WIC superconducting wire and preparation method thereof

Abstract

The invention belongs to the technical field of superconducting wires, and relates to a WIC superconducting wire and a preparation method thereof. The invention provides a preparation method of a WIC superconducting wire, and the method comprises the steps: putting an NbTi / Cu composite round wire into a copper slot wire with a semicircular groove, and completing the preliminary combination through a constraint mold; and then symmetrically arranging another copper slot wire with a semicircular groove, and completing final metallurgical bonding through welding to obtain the WIC superconducting wire. According to the invention, the technical problems of poor combination of a round wire and a copper slot wire, difficulty in guaranteeing the precision and the like existing in a conventional preparation method of a large-specification and high-copper-ratio WIC superconducting wire are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting wires and relates to a WIC superconducting wire and a preparation method thereof. Background Art

[0002] Magnetic resonance imaging (MRI) is an important modern medical imaging diagnosis and treatment method. Its core and foundation is NbTi superconducting wire. Among them, Wire in channel (WIC) superconducting wire has the advantages of high copper-to-superconducting ratio and low copper processing rate, which makes its processing cost low and the prepared magnet runs stably and safely. Therefore, it has become the dominant material for preparing superconducting magnets, which are key components of magnetic resonance imaging systems (MRI). With the advancement of technology, ultra-high field MRI equipment requires larger specifications and higher copper ratios. At present, the conventional preparation method of WIC superconducting wire adopts the method of directly welding NbTi / Cu composite round wire with U-shaped groove copper groove wire, and increasing the wall thickness of copper groove wire raw material to improve the specifications and copper ratio of WIC superconducting wire. However, as the specifications and copper ratio are further increased, technical problems such as poor bonding between round wire and copper groove wire, inability to process and poor forming effect often occur. Summary of the invention

[0003] The purpose of the present invention is to solve the technical problems that the conventional preparation method of WIC superconducting wire with large specifications and high copper ratio has poor combination of round wire and copper slot wire and difficulty in ensuring precision. In this regard, the present invention provides a WIC superconducting wire and a preparation method thereof to solve this need in the art.

[0004] On the one hand, the present invention relates to a method for preparing a WIC superconducting wire, which comprises: placing a NbTi / Cu composite round wire into a copper groove wire with a semicircular groove, completing preliminary bonding through a constraining mold; then symmetrically arranging another copper groove wire with a semicircular groove, completing final metallurgical bonding through welding, and preparing the WIC superconducting wire.

[0005] Furthermore, in the preparation method of the WIC superconducting wire provided by the present invention, the copper groove wire with a semicircular groove adopts a low-oxygen C11000 copper rod, which is sequentially subjected to a first annealing heat treatment, a first rolling flattening, a preliminary forming by a rectangular mold of a corresponding specification, a second annealing heat treatment, and a second rolling by a set of rectangular concave molds and semicircular convex molds to finally form the copper groove wire with a semicircular groove.

[0006] Furthermore, in the method for preparing the WIC superconducting wire provided by the present invention, the low-oxygen C11000 copper rod satisfies RRR>600 and the O content is below 280 ppm, and the final forming speed is 80-120 m / min.

[0007] Furthermore, in the method for preparing the WIC superconducting wire provided by the present invention, the copper groove wires of the two semicircular grooves symmetrically arranged in the NbTi / Cu composite round wire have a matching clearance of less than 0.1 mm.

[0008] Furthermore, in the method for preparing the WIC superconducting wire provided by the present invention, the copper groove wires with the two semicircular grooves have outer R angles with the same radius.

[0009] Furthermore, in the method for preparing the WIC superconducting wire provided by the present invention, in the preliminary combining step, the NbTi / Cu composite round wire is placed into a copper groove wire with a semicircular groove at a speed of 50 to 70 m / min.

[0010] Furthermore, in the preparation method of the WIC superconducting wire provided by the present invention, the welding is tin soldering, and after the NbTi / Cu composite round wire is symmetrically provided with two copper groove wires with semicircular grooves, they are immersed in tin liquid at the same time, and after passing through a forming mold and a cooling device, the final metallurgical bonding is completed.

[0011] On the other hand, the present invention relates to a WIC superconducting wire, which is prepared by the preparation method of the WIC superconducting wire.

[0012] Furthermore, in the WIC superconducting wire provided by the present invention, the specification of the WIC superconducting wire is not less than 4 mm×2.4 mm.

