WO2018163747A1 - Plasma torch, plasma torch forward end electrode, and molten metal heating device - Google Patents

Plasma torch, plasma torch forward end electrode, and molten metal heating device Download PDF

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Publication number
WO2018163747A1
WO2018163747A1 PCT/JP2018/005289 JP2018005289W WO2018163747A1 WO 2018163747 A1 WO2018163747 A1 WO 2018163747A1 JP 2018005289 W JP2018005289 W JP 2018005289W WO 2018163747 A1 WO2018163747 A1 WO 2018163747A1
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WO
WIPO (PCT)
Prior art keywords
plasma torch
tip
main body
molten metal
plasma
Prior art date
Application number
PCT/JP2018/005289
Other languages
French (fr)
Japanese (ja)
Inventor
浩規 前川
三浦　康彰
Original Assignee
新日鉄住金エンジニアリング株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
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Application filed by 新日鉄住金エンジニアリング株式会社 filed Critical 新日鉄住金エンジニアリング株式会社
Priority to KR1020197013087A priority Critical patent/KR102212239B1/en
Priority to CN201880004248.1A priority patent/CN109952815A/en
Publication of WO2018163747A1 publication Critical patent/WO2018163747A1/en

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/3431—Coaxial cylindrical electrodes
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Tank furnaces
    • F27B3/08—Hearth-type furnaces, e.g. of reverberatory type; Tank furnaces heated electrically, with or without any other source of heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00—Arrangement of elements for electric heating in or on furnaces
    • F27D11/08—Heating by electric discharge, e.g. arc discharge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D99/00—Subject matter not provided for in other groups of this subclass
    • F27D99/0001—Heating elements or systems
    • F27D99/0006—Electric heating elements or system
    • F27D2099/0031—Plasma-torch heating

Definitions

  • the present disclosure relates to a plasma torch, a tip electrode for the plasma torch, and a molten metal heating device.
  • Patent Document 1 discloses a plasma torch made of graphite.
  • the plasma torch is used to effectively heat the molten slag in the melting furnace body.
  • the plasma torch is inserted into a through-hole of a lid arranged to cover the upper opening of the melting furnace main body.
  • the lower end portion of the plasma torch is located in the internal space surrounded by the melting furnace main body and the lid, and the upper end portion of the plasma torch is located outside the internal space.
  • the interior space is usually filled with an inert gas. That is, almost no oxygen is present in the internal space. Therefore, although the molten metal exists and is in a high temperature environment, the amount of oxygen that reacts with graphite is small, and the plasma torch (lower end portion of the torch) located in the internal space is less likely to be worn. On the other hand, although a large amount of oxygen exists outside the internal space, the temperature outside the internal space is low, so that the plasma torch (the torch upper end portion) located outside the internal space is not easily worn out.
  • the present disclosure describes a plasma torch capable of extending the life, a tip electrode for the plasma torch, and a molten metal heating apparatus capable of extending the life of the plasma torch.
  • a plasma torch generates plasma between molten metal in a container including a storage tank that stores molten metal and a lid that covers an opening of the storage tank that is opened upward.
  • a metal main body configured to be able to be inserted into a through-hole provided in the lid so that a tip portion toward the molten metal is located in the container at the time of heat treatment of the molten metal by plasma, And a tip electrode made of graphite attached to the tip of each.
  • the metal main body can be inserted into the through hole so that the tip of the main body facing the molten metal is located in the container during the heat treatment of the molten metal (molten liquid metal) by plasma. It is configured. Therefore, the graphite tip electrode does not exist in the vicinity of the through hole of the lid. Therefore, wear of the tip electrode is extremely suppressed. As a result, it is possible to extend the life of the plasma torch.
  • the tip electrode made of graphite is used, it is possible to generate plasma with a probability of 100% by immersing the tip electrode in the molten metal when generating plasma and pulling the tip electrode out of the molten metal. . Note that when a metal plasma torch is used as a whole, the graphite is not worn, but if the plasma torch is immersed in the molten metal, the plasma torch is melted and it becomes difficult to control the temperature of the molten metal.
  • the plasma torch of Example 1 may further include an insulating coating provided so as to cover the outer peripheral surface of the main body.
  • the main body is inserted into the through-hole during the heat treatment of the molten metal with plasma, and even if the distance between the main body and the lid is close, the insulating coating material prevents discharge (plasma generation) between the main body and the lid. Can be removed. Therefore, it becomes possible to perform the heat treatment of the molten metal using a plasma torch safely and stably.
  • an insulating coating is provided on the outer peripheral surface of a plasma torch made entirely of graphite, although the discharge between the plasma torch and the lid can be prevented, the graphite itself becomes hot during the heat treatment of the molten metal by plasma.
  • the insulating coating material having a large difference in thermal expansion coefficient from graphite is peeled off from the outer peripheral surface of graphite. Although it may be possible to suppress the peeling of the insulating coating material from the graphite by cooling the graphite, the graphite is structurally brittle, so it is difficult to provide a flow path for the coolant in the graphite plasma torch. .
  • a plasma torch according to another example of the present disclosure includes a metal main body, a graphite tip electrode attached to a tip portion of the main body, and an insulating coating provided to cover the outer peripheral surface of the main body. .
  • the insulating coating material is provided so as to cover the outer peripheral surface of the main body, the main body is inserted into the through-hole during the heat treatment of the molten metal by plasma, and even if the distance between the main body and the lid is close, insulation is provided.
  • the covering material prevents discharge (plasma generation) between the main body and the lid. Therefore, it becomes possible to perform the heat treatment of the molten metal using a plasma torch safely and stably.
  • the tip electrode may be configured to be detachable from the tip portion.
  • a new tip electrode may be attached to the main body. Therefore, the main body can be reused. Therefore, the running cost of the plasma torch can be reduced.
  • the tip electrode may be configured to be screwable with the tip portion. In this case, it is possible to exchange the tip electrode very easily.
  • Example 6 In the plasma torch of Example 4 or Example 5, the tip portion is provided with a concave portion having an inclined surface that increases in diameter toward the tip, and the tip electrode has a convex portion having an outer peripheral surface corresponding to the inclined surface. It is provided and the convex part of the tip electrode may be comprised so that fitting to the recessed part of a tip part is possible. In this case, the contact area between the tip electrode and the tip (main body) is increased. Therefore, when the plasma torch is energized for plasma generation and current flows between the main body and the tip electrode, Joule heat is hardly generated at the contact portion between the main body and the tip electrode. Therefore, since wear due to heat generation of the tip electrode is further suppressed, it is possible to further extend the life of the plasma torch.
  • Example 7 In the plasma torch of Examples 1 to 6, the distal end portion of the main body may be configured to be detachable from the proximal end portion of the main body. In this case, when the tip of the main body is damaged, a new tip may be attached to the base end of the main body. Therefore, the base end portion of the main body can be reused. Therefore, the running cost of the plasma torch can be reduced.
  • Example 8 In any of the plasma torches of Examples 1 to 7, a coolant flow path may be provided in the main body.
  • the tip electrode attached to the tip of the main body is also cooled by cooling the main body with the coolant. For this reason, since wear due to heat generation of the tip electrode is further suppressed, it is possible to further extend the life of the plasma torch.
  • Example 9 The plasma torch of any of Examples 1 to 8 may be provided with a through hole that functions as a flow path for the working gas for generating plasma extending along the longitudinal direction. In this case, since the operating gas flows from the plasma torch toward the molten metal, stable plasma can be generated.
  • Example 10 In the plasma torch of Example 9, the main body has an outer tube portion extending along the longitudinal direction, and a center portion inserted through the outer tube portion, and the tip electrode is attached to the tip portion of the center portion.
  • the through hole may be formed by an annular gap formed between the tube portion and the center portion.
  • the peripheral edge of the tip electrode receives heat.
  • the heat receiving region (heat receiving portion) of the tip electrode is relatively wide, so that heat is easily dispersed. Therefore, the maximum temperature on the tip surface of the tip electrode is lowered, and the temperature distribution on the tip surface of the tip electrode becomes gentle. As a result, since wear due to heat generation at the tip electrode is further suppressed, it is possible to further extend the life of the plasma torch.
  • Example 11 In the plasma torch of Example 9, the main body has an outer tube portion extending along the longitudinal direction, and a central portion inserted into the outer tube portion, and the tip electrode is disposed on the inner side of the annular outer portion and the outer portion.
  • An inner portion that can be arranged, the inner portion is attached to the distal end portion of the center portion, and the outer portion is attached to the outer tube portion, and the outer tube portion and the outer portion are connected to the center portion and the inner portion.
  • the through hole may be formed by an annular gap formed between them. In this case, when plasma is generated between the plasma torch (tip electrode) and the molten metal, the vicinity of the through hole in the tip electrode is particularly heated.
  • the heat receiving region (heat receiving portion) of the tip electrode is relatively wide, so that heat is easily dispersed. Therefore, the maximum temperature on the tip surface of the tip electrode is lowered, and the temperature distribution on the tip surface of the tip electrode becomes gentle. As a result, since wear due to heat generation at the tip electrode is further suppressed, it is possible to further extend the life of the plasma torch.
  • Example 12 In the plasma torch of Example 11, the outer tube portion and the outer portion, and the center portion and the inner portion may be electrically insulated from each other. In this case, the outer tube portion and the outer portion, and the center portion and the inner portion can be connected to power sources having different polarities. Thereby, plasma is generated by discharging between the outer portion and the inner portion. In this state, by increasing the output of the power source, plasma generated between the outer side and the inner side grows. When the grown plasma reaches the molten metal, the plasma can be generated between the plasma torch and the molten metal by connecting the outer and inner parts and the molten metal to power sources having different polarities. Accordingly, even when the distance between the tip of the plasma torch and the molten metal is large, it is possible to stably generate plasma between the tip of the plasma torch and the molten metal.
  • Example 13 The plasma torch of any of Examples 1 to 12 may further include an annular insulating member that covers a region exposed to the outside of the contact portion between the tip electrode and the tip portion. In this case, it is possible to prevent discharge from occurring in the vicinity of the contact portion of the tip electrode. Therefore, it can suppress that a front-end
  • a tip electrode for a plasma torch has a metal main body in which a tip portion toward a molten metal is located in the container when the molten metal in the container is heated by plasma.
  • This is a graphite tip electrode for a plasma torch in which a main body is configured to be inserted into a through-hole provided in a lid, and is configured to be detachable from a tip portion of the main body.
  • the tip electrode for a plasma torch according to Example 14 has a metal main body in which a tip portion toward the molten metal is located in the container when the molten metal in the container is heated by plasma, and is provided on the lid of the container. It is used for a plasma torch in which a main body is configured to be inserted into a through hole. Therefore, the graphite tip electrode does not exist in the vicinity of the through hole of the lid. Therefore, wear of the tip electrode is extremely suppressed. As a result, it is possible to extend the life of the plasma torch.
  • the tip electrode for the plasma torch according to Example 14 is made of graphite, when the plasma is generated, the tip electrode is immersed in the molten metal, and the tip electrode is pulled out of the molten metal to generate plasma with a probability of 100%. It becomes possible to make it. Note that when a metal plasma torch is used as a whole, the graphite is not worn, but if the plasma torch is immersed in the molten metal, the plasma torch is melted and it becomes difficult to control the temperature of the molten metal.
  • a tip electrode for a plasma torch according to another example of the present disclosure is configured to be attachable to and detachable from a tip portion of a metal main body provided with an insulating coating material so as to cover an outer peripheral surface.
  • the tip electrode for a plasma torch according to Example 15 when the molten metal (molten liquid metal) in the container is heat-treated with plasma, the tip of the metal main body facing the molten metal is positioned in the container. The main body is inserted into the through hole. Therefore, the graphite tip electrode does not exist in the vicinity of the through hole of the lid. Therefore, wear of the tip electrode is extremely suppressed. As a result, it is possible to extend the life of the plasma torch. Moreover, since the tip electrode for the plasma torch according to Example 15 is made of graphite, plasma is generated with a probability of 100% by immersing the tip electrode in the molten metal when the plasma is generated and pulling the tip electrode out of the molten metal. It becomes possible to make it.
  • the insulating coating material is provided so as to cover the outer peripheral surface of the main body, the main body is inserted into the through-hole during the heat treatment of the molten metal by plasma, and even if the distance between the main body and the lid is close, insulation is provided.
  • the covering material prevents discharge (plasma generation) between the main body and the lid. Therefore, the heat treatment of the molten metal using the plasma torch to which the tip electrode according to Example 15 is attached can be performed safely and stably.
  • a molten metal heating apparatus includes a container including a storage tank that stores the molten metal, a lid that covers an opening of the storage tank that is opened upward, and the molten metal in the container.
  • a plasma torch that generates plasma, and the plasma torch is configured to be able to be inserted into a through-hole provided in the lid so that a tip portion toward the molten metal is located in the container when the molten metal is heated by the plasma. It has a metal main body and a graphite tip electrode attached to the tip of the main body.
  • the metal main body is inserted into the through hole so that the tip of the main body facing the molten metal is located in the container. It is configured to be possible. Therefore, the graphite tip electrode does not exist in the vicinity of the through hole of the lid. Therefore, wear of the tip electrode is extremely suppressed. As a result, it is possible to extend the life of the plasma torch.
  • the tip electrode made of graphite is used, it is possible to generate plasma with a probability of 100% by immersing the tip electrode in the molten metal when generating plasma and pulling the tip electrode out of the molten metal. . Note that when a metal plasma torch is used as a whole, the graphite is not worn, but if the plasma torch is immersed in the molten metal, the plasma torch is melted and it becomes difficult to control the temperature of the molten metal.
  • the plasma torch according to the present disclosure, the tip electrode for the plasma torch, and the molten metal heating measure can extend the life of the plasma torch.
  • FIG. 1 is a diagram illustrating an example of a continuous casting apparatus.
  • FIG. 2 shows a cross section of the plasma torch of FIG.
  • FIG. 3 shows a cross section of a conventional plasma torch.
  • FIG. 4 shows a cross section of a conventional plasma torch.
  • FIG. 5 shows a cross section of a plasma torch according to another example.
  • FIG. 6 shows a cross section of a plasma torch according to another example.
  • FIG. 7 shows a cross section of a plasma torch according to another example.
  • FIG. 8 shows a cross section of a plasma torch according to another example.
  • FIG. 9 shows a cross section of a plasma torch according to another example.
  • FIG. 10 shows a cross section of a plasma torch according to another example.
  • FIG. 11 shows a cross section of a plasma torch according to another example.
  • the continuous casting apparatus 100 includes a ladle 101, a tundish 102 (a molten metal heating apparatus), a mold 103, a cast piece support roll 104, and a plasma generator 1 (a molten metal heating apparatus).
