A method of manufacturing a tubular fittings of high-temperature superconducting material

 

(57) Abstract:

The essence of the invention. A method of manufacturing a tubular fittings of high-temperature superconducting material on the basis of the oxides of bismuth, calcium, strontium, copper and, in special cases, lead. The method comprises preparing a homogeneous melt of oxides with a given stoichiometry, fill it with a temperature of 900 - 1300oC in the mold, which rotates with a frequency of 200 - 1500 min-1around an axis inclined to the horizontal at an angle of not less than 15o. The cured molded part is removed from the mold and annealed for 4 to 150 hours at 700 - 900oC in oxygen-containing atmosphere. 6 C.p. f-crystals, 3 tab., 5 Il.

The present invention relates to a method of manufacturing a tubular fittings of high-temperature superconducting material on the basis of the oxides of bismuth, calcium, strontium, copper and, in this case, lead, and prepare a homogeneous melt of a mixture of oxides with a given stoichiometry, the melt with a temperature of 900 - 1300oC in the mold, rotating around the axis depending on the inner diameter with a frequency of 200 - 1500 min-1are then removed from the mold, the cured shaped det is for drinking, preparing tubular parts made of high-temperature superconducting material on the basis of the oxides of bismuth, calcium, strontium and copper, in which a homogeneous melt of the mixture of oxides to a temperature of 900 - 1100oC fill in rotating around the horizontal axis of the mold and leave it to freeze. Extracted from the mold fitting then annealed at 700 - 900oC for 4 to 150 hours in oxygen-containing atmosphere [1].

Supplying electric current through the copper wires to the low-temperature superconducting systems, in particular the coils, which must operate at 4K with cooling by liquid helium in the supply of liquid helium is transferred, on the one hand, the heat due to the temperature difference between 300K and 4K, and, on the other hand, Joul warmth educed due to the electrical resistance of copper, resulting in undesirable evaporation of helium.

Supplying electric current through the copper conductors, and through the ceramic high-temperature superconductors significantly reduced the influx of heat to the inventory of liquid helium, on the one hand, due to the lower thermal conductivity of high-temperature superconductor compared with good conductive heat the copper, and, on the other hand, due to the absence of Joule heat release, because at temperatures below Scania.

Due to its own current magnetic field in the conductor, the so-called effect of the self-magnetic field, better to use instead of rod of the contact tube, because the distribution of the current-carrying cross-section on a larger area of the self-magnetic field thereby reducing the negative impact on the current carrying capacity of the conductor.

Submitted to the inventory of liquid helium amount of heat is determined by the cross section of the electrical power supply of the high-temperature superconducting material. It should be noted that transmit a certain current through the high-temperature superconductor require a certain minimum cross-section. Obtained from the melt of oxides of bismuth, calcium, strontium, copper and, in this case, lead high-temperature superconducting material has the advantage that its current-carrying capacity at 4K approximately 50 to 100 times higher than at 77 K, i.e., the cross section of the material at lower temperatures in the region of helium cooling is excessive dimensions. Therefore, it would be preferable to calculate the current lead through the high-temperature superconductor so that the conductive section "sozdanie method of manufacturing such tubular parts made of high-temperature superconducting material on the basis of the oxides of bismuth, calcium, strontium, copper and, in this case, lead, cross sections which differ significantly from each other at their both ends. According to the invention, this is achieved by a homogeneous melt of the mixture of oxides to a temperature of 900 - 1300oC is poured into the mold, rotating around the axis depending on its inside diameter with a frequency of 200 - 1500 min-1and the axis of the mold is inclined to the horizontal at an angle of 15oafter which you extracted from the mold, the cured part is annealed at 700 - 900oC in oxygen-containing atmosphere.

The method according to the invention can also be improved by selection due to the fact that

a) the axis is inclined to the horizontal at an angle of 30o;

b) the axis is inclined to the horizontal at an angle of 20 - 60o;

in) mold is a mold with a cylindrical internal volume;

g) mold is a mold with a tapered internal displacement;

d) greater inclination of the die to the horizontal direction corresponds to the high frequency of its rotation, and Vice versa.

On the accompanying drawings in section and schematically equipment for centrifugal casting and the shaped body obtained by the method according izobret, on which there is mounted a metal mold of Fig.2 is a molded body obtained in the cylindrical mold; Fig.3 is a horizontal conical mold shaped body; Fig. 4 is a molded body obtained in the conical mold; Fig.5 is a vertical cylindrical metal mold shaped body.

In Fig.1 located on the tiltable base 9 fixed bearing 1 shaft 2 and the electric motor 5 with variable speed. On one end in the support shaft 1 2 worn continued 3 die 4 and the other end of the shaft 2 is connected with the power circuit to the motor 5. On the open end of the die 4 is wearing a closing ring 6. In the open end of the die 4 includes the spout 7, in which the crucible 8 flows down the melt. In Fig.2 shows the shaped body obtained at different angles of inclination to the horizontal of 10.

In Fig.3 shows a conical mold 4 continued 3 on which there is mounted a closing ring 6.

