Metal wire rod for low-temperature refrigeration as well as preparation method and application of metal wire rod

Abstract

The invention relates to a metal wire rod for low-temperature refrigeration and a preparation method and application thereof.The preparation method comprises the following steps that (1) a metal raw material is put into a crucible and sealed, a micropore piece is arranged at the bottom of the crucible, the crucible is heated by controlling the heating power under the protective atmosphere so that the metal raw material can be molten, then heat preservation refining is conducted, and the metal raw material is obtained; smelting liquid is obtained; and (2) filling protective gas into the crucible, enabling the pressure in the crucible to be greater than the external pressure, extruding the smelting liquid from the microporous sheet under the action of pressure difference and gravity, and then cooling to obtain the metal wire rod. According to the preparation method, the diameter-adjustable metal wire for low-temperature refrigeration can be obtained by regulating and controlling technological parameters, the preparation process is simple and efficient, the product surface is smooth, the size is uniform, and the preparation method is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature refrigeration, and in particular to a metal wire material for low-temperature refrigeration, a preparation method thereof and application thereof. Background Art

[0002] Cryogenic refrigeration technology uses some special materials and equipment to achieve refrigeration under extremely low temperature conditions. It has been widely used in the fields of freezing, cryoelectronics, magnetic resonance imaging, etc. It also has important application value in the fields of precision instrument manufacturing and high-energy physics experiments. Among them, refrigeration technology in the liquid helium temperature zone (2-10K) is widely used in aerospace, biomedicine, and cutting-edge scientific research, and has extremely important strategic significance. Helium is a strategic resource. my country's helium reserves account for only 2% of the world's total reserves, and daily use is highly dependent on imports. At present, many key technical fields involving low-temperature acquisition almost rely on liquid helium, and the cost of use is high, and there is a supply risk. Therefore, the development of liquid helium-free refrigeration technology is particularly urgent and necessary.

[0003] The Gifford-McMahon (GM) refrigerator is a device that uses the Simon expansion principle to achieve refrigeration. It is currently an effective method of low-temperature refrigeration without liquid helium. The GM refrigerator is mainly composed of a compressor unit, an expander, a gas distribution mechanism, a cold storage device and a cold head heat exchanger. Among them, the cold storage device, as a key component of the GM refrigerator, is filled with cold storage materials. The cold storage material has a high specific heat at low temperatures and can store a large amount of cold per unit volume. The GM refrigerator periodically passes hot and cold air flows through the cold storage device to achieve an effective heat exchange process. Lead (Pb) is often used as a filling material for the first-stage cold storage device. The high specific heat property of lead enables it to reduce the temperature to 10K and maintain a large amount of cold in single-stage refrigeration.

[0004] In the practical application of cold storage materials, in addition to requiring them to have the highest possible specific heat capacity, they are also required to have a large specific surface area and a more regular shape while ensuring the highest possible filling rate, so as to reduce the flow resistance of the refrigerant in the cold storage device. Therefore, the filamentary structure is considered to be a relatively ideal structure with good heat exchange effect. However, traditional low-temperature refrigeration materials such as single substances or alloys of lead (Pb), bismuth (Bi), and tin (Sn) have poor mechanical properties and are difficult to obtain through conventional extrusion, drawing or rolling.

[0005] For example, CN101885059A discloses a lead fiber wire and a method for making the same, wherein a lead rod with an outer diameter of 1-110 mm is used on a C-6136A lathe of Jiangsu Yancheng Chenjin Machine Tool Co., Ltd., with a spindle speed of 680-720 r / min, a tool longitudinal feed of 33.77-112.58 mm / min, and a transverse feed of 8.206-164.12 mm / min to obtain a lead wire with a thickness of 0.01-5.00 mm. However, the process of turning to prepare the lead wire is of low production efficiency, a large amount of waste is generated during the turning process, and the mechanical properties of the lead wire are not high.

