outer surface of the crucible, and an upper cooling portion that cools the upper electrode portion.

Advantages of the Invention

[0008] The crucible furnace according to the above aspect of the present invention has an advantage that in a crucible furnace that generates heat by energization, it is possible to reduce the occurrence of problems due to high heat in the upper electrode portion and its peripheral portion.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0010] <Embodiment> Hereinafter, the crucible furnace 1 according to the present embodiment will be described with reference to the accompanying drawings. The crucible furnace 1 is a furnace that melts metal and holds the melted metal (hereinafter sometimes referred to as "molten metal"). The crucible furnace 1 according to the present embodiment is an electric furnace that heats the crucible 2 by applying a voltage thereto, thereby melting and holding the metal. The metal melted by the crucible furnace 1 is not particularly limited, and examples thereof include aluminum, copper, copper alloy, zinc, and the like. As shown in FIG. 1, the crucible furnace 1 includes a crucible 2, a crucible stand 3, a frame body 4, an electrode portion 5, a heat insulating material 6, and a cooling portion 7.

[0011] Hereinafter, for convenience of explanation, the description will be based on the crucible furnace 1 placed on the installation surface G1 forming a horizontal plane. Also, the direction perpendicular to the horizontal plane is defined as the "vertical direction". However, the definition of these directions does not specify the usage mode of the crucible furnace 1 according to the present invention.

[0012] (Crucible 2) The crucible 2 is a container capable of containing a metal such as aluminum. The crucible 2 is made of a conductive material and generates heat when energized. The conductive material constituting the crucible 2 is not particularly limited, and examples thereof include carbon (graphite, carbon black, etc.), silicon carbide, mullite, and the like, and a mixed material containing these may also be mentioned. However, it is preferable to use a graphite-silicon carbide crucible mainly composed of graphite and silicon carbide for the crucible 2.

[0013] The electrical resistivity value of the crucible 2 is not particularly limited, but for example, 5×10 -3 [Ω·cm] or more and 1000×10 -3 [Ω·cm] or less, preferably 10×10 -3 [Ω·cm] or more and 500×10 -3 [Ω·cm] or less, more preferably 100×10 -3 [Ω·cm] or more and 300×10 -3 [Ω·cm] or less, still more preferably 150×10 -3 [Ω·cm] or more and 250×10 -3 [Ω·cm] or less, most preferably 200×10 -3It is set around [[Ω·cm]].

[0014] The size of the crucible 2 is not particularly limited. For example, it is preferable that the crucible 2 is formed to have a capacity capable of accommodating aluminum of 100 kg or more and 600 kg or less.

[0015] The thickness of the crucible 2 is not particularly limited and is appropriately set according to the size of the crucible 2. For example, it is set to 5 mm or more and 100 mm or less.

[0016] The crucible 2 may have a uniform thickness and the same material in the vertical direction, or the thickness and material may change in the vertical direction. For example, the crucible 2 can change the thickness and material of the upper part on the flange part 22 side from those of the lower part on the bottom side of the crucible body 21 (by making the thickness of the upper part larger than that of the lower part in terms of thickness), so that the electrical resistivity of the upper part is made smaller than that of the lower part, and the upper part can be made less likely to generate heat by energization. In this case, the electrical resistivity of the lower part of the crucible 2 (the part where the metal such as aluminum accommodated in the crucible 2 mainly contacts) is set within the above-mentioned numerical range. The height of the upper part of the crucible 2 is not particularly limited, but for example, it is preferably 0.05 or more and 0.3 or less in terms of the ratio to the overall height of the crucible 2.

[0017] As shown in FIG. 1, the crucible 2 includes a crucible body 21 and a flange part 22. The crucible body 21 and the flange part 22 are integrally formed.

[0018] The crucible body 21 is a part that constitutes the main body of the crucible 2. The crucible body 21 is formed in a container shape having an opening surface on the upper surface. Also, the crucible body 21 is formed in a substantially circular shape in plan view. The inner surface of the crucible body 21 is formed in a mortar shape so as to have a smaller diameter as it goes downward. However, in the present invention, the shape of the crucible body 21 is not particularly limited, and for example, it may be tapered, cylindrical, rectangular tubular, or the like.

[0019] The flange portion 22 reinforces the upper end portion of the crucible body 21. The flange portion 22 protrudes outward at the upper end portion of the crucible body 21. The flange portion 22 is formed along the entire length of the opening peripheral edge of the upper end portion of the crucible body 21. Here, the "outward" means the outer side (opposite to the center) with respect to the peripheral wall of the crucible body 21 in the radial direction of the crucible body 21.

