JPH0443515A - Manufacturing method of Nb↓3Sn superconducting wire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a Nb3Sn-based superconducting wire, and more specifically, to a method for manufacturing an Nb3Sn-based compound superconducting wire used as a winding material of an electromagnet for generating a high magnetic field. Naru N
The present invention relates to a method for manufacturing bzSn-based superconducting wire.

[Conventional technology] Superconducting wire consumes almost no power, allows large currents to flow, and remains superconducting even in high magnetic fields, so its use as a winding material for electromagnets for generating high magnetic fields is progressing. It is being The most widely used wire of this type is NbTi alloy wire, but the magnetic field generated by this alloy wire has a limit of 9 Tesla, so if a higher magnetic field than this is required, is Nb5Sn with high critical magnetic field
A type of compound wire is used. This Nb3Sn wire is made of a Cu-Sn alloy base and N
There is one that consists of three types of b-substrates. The conventional manufacturing method for this wire rod is as shown in Fig. 2.
The process consists of a Nb base (6) that becomes a filament, a Nb-Sn diffusion barrier (8), and a stabilized Cυ (5). , intermediate annealing is required every 40% reduction in cross-sectional diameter, and the number of annealing operations is extremely large to produce a practical wire rod, which poses a problem in terms of production cost.

Another method for manufacturing Nbs'Sn superconducting wire is Cu and Sn.
There is one that consists of a base and a Nb base. The conventional manufacturing method for this wire rod is based on a 3Sn substrate (7
), Cu (5), Nb base (6), Sn diffusion barrier (8), and heat treated.No Cu-Sn alloy is used, and all metals with excellent workability are used, making it extremely Since it has excellent workability, desired shapes and dimensions can be obtained without one intermediate annealing.

Regardless of the manufacturing method mentioned above, the Nb3Sn superconducting wire has a viscosity of 600 to 800, either before or after winding the electromagnet coil.
NbJn generation heat treatment is performed at a temperature of several tens to several hundreds of hours. In the bronze method shown in Figure 2, this heat treatment
Sn in u-Sn alloy (3) is Nb (filament) (
6) to generate Nb and 3Sn. At this time, a Sn diffusion barrier (8) is provided to prevent the diffusion of Sn up to the stabilizing Cu (5) of the outer skin. In the internal diffusion method shown in Fig. 3, the Sn substrate (7) first becomes carbon
It diffuses into Cu-5n to form a Cu-5n alloy, and Sn in Cu-5n reacts with Nb (filament) (6) to generate Nb*Sn. In addition, the stabilization of the outer skin C
Similar to the bronze method, there is a 3Sn diffusion barrier (8) up to u(5) to prevent Sn diffusion.

These NbaSn superconducting wires have a good track record of being used as superconducting wires for high magnetic fields.

However, recently there has been a strong demand for Nb-Sn superconducting wires that are stable against rapid magnetic field fluctuations, and Nb5S for pulse
Development of n-rays is progressing. Therefore, from the reduction of AC loss in Nb3Sn wire, Nb3Sn without stabilizing Cu is 1
m-units are now being produced.

The stabilizing copper in the outer sheath of Nb5Sn superconducting wires has been replaced by a Cu-Sn alloy (bronze) with high electrical resistance, mainly to reduce coupling loss and eddy current loss. Nb=S for pulse
Conventional Nb5Sn by internal diffusion method as n superconducting wire
! In i, as shown in FIG. 4, 3Sn substrate (7), Nb
The base body (6) is made of Cu (5), and Nb3Sn formation heat treatment is performed without providing a Sn diffusion barrier.
This is a method in which the unreacted Sn of b (filament) (6) forms the Cu matrix containing the outer skin into bronze (Cu-Sn alloy). In the bronze method Nb=Sn wire, as shown in FIG.
6), and the matrix has been made of bronze (Cu) from the beginning.
-Sn alloy), but Sn in the cross-sectional direction of the Nb5Sn wire
Due to the uniform diffusion of the Sn diffusion barrier, no Sn diffusion barrier is provided.

As described above, each of the Nb3Sn superconducting wires is subjected to Nb3Sn generation heat treatment either before or after winding the coil of the electromagnet. Nb3Sn generation heat treatment is performed at a high temperature of 600 to 800°C.
In addition, since the heat treatment is for a long time of several tens to hundreds of hours, Sn vaporizes from the Cu-Sn alloy of the outer skin, and the sixth
As shown in the figure, the surface of the superconducting wire consisting of Nb5Sn (2) and CLI-Sn substrate (3) enters a de-Sn phenomenon state, and void defects (4) occur.

