CN104091651A - Method for manufacturing multi-core MgB2 superconductive wires through extrusion technology - Google Patents
Method for manufacturing multi-core MgB2 superconductive wires through extrusion technology Download PDFInfo
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Abstract
The invention discloses a method for manufacturing multi-core MgB2 superconductive wires through the extrusion technology. The method includes the steps that first, precursor powder is prepared; second, the precursor powder is installed in a pipe to prepare a primary complex, and single-core wires are obtained through drawing machining; third, the precursor powder is installed in a pipe to prepare a secondary complex; fourth, the secondary complex processed through pre-heating seal welding is extruded, and multi-core rods are obtained; fifth, the multi-core rods are stripped and drawn to obtain multi-core wires, the multi-core wires are subjected to heat treatment, and then the multi-core MgB2 superconductive wires are obtained. According to the method, on the basis of a traditional power pipe-installing technology, a large single-pass machining deformation amount is adopted for manufacturing the multi-core MgB2 superconductive wires, in other words, the extrusion technology is adopted for manufacturing the multi-core MgB2 superconductive wires, because the secondary complex is in a very favorable three-dimensional stress state in extrusion, good metallurgical bonding will be achieved between different metal interfaces in the secondary complex along with the large extrusion deformation amount, the manufactured multi-core rods are high in composite strength, and the compactness and the yield strength of the multi-core MgB2 superconductive wires can be significantly improved.
Description
Technical field
The invention belongs to superconducting line strips processing technique field, specifically relate to a kind of extrusion process and prepare multicore MgB
2the method of superconducting wire.
Background technology
The superconductivity of magnesium diboride material found by Japanese scientist at first, and this material is a kind of nonmetallic compound with simple binary structure, the superconduction critical transition temperature (T under null field
c) be about 39K, be the simple binary compound at present with the highest superconduction critical transition temperature, at the beginning of finding, its superconductivity just caused the research field internal medicine scholars' such as all parts of the world Theoretical Physics and practical application very big enthusiasm.For MgB
2the wire strip research field of superconductor forceful electric power application, its technical research of becoming a useful person has obtained significant progress, and the researcher of countries in the world successively attempts adopting multiple manufacturing process preparation to have the MgB of certain length
2superconducting line strips, such as adopting powder tubulature technique (PIT), continuous powder tubulature moulding process (CTFF) and center Mg diffusion technology (IMD) etc.
For MgB
2the most frequently used manufacturing process of the long wire strip of multicore is to adopt in-situ method powder sleeve technology (in-situ PIT).In its course of processing first by Mg powder, B powder and doping powder according to 1:(2-x): the stoichiometric proportion mixing of x, tubulature are also prepared into round line or bandlet through drawing, the rolling equal pressure course of processing, and obtain MgB through suitable Technology for Heating Processing
2superconducting wire.In this traditional in-situ PIT technical process, owing to being subject to Mg-B architecture to study the impact of phase reaction intrinsic property, at the final MgB forming
2in superconducting phase, there is more cellular hole.The existence of these holes has reduced MgB
2the connectivity of intergranule, has reduced the effective-current area of supercurrent, thereby has suppressed MgB
2the supercurrent transmission performance of composite wire, becomes restriction MgB
2one of " bottleneck " of the practical development of superconductor.
Summary of the invention
Technical problem to be solved by this invention is, for above-mentioned deficiency of the prior art, to provide a kind of extrusion process to prepare multicore MgB
2the method of superconducting wire.It is that extrusion-processing technology is prepared multicore MgB that the method adopts larger single pass machining deformation amount on the basis of traditional powder tubulature technique
2superconducting wire, during due to extruding, secondary complex, in very favorable three-dimensional stress state, is followed larger extrusion deformation degree, and in secondary complex, good metallurgical binding can be realized in different metal interface, the combined strength bination of the multicore bar of preparation is higher, can significantly improve multicore MgB
2the density of superconducting wire and yield strength are practical km magnitude MgB
2the mass production of superconducting wire provides a new way.