  • the ladle 101 is a container for storing molten metal (molten steel) M.
  • the tundish 102 is disposed below the ladle 101.
  • the tundish 102 (container) has a main body 102a (storage tank) and a lid 102b.
  • the main body 102 a stores the molten metal M that has flowed out from the nozzle 101 a provided on the bottom wall of the ladle 101.
  • the lid 102b covers the opening 102c of the main body 102a opened upward.
  • the lid 102b is provided with a through hole 102d that communicates the inside and outside of the tundish 102.
  • the mold 103 is disposed below the tundish 102.
  • the mold 103 is molded into a predetermined shape while cooling the molten metal flowing out from the nozzle 102e provided on the bottom wall of the tundish 102.
  • the slab support roll 104 conveys the slab S drawn out from the mold 103 while cooling it.
  • the plasma generator 1 is a device for controlling the temperature of the molten metal M in the tundish 102. Therefore, the plasma generator 1 constitutes a molten metal heating device together with the tundish 102.
  • the plasma generator 1 includes a plasma torch 10, a torch holder 12, an elevator 14, and an operating gas source 16.
  • the plasma torch 10 is, for example, a round bar (straight bar) extending linearly.
  • the diameter of the plasma torch 10 may be about 50 mm to 200 mm, for example.
  • the length of the plasma torch 10 may be about 1000 mm to 2500 mm, for example.
  • the shape of the plasma torch 10 may be a shape other than a round shape, or may not necessarily extend linearly but may be bent.
  • the plasma torch 10 is connected to a power source (not shown), and a predetermined voltage (for example, about 100 V to 500 V) is applied.
  • the plasma torch 10 includes a metal main body 18, a graphite tip electrode 20, and an insulating coating material 22.
  • the main body 18 is provided with a through hole H1.
  • the through hole H1 has, for example, a circular shape, and extends along the axial direction of the main body 18 (longitudinal direction of the plasma torch 10).
  • the diameter of the through hole H1 may be about 10 mm, for example.
  • the main body 18 is provided with a flow path F of a coolant (for example, water) so as to surround the through hole H1.
  • the coolant is supplied to the flow path F from a coolant source (not shown).
  • the coolant is discharged after flowing through the flow path F, cooled by, for example, a heat exchanger, and supplied to the flow path F again. As the coolant circulates through the flow path F, the entire plasma torch 10 (the main body 18 and the tip electrode 20) is cooled.
  • the tip electrode 20 is attached to the lower end portion 18 a (tip portion) of the main body 18. More specifically, the tip electrode 20 is attached to the tip surface T1 of the lower end 18a.
  • the contact area between the tip electrode 20 and the main body 18 is large, the Joule heat generated at the contact portion between the tip electrode 20 and the main body 18 when the plasma torch 10 is energized becomes small, and the plasma torch 10 (the main body 18 and the tip electrode 20). ) Wear can be suppressed.
  • the contact area between the tip electrode 20 and the main body 18 is X and the current flowing through the plasma torch 10 is Y
  • the contact area X may satisfy X / Y ⁇ 1.0 [A / mm 2 ].
  • the value obtained by dividing the current Y by the contact area X represents the density of current passing through the contact portion (passing current density).
  • the tip electrode 20 is provided with a through hole H2.
  • the through hole H2 extends along the axial direction of the tip electrode 20 (plasma torch 10).
  • the through hole H ⁇ b> 2 communicates with the through hole H ⁇ b> 1 in a state where the tip electrode 20 is attached to the tip surface T ⁇ b> 1 of the main body 18.
  • the insulating coating material 22 is provided on the entire outer peripheral surface of the main body 18.
  • the insulating coating material 22 is obtained, for example, by spraying alumina (Al 2 O 3 ) on the outer peripheral surface of the main body 18.
  • the torch holder 12 holds the base end portion 18b of the main body 18 (plasma torch 10).
  • the torch holder 12 can hold the plasma torch 10 such that the plasma torch 10 is inclined by about 0 ° to 30 ° with respect to the vertical axis, for example.
  • the elevator 14 moves the torch holder 12 up and down. Therefore, the plasma torch 10 held by the torch holder 12 is also raised and lowered in the vertical direction by the elevator 14, and approaches and separates from the molten metal M in the tundish 102.
  • the plasma torch 10 is raised by the elevator 14 when the lower end (tip) of the plasma torch 10 is located in the tundish 102, the plasma torch 10 passes through the through-hole 102d of the lid 102b and the Move out.
  • the lower end portion of the plasma torch 10 moves into the tundish 102 through the through hole 102d of the lid 102b.
  • the working gas source 16 supplies a working gas (for example, an inert gas such as argon or nitrogen) for generating plasma to the through holes H1 and H2. Therefore, the through holes H1 and H2 function as operating gas flow paths.
  • the working gas source 16 is connected to the through holes H ⁇ b> 1 and H ⁇ b> 2 via the pipe 24.
  • the pipe 24 is provided with a valve 26. According to opening / closing of the valve 26, the supply state of the working gas from the working gas source 16 to the through holes H1, H2 and the non-supply state are switched.
  • the operating gas source 16, the pipe 24, and the valve 26 function as supply means for supplying the operating gas to the through holes H1 and H2 (plasma torch 10).
  • the periphery of the tip electrode 20 (near the molten metal surface of the molten metal M) is set as an operating gas atmosphere. Specifically, the valve 26 is opened, and the working gas is supplied from the working gas source 16 into the tundish 102 through the through holes H1 and H2. Further, a predetermined voltage is applied to the plasma torch 10.
  • the elevator 14 lowers the plasma torch 10 toward the molten metal M.
  • the entire tip electrode 20 is located in the tundish 102 (in the internal space between the main body 102 a and the lid 102 b), and the main body 18 and the insulating coating material 22 face the through hole 102 d.
  • the plasma torch 10 is positioned with respect to the tundish 102 and the surface of the molten metal M so as to be in a state. Thereby, the tip electrode 20 is brought close to the melt M until the distance (gap) between the tip electrode 20 (plasma torch 10) and the melt M becomes a predetermined size.
  • the upper end of the part is also difficult to wear.
  • the low temperature outside air containing oxygen and the hot air in the tundish 102 are mixed.
  • the portion of the plasma torch 50 that is inserted through the through hole 102d (the intermediate portion of the plasma torch 50) is easily worn out by the reaction of graphite and oxygen. Therefore, as shown in FIG. 3, the middle portion of the plasma torch 50 may be thinned, which may affect the life of the plasma torch 50. It is also conceivable to use a metal plasma torch for the occurrence of such wrinkles.
  • the distance between the intermediate portion of the plasma torch 50 and the through hole 102d is relatively short. Therefore, when the atmosphere around the plasma torch 50 becomes unstable, as shown in FIG. 4, there is a possibility that plasma P1 is generated due to discharge between the outer peripheral surface of the plasma torch 50 and the through hole 102d. In order to prevent such discharge, an insulating coating material may be provided on the outer peripheral surface of the plasma torch 50.
  • the plasma torch 50 is made of graphite, the graphite itself becomes a high temperature and thermally expands during the heat treatment of the molten metal M by the plasma torch 50.
  • the thermal expansion coefficient of graphite is larger than the thermal expansion coefficient of the insulating coating material, the insulating coating material is peeled off from the outer surface of the plasma torch 50. Although it is conceivable to suppress peeling of the insulating coating material by cooling the graphite, it is difficult to provide a flow path for the coolant in the graphite plasma torch 50 because graphite is structurally brittle.
  • the metal main body 18 is a through-hole so that the lower end portion 18a of the main body 18 facing the molten metal M is positioned in the tundish 102 during the heat treatment of the molten metal M with the plasma P. It is configured to be able to be inserted into 102d. For this reason, the graphite tip electrode 20 does not exist in the vicinity of the through hole 102d of the lid 102b. Therefore, wear of the tip electrode 20 is extremely suppressed. As a result, the life of the plasma torch 10 can be extended.
  • the tip electrode 20 is immersed in the molten metal, and the tip electrode 20 is pulled up from the molten metal M, thereby generating the plasma P with a probability of 100%. It becomes possible to make it.
  • the insulating coating material 22 is provided so as to cover the outer peripheral surface of the main body 18. Therefore, even when the main body 18 is inserted into the through-hole 102d during the heat treatment of the molten metal M by the plasma P and the distance between the main body 18 and the lid 102b is close, the insulating coating material 22 causes the gap between the main body 18 and the lid 102b. Discharge (plasma generation) is prevented. Therefore, the heat treatment of the molten metal M using the plasma torch 10 can be performed safely and stably.
  • a coolant flow path F is provided in the main body 18. Therefore, the tip electrode 20 attached to the lower end portion 18a of the main body 18 is also cooled by cooling the main body 18 with the coolant. Therefore, since wear due to heat generation of the tip electrode 20 is further suppressed, the life of the plasma torch 10 can be further extended.
  • the through holes H1 and H2 that function as flow paths for the working gas for generating the plasma P in the main body 18 and the tip electrode 20 extend along the longitudinal direction (axial direction) of the plasma torch 10, respectively. Is provided. Therefore, the operating gas flows from the plasma torch 10 toward the molten metal M, so that stable plasma P can be generated.
  • the tip electrode 20 may be configured to be attachable to and detachable from the lower end portion 18a (tip surface T1) of the main body 18.
  • the tip electrode 20 when the tip electrode 20 is worn with the generation of the plasma P, a new tip electrode 20 may be attached to the main body 18. Therefore, the main body 18 can be reused. Therefore, the running cost of the plasma torch 10 can be reduced.
  • the internal thread portion 18 c formed on the lower end portion 18 a of the main body 18 and the external thread portion 20 a provided on the tip electrode 20 may be configured to be screwable.
  • the male screw portion 18 d formed on the lower end portion 18 a of the main body 18 and the female screw portion 20 b provided on the tip electrode 20 may be configured to be screwable.
  • the tip electrode 20 can be replaced very simply.
  • the tip electrode 20 side has a female screw portion 20b, the tip electrode 20 has a large diameter, so that the tip electrode 20 can be increased in strength.
  • the main body 18 may have an outer tube portion 18A extending along the axial direction (longitudinal direction) and a center portion 18B inserted into the outer tube portion 18A.
  • the outer tube portion 18A is separate from the center portion 18B.
  • an insulating coating material 22 is provided as a whole.
  • the inner diameter of the outer tube portion 18A is larger than the outer diameter of the center portion 18B. Therefore, an annular through hole H3 extending in the axial direction (longitudinal direction) of the main body 18 is provided between the outer tube portion 18A and the center portion 18B. That is, the through hole H3 surrounds the central portion 18B.
  • the through hole H3 is connected to the operating gas source 16, and the operating gas is supplied from the operating gas source 16.
  • Flow paths FA and FB through which a coolant flows are provided inside the outer pipe portion 18A and the center portion 18B, respectively.
  • An internal thread portion 18c is formed at the lower end portion 18a of the center portion 18B.
  • the female screw portion 18 c is configured to be screwable with a male screw portion 20 a provided on the tip electrode 20. Therefore, the tip electrode 20 can be attached to and detached from the center portion 18B.
  • the periphery of the tip electrode 20 is particularly heated.
  • the heat receiving region (heat receiving portion) of the tip electrode 20 is relatively wide, so that heat is easily dispersed. Accordingly, the maximum temperature on the tip surface T2 of the tip electrode 20 is lowered, and the temperature distribution on the tip surface T2 of the tip electrode 20 is gentle. As a result, since wear due to heat generation of the tip electrode 20 is further suppressed, the life of the plasma torch 10 can be further extended.
  • the main body 18 has an outer tube portion 18A extending along the axial direction (longitudinal direction) thereof, and a center portion 18B inserted through the outer tube portion 18A.
  • 20 may have an annular outer portion 20A and an inner portion 20B that can be disposed inside the outer portion.
  • the outer pipe portion 18A is separate from the center portion 18B.
  • Each of the outer peripheral surface of the outer tube portion 18A and the outer peripheral surface of the center portion 18B is provided with an insulating coating material 22 as a whole.
  • the inner diameter of the outer tube portion 18A is larger than the outer diameter of the center portion 18B. Therefore, an annular through hole H3 extending in the axial direction (longitudinal direction) of the main body 18 is provided between the outer tube portion 18A and the center portion 18B. That is, the through hole H3 surrounds the central portion 18B.
  • the through hole H3 is connected to the operating gas source 16, and the operating gas is supplied from the operating gas source 16.
  • Flow paths FA and FB through which a coolant flows are provided inside the outer pipe portion 18A and the center portion 18B, respectively.
  • the inner diameter of the outer portion 20A is larger than the outer diameter of the inner portion 20B.
  • a male screw portion 20a is provided on the outer peripheral surface of the outer portion 20A.
  • the external thread part 20A of the outer side part 20A is configured to be screwable with an internal thread part 18c provided at the lower end part 18a of the outer pipe part 18A. Therefore, the outer portion 20A can be attached to and detached from the outer tube portion 18A.
  • a male screw portion 20a is provided on the outer peripheral surface of the inner portion 20B.
  • the male screw portion 20a of the inner portion 20B is provided at the lower end portion 18a of the center portion 18B and is configured to be screwable with the female screw portion 18c. Therefore, the inner side part 20B is detachable with respect to the center part 18B.
  • an annular penetration extending in the axial direction of the tip electrode 20 is provided between the outer portion 20A and the inner portion 20B.
  • a hole H4 is provided. The through hole H4 communicates with the through hole H3, and the working gas flows through the through hole H3.
  • the plasma torch 10 shown in FIG. 8 when the plasma P is generated between the plasma torch 10 (tip electrode 20) and the molten metal M, the vicinity of the through hole H4 in the tip electrode 20 is particularly heated. For this reason, the heat receiving region (heat receiving portion) of the tip electrode 20 is relatively wide, so that heat is easily dispersed. Accordingly, the maximum temperature on the tip surface T2 of the tip electrode 20 is lowered, and the temperature distribution on the tip surface T2 of the tip electrode 20 is gentle. As a result, since wear due to heat generation of the tip electrode 20 is further suppressed, the life of the plasma torch 10 can be further extended.
  • the outer tube portion 18A and the outer portion. 20A and the central portion 18B and the inner portion 20B are electrically insulated from each other. Therefore, the outer tube portion 18A and the outer portion 20A, and the center portion 18B and the inner portion 20B can be connected to power supplies having different polarities. As a result, discharge occurs between the outer portion 20A and the inner portion 20B, and plasma P is generated. By increasing the power output in this state, the plasma P generated between the outer portion 20A and the inner portion 20B grows.