[Problems to be Solved by the Invention] In the conventional method for manufacturing Nb3Sn superconducting wires as described above, void-like defects occur on and near the surface of the NbxSn superconducting wires due to removal of Sn, and the homogeneity of the surface cannot be maintained. Therefore, as a winding material for superconducting electromagnets, the strength of the wire material is significantly reduced against bending strain and tensile/compressive stress. Further, there were other problems such as the Sn concentration in the bronze matrix decreased due to the Sn removal phenomenon, the amount of NbaSn produced decreased, and the critical current characteristics also deteriorated.

This invention was made in order to solve the above-mentioned problems, and its purpose is to obtain a method for manufacturing a sound NbrSn superconducting wire for pulse use that is homogeneous, has no surface defects, and has no deterioration in critical current characteristics. do.

[Means for Solving the Problems] A method for manufacturing an Nb3Sn superconducting wire according to the present invention provides a method for producing a Nb3Sn superconducting wire having a thickness of 0.5 to
1011m of Cr plating treatment followed by heat treatment 2. Effects In this invention, the Sn removal phenomenon that occurs during the Nb5Sn formation heat treatment of the Nb=Sn superconducting wire without stabilizing copper is
Prevented by r plating treatment.

“Example J An embodiment of the present invention will be described below with reference to the drawings.

First, as shown in FIG.
A Nb5Sn II made by the internal diffusion method shown in FIG. 3, consisting of an n base and an Nb base, is manufactured and prepared to have a desired wire diameter II.

Next, this wire was labeled with the following message: ``Product name: Asahi From Special CUH''.

Plating thickness 4u at current density 20^/dea” in plating bath
m continuous Cr plating treatment. Next, this Cr-plated Nb3Sn was subjected to a normal Nb3Sn generation heat treatment.
00℃.

Heat treatment is performed for 70 hours.
In the case of the bronze method, the Cu-5n alloy is homogenized at 0°C. On the other hand, in the internal diffusion method, Sn is uniformly diffused into Cu to form a Cu-5n alloy. Further 500℃~70
At 0° C., Sn in these Cu-5n alloys reacts with the Nb substrate to generate Nb5Sn.

Further, unreacted Sn of the Nb substrate (6) remains to form a Cu-5n (bronze) matrix with high electrical resistance.

Cu-5n of Nb5Sn superconducting wire at 550℃~700℃
Since the vaporization of Sn on the surface is suppressed by the Cr plating coating,
The occurrence of void defects is prevented, and the N
Cu-5n substrate with b1Sn filament (2) (
3) A healthy (pulse use) Nb3Sn superconducting wire with a Cr plating layer (1) on the surface is obtained.

Note that Cr plating hardly reacts with Sn and Cu even when subjected to Nb3Sn generation heat treatment, and is stable without deterioration even at high temperatures for a long time. The atmosphere for heat treatment is normal N.
As with b5Sn production heat treatment, there is no problem in vacuum or inert gas atmosphere. Furthermore, since Cr plating covers the entire surface of the Wb3Sn superconducting wire, it increases mechanical strength and
It has a sufficiently high electrical resistance and is useful as a pulse NbzSn superconducting wire.

Furthermore, as an alternative to Cr plating, Ta-V・N
i-plating is also easily considered. In case of Ni plating, Cr
Cr is not stable because it reacts with Sn and Nb.
It is possible to partially apply 3Sn by selecting the heat treatment conditions for formation at low temperature and short time.

[Effects of the Invention] As described above, according to the present invention, by applying Cr plating to a thickness of 0.5 to 101 J+1 on the surface of a pulse Nb3Sn wire without stabilizing copper, and then heat-treating it, Nb
This has the effect of preventing the Sn removal phenomenon that occurs during aSn generation heat treatment, eliminating surface void defects, and improving stability.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a wire rod obtained by an embodiment of the present invention, Figures 2 to 5 are cross-sectional views of conventional wire rods (unheated), and Figure 6 is a cross-sectional view of a conventional pulse superconducting wire rod. FIG. (1)・-Cr plating, (2)・・Nb1Sn, (3
)-□-Cu-Sn (bronze) substrate, (4)...void defect, (5)Cu, <6)--Nb substrate (filament), (7)=Sn substrate, (8)...Ta or Nb Sn diffusion barrier. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] Nb_3 consisting of Cu-Sn alloy base and Nb base
A step of applying Cr plating to a thickness of 0.5 to 10 μm on the surface of a superconducting wire made of either a Sn superconducting wire or a Nb_3Sn superconducting wire made of Cu, a Sn base, and a Nb base; A method for manufacturing a Nb_3Sn-based superconducting wire, which comprises a step of heat-treating the superconducting wire.