[0020] The flange portion 22 includes a tip portion 221 and a base end portion 222. The base end portion 222 is the portion connected to the crucible body 21, and is formed such that the thickness dimension becomes thinner as it advances outward in the radial direction of the crucible 2. The tip portion 221 is the portion provided at the outer end in the radial direction of the base end portion 222. The tip portion 221 is formed with the same thickness dimension along the radial direction. However, in the flange portion 22 according to the present invention, the base end portion 222 and the tip portion 221 may be formed with the same thickness dimension (the tip portion 221 and the base end portion 222 may be connected without a clear boundary). The portion of the lower surface of the flange portion 22 corresponding to the base end portion 222 is inclined with respect to the horizontal plane, but the upper surface is formed in a planar shape over the entire surface.

[0021] When the flange portion 22 is provided on the crucible body 21, while the strength of the upper end portion of the crucible body 21 is increased, the surface area of the crucible 2 is increased by the flange portion 22, and the heat dissipation amount is increased. As a result, the temperature of the molten metal in the crucible 2 may decrease. Therefore, in order to prevent the temperature of the molten metal in the crucible 2 from decreasing, it is preferable to cover the flange portion 22 with a heat insulator (not shown). There is no particular limitation on the heat insulator, and examples thereof include a blanket, a silica board, an aerogel, a coated heat insulating material, and the like. The heat insulator may cover only the flange portion 22, or may cover not only the flange portion 22 but also the upper electrode portion 51.

[0022] (Crucible stand) The crucible table 3 supports the crucible 2. The crucible table 3 is formed in a rectangular parallelepiped shape as shown in FIG. 2, but may have various shapes such as a cylindrical shape, a polygonal column shape, a frustum of a cone shape, etc. The crucible table 3 is formed of a material having heat resistance. Examples of the material of the crucible table 3 include alumina (Al2O3), silica (SiO2), silicon carbide (SiC), a graphite-containing material, and the like.

[0023] As shown in FIG. 3, the crucible table 3 has a mounting surface 31 and an electrode connection portion 32. The mounting surface 31 is a surface on which the crucible 2 is placed and is formed on the upper surface of the crucible table 3. The mounting surface 31 is configured to be directly electrically connected to the crucible 2. In the present embodiment, the mounting surface 31 is a flat surface, but in the present invention, the shape is not particularly limited, and it may be curved in a spherical shape along the bottom surface of the crucible 2, or may be composed of protruding surfaces of a plurality of convex portions, or the bottom surface of the crucible 2 may be convex and formed in a concave shape to match the convex bottom surface.

[0024] As used in this specification, "directly" electrically connected means that in addition to the direct contact between one contact point and the other contact point, the one contact point and the other contact point are electrically connected in a state where a conductive member such as conductive grease, conductive packing, or a conductive sheet is interposed therebetween, but does not include interposing a member that can become an electrical resistance of other components or the like. Also, when the one contact point and the other contact point are electrically connected, it may be referred to as "electrically connected".

[0025] The electrode connection portion 32 is a portion of the crucible table 3 where the lower electrode portion 55 of the electrode portion 5 is electrically connected. The electrode connection portion 32 according to the present embodiment is the lower surface of the crucible table 3. However, the electrode connection portion 32 according to the present invention may be the side surface of the crucible table 3, or may be configured by a hole formed in the side surface or the bottom surface of the crucible table 3 into which the lower electrode portion 55 is inserted. Further, a protruding piece may be formed so as to protrude from the crucible table 3, and the protruding piece may be used as the electrode connection portion 32, or it may be configured by a connector capable of connecting the lower electrode portion 55.

[0026] (Electrode portion 5) The electrode part 5 is a component that passes the current supplied from the power supply device to the crucible 2. As shown in FIG. 1, the crucible furnace 1 according to the present embodiment includes, as the electrode part 5, the above-described lower electrode part 55 and a plurality of upper electrode parts 51.

[0027] (Lower electrode part 55) The lower electrode part 55 is an electrode part that is electrically connected to the lower part of the crucible 2. In the present embodiment, the lower electrode part 55 is directly connected to the electrode connection part 32 of the crucible table 3 and is electrically connected to the lower part of the crucible 2 via the crucible table 3. In the present embodiment, the lower electrode part 55 applies a current to the bottom surface of the crucible 2, but in the present invention, a current may be applied to a position (for example, the skirt part) deviated from the bottom surface.

[0028] As shown in FIG. 3, the lower electrode part 55 includes a first electrode 551 extending along a horizontal plane and a second electrode 552 rising from the first electrode 551. The first electrode 551 is an electrode having a contact point that is directly electrically connected to the electrode connection part 32. The first electrode 551 is composed of a bus bar having a longitudinal direction extending linearly in one direction. The first electrode 551 has a first contact point 5511 connected to the electrode connection part 32 and a second contact point 5512 connected to the second electrode 552. The first electrode 551 is arranged along a horizontal plane, the end having the first contact point 5511 is arranged below the crucible 2, and the other end (second contact point 5512) protrudes from the frame body 4.

