JP2008103155A - Manufacturing method of oxide superconductive wire rod, and judgement method of powder for oxide superconductive wire rod - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an oxide superconductive wire rod capable of obtaining high critical current characteristics with good reproducibility and a judgement method of the oxide superconductive wire rod powder. <P>SOLUTION: The manufacturing method of the oxide superconductive wire rod is provided with a filling process to fill powders of the oxide superconductor or powders to become its material into a metal sheath material and a drawing process to manufacture a wire rod by applying a plastic working on the metal sheath material. The H<SB>2</SB>O molecular number desorbed from sample powders 1g is measured and, at its measurement, those sample powders having a maximum value A of the H<SB>2</SB>O molecular number in a range of 50-300°C of 10<SP>18</SP>or less and a ratio (B/A) of the peak value B of the H<SB>2</SB>O molecular number measured at further temperature rise within temperature range of 200°C from the measuring temperature of the maximum value A and the maximum value A being below 0.5 are judged as an adequate powder 1, and the adequate powders 1 are filled into the metal sheath material 2 to manufacture the wire rod. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an oxide superconducting wire having excellent reproducibility and high critical current characteristics, and a method for determining a powder for an oxide superconducting wire.

  Oxide superconducting wires having high critical current characteristics include bismuth and yttrium, and the powder-in-tube method, which is excellent in lengthening, is generally known as the former method for producing oxide superconducting wires. Yes. In this process, oxide superconductor powder or its raw material powder is basically filled into a metal sheath material such as a silver pipe, subjected to plastic processing such as wire drawing, and finally superconductor crystals are formed. A heat treatment for orientation is performed.

  The oxide superconducting wire is required to have a high critical current density in order to be applied to a superconducting coil, a superconducting magnet, an MRI apparatus, a magnetic levitation train, a SMES (Superconducting Magnetic Energy Storage). According to the powder-in-tube method, it is known that it is easy to lengthen the wire, and that a relatively high critical current characteristic can be obtained with a bismuth oxide superconducting wire.

Japanese Unexamined Patent Publication No. 63-270342 JP 2004-087488 A

  However, it is known that the wire material obtained by the powder-in-tube method has greatly different critical current characteristics of the final wire material depending on the state of the raw material powder filled in the metal sheath material, plastic working conditions, and the like. For example, in the production of a bismuth-based oxide superconducting wire, the drawback is that the reproducibility of high critical current characteristics is poor, that is, the yield of wires having high critical current characteristics is low.

  As one of the causes, the raw material powder is not limited to the oxide superconductor powder, and moisture adsorption generally occurs. Therefore, when the raw material powder is in a hygroscopic state (occlusion state), the properties of the powder itself are It is considered that the critical current characteristics of the final wire are greatly affected.

  Accordingly, an object of the present invention is to provide a method for producing an oxide superconducting wire and a method for determining a powder for an oxide superconducting wire, which can obtain high critical current characteristics with good reproducibility.

In order to achieve the above object, the invention of claim 1 includes a filling step of filling a metal sheath material with a powder of an oxide superconductor or a raw material thereof, and a metal sheath material filled with the powder. In a method for producing an oxide superconducting wire comprising a wire drawing step for producing a wire by performing plastic working, 1 g of sample powder is heated from room temperature to 20 ° C./minute in a high vacuum state of 10 ⁻⁶ Pa or higher. The temperature is increased at a rate of temperature increase, and the number of H ₂ O molecules desorbed from the sample powder is measured every 4 ° C. using a mass spectrometer. When the maximum value A of the number of H ₂ O molecules at each measurement temperature within the range of 300 ° C. is 10 ¹⁸ or less, and when the temperature is further increased within the temperature range of 200 ° C. from the measurement temperature of the maximum value A The peak value B of the number of H ₂ O molecules to be measured The ratio (B / A) to the maximum value A is <0.5, or the maximum value A is 10 ¹⁸ or less, and within the temperature range of 200 ° C. from the measurement temperature of the maximum value A When the temperature is raised, the number of H ₂ O molecules only decreases and the peak value B is not measured is made an appropriate powder, the appropriate powder is filled in the metal sheath material, and the wire is produced. It is a manufacturing method of the oxide superconducting wire.

