Preparation method and application of high-uniformity fine Nb rod

Abstract

The invention discloses a preparation method and application of a high-uniformity fine Nb rod. The preparation method of the Nb rod comprises the steps of smelting, homogenization treatment, extrusion, annealing, rolling, stretching, straightening and polishing, finished product annealing and cleaning. The Nb rod prepared under a specific process condition has high uniformity, can be further processed into an extremely fine Nb wire on the basis, and can be applied to the fields of superconducting materials, high-strength and high-conductivity wires and aerospace due to the fact that Nb has good plasticity and superconducting characteristics, so that the Nb rod can be applied to the fields of the superconducting materials, the high-strength and high-conductivity wires and the aerospace field. And the prepared Nb rod (wire) has better fracture resistance.

Description

Technical Field

[0001] The invention relates to the technical field of superconducting material preparation, and in particular to a preparation method of a highly uniform fine Nb rod and application thereof. Background Art

[0002] Superconducting materials refer to materials that exhibit zero resistance and the property of repelling magnetic lines of force under certain low temperature conditions. They have the characteristics of zero resistance and anti-magnetism, and are widely used in the power industry, transportation, medical field, and scientific research equipment (high-energy physics). Metal niobium (chemical symbol Nb) is a transition metal element. Niobium has stable chemical properties and does not oxidize in the air. It is also difficult to dissolve, resistant to high temperatures, corrosion-resistant, and has high strength. Certain compounds and alloys of niobium have a high superconducting transition temperature, which makes them widely used in the field of superconducting materials. Niobium compounds and alloys, such as NbTi and Nb3Sn, are widely used to manufacture various industrial superconductors.

[0003] At present, almost all industrial superconducting devices use NbTi and Nb3Sn as superconductors. These superconducting devices play an important role in power transmission, medical diagnosis, scientific research equipment (high-energy physics) and other fields. For example, superconducting generators use the zero resistance characteristics of superconductors to greatly improve power generation efficiency; superconducting magnetic energy storage devices use the magnetic levitation characteristics of superconductors to achieve long-term storage and rapid release of electrical energy; large ion colliders can use superconducting magnets to generate strong magnetic fields to make particles in the device collide at high speed to study the nature of matter.

[0004] With the continuous development of superconducting technology, the application of metallic niobium in superconducting materials will become more extensive. The miniaturization of equipment can further reduce the wire diameter of superconducting materials. When manufacturing Nb wires, Nb often needs to be processed to 3-5μm without breakage. Even high-demand Nb materials need to be processed to 1-2μm, which requires the original Nb material to have high purity and grain uniformity. At present, in the processing of niobium wires, due to factors such as the preparation process, the purity of niobium materials can be purified to a higher purity through multiple electron beam melting. In order to avoid the impact of breakage during use, one of the most important indicator parameters is the grain size difference of the entire Nb material, which generally needs to be controlled within 1-2 levels, and there must be no fine grain bands. Only when the purity and grain size meet the requirements can qualified and high-performance superconducting wires be prepared. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention aims to provide a method for preparing a highly uniform fine Nb rod and its application. The prepared Nb rod has high uniformity, can be used in superconducting materials and high-strength and high-conducting wires, and has good anti-fracture performance.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing fine Nb rods with high uniformity comprises the following steps:

[0007] S1. Melting

[0008] Select a certain amount of Nb bars and perform vacuum electron beam melting 2-4 times to remove some impurities and prepare Nb ingots with the required composition and specifications of D120-200mm;

[0009] S2. Homogenization

[0010] The Nb ingot with the riser removed was cast at 10 -3 Pa vacuum, homogenization treatment at 1200-1300℃ for 2h;

[0011] S3, extrusion adjustment process

[0012] S31, extruding the homogenized rough Nb rod blank at a certain extrusion ratio under high temperature;

[0013] S32, performing surface treatment on the extruded Nb rod, and then annealing under vacuum and cooling the rod with the furnace before taking it out of the furnace;

[0014] S4, rolling

[0015] Roll the Nb rods after they are fired, with a deformation rate of 15-20% each time, rolling them close to the finished product size and leaving a 1-2mm margin;

[0016] S5. Stretch

[0017] The rolled Nb rod is stretched in a round shape, with a stretching deformation rate of 10-15% each time, and a grinding allowance of 0.1-0.5 mm is reserved;

[0018] S6, straightening and polishing

[0019] The stretched Nb rod is surface straightened and polished;

[0020] S7, finished product annealing

[0021] The polished Nb rod is heated to not less than 10 -3 Recrystallization annealing under Pa vacuum conditions, adjusting the annealing process, to obtain fine Nb rods that meet the requirements of organization and performance;

[0022] S8. Cleaning

[0023] The surface of the fine Nb rods after being taken out of the furnace is cleaned by strong acid and strong alkali to form high uniformity fine Nb rod products.