In Fig. 4 shows two shaped body obtained in the mold of Fig.3, and one of them received in the mold, located horizontally 10, and the other in the mold at an angle of 45o.

In Fig. 5 shows a cylindrical metal mold 4 with the continuation of the 3, the axis of which during casting spinning procedure, according to the invention, when the inclination of the axis of rotation of the die to the horizontal at a certain angle in addition to the centrifugal acceleration due to the rotation of the die is still the force of gravity, which, depending on the inclination of the axis causes the flow is still liquid melt in the lying area of the die. By varying the quantity of the melt, the frequency of rotation of the die and its angle to the horizontal can be cast pipe section which is different on the upper and lower ends by a factor of 3 to 4 (Fig.2).

Using the method according to the invention even greater difference in cross section between the upper and lower ends of the shaped bodies can be achieved by using the die 4 in the form of a truncated cone (Fig.3). In this case a reduction of the cross section depends on the geometry of the die and the degree of filling.

While using the horizontal conical die, according to the prior art, the thickness of its walls is reduced to finer end due to the tilt axis of the conical die to the horizontal is possible to achieve nearly uniform wall thickness of the cone, as in this case, the melt is drawn down by gravity and centrifugal acceleration presses the melt along the side surface to the open end (Fig.4).

the frequency of rotation, dependent on other parameters (length, shape and the free section of the mold, the viscosity of the melt, and so on), which is roughly balanced counter-force (centrifugal acceleration of Earth gravity) acting on filled in a mold melt.

The method according to the invention, when the tilt angles of 15 - 80owhen using a cylindrical die receive the shaped body, having an outside cylindrical, and inside - conical shape. When the angle of inclination 90oto the horizontal direction obtained shaped body is inside a parabolic shape (Fig.5).

In the following examples was made of high temperature superconductor composition of Bi2Sr2CaCu2O8+xwhere x = 0 to 0.3. With appropriate changes in the composition and characteristics of the pre-and post-processing using the same manufacturing and other molten high-temperature superconductors based on bismuth.

Example 1 (according to the method)

400 g of a mixture of oxides of bismuth, strontium, calcium and copper in a molar ratio of 2:2:1:2 was melted in the crucible of sintered corundum at 1500oC. a Cylindrical metal mold 4 (inner diameter 47 mm, length 100 mm) was put on in the akila 4 was horizontal (tilt angle 0o). When the mold 4 is rotated with a frequency of 750 rpm-1the melt was poured from the crucible 8 and the chute 7. After solidification of the melt from the die drew cylindrical fitting and annealed for 100 h at 840oC. Square cross section of the superconducting shaped bodies were approximately the same at both ends (Fig. 2 and table. 1).

Example 2 (according to the invention)

Example 1 was repeated with the difference that, on the one hand, the axis of the die was inclined to the horizontal at an angle of 20, 45 and 90oand that, on the other hand, used the greater frequency of rotation of the chill mould.

The square cross section of the superconducting shaped bodies differed from each other at both ends (Fig. 2 and table. 1).

Example 3 (according to the invention)

Examples 1 and 2 was repeated with the difference that they used a cylindrical mold with an inner diameter of 35 mm and which is rotated with a frequency of 1000 - 1400 min-1.

The dimensions of the superconducting shaped bodies are given in table.2.

Example 4 (according to the invention)

In accordance with examples 1 conical mold 4, one end of which had an inner diameter of 45 mm, and the other 25 mm at a length of 150 mm, was placed on a shaft 2 connected to the motor 5 with the power circuit.

Example 5 (according to the invention)

Example 4 was repeated with the difference that a mixture of oxides of bismuth, strontium, calcium, copper was added to the lead oxide.

This variorum portions of a mixture of oxides, different frequencies of rotation of the conical die and different angles of inclination of its axis are given in table.3.

1. A method of manufacturing a tubular fittings of high-temperature superconducting material on the basis of the oxides of bismuth, calcium, strontium and copper, comprising preparing a homogeneous melt of a mixture of oxides in stoichiometric ratio, pouring the melt into the mold, rotating with a frequency of 200 1500 min-1and after solidification of the melt extraction from form fitting and subsequent firing it at 700 - 900oWith over 4 150 h in oxygen-containing atmosphere, wherein rotating the mold reject at an angle of not less than 15obetween the axis of its rotation and horizontal, and the pouring of the melt is carried out at 900 - 1300oC.

2. The method according to p. 1, characterized in that the tubular fittings are made of high-temperature superconducting material, optionally containing lead oxide.

3. The method according to p. 1, featuring the Method according to p. 1, characterized in that the mold reject the angle 20 60obetween the axis of its rotation and horizontal.

5. The method according to p. 1, characterized in that as the mold using the mold with a cylindrical internal volume.

6. The method according to p. 1, characterized in that as the mold using the mold with a tapered internal volume.

7. The method according to p. 6, characterized in that the rotational speed of the die increases with increasing angle to the axis of rotation from horizontal or reduce a decrease in the angle of deviation of the axis of rotation from horizontal.

 

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1 ex

FIELD: metallurgy.

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1 tbl, 1 ex

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1 dwg, 3 ex

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