The invention according to claim 2 is the method for producing an oxide superconducting wire according to claim 1, wherein the powder, which is inappropriate at the time of measuring the number of H ₂ O molecules, is subjected to heat treatment under reduced pressure to dehydrate the powder.

  The invention according to claim 3 is the method for producing an oxide superconducting wire according to claim 1, wherein the oxide superconductor powder is composed mainly of a 2212 phase of a bismuth-based oxide superconductor.

The invention of claim 4 is used in the manufacture of oxide superconducting wires, and in the method for determining oxide superconductor powder or powder as a raw material thereof, the number of H ₂ O molecules absorbed and occluded in the powder is measured. Therefore, 1 g of the sample powder is heated from room temperature at a temperature rising rate of 20 ° C./min in a high vacuum state of 10 ⁻⁶ Pa or higher, and the sample powder is used every 4 ° C. using a mass spectrometer. The number of H ₂ O molecules desorbed from the sample is measured, and at the time of measurement, the maximum value A of the number of H ₂ O molecules at each measurement temperature within a temperature range of 50 to 300 ° C. of the sample powder or the sample powder is ¹⁸ or less, and the ratio between the maximum value a and the peak value B of H ₂ O the number of molecules to be measured when the temperature was raised within a temperature range of more 200 ° C. from the measured temperature of the maximum value a (B / A) is <0.5 or the maximum value A is 10 ¹⁸ The following is determined as an appropriate powder when the peak value B is not measured only when the number of H ₂ O molecules is decreased when the temperature is further increased from the maximum temperature A within the temperature range of 200 ° C. A method for determining a powder for an oxide superconducting wire, wherein the powder determined to be appropriate is used for manufacturing an oxide superconducting wire.

  According to the present invention, by defining the amount of occluded / adsorbed moisture that can be used as a filling powder used in the production of oxide superconducting wires by the powder-in-tube method, it has high critical current characteristics with excellent reproducibility. An oxide superconducting wire can be manufactured.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  In a method of manufacturing an oxide superconducting wire according to a preferred embodiment of the present invention, first, as shown in FIG. 1, a bismuth 2212 oxide superconductor powder (hereinafter referred to as Bi2212 powder) 1 is an Ag pipe (metal). The sheath material 2 is filled (filling step). When using raw material powders of Bi2212 oxide superconductor, first, these powders are synthesized and fired to produce Bi2212 powder 1, and then Ag22 is filled with Bi2212 powder 1 that has been synthesized and fired.

  Next, as shown in FIG. 2, the Ag pipe 2 filled with the Bi2212 powder 1 is subjected to first wire drawing (plastic working) using a wire drawing die 3 to produce a single core wire 5 (first wire). 1 wire drawing process). Next, as shown in FIG. 3, a large number of single-core wires 5 are incorporated into an Ag alloy pipe (metal sheath material) 4 to produce a multi-core wire (billet) 6 (an assembling step). Next, as shown in FIG. 4, the multifilamentary wire 6 is subjected to second wire drawing using a wire drawing die 13 to produce a wire 15 (second wire drawing step).

  Finally, the wire 15 is subjected to a heat treatment to orient the superconductor crystals (heat treatment step), whereby a Bi2212 oxide superconducting wire is obtained.

The present embodiment is characterized in that the acceptable “H ₂ O molecular number / 1 g” of the powder (Bi2212 powder 1 or Bi2212 oxide superconductor raw material powder) used in the filling step of the manufacturing process is defined. .

Bi2212 powder 1 used in the filling process of the manufacturing process contains a certain amount of moisture (H ₂ O) (occluded and adsorbed), but also adsorbs moisture during the handling of the powder. Will occur. When a certain amount or more of moisture is occluded and adsorbed on the oxide superconductor powder, the critical current characteristic of the final wire manufactured using the powder is lowered and / or the reproducibility of the critical current characteristic is deteriorated. Therefore, in this embodiment, it is determined whether the powder is suitable for use before the filling step of the manufacturing process (determination step).

