A method for preparing a short-period niobium-titanium superconducting wire and a niobium-titanium superconducting wire

Abstract

The present invention belongs to the technical field of superconducting wires, and relates to a method for preparing a short-period niobium-titanium superconducting wire and a niobium-titanium superconducting wire. The preparation method comprises: performing a first online heat treatment while stretching a NbTi / Nb / Cu primary single core rod, and immediately performing a first water cooling after the heat treatment to obtain a NbTi / Nb / Cu single core rod; placing the NbTi / Nb / Cu single core rod into a copper tube, filling the gap with a copper plug rod to form a NbTi / Cu composite ingot, and extruding the NbTi / Cu composite ingot to obtain a NbTi / Cu composite rod; performing a second online heat treatment while stretching the NbTi / Cu composite rod, and immediately performing a second water cooling after the heat treatment to obtain a NbTi / Cu composite wire; twisting and stretching the NbTi / Cu composite wire to obtain a niobium-titanium superconducting wire. The present invention solves the technical problem of a long preparation cycle of niobium-titanium superconducting wires.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting wires, and relates to a preparation method of a short-period niobium-titanium superconducting wire and the niobium-titanium superconducting wire. Background Art

[0002] NbTi / Cu superconducting wires have the advantages of good processing characteristics, stable superconducting performance and low price, and are widely used in superconducting magnets. With the development of superconducting technologies such as magnetic resonance imaging (MRI) and nuclear magnetic resonance imaging (NMR), the demand for niobium-titanium superconducting materials with high critical current density is increasing. Niobium-titanium superconducting wires need to undergo multiple (≥3) aging heat treatments to generate a pinning phase in order to obtain a high critical current density. However, during the aging heat treatment of superconducting composite wires, due to the large space occupied by the wires, aging heat treatment has become a key step in limiting the production of niobium-titanium superconducting wires with high critical current density. Summary of the invention

[0003] The purpose of the present invention is to solve the technical problem of long preparation period of niobium-titanium superconducting wire.

[0004] Based on the above purpose, the present invention provides a method for preparing a short-period niobium-titanium superconducting wire and a niobium-titanium superconducting wire to meet the needs in the art.

[0005] On the one hand, the present invention relates to a method for preparing a short-period niobium-titanium superconducting wire, which comprises: performing a first online heat treatment while stretching a NbTi / Nb / Cu primary single core rod, and immediately performing a first water cooling after the heat treatment to obtain a NbTi / Nb / Cu single core rod;

[0006] The NbTi / Nb / Cu single core rod is placed in a copper tube, and the gap is filled with a copper rod to form a NbTi / Cu composite ingot, and the NbTi / Cu composite ingot is extruded to obtain a NbTi / Cu composite rod;

[0007] The NbTi / Cu composite rod is stretched and subjected to a second online heat treatment, and immediately subjected to a second water cooling after the heat treatment, to obtain a NbTi / Cu composite wire;

[0008] The NbTi / Cu composite wire is twisted and stretched to obtain a niobium-titanium superconducting wire.

[0009] Specifically, in the preparation method of the short-period niobium-titanium superconducting wire provided by the present invention, the NbTi / Nb / Cu primary single-core rod is commercially available or prepared, and the preparation method of the NbTi / Nb / Cu primary single-core rod comprises: cleaning the NbTi rod, the Nb plate, and the Cu tube; after cleaning, completely wrapping the NbTi rod with the Nb plate and then putting it into the Cu tube to form a NbTi / Nb / Cu primary single-core ingot; extruding the NbTi / Nb / Cu primary single-core ingot to obtain the NbTi / Nb / Cu primary single-core rod.

[0010] Furthermore, in the method for preparing the short-period niobium-titanium superconducting wire provided by the present invention, the temperature of the first online heat treatment or the second online heat treatment is 500-1000° C., and the heating power is 100-5000 KW.

[0011] Furthermore, in the method for preparing a short-period niobium-titanium superconducting wire provided by the present invention, the number of the first online heat treatment or the second online heat treatment is 1 to 8 times, and the total duration of the first online heat treatment or the second online heat treatment is 100 hours to 500 hours.

[0012] Furthermore, in the method for preparing the short-period niobium-titanium superconducting wire provided by the present invention, the stretching speed of the NbTi / Nb / Cu primary single core rod or the NbTi / Cu composite rod is 5 to 150 m / min.

[0013] Furthermore, in the method for preparing the short-period niobium-titanium superconducting wire provided by the present invention, the center temperature of the material is ensured to be less than 120° C. within 3 seconds after the first water cooling or the second water cooling.

[0014] On the other hand, the present invention relates to a niobium-titanium superconducting wire, which is prepared by the above-mentioned preparation method.

