CN102354579A - Preparation method of NbTi/Cu superconducting wire used for magnetic resonance imaging (MRI) - Google Patents

Abstract

The invention relates to a preparation method of a NbTi/Cu superconducting wire used for magnetic resonance imaging (MRI). The preparation method is technically characterized by comprising the following steps: carrying out deep hole drilling on a Cu ingot, thus obtaining a porous Cu ingot with 15-100 holes, wherein the holes are uniformly distributed on 1-6 layers of concentric circles which take the center of the Cu ingot as a center; then inserting a NbTi/Cu single-core bar into the porous Cu ingot, wherein the ratio of the cross-sectional area of a Cu substrate to the total cross-sectional area of a NbTi alloy bar is 2-10; and finally carrying out welding and cap sealing on two ends by using copper caps, extruding, and then repeatedly drawing and annealing, thus obtaining the NbTi/Cu superconducting wire, wherein the diameter of the core of the NbTi/Cu superconducting wire is 50-150 mu m, and the ratio of the pitch of holes to the diameter of the core of the NbTi/Cu superconducting wire is 0.15-0.45. By utilizing the preparation method provided by the invention to prepare the NbTi/Cu superconducting wire used for MRI, the process can be simplified, and the yield can be improved, thus the production cost is lowered.

Description

A kind of method for preparing MRI with the NbTi superconducting line

Technical field

The present invention relates to the method for a kind of MRI of preparation, belong to the superconductor processing technique field, relate to the method for a kind of MRI of preparation with the NbTi superconducting line with the NbTi superconducting line.

Background technology

MRI (Magnetic resonance imaging, Magnetic Resonance Imaging) is the indispensable diagnostic tool of modern medicine, and it has non-intruding, radiationless, Diagnostic Time is short, accuracy is high characteristics.Present MRI (by 0.3T to 3.0T) more than 70% adopts cryogenic magnet.The MRI system adopts superconducting magnet can guarantee to produce most effectively even, the stable and powerful magnetic field boundary of the desired height of NMR (Nuclear Magnetic Resonance) imaging, thereby obtains distinct image.Superconducting magnet is mainly formed by the coiling of NbTi/Cu superconducting line as the critical component among the MRI.The NbTi/Cu superconducting line that traditional preparation MRI uses mainly is a secondary assembling extrusion; It is compound with the copper matrix to be about to the NbTi rod; Form single core NbTi six square rods through extruding, drawing; Circular copper-clad cover will be put into again behind NbTi six square rods and the Cu six square rod boundlings; And the circular copper plunger that adopts different size fills six square rods and the space that circular copper-clad overlaps, and is compounded to form multicore NbTi/Cu compound bar.Process multicore NbTi/Cu superconducting wire through extruding, drawing.Though this preparation method's technology is ripe relatively, the various operating efficiency that causes of operation is lower, thereby makes cost higher relatively.Therefore, be necessary to develop a kind of new NbTi/Cu superconducting line preparation method, enhance productivity, reduce cost.

Summary of the invention

The technical problem that solves

For fear of the weak point of prior art, the present invention proposes the method for a kind of MRI of preparation with the NbTi superconducting line, after NbTi pole and the compound soldering and sealing of porous C u ingot, processes the boring extrusion of multicore NbTi/Cu superconducting wire through extruding, drawing.

Technical scheme

A kind of method for preparing MRI with the NbTi superconducting line is characterized in that step is following:

Step 1: with diameter is excellent the insertion in the Cu pipe that external diameter is Φ 100～300mm of NbTi of Φ 100～300mm, and cap seal is covered with copper in two ends; Adopting extruding and drawing process to obtain the single plug of NbTi/Cu of Φ 10～30mm, is 300～800mm through aligning, cutting into length again, cleans subsequent use;

Step 2: carry out the boring that the degree of depth is 300～800mm after getting the Cu ingot cleaning that D outer diameter 0 is 300～800mm for Φ 100～300mm, height h, obtain the porous C u ingot in 15～100 holes; It is on 1 to 6 layer of concentric circles at center that said hole is evenly distributed in the Cu ingot center of circle, and outermost core silk is arranged diameter D1 less than 0.85D0; Import centre deviation＜the 0.5mm in said hole, the export center deviation＜1mm in hole; Clean the Cu ingot after the boring subsequent use;