[0024] Preferably, in step S1, the smelting is repeated 2-3 times;

[0025] In step S2, the homogenization treatment conditions are as follows: the Nb ingot is heated to 1200-1300°C at 5-10°C / min, kept at this temperature for 2 hours, and then cooled to 60°C before being taken out of the furnace.

[0026] Preferably, the extrusion in step S31 includes primary extrusion and secondary extrusion, and the primary extrusion conditions are: extrusion ratio 4-9, extrusion temperature 750-950°C;

[0027] The secondary extrusion conditions are: extrusion ratio 8-10, extrusion temperature 700-900°C.

[0028] Preferably, in step S32, the annealing includes a primary annealing and a secondary annealing, and the primary annealing condition is: 10 -3 Annealing under Pa vacuum, 580-720℃, 1-2h detrending annealing; then heating to 800-1100℃ and keeping for 3h, then cooling to 60℃ and taking out of the furnace;

[0029] The secondary annealing conditions are: 10 -3 Annealing under Pa vacuum, 500-680℃, 1-2h to remove the trend energy; then heat to 750-1000℃ and keep warm for 3h, then cool to 60℃ and take out of the furnace.

[0030] Preferably, the order of extrusion and annealing is: one extrusion, one annealing, two extrusions and two annealings.

[0031] Preferably, the finished product annealing conditions in step S7 are: 500-680°C, 1-2h detrending annealing, then heating to 750-900°C and keeping for 3h, then cooling to 60°C and taking out of the furnace.

[0032] The present application also provides an application of a prepared high-uniformity fine Nb rod in superconducting materials and high-strength and high-conducting wires.

[0033] The beneficial effects of the present invention are as follows: the Nb rod prepared by the present invention has high uniformity, and on this basis, can be further processed into Nb wires with extremely fine specifications. Since Nb has good superconducting properties, it can be applied to superconducting materials and high-strength and high-conducting wires, and has good anti-fracture performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram of a pure Nb ingot obtained by smelting according to the present invention.

[0035] Figure 2 This is a diagram of a pure niobium rod after one extrusion according to the present invention.

[0036] Figure 3 This is a diagram of the primary recrystallization annealing metallographic structure of the present invention.

[0037] Figure 4 This is a diagram of the secondary annealing metallographic structure of the present invention.

[0038] Figure 5 This is a diagram of the finished product of the fine Nb rod prepared by the present invention.

[0039] Figure 6 This is a diagram showing the metallographic structure of the secondary annealing of the currently conventionally prepared fine Nb rods. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0041] See attached Figures 1 to 5 A method for preparing a highly uniform fine Nb rod is shown, comprising the following steps:

[0042] S1. Melting

[0043] The raw material Nb bar is subjected to vacuum electron beam melting 2-4 times to remove some impurities (such as C, H, ON, etc.) to prepare Nb billet ingots with composition meeting the requirements (such as C<0.01wt%, H<0.0015wt%, O<0.015wt%, N<0.01wt%) and specifications of D120-200mm (such as attached Figure 1 The ingot of this specification can reduce the grain size difference within the cross section of the Nb ingot.

[0044] S2. Homogenization

[0045] The Nb billet with the riser removed was -3 The homogenization treatment is carried out at 1200-1300℃ for 2h under vacuum of 1200-1300℃. The specific treatment process is: the rough Nb rod blank is heated to 1200-1300℃ with the furnace at 5-10℃ / min, kept at this temperature for 2h, and then cooled to 60℃ and taken out of the furnace. During the treatment process, too high or too low heating rate is not conducive to the homogenization effect of the Nb rod, and the grain size difference of the material cross section cannot be well adjusted.

[0046] S3, extrusion (hardness, grain size) adjustment process

[0047] S31, extruding the homogenized rough Nb rod blank at a certain extrusion ratio and at a high temperature. The extrusion includes primary extrusion and secondary extrusion. The primary extrusion conditions are: extrusion ratio 4-9, extrusion temperature 750-950℃, and sequentially extruding pure niobium rods such as Figure 2 As shown; the secondary extrusion conditions are: extrusion ratio 8-10, extrusion temperature 700-900℃.

