METHOD FOR PRODUCING A SUPERCONDUCTING COMPOSITE ROD, A SUPERCONDUCTING COMPOSITE ROD AND A SUPERCONDUCTING WIRE

Abstract

The present application discloses a method for preparing a superconducting composite rod, a superconducting composite rod, and a superconducting wire. The preparation method comprises: bundling a plurality of single-core rods and then placing same into a copper pipe, to form a composite ingot; heating the composite ingot; on the basis of a required diameter, selecting an extrusion container; and performing backward extrusion on the heated composite ingot by using the extrusion container, to obtain a superconducting composite rod. According to the present application, by performing backward extrusion after heating the composite ingot, problems such as severe tail shrinkage, poor filament deformation, and low yield of composite rods obtained by performing conventional forward extrusion are solved.

Description

A method for preparing a superconducting composite rod, a superconducting composite rod and a superconducting wire Technical Field

[0001] The present application relates to the field of metal processing technology, and in particular to a method for preparing a superconducting composite rod, a superconducting composite rod, and a superconducting wire. Background Art

[0002] As people's living standards continue to improve, demand for high-end medical technologies, equipment, and devices has surged, including high-end medical imaging equipment such as magnetic resonance imaging (MRI). In recent years, driven by the global healthcare landscape, demand for MRI equipment has skyrocketed, and contracts with renowned MRI manufacturers both domestically and internationally have increased significantly. Key raw materials used in MRI equipment, such as niobium titanium (NbTi), have a significant impact on the overall cost of the equipment. Consequently, upstream and downstream companies involved in the entire MRI equipment manufacturing process have embraced lean production, optimizing processes from raw materials and processing to testing and transportation to reduce production costs. Niobium titanium / copper (NbTi / Cu) superconducting wires made from NbTi are functional materials that require a complex production process, long cycles, numerous steps, and extremely high quality standards.

[0003] At present, the hot extrusion of NbTi / Cu superconducting wires in large-scale production usually adopts forward extrusion, that is, the movement direction of the metal is the same as the movement direction of the extrusion barrel. Due to the relative movement between the material and the extrusion barrel, the extrusion yield is low and the core wire deformation is uneven. As a result, when the composite wire is stretched to the finished product specifications, a large part of the unevenly deformed core wire is removed, resulting in a significant decrease in the yield and a significant increase in production costs. Therefore, there is an urgent need to develop a hot extrusion processing method with high extrusion yield and high core wire deformation uniformity. Summary of the Invention

[0004] The embodiments of the present application provide a method for preparing a superconducting composite rod, a superconducting composite rod, and a superconducting wire, so as to solve the problem of low extrusion yield caused by normal extrusion in the prior art.

[0005] In one aspect, an embodiment of the present application provides a method for preparing a superconducting composite rod, comprising:

[0006] Multiple single core rods are bundled and loaded into a copper tube to form a composite ingot;

[0007] heating the composite ingot;

[0008] Select the extrusion cylinder according to the required diameter;

[0009] The heated composite ingot is reversely extruded by an extrusion cylinder to obtain a superconducting composite rod.

[0010] On the other hand, an embodiment of the present application further provides a superconducting composite rod, which is prepared using the above method.

[0011] On the other hand, an embodiment of the present application further provides a superconducting wire, which is prepared using a superconducting composite rod.

[0012] The superconducting composite rod preparation method, superconducting composite rod and superconducting wire in this application have the following advantages:

[0013] The composite ingot is assembled using a conical upper cover and special-shaped inserted rods. The composite ingot is first preheated at low temperature in a resistance furnace, then induction heated at high temperature by a gradient coil, and finally prepared into a superconducting composite rod by reverse extrusion and water quenching. The appropriate preheating temperature, extrusion temperature and extrusion barrel are selected according to the outer diameter of the composite ingot and the copper ratio, which effectively solves several problems of conventional forward extrusion composite rods, such as severe tail shrinkage, poor core wire deformation, and low yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0015] FIG1 is a schematic structural diagram of a copper tube and a copper cover provided in an embodiment of the present application;

[0016] FIG2 is a schematic structural diagram of a composite rod provided in an embodiment of the present application.

