CN106158139B - A kind of preparation method of high-temperature superconductor CICC conductors - Google Patents

Abstract

The invention discloses a kind of high-temperature superconductor CICC conductors and its manufacturing method, conductor includes hyperconductive cable, folded band, internal layer armor, outer layer armor.Method includes successively hyperconductive cable process, wears and pull, conductor molding, be heat-treated several steps.The present invention provides important parameter for the CICC conductor developments of large high-temperature superconduction from now on.

Description

A kind of preparation method of high temperature superconducting CICC conductor

technical field

The invention relates to the field of superconducting conductors in tokamak devices, in particular to a high-temperature superconducting CICC conductor and a manufacturing method thereof.

Background technique

Clean energy—the use of fusion energy is one of the dreams of human beings. The tokamak type magnetic confinement nuclear fusion device is a reliable device for generating fusion energy, and the full superconducting tokamak is an important guarantee for the continuous operation of the fusion reactor. On the basis of the successful establishment and operation of the EAST (Experimental Advanced Superconducting Tokamak) in China, China is actively carrying out the construction of the International Thermonuclear Experimental Reactor ITER (International Thermonuclear Experimental Reactor). At the same time, various countries have also started the pre-research work of the next generation fusion reactor. The superconducting cable is an important part of the tokamak device, and its technology is the key technology of fusion engineering. A notable feature of the next-generation fusion reactor is that the highest magnetic field of the central solenoid coil and the longitudinal field coil will exceed 12T. Limited by the critical magnetic field on the low-temperature superconducting wire, it is impossible to prepare a magnet with a higher magnetic field by using traditional low-temperature superconducting materials, and winding a magnet with a higher magnetic field requires that the material can still maintain a high critical current density in a magnetic field exceeding 20T . Therefore, seeking superconducting materials and high-field magnets with better comprehensive performance is a problem that must be solved in the future controllable magnetic confinement fusion demonstration reactor and commercialization process. Ceramic oxide high-temperature superconducting materials are ideal materials for building high-field magnets because of their extremely high irreversible field at 4.2K and excellent magnetic field current-carrying characteristics. Among the high-temperature superconducting materials, Bi ₂ Sr ₂ Ca ₁ Cu ₂ O _X (Bi-2212) is the only material that can be prepared into isotropic round wires. It is of practical application significance that it can still carry the load at 4.2K even if the external field is as high as 45T. Therefore, it is currently the most promising high-temperature superconducting material under high field (>20T).

Two key components in the manufacture of CICC conductors are superconducting cables and conductor armor. First of all, since the Bi-2212 superconducting material is a ceramic material, its mechanical properties are poor. During low-temperature operation, due to the thermal expansion and Lorentz force, the core wire of the superconducting material is prone to breakage, resulting in critical performance. decrease. To this end, we designed a new type of cable structure and cable stranding process. After verification, the new type of cable structure and stranding process fully meet the design requirements, thus solving the problem of Bi2212 cable stranding.

In terms of conductor structure design, traditional CICC conductors are generally composed of central cooling tubes, superconducting cables, overlapping tapes, and armor from the inside to the outside. For some CICC conductors, the cooling medium passes through the cable gap, so there is no central cooling pipe. As for the Bi2212 CICC conductor, a structure similar to that of the traditional CICC conductor can be selected, but a slight improvement is required. This is due to the special heat treatment environment of Bi2212 superconducting wire. First of all, Bi2212 heat treatment requires high temperature, high pressure, and pure oxygen environment. Therefore, many materials will be oxidized and deformed in high temperature oxygen. The second is that the formation of Bi2212 superconductor requires oxygen element to participate in the reaction. However, elements in alloys, such as stainless steel or nickel-based alloys, will react with oxygen at high temperatures, thereby affecting the formation of Bi2212, resulting in a decline in the performance of superconducting wires. Even if nickel-based superalloy is used as armor, it may affect the performance of Bi2212 superconducting wire. Moreover, high-temperature alloys have high strength, are difficult to process, and may damage cables when they are formed.

Contents of the invention

The purpose of the present invention is to provide a high-temperature superconducting CICC conductor and a manufacturing method thereof, so as to solve the problems existing in the superconducting conductor in the prior art tokamak device.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A high-temperature superconducting CICC conductor, characterized in that: comprising:

Superconducting cables, superconducting cables are spirally wound with overlapping tapes made of Ag or Ag-Mg alloy materials,

The inner protective layer, the superconducting cable made of 316L material is wrapped around the superconducting cable covered with Ag tape,

The outer layer of armor covers the inner protective layer, and the outer layer of armor is made of stainless steel.