For solving the problems of the technologies described above, the technical solution used in the present invention is: a kind of extrusion process is prepared multicore MgB
2the method of superconducting wire, is characterized in that, the method comprises the following steps:
Step 1, in vacuum glove box, under argon gas atmosphere protective condition by magnesium powder, amorphous boron powder and doping powder according to Mg:B: doping powder=1:(2-x): the mol ratio of x is prepared burden, then ground and mixed obtains Precursor Powder after evenly, described doping powder is carborundum, titanium carbide or active carbon, and the value of described x is 0.05～0.10;
Step 2, Precursor Powder described in step 1 is packed in Nb/Cu composite bushing, obtain once-combined body, then described once-combined body is carried out to drawing processing, obtain having the single-core wire of regular hexagonal section; The inscribed circle diameter of described regular hexagonal section is 8.5mm～12mm, and the pass reduction of described drawing processing is 10%～15%; In described Nb/Cu composite bushing, Nb is interior barrier layer, and Cu is outer stabilized zone, and in Nb/Cu composite bushing, the mass ratio of Nb and Cu is 1:(1.2～1.6);
Step 3, single-core wire described in copper rod, 1 Nb/Cu compound bar and 6 or 18 step 2 is placed in to oxygen-free copper pipe carries out secondary assembling and obtain secondary complex, the detailed process of described secondary assembling is: the center that 1 Nb/Cu compound bar is placed in to oxygen-free copper pipe, 6 or 18 single-core wires are lined up to circular ring around 1 Nb/Cu compound bar and pack oxygen-free copper pipe into, then adopt copper rod to fill the space between single-core wire and oxygen-free copper pipe; Or single-core wire described in copper rod, 7 Nb/Cu compound bar and 30 or 54 step 2 is placed in to oxygen-free copper pipe to carry out secondary assembling and obtains secondary complex, the detailed process of described secondary assembling is: the center that 7 Nb/Cu compound bar is placed in to oxygen-free copper pipe, 30 or 54 single-core wires are lined up to circular ring around 7 Nb/Cu compound bar and pack in oxygen-free copper pipe, then adopt copper rod to fill the space between single-core wire and oxygen-free copper pipe; In described Nb/Cu compound bar, the mass ratio of Nb and Cu is 1:(0.8～1.2), Nb/Cu compound bar is all identical with shape of cross section and the size of single-core wire;
Step 4, under vacuum condition, soldering and sealing is carried out in the two ends of the complex of secondary described in step 3, secondary complex after soldering and sealing is preheated to 450 ℃～550 ℃ and be incubated 20min～40min, extrusion die is preheated to 300 ℃～400 ℃, then the extrusion die secondary complex after insulation being placed in after preheating carries out extrusion process, obtaining shape of cross section is circular multicore bar, and the diameter of described cross section is for being 16mm～30mm; The extrusion ratio of described extrusion process is 9.38～11.29, and extrusion speed is 5mm/s～20mm/s;
Step 5, the bar of multicore described in step 4 is stripped off the skin to process and remove surface oxidation cortex, pass reduction with 10%～20% carries out drawing processing to the multicore bar stripping off the skin after processing, obtain the Multi-core wire that diameter is 1mm～1.4mm, then described Multi-core wire is placed in to tube furnace, under argon gas atmosphere, heat-treat, obtain multicore MgB
2superconducting wire; Described heat treated temperature is 650 ℃～700 ℃, and the heat treated time is 1.5h～3h.
Above-mentioned a kind of extrusion process is prepared multicore MgB
2the method of superconducting wire, it is characterized in that, the quality purity of the powder of magnesium described in step 1 is not less than 99%, the granularity of magnesium powder is-325 orders, the quality purity of described amorphous boron powder is not less than 99%, the granularity of amorphous boron powder is 0.1 μ m～1 μ m, and the quality purity of described doping powder is not less than 99%, and the granularity of doping powder is 1 μ m～10 μ m.
Above-mentioned a kind of extrusion process is prepared multicore MgB
2the method of superconducting wire, is characterized in that, extrusion speed described in step 4 is 10mm/s～15mm/s.
Above-mentioned a kind of extrusion process is prepared multicore MgB
2the method of superconducting wire, is characterized in that, described extrusion speed is 12mm/s.
Above-mentioned a kind of extrusion process is prepared multicore MgB
2the method of superconducting wire, is characterized in that, the quality purity of argon gas described in step 5 is not less than 99.999%.
The present invention compared with prior art has the following advantages:
1, on the basis of traditional powder tubulature technique, to adopt larger single pass extrusion process deflection be that extrusion-processing technology is prepared multicore MgB to method of the present invention
2superconducting wire, during due to extruding, secondary complex, in very favorable three-dimensional stress state, is followed larger extrusion deformation degree, and in secondary complex, good metallurgical binding can be realized in different metal interface, the combined strength bination of the multicore bar of preparation is higher, can significantly improve multicore MgB
2the density of superconducting wire and yield strength are practical km magnitude MgB
2the mass production of superconducting wire provides a new way.
2, the present invention, by inserting many copper rods in the space between single-core wire and oxygen-free copper pipe, fills the space existing in secondary complex, can avoid in extrusion process process because the MgB that mushrooming deformation causes
2the inconsistent phenomenon that the transversely deforming of superconducting core silk and core silk distribute, is conducive to improve MgB
2the density of superconducting wire.
3, in the present invention, secondary complex is carried out to extrusion process after preheating, can reduce the resistance of deformation of secondary complex in extrusion process, be conducive to obtain the uniform multicore bar of deformation, in addition, the deflection of extrusion process process reaches more than 90%, can significantly improve MgB
2the density of superconducting wire SMIS silk, reduces the hole in core silk, improves MgB
2the connectivity of superconduction crystal grain, thus MgB improved
2engineering critical current density (the J of superconducting wire
e).
