JPH0453050B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing superconducting compounds by electron beam irradiation. Using superconducting wires with zero electrical resistance allows large currents to flow without consuming power, and the superconducting state is maintained even in strong magnetic fields, making them useful for NMR analyzers, energy storage, fusion reactors, and high-energy physics. It is being used as a winding material for electromagnets used to generate strong magnetic fields, such as in particle accelerators. BACKGROUND ART Currently, alloy-based Nb-Ti, Nb ₃ Sn and V ₃ Ga called A-15 type compounds are used as superconducting materials as winding materials for electromagnets for generating strong magnetic fields. Nb-Ti alloy has high plasticity and can be directly processed into wire rods, but _{the A-}
Type 15 compounds are hard and brittle and cannot be processed directly, so wire rods have traditionally been manufactured using diffusion reactions such as surface diffusion methods and composite processing methods. In these conventional diffusion reaction methods, high-temperature heating is generally performed in an electric furnace. For example, in the case of Nb ₃ Sn, it is heated at a temperature of about 700°C in an electric furnace for about 100 hours. Ta. A- of these Nb-Ti alloys, Nb ₃ Sn, V ₃ Ga
The critical magnetic field H _C2 of the type 15 compound at 4.2K is 12T, 21T, and 22T (T: Tesla), respectively, and the closer the applied magnetic field is to this value, the more rapidly the critical current density Jc decreases. Therefore, even if V ₃ Ga wire is used, the maximum magnetic field generated as a superconducting magnet is 17.5T. On the other hand, with the development of superconducting applications, superconducting magnets are required to generate stronger magnetic fields than conventional ones, and there is a demand for the development of high-performance superconducting compounds. For example, it is said that a mirror-type superconducting magnet for a fusion reactor requires magnetic field generation of 20 to 24 T. However, such a strong magnetic field cannot be applied to the existing Nb ₃ Sn,
It is difficult to obtain it with V ₃ Ga wire. Currently, A-15 type compounds such as Nb ₃ Al, Nb ₃ (Al, Ge), Nb ₃ Ga, and Sieprel type compounds PbMo ₆ S ₈ have been found to have excellent superconducting properties. However, this Nb ₃ Al, Nb ₃ (Al, Ge),
The H _C2 of PbMo ₆ S ₈ is 30T, 41T, and 50T, respectively.
It has properties superior to Nb ₃ Sn and V ₃ Ga, but if you try to manufacture them by heating them in an electric furnace using the conventional surface diffusion method or composite processing method, for example, in the case of Nb ₃ Al, Because the temperature at which the diffusion reaction occurs is extremely high, as it must be heated to at least 1800°C, there is a problem that the crystal grains become coarser and the critical current density Jc, which is important for practical use, decreases significantly. Ta. Purpose of the Invention The present invention aims to solve the problems in conventional methods, and its purpose is to provide a method that can easily produce compound superconducting wires with excellent properties that are difficult to obtain with conventional methods. It is in. Structure of the Invention As a result of research to achieve the above object, the present inventors have found that by irradiating a composite consisting of the constituent elements of a superconductor made by an infiltration method with a high-energy density electron beam, the composite can be rapidly heated and We have found that rapid cooling can produce superconducting wires with superior Jc values that could not be obtained using conventional methods. The present invention was completed based on this knowledge. The gist of the present invention is to apply an accelerating voltage to a composite obtained by infiltrating a melt consisting of other constituent elements into the gap between a sintered body of powder or a bundle of fine wires made of one or more of the constituent elements of a superconducting compound. A method for producing a superconducting compound characterized by irradiating an electron beam with a power density of 5 to 150 KV and a power density of 10 ³ to ^{10 7} W/cm ² . In order for the superconducting compound used in the present invention to have excellent superconducting properties, A-
Type 15 compounds Nb ₃ Al, Nb ₃ (Al, Ge),
Nb ₃ Ga, or Sieprel type compound
_Preferably it is _PbMo6S8 . However, it is not limited to these compounds. The accelerating voltage when irradiating the electron beam must be between 5 and 5 in order for energy to be effectively absorbed by the composite.
It is necessary to be in the range of 150KV. Below KV, energy absorption is insufficient, and above 150 KV, the electron beam passes through and becomes useless. The power density needs to be between 10 ³ and ^{10 7} W/cm ² . If it is less than 10 ³ W/cm ² , it will not be possible to obtain a high enough temperature to generate the compound phase, and
If it exceeds 10 ⁷ W/cm ² , the composite will be overheated and disadvantageous phenomena such as melting will occur. Preferably, the volume percentage of the melt in the composite is 5-50%. If it is less than 5%, superconducting compounds will not be sufficiently produced, and if it exceeds 50%, compounds other than superconducting compounds will be produced, and in both cases the superconducting properties will deteriorate. Heat treatment before and after electron beam irradiation improves superconducting properties. The heat treatment temperature before irradiation is 400 to 2000℃, and the heat treatment temperature after irradiation is
The temperature is preferably 300 to 1500°C. Furthermore, heat treatment may be performed before and after irradiation, if necessary. Example 1 Nb powder with a particle size of approximately 0.1 mm was pressurized and molded at 2200°C.
It was heated for 1 hour to sinter. This was immersed in an Al bath heated to approximately 800°C to infiltrate the gaps between the sintered bodies, and then inserted into a Nb tube, drawn, and drawn to create a tape with a width of 6 mm and a thickness of 0.1 mm. Ivy. While moving this tape at a speed of 10cm/sec in vacuum, the acceleration voltage is 20KV and the current density is 5~10mA/
irradiated with an electron beam at mm ² . This heated the irradiated area and produced a Nb ₃ Al superconducting compound, after which the heat escaped to the unirradiated area and rapidly cooled it. When irradiated with a current density of 7 mA/ ^mm2 , the part that has become a superconducting compound has a cross section with a width of approximately 1 mm and a thickness of approximately
It was 0.05mm. For these tapes, the superconducting critical temperature Tc
The results of measuring the magnetic field current Ic at 17 Tesla are shown in Table 1 below.