A preparation method of a high-temperature superconducting CICC conductor, characterized in that: comprising the following steps:

(1) Stranding of superconducting cables: multi-strand superconducting wires are twisted together to form a superconducting cable; the twisting of superconducting cables is made by multi-stage twisting according to the structure of the cable; The automatic control is adjustable, the mold is made of polytetrafluoroethylene material, the tension of the first-class cable does not exceed 20N, the tension of the second-class cable does not exceed 40N, the tension of the third-class cable does not exceed 70N, the tension of the fourth-class cable does not exceed 150N, and the tension of the fifth-class cable No more than 250N; the superconducting cable is helically wound with Ag lapping tape, the lapping rate of the Ag lapping tape is greater than 50%, and the outer layer is wrapped with a layer of 316L to protect the Ag lapping tape, and the lapping rate is controlled at 30% %-40%; during the cable stranding process, there will be no flattening and disconnection;

(2) Penetration: the cable wrapped with a protective layer is penetrated into the outer armor;

After the cable is completed, the cable will be threaded; first, the outermost stainless steel armor is welded to the length required by the conductor, and then the cable is inserted into the welded stainless steel armor, and the cable threading is completed;

During the cable threading process, the pulling force should not exceed 50kN;

(3) Conductor forming: After the cable is threaded, the gap between the cable and the stainless steel pipe is about 2.0mm, so the conductor needs to be reduced in diameter, one is to eliminate the gap between the cable and the stainless steel, and the other is to make the inside of the conductor meet about 30 % void ratio; the conductor forming will be completed by a self-developed multi-pass forming machine; the outer diameter tolerance after forming shall not exceed 0.2mm;

(4) Heat treatment: Before the formed conductor is used, the performance of the conductor sample needs to be evaluated, and the length of the sample is at least 4 meters; before the sample is evaluated, heat treatment is required; the heat treatment of the Bi2212 conductor needs to be performed in a high-pressure, high-temperature oxygen environment It is carried out under the environment, in which the pressure is maintained at no more than 50 atmospheres, and heat treatment is required at a high temperature of 890 degrees for 48 hours. Oxygen passes through the external connection and passes through the interior of the conductor.

The invention provides an important technical reference for future research and development of large-scale high-temperature superconducting CICC conductors and large-scale high-temperature superconducting coils. Experiments have proved that the current-carrying capacity of CICC conductors manufactured by this method is greater than 10KA under self-field conditions at a temperature of 4.2 K. The conductor itself can also be used as an experimental platform for more performance tests, providing important parameters for the future development of large-scale high-temperature superconducting CICC conductors.

Description of drawings

Fig. 1 is a front view of the conductor structure of the present invention.

Fig. 2 is a three-dimensional cross-sectional view of the conductor structure of the present invention.

Detailed ways

As shown in Figure 1 and Figure 2, a high-temperature superconducting CICC conductor includes:

Superconducting cable 1, superconducting cable 1 is helically wound with overlapping tape 2 made of Ag or Ag-Mg alloy material,

The inner protective layer 3, which wraps the superconducting cable 1 wrapped with the lapping tape 2, the inner protective layer 3 is made of 316L material,

The outer layer of armor 4 covers the inner protective layer 3, and the outer layer of armor 4 is made of stainless steel.

A method for preparing a high-temperature superconducting CICC conductor, comprising the following steps:

(1) Stranding of superconducting cables: multi-strand superconducting wires are twisted together to form a superconducting cable; the twisting of superconducting cables is made by multi-stage twisting according to the structure of the cable; The automatic control is adjustable, the mold is made of polytetrafluoroethylene material, the tension of the first-class cable does not exceed 20N, the tension of the second-class cable does not exceed 40N, the tension of the third-class cable does not exceed 70N, the tension of the fourth-class cable does not exceed 150N, and the tension of the fifth-class cable No more than 250N; the superconducting cable is helically wound with Ag lapping tape, the lapping rate of the Ag lapping tape is greater than 50%, and the outer layer is wrapped with a layer of 316L to protect the Ag lapping tape, and the lapping rate is controlled at 30% %-40%; during the cable stranding process, there will be no flattening and disconnection.

(2) Penetration: the cable wrapped with a protective layer is penetrated into the outer armor;

After the cable is completed, it will be threaded. The outermost layer of stainless steel (316L or 316LN) armor is welded first to the required length of the conductor, and then the cable is inserted into the welded stainless steel armor to complete the cable threading.

During the cable threading process, the tension should not exceed 50kN.

(3) Conductor forming: After the cable is threaded, the gap between the cable and the stainless steel pipe is about 2.0mm, so the conductor needs to be reduced in diameter, one is to eliminate the gap between the cable and the stainless steel, and the other is to make the inside of the conductor meet about 30 % porosity. Conductor forming will be done using a self-developed multi-pass forming machine. The outer diameter tolerance after molding is not more than 0.2mm.