  • the plasma torch 10 tip electrode 20
  • the molten metal M are connected by connecting the outer portion 20A and the inner portion 20B and the molten metal M to different power sources.
  • Plasma P can be generated between the two. Therefore, even when the distance between the tip of the plasma torch 10 and the molten metal M is large, it is possible to stably generate the plasma P between the tip of the plasma torch 10 and the molten metal.
  • the lower end portion 18 a may be configured to be detachable from the base end portion 18 e of the main body 18. Specifically, the internal thread part 18f formed in the lower end part 18a and the external thread part 18g formed in the base end part 18e can be screwed together.
  • An insulating coating material 22 is provided on each of the outer peripheral surface of the lower end portion 18a and the outer peripheral surface of the base end portion 18e.
  • a tip electrode 20 is attached to the tip surface T1 of the lower end 18a. In this case, when the lower end 18 a of the main body 18 is damaged, a new lower end 18 a may be attached to the base end 18 e of the main body 18. Therefore, the base end portion 18e of the main body 18 can be reused. Therefore, the running cost of the plasma torch 10 can be reduced.
  • the plasma torch 10 may further include an insulating member 25.
  • the insulating member 25 has an annular shape and covers a region exposed to the outside in the contact portion between the tip electrode 20 and the lower end portion 18a.
  • a concave groove corresponding to the outer shape of the insulating member 25 is formed in the contact portion. Therefore, when attaching the insulating member 25 to the contact portion, first, the insulating member 25 is fitted into the concave groove on the lower end portion 18a side with the tip electrode 20 and the lower end portion 18a removed. Next, the male screw portion 20a of the tip electrode 20 is screwed into the female screw portion 18c of the lower end portion 18a.
  • the insulating member 25 is held in the recessed grooves of the tip electrode 20 and the lower end portion 18a. In this case, it is possible to prevent discharge from occurring in the vicinity of the contact portion of the tip electrode 20. Therefore, it is possible to prevent the lower end portion 18a from being excessively heated and deformed.
  • the lower end portion 18a may be provided with a recess having an inclined surface (tip surface T1) whose diameter increases toward the lower end.
  • the inclined surface may be, for example, a conical surface.
  • the tip electrode 20 may be provided with a convex portion having an outer peripheral surface corresponding to the inclined surface (tip surface T1). That is, the convex portion of the tip electrode 20 has a conical shape or a truncated cone shape.
  • the convex portion of the tip electrode 20 may be configured to be fitted to the concave portion of the lower end portion 18a, or may be configured to be detachable from the concave portion of the lower end portion 18a.
  • the external thread part 20a formed in the outer peripheral surface of a convex part and the internal thread part 18c formed in the internal peripheral surface of a recessed part are comprised so that screwing is possible.
  • the contact area between the tip electrode 20 and the lower end 18a (main body 18) is increased. Therefore, when the plasma torch 10 is energized for plasma generation and current flows between the main body 18 and the tip electrode 20, Joule heat is hardly generated at the contact portion between the main body 18 and the tip electrode 20. Therefore, since wear due to heat generation of the tip electrode 20 is further suppressed, the life of the plasma torch 10 can be further extended.
  • SYMBOLS 1 Plasma generating apparatus (molten metal heating apparatus) 10,50 ... Plasma torch, 12 ... Torch holder, 14 ... Elevator, 16 ... Operating gas source, 18 ... Main body, 18A ... Outer pipe part, 18B ... Center part, 18a ... lower end (tip), 18b ... proximal end, 18c ... female screw, 18d ... male screw, 18e ... base end, 18f ... female screw, 18g ... male screw, 20 ... tip electrode, 20A ... outer part, 20B ... Inner part, 20a ... Male thread part, 20b ... Female thread part, 22 ... Insulation coating material, 24 ... Piping, 25 ... Insulating member, 26 ...
  • Valve, 100 ... Continuous casting apparatus 101 ... Ladle, 102 ... Tundish ( (Molten metal heating device), 103 ... mold, 104 ... slab support roll, 101a ... nozzle, 102a ... storage tank, 102b ... lid, 102c ... opening, 102d ... through hole, 102e ... nozzle, F, FA, B ... flow path, H1 ⁇ H4 ... through hole, M ... melt (molten steel), P, P1 ... plasma, S ... slab, T1, T2 ... tip surface.
  • Molten metal heating device (Molten metal heating device)
  • 103 ... mold 104 ... slab support roll

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  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Plasma Technology (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Furnace Details (AREA)

Abstract

The present invention relates to a plasma torch, a plasma torch forward end electrode, and a molten metal heating device. The plasma torch 10 is used to generate a plasma P between the plasma torch 10 and a molten metal M, inside a tundish comprising a storage tank for storing the molten metal M, and a lid 102b opened upward and covering an opening of the storage tank. The plasma torch 10 comprises: a main body 18 produced from metal, so constituted as to be insertable into a through-hole 102d provided in the lid 102b, in such a manner that a lower end section 18a thereof, which is to face the molten metal M when the molten metal M is to be heat-processed by the plasma P, becomes positioned inside the tundish; and a forward end electrode 20 produced from graphite, attached to the lower end section 18a of the main body 18.

Description

プラズマトーチ、プラズマトーチ用の先端電極、及び溶湯加熱装置Plasma torch, tip electrode for plasma torch, and molten metal heating device
　本開示は、プラズマトーチ、プラズマトーチ用の先端電極、及び溶湯加熱装置に関する。 The present disclosure relates to a plasma torch, a tip electrode for the plasma torch, and a molten metal heating device.
　特許文献１は、黒鉛製のプラズマトーチを開示している。プラズマトーチは、溶融炉本体内の溶融スラグを効果的に加熱するために用いられる。プラズマトーチは、溶融炉本体の上部開口を覆うように配置された蓋の貫通孔内に挿通されている。プラズマトーチによる溶融スラグの加熱時には、プラズマトーチの下端部は溶融炉本体と蓋とで囲まれた内部空間内に位置しており、プラズマトーチの上端部は内部空間外に位置している。 Patent Document 1 discloses a plasma torch made of graphite. The plasma torch is used to effectively heat the molten slag in the melting furnace body. The plasma torch is inserted into a through-hole of a lid arranged to cover the upper opening of the melting furnace main body. When the molten slag is heated by the plasma torch, the lower end portion of the plasma torch is located in the internal space surrounded by the melting furnace main body and the lid, and the upper end portion of the plasma torch is located outside the internal space.
特開平９－１１５６６３号公報JP-A-9-115663
　プラズマを効果的に発生させるため、通常、内部空間内には不活性ガスが充填されている。すなわち、内部空間内には酸素がほとんど存在していない。そのため、溶湯が存在し高温の環境にあるものの、黒鉛と反応する酸素の量が少なく、内部空間内に位置するプラズマトーチ（トーチ下端部）は損耗し難い。一方、内部空間外には酸素が多量に存在するものの、内部空間外の温度は低いので、内部空間外に位置するプラズマトーチ（トーチ上端部）も損耗し難い。 In order to generate plasma effectively, the interior space is usually filled with an inert gas. That is, almost no oxygen is present in the internal space. Therefore, although the molten metal exists and is in a high temperature environment, the amount of oxygen that reacts with graphite is small, and the plasma torch (lower end portion of the torch) located in the internal space is less likely to be worn. On the other hand, although a large amount of oxygen exists outside the internal space, the temperature outside the internal space is low, so that the plasma torch (the torch upper end portion) located outside the internal space is not easily worn out.
　ところが、蓋の貫通孔近傍では、酸素を含む低温の外気と内部空間内の熱風とが混ざり合う。そのため、プラズマトーチのうち貫通孔に挿通されている部分は、黒鉛が酸素と反応して損耗し易い。従って、プラズマトーチの当該部分が細く抉れてしまい、プラズマトーチの寿命に影響を与える虞がある。 However, in the vicinity of the through-hole of the lid, low-temperature outside air containing oxygen and hot air in the internal space mix. Therefore, the portion of the plasma torch that is inserted through the through hole is easily worn out by the reaction of graphite with oxygen. Therefore, the portion of the plasma torch is thinned and there is a risk of affecting the life of the plasma torch.
　そのため、本開示は、長寿命化を図ることが可能なプラズマトーチ及びプラズマトーチ用の先端電極、並びにプラズマトーチの長寿命化を図ることが可能な溶湯加熱装置を説明する。 Therefore, the present disclosure describes a plasma torch capable of extending the life, a tip electrode for the plasma torch, and a molten metal heating apparatus capable of extending the life of the plasma torch.
　例１．本開示の一つの例に係るプラズマトーチは、溶湯を貯留する貯留槽と、上方に向けて開放された貯留槽の開口部を覆う蓋とを備える容器内で、溶湯との間でプラズマを発生させるプラズマトーチであって、プラズマによる溶湯の加熱処理時に溶湯に向かう先端部が容器内に位置するように、蓋に設けられた貫通孔内に挿通可能に構成された金属製の本体と、本体の先端部に取り付けられた黒鉛製の先端電極とを備える。 Example 1. A plasma torch according to an example of the present disclosure generates plasma between molten metal in a container including a storage tank that stores molten metal and a lid that covers an opening of the storage tank that is opened upward. A metal main body configured to be able to be inserted into a through-hole provided in the lid so that a tip portion toward the molten metal is located in the container at the time of heat treatment of the molten metal by plasma, And a tip electrode made of graphite attached to the tip of each.
　例１に係るプラズマトーチは、プラズマによる溶湯（溶融した液状の金属）の加熱処理時に、溶湯に向かう本体の先端部が容器内に位置するように、金属製の本体が貫通孔内に挿通可能に構成されている。そのため、蓋の貫通孔近傍に黒鉛製の先端電極が存在していない。従って、先端電極の損耗が極めて抑制される。その結果、プラズマトーチの長寿命化を図ることが可能となる。しかも、黒鉛製の先端電極を用いているので、プラズマを発生させる際に先端電極を溶湯に浸漬し、先端電極を溶湯から引き上げることにより、１００％の確率でプラズマを発生させることが可能となる。なお、全体が金属製のプラズマトーチを用いる場合、黒鉛の損耗は生じないが、当該プラズマトーチを溶湯に浸漬すると当該プラズマトーチが溶損し、溶湯の温度制御が困難となる。 In the plasma torch according to Example 1, the metal main body can be inserted into the through hole so that the tip of the main body facing the molten metal is located in the container during the heat treatment of the molten metal (molten liquid metal) by plasma. It is configured. Therefore, the graphite tip electrode does not exist in the vicinity of the through hole of the lid. Therefore, wear of the tip electrode is extremely suppressed. As a result, it is possible to extend the life of the plasma torch. In addition, since the tip electrode made of graphite is used, it is possible to generate plasma with a probability of 100% by immersing the tip electrode in the molten metal when generating plasma and pulling the tip electrode out of the molten metal. . Note that when a metal plasma torch is used as a whole, the graphite is not worn, but if the plasma torch is immersed in the molten metal, the plasma torch is melted and it becomes difficult to control the temperature of the molten metal.
　例２．例１のプラズマトーチは、本体の外周面を覆うように設けられた絶縁被覆材をさらに備えてもよい。この場合、プラズマによる溶湯の加熱処理時に本体が貫通孔内に挿通され、本体と蓋との距離が近接しても、絶縁被覆材により本体と蓋との間における放電（プラズマの発生）が防がれる。そのため、プラズマトーチを用いた溶湯の加熱処理を安全且つ安定して行うことが可能となる。なお、全体が黒鉛製のプラズマトーチの外周面に絶縁被覆材を設ける場合には、プラズマトーチと蓋との間における放電を防ぐことはできるものの、プラズマによる溶湯の加熱処理時に黒鉛自体が高温となり熱膨張するため、黒鉛との熱膨張率の差が大きい絶縁被覆材は黒鉛の外周面から剥がれてしまう。黒鉛を冷却することにより黒鉛からの絶縁被覆材の剥がれを抑制することも考えられるが、黒鉛は構造的に脆いので、黒鉛製のプラズマトーチに冷却液用の流路を設けることも困難である。 Example 2. The plasma torch of Example 1 may further include an insulating coating provided so as to cover the outer peripheral surface of the main body. In this case, the main body is inserted into the through-hole during the heat treatment of the molten metal with plasma, and even if the distance between the main body and the lid is close, the insulating coating material prevents discharge (plasma generation) between the main body and the lid. Can be removed. Therefore, it becomes possible to perform the heat treatment of the molten metal using a plasma torch safely and stably. Note that when an insulating coating is provided on the outer peripheral surface of a plasma torch made entirely of graphite, although the discharge between the plasma torch and the lid can be prevented, the graphite itself becomes hot during the heat treatment of the molten metal by plasma. Because of thermal expansion, the insulating coating material having a large difference in thermal expansion coefficient from graphite is peeled off from the outer peripheral surface of graphite. Although it may be possible to suppress the peeling of the insulating coating material from the graphite by cooling the graphite, the graphite is structurally brittle, so it is difficult to provide a flow path for the coolant in the graphite plasma torch. .
　例３．本開示の他の例に係るプラズマトーチは、金属製の本体と、本体の先端部に取り付けられた黒鉛製の先端電極と、本体の外周面を覆うように設けられた絶縁被覆材とを備える。 Example 3. A plasma torch according to another example of the present disclosure includes a metal main body, a graphite tip electrode attached to a tip portion of the main body, and an insulating coating provided to cover the outer peripheral surface of the main body. .
　例３に係るプラズマトーチでは、プラズマによる溶湯（溶融した液状の金属）の加熱処理時に、金属製の本体のうち溶湯に向かう先端部が容器内に位置するように、本体が貫通孔内に挿通された状態とすることにより、蓋の貫通孔近傍に黒鉛製の先端電極が存在しなくなる。そのため、先端電極の損耗が極めて抑制される。その結果、プラズマトーチの長寿命化を図ることが可能となる。しかも、黒鉛製の先端電極を用いているので、プラズマを発生させる際に先端電極を溶湯に浸漬し、先端電極を溶湯から引き上げることにより、１００％の確率でプラズマを発生させることが可能となる。加えて、絶縁被覆材が本体の外周面を覆うように設けられているので、プラズマによる溶湯の加熱処理時に本体が貫通孔内に挿通され、本体と蓋との距離が近接しても、絶縁被覆材により本体と蓋との間における放電（プラズマの発生）が防がれる。そのため、プラズマトーチを用いた溶湯の加熱処理を安全且つ安定して行うことが可能となる。 In the plasma torch according to Example 3, when the molten metal (molten liquid metal) is heated by plasma, the main body is inserted into the through-hole so that the tip of the metal main body facing the molten metal is located in the container. With this state, the tip electrode made of graphite does not exist in the vicinity of the through hole of the lid. Therefore, wear of the tip electrode is extremely suppressed. As a result, it is possible to extend the life of the plasma torch. In addition, since the tip electrode made of graphite is used, it is possible to generate plasma with a probability of 100% by immersing the tip electrode in the molten metal when generating plasma and pulling the tip electrode out of the molten metal. . In addition, since the insulating coating material is provided so as to cover the outer peripheral surface of the main body, the main body is inserted into the through-hole during the heat treatment of the molten metal by plasma, and even if the distance between the main body and the lid is close, insulation is provided. The covering material prevents discharge (plasma generation) between the main body and the lid. Therefore, it becomes possible to perform the heat treatment of the molten metal using a plasma torch safely and stably.