[0029] The second electrode 552 is connected to the second contact point 5512 of the first electrode 551. The second electrode 552 is composed of a bus bar extending along the vertical direction. The upper end part of the second electrode 552 is connected to an electrode (not shown). Note that the shape of the second electrode 552 is appropriately changed according to the environment of the crucible furnace 1. For example, it may extend parallel to the first electrode 551 or may be inclined with respect to the horizontal plane. Further, the first electrode 551 and the second electrode 552 do not have to be composed of bus bars, and for example, they may be composed of wire harnesses.

[0030] (Upper electrode part 51) As shown in FIG. 1, the upper electrode part 51 is an electrode part 5 that is electrically connected to a part above the part connected to the lower electrode part 55 in the crucible 2. The connection part of the upper electrode part 51 may be at a position above the liquid level of the molten metal. Here, it is connected to the flange part 22. As shown in FIG. 4, each upper electrode part 51 includes a connector body 52, a pressing part 53, and a plurality of elastic bodies 54.

[0031] The connector body 52 is a component that constitutes the main body of the upper electrode part 51. The connector body 52 includes a fitting part 521 formed in a substantially C-shaped cross section and a terminal part 525 to which an electric cable is electrically connected. The fitting part 521 and the terminal part 525 are integrally formed.

[0032] The fitting part 521 includes an upper plate part 522 facing the upper surface of the flange part 22, a lower plate part 523 facing the lower surface of the tip part 221 of the flange part 22, and a vertical plate part 524 connecting the upper plate part 522 and the lower plate part 523. In this embodiment, the terminal part 525 is integrally connected to the upper plate part 522, but it may be connected to at least one of the upper plate part 522, the lower plate part 523, and the vertical plate part 524.

[0033] The upper plate part 522 is directly connected to the upper surface of the flange part 22. Here, the upper plate part 522 is connected to the upper surface of the flange part 22 via a conductive packing P1. Examples of the conductive packing P1 include carbon packing, refractory rubber packing, flame-retardant silicone rubber packing, and various metal packings.

[0034] The lower plate part 523 is positioned with a gap from the lower surface of the tip part 221 of the flange part 22. The lower plate part 523 is fixed to the upper plate part 522 by the vertical plate part 524. A pressing part 53 that can move in the vertical direction is attached to the lower plate part 523.

[0035] The pressing portion 53 has a portion that directly presses against the lower surface of the tip portion 221 of the flange portion 22. The pressing portion 53 has a pair of guides extending in the vertical direction. An elastic body 54 (here, a torsion coil spring) is attached to each guide, and the elastic body 54 constantly presses the pressing portion 53 against the flange portion 22.

[0036] Each upper electrode portion 51 is partially attached to the flange portion 22 in a plan view. A plurality (here, three) of upper electrode portions 51 are assigned such that the angles (central angles) formed by the straight lines connecting the center and the flange portion 22 are equal (here, the central angle is 120°) as shown in FIG. 2.

[0037] Here, as described above, in order to prevent heat dissipation by the flange portion 22, the flange portion 22 is covered with a heat insulator. By being covered with the heat insulator, the flange portion 22 becomes hot, so there is a possibility that problems may occur in the upper electrode portion 51 and the conductive packing P1 that come into contact with the flange portion 22. When the upper electrode portion 51 becomes hot, the components and the flange portion 22 may deform, and when the conductive packing P1 deteriorates, arc discharge may occur between the flange portion 22 and the upper electrode portion 51, resulting in problems such as melting of the peripheral portion.

[0038] Therefore, in order to suppress the deterioration of the peripheral portion of the upper electrode portion 51 and the conductive packing P1 while maintaining the temperature of the upper electrode portion 51, the crucible furnace 1 according to the present embodiment includes an upper cooling portion 72 as shown in FIG. 4. By cooling the upper electrode portion 51, the upper cooling portion 72 can suppress the peripheral portion of the upper electrode portion 51 and the conductive packing P1 from becoming hot, and since the upper plate portion 522 is non-contact with the flange portion 22, an excessive decrease in the temperature of the flange portion 22 can be suppressed. That is, it is possible to suppress the conductive packing P1 from becoming hot while keeping the flange portion 22 at a high temperature.

[0039] (Frame body 4) As shown in FIG. 1, the frame body 4 is a frame that houses the crucible 2 and the heat insulating material 6. In this embodiment, the frame body 4 is composed of a case made of a metal plate. However, the frame body 4 is not limited to a metal plate and may be composed of, for example, a metal framework, PC (Precast Concrete), ceramics, etc. As shown in FIG. 2, the frame body 4 includes an inner frame member 41 and an outer frame member 42.