[0048] S32, the extruded Nb rod is sized and peeled according to the extrusion requirements, and then annealed under vacuum, and then taken out of the furnace after cooling, so that its hardness meets the extrusion or subsequent processing requirements, and effective recrystallization annealing can reduce the grain size difference. The annealing includes primary annealing and secondary annealing, and the primary annealing conditions are: 10 -3 Annealing under Pa vacuum, 580-720℃, 1-2h detrending annealing; then heating to 800-1100℃ and keeping for 3h, then cooling to 60℃ and taking out of the furnace;

[0049] The secondary annealing conditions are: 10 -3 Annealing under Pa vacuum, 500-680℃, 1-2h to remove the trend energy; then heat to 750-1000℃ and keep warm for 3h, then cool to 60℃ and take out of the furnace.

[0050] The above extrusion and annealing treatment can be repeated 2-3 times according to product requirements. The order of extrusion and annealing is: one extrusion, one annealing, two extrusions and two annealings. If necessary, three extrusions and annealing treatments should be performed. Repeated pressure annealing treatments can effectively adjust the grain size difference.

[0051] S4, rolling

[0052] The extruded and annealed Nb rod is rolled on a groove rolling mill with a pass processing rate of 15-20% and rolled to a size close to the finished product, with a 1-2mm margin.

[0053] S5. Stretch

[0054] The rolled Nb rod is subjected to full round stretching processing, with a pass processing rate of 10-15%, and a grinding processing allowance of 0.1-0.5 mm is reserved.

[0055] S6, straightening and polishing

[0056] The stretched Nb rod needs to be ground on a special precision grinder to remove surface processing defects and surface impurities, improve surface quality, and straighten according to product use requirements. Generally, the straightening requirement is 0.5mm / 1000mm.

[0057] S7, finished product annealing

[0058] The polished Nb rod with qualified surface is subjected to recrystallization annealing (preferably twice in this application) under vacuum conditions better than 10-3Pa, and the annealing process is adjusted to obtain a fine Nb rod with structure and performance that meet the requirements. The finished product annealing conditions are as follows: annealing temperature 500-680℃, 1-2h detrending annealing, then heating to 750-900℃ and keeping for 3h, and then cooling to 60℃ and taking out of the furnace. The metallographic structure of the first annealing recrystallization annealing is as follows Figure 3 As shown, the microstructure of the first annealing and recrystallization annealing is as follows Figure 4 shown.

[0059] S8. Cleaning

[0060] The fine Nb rods after being fired are cleaned by strong acid and alkali to form high uniform fine Nb rods. Figure 5 As shown, the specification is D5-15mm.

[0061] The highly uniform fine Nb rods prepared as above have high purity and uniformity, and can be used in superconducting materials and high-strength and high-conducting wires. After being processed into extremely fine superconducting wires, the problem of wire breakage can be effectively avoided.

[0062] According to the above method for preparing fine Nb rods with high uniformity, the present application provides the following embodiments:

[0063] Example 1

[0064] S1. Material selection

[0065] A rough Nb rod blank with a diameter of 120 mm was selected after electron beam melting, and its riser was cut off.

[0066] S2. Homogenization

[0067] The rough Nb rod blank with the riser cut off was homogenized under vacuum. The treatment conditions were: the rough Nb rod blank was heated to 1200°C at 10°C / min in the furnace, kept at this temperature for 2h, and then cooled to 60°C in the furnace before being taken out of the furnace.

[0068] S3, extrusion and annealing

[0069] Primary extrusion: the homogenized rough Nb rod blank is extruded at an extrusion ratio of 4 and an extrusion temperature of 650°C;

[0070] Primary annealing: anneal the extruded Nb rod under vacuum at 620°C for 1 hour to remove the trend energy; then heat to 1100°C and keep for 2.5 hours, then cool to 60°C and take out of the furnace;

[0071] Secondary extrusion: The Nb rod after primary annealing is extruded at an extrusion ratio of 8 and an extrusion temperature of 620°C.

[0072] Secondary annealing: anneal the Nb rod after secondary extrusion under vacuum at 600°C for 1 hour to remove the trend energy; then heat to 1000°C and keep for 2 hours, then cool to 60°C and take out of the furnace.

[0073] S4, rolling

[0074] The extruded and annealed Nb rods are rolled on a grooved rolling mill with a pass processing rate of 16% and rolled to a size close to the finished product, with a 1.5mm margin.

[0075] S5. Stretch

[0076] The rolled Nb rod is subjected to full round stretching processing, with a pass processing rate of 10% and a 0.2mm grinding processing allowance reserved.