　例４．例１～例３のいずれかのプラズマトーチにおいて、先端電極は、先端部に対して着脱可能に構成されていてもよい。この場合、プラズマの生成に伴い先端電極が損耗したときには、新たな先端電極を本体に取り付ければよい。そのため、本体を再利用することができる。従って、プラズマトーチのランニングコストを軽減することが可能となる。 Example 4. In the plasma torch of any of Examples 1 to 3, the tip electrode may be configured to be detachable from the tip portion. In this case, when the tip electrode is worn with plasma generation, a new tip electrode may be attached to the main body. Therefore, the main body can be reused. Therefore, the running cost of the plasma torch can be reduced.
　例５．例４のプラズマトーチにおいて、先端電極は、先端部に対して螺合可能に構成されていてもよい。この場合、先端電極の交換を極めて簡便に行うことが可能となる。 Example 5. In the plasma torch of Example 4, the tip electrode may be configured to be screwable with the tip portion. In this case, it is possible to exchange the tip electrode very easily.
　例６．例４又は例５のプラズマトーチにおいて、先端部には、先端に向かうにつれて拡径する傾斜面を有する凹部が設けられており、先端電極には、傾斜面に対応する外周面を有する凸部が設けられており、先端電極の凸部は、先端部の凹部に嵌合可能に構成されていてもよい。この場合、先端電極と先端部（本体）との接触面積が大きくなる。そのため、プラズマ生成のためにプラズマトーチに通電し、本体と先端電極との間に電流が流れる際に、本体と先端電極との当接部においてジュール熱が発生し難くなる。従って、先端電極の発熱に伴う損耗がより抑制されるので、プラズマトーチの長寿命化をより図ることが可能となる。 Example 6. In the plasma torch of Example 4 or Example 5, the tip portion is provided with a concave portion having an inclined surface that increases in diameter toward the tip, and the tip electrode has a convex portion having an outer peripheral surface corresponding to the inclined surface. It is provided and the convex part of the tip electrode may be comprised so that fitting to the recessed part of a tip part is possible. In this case, the contact area between the tip electrode and the tip (main body) is increased. Therefore, when the plasma torch is energized for plasma generation and current flows between the main body and the tip electrode, Joule heat is hardly generated at the contact portion between the main body and the tip electrode. Therefore, since wear due to heat generation of the tip electrode is further suppressed, it is possible to further extend the life of the plasma torch.
　例７．例１～例６のプラズマトーチにおいて、本体の先端部は、本体の基端部に対して着脱可能に構成されていてもよい。この場合、本体の先端部が損傷等したときには、新たな先端部を本体の基端部に取り付ければよい。そのため、本体の基端部を再利用することができる。従って、プラズマトーチのランニングコストを軽減することが可能となる。 Example 7. In the plasma torch of Examples 1 to 6, the distal end portion of the main body may be configured to be detachable from the proximal end portion of the main body. In this case, when the tip of the main body is damaged, a new tip may be attached to the base end of the main body. Therefore, the base end portion of the main body can be reused. Therefore, the running cost of the plasma torch can be reduced.
　例８．例１～例７のいずれかのプラズマトーチにおいて、本体内には冷却液の流路が設けられていてもよい。この場合、本体が冷却液によって冷却されることで、本体の先端部に取り付けられている先端電極の冷却も行われる。そのため、先端電極の発熱に伴う損耗がさらに抑制されるので、プラズマトーチの更なる長寿命化を図ることが可能となる。 Example 8. In any of the plasma torches of Examples 1 to 7, a coolant flow path may be provided in the main body. In this case, the tip electrode attached to the tip of the main body is also cooled by cooling the main body with the coolant. For this reason, since wear due to heat generation of the tip electrode is further suppressed, it is possible to further extend the life of the plasma torch.
　例９．例１～例８のいずれかのプラズマトーチには、プラズマを発生させるための動作ガスの流路として機能する貫通孔が長手方向に沿って延びるように設けられていてもよい。この場合、動作ガスがプラズマトーチから溶湯に向けて流れるので、安定したプラズマを生成することが可能となる。 Example 9. The plasma torch of any of Examples 1 to 8 may be provided with a through hole that functions as a flow path for the working gas for generating plasma extending along the longitudinal direction. In this case, since the operating gas flows from the plasma torch toward the molten metal, stable plasma can be generated.
　例１０．例９のプラズマトーチにおいて、本体は、長手方向に沿って延びる外管部と、外管部内に挿通された中心部とを有し、先端電極は中心部の先端部に取り付けられており、外管部と中心部との間に構成される環状の間隙により貫通孔が構成されていてもよい。この場合、プラズマトーチ（先端電極）と溶湯との間にプラズマが生じた際に、先端電極の周縁が特に熱を受ける。そのため、先端電極のうち熱を受ける領域（受熱部）が比較的広くなるので、熱が分散しやすくなる。従って、先端電極の先端面における最高温度が低くなると共に、先端電極の先端面における温度分布がなだらかとなる。その結果、先端電極の発熱に伴う損耗がいっそう抑制されるので、プラズマトーチのいっそうの長寿命化を図ることが可能となる。 Example 10. In the plasma torch of Example 9, the main body has an outer tube portion extending along the longitudinal direction, and a center portion inserted through the outer tube portion, and the tip electrode is attached to the tip portion of the center portion. The through hole may be formed by an annular gap formed between the tube portion and the center portion. In this case, especially when the plasma is generated between the plasma torch (tip electrode) and the molten metal, the peripheral edge of the tip electrode receives heat. For this reason, the heat receiving region (heat receiving portion) of the tip electrode is relatively wide, so that heat is easily dispersed. Therefore, the maximum temperature on the tip surface of the tip electrode is lowered, and the temperature distribution on the tip surface of the tip electrode becomes gentle. As a result, since wear due to heat generation at the tip electrode is further suppressed, it is possible to further extend the life of the plasma torch.
　例１１．例９のプラズマトーチにおいて、本体は、長手方向に沿って延びる外管部と、外管部内に挿通された中心部とを有し、先端電極は、環状の外側部と、外側部の内側に配置可能な内側部とを有し、内側部は中心部の先端部に取り付けられており、外側部は外管部に取り付けられており、外管部及び外側部と中心部及び内側部との間に構成される環状の間隙により貫通孔が構成されていてもよい。この場合、プラズマトーチ（先端電極）と溶湯との間にプラズマが生じた際に、先端電極のうち貫通孔近傍が特に熱を受ける。そのため、先端電極のうち熱を受ける領域（受熱部）が比較的広くなるので、熱が分散しやすくなる。従って、先端電極の先端面における最高温度が低くなると共に、先端電極の先端面における温度分布がなだらかとなる。その結果、先端電極の発熱に伴う損耗がいっそう抑制されるので、プラズマトーチのいっそうの長寿命化を図ることが可能となる。 Example 11. In the plasma torch of Example 9, the main body has an outer tube portion extending along the longitudinal direction, and a central portion inserted into the outer tube portion, and the tip electrode is disposed on the inner side of the annular outer portion and the outer portion. An inner portion that can be arranged, the inner portion is attached to the distal end portion of the center portion, and the outer portion is attached to the outer tube portion, and the outer tube portion and the outer portion are connected to the center portion and the inner portion. The through hole may be formed by an annular gap formed between them. In this case, when plasma is generated between the plasma torch (tip electrode) and the molten metal, the vicinity of the through hole in the tip electrode is particularly heated. For this reason, the heat receiving region (heat receiving portion) of the tip electrode is relatively wide, so that heat is easily dispersed. Therefore, the maximum temperature on the tip surface of the tip electrode is lowered, and the temperature distribution on the tip surface of the tip electrode becomes gentle. As a result, since wear due to heat generation at the tip electrode is further suppressed, it is possible to further extend the life of the plasma torch.
　例１２．例１１のプラズマトーチにおいて、外管部及び外側部と中心部及び内側部とは、互いに電気的に絶縁されていてもよい。この場合、外管部及び外側部と中心部及び内側部とを互いに異極の電源に接続することができる。これにより、外側部と内側部との間で放電しプラズマが発生する。この状態で電源の出力を大きくしていくことにより、外側部と内側部との間で生じているプラズマが成長していく。そして、成長したプラズマが溶湯に到達したときに、外側部及び内側部と、溶湯とを互いに異極の電源に接続することにより、プラズマトーチと溶湯との間にプラズマを生成することができる。従って、プラズマトーチの先端と溶湯との距離が大きい場合でも、プラズマトーチの先端と溶湯との間にプラズマを安定して生じさせることが可能となる。 Example 12. In the plasma torch of Example 11, the outer tube portion and the outer portion, and the center portion and the inner portion may be electrically insulated from each other. In this case, the outer tube portion and the outer portion, and the center portion and the inner portion can be connected to power sources having different polarities. Thereby, plasma is generated by discharging between the outer portion and the inner portion. In this state, by increasing the output of the power source, plasma generated between the outer side and the inner side grows. When the grown plasma reaches the molten metal, the plasma can be generated between the plasma torch and the molten metal by connecting the outer and inner parts and the molten metal to power sources having different polarities. Accordingly, even when the distance between the tip of the plasma torch and the molten metal is large, it is possible to stably generate plasma between the tip of the plasma torch and the molten metal.
　例１３．例１～１２のいずれかのプラズマトーチにおいて、先端電極と先端部との当接部のうち外部に露出している領域を覆う環状の絶縁部材をさらに備えてもよい。この場合、先端電極のうち当接部の近傍において放電が生ずることが防がれる。そのため、先端部が過剰に加熱され変形等してしまうことを抑制することができる。 Example 13. The plasma torch of any of Examples 1 to 12 may further include an annular insulating member that covers a region exposed to the outside of the contact portion between the tip electrode and the tip portion. In this case, it is possible to prevent discharge from occurring in the vicinity of the contact portion of the tip electrode. Therefore, it can suppress that a front-end | tip part is heated too much and deform | transforms.
　例１４．本開示の他の例に係るプラズマトーチ用の先端電極は、容器内の溶湯をプラズマによりの加熱処理する時に、溶湯に向かう先端部が容器内に位置する金属製の本体を有し、容器の蓋に設けられた貫通孔内に挿通可能に本体が構成されているプラズマトーチ用の、黒鉛製の先端電極であって、本体の先端部に対して着脱可能に構成されている。 Example 14. A tip electrode for a plasma torch according to another example of the present disclosure has a metal main body in which a tip portion toward a molten metal is located in the container when the molten metal in the container is heated by plasma. This is a graphite tip electrode for a plasma torch in which a main body is configured to be inserted into a through-hole provided in a lid, and is configured to be detachable from a tip portion of the main body.
　例１４に係るプラズマトーチ用の先端電極は、容器内の溶湯をプラズマによる加熱処理する時に、溶湯に向かう先端部が容器内に位置する金属製の本体を有し、容器の蓋に設けられた貫通孔内に挿通可能に本体が構成されているプラズマトーチに用いられる。そのため、蓋の貫通孔近傍に黒鉛製の先端電極が存在していない。従って、先端電極の損耗が極めて抑制される。その結果、プラズマトーチの長寿命化を図ることが可能となる。しかも、例１４に係るプラズマトーチ用の先端電極は黒鉛製であるので、プラズマを発生させる際に先端電極を溶湯に浸漬し、先端電極を溶湯から引き上げることにより、１００％の確率でプラズマを発生させることが可能となる。なお、全体が金属製のプラズマトーチを用いる場合、黒鉛の損耗は生じないが、当該プラズマトーチを溶湯に浸漬すると当該プラズマトーチが溶損し、溶湯の温度制御が困難となる。 The tip electrode for a plasma torch according to Example 14 has a metal main body in which a tip portion toward the molten metal is located in the container when the molten metal in the container is heated by plasma, and is provided on the lid of the container. It is used for a plasma torch in which a main body is configured to be inserted into a through hole. Therefore, the graphite tip electrode does not exist in the vicinity of the through hole of the lid. Therefore, wear of the tip electrode is extremely suppressed. As a result, it is possible to extend the life of the plasma torch. In addition, since the tip electrode for the plasma torch according to Example 14 is made of graphite, when the plasma is generated, the tip electrode is immersed in the molten metal, and the tip electrode is pulled out of the molten metal to generate plasma with a probability of 100%. It becomes possible to make it. Note that when a metal plasma torch is used as a whole, the graphite is not worn, but if the plasma torch is immersed in the molten metal, the plasma torch is melted and it becomes difficult to control the temperature of the molten metal.
　例１５．本開示の他の例に係るプラズマトーチ用の先端電極は、外周面を覆うように絶縁被覆材が設けられた金属製の本体の先端部に対して着脱可能に構成されている。 Example 15. A tip electrode for a plasma torch according to another example of the present disclosure is configured to be attachable to and detachable from a tip portion of a metal main body provided with an insulating coating material so as to cover an outer peripheral surface.
　例１５に係るプラズマトーチ用の先端電極では、容器内の溶湯（溶融した液状の金属）をプラズマにより加熱処理する時に、金属製の本体のうち溶湯に向かう先端部が容器内に位置するように、本体が貫通孔内に挿通された状態とされる。そのため、蓋の貫通孔近傍に黒鉛製の先端電極が存在しなくなる。従って、先端電極の損耗が極めて抑制される。その結果、プラズマトーチの長寿命化を図ることが可能となる。しかも、例１５に係るプラズマトーチ用の先端電極は黒鉛製であるので、プラズマを発生させる際に先端電極を溶湯に浸漬し、先端電極を溶湯から引き上げることにより、１００％の確率でプラズマを発生させることが可能となる。加えて、絶縁被覆材が本体の外周面を覆うように設けられているので、プラズマによる溶湯の加熱処理時に本体が貫通孔内に挿通され、本体と蓋との距離が近接しても、絶縁被覆材により本体と蓋との間における放電（プラズマの発生）が防がれる。そのため、例１５に係る先端電極が取り付けられるプラズマトーチを用いた溶湯の加熱処理を安全且つ安定して行うことが可能となる。 In the tip electrode for a plasma torch according to Example 15, when the molten metal (molten liquid metal) in the container is heat-treated with plasma, the tip of the metal main body facing the molten metal is positioned in the container. The main body is inserted into the through hole. Therefore, the graphite tip electrode does not exist in the vicinity of the through hole of the lid. Therefore, wear of the tip electrode is extremely suppressed. As a result, it is possible to extend the life of the plasma torch. Moreover, since the tip electrode for the plasma torch according to Example 15 is made of graphite, plasma is generated with a probability of 100% by immersing the tip electrode in the molten metal when the plasma is generated and pulling the tip electrode out of the molten metal. It becomes possible to make it. In addition, since the insulating coating material is provided so as to cover the outer peripheral surface of the main body, the main body is inserted into the through-hole during the heat treatment of the molten metal by plasma, and even if the distance between the main body and the lid is close, insulation is provided. The covering material prevents discharge (plasma generation) between the main body and the lid. Therefore, the heat treatment of the molten metal using the plasma torch to which the tip electrode according to Example 15 is attached can be performed safely and stably.