[0040] (Inner frame member 41) The inner frame member 41 houses the crucible 2 inside and fills the heat insulating material 6 (hereinafter sometimes referred to as the "inner heat insulating material 61") between the crucible 2. The inner frame member 41 is formed in a bottomed cylindrical shape having a side wall plate 411 and a bottom plate 412. As shown in FIG. 1, the side wall plate 411 extends in the vertical direction and extends from the upper surface of the heat insulating material 6 (hereinafter referred to as the "lower heat insulating material 63") laid on the lower plate 422 of the outer frame member 42 to the flange portion 22. Here, "extending to the flange portion 22" means that the upper end of the side wall plate 411 is located at any position within the range from the lower end to the upper end of the flange portion 22 in the vertical direction. However, the upper end of the side wall plate 411 may be located above the upper end of the crucible 2, or may be located below the lower end of the flange portion 22 as long as it is above the liquid level height of the molten metal.

[0041] The bottom plate 412 supports the inner heat insulating material 61 from below. The bottom plate 412 is along a horizontal plane. The bottom plate 412 is located above the lower end of the side wall plate 411, and a gap is formed between the bottom plate 412 and a virtual plane (here, the upper surface of the lower heat insulating material 63) passing through the lower end of the side wall plate 411. That is, the inner frame member 41 is formed in a so-called raised bottom shape.

[0042] As shown in Fig. 2, the bottom plate 412 is formed with an opening 413 through which the crucible table 3 passes. With the crucible table 3 passed through the opening 413, as shown in Fig. 3, the bottom plate 412 is positioned above the electrode connection part 32. Here, the bottom plate 412 is positioned above the vertical center of the crucible table 3. Thereby, the inner heat insulating material 61 can be positioned above the connection part between the electrode connection part 32 and the lower electrode part 55, and the connection part between the electrode connection part 32 and the lower electrode part 55 is configured not to be covered by the heat insulating material 6. In this embodiment, the bottom plate 412 is positioned below the upper surface of the crucible table 3.

[0043] Ribs 414 are provided around the opening 413 in the bottom plate 412. The ribs 414 surround the opening 413 in plan view. The bottom plate 412 that supports the inner heat insulating material 61 from below is reinforced by the ribs 414. The ribs 414 may be provided as appropriate according to the thickness dimension of the bottom plate 412 and the weight of the inner heat insulating material 61, and in the present invention, the ribs 414 may not be provided.

[0044] (Outer frame member 42) The outer frame member 42 is a member that constitutes the outer shell of the crucible furnace 1. The outer frame member 42 houses the inner frame member 41 inside and fills the space between the inner frame member 41 with a heat insulating material 6 (hereinafter sometimes referred to as "outer heat insulating material 62"). The outer frame member 42 is formed in a bottomed cylindrical shape having an outer side plate 421 and a bottom plate 422.

[0045] As shown in Fig. 1, the outer side plate 421 extends in the vertical direction and extends from the installation surface G1 of the crucible furnace 1 to a position exceeding the upper end of the crucible 2. The outer side plate 421 is separated from the side wall plate 411 of the inner frame member 41. As described above, the outer side plate 421 is configured to fill the outer heat insulating material 62 between itself and the inner frame member 41, but is configured to surround all of the heat insulating materials 6 (outer heat insulating material 62, inner heat insulating material 61, and lower heat insulating material 63).

[0046] The lower plate 422 supports the crucible 2, the crucible table 3, and all the heat insulating materials 6 from below. The lower plate 422 is along the horizontal plane, and a lower heat insulating material 63 is laid on the upper surface of the lower plate 422. The bottom plate 412 is located above the lower end of the side wall plate 411, and a gap is formed between it and the installation surface G1. That is, the outer frame member 42 is formed in a so-called raised bottom shape. In this embodiment, there is a gap between the lower plate 422 and the installation surface G1, but the lower plate 422 may be placed on the installation surface G1. That is, the outer frame member 42 does not have to be in a raised bottom shape.

[0047] Note that the outer frame member 42 is covered with an upper member 423 having an upper opening corresponding to the opening of the crucible 2 to cover the crucible 2. This upper opening can be opened and closed by a lid member 43 as shown in FIG. 2.

[0048] (Heat insulating material 6) As shown in FIG. 1, the heat insulating material 6 covers the outer surface of the crucible 2. As described above, the crucible furnace 1 according to this embodiment includes an inner heat insulating material 61, an outer heat insulating material 62, and a lower heat insulating material 63 as the heat insulating material 6.