[0006] Therefore, how to produce cold metal wires for low-temperature processing with uniform composition and fine grains at a lower cost and simpler operation, and how to regulate the diameter of the wires, are technical problems that need to be solved in the current field. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide a metal wire for low-temperature refrigeration and a preparation method and use thereof. Compared with the prior art, the preparation method provided by the present invention can obtain a metal wire for low-temperature refrigeration with adjustable diameter by adjusting process parameters, and the preparation process is simple and efficient, the product surface is smooth, the size is uniform, and it is suitable for industrial production.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a metal wire for low-temperature refrigeration, characterized in that the preparation method comprises the following steps:

[0010] (1) placing a metal raw material into a crucible and sealing it, with a microporous sheet disposed at the bottom of the crucible, heating the crucible under a protective atmosphere by controlling the heating power to melt the metal raw material, and then performing heat preservation and refining to obtain a molten liquid;

[0011] (2) A protective gas is filled into the crucible to make the pressure inside the crucible greater than the external pressure, so that the molten liquid is squeezed out of the microporous sheet under the action of pressure difference and gravity, and then cooled to obtain a metal wire.

[0012] The preparation method provided by the present invention is aimed at the problem of poor mechanical properties of metals used for low-temperature refrigeration. It breaks through the conventional plastic processing ideas such as extrusion, drawing or rolling, and uses pressure difference and gravity to directly spray from liquid melt to prepare metal wire. The diameter of the wire can be conveniently adjusted by regulating the pressure difference, heating power and the diameter of the through hole in the microporous sheet. Rapid outflow and cooling can make the composition of the product uniform, obtain fine-grained structure, and make the product have higher mechanical strength and better plastic toughness. It has good application prospects in the field of low-temperature refrigeration.

[0013] Preferably, the metal raw material in step (1) contains any one of Pb, Bi or Sn, or a combination of at least two of them.

[0014] In the present invention, the metal raw material contains any one of Pb, Bi or Sn or a combination of at least two of them. The obtained metal wire material can be a single substance of Pb, Bi or Sn, or an alloy based on Pb, Bi or Sn. According to performance requirements, any one of Sb, Ag, Cu or Te or a combination of at least two of them can be added to the metal raw material to adjust the performance of the metal wire material.

[0015] Preferably, the purity of the metal raw material is ≥99.9wt.%, for example, it can be 99.90wt.%, 99.91wt.%, 99.92wt.%, 99.93wt.%, 99.94wt.%, 99.95wt.%, 99.96wt.%, 99.97wt.%, 99.98wt.% or 99.99wt.%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] Preferably, the metal raw material is polished to remove oxide scale and impurities on the surface before being placed in the crucible.

[0017] Preferably, the crucible in step (1) is placed in a cavity for heating.

[0018] Preferably, the cavity is evacuated and filled with protective gas in sequence before heating.

[0019] Preferably, the vacuum degree at the end point of the vacuum extraction is ≤5Pa, for example, it can be 5Pa, 4Pa, 3Pa, 2Pa or 1Pa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the protective gas comprises nitrogen and / or an inert gas.

[0021] Preferably, the inert gas comprises argon.

[0022] Preferably, the protective gas is filled into the cavity until the pressure is equal to the external atmospheric pressure.

[0023] Preferably, the heating power in step (1) is 1.0-2.0 kW, for example, 1.0 kW, 1.2 kW, 1.4 kW, 1.6 kW, 1.8 kW or 2.0 kW, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] In the present invention, by optimally controlling the heating power, the superheat of the melt can be effectively controlled while ensuring that the metal raw material can be completely melted. If the heating power is too high, the melt superheat will be too high, which will lead to a large flow diameter, and the liquid will fall directly into the collection device or component without enough time to cool; if the heating power is too low, the metal raw material will not be completely melted.

[0025] Preferably, the heating method includes induction heating.

[0026] Preferably, the heat preservation and refining time in step (1) is 15-30 min, for example, it can be 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, the microporous sheet in step (1) is provided with through holes.

[0028] Preferably, the diameter of the through hole is 0.1-0.2 mm, for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.16 mm, 0.18 mm or 0.2 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] In the present invention, by preferably controlling the diameter of the through hole, the diameter of the wire material can be effectively controlled to prevent it from deviating from the commonly used diameter range of the wire material for low-temperature refrigeration. If the diameter of the through hole is too large, the liquid flow diameter will be too large and will not have time to cool down and will directly fall into the collection device or component; if the diameter of the through hole is too small, the liquid flow cannot be generated and the melt cannot be extruded.