　例１６．本開示の他の例に係る溶湯加熱装置は、溶湯を貯留する貯留槽と、上方に向けて開放された貯留槽の開口部を覆う蓋とを備える容器と、容器内で溶湯との間でプラズマを発生させるプラズマトーチとを備え、プラズマトーチは、プラズマによる溶湯の加熱処理時に溶湯に向かう先端部が容器内に位置するように、蓋に設けられた貫通孔内に挿通可能に構成された金属製の本体と、本体の先端部に取り付けられた黒鉛製の先端電極とを有する。 Example 16. A molten metal heating apparatus according to another example of the present disclosure includes a container including a storage tank that stores the molten metal, a lid that covers an opening of the storage tank that is opened upward, and the molten metal in the container. A plasma torch that generates plasma, and the plasma torch is configured to be able to be inserted into a through-hole provided in the lid so that a tip portion toward the molten metal is located in the container when the molten metal is heated by the plasma. It has a metal main body and a graphite tip electrode attached to the tip of the main body.
　例１６に係る溶湯加熱装置では、プラズマによる溶湯（溶融した液状の金属）の加熱処理時に、溶湯に向かう本体の先端部が容器内に位置するように、金属製の本体が貫通孔内に挿通可能に構成されている。そのため、蓋の貫通孔近傍に黒鉛製の先端電極が存在していない。従って、先端電極の損耗が極めて抑制される。その結果、プラズマトーチの長寿命化を図ることが可能となる。しかも、黒鉛製の先端電極を用いているので、プラズマを発生させる際に先端電極を溶湯に浸漬し、先端電極を溶湯から引き上げることにより、１００％の確率でプラズマを発生させることが可能となる。なお、全体が金属製のプラズマトーチを用いる場合、黒鉛の損耗は生じないが、当該プラズマトーチを溶湯に浸漬すると当該プラズマトーチが溶損し、溶湯の温度制御が困難となる。 In the molten metal heating apparatus according to Example 16, during the heat treatment of the molten metal (molten liquid metal) by plasma, the metal main body is inserted into the through hole so that the tip of the main body facing the molten metal is located in the container. It is configured to be possible. Therefore, the graphite tip electrode does not exist in the vicinity of the through hole of the lid. Therefore, wear of the tip electrode is extremely suppressed. As a result, it is possible to extend the life of the plasma torch. In addition, since the tip electrode made of graphite is used, it is possible to generate plasma with a probability of 100% by immersing the tip electrode in the molten metal when generating plasma and pulling the tip electrode out of the molten metal. . Note that when a metal plasma torch is used as a whole, the graphite is not worn, but if the plasma torch is immersed in the molten metal, the plasma torch is melted and it becomes difficult to control the temperature of the molten metal.
　本開示に係るプラズマトーチ、プラズマトーチ用の先端電極、及び溶湯加熱措置によれば、プラズマトーチの長寿命化を図ることが可能となる。 The plasma torch according to the present disclosure, the tip electrode for the plasma torch, and the molten metal heating measure can extend the life of the plasma torch.
図１は、連続鋳造装置の一つの例を示す図である。FIG. 1 is a diagram illustrating an example of a continuous casting apparatus. 図２は、図１のプラズマトーチの断面を示す。FIG. 2 shows a cross section of the plasma torch of FIG. 図３は、従来のプラズマトーチの断面を示す。FIG. 3 shows a cross section of a conventional plasma torch. 図４は、従来のプラズマトーチの断面を示す。FIG. 4 shows a cross section of a conventional plasma torch. 図５は、他の例に係るプラズマトーチの断面を示す。FIG. 5 shows a cross section of a plasma torch according to another example. 図６は、他の例に係るプラズマトーチの断面を示す。FIG. 6 shows a cross section of a plasma torch according to another example. 図７は、他の例に係るプラズマトーチの断面を示す。FIG. 7 shows a cross section of a plasma torch according to another example. 図８は、他の例に係るプラズマトーチの断面を示す。FIG. 8 shows a cross section of a plasma torch according to another example. 図９は、他の例に係るプラズマトーチの断面を示す。FIG. 9 shows a cross section of a plasma torch according to another example. 図１０は、他の例に係るプラズマトーチの断面を示す。FIG. 10 shows a cross section of a plasma torch according to another example. 図１１は、他の例に係るプラズマトーチの断面を示す。FIG. 11 shows a cross section of a plasma torch according to another example.
　以下に説明される本開示に係る実施形態は本発明を説明するための例示であるので、本発明は以下の内容に限定されるべきではない。以下の説明において、同一要素又は同一機能を有する要素には同一符号を用いることとし、重複する説明は省略する。 The embodiments according to the present disclosure described below are examples for explaining the present invention, and the present invention should not be limited to the following contents. In the following description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.
　まず、図１を参照して、連続鋳造装置１００の構成について説明する。連続鋳造装置１００は、取鍋１０１と、タンディッシュ１０２（溶湯加熱装置）と、鋳型１０３と、鋳片支持ロール１０４と、プラズマ発生装置１（溶湯加熱装置）を備える。 First, the configuration of the continuous casting apparatus 100 will be described with reference to FIG. The continuous casting apparatus 100 includes a ladle 101, a tundish 102 (a molten metal heating apparatus), a mold 103, a cast piece support roll 104, and a plasma generator 1 (a molten metal heating apparatus).
　取鍋１０１は、溶湯（溶鋼）Ｍを貯留する容器である。タンディッシュ１０２は、取鍋１０１の下方に配置されている。タンディッシュ１０２（容器）は、本体１０２ａ（貯留槽）と、蓋１０２ｂとを有する。本体１０２ａは、取鍋１０１の底壁に設けられたノズル１０１ａから流出した溶湯Ｍを貯留する。蓋１０２ｂは、上方に向けて開放された本体１０２ａの開口部１０２ｃを覆っている。蓋１０２ｂには、タンディッシュ１０２の内外を連通する貫通孔１０２ｄが設けられている。 The ladle 101 is a container for storing molten metal (molten steel) M. The tundish 102 is disposed below the ladle 101. The tundish 102 (container) has a main body 102a (storage tank) and a lid 102b. The main body 102 a stores the molten metal M that has flowed out from the nozzle 101 a provided on the bottom wall of the ladle 101. The lid 102b covers the opening 102c of the main body 102a opened upward. The lid 102b is provided with a through hole 102d that communicates the inside and outside of the tundish 102.
　鋳型１０３は、タンディッシュ１０２の下方に配置されている。鋳型１０３は、タンディッシュ１０２の底壁に設けられたノズル１０２ｅから流出した溶湯を冷却しながら所定形状に成形する。鋳片支持ロール１０４は、鋳型１０３から引き抜かれた鋳片Ｓを冷却しつつ搬送する。 The mold 103 is disposed below the tundish 102. The mold 103 is molded into a predetermined shape while cooling the molten metal flowing out from the nozzle 102e provided on the bottom wall of the tundish 102. The slab support roll 104 conveys the slab S drawn out from the mold 103 while cooling it.
　プラズマ発生装置１は、タンディッシュ１０２内の溶湯Ｍの温度を制御するための装置である。そのため、プラズマ発生装置１は、タンディッシュ１０２と共に、溶湯加熱装置を構成している。プラズマ発生装置１は、プラズマトーチ１０と、トーチ保持具１２と、昇降機１４と、動作ガス源１６とを備える。 The plasma generator 1 is a device for controlling the temperature of the molten metal M in the tundish 102. Therefore, the plasma generator 1 constitutes a molten metal heating device together with the tundish 102. The plasma generator 1 includes a plasma torch 10, a torch holder 12, an elevator 14, and an operating gas source 16.
　プラズマトーチ１０は、例えば直線状に延びる丸棒（直棒）である。プラズマトーチ１０の直径は、例えば５０ｍｍ～２００ｍｍ程度であってもよい。プラズマトーチ１０の長さは、例えば１０００ｍｍ～２５００ｍｍ程度であってもよい。プラズマトーチ１０の形状は、丸形以外の他の形状であってもよいし、必ずしも直線状に延びておらず屈曲していてもよい。プラズマトーチ１０は、図示しない電源に接続されており、所定の電圧（例えば１００Ｖ～５００Ｖ程度）が印加される。 The plasma torch 10 is, for example, a round bar (straight bar) extending linearly. The diameter of the plasma torch 10 may be about 50 mm to 200 mm, for example. The length of the plasma torch 10 may be about 1000 mm to 2500 mm, for example. The shape of the plasma torch 10 may be a shape other than a round shape, or may not necessarily extend linearly but may be bent. The plasma torch 10 is connected to a power source (not shown), and a predetermined voltage (for example, about 100 V to 500 V) is applied.
　プラズマトーチ１０は、図１及び図２に示されるように、金属製の本体１８と、黒鉛製の先端電極２０と、絶縁被覆材２２とを有する。本体１８には、図２に示されるように、貫通孔Ｈ１が設けられている。貫通孔Ｈ１は、例えば円形状を呈し、本体１８の軸方向（プラズマトーチ１０の長手方向）に沿って延びている。貫通孔Ｈ１の直径は、例えば１０ｍｍ程度であってもよい。本体１８には、貫通孔Ｈ１を取り囲むように、冷却液（例えば、水）の流路Ｆが設けられている。流路Ｆには、図示しない冷却液源から冷却液が供給される。冷却液は、流路Ｆ内を流通した後に排出され、例えば熱交換器によって冷却され、再び流路Ｆに供給される。冷却液が流路Ｆを循環することにより、プラズマトーチ１０全体（本体１８及び先端電極２０）が冷却される。 As shown in FIGS. 1 and 2, the plasma torch 10 includes a metal main body 18, a graphite tip electrode 20, and an insulating coating material 22. As shown in FIG. 2, the main body 18 is provided with a through hole H1. The through hole H1 has, for example, a circular shape, and extends along the axial direction of the main body 18 (longitudinal direction of the plasma torch 10). The diameter of the through hole H1 may be about 10 mm, for example. The main body 18 is provided with a flow path F of a coolant (for example, water) so as to surround the through hole H1. The coolant is supplied to the flow path F from a coolant source (not shown). The coolant is discharged after flowing through the flow path F, cooled by, for example, a heat exchanger, and supplied to the flow path F again. As the coolant circulates through the flow path F, the entire plasma torch 10 (the main body 18 and the tip electrode 20) is cooled.
　先端電極２０は、本体１８の下端部１８ａ（先端部）に取り付けられている。より詳しくは、先端電極２０は、下端部１８ａの先端面Ｔ１に取り付けられている。先端電極２０と本体１８との接触面積が大きいと、プラズマトーチ１０への通電時に先端電極２０と本体１８との当接部に生ずるジュール熱が小さくなり、プラズマトーチ１０（本体１８及び先端電極２０）の損耗を抑制できる傾向にある。先端電極２０と本体１８との接触面積をＸとし、プラズマトーチ１０を流れる電流をＹとした場合、接触面積ＸはＸ／Ｙ≦１．０［Ａ／ｍｍ２］を満たしていてもよい。なお、接触面積Ｘで電流Ｙを除算した値は、当接部を通過する電流の密度（通過電流密度）を表わしている。 The tip electrode 20 is attached to the lower end portion 18 a (tip portion) of the main body 18. More specifically, the tip electrode 20 is attached to the tip surface T1 of the lower end 18a. When the contact area between the tip electrode 20 and the main body 18 is large, the Joule heat generated at the contact portion between the tip electrode 20 and the main body 18 when the plasma torch 10 is energized becomes small, and the plasma torch 10 (the main body 18 and the tip electrode 20). ) Wear can be suppressed. When the contact area between the tip electrode 20 and the main body 18 is X and the current flowing through the plasma torch 10 is Y, the contact area X may satisfy X / Y ≦ 1.0 [A / mm 2 ]. The value obtained by dividing the current Y by the contact area X represents the density of current passing through the contact portion (passing current density).
　先端電極２０には、貫通孔Ｈ２が設けられている。貫通孔Ｈ２は、先端電極２０（プラズマトーチ１０）の軸方向に沿って延びている。貫通孔Ｈ２は、先端電極２０が本体１８の先端面Ｔ１に取り付けられた状態において、貫通孔Ｈ１と連通している。 The tip electrode 20 is provided with a through hole H2. The through hole H2 extends along the axial direction of the tip electrode 20 (plasma torch 10). The through hole H <b> 2 communicates with the through hole H <b> 1 in a state where the tip electrode 20 is attached to the tip surface T <b> 1 of the main body 18.
　絶縁被覆材２２は、本体１８の外周面の全体に設けられている。絶縁被覆材２２は、例えば、アルミナ（Ａｌ２Ｏ３）を本体１８の外周面に溶射することによって得られる。 The insulating coating material 22 is provided on the entire outer peripheral surface of the main body 18. The insulating coating material 22 is obtained, for example, by spraying alumina (Al 2 O 3 ) on the outer peripheral surface of the main body 18.