Step 3: with the single plug of the NbTi/Cu of step 1 preparation; In the porous C u ingot that inserting step 2 prepares; Wherein total cross-sectional area ratio of the cross-sectional area of Cu matrix and NbTi alloy bar is 2～10, after cap seal is covered with copper in the Cu ingot two ends that insertion NbTi is excellent, obtains the compound billet of multicore;

Step 4: the compound billet of the multicore after the soldering and sealing is pushed behind insulation 30～120min down at 520～650 ℃; Extrusion ratio is 8～20; The extrusion die diameter is Φ 30～100mm, and extrusion speed is 10～40mm/s, and obtaining diameter is the multicore NbTi/Cu Compound Extrusion rod of Φ 40～80mm;

Step 5: the multicore NbTi/Cu Compound Extrusion rod that step 4 is obtained carries out stretching for 10～20 times on stretching-machine, annealing; Draw speed 5～100m/min; Working modulus is 10～20%/passage; Obtaining core filament diameter Df is 50～150 μ m, and the core filament diameter Df ratio of pitch of holes S and NbTi is 0.15～0.45 NbTi/Cu superconducting line.

Beneficial effect

A kind of method for preparing MRI with the NbTi superconducting line that the present invention proposes after NbTi pole and the compound soldering and sealing of porous C u ingot, is processed the boring extrusion of multicore NbTi/Cu superconducting wire through extruding, drawing.This method technology is simple, and rate of finished products is higher, compares with secondary assembling extrusion to have the following advantages: (1) assembling is simple more, convenient.(2) saved the production of six side's copper plugs, copper interpolation slit rod, significantly reduced production process, shortened the production cycle, reduced production costs; (3) improved NbTi rod utilance, adopted secondary assembling extruding, the NbTi rod has the process of single plug and two losses of compound bar, and the overall utilization of NbTi is about 65-70%.And adopting the boring extrusion, the NbTi utilance can be brought up to about 85%.(4) it is cheap that the Cu ingot used of boring method is compared the Cu pipe price comparison that secondary assembling extrusion uses, and so just reduced cost.(5) this method has also reduced the loss of oxygen-free copper when reducing operation, raises the efficiency, and has reduced production cost.

Description of drawings

Fig. 1 is the schematic cross-section that adopts the Cu ingot of boring extrusion;

Fig. 2 is the electron microscope photo scanning that adopts the NbTi/Cu superconducting line that the method for the embodiment of the invention 1 makes.

Embodiment

Combine embodiment, accompanying drawing that the present invention is further described at present:

Embodiment 1:

With diameter is that the single plug of NbTi/Cu of the 23mm diameter of packing into is Φ 255mm; Length is in the 42 core porous copper ingots of 670mm; It is on 2 layers of concentric circles at center that the hole is evenly distributed in Cu ingot center; And the outermost core silk diameter D1 that arranges is 192mm; Total cross-sectional area of the cross-sectional area of Cu matrix and NbTi alloy bar is than 4, and it is added a cover the two ends, back and adopts vacuum electron beam to carry out soldering and sealing.Then billet is heated to 550 ℃ in induction furnace; Push behind the insulation 40min; Extrusion ratio is 10, and the extrusion die diameter is Φ 71, and extrusion speed is 20mm/s; And between with lubricator lubricated billet and the extrusion die; To push rod after extruding is accomplished and on stretching-machine, stretch, draw speed 30m/min, working modulus is selected 20%/passage; Promptly getting the core silk is 95 μ m for diameter Df, and the core filament diameter Df ratio of pitch of holes s and NbTi is 0.3 NbTi/Cu superconducting line.