Below by drawings and Examples, technical scheme of the present invention is described in further detail.
Accompanying drawing explanation
Fig. 1 is the structural representation that the embodiment of the present invention is assembled the secondary complex obtaining for 1 two times.
Fig. 2 is the multicore MgB of the embodiment of the present invention 1 preparation
2the SEM photo of superconducting wire cross section.
Fig. 3 is the multicore MgB of comparative example 1 preparation
2the SEM photo of superconducting wire cross section.
Description of reference numerals:
1-single-core wire; 2-Nb/Cu compound bar; 3-oxygen-free copper pipe;
4-copper rod.
Embodiment
Embodiment 1
Step 1, in vacuum glove box, under argon gas atmosphere protective condition by magnesium powder, amorphous boron powder and doping powder are according to Mg:B: the mol ratio of doping powder=1:1.92:0.08 is prepared burden, then ground and mixed obtains Precursor Powder after evenly, described doping powder is carborundum, the quality purity of described magnesium powder is not less than 99%, the granularity of magnesium powder is-325 orders, the quality purity of described amorphous boron powder is not less than 99%, the granularity of amorphous boron powder is 0.1 μ m～1 μ m, the quality purity of described doping powder is not less than 99%, the granularity of doping powder is 1 μ m～10 μ m,
Step 2, to pack Precursor Powder described in step 1 into external diameter be in 15mm, the internal diameter Nb/Cu composite bushing that is 10mm, obtain once-combined body, then described once-combined body is first processed to 2 passages, with 12% pass reduction drawing, processed 2 passages again with 15% pass reduction drawing, obtain the pole that diameter is 11.2mm, then through 4 passage six side's mould drawings, obtain having the single-core wire 1 of regular hexagonal section with 10% pass reduction; The inscribed circle diameter of described regular hexagonal section is 8.65mm; In described Nb/Cu composite bushing, Nb is interior barrier layer, and Cu is outer stabilized zone, and in Nb/Cu composite bushing, the mass ratio of Nb and Cu is 1:1.4;
Step 3, single-core wire 1 described in 4,1 Nb/Cu compound bar 2 of copper rod and 18 step 2 is placed in to external diameter is that 64mm, internal diameter are that 44.5mm, length are that 170mm oxygen-free copper pipe 3 carries out secondary assembling and obtains secondary complex (as Fig. 1 shows), the detailed process of described secondary assembling is: the center that 1 Nb/Cu compound bar 2 is placed in to oxygen-free copper pipe 3,18 single-core wires 1 are lined up to circular ring around Nb/Cu compound bar 2 and pack in oxygen-free copper pipe 3, the space that then adopts copper rod 4 to fill between single-core wire 1 and oxygen-free copper pipe 3; In specific implementation process, select the copper rod 4 (diameter is 3.8mm, 2.5mm and 1.6mm) of different size, according to first filling chile bar, in chile bar gap, fill afterwards the principle of thin copper bar and fill, until fill up described secondary complex; In described Nb/Cu compound bar 2, the mass ratio of Nb and Cu is 1:1, and Nb/Cu compound bar 2 is identical with the shape of cross section of single-core wire 1, and Nb/Cu compound bar 2 is measure-alike with single-core wire 1;
Step 4, under vacuum condition, soldering and sealing is carried out in the two ends of the complex of secondary described in step 3, secondary complex after soldering and sealing is preheated to 500 ℃ and be incubated 30min, extrusion die is preheated to 350 ℃, then the extrusion die secondary complex after insulation being placed in after preheating carries out extrusion process, obtaining the uniform shape of cross section of deformation is circular multicore bar, and the diameter of described cross section is for being 20mm; The extrusion ratio of described extrusion process is 10.24, and extrusion speed is 12mm/s;
Step 5, the bar of multicore described in step 4 is stripped off the skin to process with the scalping mold of Φ 19.5mm and remove surface oxidation cortex, the multicore bar stripping off the skin after processing is carried out to drawing processing, obtain the Multi-core wire that diameter is 1mm, then described Multi-core wire is placed in to tube furnace, at quality purity, be not less than under 99.999% argon gas atmosphere and heat-treat, obtain multicore MgB
2superconducting wire; The detailed process of described drawing processing is: first with 20% pass reduction drawing, process 18 passages, with 15% pass reduction drawing, process 8 passages again, with 12% pass reduction drawing, process 2 passages again, then with 10% pass reduction drawing, process 3 passages, finally obtain the Multi-core wire that diameter is 1mm; Described heat treated temperature is 670 ℃, and the heat treated time is 2h.
