JP2007200562A - CONTINUOUS HEAT TREATMENT DEVICE OF Bi-BASED OXIDE SUPERCONDUCTIVE WIRE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously manufacture a long Bi-based oxide superconductive wire or twisted wire conductor excelling in characteristics at a low cost without adding distortion. <P>SOLUTION: The wire or twisted wire conductor 9 after a forming process which is wound around a delivery device 3 is mounted on a transport device 5, passes through a preliminary heating chamber 6, heater zones 2a, 2b and 2c of a heat treatment furnace 2 and a slow cooling chamber 7, and is wound around a winding device 4. The temperature and the transport speed of the wire or twisted wire conductor 9 are controlled to secure a slow cooling process from a temperature 50°C lower than a partial dissolution point to a temperature 20°C higher than it in an oxidizing environment up to 10°C below a condensation temperature. The delivery speed of the delivery device 3, the winding speed of the winding device 4 and the transport speed of the transport device 5 are so controlled by a control device 8 that additional distortion to the wire or twisted wire conductor 9 and flexural distortion thereof are set not greater than 0.1% and not greater than 0.1%, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an oxide superconductor heat treatment apparatus, and more particularly to improvement of a continuous heat treatment apparatus for Bi (2212) -based oxide superconducting wire used for superconducting magnets and power equipment.

  Conventionally, as an oxide superconductor, Bi (2212) oxide superconductor (Bi: Sr: Ca: Cu = 2: 2: 1: 2 molar ratio) and Bi (2223) oxide superconductor (Bi: Sr: Ca: Cu = 2: 2: 2: 3 molar ratio) has been successfully formed into wires, and these wires are produced by a so-called silver sheath method (Powder in Tube Method). In this method, a raw material powder of a superconducting material is filled in a silver or silver alloy pipe, and this is subjected to diameter reduction processing or further rolled to form a round cross-section or tape shape, and then subjected to heat treatment. The raw material powder is made superconductive.

  As the material used for the sheath material, silver or a silver alloy is selected from the viewpoints of no reactivity with the superconducting powder, no oxidation at a high temperature, and a high oxygen diffusion rate. In this way, an oxide superconducting wire in which a large number of thin oxide superconductor filaments are arranged in silver or a silver alloy is manufactured. Aggregate conductors are manufactured.

  In order to produce a superconductor by this process, it is essential to perform heat treatment after cold working. This heat treatment is performed by winding together with a heat-resistant spacer or gaps so as not to contact each other, forming concentric circles in a pancake shape, or winding them in a cylindrical firing drum shape, and heat treatment using an electric furnace for heat treatment. It has been subjected.

  In the resistance heating method using the batch electric furnace described above, the furnace body is heated by the heat generated by the resistance heating element and is kept warm by the heat insulating material around the furnace. First, the furnace body having a large heat capacity is heated. Further, after completion of the heat treatment, the cooling rate of the sample is also controlled by the cooling rate of the furnace body, so that it is difficult to control the cooling rate.

  Therefore, in this case, as the wire becomes longer, the electric furnace becomes larger and the cost increases, and the manufacturing efficiency is lowered. Further, when a Bi (2212) -based oxide superconducting wire is manufactured by the above silver sheath method, the synthesis temperature in the heat treatment for generating the oxide superconductor after cold working is narrow in the appropriate temperature range, for example, the temperature range Must be controlled to ± 1 to 2 ° C. There is a problem that temperature control becomes difficult as the electric furnace becomes larger.

  The difficulty of the above severe temperature control increases remarkably as the electric furnace becomes larger as the wire becomes longer. In addition, in order to support the weight of a long wire at high temperatures, a large wire support is required. From the viewpoint of heat resistance, this wire support is formed of heat resistant stainless steel, ceramic molded body, etc. ing.