　図１に戻って、トーチ保持具１２は、本体１８（プラズマトーチ１０）の基端部１８ｂを保持する。トーチ保持具１２は、例えば、プラズマトーチ１０が鉛直軸に対して０°～３０°程度傾くようにプラズマトーチ１０を保持可能である。昇降機１４は、トーチ保持具１２を上下方向に昇降させる。そのため、トーチ保持具１２によって保持されているプラズマトーチ１０も、昇降機１４によって上下方向に昇降され、タンディッシュ１０２内の溶湯Ｍに対して近接及び離間する。プラズマトーチ１０の下端部（先端部）がタンディッシュ１０２内に位置するときにプラズマトーチ１０が昇降機１４によって上昇されると、プラズマトーチ１０は、蓋１０２ｂの貫通孔１０２ｄを通ってタンディッシュ１０２の外に移動する。プラズマトーチ１０がタンディッシュ１０２外にあるときに昇降機１４によって下降されると、プラズマトーチ１０の下端部は、蓋１０２ｂの貫通孔１０２ｄを通ってタンディッシュ１０２内に移動する。 Referring back to FIG. 1, the torch holder 12 holds the base end portion 18b of the main body 18 (plasma torch 10). The torch holder 12 can hold the plasma torch 10 such that the plasma torch 10 is inclined by about 0 ° to 30 ° with respect to the vertical axis, for example. The elevator 14 moves the torch holder 12 up and down. Therefore, the plasma torch 10 held by the torch holder 12 is also raised and lowered in the vertical direction by the elevator 14, and approaches and separates from the molten metal M in the tundish 102. When the plasma torch 10 is raised by the elevator 14 when the lower end (tip) of the plasma torch 10 is located in the tundish 102, the plasma torch 10 passes through the through-hole 102d of the lid 102b and the Move out. When the plasma torch 10 is lowered by the elevator 14 when it is outside the tundish 102, the lower end portion of the plasma torch 10 moves into the tundish 102 through the through hole 102d of the lid 102b.
　動作ガス源１６は、図１及び図２に示されるように、プラズマを発生させるための動作ガス（例えば、アルゴン、窒素等の不活性ガス）を貫通孔Ｈ１，Ｈ２に供給する。そのため、貫通孔Ｈ１，Ｈ２は、動作ガスの流路として機能する。動作ガス源１６は、配管２４を介して貫通孔Ｈ１，Ｈ２と接続されている。配管２４には、バルブ２６が設けられている。バルブ２６の開閉に応じて、動作ガス源１６からの動作ガスの貫通孔Ｈ１，Ｈ２への供給状態と非供給状態とが切り替わる。本実施形態では、動作ガス源１６、配管２４及びバルブ２６が、動作ガスを貫通孔Ｈ１，Ｈ２（プラズマトーチ１０）に供給する供給手段として機能する。 As shown in FIGS. 1 and 2, the working gas source 16 supplies a working gas (for example, an inert gas such as argon or nitrogen) for generating plasma to the through holes H1 and H2. Therefore, the through holes H1 and H2 function as operating gas flow paths. The working gas source 16 is connected to the through holes H <b> 1 and H <b> 2 via the pipe 24. The pipe 24 is provided with a valve 26. According to opening / closing of the valve 26, the supply state of the working gas from the working gas source 16 to the through holes H1, H2 and the non-supply state are switched. In the present embodiment, the operating gas source 16, the pipe 24, and the valve 26 function as supply means for supplying the operating gas to the through holes H1 and H2 (plasma torch 10).
　プラズマ発生装置１によってプラズマを発生させる場合には、まず、先端電極２０の周囲（溶湯Ｍの湯面近傍）を動作ガス雰囲気とする。具体的には、バルブ２６を開放して、動作ガス源１６から貫通孔Ｈ１，Ｈ２を介して動作ガスをタンディッシュ１０２内に供給する。また、プラズマトーチ１０に所定の電圧を印加させる。 When plasma is generated by the plasma generator 1, first, the periphery of the tip electrode 20 (near the molten metal surface of the molten metal M) is set as an operating gas atmosphere. Specifically, the valve 26 is opened, and the working gas is supplied from the working gas source 16 into the tundish 102 through the through holes H1 and H2. Further, a predetermined voltage is applied to the plasma torch 10.
　次に、この状態で、昇降機１４によってプラズマトーチ１０を溶湯Ｍに向けて降下させる。このとき、昇降機１４は、先端電極２０の全体がタンディッシュ１０２内（本体１０２ａと蓋１０２ｂとの間の内部空間内）に位置すると共に、本体１８及び絶縁被覆材２２が貫通孔１０２ｄに対向した状態となるように、プラズマトーチ１０をタンディッシュ１０２及び溶湯Ｍの湯面に対して位置決めする。これにより、先端電極２０（プラズマトーチ１０）と溶湯Ｍとの距離（ギャップ）が所定の大きさとなるまで先端電極２０を溶湯Ｍに近づける。そうすると、先端電極２０と溶湯Ｍとの間で絶縁破壊が生じ、先端電極２０と溶湯Ｍとの間に電流が流れる。これにより、図２に示されるように、先端電極２０と溶湯Ｍとの間にプラズマＰが発生する。なお、先端電極２０は、熱を受けることにより徐々に消耗（損耗）していく。 Next, in this state, the elevator 14 lowers the plasma torch 10 toward the molten metal M. At this time, in the elevator 14, the entire tip electrode 20 is located in the tundish 102 (in the internal space between the main body 102 a and the lid 102 b), and the main body 18 and the insulating coating material 22 face the through hole 102 d. The plasma torch 10 is positioned with respect to the tundish 102 and the surface of the molten metal M so as to be in a state. Thereby, the tip electrode 20 is brought close to the melt M until the distance (gap) between the tip electrode 20 (plasma torch 10) and the melt M becomes a predetermined size. Then, dielectric breakdown occurs between the tip electrode 20 and the molten metal M, and a current flows between the tip electrode 20 and the molten metal M. Thereby, as shown in FIG. 2, plasma P is generated between the tip electrode 20 and the molten metal M. The tip electrode 20 is gradually consumed (worn) by receiving heat.
　ところで、図３に示されるような全体が黒鉛製のプラズマトーチ５０を用いて、溶湯Ｍとの間にプラズマＰを発生させる場合を考える。タンディッシュ１０２内には、不活性ガスが充填されているので、タンディッシュ１０２には酸素がほとんど存在していない。そのため、溶湯Ｍが存在し高温の環境にあるものの、黒鉛と反応する酸素の量が少なく、タンディッシュ１０２内に位置するプラズマトーチ５０（プラズマトーチ５０の下端部）は損耗し難い。一方、タンディッシュ１０２外の温度は低いので、タンディッシュ１０２外には酸素が多量に存在するものの、タンディッシュ１０２外の温度は低いので、タンディッシュ１０２外に位置するプラズマトーチ５０（プラズマトーチ５０の上端部）も損耗し難い。しかしながら、蓋１０２ｂの貫通孔１０２ｄ近傍では、酸素を含む低温の外気とタンディッシュ１０２内の熱風とが混ざり合う。そのため、プラズマトーチ５０のうち貫通孔１０２ｄに挿通されている部分（プラズマトーチ５０の中間部分）は、黒鉛と酸素とが反応して損耗しやすい。従って、図３に示されるように、プラズマトーチ５０の中間部分が細く抉れてしまい、プラズマトーチ５０の寿命に影響を与える虞がある。このような抉れの発生に対して、全体が金属製のプラズマトーチを用いることも考えられる。しかしながら、金属製のプラズマトーチを用いる場合には、プラズマを発生させるためにプラズマトーチを溶湯Ｍに浸漬することができないので、プラズマの発生率が低下してしまう。金属製のプラズマトーチを溶湯に浸漬すると、溶湯Ｍの温度がプラズマトーチが溶損してしまい、溶湯Ｍの温度制御が困難となる。 Now, consider the case where plasma P is generated between the molten metal M and the entire plasma graphite torch 50 as shown in FIG. Since the tundish 102 is filled with an inert gas, oxygen is hardly present in the tundish 102. Therefore, although the molten metal M exists and is in a high temperature environment, the amount of oxygen that reacts with the graphite is small, and the plasma torch 50 (the lower end portion of the plasma torch 50) located in the tundish 102 is not easily worn. On the other hand, since the temperature outside the tundish 102 is low, a large amount of oxygen is present outside the tundish 102, but the temperature outside the tundish 102 is low, so that the plasma torch 50 (plasma torch 50 located outside the tundish 102). The upper end of the part is also difficult to wear. However, in the vicinity of the through hole 102d of the lid 102b, the low temperature outside air containing oxygen and the hot air in the tundish 102 are mixed. For this reason, the portion of the plasma torch 50 that is inserted through the through hole 102d (the intermediate portion of the plasma torch 50) is easily worn out by the reaction of graphite and oxygen. Therefore, as shown in FIG. 3, the middle portion of the plasma torch 50 may be thinned, which may affect the life of the plasma torch 50. It is also conceivable to use a metal plasma torch for the occurrence of such wrinkles. However, when a metal plasma torch is used, since the plasma torch cannot be immersed in the molten metal M in order to generate plasma, the plasma generation rate decreases. When a metal plasma torch is immersed in the molten metal, the temperature of the molten metal M is melted and the temperature control of the molten metal M becomes difficult.
　また、プラズマトーチ５０の中間部分と貫通孔１０２ｄとの距離は比較的短い。そのため、プラズマトーチ５０の周囲の雰囲気が不安定になると、図４に示されるように、プラズマトーチ５０の外周面と貫通孔１０２ｄとの間で放電してプラズマＰ１が生ずる虞がある。このような放電を防ぐために、プラズマトーチ５０の外周面に絶縁被覆材を設けることも考えられる。しかしながら、プラズマトーチ５０は黒鉛製であるので、プラズマトーチ５０による溶湯Ｍの加熱処理時に黒鉛自体が高温となり熱膨張する。黒鉛の熱膨張率は絶縁被覆材の熱膨張率よりも大きいので、絶縁被覆材はプラズマトーチ５０の外表面から剥がれてしまう。黒鉛を冷却することにより絶縁被覆材の剥がれを抑制することも考えられるが、黒鉛は構造的に脆いので、黒鉛製のプラズマトーチ５０に冷却液用の流路を設けることも困難である。 In addition, the distance between the intermediate portion of the plasma torch 50 and the through hole 102d is relatively short. Therefore, when the atmosphere around the plasma torch 50 becomes unstable, as shown in FIG. 4, there is a possibility that plasma P1 is generated due to discharge between the outer peripheral surface of the plasma torch 50 and the through hole 102d. In order to prevent such discharge, an insulating coating material may be provided on the outer peripheral surface of the plasma torch 50. However, since the plasma torch 50 is made of graphite, the graphite itself becomes a high temperature and thermally expands during the heat treatment of the molten metal M by the plasma torch 50. Since the thermal expansion coefficient of graphite is larger than the thermal expansion coefficient of the insulating coating material, the insulating coating material is peeled off from the outer surface of the plasma torch 50. Although it is conceivable to suppress peeling of the insulating coating material by cooling the graphite, it is difficult to provide a flow path for the coolant in the graphite plasma torch 50 because graphite is structurally brittle.
　しかしながら、以上のような本実施形態では、プラズマＰによる溶湯Ｍの加熱処理時に、溶湯Ｍに向かう本体１８の下端部１８ａがタンディッシュ１０２内に位置するように、金属製の本体１８が貫通孔１０２ｄ内に挿通可能に構成されている。そのため、蓋１０２ｂの貫通孔１０２ｄ近傍に黒鉛製の先端電極２０が存在していない。従って、先端電極２０の損耗が極めて抑制される。その結果、プラズマトーチ１０の長寿命化を図ることが可能となる。しかも、黒鉛製の先端電極２０を用いているので、プラズマＰを発生させる際に先端電極２０を溶湯に浸漬し、先端電極２０を溶湯Ｍから引き上げることにより、１００％の確率でプラズマＰを発生させることが可能となる。 However, in the present embodiment as described above, the metal main body 18 is a through-hole so that the lower end portion 18a of the main body 18 facing the molten metal M is positioned in the tundish 102 during the heat treatment of the molten metal M with the plasma P. It is configured to be able to be inserted into 102d. For this reason, the graphite tip electrode 20 does not exist in the vicinity of the through hole 102d of the lid 102b. Therefore, wear of the tip electrode 20 is extremely suppressed. As a result, the life of the plasma torch 10 can be extended. Moreover, since the graphite tip electrode 20 is used, when the plasma P is generated, the tip electrode 20 is immersed in the molten metal, and the tip electrode 20 is pulled up from the molten metal M, thereby generating the plasma P with a probability of 100%. It becomes possible to make it.
　本実施形態では、絶縁被覆材２２が、本体１８の外周面を覆うように設けられている。そのため、プラズマＰによる溶湯Ｍの加熱処理時に本体１８が貫通孔１０２ｄ内に挿通され、本体１８と蓋１０２ｂとの距離が近接しても、絶縁被覆材２２により本体１８と蓋１０２ｂとの間における放電（プラズマの発生）が防がれる。そのため、プラズマトーチ１０を用いた溶湯Ｍの加熱処理を安全且つ安定して行うことが可能となる。 In this embodiment, the insulating coating material 22 is provided so as to cover the outer peripheral surface of the main body 18. Therefore, even when the main body 18 is inserted into the through-hole 102d during the heat treatment of the molten metal M by the plasma P and the distance between the main body 18 and the lid 102b is close, the insulating coating material 22 causes the gap between the main body 18 and the lid 102b. Discharge (plasma generation) is prevented. Therefore, the heat treatment of the molten metal M using the plasma torch 10 can be performed safely and stably.
　本実施形態では、本体１８内に冷却液の流路Ｆが設けられている。そのため、本体１８が冷却液によって冷却されることで、本体１８の下端部１８ａに取り付けられている先端電極２０の冷却も行われる。従って、先端電極２０の発熱に伴う損耗がさらに抑制されるので、プラズマトーチ１０の更なる長寿命化を図ることが可能となる。 In the present embodiment, a coolant flow path F is provided in the main body 18. Therefore, the tip electrode 20 attached to the lower end portion 18a of the main body 18 is also cooled by cooling the main body 18 with the coolant. Therefore, since wear due to heat generation of the tip electrode 20 is further suppressed, the life of the plasma torch 10 can be further extended.
　本実施形態では、本体１８及び先端電極２０にそれぞれ、プラズマＰを発生させるための動作ガスの流路として機能する貫通孔Ｈ１，Ｈ２がプラズマトーチ１０の長手方向（軸方向）に沿って延びるように設けられている。そのため、動作ガスがプラズマトーチ１０から溶湯Ｍに向けて流れるので、安定したプラズマＰを生成することが可能となる。 In the present embodiment, the through holes H1 and H2 that function as flow paths for the working gas for generating the plasma P in the main body 18 and the tip electrode 20 extend along the longitudinal direction (axial direction) of the plasma torch 10, respectively. Is provided. Therefore, the operating gas flows from the plasma torch 10 toward the molten metal M, so that stable plasma P can be generated.