Fig. 2 is the multicore MgB of the embodiment of the present invention 1 preparation
2the SEM photo of superconducting wire cross section, as can be seen from Figure 2, multicore MgB prepared by the present embodiment
2mgB in superconducting wire
2superconductor particles is very thin, and crystal structure is comparatively fine and close, and intercrystalline has extraordinary connectedness, and without obviously hole and crackle occur.
Multicore MgB prepared by the present embodiment
2the surrender hardness of superconducting wire is 120MPa, and engineering critical current density is 1.24 * 10
5a/cm
2(20K, self-fields).
Comparative example 1
Comparative example 1 is identical with embodiment 1, and its difference is: the secondary complex step 3 not being obtained carries out preheating and the extrusion process of step 4, but directly described secondary complex is carried out to drawing processing and the heat treatment in step 5, obtains multicore MgB
2superconducting wire.
The multicore MgB of comparative example 1 preparation
2the yield strength of superconducting wire is 80MPa, and engineering critical current density is 9 * 10
4a/cm
2(20K, self-fields).
Fig. 3 is the multicore MgB of comparative example 1 preparation
2the SEM photo of superconducting wire cross section, as can be seen from Figure 3, the multicore MgB of comparative example 1 preparation
2in superconducting wire, have the more hole that is of a size of micron dimension, the existence of these holes has reduced MgB
2link performance and the MgB of superconductor particles
2the density of superconducting phase.In conjunction with above-mentioned, find out, extrusion process after preheating in embodiment 1, can reduce the resistance of deformation of secondary complex in extrusion process, is conducive to obtain the uniform multicore bar of deformation, can significantly improve MgB
2the density of superconducting wire SMIS silk, reduces the hole in core silk, improves MgB
2the connectivity of superconduction crystal grain, thus MgB improved
2the engineering critical current density of superconducting wire.
Embodiment 2
Step 1, in vacuum glove box, under argon gas atmosphere protective condition by magnesium powder, amorphous boron powder and doping powder are according to Mg:B: the mol ratio of doping powder=1:1.90:0.10 is prepared burden, then ground and mixed obtains Precursor Powder after evenly, described doping powder is titanium carbide, the quality purity of described magnesium powder is not less than 99%, the granularity of magnesium powder is-325 orders, the quality purity of described amorphous boron powder is not less than 99%, the granularity of amorphous boron powder is 0.1 μ m～1 μ m, the quality purity of described doping powder is not less than 99%, the granularity of doping powder is 1 μ m～10 μ m,
Step 2, packing Precursor Powder described in step 1 into external diameter is 15mm, internal diameter is in the Nb/Cu composite bushing of 8mm, obtain once-combined body, then described once-combined body is first processed to 4 passages with 12% pass reduction drawing, obtain the pole that diameter is 11.6mm, with 10% pass reduction, through 5 passage six side's mould drawings, obtain having the single-core wire 1 of regular hexagonal section again, the inscribed circle diameter of described regular hexagonal section is 8.5mm, in described Nb/Cu composite bushing, Nb is interior barrier layer, Cu is outer stabilized zone, in Nb/Cu composite bushing, the mass ratio of Nb and Cu is 1:1.2,
Step 3, single-core wire 1 described in 4,7 Nb/Cu compound bar 2 of copper rod and 54 step 2 is placed in to external diameter is that 100mm, internal diameter are that 78mm, length are that 300mm oxygen-free copper pipe 3 carries out secondary assembling and obtains secondary complex, the detailed process of described secondary assembling is: the center that 7 Nb/Cu compound bar 2 is placed in to oxygen-free copper pipe 3,54 single-core wires 1 are lined up to circular ring around 7 Nb/Cu compound bar 2 and pack in oxygen-free copper pipe 3, the space that then adopts copper rod 4 to fill between single-core wire 1 and oxygen-free copper pipe 3; In specific implementation process, select the copper rod 4 (diameter is 6mm, 4mm, 3.2mm, 2.5mm, 1.5mm and 1.0mm) of different size, according to first filling chile bar, in chile bar gap, fill afterwards the principle of thin copper bar and fill, until fill up described secondary complex; In described Nb/Cu compound bar 2, the mass ratio of Nb and Cu is 1:0.8, and Nb/Cu compound bar 2 is identical with the shape of cross section of single-core wire 1, and Nb/Cu compound bar 2 is measure-alike with single-core wire 1;
Step 4, under vacuum condition, soldering and sealing is carried out in the two ends of the complex of secondary described in step 3, secondary complex after soldering and sealing is preheated to 450 ℃ and be incubated 40min, extrusion die is preheated to 400 ℃, then the extrusion die secondary complex after insulation being placed in after preheating carries out extrusion process, obtaining the uniform shape of cross section of deformation is circular multicore bar, and the diameter of described cross section is for being 30mm; The extrusion ratio of described extrusion process is 10.89, and extrusion speed is 5mm/s;
Step 5, the bar of multicore described in step 4 is stripped off the skin to process with the scalping mold of Φ 29.5mm and remove surface oxidation cortex, the multicore bar stripping off the skin after processing is carried out to drawing processing, obtain the Multi-core wire that diameter is 1.4mm, then described Multi-core wire is placed in to tube furnace, at quality purity, be not less than under 99.999% argon gas atmosphere and heat-treat, obtain multicore MgB
2superconducting wire; The detailed process of described drawing processing is: first with 20% pass reduction drawing, process 21 passages, with 15% pass reduction drawing, process 6 passages again, then with 10% pass reduction drawing, process 4 passages, finally obtain the Multi-core wire that diameter is 1.4mm; Described heat treated temperature is 700 ℃, and the heat treated time is 1.5h.