[0049] The inner heat insulating material 61 is a heat insulating material disposed between the crucible 2 and the inner frame member 41. The inner heat insulating material 61 covers the immediate side of the crucible 2. A refractory heat insulating material having fire resistance is used for the inner heat insulating material 61 according to this embodiment. The inner heat insulating material 61 is formed in a powder form and is filled into the space surrounded by the crucible 2, the inner frame member 41, and the crucible table 3 without gaps. Examples of the material of the inner heat insulating material 61 include ceramics, quartz, alumina, microsilica (registered trademark), ceramic fiber, etc. Examples of ceramics include silica, magnesia, calcia, etc.

[0050] The outer heat insulation material 62 is a heat insulation material disposed between the outer frame member 42 and the inner frame member 41. The outer heat insulation material 62 covers the side of the crucible 2 (here, the outside of the inner heat insulation material 61). The outer heat insulation material 62 is formed in a plate shape and is fixed to the inner surface of the outer plate 421 of the outer frame member 42 and / or the side wall plate 411 of the inner frame member 41. Examples of the material of the outer heat insulation material 62 include, for example, ceramics, metals, white porcelain, platinum, quartz, alumina, resin foam, microsilica, silica aerogel, ceramic fiber, silica board, and the like.

[0051] The lower heat insulation material 63 is a heat insulation material disposed along the lower plate 422 on the lower plate 422 of the outer frame member 42. The lower heat insulation material 63 covers the lower part of the crucible 2. The lower heat insulation material 63 is formed in a plate shape in the same manner as the outer heat insulation material 62, and the same material as the outer heat insulation material 62 is used.

[0052] Thus, in the crucible furnace 1 according to the present embodiment, since the side and the lower part of the crucible 2 are covered by the heat insulation material 6, the temperature of the crucible 2 is less likely to decrease. On the other hand, when the electrode part 5 becomes hot and deformation or deterioration occurs in the electrode part 5, poor conduction is likely to occur at the contact point of the electrode part 5, and problems such as arc discharge and melting of the peripheral part may occur. Therefore, the crucible furnace 1 according to the present embodiment includes a cooling part 7 that cools the vicinity of the contact point of the electrode part 5.

[0053] (Cooling part 7) The cooling part 7 has a function of cooling at least the vicinity of the contact point in the electrode part 5. As the cooling part 7, any component, mechanism, or structure may be used as long as it can cool the vicinity of the contact point of the electrode part 5. The cooling part 7 includes a lower cooling part 71 (FIG. 3) and an upper cooling part 72 (FIG. 4).

[0054] (Lower cooling part 71) The lower cooling unit 71 has a function of being able to cool the vicinity of the contact point of the lower electrode unit 55. Specifically, as shown in FIG. 3, it cools the connection portion between the lower electrode unit 55 and the electrode connection unit 32. If the connection portion between the lower electrode unit 55 and the electrode connection unit 32 is covered with the heat insulating material 6 together with the crucible 2, it may rise to approximately 800°C to 900°C, and if use continues in this state, the lower electrode unit 55 may be deformed. On the other hand, the crucible furnace 1 according to the present embodiment includes the lower cooling unit 71, so that the connection portion between the lower electrode unit 55 and the electrode connection unit 32 can be cooled, and the temperature rise in the vicinity of the contact point of the lower electrode unit 55 can be suppressed.

[0055] The lower cooling unit 71 according to the present embodiment has a structure (non-covering structure) that realizes not covering the connection portion between the electrode connection unit 32 and the lower electrode unit 55 with the heat insulating material 6, and a structure (ventilation structure) that realizes radiating heat from the connection portion between the electrode connection unit 32 and the lower electrode unit 55 by air cooling.

[0056] The non-covering structure is a structure in which the bottom plate 412 of the inner frame member 41 is located above the connection portion between the electrode connection unit 32 and the lower electrode unit 55, and does not cover the connection portion. According to the non-covering structure, even if the crucible table 3 has a temperature rise, the heat of the connection portion between the electrode connection unit 32 and the lower electrode unit 55 can be radiated to the space below the bottom plate 412, so that the temperature rise in the vicinity of the contact point of the lower electrode unit 55 can be suppressed.

[0057] As a ventilation structure, the lower cooling unit 71 includes a plurality of air intake ports 711 and an air flow path 712. The air intake ports 711 are formed in the outer side plate 421 and penetrate at a position below the bottom plate 412 of the inner frame member 41. Each air intake port 711 is formed in a slit shape having a longitudinal direction along the vertical direction. However, in the present invention, the air intake port 711 is not limited to a slit, and may be constituted by, for example, a round hole, a rectangular hole, a long hole, an opening continuous to substantially the entire outer circumference leaving only the legs supporting the outer frame member 42, etc.