　以上、本開示に係る実施形態について詳細に説明したが、本発明の要旨の範囲内で種々の変形を上記の実施形態に加えてもよい。例えば、先端電極２０は、本体１８の下端部１８ａ（先端面Ｔ１）に対して着脱可能に構成されていてもよい。この場合、プラズマＰの生成に伴い先端電極２０が損耗したときには、新たな先端電極２０を本体１８に取り付ければよい。そのため、本体１８を再利用することができる。従って、プラズマトーチ１０のランニングコストを軽減することが可能となる。 As mentioned above, although embodiment concerning this indication was described in detail, you may add various deformation | transformation to said embodiment within the range of the summary of this invention. For example, the tip electrode 20 may be configured to be attachable to and detachable from the lower end portion 18a (tip surface T1) of the main body 18. In this case, when the tip electrode 20 is worn with the generation of the plasma P, a new tip electrode 20 may be attached to the main body 18. Therefore, the main body 18 can be reused. Therefore, the running cost of the plasma torch 10 can be reduced.
　具体的には、図５に示されるように、本体１８の下端部１８ａに形成された雌ねじ部１８ｃと、先端電極２０に設けられた雄ねじ部２０ａとが螺合可能に構成されていてもよい。また、図６に示されるように、本体１８の下端部１８ａに形成された雄ねじ部１８ｄと、先端電極２０に設けられた雌ねじ部２０ｂとが螺合可能に構成されていてもよい。これらの場合、先端電極２０の交換を極めて簡便に行うことが可能となる。特に、図６に示されるように、先端電極２０側が雌ねじ部２０ｂを有する場合、先端電極２０が大径化するので、先端電極２０の高強度化が図られる。 Specifically, as shown in FIG. 5, the internal thread portion 18 c formed on the lower end portion 18 a of the main body 18 and the external thread portion 20 a provided on the tip electrode 20 may be configured to be screwable. . Further, as shown in FIG. 6, the male screw portion 18 d formed on the lower end portion 18 a of the main body 18 and the female screw portion 20 b provided on the tip electrode 20 may be configured to be screwable. In these cases, the tip electrode 20 can be replaced very simply. In particular, as shown in FIG. 6, when the tip electrode 20 side has a female screw portion 20b, the tip electrode 20 has a large diameter, so that the tip electrode 20 can be increased in strength.
　図７に示されるように、本体１８は、その軸方向（長手方向）に沿って延びる外管部１８Ａと、外管部１８Ａ内に挿通された中心部１８Ｂとを有していてもよい。外管部１８Ａは、中心部１８Ｂとは別体である。外管部１８Ａの外周面には、絶縁被覆材２２が全体的に設けられている。外管部１８Ａの内径は、中心部１８Ｂの外径よりも大きい。そのため、外管部１８Ａと中心部１８Ｂとの間には、本体１８の軸方向（長手方向）に延びる環状の貫通孔Ｈ３が設けられている。すなわち、貫通孔Ｈ３は、中心部１８Ｂを取り囲んでいる。貫通孔Ｈ３は、動作ガス源１６に接続されており、動作ガス源１６から動作ガスが供給される。外管部１８Ａの内部及び中心部１８Ｂの内部にはそれぞれ、冷却液が流通する流路ＦＡ，ＦＢが設けられている。中心部１８Ｂの下端部１８ａには、雌ねじ部１８ｃが形成されている。雌ねじ部１８ｃは、先端電極２０に設けられた雄ねじ部２０ａと螺合可能に構成されている。そのため、先端電極２０は、中心部１８Ｂに対して着脱可能である。 7, the main body 18 may have an outer tube portion 18A extending along the axial direction (longitudinal direction) and a center portion 18B inserted into the outer tube portion 18A. The outer tube portion 18A is separate from the center portion 18B. On the outer peripheral surface of the outer tube portion 18A, an insulating coating material 22 is provided as a whole. The inner diameter of the outer tube portion 18A is larger than the outer diameter of the center portion 18B. Therefore, an annular through hole H3 extending in the axial direction (longitudinal direction) of the main body 18 is provided between the outer tube portion 18A and the center portion 18B. That is, the through hole H3 surrounds the central portion 18B. The through hole H3 is connected to the operating gas source 16, and the operating gas is supplied from the operating gas source 16. Flow paths FA and FB through which a coolant flows are provided inside the outer pipe portion 18A and the center portion 18B, respectively. An internal thread portion 18c is formed at the lower end portion 18a of the center portion 18B. The female screw portion 18 c is configured to be screwable with a male screw portion 20 a provided on the tip electrode 20. Therefore, the tip electrode 20 can be attached to and detached from the center portion 18B.
　図７に示されるプラズマトーチ１０の場合、プラズマトーチ１０（先端電極２０）と溶湯Ｍとの間にプラズマＰが生じた際に、先端電極２０の周縁が特に熱を受ける。そのため、先端電極２０のうち熱を受ける領域（受熱部）が比較的広くなるので、熱が分散しやすくなる。従って、先端電極２０の先端面Ｔ２における最高温度が低くなると共に、先端電極２０の先端面Ｔ２における温度分布がなだらかとなる。その結果、先端電極２０の発熱に伴う損耗がいっそう抑制されるので、プラズマトーチ１０のいっそうの長寿命化を図ることが可能となる。 In the case of the plasma torch 10 shown in FIG. 7, when the plasma P is generated between the plasma torch 10 (tip electrode 20) and the molten metal M, the periphery of the tip electrode 20 is particularly heated. For this reason, the heat receiving region (heat receiving portion) of the tip electrode 20 is relatively wide, so that heat is easily dispersed. Accordingly, the maximum temperature on the tip surface T2 of the tip electrode 20 is lowered, and the temperature distribution on the tip surface T2 of the tip electrode 20 is gentle. As a result, since wear due to heat generation of the tip electrode 20 is further suppressed, the life of the plasma torch 10 can be further extended.
　図８に示されるように、本体１８は、その軸方向（長手方向）に沿って延びる外管部１８Ａと、外管部１８Ａ内に挿通された中心部１８Ｂとを有しており、先端電極２０は、環状の外側部２０Ａと、外側部の内側に配置可能な内側部２０Ｂとを有していてもよい。 As shown in FIG. 8, the main body 18 has an outer tube portion 18A extending along the axial direction (longitudinal direction) thereof, and a center portion 18B inserted through the outer tube portion 18A. 20 may have an annular outer portion 20A and an inner portion 20B that can be disposed inside the outer portion.
　外管部１８Ａは、中心部１８Ｂとは別体である。外管部１８Ａの外周面及び中心部１８Ｂの外周面にはそれぞれ、絶縁被覆材２２が全体的に設けられている。外管部１８Ａの内径は、中心部１８Ｂの外径よりも大きい。そのため、外管部１８Ａと中心部１８Ｂとの間には、本体１８の軸方向（長手方向）に延びる環状の貫通孔Ｈ３が設けられている。すなわち、貫通孔Ｈ３は、中心部１８Ｂを取り囲んでいる。貫通孔Ｈ３は、動作ガス源１６に接続されており、動作ガス源１６から動作ガスが供給される。外管部１８Ａの内部及び中心部１８Ｂの内部にはそれぞれ、冷却液が流通する流路ＦＡ，ＦＢが設けられている。 The outer pipe portion 18A is separate from the center portion 18B. Each of the outer peripheral surface of the outer tube portion 18A and the outer peripheral surface of the center portion 18B is provided with an insulating coating material 22 as a whole. The inner diameter of the outer tube portion 18A is larger than the outer diameter of the center portion 18B. Therefore, an annular through hole H3 extending in the axial direction (longitudinal direction) of the main body 18 is provided between the outer tube portion 18A and the center portion 18B. That is, the through hole H3 surrounds the central portion 18B. The through hole H3 is connected to the operating gas source 16, and the operating gas is supplied from the operating gas source 16. Flow paths FA and FB through which a coolant flows are provided inside the outer pipe portion 18A and the center portion 18B, respectively.
　外側部２０Ａの内径は、内側部２０Ｂの外径よりも大きい。外側部２０Ａの外周面には、雄ねじ部２０ａが設けられている。外側部２０Ａの雄ねじ部２０ａは、外管部１８Ａの下端部１８ａに設けられた雌ねじ部１８ｃと螺合可能に構成されている。そのため、外側部２０Ａは、外管部１８Ａに対して着脱可能である。内側部２０Ｂの外周面には、雄ねじ部２０ａが設けられている。内側部２０Ｂの雄ねじ部２０ａは、中心部１８Ｂの下端部１８ａに設けられて雌ねじ部１８ｃと螺合可能に構成されている。そのため、内側部２０Ｂは、中心部１８Ｂに対して着脱可能である。外側部２０Ａ及び内側部２０Ｂがそれぞれ外管部１８Ａ及び中心部１８Ｂに対して取り付けられた状態において、外側部２０Ａと内側部２０Ｂとの間には、先端電極２０の軸方向に延びる環状の貫通孔Ｈ４が設けられる。貫通孔Ｈ４は、貫通孔Ｈ３と連通しており、貫通孔Ｈ３を通じて動作ガスが流通する。 The inner diameter of the outer portion 20A is larger than the outer diameter of the inner portion 20B. A male screw portion 20a is provided on the outer peripheral surface of the outer portion 20A. The external thread part 20A of the outer side part 20A is configured to be screwable with an internal thread part 18c provided at the lower end part 18a of the outer pipe part 18A. Therefore, the outer portion 20A can be attached to and detached from the outer tube portion 18A. A male screw portion 20a is provided on the outer peripheral surface of the inner portion 20B. The male screw portion 20a of the inner portion 20B is provided at the lower end portion 18a of the center portion 18B and is configured to be screwable with the female screw portion 18c. Therefore, the inner side part 20B is detachable with respect to the center part 18B. In a state where the outer portion 20A and the inner portion 20B are attached to the outer tube portion 18A and the center portion 18B, respectively, an annular penetration extending in the axial direction of the tip electrode 20 is provided between the outer portion 20A and the inner portion 20B. A hole H4 is provided. The through hole H4 communicates with the through hole H3, and the working gas flows through the through hole H3.
　図８に示されるプラズマトーチ１０の場合、プラズマトーチ１０（先端電極２０）と溶湯Ｍとの間にプラズマＰが生じた際に、先端電極２０のうち貫通孔Ｈ４近傍が特に熱を受ける。そのため、先端電極２０のうち熱を受ける領域（受熱部）が比較的広くなるので、熱が分散しやすくなる。従って、先端電極２０の先端面Ｔ２における最高温度が低くなると共に、先端電極２０の先端面Ｔ２における温度分布がなだらかとなる。その結果、先端電極２０の発熱に伴う損耗がいっそう抑制されるので、プラズマトーチ１０のいっそうの長寿命化を図ることが可能となる。 In the case of the plasma torch 10 shown in FIG. 8, when the plasma P is generated between the plasma torch 10 (tip electrode 20) and the molten metal M, the vicinity of the through hole H4 in the tip electrode 20 is particularly heated. For this reason, the heat receiving region (heat receiving portion) of the tip electrode 20 is relatively wide, so that heat is easily dispersed. Accordingly, the maximum temperature on the tip surface T2 of the tip electrode 20 is lowered, and the temperature distribution on the tip surface T2 of the tip electrode 20 is gentle. As a result, since wear due to heat generation of the tip electrode 20 is further suppressed, the life of the plasma torch 10 can be further extended.
　図８に示されるプラズマトーチ１０の場合、外管部１８Ａの外周面及び中心部１８Ｂの外周面にはそれぞれ、絶縁被覆材２２が全体的に設けられているので、外管部１８Ａ及び外側部２０Ａと中心部１８Ｂ及び内側部２０Ｂとは互いに電気的に絶縁されている。そのため、外管部１８Ａ及び外側部２０Ａと中心部１８Ｂ及び内側部２０Ｂとを互いに異極の電源に接続することができる。これにより、外側部２０Ａと内側部２０Ｂとの間で放電しプラズマＰが発生する。この状態で電源の出力を大きくしていくことにより、外側部２０Ａと内側部２０Ｂとの間で生じているプラズマＰが成長していく。そして、成長したプラズマＰが溶湯Ｍに到達したときに、外側部２０Ａ及び内側部２０Ｂと、溶湯Ｍとを互いに異極の電源に接続することにより、プラズマトーチ１０（先端電極２０）と溶湯Ｍとの間にプラズマＰを生成することができる。従って、プラズマトーチ１０の先端と溶湯Ｍとの距離が大きい場合でも、プラズマトーチ１０の先端と溶湯との間にプラズマＰを安定して生じさせることが可能となる。 In the case of the plasma torch 10 shown in FIG. 8, since the insulation coating material 22 is entirely provided on the outer peripheral surface of the outer tube portion 18A and the outer peripheral surface of the center portion 18B, the outer tube portion 18A and the outer portion. 20A and the central portion 18B and the inner portion 20B are electrically insulated from each other. Therefore, the outer tube portion 18A and the outer portion 20A, and the center portion 18B and the inner portion 20B can be connected to power supplies having different polarities. As a result, discharge occurs between the outer portion 20A and the inner portion 20B, and plasma P is generated. By increasing the power output in this state, the plasma P generated between the outer portion 20A and the inner portion 20B grows. When the grown plasma P reaches the molten metal M, the plasma torch 10 (tip electrode 20) and the molten metal M are connected by connecting the outer portion 20A and the inner portion 20B and the molten metal M to different power sources. Plasma P can be generated between the two. Therefore, even when the distance between the tip of the plasma torch 10 and the molten metal M is large, it is possible to stably generate the plasma P between the tip of the plasma torch 10 and the molten metal.
　図９に示されるように、下端部１８ａが本体１８の基端部１８ｅに対して着脱可能に構成されていてもよい。具体的には、下端部１８ａに形成された雌ねじ部１８ｆと、基端部１８ｅに形成された雄ねじ部１８ｇとが螺合可能に構成されている。下端部１８ａの外周面及び基端部１８ｅの外周面にはそれぞれ、絶縁被覆材２２が設けられている。下端部１８ａの先端面Ｔ１には、先端電極２０が取り付けられている。この場合、本体１８の下端部１８ａが損傷等したときには、新たな下端部１８ａを本体１８の基端部１８ｅに取り付ければよい。そのため、本体１８の基端部１８ｅを再利用することができる。従って、プラズマトーチ１０のランニングコストを軽減することが可能となる。 As shown in FIG. 9, the lower end portion 18 a may be configured to be detachable from the base end portion 18 e of the main body 18. Specifically, the internal thread part 18f formed in the lower end part 18a and the external thread part 18g formed in the base end part 18e can be screwed together. An insulating coating material 22 is provided on each of the outer peripheral surface of the lower end portion 18a and the outer peripheral surface of the base end portion 18e. A tip electrode 20 is attached to the tip surface T1 of the lower end 18a. In this case, when the lower end 18 a of the main body 18 is damaged, a new lower end 18 a may be attached to the base end 18 e of the main body 18. Therefore, the base end portion 18e of the main body 18 can be reused. Therefore, the running cost of the plasma torch 10 can be reduced.