[0017] Description of the accompanying drawings: 1-copper tube, 2-upper cover, 3-lower cover, 4-trapezoidal plug, 5-triangular plug, 6-single core rod. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0019] The present invention provides a method for preparing a superconducting composite rod, comprising:

[0020] S100 , multiple single core rods 6 are bundled and loaded into the copper tube 1 to form a composite ingot.

[0021] For example, the single core rod 6 may be a NbTi / Cu single core rod or other single core rod used to prepare superconducting wires. Before the single core rod 6 is installed in the copper tube 1 , the single core rod 6 and the copper tube 1 need to be cleaned, preferably using nitric acid.

[0022] The cross-section of the single core rod 6 is a regular hexagon, while the cross-section of the copper tube 1 is circular. After multiple single core rods 6 are loaded into the copper tube 1, copper inserts are inserted into the gaps between the single core rods 6 and the copper tube 1. The copper inserts include trapezoidal inserts 4 and triangular inserts 5. The choice of trapezoidal inserts 4 or triangular inserts 5 can be flexibly selected based on the size of the gap between the single core rod 6 and the copper tube 1.

[0023] Furthermore, after multiple single core rods 6 are loaded into the copper tube 1, copper caps are placed at both ends of the copper tube 1 and welded to the copper tube 1 to form a composite ingot. Specifically, the copper caps can be welded to the copper tube 1 using electron beam sealing welding technology.

[0024] As shown in Figure 1, the copper cover in this application includes an upper cover 2 and a lower cover 3. The upper cover adopts a conical structure, and the lower cover can adopt a disc-shaped structure. The cone angle of the upper cover 2 is 120°. To ensure that the upper cover 2, the lower cover 3 and the copper tube 1 are tightly assembled, the end face of the copper tube 1 needs to be chamfered. After the copper rod made of oxygen-free copper is inserted into the copper tube 1, the filling rate of the composite ingot is required to be greater than 95%. Finally, a vacuum electron beam welder is used to seal the assembled sheath.

[0025] S110, heating the composite ingot.

[0026] For example, the composite ingot is preheated before being heated. Specifically, a resistance furnace can be used for preheating, with the preheating temperature controlled between 200°C and 300°C, a heating rate not exceeding 100°C / hour, and a preheating time of 1 to 2 hours. During preheating, a layer of stainless steel plate should be placed on the bottom of the resistance furnace to prevent foreign matter from being trapped on the surface of the composite ingot.

[0027] After the composite ingot is preheated, it can be heated sequentially using multiple induction coils, with the temperatures of the multiple induction coils increasing sequentially. In the embodiment of the present application, the number of induction coils is six, and the temperature difference between two adjacent induction coils is 40-80°C. The composite ingot is heated in each induction coil for 10-40 minutes. During the heating process, infrared sensing can be used to monitor the actual temperature of the composite ingot.

[0028] S120, select the extrusion cylinder and extrusion die according to the required diameter.

[0029] For example, the extrusion barrel can be selected based on the final required diameter of the superconducting composite rod. The gap between the inner diameter of the extrusion barrel and the outer diameter of the heated composite ingot is controlled to be 5mm-10mm, and the extrusion die is concave with a taper angle of 120°.

[0030] S130, reversely extruding the heated composite ingot using an extrusion cylinder to obtain a superconducting composite rod.

[0031] For example, before reverse extrusion of the composite ingot using the extrusion barrel, the barrel and die are preheated to a temperature between 200°C and 300°C, and lubricant is applied to both. Furthermore, the inner wall of the barrel and the die surface are carefully cleaned before extrusion to prevent foreign matter from being trapped.

[0032] After the extrusion starts, the reverse extrusion speed is controlled at 10mm / s~20mm / s. The extruded rod needs to be water quenched immediately after leaving the mold. The quenching time is controlled at 1min~3min, and the temperature of the quenching cooling water is controlled at 20℃~30℃.

[0033] The embodiment of the present application further provides a superconducting composite rod, which is prepared using the above method.