[0015] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects or advantages:

[0016] (1) In the preparation of niobium-titanium superconducting wires, the prior art adopts stretching and online heat treatment separately. The present application adopts online heat treatment while stretching, which shortens the production cycle of niobium-titanium superconducting wires and saves production space.

[0017] (2) The purpose of online heat treatment is to precipitate superconducting pinning phase. This application adopts online heat treatment while stretching. During stretching, the superconducting pinning phase is broken, extended and refined. A part of the generated pinning phase becomes the "nucleation point" of the newly generated pinning phase in the next process, and another part of the generated pinning phase becomes the pinning phase of the high magnetic field, thereby improving the superconducting pinning force and performance of the niobium-titanium superconducting wire. The critical current density Ic and residual resistance ratio RRR of the niobium-titanium superconducting composite wire obtained by this method are both high.

[0018] (3) In the preparation of niobium-titanium superconducting wires, the prior art adopts natural cooling after the heat treatment. The present invention adopts water cooling immediately after the online heat treatment. When the center temperature of the material is ensured to be less than 100°C within 3 seconds after water cooling, the precipitated phase α-Ti during the heat treatment can be retained, and higher performance can be obtained, which can further effectively shorten the production cycle of niobium-titanium superconducting wires. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is described below in conjunction with embodiments; however, the present invention is not limited to the following embodiments.

[0020] The experimental methods and detection methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0021] Example 1

[0022] This embodiment provides a method for preparing a short-period niobium-titanium superconducting wire.

[0023] First, clean the NbTi rod, Nb plate, and Cu tube. After cleaning, completely wrap the NbTi rod with the Nb plate and put it into the Cu tube to form a NbTi / Nb / Cu primary single-core ingot. Extrude the NbTi / Nb / Cu primary single-core ingot to obtain a NbTi / Nb / Cu primary single-core rod. When preparing the NbTi / Nb / Cu primary single-core rod, perform online heat treatment while stretching. The online heat treatment temperature is 500°C and the stretching speed is 10m / min. The heating power of the online heating equipment is 800KW. After heating, water cooling is performed to ensure that the center temperature of the material is <110°C within 3 seconds after heating and water cooling. After stretching, the NbTi / Nb / Cu single-core rod is cut to length and straightened.

[0024] Secondly, multiple NbTi / Nb / Cu single core rods are loaded into the cleaned Cu tube, and the gaps are filled with copper rods to form NbTi / Cu composite ingots. The NbTi / Cu composite ingot is extruded to obtain NbTi / Cu composite rods. Online heat treatment is carried out while the composite rod is stretched. After heating, water cooling is carried out, and the center temperature of the material is ensured to be <110°C within 3 seconds after heating and water cooling. The online heat treatment temperature is 500°C and the stretching speed is 10m / min. The heating power of the online heating equipment is 800KW. The NbTi / Cu composite wire is twisted and stretched to the required specifications after twisting to obtain a NbTi / Cu composite wire with high efficiency, high critical current and high RRR value.

[0025] Example 2

[0026] This embodiment provides a method for preparing a short-period niobium-titanium superconducting wire.

[0027] First, clean the NbTi rod, Nb plate, and Cu tube. After cleaning, completely wrap the NbTi rod with the Nb plate and put it into the Cu tube to form a NbTi / Nb / Cu primary single-core ingot. Extrude the NbTi / Nb / Cu primary single-core ingot to obtain a NbTi / Nb / Cu primary single-core rod. When preparing the NbTi / Nb / Cu primary single-core rod, perform online heat treatment while stretching. After heating, water cool it, and ensure that the center temperature of the material is <100°C within 3 seconds after heating and water cooling. The online heat treatment temperature is 700°C, and the stretching speed is 80m / min. The heating power of the online heating equipment is 2000KW. After stretching, the NbTi / Nb / Cu single-core rod is cut to length and straightened.

[0028] Secondly, multiple NbTi / Nb / Cu single core rods are loaded into the cleaned Cu tube, and the gaps are filled with copper rods to form NbTi / Cu composite ingots. The NbTi / Cu composite ingot is extruded to obtain NbTi / Cu composite rods. Online heat treatment is carried out while the composite rod is stretched. After heating, water cooling is carried out, and the center temperature of the material is ensured to be <100°C within 3 seconds after heating and water cooling. The online heat treatment temperature is 700°C and the stretching speed is 80m / min. The heating power of the online heating equipment is 2000KW. The NbTi / Cu composite wire is twisted and stretched to the required specifications after twisting to obtain a NbTi / Cu composite wire with high efficiency, high critical current and high RRR value.

[0029] Example 3

[0030] This embodiment provides a method for preparing a short-period niobium-titanium superconducting wire.