[0013] Furthermore, in the WIC superconducting wire provided by the present invention, the copper ratio of the WIC superconducting wire is not less than 30.0.

[0014] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: The present invention solves the problems that the prior art generally adopts direct welding of round wire and large-sized copper slot wire, the round wire and the copper slot wire of high-copper ratio WIC superconducting wire are not well bonded, and the dimensional accuracy of the groove of the large-sized copper slot wire is difficult to ensure, and explores a preparation route of high-copper ratio WIC superconducting wire with higher production efficiency and better forming effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1Schematic diagram of a copper groove wire with two semicircular grooves symmetrically arranged on a NbTi / Cu composite circular wire.

[0017] Description of the accompanying drawings: 1. Copper groove wire with semicircular grooves; 2. NbTi / Cu composite round wire. DETAILED DESCRIPTION

[0018] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials can be purchased on the market unless otherwise specified. The % in the following embodiments, unless otherwise specified, are all mass percentages. The ratios in the following embodiments, unless otherwise specified, are all mass ratios.

[0019] Example 1 This embodiment provides a method for preparing a WIC superconducting wire.

[0020] S100, obtaining an assembled NbTi / Cu composite round wire.

[0021] S110, subjecting the low-oxygen C11000 copper rod to multiple annealing heat treatments, and performing one-time rolling and cooperating with a rectangular mold to realize preliminary rectangular forming.

[0022] In the embodiment provided by the present invention, the low oxygen C11000 copper rod needs to meet RRR>600, the O content needs to be controlled below 280ppm, and the grain structure is optimized after the first annealing heat treatment (350℃×6h). It is initially formed by a rolling flattening and a rectangular mold of corresponding specifications, and a secondary annealing heat treatment (200~250℃×3h) is required after forming.

[0023] S120, a set of rectangular concave dies and semicircular convex dies are used together to form semicircular grooves through secondary rolling.

[0024] In the embodiment provided by the present invention, the fitting clearance between the two molds should be less than 0.1 mm to ensure that the molding dimension deviation is controlled within a certain range.

[0025] S130, the final forming process is carried out by a precision-sized mold, so that the copper groove line of the semicircular groove has a smooth and uniform outer R angle.

[0026] In the embodiment provided by the present invention, the final forming speed is 80-120 m / min, which ensures that the copper groove wire has a smooth outer R angle with a consistent radius.

[0027] S140, ultrasonically clean the copper groove wire with the semicircular groove prepared above, put the round wire into a copper groove wire with a semicircular groove in advance, and complete the preliminary combination through the constraining mold.

[0028] In the embodiment provided by the present invention, the copper slot wire needs to be ultrasonically cleaned to remove oil stains on the surface and in the slot. During the inlay process, the round wire needs to be slowly placed in the groove of the copper slot wire below at a speed of 40 to 70 m / min. Generally, the constraint mold needs to be selected to be 200 to 300 μm larger than the combination of the copper slot wire and the round wire, which mainly plays a constraint role to ensure that the slot wire and the round wire are not deformed.

[0029] S150, such as Figure 1 As shown, the above combined wires are soldered together with another copper groove wire with a semicircular groove by soldering to complete the final metallurgical bonding.

[0030] In the embodiment provided by the present invention, another copper groove wire with a semicircular groove is placed with the groove surface facing downward on the combined wire, and is immersed in tin liquid at the same time according to the requirements of the inlay welding process, with a welding temperature of 60-100°C and a speed of 100-150m / min. After passing through the forming mold, it enters the cooling water to achieve metallurgical bonding.

[0031] Example 2 This embodiment provides a method for preparing a WIC superconducting wire.