[0034] An embodiment of the present application further provides a superconducting wire, which is prepared using the above-mentioned superconducting composite rod.

[0035] For example, the superconducting composite rod may be drawn in multiple passes to form a superconducting wire. Example 1

[0036] First, 55 cleaned hexagonal NbTi / Cu single-core rods (H15mm, 560mm long) were neatly and closely packed inside an oxygen-free copper tube (OD) with an outer diameter of Φ152mm, an inner diameter of Φ133mm, and a length of 600mm. Six trapezoidal inserts and 12 triangular inserts were then placed between the OD tube and the single-core rods. Finally, a 55mm-thick upper cover and a 30mm-thick lower cover were inserted into both ends of the OD tube. The assembled composite ingot was then vacuum welded in an electron beam welder. The welded NbTi / Cu composite ingot was preheated in a resistance furnace at a temperature of 200°C, a heating rate of 90°C / h, and a preheating hold time of 1h. Before loading, a layer of stainless steel was laid on the furnace floor to prevent foreign matter from being trapped on the surface of the composite ingot. The preheated composite ingot is transferred to the induction coil for high-temperature heating. The heating temperature of each induction coil is 270℃, 340℃, 410℃, 480℃, 550℃, and 620℃, and the heating time of each induction coil is 20min, 20min, 20min, 30min, 30min, and 30min, respectively. While the composite ingot is induction heated, the Φ155mm extrusion barrel and the Φ40mm conical die are preheated at a temperature of 200°C. When the last induction coil heating is about to be completed, lubricant is applied to the extrusion barrel and the die. After the preparation is ready, the heated composite ingot is transferred to the inside of the extrusion barrel for reverse extrusion. The extrusion speed is controlled at 10mm / s~20mm / s. After the Φ40mm extruded rod is ejected from the die, it is immediately transferred to a water tank for quenching until the extruded rod cools to room temperature. The outer diameter is measured after it is taken out, and finally the head and tail of the Φ40mm extruded rod are sawed until 55 layers of core wire appear, obtaining a NbTi / Cu superconducting composite rod with uniform core wire deformation. Compared with the forward extrusion, the extrusion yield of the Φ152mm ingot-shaped composite ingot is increased by about 3%, which is a significant effect. Example 2

[0037] First, 55 cleaned hexagonal NbTi / Cu single-core rods (H25mm, 700mm long) were neatly and closely packed inside an oxygen-free copper tube (OD) with an outer diameter of Φ230mm, an inner diameter of Φ195mm, and a length of 720mm. Six trapezoidal inserts and 12 triangular inserts were then placed between the OD copper tube and the single-core rods. Finally, a 55mm-thick upper cover and a 30mm-thick lower cover were inserted into both ends of the OD copper tube. The assembled composite ingot was vacuum welded in an electron beam welder. The welded NbTi / Cu composite ingot was preheated in a resistance furnace at a temperature of 250°C, a heating rate of 80°C / h, and a preheating hold time of 2h. Before loading, a layer of stainless steel was laid on the furnace floor to prevent foreign matter from being trapped on the composite ingot surface. The preheated composite ingot is transferred to the induction coil for high-temperature heating. The heating temperature of each induction coil is 320°C, 390°C, 460°C, 530°C, 600°C, and 670°C, and the heating time of each induction coil is 20min, 20min, 20min, 30min, 30min, and 30min, respectively. While the composite ingot is induction heated, the Φ235mm extrusion barrel and the Φ80mm conical die are preheated at 200°C. When the last induction coil heating is about to be completed, lubricant is applied to the extrusion barrel and the die. After the preparation is ready, the heated composite ingot is transferred to the inside of the extrusion barrel for reverse extrusion. The extrusion speed is controlled at 10mm / s~20mm / s. After the Φ80mm extruded rod is ejected from the die, it is immediately transferred to the water tank for quenching until the extruded rod cools to room temperature. After being taken out, the outer diameter is measured. Finally, the head and tail of the Φ80mm extruded rod are sawed until 55 layers of core wire appear, obtaining a NbTi / Cu superconducting composite rod with uniform core wire deformation. Compared with the forward extrusion, the extrusion yield of the Φ230mm ingot-shaped composite ingot is improved by about 4.5%, which is a significant effect. Example 3