Since the above-mentioned wire rod support has a large heat capacity, for example, the wire rod support is formed in a cylindrical shape, and a wire containing an element constituting a long oxide superconductor is wound around the outer periphery in a solenoid shape to perform heat treatment. When applied, the thermal behavior of the wire is greatly influenced by the thermal behavior and heat capacity of the wire support, and there is a drawback that it becomes difficult to control the temperature of the wire to be heat-treated, making it difficult to obtain a desired heat treatment pattern. In the production of a Bi (2212) -based oxide superconducting wire whose cooling conditions must be strictly controlled, it becomes extremely difficult to obtain a superconducting wire having excellent characteristics.
In addition, when heat-resistant stainless steel is used as the wire support, distortion is applied during heat treatment due to the difference in thermal expansion coefficient between the wire wound on the wire support and the oxide superconductor, resulting in deterioration of the superconducting properties and the sheath. In addition to the problem that the material is cracked, there is a problem that the superconductor is contaminated by the diffusion of the elements constituting the wire support into the wire, and the superconducting properties are deteriorated.

  As means for solving the above problems, the elements constituting the long oxide superconductor are included at a predetermined molar ratio outside the winding frame in which the ceramic layer is provided on the surface of the cylindrical member made of a heat-resistant metal material. After winding the wire containing the raw material powder into a solenoid shape, heat treatment is performed to prevent heat from flowing from the wire support, enabling heat treatment control with a predetermined heat treatment pattern, and from the wire support There is known a method for producing a long oxide superconducting wire having excellent superconducting properties by preventing diffusion of elements constituting the wire support to the wire (see, for example, Patent Document 1).

  On the other hand, a method in which a long wire is continuously heated as compared to the batch heating method has been studied. For example, it has a heating means and a control mechanism for controlling the temperature of the heating means, and runs on one or more strips of a long wire having a superconductor forming portion that becomes an oxide superconductor by heat treatment inside the heating means. There is known a continuous heat treatment apparatus for an oxide superconducting wire in which two or more heat treatment units are provided in the running direction of the long wire by heating the wire to form a long oxide superconducting wire. (For example, refer to Patent Document 2).

JP 2004-200098 A JP-A-9-147647

  In the resistance heating method using the batch electric furnace described above, it is possible to some extent to prevent the heat inflow from the wire support and the diffusion of the elements constituting the wire support from the wire support to the wire. However, as the length of the wire increases, the size of the electric furnace increases and the cost increases, the production efficiency decreases, and the problem that the temperature control becomes difficult as the electric furnace increases in size still remains. It was.

  Further, in the above-described continuous heat treatment apparatus, when the heat treatment units are arranged in the horizontal direction, tension is applied so that the oxide superconducting wire does not come into contact with the heating means when being sent out in the horizontal direction (paragraph of the same publication). 0029), a long oxide superconducting wire traveling between the delivery device and the winding device has to be distorted, which may deteriorate the characteristics of the Bi-based oxide superconducting wire.

  The present invention has been made to solve the above problems, and enables strict temperature control without adding strain to a long oxide superconducting wire or conductor, and has excellent superconducting characteristics at low cost. An object of the present invention is to provide a continuous heat treatment apparatus for a Bi-based oxide superconducting wire capable of continuously producing a Bi-based oxide superconducting wire.

  In order to solve the above problems, the Bi-based oxide superconducting wire continuous heat treatment apparatus of the present invention is a wire obtained by filling a raw material powder constituting a Bi-based oxide superconducting material into a silver or silver alloy sheath and molding it. Or a continuous heat treatment apparatus for producing an oxide superconducting wire or an oxide superconductor by heat-treating a conductor in which a plurality of these wires are twisted, the heat treatment apparatus comprising a feeding device and a winding device; A heat treatment furnace disposed between the soldering device and the winding device, and a wire or conductor transfer device disposed in the heat treatment furnace, wherein the heat treatment furnace comprises a Bi (2212) oxide superconductor. It includes a heat treatment zone that can be controlled to a heat treatment temperature including a partial melting temperature region for generation, and the wire or conductor placed on the wire or conductor transfer device disposed in the heat treatment furnace is in an oxidizing atmosphere. It is obtained so as to comprise a heat treatable atmosphere control means.

