JPS6025845B2 - Manufacturing method of composite superconducting conductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a composite superconducting conductor used for superconducting power transmission cables, various superconducting magnets, and the like.

A composite superconducting conductor consists of a superconducting material and a normal conducting material. For example, a superconducting wire with a diameter of 5 mm to 250 threads is placed in a normal conducting material such as copper, aluminum, other metals, or alloys of these metals. These wires are embedded into round wires, flat wires, and hollow wires.

Figure 1 is a cross-sectional view showing an example of a conventional composite superconducting conductor, in which a large number of superconducting strands 1 are made of a normal conducting material 2 such as copper or aluminum.
It is embedded inside and finished as a flat wire.

An insulator 3 is placed on the edge of the rectangular cross section, and the coil is wound so as to be in contact with the edge of the coil through the insulator 3. Since the wire exhibits superconductivity, it does not generate heat under a constant magnetic field and constant current, but it generates loss due to magnetization when the current changes over time. Furthermore, if the superconductivity is broken for some reason, a large amount of Joule heat will be generated. Therefore, in order to make a part of the composite superconducting conductor, for example, the short side 4 of the rectangular cross section, a cooling surface that is cooled by coming into direct contact with liquid helium, a gap 10 (width 1 to 5 kites) are provided. The conditions for preventing the expansion of the superconducting region are given by the following equation.

Mackerel＜・・．．・・・．・・・．・tl'Aburu Hinagisonden Wanimari's Showaniq: Cooling heat flow rate.

Given the current value and cooling conditions, the cooling perimeter P and the cross-sectional area A of the charged conductor must be increased in order to satisfy equation {1).

That is, a large amount of normal conductive material must be used, which is a major factor in increasing costs, such as increasing the size and weight of the diamond counterfeit. As one countermeasure against this problem, a method is known in which a rectangular groove with one rib in depth and one sail in middle is provided on the surface of the composite superconducting conductor on the pitch 2 side, as described in Japanese Patent Publication No. 8 of Japanese Patent Publication No. 45-22. It is being

Although this method is expected to have the effect of increasing the cooling perimeter P by about twice, it cannot be said that it is still sufficient. When placed in a narrow cooling channel like a superconducting magnet, such a cooling surface does not necessarily provide a cooling amount (P×q) proportional to the increase in surface area, but rather becomes lower. In addition, in order to increase P, we added
When deep grooves are carved with a narrow pitch as described in the publication, chips adhere to the conductor and get mixed into the coil.
There is a possibility of electrical short-circuiting between the conductors 2 and 2 that narrow the insulator 3 or between the coils via the gap 10 for liquid helium. The present invention was made to solve the above-mentioned problems, and includes a large number of closely spaced grooves each having an acute angle at the bottom in the skin band of the cooling surface of a composite superconducting conductor. A large number of ridges are separated from each other and have sharply tapered tips, and are formed by plowing without exposing the cut shoulder, thereby increasing the amount of cooling.

An embodiment of the method of the present invention will be described below with reference to FIG.

FIG. 2 shows a case where a cooling surface is formed on the short side of the rectangular cross section of a composite superconducting conductor finished into a rectangular wire, and an insulator 3 is stretched on the farthest side. First, a large number of superconducting wires 1 are embedded in a normal conductive material 2 such as copper or aluminum. then in the skin zone of the cooling surface a number of successively adjacent parallel first grooves 5;
forming a number of consecutive parallel ridges 6 separated by first grooves 5; The processing method used at this time is to plastically deform the epidermis by plowing it up without cutting it, thereby creating fine, deep grooves that are close to each other. In addition, a textbook is prepared for machining bits with the same or slightly different cutting edge shapes, and machining is performed in stages. The bit for raising the plow is
A cut-out cutting edge, that is, one with an obliquely formed blade may be used. As a result, the groove 5 has an acute angle at the bottom,
Further, a large number of parallel raised portions 6 separated by the first groove 5 have tips tapered to an acute angle portion. First groove 5
The size is, for example, 0.2 legs in the middle, 0.8 ribs in depth, and 0.4 skin in pitch. Therefore, the size of the raised portion 6 is also medium.
2 jobs, 0.8 ribs in height. In such a configuration, the surface area is three times that of the unprocessed surface. FIG. 3 is a diagram for explaining another embodiment of the method for manufacturing a composite superconducting conductor of the present invention, and is an enlarged view of the skin band on the cooling surface of the composite superconducting conductor.