[0058] The air flow path 712 is a space that communicates with the air intake port 711 and is a space where the connection portion between the electrode connection portion 32 and the lower electrode portion 55 is arranged. The air flow path 712 is composed of a space below the bottom plate 412 of the inner frame member 41. A plurality of through holes 713 are formed at positions below the bottom plate 412 in the side wall plate 411, and a plurality of through holes 713 are also formed in the rib 414. The air flow path 712 leads from the air intake port 711, passes through these through holes 713, and communicates with the electrode connection portion 32.

[0059] Since the connection portion between the electrode connection portion 32 and the lower electrode portion 55 is arranged in the air flow path 712, the air taken in from the air intake port 711 flows through the air flow path 712 and exchanges heat with the electrode connection portion 32 within the air flow path 712. The air whose temperature has risen due to heat exchange is discharged to the outside of the outer frame member 42 from another air intake port 711 (also referred to as an air discharge port in this case). At this time, the temperature rise of the connection portion between the electrode connection portion 32 and the lower electrode portion 55 is suppressed by heat exchange with the air. Also, since the lower electrode portion 55 is also drawn out of the outer frame member 42 through the air flow path 712, the temperature rise is suppressed.

[0060] Further, it is preferable that the lower cooling portion 71 has a fluid flow path 73 that cools the connection portion between the electrode connection portion 32 and the lower electrode portion 55 from below. By passing a cooling fluid through the fluid flow path 73, the region of the contact point of the first electrode 551 with the crucible base 3 can be directly cooled. Note that the fluid flow path 73 may cool the connection portion between the electrode connection portion 32 and the lower electrode portion 55 from the side or from above.

[0061] Here, FIG. 6 is a bottom view of the fluid flow path 73 and the first electrode 551 as seen from below. As shown in FIG. 6, the fluid flow path 73 is formed within the case 74. The fluid flow path 73 is formed in a ninety-fold shape when viewed from the bottom. In the present embodiment, the case 74 and the first electrode 551 are integrally formed. The upper part of the fluid flow path 73 is open, and the inside of the fluid flow path 73 faces the first electrode 551. Inside the case 74, a cylindrical inlet portion 731 and a cylindrical outlet portion 732 are provided. The inlet portion 731 communicates with the inlet of the fluid flow path 73. The outlet portion 732 communicates with the outlet of the fluid flow path 73. As shown in FIG. 3, the inlet portion 731 and the outlet portion 732 protrude from the outer frame member 42.

[0062] The lower cooling portion 71 preferably includes a fluid transfer device that sends fluid to the fluid flow path 73. The fluid sent by the fluid transfer device may be a gas or a liquid. Examples of the fluid transfer device include a blower, a fan, a pump, and the like. When fluid flows into the inlet portion 731 by the fluid transfer device, the fluid directly contacts the first electrode 551, undergoes heat exchange, and then the heat-exchanged fluid exits from the outlet portion 732. By doing so, the connection portion between the electrode connection portion 32 and the lower electrode portion 55 can be cooled, and the temperature rise of the connection portion can be further suppressed.

[0063] As described above, the lower cooling portion 71 according to the present embodiment can cool the connection portion between the electrode connection portion 32 and the lower electrode portion 55 with both the non-coated structure and the ventilation structure, so that the temperature rise of the connection portion can be effectively suppressed. Moreover, in addition to the non-coated structure and the ventilation structure, since it has the fluid flow path 73 that cools the connection portion between the electrode connection portion 32 and the lower electrode portion 55 with the fluid flowing forcibly, the temperature rise of the connection portion can be further suppressed. In the present embodiment, the temperature of the connection portion between the lower electrode portion 55 and the electrode connection portion 32 can be suppressed to about 500°C, for example.

[0064] In the lower cooling unit 71 according to the present embodiment, the intake of air from the air intake port 711 is realized by natural convection caused by, for example, a temperature rise in the electrode connection part 32. However, for example, air may be forcibly taken in by a blower device such as a fan or a compressor. Further, a pipe through which the air blown from the blower device passes may be passed through the air intake port 711, and the air may be directly blown onto the electrode connection part 32 from the pipe.

[0065] (Upper cooling unit 72) As shown in FIG. 4, the upper cooling unit 72 cools the upper electrode part 51. In the crucible furnace 1 according to the present embodiment, as described above, in order to prevent heat dissipation by the flange part 22, the flange part 22 is covered with a heat insulator. For this reason, the flange part 22 has a high temperature of about 600°C to 700°C. Due to this high heat, the upper electrode part 51 may deteriorate. Also, the conductive packing P1 in contact with the flange part 22 may deteriorate due to oxidation. On the other hand, the crucible furnace 1 according to the present embodiment includes the upper cooling unit 72, so that the peripheral part of the upper electrode part 51 can be cooled. Thereby, the temperature rise of the peripheral part of the upper electrode part 51 and the conductive packing P1 can be suppressed, and the occurrence of problems due to high heat in the upper electrode part 51 and its peripheral part can be reduced.