[0038] First, 55 cleaned hexagonal NbTi / Cu single-core rods (H35mm, 800mm long) were neatly and closely packed inside an oxygen-free copper tube (OD305mm, ID261mm, 820mm long). Six trapezoidal inserts and 12 triangular inserts were then placed between the OD tube and the single-core rods. Finally, a 75mm-thick upper cover and a 40mm-thick lower cover were inserted into both ends of the OD tube. The assembled composite ingot was then vacuum welded in an electron beam welder. The welded NbTi / Cu composite ingot was preheated in a resistance furnace at a temperature of 300°C, a heating rate of 70°C / h, and a preheating hold time of 2h. Before loading, a layer of stainless steel was laid on the furnace floor to prevent foreign matter from being trapped on the surface of the composite ingot. The preheated composite ingot is transferred to the induction coil for high-temperature heating. The heating temperature of each coil is 300℃, 380℃, 460℃, 540℃, 620℃, and 700℃, and the heating time of each induction coil is 15min, 15min, 20min, 30min, 40min, and 40min, respectively. While the composite ingot is induction heated, the Φ310mm extrusion barrel and the Φ90mm conical die are preheated at 200°C. When the last induction coil heating is about to be completed, lubricant is applied to the extrusion barrel and the die. After the preparation is ready, the heated composite ingot is transferred to the inside of the extrusion barrel for reverse extrusion. The extrusion speed is controlled at 10mm / s~20mm / s. After the Φ90mm extruded rod is ejected from the die, it is immediately transferred to the water tank for quenching until the extruded rod cools to room temperature. After being taken out, the outer diameter is measured. Finally, the head and tail of the Φ90mm extruded rod are sawed until 55 layers of core wire appear, obtaining a NbTi / Cu superconducting composite rod with uniform core wire deformation. Compared with the forward extrusion, the extrusion yield of the Φ305mm ingot-shaped composite ingot is increased by about 6%, which is a significant effect.

[0039] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0040] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for producing a superconducting composite rod, characterized in that it includes the following steps: a plurality of rods (6) with one core are combined and placed in a copper tube (1) to obtain a composite blank; the said composite blank is heated; Depending on the required diameter, an extrusion cylinder is selected; by means of said extrusion cylinder, said composite blank is subjected to reverse extrusion after heating to obtain a superconducting composite rod.

2. A method for producing a superconducting composite rod according to claim 1, characterized in that after placing a plurality of rods (6) with one core in a copper tube (1), copper caps are additionally installed at both ends of the copper tube (1) and the copper caps are welded to the copper tube (1) to obtain a composite blank.

3. A method for producing a superconducting composite rod according to paragraph 2, characterized in that the copper caps are welded to the copper tube (1) using electron beam sealing welding technology.

4. A method for producing a superconducting composite rod according to claim 1, characterized in that the rod (6) with one core in cross-section has the shape of a regular hexagon, and the copper tube (1) in cross-section is round, and after placing a plurality of rods (6) with one core in the copper tube (1), copper insert rods are also inserted into the spaces between the rods (6) with one core and the copper tube (1).

5. A method for producing a superconducting composite rod according to claim 4, characterized in that the copper insert rods comprise trapezoidal insert rods (4) and triangular insert rods (5).

6. A method for producing a superconducting composite rod according to claim 1, characterized in that before heating the composite blank, the composite blank is also preheated.

7. A method for producing a superconducting composite rod according to claim 1, characterized in that the composite blank is heated sequentially by means of several induction coils, wherein the temperature of several induction coils is increased sequentially.

8. A method for producing a superconducting composite rod according to claim 1, characterized in that the extrusion cylinder is also preheated before reverse extrusion of the composite blank by means of the extrusion cylinder and a lubricant is applied to the extrusion cylinder.

9. A superconducting composite rod, characterized in that the superconducting composite rod is obtained by the method according to any of paragraphs 1-8.

10. A superconducting wire, characterized in that the superconducting wire is obtained using a superconducting composite rod according to paragraph 9.