In this determination step, 1 g of sample powder is first heated from room temperature at a rate of temperature increase of 20 ° C./min in a high vacuum state of 10 ⁻⁶ Pa or higher, and a mass spectrometer is increased every 4 ° C. Is used to measure the number of H ₂ O molecules desorbed from the sample powder. This measurement is performed by using, for example, temperature desorption spectroscopy (TDS). As shown in FIG. 5, the measurement principle of TDS analysis is that a sample 9 placed on a sample stage 10 is heated with infrared rays, and a gas (desorption H ₂ O) 8 is released from a quadrupole mass spectrometer. 7 is detected. The obtained information is a mass spectrum of the emitted gas 8 having a mass number of 1 to 200, and measurement of H ₂ O molecules is performed by detecting a mass spectrum of Mz18.

FIG. 6 shows the result of TDS analysis of Bi2212 powder 1 and shows the relationship between the sample surface temperature (powder surface temperature) and the number of H ₂ O molecules / 1 g.

As shown in FIG. 6, the maximum value A of the number of H ₂ O molecules is measured at around 120 ° C. within the range of the powder surface temperature of 50 to 300 ° C. Furthermore, within the range of the temperature 120 to 320 ° C. of the sample stage 10 (further 200 ° C. from the measurement temperature of the maximum value A), the peak value B of the number of H ₂ O molecules is measured around the powder surface temperature of 220 ° C.

In this embodiment, during these measurements, the maximum value A of the number of H ₂ O molecules is 10 ¹⁸ or less, and the ratio of the peak value B of the number of H ₂ O molecules to the maximum value A (B / A ) Is <0.5, it is determined that Bi2212 powder 1 (Bi2212 powder 1 used in the filling step) has an appropriate amount of occluded water. Alternatively, the maximum value A of the number of H ₂ O molecules is 10 ¹⁸ or less, and the peak value B is not measured only when the number of H ₂ O molecules decreases within the range of the powder surface temperature of 120 to 320 ° C. It is determined that Bi 2212 powder 1 has an appropriate amount of occluded water. In the case of the raw material powder of the Bi2212 oxide superconductor, the same determination is performed, and each raw material powder determined to have an appropriate amount of occluded moisture is synthesized and fired to produce an appropriate Bi2212 powder 1.

The Bi2212 oxide superconducting wire finally obtained using the Bi2212 powder 1 determined to be appropriate has a high critical current characteristic value and is extremely excellent in reproducibility. In other words, by manufacturing the oxide superconducting wire using the method for determining a powder for an oxide superconducting wire according to the present embodiment, it is possible to manufacture a Bi2212 oxide superconducting wire having high critical current characteristics with high reproducibility. It becomes. Further, the value of the number of H ₂ O molecules per gram of the powder is within a range satisfying the condition that the maximum value A is 10 ¹⁸ or less and B / A is <0.5 (or no peak value B). If so, the reproducibility is good, but the critical current characteristic Jc value tends to increase slightly as the B / A value decreases.

On the other hand, the Bi2212 oxide superconducting wire using the Bi2212 powder 1 with B / A of ≧ 0.5 in FIG. Get smaller. In addition, even when B / A is <0.5, the Bi2212 oxide superconducting wire using the Bi2212 powder 1 having a maximum value A of more than 10 ¹⁸ has low critical current characteristics and is reproducible. Also lacks.

Here, even if Bi 2212 powder 1 whose occluded water content was not determined to be appropriate was subjected to the heat treatment under reduced pressure to properly dehydrate the powder, the above-described determination was performed again, and the maximum value A was 10 ^{If 18} or less and B / A satisfies the condition of <0.5 (or no peak value B), that is, if the stored moisture content of Bi2212 powder 1 is controlled within an appropriate range, the oxide superconducting wire It becomes possible to apply to manufacturing. Further, even if Bi 2212 powder 1 is determined to have an appropriate amount of occluded moisture, it can be dehydrated by performing reduced pressure heat treatment to control the amount of occluded moisture to a higher level, thereby achieving a higher critical current characteristic value. High reproducibility can be obtained. The temperature, time, and degree of vacuum of the reduced pressure heat treatment conditions are appropriately adjusted according to the amount of stored moisture of Bi2212 powder 1. For example, the higher the stored amount of moisture, the higher the temperature, the longer the time, or the higher the degree of vacuum. The lower the moisture content, the lower the temperature, the shorter the time, or the lower the vacuum.