[0030] Preferably, the pressure difference in step (2) is 10-50 kPa, for example, it can be 10 kPa, 12 kPa, 15 kPa, 18 kPa, 20 kPa, 22 kPa, 25 kPa, 28 kPa, 30 kPa, 32 kPa, 35 kPa, 38 kPa, 40 kPa, 42 kPa, 45 kPa, 48 kPa or 50 kPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] In the present invention, by preferably controlling the pressure difference, it is possible to ensure that the melt can be stably extruded from the micropores in the form of a liquid flow. If the pressure difference is too large, the liquid flow will be extruded too quickly and will not have time to cool down and will directly fall into the collection device or component; if the pressure difference is too small, the fluid cannot be generated and the melt will be extruded from the through hole in the form of droplets.

[0032] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0033] (1) grinding a metal raw material to remove oxide scale and impurities on the surface, placing it in a crucible and sealing it, wherein the metal raw material contains any one of Pb, Bi or Sn or a combination of at least two of them, and the purity of the metal raw material is ≥99.9wt.%, a microporous sheet is arranged at the bottom of the crucible, and a through hole with a diameter of 0.1-0.2mm is arranged in the microporous sheet, the crucible is placed in a cavity, and then the cavity is evacuated to an end vacuum degree of ≤5Pa, and then a protective gas is filled until the pressure in the cavity is equal to the external atmospheric pressure, and the heating power is controlled to be 1.0-2.0kW to perform induction heating on the crucible to melt the metal raw material, and then heat preservation and refining are performed for 15-30min to obtain a molten liquid;

[0034] (2) A protective gas is filled into the crucible so that the pressure inside the crucible is greater than the pressure inside the cavity and the pressure difference is 10-50 kPa, so that the molten liquid is squeezed out of the microporous sheet under the action of the pressure difference and gravity, and then cooled to obtain a metal wire.

[0035] In a second aspect, the present invention provides a metal wire material for low-temperature refrigeration, wherein the metal wire material for low-temperature refrigeration is obtained by the preparation method of the metal wire material for low-temperature refrigeration according to the first aspect of the present invention.

[0036] The metal wire material for low-temperature refrigeration provided by the present invention has high continuity, a smooth surface, uniform composition, fine grain structure, high mechanical strength and good plasticity and toughness.

[0037] Preferably, the diameter of the metal wire is 0.15-0.25 mm, for example, it can be 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.20 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm or 0.25 mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] In a third aspect, the present invention provides a use of the metal wire material for low-temperature refrigeration as described in the second aspect of the present invention, wherein the metal wire material for low-temperature refrigeration is used as a cold storage material for a refrigerator.

[0039] The metal wire material for low-temperature refrigeration provided by the present invention has a regular shape and an adjustable diameter, can ensure a high filling rate, reduce the flow resistance of the refrigerant in the cold storage device, and has good application prospects in the field of low-temperature refrigeration.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The preparation method provided by the present invention is aimed at the problem of poor mechanical properties of metals used for low-temperature refrigeration. It breaks through the conventional plastic processing ideas such as extrusion, drawing or rolling, and uses pressure difference and gravity to directly spray from liquid melt to prepare metal wire. The diameter of the wire can be conveniently adjusted by regulating the pressure difference, heating power and the diameter of the through hole in the microporous sheet. Rapid outflow and cooling can make the composition of the product uniform, obtain a fine-grained structure, and make the product have higher mechanical strength and better plastic toughness.

[0042] (2) The metal wire material for low-temperature refrigeration provided by the present invention has a regular shape and an adjustable diameter, which can ensure a high filling rate and reduce the flow resistance of the refrigerant in the cold storage device, and has good application prospects in the field of low-temperature refrigeration. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of the structure of the device used in the preparation method provided in Example 1 of the present invention;

[0044] Among them, 1-crucible; 2-sealing cover; 3-microporous sheet; 4-cavity; 5-pressure gauge; 6-induction heating component; 7-pressure difference control component; 8-vacuuming component; 9-collecting component; 10-gas distribution component;

[0045] Figure 2 The XRD pattern of the metal wire obtained by the preparation method provided in Example 1 of the present invention;