Multicore MgB prepared by the present embodiment
2the surrender hardness of superconducting wire is 115MPa, and engineering critical current density is 1.13 * 10
5a/cm
2(20K, self-fields).Extrusion process after preheating in the present embodiment, can reduce the resistance of deformation of secondary complex in extrusion process, is conducive to obtain the uniform multicore bar of deformation, can significantly improve MgB
2the density of superconducting wire SMIS silk, reduces the hole in core silk, improves MgB
2the connectivity of superconduction crystal grain, thus MgB improved
2the engineering critical current density of superconducting wire.
Embodiment 3
Step 1, in vacuum glove box, under argon gas atmosphere protective condition by magnesium powder, amorphous boron powder and doping powder are according to Mg:B: the mol ratio of doping powder=1:1.95:0.05 is prepared burden, then ground and mixed obtains Precursor Powder after evenly, described doping powder is active carbon, the quality purity of described magnesium powder is not less than 99%, the granularity of magnesium powder is-325 orders, the quality purity of described amorphous boron powder is not less than 99%, the granularity of amorphous boron powder is 0.1 μ m～1 μ m, the quality purity of described doping powder is not less than 99%, the granularity of doping powder is 1 μ m～10 μ m,
Step 2, to pack Precursor Powder described in step 1 into external diameter be in 18mm, the internal diameter Nb/Cu composite bushing that is 10mm, obtain once-combined body, then described once-combined body is first processed to 1 passage, with 12% pass reduction drawing, processed 2 passages again with 13% pass reduction drawing, obtain the pole that diameter is 14.8mm, with 10% pass reduction, obtain having the single-core wire 1 of regular hexagonal section through 3 passage six side's mould drawings again, the inscribed circle diameter of described regular hexagonal section is 12mm; In described Nb/Cu composite bushing, Nb is interior barrier layer, and Cu is outer stabilized zone, and in Nb/Cu composite bushing, the mass ratio of Nb and Cu is 1:1.6;
Step 3, single-core wire 1 described in 4,1 Nb/Cu compound bar 2 of copper rod and 6 step 2 is placed in to external diameter is that 49mm, internal diameter are that 37mm, length are that 200mm oxygen-free copper pipe oxygen-free copper pipe 3 carries out secondary assembling and obtains secondary complex, the detailed process of described secondary assembling is: the center that 1 Nb/Cu compound bar 2 is placed in to oxygen-free copper pipe 3,6 single-core wires 1 are lined up to circular ring around 1 Nb/Cu compound bar 2 and pack in oxygen-free copper pipe 3, the space that then adopts copper rod 4 to fill between single-core wire 1 and oxygen-free copper pipe 3; In specific implementation process, select the copper rod 4 (diameter is 3.2mm, 2.5mm and 1.0mm) of different size, according to first filling chile bar, in chile bar gap, fill afterwards the principle of thin copper bar and fill, until fill up described secondary complex; In described Nb/Cu compound bar 2, the mass ratio of Nb and Cu is 1:1.2, and Nb/Cu compound bar 2 is identical with the shape of cross section of single-core wire 1, and Nb/Cu compound bar 2 is measure-alike with single-core wire 1;
Step 4, under vacuum condition, soldering and sealing is carried out in the two ends of the complex of secondary described in step 3, secondary complex after soldering and sealing is preheated to 550 ℃ and be incubated 20min, extrusion die is preheated to 300 ℃, then the extrusion die secondary complex after insulation being placed in after preheating carries out extrusion process, obtaining the uniform shape of cross section of deformation is circular multicore bar, and the diameter of described cross section is for being 16mm; The extrusion ratio of described extrusion process is 9.38, and extrusion speed is 20mm/s;
Step 5, the bar of multicore described in step 4 is stripped off the skin to process with the scalping mold of Φ 15.5mm and remove surface oxidation cortex, the multicore bar stripping off the skin after processing is carried out to drawing processing, obtain the Multi-core wire that diameter is 1mm, then described Multi-core wire is placed in to tube furnace, at quality purity, be not less than under 99.999% argon gas atmosphere and heat-treat, obtain multicore MgB
2superconducting wire; The detailed process of described drawing processing is: first with 20% pass reduction drawing, process 15 passages, with 15% pass reduction drawing, process 9 passages again, then with 10% pass reduction drawing, process 6 passages, finally obtain the Multi-core wire that diameter is 1mm; Described heat treated temperature is 650 ℃, and the heat treated time is 3h.