[0031] First, clean the NbTi rod, Nb plate, and Cu tube. After cleaning, completely wrap the NbTi rod with the Nb plate and put it into the Cu tube to form a NbTi / Nb / Cu primary single-core ingot. Extrude the NbTi / Nb / Cu primary single-core ingot to obtain a NbTi / Nb / Cu primary single-core rod. When preparing the NbTi / Nb / Cu primary single-core rod, perform online heat treatment while stretching. After heating, water cool it, and ensure that the center temperature of the material is <100°C within 3 seconds after heating and water cooling. The online heat treatment temperature is 900°C, and the stretching speed is 120m / min. The heating power of the online heating equipment is 4500KW. After stretching, the NbTi / Nb / Cu single-core rod is cut to length and straightened.

[0032] Secondly, multiple NbTi / Nb / Cu single core rods are loaded into the cleaned Cu tube, and the gaps are filled with copper rods to form NbTi / Cu composite ingots. The NbTi / Cu composite ingot is extruded to obtain NbTi / Cu composite rods. Online heat treatment is carried out while the composite rod is stretched. After heating, water cooling is carried out, and the center temperature of the material is ensured to be <100°C within 3 seconds after heating and water cooling. The online heat treatment temperature is 900°C and the stretching speed is 120m / min. The heating power of the online heating equipment is 4500KW. The NbTi / Cu composite wire is twisted and stretched to the required specifications after twisting to obtain a NbTi / Cu composite wire with high efficiency, high critical current and high RRR value.

[0033] Comparative Example 1

[0034] Same as Example 1, except that the center temperature of the material is 300° C. within 3 seconds after water cooling.

[0035] Comparative Example 2

[0036] The same as Example 1, except that the niobium-titanium superconducting wire is prepared by a conventional method (the preparation steps refer to CN104123997A, no water cooling is performed, and heat treatment is performed in a vacuum heat treatment furnace).

[0037] The niobium-titanium superconducting wire prepared in the above embodiment was tested, and the experimental results are shown in Table 1.

[0038] Table 1 Critical current density of niobium-titanium superconducting wire

[0039]

[0040] The Jc (4.2K, 5T) obtained by the method of this patent in Examples 1 to 3 is equivalent to the critical current density of the niobium-titanium superconducting wire prepared by the conventional method, but the preparation time is greatly reduced.

[0041] Embodiments 1 to 3 retain a large amount of flux pinning phase after water cooling with better effect, and the Jc (4.2K, 5T) of comparative example 1 in which the material center temperature is 300°C within 3 seconds after water cooling is higher.

[0042] The NbTi / Cu superconducting wire prepared by conventional preparation method is drawn from the first Until the last aging heat treatment The production cycle takes 480 hours (400 hours of heat treatment and 80 hours of stretching). to The production cycle takes 80 hours. Immediate water cooling after heat treatment can retain the precipitated phase α-Ti during heat treatment and obtain higher performance. Using the same preparation process, the Jc of the water-cooled superconducting wire is 3% higher than that of the air-cooled superconducting wire.

[0043] As described above, the basic principle, main features and advantages of the present invention are well described. The above embodiments and descriptions are only descriptions of the preferred embodiments of the present invention, and the present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the protection scope determined by the present invention.

Claims

1. A method for preparing a short-period niobium-titanium superconducting wire, characterized in that: include: The NbTi / Nb / Cu primary single core rod is stretched and subjected to a first online heat treatment, and immediately subjected to a first water cooling after the heat treatment, to obtain a NbTi / Nb / Cu single core rod; The NbTi / Nb / Cu single core rod is placed in a copper tube, and the gap is filled with a copper rod to form a NbTi / Cu composite ingot, and the NbTi / Cu composite ingot is extruded to obtain a NbTi / Cu composite rod; The NbTi / Cu composite rod is stretched and subjected to a second online heat treatment, and immediately subjected to a second water cooling after the heat treatment, to obtain a NbTi / Cu composite wire; Twisting and stretching the NbTi / Cu composite wire to obtain a niobium-titanium superconducting wire; Ensure that the center temperature of the material is less than 120°C within 3 seconds after the first water cooling and the second water cooling; The NbTi / Nb / Cu primary single core rod comprises NbTi, Nb and Cu in order from the inner core to the outer layer.

2. The method for preparing a short-period niobium-titanium superconducting wire according to claim 1, characterized in that: The temperature of the first online heat treatment or the second online heat treatment is 500-1000° C., and the heating power is 100-5000 KW.

3. The method for preparing a short-period niobium-titanium superconducting wire according to claim 1, characterized in that: The number of times of the first online heat treatment or the second online heat treatment is 1 to 8 times, and the total duration of the first online heat treatment or the second online heat treatment is 100 hours to 500 hours.

4. The method for preparing a short-period niobium-titanium superconducting wire according to claim 1, characterized in that: The NbTi / Nb / Cu primary single core rod or the NbTi / Cu composite rod is stretched at a speed of 5 to 150 m / min.

5. A niobium-titanium superconducting wire, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 4.

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