The manufacturing method of the present embodiment relates to a manufacturing method of an oxide superconducting wire, particularly a Bi2212 oxide superconducting wire, but other superconducting wire manufactured by a powder-in-tube method, for example, a bismuth-based 2223 oxide. It can also be applied to a method of manufacturing a superconducting wire. In addition, the manufacturing method of the present embodiment is a general oxide superconducting wire produced using another powder in-tube method, or an oxide superconducting wire produced using powder in a method other than the powder in-tube method. This method can also be applied. Furthermore, in addition to the oxide superconducting wire, the present invention can also be applied to a superconducting wire manufacturing method using a powder-in-tube method such as a MgB ₂ superconducting wire. However, some of these cases have different B / A criteria and ranges. In some cases, it may be better to provide criteria such as “A + B” instead of “B / A”.

  The oxide superconducting wire obtained by the manufacturing method of the present embodiment can be applied to a superconducting coil, a superconducting magnet, an MRI apparatus, a magnetic levitation train, SMES, etc. In addition to these, a high critical current density is required. It can be used for all superconducting wire application systems.

  Examples of the present invention and comparative examples are shown below.

  Samples were Bi2212 powder heat-treated under reduced pressure (dehydration treatment) (Example 1), as it was after powder synthesis firing (no treatment) (Example 2), and hydrolyzed to change the amount of occluded water. Six types of samples (Example 3 and Comparative Examples 1 to 3) were prepared. Table 1 shows details of six types of samples (powder Nos. A to f).

TDS analysis was performed about each sample of Examples 1-3 and Comparative Examples 1-3. Table 2 shows the analysis conditions for the TDS analysis. In addition, for each sample, the maximum value A and peak value B of the number of H ₂ O molecules were measured within the range of the sample stage temperature of 50 to 300 ° C., and the ratio (B / A) was determined. Show. Furthermore, the relationship between the sample surface temperature and the number of H ₂ O molecules of each sample is shown in FIGS.

  As shown in FIGS. 7-12, B / A of each sample of Examples 1-3 and Comparative Examples 1-3 is 0, 0.13, 0.44, 0.68, 1.86, 0, respectively. .40, and the peak value B was not measured in the sample of Example 1.

  Next, an oxide superconducting wire was produced using each of the six types of Bi2212 powders. Table 4 shows the production conditions of the wire. The evaluation results of the critical current characteristics of each wire in liquid helium (at 4.2K, 0T) are shown in Table 3 described above. For evaluation of reproducibility of the critical current characteristics, five specimens (1 to 5) were prepared for each wire and evaluated.

The samples of Examples 1 to 3 each had a B / A of less than 0.5, and the critical current characteristic Jc value of the wire using these samples was a high value of about 4,000 A / mm ² . In addition, these wires had small variations between specimens and were excellent in reproducibility of the Jc value.

  On the other hand, the samples of Comparative Examples 1 and 2 each had a B / A value exceeding 0.5, and the critical current characteristic Jc value of the wire material using these samples was significantly lowered with an increase in B / A. Moreover, these wires had large variations between specimens, and the reproducibility of the Jc value was poor.

In addition, the sample of Comparative Example 3 in which excessive moisture was intentionally adsorbed was B / A less than 0.5, but the maximum value A was 3.0 × 10 ¹⁹ and more than 10 ¹⁸ , The wire using this sample had all critical current characteristic Jc values of zero before evaluating the variation between specimens (presence of reproducibility).