Multicore MgB prepared by the present embodiment
2the surrender hardness of superconducting wire is 126MPa, and engineering critical current density is 1.16 * 10
5a/cm
2(20K, self-fields).Extrusion process after preheating in the present embodiment, can reduce the resistance of deformation of secondary complex in extrusion process, is conducive to obtain the uniform multicore bar of deformation, can significantly improve MgB
2the density of superconducting wire SMIS silk, reduces the hole in core silk, improves MgB
2the connectivity of superconduction crystal grain, thus MgB improved
2the engineering critical current density of superconducting wire.
Embodiment 4
Step 1, in vacuum glove box, under argon gas atmosphere protective condition by magnesium powder, amorphous boron powder and doping powder are according to Mg:B: the mol ratio of doping powder=1:1.93:0.07 is prepared burden, then ground and mixed obtains Precursor Powder after evenly, described doping powder is carborundum, the quality purity of described magnesium powder is not less than 99%, the granularity of magnesium powder is-325 orders, the quality purity of described amorphous boron powder is not less than 99%, the granularity of amorphous boron powder is 0.1 μ m～1 μ m, the quality purity of described doping powder is not less than 99%, the granularity of doping powder is 1 μ m～10 μ m,
Step 2, to pack Precursor Powder described in step 1 into external diameter be in 14mm, the internal diameter Nb/Cu composite bushing that is 10mm, obtain once-combined body, then described once-combined body is first processed to 1 passage, with 13% pass reduction drawing, processed 1 passage again with 15% pass reduction drawing, obtain the pole that diameter is 12mm, with 10% pass reduction, obtain having the single-core wire 1 of regular hexagonal section through 5 passage six side's mould drawings again, the inscribed circle diameter of described regular hexagonal section is 8.8mm; In described Nb/Cu composite bushing, Nb is interior barrier layer, and Cu is outer stabilized zone, and in Nb/Cu composite bushing, the mass ratio of Nb and Cu is 1:1.5;
Step 3, single-core wire 1 described in 4,7 Nb/Cu compound bar 2 of copper rod and 30 step 2 is placed in to external diameter is that 84mm, internal diameter are that oxygen-free copper pipe 3 that 63mm, length are 230mm carries out secondary assembling and obtains secondary complex, the detailed process of described secondary assembling is: the center that 7 Nb/Cu compound bar 2 is placed in to oxygen-free copper pipe 3,30 single-core wires 1 are lined up to circular ring around 7 Nb/Cu compound bar 2 and pack in oxygen-free copper pipe 3, the space that then adopts copper rod 4 to fill between single-core wire 1 and oxygen-free copper pipe 3; In specific implementation process, select the copper rod 4 (diameter is 5mm, 3.8mm, 2.5mm and 1.5mm) of different size, according to first filling chile bar, in chile bar gap, fill afterwards the principle of thin copper bar and fill, until fill up described secondary complex; In described Nb/Cu compound bar 2, the mass ratio of Nb and Cu is 1:1.1, and Nb/Cu compound bar 2 is identical with the shape of cross section of single-core wire 1, and Nb/Cu compound bar 2 is measure-alike with single-core wire 1;
Step 4, under vacuum condition, soldering and sealing is carried out in the two ends of the complex of secondary described in step 3, secondary complex after soldering and sealing is preheated to 520 ℃ and be incubated 35min, extrusion die is preheated to 380 ℃, then the extrusion die secondary complex after insulation being placed in after preheating carries out extrusion process, obtaining the uniform shape of cross section of deformation is circular multicore bar, and the diameter of described cross section is for being 25mm; The extrusion ratio of described extrusion process is 11.29, and extrusion speed is 15mm/s;
Step 5, the bar of multicore described in step 4 is stripped off the skin to process with the scalping mold of Φ 24.5mm and remove surface oxidation cortex, the multicore bar stripping off the skin after processing is carried out to drawing processing, obtain the Multi-core wire that diameter is 1.2mm, then described Multi-core wire is placed in to tube furnace, at quality purity, be not less than under 99.999% argon gas atmosphere and heat-treat, obtain multicore MgB
2superconducting wire; The detailed process of described drawing processing is: first with 20% pass reduction drawing, process 21 passages, with 15% pass reduction drawing, process 5 passages again, then with 10% pass reduction drawing, process 5 passages, finally obtain the Multi-core wire that diameter is 1.2mm; Described heat treated temperature is 660 ℃, and the heat treated time is 2.5h.