  In the case of a wire processed by filling a raw material powder in a silver alloy sheath, one or more of Mg, Ni, Sb, Mn, Cu, and Al are added to 0.01 to 1 at% of silver of 4N or more. Most of these elements are oxidized during the heat treatment for producing the Bi (2212) -based oxide superconductor and dispersed in silver, thereby increasing the mechanical strength of silver. The shape of the wire may be any of a round wire, a flat wire, and a tape wire, and the superconducting filament arrangement structure and the number of filaments are not limited. In the case of a conductor in which a plurality of wires are twisted together, it can be applied to any of a primary twisted and higher-order twisted conductor, an assembled conductor, a Rutherford-type conductor, a conduit-type conductor, and a stabilizing conductor with a stabilizing layer. .

  According to the present invention, since a long silver sheath wire or conductor can be continuously heat-treated by strictly controlling the appropriate temperature for heat treatment, a large electric furnace is not required and the wire or conductor can be manufactured at low cost. Therefore, it is possible to produce a wire or conductor having excellent superconducting characteristics without adding strain, and its practical value is great.

  As described above, the present invention is a heat treatment zone in which a wire or a stranded wire conductor after molding is placed on a transfer device disposed in a heat treatment furnace and controlled to a heat treatment temperature including a partial melting temperature region. The heat treatment furnace can be heated to a heat treatment temperature including a partial melting temperature region for producing a Bi (2212) -based oxide superconductor. It is preferable to comprise a plurality of heater zones whose temperature can be controlled with a predetermined heat treatment pattern including a heat treatment zone that can be controlled.

  The heat treatment furnace is formed of, for example, a tubular furnace, and the shape of the core portion through which the wire or the assembly conductor passes may be round, square, and other shapes.

  The heat treatment pattern includes a heating region in which the oxygen concentration is 50% or more and the heat treatment temperature is higher than the melting point of the Bi (2212) -based oxide superconductor and heated at a temperature lower than 20 ° C. exceeding the melting point. It is preferable to do.

  For controlling the atmosphere in the furnace, it is possible to adopt a method in which the entire furnace is covered with a casing and sealed to make the whole atmosphere the same. Alternatively, gas may be blown directly into the furnace, and the oxygen concentration in the furnace may be controlled by the flow rate. In this latter case, it is necessary to take measures to prevent the temperature in the furnace from being changed by the introduced oxygen. Examples of this measure include a method in which a preliminary chamber is provided to heat the gas and a method in which a radiant plate is placed in a heat treatment furnace to prevent convection.

  In addition, the heat treatment apparatus preferably includes a preheating chamber on the inlet side and a slow cooling chamber on the outlet side of the conveyance path of the wire or conductor conveyed in the heat treatment furnace, and in this case, the preheating chamber is Bi (2212). ) A means for heating to a temperature of several tens of degrees below the melting point of the oxide superconductor is provided, and the annealing chamber is provided with a means for cooling to 10 ° C. below the solidification temperature of the Bi (2212) oxide superconductor. To do.

  When the preheating chamber and the slow cooling chamber are provided, the lengths of the preheating chamber, the heat treatment zone, and the slow cooling chamber are 50 ° C. lower than the time during which the wire or conductor is sufficiently heated and the partial melting point. The time to raise the temperature from below 20 ° C. to below the temperature is desirably 10 to 30 ° C./h, and the time for cooling the subsequent slow cooling process to 0.1 ° C. to 10 ° C./h from the solidification temperature to 10 ° C. Designed to.

  The conveyance of the wire or conductor is preferably a structure that applies as little mechanical stress as possible to the wire or conductor. If necessary, a mechanism for controlling tension is installed in the delivery mechanism. The carrier support may be anything that maintains its shape and mechanical strength in an oxidizing atmosphere and temperature of heat treatment. For example, the carrier device is spanned between a pair of synchronously rotating drive rollers and these drive rollers. It is preferable to use an endless belt made of a net-like body formed of a heat-resistant metal material. The feeding device, the winding device and the conveying device have a tensile strain of 0.1% on the wire constituting the wire or conductor. It is preferable to include a control device that controls the feeding speed, the winding speed, and the conveying speed so that the bending strain amount is 0.1% or less.