It is a figure which shows the filling process in the manufacturing process of the oxide superconducting wire by a powder in tube method. It is a figure which shows the 1st wire drawing process in the manufacturing process of the oxide superconducting wire by a powder in tube method. It is a figure which shows the multi-core incorporation process in the manufacturing process of the oxide superconducting wire by a powder in tube method. It is a figure which shows the 2nd wire drawing process in the manufacturing process of the oxide superconducting wire by a powder in tube method. It is the schematic for demonstrating the measurement principle of temperature rising desorption gas analysis. Is a diagram showing the relationship between the sample surface temperature and H ₂ O the number of molecules. Is a diagram showing the relationship between the sample surface temperature and H ₂ O the number of molecules of the sample of Example 1 (powder a). Is a diagram showing the relationship between the sample surface temperature and H ₂ O number of molecules of the sample of Example 2 (powder b). Is a diagram showing the relationship between the sample surface temperature and H ₂ O the number of molecules of the sample of Example 3 (powder c). Sample of Comparative Example 1 is a diagram showing the relationship between the sample surface temperature and H ₂ O the number of molecules of (powder d). Comparative Example 2 Sample is a diagram showing the relationship between the sample surface temperature and H ₂ O the number of molecules of (powder e). Sample of Comparative Example 3 is a diagram showing the relationship between the sample surface temperature and H ₂ O the number of molecules of (powder f).

Explanation of symbols

1 Bi2212 powder (powder)
2 Ag pipe (metal sheath material)

Claims (4)

A filling step of filling a metal sheath material with a powder of an oxide superconductor or a raw material powder thereof, and a wire drawing step of plastically processing the metal sheath material filled with the powder to produce a wire rod In the method for producing an oxide superconducting wire, 1 g of sample powder is heated from room temperature at a heating rate of 20 ° C./min in a high vacuum state of 10 ⁻⁶ Pa or higher and mass analysis is performed every 4 ° C. The number of H ₂ O molecules desorbed from the sample powder is measured using a meter, and at the time of measurement, the number of H ₂ O molecules at each measurement temperature within the temperature range of 50 to 300 ° C. of the sample powder or around the sample powder. The maximum value A of 10 ¹⁸ or less, and the peak value B of the number of H ₂ O molecules measured when the temperature is further raised within the temperature range of 200 ° C. from the measurement temperature of the maximum value A and the maximum value The ratio with A (B / A) is <0.5 Or the maximum value A is 10 ¹⁸ or less, and when the temperature is further increased within the temperature range of 200 ° C. from the measurement temperature of the maximum value A, the peak value B is only reduced by the decrease in the number of H ₂ O molecules. A method for producing an oxide superconducting wire, characterized in that an unmeasured powder is used as an appropriate powder, the appropriate powder is filled in the metal sheath material, and a wire is produced. The method for producing an oxide superconducting wire according to claim 1, wherein the powder that is inappropriate at the time of measuring the number of H ₂ O is subjected to heat treatment under reduced pressure to dehydrate the powder.   2. The method for producing an oxide superconducting wire according to claim 1, wherein the oxide superconductor powder is mainly composed of a 2212 phase of a bismuth-based oxide superconductor. 3. In the method for determining the oxide superconductor powder or the raw material powder used in the production of the oxide superconducting wire, 1 g of sample powder is used to measure the number of H ₂ O molecules absorbed and occluded in the powder. H ₂ O that is heated from room temperature at a rate of temperature increase of 20 ° C./min in a high vacuum state of 10 ⁻⁶ Pa or higher and desorbed from the sample powder at every 4 ° C. using a mass spectrometer. The number of molecules is measured, and at the time of measurement, the maximum value A of the number of H ₂ O molecules at each measurement temperature in the temperature range of 50 to 300 ° C. of the sample powder or the sample powder is 10 ¹⁸ or less, and The ratio (B / A) between the peak value B of the number of H ₂ O molecules measured when the temperature is further raised within the temperature range of 200 ° C. from the measured temperature of the maximum value A and the maximum value A is <0. 5 or a maximum value A of 10 ¹⁸ or less, and When the temperature is further increased within the temperature range of 200 ° C from the maximum temperature A, it is determined that the number of H ₂ O molecules only decreases and the peak value B is not measured is an appropriate powder. A method for determining a powder for an oxide superconducting wire, wherein the powder is used for manufacturing an oxide superconducting wire.

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