[0077] S6, straightening and polishing

[0078] The stretched Nb rod needs to be ground on a special precision grinder to remove surface processing defects and surface impurities, improve surface quality, and straighten according to product use requirements. The straightening requirement is 0.5mm / 1000mm.

[0079] S7, finished product annealing

[0080] The straightened and polished fine Nb rods were annealed in vacuum at 600°C for 1 hour to remove the trend, then heated to 950°C for 3 hours, and then cooled to 60°C before being taken out of the furnace.

[0081] S8. Cleaning

[0082] The fine Nb rods taken out of the furnace are cleaned on the surface by strong acid and strong alkali to obtain high uniformity fine Nb rods.

[0083] Example 2

[0084] S1. Material selection

[0085] A rough Nb rod blank with a D of 160 mm was selected after electron beam melting, and its riser was cut off.

[0086] S2. Homogenization

[0087] The rough Nb rod blank with the riser cut off was homogenized under vacuum. The treatment conditions were: the rough Nb rod blank was heated to 1250°C at 10°C / min in the furnace, kept at this temperature for 2h, and then cooled to 60°C in the furnace before being taken out of the furnace.

[0088] S3, extrusion and annealing

[0089] Primary extrusion: the homogenized rough Nb rod blank is extruded at an extrusion ratio of 7 and an extrusion temperature of 680°C;

[0090] Primary annealing: anneal the Nb rod after primary extrusion under vacuum at 640°C for 1.5 hours to remove the trend energy; then heat to 1150°C and keep for 3 hours, then cool to 60°C and take out of the furnace;

[0091] Secondary extrusion: The Nb rod after primary annealing is extruded at an extrusion ratio of 9 and an extrusion temperature of 650°C.

[0092] Secondary annealing: anneal the Nb rod after secondary extrusion under vacuum at 600°C for 1.5 hours to remove the trend energy; then heat to 950°C and keep for 3 hours, then cool to 60°C and take out of the furnace.

[0093] S4, rolling

[0094] The extruded and annealed Nb rods are rolled on a grooved rolling mill with a pass processing rate of 18% and rolled to a size close to the finished product, with a 2mm margin.

[0095] S5. Stretch

[0096] The rolled Nb rod is fully stretched in a round shape, with a pass processing rate of 13% and a grinding allowance of 0.3 mm.

[0097] S6, straightening and polishing

[0098] The stretched Nb rod needs to be ground on a special precision grinder to remove surface processing defects and surface impurities, improve surface quality, and straighten according to product use requirements. The straightening requirement is 0.5mm / 1000mm.

[0099] S7, finished product annealing

[0100] The straightened and polished fine Nb rods were annealed under vacuum. The annealing conditions were: 600°C, kept for 1.5 hours to remove the trend, then heated to 950°C and kept for 3 hours, and then cooled to 60°C and taken out of the furnace.

[0101] S8. Cleaning

[0102] The fine Nb rods taken out of the furnace are cleaned on the surface by strong acid and strong alkali to obtain high uniformity fine Nb rods.

[0103] Example 3

[0104] S1. Material selection

[0105] A rough Nb rod blank having a diameter of D200 mm was selected by electron beam melting, and its riser was cut off.

[0106] S2. Homogenization

[0107] The rough Nb rod blank with the riser cut off was homogenized under vacuum. The treatment conditions were: the rough Nb rod blank was heated to 1300°C at 10°C / min in the furnace, kept at that temperature for 2h, and then cooled to 60°C in the furnace before being taken out of the furnace.

[0108] S3, extrusion and annealing

[0109] Primary extrusion: the homogenized rough Nb rod is extruded at an extrusion ratio of 9 and an extrusion temperature of 720°C;

[0110] Primary annealing: anneal the Nb rod after primary extrusion under vacuum at 750°C for 2 hours to remove the trend energy; then heat to 1200°C and keep for 3 hours, then cool to 60°C and take out of the furnace;

[0111] Secondary extrusion: The Nb rod after primary annealing is extruded at an extrusion ratio of 10 and an extrusion temperature of 700°C.

[0112] Secondary annealing: anneal the Nb rod after secondary extrusion under vacuum at 680°C for 2 hours to remove the trend energy; then heat to 1000°C and keep for 3 hours, then cool to 60°C and take out of the furnace.

[0113] S4, rolling

[0114] The extruded and annealed Nb rods are rolled on a grooved rolling mill with a pass processing rate of 20% and rolled to a size close to the finished product, with a 1.5mm margin reserved.