[0066] As shown in FIG. 4, the upper cooling unit 72 according to the present embodiment includes a cooling pipe 721 that contacts the upper surface of the upper plate part 522 that presses the conductive packing P1 from above. The cooling pipe 721 is configured such that a fluid passes through it, and the upper plate part 522 can be cooled by the cooling pipe 721. The fluid passing through the cooling pipe 721 may be either a liquid or a gas, but considering the risk when the cooling pipe 721 is damaged, it is preferably a gas. Here, the upper cooling unit 72 is configured to cool the upper plate part 522 by air cooling.

[0067] The cooling pipe 721 is arranged so as to be close to the upper surface of the upper plate portion 522, and among the closeness, it is more preferable that it contacts the upper surface of the upper plate portion 522. The cooling pipe 721 is bent in a meandering shape so that sufficient heat exchange with the upper plate portion 522 can be performed. The air passing through the cooling pipe 721 is sent, for example, by a compressor, a fan, or the like.

[0068] In this way, the upper cooling portion 72 according to the present embodiment can suppress the temperature rise of the conductive packing P1 by cooling the upper electrode portion 51, so that the oxidation of the conductive packing P1 can be effectively suppressed. As a result, the temperature of the conductive packing P1 can be expected to drop by about 100 °C, for example, compared to the case where the upper electrode portion 51 is not provided.

[0069] Note that the upper cooling portion 72 is not limited to the cooling pipe 721, and for example, a heat dissipation fin, a cooling structure using a Peltier element, or the like may be used. Also, it does not have to be provided so as to face the upper plate portion 522, and at least one of the lower plate portion 523 and the vertical plate portion 524 may be cooled. Also, as the upper cooling portion 72, it is not always necessary to provide the cooling pipe 721, and cooling air may be directly blown onto the upper plate portion 522. Further, as shown in FIG. 5, as the upper cooling portion 72, instead of the cooling pipe 721, a box body 722 having a ninety-fold flow path 725 may be provided. The box body 722 has an air inlet 723, an air outlet 724, and a flow path 725 connecting the air inlet 723 and the air outlet 724. The flow path 725 has an opening surface on the lower surface, and the opening surface faces the upper plate portion 522. Thereby, when cooling air flows in from the air inlet 723, the cooling air directly contacts the upper plate portion 522. In this way, when the cooling air directly contacts the upper plate portion 522, the cooling efficiency can be increased compared to cooling through the cooling pipe 721. Note that the reference numeral 726 in FIG. 5 is a pin standing up from the upper plate portion 522 and attaches the box body onto the upper plate portion 522.

[0070] <Modification Example> The above embodiment is merely one of various embodiments of the present invention. The embodiment can be variously modified according to design and the like as long as the object of the present invention can be achieved. Hereinafter, modification examples of the embodiment will be enumerated. The modification examples described below can be applied in appropriate combinations.

[0071] In the above embodiment, the stationary crucible furnace 1 was used. However, in the present invention, there is no particular limitation as long as it is an electric crucible furnace 1. For example, it may be a pit-type crucible furnace 1 or a tilting-type crucible furnace 1.

[0072] In the above embodiment, the lower electrode part 55 was electrically connected to the lower part of the crucible 2 via the crucible table 3. However, in the present invention, it may be directly connected to the crucible 2.

[0073] In the above embodiment, an example in which there are three upper electrode parts 51 was described. However, in the present invention, it is not limited to this, and the number of upper electrode parts 51 may be two, four, or six. Also, the power supply to the upper electrode part 51 for the crucible 2 is not particularly limited, and for example, it may be either two-layer alternating current or three-phase alternating current.

[0074] The crucible furnace 1 according to the above embodiment includes the lower cooling part 71 for cooling the lower electrode part 55. However, for example, if the lower electrode part 55 is separated from the crucible 2, the temperature rise can be suppressed, so the lower cooling part 71 may not be provided.

[0075] In the above embodiment, the lower cooling part 71 includes both a non-coated structure and a ventilation structure. However, in the present invention, it may be composed of only the non-coated structure without the ventilation structure. Also, as the lower cooling part 71, the ventilation structure may be provided without the non-coated structure to air-cool the electrode connection part 32. Also, the non-coated structure and / or the ventilation structure may not be provided, and only the fluid flow path 73 may be provided. Also, the fluid flow path 73 may not be provided. Also, the lower cooling part 71 is not limited to air cooling or water cooling, and for example, it may be a lower cooling part that cools by bringing a Peltier element into contact with the connection part between the electrode connection part 32 and the lower electrode part 55.