Embodiment 2:

With diameter is that the single plug of NbTi/Cu of the 15mm diameter of packing into is Φ 180mm; Length is in the 54 core porous copper ingots of 560mm; It is on 3 layers of concentric circles at center that the hole is evenly distributed in Cu ingot center; And the outermost core silk diameter D1 that arranges should be 145mm; The cross-sectional area of Cu matrix is 2.5 with total cross-sectional area ratio of NbTi alloy bar, adds a cover the two ends, back and adopts vacuum electron beam to carry out soldering and sealing.Then billet is heated to 550 ℃ in induction furnace; Push behind the insulation 60min; Extrusion ratio is 13, and the extrusion die diameter is Φ 58, and extrusion speed is 20mm/s; And between with lubricator lubricated billet and the extrusion die; To push rod after extruding is accomplished and on stretching-machine, stretch, draw speed 30m/min, working modulus is selected 20%/passage; Promptly getting the core silk is 75mm for diameter Df, and the core filament diameter Df ratio of pitch of holes s and NbTi is 0.25 NbTi/Cu superconducting line.

Embodiment 3:

With diameter is that the single plug of NbTi/Cu of the 30mm diameter of packing into is Φ 280mm; Length is in the 24 core porous copper ingots of 770mm; It is on 1 layer of concentric circles at center that the hole is evenly distributed in Cu ingot center; And the outermost core silk diameter D1 that arranges should be 217mm; The cross-sectional area of Cu matrix is 7 with total cross-sectional area ratio of NbTi alloy bar, adds a cover the two ends, back and adopts vacuum electron beam to carry out soldering and sealing.Then billet is heated to 550 ℃ in induction furnace; Push behind the insulation 80min; Extrusion ratio is 14, and the extrusion die diameter is Φ 71, and extrusion speed is 20mm/s; And between with lubricator lubricated billet and the extrusion die; To push rod after extruding is accomplished and on stretching-machine, stretch, draw speed 30m/min, working modulus is selected 20%/passage; Promptly getting the core silk is 115 μ m for diameter Df, and the core filament diameter Df ratio of pitch of holes s and NbTi is 0.45 NbTi/Cu superconducting line.

Claims (1)

1. method for preparing MRI with the NbTi superconducting line is characterized in that step is following:

Step 1: with diameter is excellent the insertion in the Cu pipe that external diameter is Φ 100～300mm of NbTi of Φ 100～300mm, and cap seal is covered with copper in two ends; Adopting extruding and drawing process to obtain the single plug of NbTi/Cu of Φ 10～30mm, is 300～800mm through aligning, cutting into length again, cleans subsequent use;

Step 2: carry out the boring that the degree of depth is 300～800mm after getting the Cu ingot cleaning that D outer diameter 0 is 300～800mm for Φ 100～300mm, height h, obtain the porous C u ingot in 15～100 holes; It is on 1 to 6 layer of concentric circles at center that said hole is evenly distributed in the Cu ingot center of circle, and outermost core silk is arranged diameter D1 less than 0.85D0; Import centre deviation＜the 0.5mm in said hole, the export center deviation＜1mm in hole; Clean the Cu ingot after the boring subsequent use;

Step 3: with the single plug of the NbTi/Cu of step 1 preparation; In the porous C u ingot that inserting step 2 prepares; Wherein total cross-sectional area ratio of the cross-sectional area of Cu matrix and NbTi alloy bar is 2～10, after cap seal is covered with copper in the Cu ingot two ends that insertion NbTi is excellent, obtains the compound billet of multicore;

Step 4: the compound billet of the multicore after the soldering and sealing is pushed behind insulation 30～120min down at 520～650 ℃; Extrusion ratio is 8～20; The extrusion die diameter is Φ 30～100mm, and extrusion speed is 10～40mm/s, and obtaining diameter is the multicore NbTi/Cu Compound Extrusion rod of Φ 40～80mm;

Step 5: the multicore NbTi/Cu Compound Extrusion rod that step 4 is obtained carries out stretching for 10～20 times on stretching-machine, annealing; Draw speed 5～100m/min; Working modulus is 10～20%/passage; Obtaining core filament diameter Df is 50～150 μ m, and the core filament diameter Df ratio of pitch of holes S and NbTi is 0.15～0.45 NbTi/Cu superconducting line.

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