[0115] S5. Stretch

[0116] The rolled Nb rod is subjected to full round stretching processing, with a pass processing rate of 15% and a 0.4mm grinding processing allowance reserved.

[0117] S6, straightening and polishing

[0118] The stretched Nb rod needs to be ground on a special precision grinder to remove surface processing defects and surface impurities, improve surface quality, and straighten according to product use requirements. The straightening requirement is 0.5mm / 1000mm.

[0119] S7, finished product annealing

[0120] The straightened and polished fine Nb rods were annealed under vacuum at 680°C for 2 hours to remove the trend, then heated to 950°C for 3 hours, and then cooled to 60°C before being taken out of the furnace.

[0121] S8. Cleaning

[0122] The fine Nb rods taken out of the furnace are cleaned on the surface by strong acid and strong alkali to obtain high uniformity fine Nb rods.

[0123] According to the above embodiments, the Figure 5 The high uniformity fine Nb rod shown can be further processed and applied in not limited to superconducting materials and high-strength and high-wire materials due to its high uniformity.

[0124] The above shows and describes the basic principle, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention claimed.

Claims

1. A method for preparing fine Nb rods with high uniformity, characterized in that: The following steps are involved: S1. Melting Select a certain amount of Nb bars and perform vacuum electron beam melting 2-4 times to remove some impurities and prepare Nb ingots with the required composition and specifications of D120-200mm; S2. Homogenization The Nb ingot with the riser removed was cast at 10 -3 Pa vacuum, homogenization treatment at 1200-1300℃ for 2h; S3, extrusion adjustment process S31, extruding the homogenized rough Nb rod blank at a certain extrusion ratio under high temperature; S32, performing surface treatment on the extruded Nb rod, and then annealing under vacuum and cooling the rod with the furnace before taking it out of the furnace; S4, rolling Roll the Nb rods after they are fired, with a deformation rate of 15-20% each time, rolling them close to the finished product size and leaving a 1-2mm margin; S5. Stretch The rolled Nb rod is stretched in a round shape, with a stretching deformation rate of 10-15% each time, and a grinding allowance of 0.1-0.5 mm is reserved; S6, straightening and polishing The stretched Nb rod is surface straightened and polished; S7, finished product annealing The polished Nb rod is heated to not less than 10 -3 Recrystallization annealing under Pa vacuum conditions, adjusting the annealing process, to obtain fine Nb rods that meet the requirements of organization and performance; S8. Cleaning The surface of the fine Nb rods after being taken out of the furnace is cleaned by strong acid and strong alkali to form high uniformity fine Nb rod products.

2. The method for preparing fine Nb rods with high uniformity according to claim 1, characterized in that: In step S1, the smelting is repeated 2-3 times; In step S2, the homogenization treatment conditions are as follows: the Nb ingot is heated to 1200-1300°C at 5-10°C / min, kept at this temperature for 2 hours, and then cooled to 60°C before being taken out of the furnace.

3. The method for preparing fine Nb rods with high uniformity according to claim 2, characterized in that: The extrusion in step S31 includes primary extrusion and secondary extrusion, and the primary extrusion conditions are: extrusion ratio 4-9, extrusion temperature 750-950°C; The secondary extrusion conditions are: extrusion ratio 8-10, extrusion temperature 700-900°C.

4. The method for preparing fine Nb rods with high uniformity according to claim 3, characterized in that: In step S32, the annealing includes a primary annealing and a secondary annealing, and the primary annealing conditions are: 10 -3 Annealing under Pa vacuum, 580-720℃, 1-2h detrending annealing; then heating to 800-1100℃ and keeping for 3h, then cooling to 60℃ and taking out of the furnace; The secondary annealing conditions are: 10 -3 Annealing under Pa vacuum, 500-680℃, 1-2h to remove the trend energy; then heat to 750-1000℃ and keep warm for 3h, then cool to 60℃ and take out of the furnace.

5. The method for preparing fine Nb rods with high uniformity according to claim 4, characterized in that: The order of extrusion and annealing is: primary extrusion, primary annealing, secondary extrusion and secondary annealing.

6. The method for preparing highly uniform fine Nb rods according to claim 5, characterized in that: The finished product annealing conditions in step S7 are: 500-680°C, 1-2h detrending annealing, then heating to 750-900°C and keeping for 3h, then cooling to 60°C and taking out of the furnace.

7. Use of the highly uniform fine Nb rods prepared as claimed in claims 1 to 6 in superconducting materials and high-strength and high-conducting wires.

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