[0032] First, clean and dry oxygen-free copper tubes, upper covers, lower covers, single core rods and copper plugs are assembled. Then, electron beam welding is used to weld the assembled 54-core NbTi / Cu composite ingots. The vacuum degree during welding must be less than 10 - 5mbar, the welding is first carried out with 6-point positioning, and then repeated sealing is performed to ensure the quality of the weld. The welded 54-core NbTi / Cu composite ingot is placed in a resistance furnace for uniform heating, and then extruded to obtain a NbTi / Cu composite rod. In the subsequent drawing process of the NbTi / Cu composite rod, multiple aging heat treatments are required. During the aging heat treatment process, the vacuum degree of the heat treatment furnace must be less than 0.1Pa, and the material temperature must be continuously monitored; it is also necessary to ensure that the lubrication is sufficient during the drawing process to prepare a Φ1.0mm 54-core NbTi / Cu composite wire. Low-oxygen C11000 copper rods that meet RRR>600 and O content<280ppm are selected, and the grain structure is optimized after the first annealing heat treatment (350℃×6h). After one rolling flattening, it is initially formed by a rectangular die of corresponding specifications, and a secondary annealing heat treatment (200℃×3h) is required after forming. A set of rectangular concave dies and semicircular convex dies are used for secondary rolling to form a Φ1.02mm semicircular groove. Finally, after passing through the forming mold, the copper slot wire has a smooth outer R angle with consistent radius, and the copper slot wire preparation is completed. The copper slot wire prepared above needs to be ultrasonically cleaned to remove oil stains on the surface and in the slot. During the inlay process, the round wire needs to be slowly placed in the groove of the copper slot wire below at a speed of 65m / min. The mold passed through is selected to be 200-300μm larger than the combination of the copper slot wire and the round wire to ensure that the slot wire and the round wire are not deformed. Place the groove of the other copper slot wire face down on top of the combined wire, and immerse it in the tin liquid at the same time according to the requirements of the inlay welding process. The welding temperature is 65℃ and the speed is 130m / min. After passing through the forming mold, enter the cooling water to achieve metallurgical bonding. Complete the preparation of WIC superconducting wire with a large specification of (4.0×2.4) mm and a copper ratio of up to 30.0.

[0033] Example 3 This embodiment provides a method for preparing a WIC superconducting wire.

[0034] First, clean and dry oxygen-free copper tubes, upper covers, lower covers, single core rods and copper plugs are assembled. Then, electron beam welding is used to weld the assembled 54-core NbTi / Cu composite ingots. The vacuum degree during welding must be less than 10 - 5mbar, the welding is first carried out by 6-point positioning, and then repeated sealing is performed to ensure the quality of the weld. The welded 54-core NbTi / Cu composite ingot is placed in a resistance furnace for uniform heating, and then extruded to obtain a NbTi / Cu composite rod. In the subsequent drawing process of the NbTi / Cu composite rod, multiple aging heat treatments are required. During the aging heat treatment process, the vacuum degree of the heat treatment furnace must be less than 0.1Pa, and the material temperature must be continuously monitored; it is also necessary to ensure that the lubrication is sufficient during the drawing process to prepare an 85-core NbTi / Cu composite wire with a specification of Φ1.2mm. Low-oxygen C11000 copper rods that meet RRR>600 and O content<280ppm are selected, and the grain structure is optimized after the first annealing heat treatment (350℃×6h). After one rolling flattening, it is initially formed by a rectangular die of corresponding specifications, and a secondary annealing heat treatment (200℃×3h) is required after forming. A set of rectangular concave dies and semicircular convex dies are used for secondary rolling to form a Φ1.22mm semicircular groove. Finally, after passing through the forming mold, the copper slot wire has a smooth outer R angle with consistent radius, and the copper slot wire preparation is completed. The copper slot wire prepared above needs to be ultrasonically cleaned to remove oil stains on the surface and in the slot. During the inlay process, the round wire needs to be slowly placed in the groove of the copper slot wire below at a speed of 55m / min. The mold passed through needs to be 200-300μm larger than the combination of the copper slot wire and the round wire, which mainly plays a restraining role to ensure that the slot wire and the round wire do not deform. Place the groove of the other copper slot wire face down on top of the combined wire, and immerse it in the tin liquid at the same time according to the requirements of the inlay welding process, with a welding temperature of 70℃ and a speed of 120m / min. After passing through the forming mold and entering the cooling water, metallurgical bonding is achieved. The preparation of WIC superconducting wire with a large specification of (5.0×3.2) mm and a copper ratio of up to 38.0 is completed.

[0035] Example 4 This embodiment provides a method for preparing a WIC superconducting wire.