[Table] When converted to critical current density Jc, 4×
The value is 10 ⁴ A/cm ² or more. When this tape was further heat-treated at 700°C for 100 hours, the Tc increased by around 1.5K as shown in Table 1, and the Jc value in high magnetic fields also increased accordingly. In addition, heat treatment at 1000℃ for 30 minutes before electron beam irradiation facilitated the reaction, resulting in a temperature of 17K.
Tc and Ic of 25A (17T) were obtained. When this was further heat-treated at 700°C for 100 hours after electron beam irradiation, Tc increased to 18.0K and Ic to 30A. Example 2 Approximately 800 fine Nb wires with a diameter of 0.3 mm were bundled and inserted into a Nb tube, and heated at 2200° C. for 1 hour to sinter the Nb wires together. This was heated to about 800°C to produce Al-10 atomic%
After immersing Ge in a bath to infiltrate the Al-Ge alloy into the gaps between the Nb wires, the wires are drawn and rolled to a width of 6 mm and a thickness of 6 mm.
The tape was 0.1mm thick. Put this tape in a vacuum for 10
Moving at a speed of cm/sec, acceleration voltage 20KV,
Electron beam irradiation was performed at a current density of 5 to 10 mA/mm ² . As a result, the irradiated area is heated and Nb ₃ (Al,
Ge) A superconducting compound was formed, and then the heat escaped to the unirradiated area and was rapidly cooled. of the resulting tape
When Tc and Ic at 17T were measured, respectively.
It was 17.1K and 20A. When this was further heat treated at 700℃ for 100 hours, Tc and Ic (at 17T)
increased to 19.3K and 24A, respectively. Example 3 800 thin Mo wires with a diameter of 0.3 mm were bundled and inserted into a Ta tube, and heated at 2400° C. for 1 hour to sinter the Mo wires. This was heated to about 1200℃ Pb-40 atomic%
After soaking in an S bath to infiltrate the Pb-S melt into the gaps between the Mo wires, the wires are drawn and rolled to a width of 6 mm and a thickness of 0.2 mm.
I made a tape. Next, put this tape in a vacuum for 10 minutes.
Accelerating voltage 20KV while moving at a speed of cm/sec,
Electron beam irradiation was performed at a current density of 5 to 10 mA/mm ² . This heated the irradiated area and produced a PbMo ₆ S ₈ superconducting compound, after which the heat escaped to the unirradiated area and rapidly cooled it. Tc and of the obtained tape
When Ic was measured at 17T, they were 12.8K and 12.8K, respectively.
It was 10A. When this was further heat treated at 500°C for 100 hours, Tc and Ic (at 17T) rose to 13.0K and 13A, respectively. Effects of the Invention According to the method of the present invention, the following excellent effects can be achieved. (1) Since the energy density of the electron beam is extremely high, even if the irradiated part moves at a relatively high speed with respect to the wire material, the irradiated part is instantaneously heated to a sufficiently high temperature, and the chemical content remains stable at high temperatures. A compound phase with excellent properties of theoretical composition can be easily produced. Therefore, superconducting compounds with excellent properties, such as Nb ₃ Al, Nb ₃ (Al.Ge), and PbMo ₆ S ₈ , to which it has been difficult to apply conventional diffusion methods, can be made into wires with great ease. (2) Since it is electron beam heating, heating is limited to the irradiated area, and after irradiation, heat is rapidly dissipated by thermal conduction, so the rapid cooling effect is large and the high temperature stable phase can be kept at room temperature. In addition, the crystal grains can be kept small, and a wire rod with a high Jc value, which is important for practical use, can be obtained. (3) Since it is possible to irradiate the electron beam by moving the wire material or the electron beam at high speed, manufacturing can be performed efficiently, and long wire materials can be manufactured extremely easily, reducing costs. can also be obtained cheaply. (4) Since the wire obtained by the method of the present invention has excellent superconducting critical current characteristics, the amount of wire required to generate a strong magnetic field is small, and cooling costs can be reduced.

Claims (1)

[Claims] 1. In the gap between a sintered body of powder or a bundle of fine wires made of one or more constituent elements of a superconducting compound,
A composite obtained by infiltrating a melt consisting of other constituent elements is heated at an accelerating voltage of 5 to 150 KV and a power density of 10 ³ to
A method for producing a superconducting compound characterized by irradiation with an electron beam of 10 ⁷ W/cm ² . 2. The method for producing a superconducting compound according to claim 1, wherein the superconducting compound is an A-15 type superconducting compound or a Sieprel type superconducting compound. 3 The sintered body or the thin wire is a sintered body of Nb powder or the Nb thin wire, and the molten body is made of one or more selected from Al, Ge, and Ga, as described in claim 1. A method for producing superconducting compounds. 4 Sintered body or thin wire is Mo powder sintered body or
2. The method for producing a superconducting compound according to claim 1, wherein the superconducting compound is a thin wire of Mo, and the melt is composed of one or more selected from Pb, Sn, and Cu and S. 5. The method for producing a superconducting compound according to claim 1, wherein heat treatment is performed at 300 to 2000° C. before or after electron beam irradiation, or both.