The endless belt can be prepared by knitting a linear body made of stainless steel, Hastelloy, Inconel, or other heat-resistant metal material, and ZrO ₂ , Al ₂ O ₃ as a diffusion preventing layer on the surface of the linear body. A ceramic-coated material such as MgO can be used.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of a continuous heat treatment apparatus for Bi-based oxide superconducting wire of the present invention.

  In the figure, a continuous heat treatment apparatus 1 for a Bi-based oxide superconducting wire includes a heat treatment furnace 2 comprising a tubular furnace, a feeding device 3, a winding device 4, a conveying device 5, a preheating chamber 6, a slow cooling chamber 7, and a control. The apparatus 8 is mainly configured.

  The heat treatment furnace 2 is disposed between the feeding device 3 and the winding device 4, and fills a silver or silver alloy sheath with a raw material powder constituting a Bi-based oxide superconducting material that is a material to be heat treated. The preheating chamber 6 is disposed on the entrance side of the heat treatment furnace 2 in the traveling direction of the conductor 9 formed by twisting the wires 9 formed by twisting them, and the annealing chamber 7 is disposed on the exit side. . The preheating chamber 6 includes means (not shown) for heating to a temperature of several tens of degrees below the melting point of the Bi (2212) oxide superconductor, for example, a temperature lower than the melting point by 50 ° C., and the slow cooling chamber 7 is And a means (not shown) for cooling to 10 ° C. or lower than the solidification temperature of the Bi (2212) oxide superconductor.

  An atmosphere gas is supplied from the gas supply device 10 to the preheating chamber 6 to control the inside of the heat treatment furnace 2 to an oxidizing atmosphere. As for the atmosphere in the furnace, the entire heat treatment furnace 2 may be covered with the casing 11, and the inside thereof may be made the same atmosphere. In this case, the preheating chamber 6 may be omitted.

  The heat treatment furnace 2 includes a plurality of heater zones 2a that can be controlled in temperature by a predetermined heat treatment pattern including a heat treatment zone that can be controlled to a heat treatment temperature including a partial melting temperature region for generating a Bi (2212) -based oxide superconductor. 2b and 2c. For example, the oxygen concentration is 50% or more, and the heat treatment temperature is higher than the melting point of the Bi (2212) -based oxide superconductor and is heated at a temperature lower than 20 ° C. exceeding this melting point. It is controlled by a heat treatment pattern including a heating region.

The conveying device 5 is disposed in the heat treatment furnace 2 and is disposed from the preheating chamber 6 through the heat treatment furnace 2 and the slow cooling chamber 7 to just before the winding drum of the winding device 4.
The conveying device 5 is composed of a pair of synchronously rotating drive rollers (not shown) and an endless belt made of a net-like material stretched between these drive rollers. The endless belt has ZrO _{2 on the} surface. It is made by knitting a linear body made of stainless steel, Hastelloy, Inconel or other heat-resistant metal material coated with ceramics such as Al ₂ O ₃ and MgO as a diffusion preventing layer.

  In the Bi-based oxide superconducting wire continuous heat treatment apparatus 1 described above, the molded wire or the stranded wire conductor 9 wound on the drum of the delivery device 3 is placed on the transport device 5 and preheated. It passes through the chamber 6, the heater zones 2 a, 2 b, 2 c of the heat treatment furnace 2 and the annealing chamber 7, and is wound on the drum of the winding device 4. The wire or stranded wire conductor 9 is in an oxidizing atmosphere while passing through the preheating chamber 6, the heat treatment furnace 2 and the slow cooling chamber 7, for example, from a temperature 50 ° C. lower than the partial melting point to a temperature lower than 20 ° C. The temperature and the conveying speed are controlled so as to secure the time for raising at 10 to 30 ° C./h, and the subsequent slow cooling process, for example, cooling at 0.1 ° C. to 10 ° C./h to 10 ° C. or less. The

  Further, the feeding device 3, the winding device 4 and the conveying device 5 are such that the additional strain on the wire or the stranded wire conductor 9 is 0.1% or less and the amount of bending strain is 0.1% or less. The control device 8 controls the sending speed of the sending device 3, the winding speed of the winding device 4, and the conveying speed of the conveying device 5.