[0036] First, clean and dry oxygen-free copper tubes, upper covers, lower covers, single core rods and copper plugs are assembled. Then, electron beam welding is used to weld the assembled 54-core NbTi / Cu composite ingots. The vacuum degree during welding must be less than 10 - 5mbar, the welding is first carried out by 6-point positioning, and then repeated sealing is performed to ensure the quality of the weld. The welded 54-core NbTi / Cu composite ingot is placed in a resistance furnace for uniform heating, and then extruded to obtain a NbTi / Cu composite rod. In the subsequent drawing process of the NbTi / Cu composite rod, multiple aging heat treatments are required. During the aging heat treatment process, the vacuum degree of the heat treatment furnace must be less than 0.1Pa, and the material temperature must be continuously monitored; it is also necessary to ensure that the lubrication is sufficient during the drawing process to prepare a Φ0.8mm 55-core NbTi / Cu composite wire. Low-oxygen C11000 copper rods that meet RRR>600 and O content<280ppm are selected, and the grain structure is optimized after the first annealing heat treatment (350℃×6h). After one rolling flattening, it is initially formed by a rectangular die of corresponding specifications, and a secondary annealing heat treatment (250℃×3h) is required after forming. A set of rectangular concave dies and semicircular convex dies are used for secondary rolling to form a Φ0.82mm semicircular groove. Finally, after passing through the forming mold, the copper slot wire has a smooth outer R angle with a consistent radius, and the copper slot wire preparation is completed. The copper slot wire prepared above needs to be ultrasonically cleaned to remove oil stains on the surface and in the slot. During the inlay process, the round wire needs to be slowly placed in the groove of the copper slot wire below at a speed of 45m / min. The mold passed through needs to be 200-300μm larger than the combination of the copper slot wire and the round wire, which mainly plays a restraining role to ensure that the slot wire and the round wire do not deform. Place the groove of the other copper slot wire face down on top of the combined wire, and immerse it in the tin liquid at the same time according to the requirements of the inlay welding process, with a welding temperature of 90°C and a speed of 100m / min. Pass through the forming mold and enter the cooling water. Achieve metallurgical bonding and complete the preparation of WIC superconducting wire with a large specification of (5.0×3.0) mm and a copper ratio of up to 65.0.

[0037] 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 implementation modes 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 WIC superconducting wire, characterized in that: include: The NbTi / Cu composite round wire is placed in a copper groove wire with a semicircular groove, and the initial bonding is completed through a constrained mold; then another copper groove wire with a semicircular groove is symmetrically arranged, and the final metallurgical bonding is completed by welding to produce a WIC superconducting wire.

2. The method for preparing a WIC superconducting wire according to claim 1, characterized in that: The copper trough wire with a semicircular groove is made of a low-oxygen C11000 copper rod, which is subjected to a primary annealing heat treatment, a primary rolling flattening, a preliminary forming by a rectangular mold of a corresponding specification, a secondary annealing heat treatment, and a secondary rolling by a set of rectangular concave molds and semicircular convex molds to finally form the copper trough wire with a semicircular groove.

3. The method for preparing a WIC superconducting wire according to claim 2, characterized in that: The low-oxygen C11000 copper rod meets RRR>600 and the O content is below 280 ppm, and the final forming speed is 80-120 m / min.

4. The method for preparing a WIC superconducting wire according to claim 1, characterized in that: The copper groove wire with two semicircular grooves symmetrically arranged on the NbTi / Cu composite round wire has a matching clearance of less than 0.1mm.

5. The method for preparing a WIC superconducting wire according to claim 4, characterized in that: The copper groove lines of the two semicircular grooves have outer R angles with the same radius.

6. The method for preparing a WIC superconducting wire according to any one of claims 1 to 5, characterized in that: In the preliminary combining step, the NbTi / Cu composite round wire is placed into a copper groove wire with a semicircular groove at a speed of 50-70 m / min.

7. The method for preparing a WIC superconducting wire according to claim 1, characterized in that: The welding is tin soldering. After the NbTi / Cu composite circular wire is symmetrically provided with two copper groove wires with semicircular grooves, the copper groove wires are simultaneously immersed in tin liquid, and the final metallurgical bonding is completed after passing through a forming mold and a cooling device.

8. A WIC superconducting wire, characterized in that: The WIC superconducting wire is prepared by the preparation method of the WIC superconducting wire according to any one of claims 1 to 7.

9. The WIC superconducting wire according to claim 8, characterized in that: The specification of the WIC superconducting wire is not less than 4 mm×2.4 mm.

10. The WIC superconducting wire according to claim 8, characterized in that: The copper ratio of the WIC superconducting wire is not less than 30.0.

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