[0046] Figure 3 This is an optical micrograph of the metal wire obtained by the preparation method provided in Example 1 of the present invention;

[0047] Figure 4 This is an optical micrograph of the metal wire obtained by the preparation method provided in Example 2 of the present invention;

[0048] Figure 5 This is an optical micrograph of the metal wire obtained by the preparation method provided in Example 3 of the present invention;

[0049] Figure 6 This is an optical micrograph of the product obtained by the preparation method provided in Example 4 of the present invention;

[0050] Figure 7 This is a photo of the product obtained by the preparation method provided in Example 5 of the present invention;

[0051] Figure 8 This is an optical micrograph of the product obtained by the preparation method provided in Example 6 of the present invention;

[0052] Fig. 9 This is an optical micrograph of the product obtained by the preparation method provided in Example 7 of the present invention;

[0053] Fig.10 This is a photo of the product obtained by the preparation method provided in Example 8 of the present invention. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0055] In a specific embodiment, the device used in the method for preparing the metal wire for low-temperature refrigeration provided by the present invention is as follows Figure 1 As shown, the device comprises a crucible 1, a sealing cover 2 is arranged above the crucible 1 for sealing the crucible 1, a microporous sheet 3 is arranged at the bottom of the crucible 1, a circular through hole is arranged in the middle of the microporous sheet 3 for allowing the molten liquid to flow out of the through hole to prepare the wire material, an induction heating component 6 is arranged outside the crucible 1 for heating the metal raw material in the crucible 1, the crucible 1 is arranged in a sealed cavity 4, a pressure gauge 5 is arranged on the cavity 4 for testing the pressure in the cavity 4, a vacuum assembly 8, a pressure difference control assembly 7 and a gas distribution assembly 10 are arranged on the cavity 4, and the vacuum assembly 8, the pressure difference control assembly 7 and the gas distribution assembly 10 are arranged on the cavity 4. The vacuum component 8 is used to evacuate the cavity 4, the pressure difference control component 7 is used to inject protective gas into the crucible 1 to control the pressure difference between the cavity 4 and the crucible 1, the gas distribution component 10 is used to inject protective gas into the cavity 4, and a collecting component 9 is provided at the bottom of the crucible 1 for collecting the prepared wire material. The induction heating component 6 and the cavity 4 can be cooled by a water cooler (not shown in the figure). The material of the crucible 1, the sealing cover 2 and the microporous sheet 3 can be any one of boron nitride, alumina, quartz or graphite, or a combination of at least two of them.

[0056] In the following examples, Bruker D8 Advance was used to test the X-ray diffraction patterns of the products;

[0057] In the following examples, an MIT 500 optical microscope produced by Ott Optics was used to test the optical microstructure of the product.

[0058] Example 1

[0059] This embodiment provides a method for preparing a metal wire for low-temperature refrigeration. The device used in the preparation method is as follows: Figure 1 As shown, it includes a crucible 1, a sealing cover 2, a microporous sheet 3, a cavity 4, a pressure gauge 5, an induction heating component 6, a pressure difference control component 7, a vacuum component 8, a collection component 9 and a gas distribution component 10. The preparation method includes the following steps:

[0060] (1) Pb, Sb, Ag, Cu and Te and other metal raw materials are polished to remove the oxide scale and impurities on the surface, Pb954g, Sb 42.5g, Ag 2.5g, Cu 0.5g and Te 0.5g are placed in a crucible 1 and sealed by a sealing cover 2, the purity of the metal raw materials is ≥99.9wt.%, a quartz microporous sheet 3 is provided at the bottom of the crucible 1, and a through hole with a diameter of 0.1mm is provided in the microporous sheet 3, the crucible 1 is placed in a cavity 4, and then the cavity 4 is evacuated by a vacuum pumping component 8 to an end vacuum degree of 5Pa, and then argon is filled into the cavity 4 by a gas distribution component 10 until the pressure in the cavity 4 is equal to the external atmospheric pressure, that is, the pressure gauge 5 displays "0", the induction heating component 6 is turned on to control the heating power to 1.0kW to perform induction heating on the crucible 1 to melt the metal raw materials, and then the crucible is kept warm and refined for 20min to obtain a molten liquid;

[0061] (2) Argon gas is filled into the crucible 1 through the pressure difference control component 7, so that the pressure in the crucible 1 is greater than the pressure in the cavity 4 and the pressure difference is 30 kPa, so that the molten liquid is squeezed out of the microporous sheet 3 under the action of the pressure difference and gravity, and then cooled to obtain a continuous, smooth-surfaced, uniform-diameter metal wire with a diameter of 0.15 mm and collected by the collecting component 9.