(4) Heat treatment: Before the formed conductor is used, it is necessary to evaluate the performance of the conductor sample, and the length of the sample should be at least 4 meters. Before samples can be evaluated, heat treatment is required. Bi2212 conductor heat treatment needs to be carried out in a high-pressure, high-temperature oxygen environment, where the pressure is maintained at no more than 50 atmospheres, and heat treatment at a high temperature of 890 degrees is required for 48 hours. Oxygen passes through the external connection and passes through the inside of the conductor.

The invention discloses a novel high-temperature superconducting CICC conductor, and the superconducting cable used is a Bi2212 silver-based superconducting wire. The conductor is composed of Bi2212 superconducting cable, Ag or Ag-Mg overlapping tape, 316L inner protective layer, and stainless steel outer armor. The key technologies and processes in conductor manufacturing include: cable stranding, cable threading, conductor forming, and conductor heat treatment.

The conductor structure of the present invention consists of a superconducting cable, a lapping tape, an inner protective layer and an outer armor from the inside to the outside. Among them, Ag or Ag-Mg alloy is selected as the material of the lapping tape, because the material of the inner protective layer must meet the following requirements:

1) It will not react violently with oxygen in high temperature oxygen

2) During heat treatment, the elements in the alloy will not react with Bi2212 powder

The Ag-Mg alloy does not react violently with oxygen, and is the same as the sheath material of the Bi2212 superconducting wire, so it will not affect the reaction of the Bi2212 powder with oxygen to form a Bi2212 phase.

The 316L stainless steel tape is used as the inner protective layer, which can protect the overlapping tape of the cable from damage when the cable is threaded and reduced in diameter, and avoid direct contact between the cable and the external stainless steel armor.

The choice of stainless steel as the outer armor is mainly for supporting and protecting.

In the inventive method:

After the cable penetrates the armor and before heat treatment, the conductor needs to be reduced in diameter to reduce the gap between the strands and ensure that the strands will not undergo large strains under the action of electromagnetic force. And the size after shrinkage should not be too small, because shrinking the conductor too small will cause the strands to be over-extruded, and secondly, the gap will affect the flow of coolant if the gap is too small. Therefore, the control of the reduced diameter is very important.

Conductor forming will use multi-roller, multi-pass forming machine for slow-speed forming of conductors. Before each forming, empty tubes will be used for wheel set debugging to ensure the accuracy of conductor size.

The conductor manufacturing process is as follows:

Stranding of superconducting cables → cable threading → conductor forming → heat treatment.

Claims (1)

1. a preparation method of high temperature superconducting CICC conductor, is characterized in that: comprise the following steps: (1) Stranding of superconducting cables: multi-strand superconducting wires are twisted together to form a superconducting cable; the twisting of superconducting cables is made by multi-stage twisting according to the structure of the cable; The automatic control is adjustable, the mold is made of polytetrafluoroethylene material, the tension of the first-class cable does not exceed 20N, the tension of the second-class cable does not exceed 40N, the tension of the third-class cable does not exceed 70N, the tension of the fourth-class cable does not exceed 150N, and the tension of the fifth-class cable No more than 250N; the superconducting cable is helically wound with Ag lapping tape, the lapping rate of the Ag lapping tape is greater than 50%, and the outer layer is wrapped with a layer of 316L to protect the Ag lapping tape, and the lapping rate is controlled at 30% %-40%; during the cable stranding process, there will be no flattening and disconnection; (2) Penetration: the cable wrapped with a protective layer is penetrated into the outer armor; After the cable is completed, the cable is threaded; first, the outermost stainless steel armor is welded to the length required by the conductor, and then the cable is inserted into the welded stainless steel armor, and the cable threading is completed; During the cable threading process, the controlled tension does not exceed 50kN; (3) Conductor forming: After the cable is threaded, the gap between the cable and the stainless steel pipe is 2.0mm, and the diameter of the conductor is reduced. One is to eliminate the gap between the cable and the stainless steel, and the other is to make the inside of the conductor meet the 30% gap. The conductor forming is completed by a self-developed multi-pass forming machine; the outer diameter tolerance after forming is not more than 0.2mm; (4) Heat treatment: Before the formed conductor is used, the performance of the conductor sample is evaluated, and the length of the sample is at least 4 meters; before the sample is evaluated, heat treatment is performed; the heat treatment of the Bi2212 conductor is carried out in a high-pressure, high-temperature oxygen environment. The pressure is maintained at no more than 50 atmospheres, and the heat treatment is performed at a high temperature of 890 degrees for 48 hours. The oxygen passes through the external connection and passes through the inside of the conductor.