JPH02227916A - Manufacture of oxide superconductive wire rod - Google Patents

Abstract

PURPOSE:To prevent deterioration taking place at the time of heat treatment while heightening the critical current density by heating and holding a core material at a temperature higher than the evaporation temperature of a core material followed by switching to an oxygen atmosphere for having its temperature raised up to the baking temperature of a superconductive material to be held for a prescribed time followed by being cooled. CONSTITUTION:Core materials 3 are put into a metal sheath material 1 and the periphery thereof is filled with a superconductive material powder 2 followed by drawing and rolling at a temperature higher than a softening point of the core material 3 which is put in the central part. Next, after holding the rolled wire rod at a fixed temperature higher than an evaporation temperature of the core materials 3 for a proper time in the vacuum atmosphere changed over to the oxygen atmosphere is applied to start warm up again in order to hold a prescribed baking temperature for a proper time followed by being cooled. Then, the core materials 3 filled in the sheath material 1 together with superconductive material powder 2 is melted and evaporated at the time of holding a fixed temperature and discharged from the end part of the opened wire rod. Thereby, a wire rod having an excellent superconductive characteristic can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing an oxide superconducting wire.

(Conventional wave elf) Conventionally, as a method of making wires from oxide superconductors, a pipe made of a metal sheath material such as silver is filled with oxide superconductor powder, and then drawn and rolled to make wires and tapes, and then a predetermined shape is formed. A method is used to manufacture wire rods with superconductivity by subjecting them to heat treatment under certain conditions.

However, with this method, during heat treatment, carbon dioxide gas released by decomposition of the carbonic acid remaining in the superconductor powder,
The pressure inside the sheath increases due to oxygen gas etc. that are said to be released from the superconductor, which may cause the sheath to bulge and cause the sheath and the superconducting material inside to separate.

(Problems to be solved by the invention) Regarding the production of oxide superconductors into wires using the metal sheath method,
It is an object of the present invention to provide a method for manufacturing a superconducting wire with high critical current density while preventing deterioration that occurs during heat treatment.

(Means for solving the problem) In a method of forming an oxide superconducting material into a wire or tape using a metal sheath method, a) a substance that evaporates at a temperature lower than the firing temperature of the oxide superconductor is contained in the metal sheath. After inserting one or more core materials, the superconducting material is filled, b) This is rolled at a temperature higher than the softening point of the core material, and C) This is further rolled in a vacuum atmosphere and at a temperature lower than the evaporation temperature of the core material. The problem with the conventional wire manufacturing method was solved by heating and holding at the above temperature, d) switching to an oxygen atmosphere, raising the temperature, raising the temperature to the firing temperature of the superconducting material, holding it for a predetermined time, and then lowering the temperature.

(Example) FIG. 1 shows the state before rolling, where 1 is a metal sheath material, 3 is a core material, and 2 is a superconducting material powder. Now, in the present invention, when filling the metal sheath material 1 with the oxide superconducting material powder 2,
At its center, one or several core materials 3 made of metal or organic compound having a low evaporation temperature are placed. Thereafter, superconducting material powder 2 is filled around it. Next, drawing and rolling are performed at a temperature higher than the softening point of the core material 3 placed in the center.

When an organic compound or the like is used as the core material 3, the ductility of the core material 3 is lower than that of the sheath material 1 during drawing or rolling processing, so it is best to process the core material 3 after processing. It is difficult to distribute it uniformly in the length direction with the same shape as before.

For this reason, the heater 4 is heated to a temperature higher than the softening point of the core material 3.
Immediately after heating, rolling is performed using a rolling roll 5 to obtain a tape material 6.

Thereafter, this rolled wire rod is heat treated under the following conditions. That is, when raising the temperature from room temperature, the temperature is maintained in a vacuum atmosphere at a temperature higher than the evaporation temperature of the core material 3 for an appropriate period of time (symbol b in Figure 3), then switched to an oxygen atmosphere, and then heated again. The temperature starts to rise (FIG. 3, reference numeral c), and after being maintained at a predetermined firing temperature for an appropriate time (FIG. 3, reference numeral d), the temperature is lowered (FIG. 3, reference numeral e).

Also, during heat treatment, the seals applied to both ends for wire drawing and rolling are removed.

Through such heat treatment, the core material 3 filled in the sheath material 1 together with the superconducting material powder 2 melts and evaporates when the temperature pattern shown in FIG. The wire is discharged from the end of the wire. Also, since the sheath material 1 has not softened at this temperature, even if the pressure inside the sheath material 1 increases due to the evaporation of the core material 3, the sheath material 1
It does not bulge and evaporated gas is released from the end. Furthermore, since the atmosphere inside the furnace is evacuated by a vacuum pump at this time, the evaporated gas of the core material 3 is efficiently released from the end.

After the core material 3 evaporates and comes out, a through hole is formed. When firing superconducting materials in an oxygen atmosphere.

Oxygen enters the through holes, allowing the superconducting material to remain in direct contact with oxygen, making it easier to bring out superior superconducting properties compared to conventional methods. Furthermore, for this reason, the sheath material that was conventionally made of silver, which has good oxygen diffusivity, can be replaced with another material.

(Effects) Since the core material is inserted into the metal sheath and rolled at a temperature higher than the softening point of the core material, the core material is uniformly extended and distributed in the length direction.

Since the product in this state is kept in a vacuum atmosphere at a temperature higher than the evaporation temperature of the core material, the evaporated core material is discharged to the outside and that portion becomes a through hole.

Since the wire is switched and fired in an oxygen atmosphere in this state, the superconducting material comes in good contact with oxygen, and a wire with excellent superconducting properties can be obtained.

[Brief explanation of the drawing]

FIG. 1(a) is a cross-sectional view of a state in which a core material is inserted into a metal sheath material and filled with superconducting material powder. FIG. 1(b) is also a longitudinal sectional view. FIG. 2 shows the rolling process of the state shown in FIG. 1 under heating. FIG. 3 shows the atmosphere and temperature conditions of the heat treatment process. In the figure; 1 metal sheath material 2 superconducting material powder 3 core material
4 Heater 5 Rolling roll 6 Tape material and above Figure 2 Figure 3

Claims (1)

[Scope of Claims] A method for producing an oxide superconducting wire comprising the following steps a) to d) in a method of forming an oxide superconducting material into a wire or tape by a metal sheath method. a) One or more core materials made of a substance that evaporates at a temperature lower than the firing temperature of the oxide superconductor are inserted into the metal sheath, and then a superconducting material is filled. b) Rolling this at a temperature higher than the softening point of the core material. c) Further, this is heated and maintained in a vacuum atmosphere at a temperature higher than the evaporation temperature of the core material. d) Switch to an oxygen atmosphere, raise the temperature, raise the temperature to the firing temperature of the superconducting material, hold it for a predetermined time, and then lower the temperature.