In Fig. 3, first, the normal conducting material 2 of the composite superconducting conductor is
A knurling machine equipped with a roll having protrusions for incrementing numbers is pressed onto the surface, and the composite superconducting conductor is moved in the direction of rotation of the roll. As a result, a large number of relatively shallow second grooves 8 with small intervals are formed at a constant pitch in the skin band of the normal conductive material 2. After the second groove 8 is formed, the first groove 5 is processed in a direction intersecting with the second groove 8. A textbook for groove machining tools with the same or slightly different cutting edge formation is prepared, and the machining is performed step by step. In this processing, the surface of the normal conductive material 2 is not cut away, but is deformed in a plowing manner, so that fine, deep grooves are formed close to each other. As a result, in the skin zone of the cooling surface of the normal conductive material 2, a large number of successive parallel first grooves 5 with small intervals each having an acute angle at the bottom are formed.
and a V-shaped interval separated by this groove 5, the tip tapering at an acute angle, the depth from the tip being shallower than the depth of the first groove 5, and the bottom being mirror-slanted at an acute angle. A raised portion 6 having a small valley 7 is formed. For example, the first
In the groove 5, 0.2 skin, depth 0.8 fence, pitch 0.4 rib,
In the case of valley 7 with a pitch of 0.6 and a depth of 0.4, the surface area reaches about 3.5 times that of the unprocessed surface. The effects obtained in this way will be explained with reference to FIG.

In Fig. 4, in order to express the cooling performance, the horizontal axis shows the temperature Tw of the conductor surface and the temperature Tb (
4.2 K), and the vertical axis is the heat flow east q (the value obtained by dividing the heat flow Q by the surface area A) transferred from the conductor surface to the liquid helium. Here, the projected area (ie, the surface area of the unprocessed surface) is taken as A. The size of the cooling channel is approximately 2.3 mm in clearance, approximately 5 mm in length, and 1 mm in length, and Tw is the average value in the length direction. curve a
is the characteristic of a normal polished copper surface, and curved image b is a characteristic of the surface of the embodiment shown in FIG. As the heat flow east q is raised, the transfer is first carried out by nucleate boiling, and a certain heat flow east q
At max, it transitions to film boiling. Here, if q is lowered, qmj
Return to the boiling point again at n. Since experiments cannot be performed between qmax and qmjn, the values are estimated. In the unlikely event that a superconducting conductor transitions to the boiling region due to an increase in temperature for some reason, it will return to the nucleate boiling region and recover the superconducting properties if the cause disappears, so it is desirable that qmax and qmin be as high as possible, especially qmin. has a large impact.

qmax of curve b does not increase much compared to qmax of curve a. This shows that with a fine surface structure as shown in the example, an increase in qmax corresponding to an increase in surface area cannot necessarily be obtained in a narrow space. on the other hand,
The qmjn of the curve b is more than four times the qmln of the curve a, and there is an increase in the heat flow east by an amount more than proportional to the increase in the surface area. It is thought that the fine surface structure shown in this example impedes the stability of film boiling. It is thought that the acute angles of the ridges have a positive effect on the 〈. As described above, the manufacturing method of the present invention does not create a cut layer in the skin zone of the cooling surface of the composite superconducting conductor by plowing.
By forming a large number of grooves with acute-angled bottoms and at the same time forming a large number of ridges separated by the grooves and tapered at acute angles, the critical heat flow for film boiling on the cooling surface is reduced compared to conventional methods. East qmjn can be significantly increased.

Moreover, when forming the groove, no chips are produced as in cutting, so there is no risk of electrical short circuits caused by chips.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional composite superconducting conductor, FIG. 2 is an enlarged perspective view of a composite superconducting conductor manufactured by an embodiment of the method of the present invention, and FIG. 3 is an implementation of the method of the present invention. FIG. 4 is an enlarged perspective view of the main part of the composite superconducting conductor manufactured according to the example, and is a characteristic diagram comparing the conventional composite superconducting conductor and the composite superconducting conductor shown in FIG. 3 manufactured by the method of the present invention. 1...Superconducting wire, 2...Normal conductive material, 3...
...Insulator, 5...First groove, 6...
...ridge, 7...valley. O figure leopard figure 2 figure 3 figure and 4 figure

Claims (1)

[Claims] 1 A plowing process is performed over part or all of the surface of a composite superconducting conductor made of a superconducting material and a normal conducting material, and a large number of successively approaching first grooves with small intervals are formed. , and a large number of protuberances separated by the first groove and each having an acutely tapered tip. 2. First, a large number of closely spaced second grooves are formed by machining over part or all of the surface of a composite superconducting conductor made of a superconducting material and a normal conducting material, and then the second grooves are The plowing process is performed to be deeper than the second groove in the direction intersecting with the second groove.
a plurality of consecutively approaching first grooves deeper than the grooves of the first groove;
A method for producing a composite superconducting conductor, the method comprising: forming a large number of ridges having a large number of V-shaped valleys that are shallower than the grooves of the composite superconducting conductor.