  According to the continuous heat treatment apparatus for Bi-based oxide superconducting wire of the present invention, a long Bi (2212) -based oxide superconducting wire having excellent superconducting properties used in superconducting magnets and power equipment can be obtained at low cost. It becomes possible to manufacture continuously.

It is a schematic sectional drawing which shows one Example of the continuous heat processing apparatus of Bi type oxide superconducting wire of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Continuous heat processing apparatus of Bi type oxide superconducting wire 2 Heat processing furnace 2a, 2b, 2c Heater zone 3 Sending apparatus 4 Winding apparatus 5 Conveying apparatus 6 Preheating chamber 7 Slow cooling chamber 8 Control apparatus 9 Wire or twisted conductor 10 Gas supply device 11 Case

Claims (7)

  Oxide superconducting wire or oxide superconductor by heat-treating wire formed by filling raw material powder constituting Bi-based oxide superconducting material into a silver or silver alloy sheath, or a conductor obtained by twisting a plurality of them. The heat treatment apparatus includes: a feeding apparatus and a winding apparatus; a heat treatment furnace disposed between the feeding apparatus and the winding apparatus; and the heat treatment furnace. Heat treatment controllable to a heat treatment temperature including a partial melting temperature region for producing a Bi (2212) -based oxide superconductor. An atmosphere control means including a zone and capable of heat-treating the wire or conductor placed on the wire or conductor disposed in the heat treatment furnace in an oxidizing atmosphere. Bi-based oxide superconducting wire of a continuous heat treatment apparatus, characterized in that was e.   The heat treatment furnace is composed of a plurality of heater zones whose temperature can be controlled with a predetermined heat treatment pattern including a heat treatment zone which can be controlled to a heat treatment temperature including a partial melting temperature region for generating a Bi (2212) -based oxide superconductor. The continuous heat treatment apparatus for a Bi-based oxide superconducting wire according to claim 1.   The heat treatment pattern includes a heating region in which the oxygen concentration is 50% or more and the heat treatment temperature is higher than the melting point of the Bi (2212) -based oxide superconductor and heated at a temperature lower than 20 ° C. exceeding the melting point. A continuous heat treatment apparatus for a Bi-based oxide superconducting wire according to claim 2.   4. The heat treatment apparatus according to claim 1, further comprising a preheating chamber on an inlet side and a slow cooling chamber on an outlet side of a conveyance path for a wire or conductor conveyed in the heat treatment furnace. 5. Continuous heat treatment apparatus for Bi-based oxide superconducting wire.   The preheating chamber includes means for heating to a temperature of several tens of degrees below the melting point of the Bi (2212) oxide superconductor, and the slow cooling chamber is 10 ° C. below the solidification temperature of the Bi (2212) oxide superconductor. 5. A continuous heat treatment apparatus for a Bi-based oxide superconducting wire according to claim 4, further comprising means for cooling to a temperature.   The conveying device is constituted by a pair of synchronously rotating drive rollers and an endless belt made of a net-like body formed of a wire of a heat-resistant metal material stretched between the drive rollers. 2. A continuous heat treatment apparatus for a Bi-based oxide superconducting wire according to 1. The feeding device, the winding device, and the conveying device have a feeding speed such that the tensile strain on the wire constituting the wire or conductor is 0.1% or less and the amount of bending strain is 0.1% or less. The continuous heat treatment apparatus for a Bi-based oxide superconducting wire according to claim 1, further comprising a control device for controlling a winding speed and a conveying speed.

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