　図１０に示されるように、プラズマトーチ１０は、絶縁部材２５をさらに備えていてもよい。絶縁部材２５は、円環状を呈しており、先端電極２０と下端部１８ａとの当接部のうち外部に露出している領域を覆っている。当接部には、絶縁部材２５の外形に対応した凹溝が形成されている。そのため、絶縁部材２５を当接部に取り付ける際には、まず、先端電極２０と下端部１８ａとが取り外されている状態で、下端部１８ａ側の凹溝に絶縁部材２５を嵌め込む。次に、先端電極２０の雄ねじ部２０ａを下端部１８ａの雌ねじ部１８ｃに螺合する。これにより、絶縁部材２５は、先端電極２０及び下端部１８ａの凹溝内において保持される。この場合、先端電極２０のうち当接部の近傍において放電が生ずることが防がれる。そのため、下端部１８ａが過剰に加熱され変形等してしまうことを抑制することができる。 As shown in FIG. 10, the plasma torch 10 may further include an insulating member 25. The insulating member 25 has an annular shape and covers a region exposed to the outside in the contact portion between the tip electrode 20 and the lower end portion 18a. A concave groove corresponding to the outer shape of the insulating member 25 is formed in the contact portion. Therefore, when attaching the insulating member 25 to the contact portion, first, the insulating member 25 is fitted into the concave groove on the lower end portion 18a side with the tip electrode 20 and the lower end portion 18a removed. Next, the male screw portion 20a of the tip electrode 20 is screwed into the female screw portion 18c of the lower end portion 18a. Thereby, the insulating member 25 is held in the recessed grooves of the tip electrode 20 and the lower end portion 18a. In this case, it is possible to prevent discharge from occurring in the vicinity of the contact portion of the tip electrode 20. Therefore, it is possible to prevent the lower end portion 18a from being excessively heated and deformed.
　図１１に示されるように、下端部１８ａには、下端に向かうにつれて拡径する傾斜面（先端面Ｔ１）を有する凹部が設けられていてもよい。傾斜面は、例えば円錐面であってもよい。先端電極２０には、傾斜面（先端面Ｔ１）に対応する外周面を有する凸部が設けられていてもよい。すなわち、先端電極２０の凸部は、円錐状又は円錐台状を呈している。先端電極２０の凸部は、下端部１８ａの凹部に対して嵌合可能に構成されていてもよく、下端部１８ａの凹部に対して着脱可能に構成されていてもよい。図１１においては、凸部の外周面に形成された雄ねじ部２０ａと、凹部の内周面に形成された雌ねじ部１８ｃとが螺合可能に構成されている。この場合、先端電極２０と下端部１８ａ（本体１８）との接触面積が大きくなる。そのため、プラズマ生成のためにプラズマトーチ１０に通電し、本体１８と先端電極２０との間に電流が流れる際に、本体１８と先端電極２０との当接部においてジュール熱が発生し難くなる。従って、先端電極２０の発熱に伴う損耗がより抑制されるので、プラズマトーチ１０の長寿命化をより図ることが可能となる。 As shown in FIG. 11, the lower end portion 18a may be provided with a recess having an inclined surface (tip surface T1) whose diameter increases toward the lower end. The inclined surface may be, for example, a conical surface. The tip electrode 20 may be provided with a convex portion having an outer peripheral surface corresponding to the inclined surface (tip surface T1). That is, the convex portion of the tip electrode 20 has a conical shape or a truncated cone shape. The convex portion of the tip electrode 20 may be configured to be fitted to the concave portion of the lower end portion 18a, or may be configured to be detachable from the concave portion of the lower end portion 18a. In FIG. 11, the external thread part 20a formed in the outer peripheral surface of a convex part and the internal thread part 18c formed in the internal peripheral surface of a recessed part are comprised so that screwing is possible. In this case, the contact area between the tip electrode 20 and the lower end 18a (main body 18) is increased. Therefore, when the plasma torch 10 is energized for plasma generation and current flows between the main body 18 and the tip electrode 20, Joule heat is hardly generated at the contact portion between the main body 18 and the tip electrode 20. Therefore, since wear due to heat generation of the tip electrode 20 is further suppressed, the life of the plasma torch 10 can be further extended.
　１…プラズマ発生装置（溶湯加熱装置）、１０，５０…プラズマトーチ、１２…トーチ保持具、１４…昇降機、１６…動作ガス源、１８…本体、１８Ａ…外管部、１８Ｂ…中心部、１８ａ…下端部（先端部）、１８ｂ…基端部、１８ｃ…雌ねじ部、１８ｄ…雄ねじ部、１８ｅ…基端部、１８ｆ…雌ねじ部、１８ｇ…雄ねじ部、２０…先端電極、２０Ａ…外側部、２０Ｂ…内側部、２０ａ…雄ねじ部、２０ｂ…雌ねじ部、２２…絶縁被覆材、２４…配管、２５…絶縁部材、２６…バルブ、１００…連続鋳造装置、１０１…取鍋、１０２…タンディッシュ（溶湯加熱装置）、１０３…鋳型、１０４…鋳片支持ロール、１０１ａ…ノズル、１０２ａ…貯留槽、１０２ｂ…蓋、１０２ｃ…開口部、１０２ｄ…貫通孔、１０２ｅ…ノズル、Ｆ，ＦＡ，ＦＢ…流路、Ｈ１～Ｈ４…貫通孔、Ｍ…溶湯（溶鋼）、Ｐ，Ｐ１…プラズマ、Ｓ…鋳片、Ｔ１，Ｔ２…先端面。 DESCRIPTION OF SYMBOLS 1 ... Plasma generating apparatus (molten metal heating apparatus) 10,50 ... Plasma torch, 12 ... Torch holder, 14 ... Elevator, 16 ... Operating gas source, 18 ... Main body, 18A ... Outer pipe part, 18B ... Center part, 18a ... lower end (tip), 18b ... proximal end, 18c ... female screw, 18d ... male screw, 18e ... base end, 18f ... female screw, 18g ... male screw, 20 ... tip electrode, 20A ... outer part, 20B ... Inner part, 20a ... Male thread part, 20b ... Female thread part, 22 ... Insulation coating material, 24 ... Piping, 25 ... Insulating member, 26 ... Valve, 100 ... Continuous casting apparatus, 101 ... Ladle, 102 ... Tundish ( (Molten metal heating device), 103 ... mold, 104 ... slab support roll, 101a ... nozzle, 102a ... storage tank, 102b ... lid, 102c ... opening, 102d ... through hole, 102e ... nozzle, F, FA, B ... flow path, H1 ~ H4 ... through hole, M ... melt (molten steel), P, P1 ... plasma, S ... slab, T1, T2 ... tip surface.

Claims (16)

  1. 　溶湯を貯留する貯留槽と、上方に向けて開放された前記貯留槽の開口部を覆う蓋とを備える容器内で、溶湯との間でプラズマを発生させるプラズマトーチであって、
    　プラズマによる溶湯の加熱処理時に溶湯に向かう先端部が前記容器内に位置するように、前記蓋に設けられた貫通孔内に挿通可能に構成された金属製の本体と、
    　前記本体の前記先端部に取り付けられた黒鉛製の先端電極とを備える、プラズマトーチ。     A plasma torch for generating plasma between the molten metal in a container including a storage tank for storing the molten metal and a lid covering the opening of the storage tank opened upward.
    A metal main body configured to be able to be inserted into a through-hole provided in the lid, so that a tip portion directed to the molten metal at the time of the heat treatment of the molten metal by plasma is located in the container;
    A plasma torch comprising a graphite tip electrode attached to the tip of the main body.
  2. 　前記本体の外周面を覆うように設けられた絶縁被覆材をさらに備える、請求項１に記載のプラズマトーチ。 The plasma torch according to claim 1, further comprising an insulating coating provided so as to cover an outer peripheral surface of the main body.
  3. 　金属製の本体と、
    　前記本体の先端部に取り付けられた黒鉛製の先端電極と、
    　前記本体の外周面を覆うように設けられた絶縁被覆材とを備える、プラズマトーチ。     A metal body,
    A graphite tip electrode attached to the tip of the body;
    A plasma torch comprising an insulating coating provided to cover the outer peripheral surface of the main body.
  4. 　前記先端電極は、前記先端部に対して着脱可能に構成されている、請求項１～３のいずれか一項に記載のプラズマトーチ。 The plasma torch according to any one of claims 1 to 3, wherein the tip electrode is configured to be detachable from the tip portion.
  5. 　前記先端電極は、前記先端部に対して螺合可能に構成されている、請求項４に記載のプラズマトーチ。 The plasma torch according to claim 4, wherein the tip electrode is configured to be screwable with the tip portion.
  6. 　前記先端部には、先端に向かうにつれて拡径する傾斜面を有する凹部が設けられており、
    　前記先端電極には、前記傾斜面に対応する外周面を有する凸部が設けられており、
    　前記先端電極の前記凸部は、前記先端部の前記凹部に嵌合可能に構成されている、請求項４又は５に記載のプラズマトーチ。     The tip is provided with a recess having an inclined surface that increases in diameter toward the tip,
    The tip electrode is provided with a convex portion having an outer peripheral surface corresponding to the inclined surface,
    The plasma torch according to claim 4 or 5, wherein the convex portion of the tip electrode is configured to be fitted into the concave portion of the tip portion.
  7. 　前記本体の前記先端部は、前記本体の基端部に対して着脱可能に構成されている、請求項１～６のいずれか一項に記載のプラズマトーチ。 The plasma torch according to any one of claims 1 to 6, wherein the distal end portion of the main body is configured to be detachable from a proximal end portion of the main body.
  8. 　前記本体内には冷却液の流路が設けられている、請求項１～７のいずれか一項に記載のプラズマトーチ。 The plasma torch according to any one of claims 1 to 7, wherein a cooling fluid flow path is provided in the main body.
  9. 　プラズマを発生させるための動作ガスの流路として機能する貫通孔が長手方向に沿って延びるように設けられている、請求項１～８のいずれか一項に記載のプラズマトーチ。 The plasma torch according to any one of claims 1 to 8, wherein a through hole functioning as a flow path of a working gas for generating plasma extends along the longitudinal direction.
  10. 　前記本体は、長手方向に沿って延びる外管部と、前記外管部内に挿通された中心部とを有し、
    　前記先端電極は前記中心部の先端部に取り付けられており、
    　前記外管部と前記中心部との間に構成される環状の間隙により前記貫通孔が構成されている、請求項９に記載のプラズマトーチ。     The main body has an outer tube portion extending along a longitudinal direction, and a central portion inserted into the outer tube portion,
    The tip electrode is attached to the tip of the central portion;
    The plasma torch according to claim 9, wherein the through-hole is configured by an annular gap configured between the outer tube portion and the center portion.
  11. 　前記本体は、長手方向に沿って延びる外管部と、前記外管部内に挿通された中心部とを有し、
    　前記先端電極は、環状の外側部と、前記外側部の内側に配置可能な内側部とを有し、
    　前記内側部は前記中心部の先端部に取り付けられており、
    　前記外側部は前記外管部に取り付けられており、
    　前記外管部及び前記外側部と前記中心部及び前記内側部との間に構成される環状の間隙により前記貫通孔が構成されている、請求項９に記載のプラズマトーチ。     The main body has an outer tube portion extending along a longitudinal direction, and a central portion inserted into the outer tube portion,
    The tip electrode has an annular outer portion and an inner portion that can be disposed inside the outer portion,
    The inner part is attached to the tip of the central part;
    The outer portion is attached to the outer tube portion;
    The plasma torch according to claim 9, wherein the through hole is configured by an annular gap formed between the outer tube portion and the outer portion, and the center portion and the inner portion.
  12. 　前記外管部及び前記外側部と前記中心部及び前記内側部とは、互いに電気的に絶縁されている、請求項１１に記載のプラズマトーチ。 The plasma torch according to claim 11, wherein the outer tube portion, the outer portion, the center portion, and the inner portion are electrically insulated from each other.
  13. 　前記先端電極と前記先端部との当接部のうち外部に露出している領域を覆う環状の絶縁部材をさらに備える、請求項１～１２のいずれか一項に記載のプラズマトーチ。 The plasma torch according to any one of claims 1 to 12, further comprising an annular insulating member that covers a region exposed to the outside of a contact portion between the tip electrode and the tip portion.
  14. 　容器内の溶湯をプラズマにより加熱処理する時に、溶湯に向かう先端部が前記容器内に位置する金属製の本体を有し、前記容器の蓋に設けられた貫通孔内に挿通可能に前記本体が構成されているプラズマトーチ用の、黒鉛製の先端電極であって、
    　前記本体の前記先端部に対して着脱可能に構成された、先端電極。     When the molten metal in the container is heat-treated with plasma, the tip part toward the molten metal has a metal main body located in the container, and the main body is capable of being inserted into a through hole provided in the lid of the container. A tip electrode made of graphite for a plasma torch,
    A tip electrode configured to be detachable from the tip portion of the main body.
  15. 　外周面を覆うように絶縁被覆材が設けられた金属製の本体の先端部に対して着脱可能に構成された、プラズマトーチ用の黒鉛製の先端電極。 A graphite tip electrode for a plasma torch configured to be detachable from the tip of a metal main body provided with an insulating coating so as to cover the outer peripheral surface.
  16. 　溶湯を貯留する貯留槽と、上方に向けて開放された前記貯留槽の開口部を覆う蓋とを備える容器と、
    　前記容器内で溶湯との間でプラズマを発生させるプラズマトーチとを備え、
    　前記プラズマトーチは、
    　　プラズマによる溶湯の加熱処理時に溶湯に向かう先端部が前記容器内に位置するように、前記蓋に設けられた貫通孔内に挿通可能に構成された金属製の本体と、
    　　前記本体の前記先端部に取り付けられた黒鉛製の先端電極とを有する、溶湯加熱装置。     A container comprising a storage tank for storing molten metal, and a lid that covers the opening of the storage tank opened upward;
    A plasma torch for generating plasma between the molten metal in the container,
    The plasma torch is
    A metal main body configured to be able to be inserted into a through-hole provided in the lid, so that a tip portion directed to the molten metal at the time of the heat treatment of the molten metal by plasma is located in the container;
    A molten metal heating device having a graphite tip electrode attached to the tip of the main body.
PCT/JP2018/005289 2017-03-07 2018-02-15 Plasma torch, plasma torch forward end electrode, and molten metal heating device WO2018163747A1 (en)

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