Multicore MgB prepared by the present embodiment
2the surrender hardness of superconducting wire is 117MPa, and engineering critical current density is 1.2 * 10
5a/cm
2(20K, self-fields).Extrusion process after preheating in the present embodiment, can reduce the resistance of deformation of secondary complex in extrusion process, is conducive to obtain the uniform multicore bar of deformation, can significantly improve MgB
2the density of superconducting wire SMIS silk, reduces the hole in core silk, improves MgB
2the connectivity of superconduction crystal grain, thus MgB improved
2the engineering critical current density of superconducting wire.
Embodiment 5
Step 1, in vacuum glove box, under argon gas atmosphere protective condition by magnesium powder, amorphous boron powder and doping powder are according to Mg:B: the mol ratio of doping powder=1:1.94:0.06 is prepared burden, then ground and mixed obtains Precursor Powder after evenly, described doping powder is active carbon, the quality purity of described magnesium powder is not less than 99%, the granularity of magnesium powder is-325 orders, the quality purity of described amorphous boron powder is not less than 99%, the granularity of amorphous boron powder is 0.1 μ m～1 μ m, the quality purity of described doping powder is not less than 99%, the granularity of doping powder is 1 μ m～10 μ m,
Step 2, packing Precursor Powder described in step 1 into external diameter is 18mm, internal diameter is in the Nb/Cu composite bushing of 8mm, obtain once-combined body, then described once-combined body is first processed to 1 passage with 15% pass reduction drawing, with 13% pass reduction drawing, process 1 passage again, with 12% pass reduction drawing, process 2 passages again, obtain the pole that diameter is 13.6mm, again with 10% pass reduction through 4 passage six side's mould drawings, obtain having the single-core wire 1 of regular hexagonal section, the inscribed circle diameter of described regular hexagonal section is 10.5mm, in described Nb/Cu composite bushing, Nb is interior barrier layer, and Cu is outer stabilized zone, and in Nb/Cu composite bushing, the mass ratio of Nb and Cu is 1:1.3,
Step 3, single-core wire 1 described in 4,1 Nb/Cu compound bar 2 of copper rod and 6 step 2 is placed in to external diameter is that 56mm, internal diameter are that 33mm, length are that 180mm oxygen-free copper pipe oxygen-free copper pipe 3 carries out secondary assembling and obtains secondary complex, the detailed process of described secondary assembling is: the center that 1 Nb/Cu compound bar 2 is placed in to oxygen-free copper pipe 3,6 single-core wires 1 are lined up to circular ring around 1 Nb/Cu compound bar 2 and pack in oxygen-free copper pipe 3, the space that then adopts copper rod 4 to fill between single-core wire 1 and oxygen-free copper pipe 3; In specific implementation process, select the copper rod 4 (diameter is 3.2mm, 2.5mm and 1.0mm) of different size, according to first filling chile bar, in chile bar gap, fill afterwards the principle of thin copper bar and fill, until fill up described secondary complex; In described Nb/Cu compound bar 2, the mass ratio of Nb and Cu is 1:0.9, and Nb/Cu compound bar 2 is identical with the shape of cross section of single-core wire 1, and Nb/Cu compound bar 2 is measure-alike with single-core wire 1;
Step 4, under vacuum condition, soldering and sealing is carried out in the two ends of the complex of secondary described in step 3, secondary complex after soldering and sealing is preheated to 530 ℃ and be incubated 25min, extrusion die is preheated to 320 ℃, then the extrusion die secondary complex after insulation being placed in after preheating carries out extrusion process, obtaining the uniform shape of cross section of deformation is circular multicore bar, and the diameter of described cross section is for being 18mm; The extrusion ratio of described extrusion process is 9.68, and extrusion speed is 10mm/s;
Step 5, the bar of multicore described in step 4 is stripped off the skin to process with the scalping mold of Φ 17.5mm and remove surface oxidation cortex, the multicore bar stripping off the skin after processing is carried out to drawing processing, obtain the Multi-core wire that diameter is 1.1mm, then described Multi-core wire is placed in to tube furnace, at quality purity, be not less than under 99.999% argon gas atmosphere and heat-treat, obtain multicore MgB
2superconducting wire; The detailed process of described drawing processing is: first with 20% pass reduction drawing, process 13 passages, with 15% pass reduction drawing, process 13 passages again, then with 10% pass reduction drawing, process 5 passages, finally obtain the Multi-core wire that diameter is 1.1mm; Described heat treated temperature is 680 ℃, and the heat treated time is 1.75h.
Multicore MgB prepared by the present embodiment
2the surrender hardness of superconducting wire is 118MPa, and engineering critical current density is 1.15 * 10
5a/cm
2(20K, self-fields).Extrusion process after preheating in the present embodiment, can reduce the resistance of deformation of secondary complex in extrusion process, is conducive to obtain the uniform multicore bar of deformation, can significantly improve MgB
2the density of superconducting wire SMIS silk, reduces the hole in core silk, improves MgB
2the connectivity of superconduction crystal grain, thus MgB improved
2the engineering critical current density of superconducting wire.