[0076] In the crucible furnace 1 according to the above embodiment, as the heat insulating material 6, the inner heat insulating material 61, the outer heat insulating material 62, and the lower heat insulating material 63 are provided, but the lower heat insulating material 63 may not be provided. Further, as the heat insulating material 6, it is sufficient to include at least one of the inner heat insulating material 61 and the outer heat insulating material 62.

[0077] In the crucible furnace 1 according to the above embodiment, the flange portion 22 is provided, but in the present invention, the flange portion 22 may not be provided. In this case, the upper electrode portion 51 may be attached to the upper end edge portion of the crucible body 21.

[0078] In this specification, expressions with "substantially", such as "substantially parallel" or "substantially orthogonal", may be used. For example, "substantially parallel" means substantially "parallel", and includes not only a strictly "parallel" state but also a state with an error of about several degrees. The same applies to other expressions with "substantially".

[0079] Also, in this specification, expressions distinguished by the presence or absence of "... portion", such as "end portion" and "end", are used. For example, "end" means the end part of an object, but "end portion" means a region having a certain range including the "end". Any point within a certain range including the end is regarded as an "end portion". The same applies to other expressions with "... portion".

[0080] <Summary> As described above, the crucible furnace 1 according to the first aspect includes a crucible 2 that generates heat by energization, a lower electrode portion 55 electrically connected to the lower part of the crucible 2, an upper electrode portion 51 electrically connected to the upper part of the crucible 2, a heat insulator that covers the upper part of the crucible 2, and an upper cooling portion 72 that cools the upper electrode portion 51. According to this aspect, by cooling the upper electrode portion 51, it is possible to suppress the temperature rise of the upper part of the crucible 2 that contacts the upper part of the crucible 2 and the upper cooling portion 72, and reduce the occurrence of problems due to high heat in the upper electrode portion 51 and its peripheral portion.

[0081] In the crucible furnace 1 according to the second aspect, in the first aspect, the crucible 2 has a flange portion 22 protruding outward from the upper end of the crucible 2, and the upper electrode portion 51 is connected to the flange portion 22 of the crucible 2. According to this aspect, while reducing the temperature drop of the flange portion 22 of the crucible 2 by the heat insulator, it is possible to suppress the upper electrode portion 51 and its peripheral portion from becoming too hot.

[0082] The crucible furnace 1 according to the third aspect further includes a conductive packing P1 disposed between the upper electrode portion 51 and the flange portion 22 in the second aspect. According to this aspect, while enhancing the electrical conductivity between the flange portion 22 and the upper electrode portion 51, it is possible to suppress the deterioration of the conductive packing P1 by the upper cooling portion 72.

[0083] In the crucible furnace 1 according to the fourth aspect, in any one of the first to third aspects, the upper cooling portion 72 is configured to cool the upper electrode portion 51 by air cooling. According to this aspect, even if the upper cooling portion 72 is damaged, it is possible to avoid the risk of contact between the molten metal and something other than air (for example, water in the case of water cooling).

[0084] In the crucible furnace 1 according to the fifth aspect, in any one of the first to fourth aspects, the heat insulator covers the upper portion of the crucible 2 and the upper electrode portion 51. According to this aspect, while reducing the temperature drop of the upper electrode portion 51 and the upper portion of the crucible 2, it is possible to suppress an excessive temperature rise of the upper electrode portion 51 and its peripheral portion.

Explanation of Reference Numerals

[0085] 1 Crucible furnace 2 Crucible 21 Crucible body 3 Crucible stand 51 Upper electrode portion 55 Lower electrode portion 6 Heat insulating material 7 Cooling portion 72 Upper cooling portion P1 Conductive packing

Claims

1. A crucible that generates heat when an electric current is applied, A lower electrode portion electrically connected to the lower part of the crucible, An upper electrode portion electrically connected to the upper part of the crucible, A heat insulator that covers the upper part of the crucible, An upper cooling portion that cools the upper electrode portion, Comprising, The upper cooling portion is configured to cool the upper electrode portion by air cooling, Crucible furnace.

2. The crucible has a flange portion that protrudes outward from the upper end of the crucible, The upper electrode portion is connected to the flange portion of the crucible, The crucible furnace according to claim 1.

3. Further comprising a conductive packing disposed between the upper electrode portion and the flange portion, The crucible furnace according to claim 2.

4. Further comprising a lower cooling portion that cools the lower electrode portion, The crucible furnace according to any one of claims 1 to 3.

5. The heat insulator covers the upper part of the crucible and the upper electrode portion, The crucible furnace according to any one of claims 1 to 3.

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