The above; it is only preferred embodiment of the present invention; not the present invention is imposed any restrictions, every any simple modification of above embodiment being done according to the technology of the present invention essence, change and equivalent structure change, and all still belong in the protection range of technical solution of the present invention.
Claims (5)
1. an extrusion process is prepared multicore MgB
2the method of superconducting wire, is characterized in that, the method comprises the following steps:
Step 1, in vacuum glove box, under argon gas atmosphere protective condition by magnesium powder, amorphous boron powder and doping powder according to Mg:B: doping powder=1:(2-x): the mol ratio of x is prepared burden, then ground and mixed obtains Precursor Powder after evenly, described doping powder is carborundum, titanium carbide or active carbon, and the value of described x is 0.05～0.10;
Step 2, Precursor Powder described in step 1 is packed in Nb/Cu composite bushing, obtain once-combined body, then described once-combined body is carried out to drawing processing, obtain having the single-core wire (1) of regular hexagonal section; The inscribed circle diameter of described regular hexagonal section is 8.5mm～12mm, and the pass reduction of described drawing processing is 10%～15%; In described Nb/Cu composite bushing, Nb is interior barrier layer, and Cu is outer stabilized zone, and in Nb/Cu composite bushing, the mass ratio of Nb and Cu is 1:(1.2～1.6);
Step 3, copper rod (4), 1 Nb/Cu compound bar (2) and single-core wire (1) described in 6 or 18 step 2 are placed in to oxygen-free copper pipe (3) carry out secondary assembling and obtain secondary complex, the detailed process of described secondary assembling is: the center that 1 Nb/Cu compound bar (2) is placed in to oxygen-free copper pipe (3), 6 or 18 single-core wires (1) are lined up to circular ring around 1 Nb/Cu compound bar (2) and pack oxygen-free copper pipe (3) into, then adopt copper rod (4) to fill the space between single-core wire (1) and oxygen-free copper pipe (3); Or copper rod (4), 7 Nb/Cu compound bar (2) and single-core wire (1) described in 30 or 54 step 2 are placed in to oxygen-free copper pipe (3) to carry out secondary assembling and obtains secondary complex, the detailed process of described secondary assembling is: the center that 7 Nb/Cu compound bar (2) is placed in to oxygen-free copper pipe (3), 30 or 54 single-core wires (1) are lined up to circular ring around 7 Nb/Cu compound bar (2) and pack in oxygen-free copper pipe (3), then adopt copper rod (4) to fill the space between single-core wire (1) and oxygen-free copper pipe (3); In described Nb/Cu compound bar (2), the mass ratio of Nb and Cu is 1:(0.8～1.2), Nb/Cu compound bar (2) is all identical with shape of cross section and the size of single-core wire (1);
Step 4, under vacuum condition, soldering and sealing is carried out in the two ends of the complex of secondary described in step 3, secondary complex after soldering and sealing is preheated to 450 ℃～550 ℃ and be incubated 20min～40min, extrusion die is preheated to 300 ℃～400 ℃, then the extrusion die secondary complex after insulation being placed in after preheating carries out extrusion process, obtaining shape of cross section is circular multicore bar, and the diameter of described cross section is 16mm～30mm; The extrusion ratio of described extrusion process is 9.38～11.29, and extrusion speed is 5mm/s～20mm/s;
Step 5, the bar of multicore described in step 4 is stripped off the skin to process and remove surface oxidation cortex, pass reduction with 10%～20% carries out drawing processing to the multicore bar stripping off the skin after processing, obtain the Multi-core wire that diameter is 1mm～1.4mm, then described Multi-core wire is placed in to tube furnace, under argon gas atmosphere, heat-treat, obtain multicore MgB
2superconducting wire; Described heat treated temperature is 650 ℃～700 ℃, and the heat treated time is 1.5h～3h.
2. according to a kind of extrusion process claimed in claim 1, prepare multicore MgB
2the method of superconducting wire, it is characterized in that, the quality purity of the powder of magnesium described in step 1 is not less than 99%, the granularity of magnesium powder is-325 orders, the quality purity of described amorphous boron powder is not less than 99%, the granularity of amorphous boron powder is 0.1 μ m～1 μ m, and the quality purity of described doping powder is not less than 99%, and the granularity of doping powder is 1 μ m～10 μ m.
3. according to a kind of extrusion process claimed in claim 1, prepare multicore MgB
2the method of superconducting wire, is characterized in that, extrusion speed described in step 4 is 10mm/s～15mm/s.
4. according to a kind of extrusion process claimed in claim 3, prepare multicore MgB
2the method of superconducting wire, is characterized in that, described extrusion speed is 12mm/s.
5. according to a kind of extrusion process claimed in claim 1, prepare multicore MgB
2the method of superconducting wire, is characterized in that, the quality purity of argon gas described in step 5 is not less than 99.999%.
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