[0062] Taking Example 1 as an example, the XRD spectrum of the metal wire obtained in this example is tested. Figure 2 As shown, from Figure 2 The characteristic peaks of Pb and the weak characteristic peaks of Sb can be seen, while Ag, Cu and Te do not show their characteristic peaks due to trace addition.

[0063] The optical micrograph of the metal wire obtained in this embodiment is as follows: Figure 3 As shown, from Figure 3 It can be seen that the obtained metal wire is continuous, uniform in diameter and has a smooth surface.

[0064] Example 2

[0065] This embodiment provides a method for preparing a metal wire for low-temperature refrigeration. The device used in the preparation method is the same as that in Example 1. The preparation method comprises the following steps:

[0066] (1) Metal raw materials such as Bi and Sb are polished to remove oxide scale and impurities on the surface, 950 g of Bi and 50 g of Sb are placed in a crucible and sealed with a sealing cover, the purity of the metal raw materials is ≥99.9 wt.%, a microporous sheet made of boron nitride is provided at the bottom of the crucible, and a through hole with a diameter of 0.15 mm is provided in the microporous sheet, the crucible is placed in a cavity, and then the cavity is evacuated by a vacuum pumping component to a terminal vacuum degree of 4 Pa, and then nitrogen is filled into the cavity by a gas distribution component until the pressure in the cavity is equal to the external atmospheric pressure, that is, the pressure gauge displays "0", the induction heating component is turned on to control the heating power to 2.0 kW to perform induction heating on the crucible to melt the metal raw materials, and then the crucible is kept warm and refined for 15 minutes to obtain a molten liquid;

[0067] (2) nitrogen is filled into the crucible through the pressure difference control component, so that the pressure in the crucible is greater than the pressure in the cavity and the pressure difference is 10 kPa, so that the molten liquid is squeezed out of the microporous sheet under the action of the pressure difference and gravity, and then cooled to obtain a continuous, smooth-surfaced, 0.25 mm diameter metal wire of equal diameter, which is collected by the collecting component.

[0068] The optical micrograph of the metal wire obtained in this embodiment is as follows: Figure 4 As shown, from Figure 4 It can be seen that the obtained metal wire is continuous, uniform in diameter and has a smooth surface.

[0069] Example 3

[0070] This embodiment provides a method for preparing a metal wire for low-temperature refrigeration. The device used in the preparation method is the same as that in Example 1. The preparation method comprises the following steps:

[0071] (1) Grinding the metal raw material Sn to remove the oxide scale and impurities on the surface, placing 1000 g of Sn into a crucible and sealing it with a sealing cover, wherein the purity of the metal raw material is ≥99.9 wt.%, and the bottom of the crucible is provided with a microporous sheet made of alumina, and a through hole with a diameter of 0.2 mm is provided in the microporous sheet, and the crucible is placed in a cavity, and then the cavity is evacuated by a vacuum pumping component to a terminal vacuum degree of 3 Pa, and then argon is filled into the cavity by a gas distribution component until the pressure in the cavity is equal to the external atmospheric pressure, that is, the pressure gauge displays "0", and the induction heating component is turned on to control the heating power to 1.2 kW to perform induction heating on the crucible to melt the metal raw material, and then the crucible is kept warm and refined for 30 minutes to obtain a molten liquid;

[0072] (2) Argon gas is filled into the crucible through the pressure difference control component, so that the pressure in the crucible is greater than the pressure in the cavity and the pressure difference is 50 kPa, so that the molten liquid is squeezed out of the microporous sheet under the action of pressure difference and gravity, and then cooled to obtain a continuous, smooth-surfaced, 0.20 mm diameter metal wire of equal diameter, which is collected by the collection component.

[0073] The optical micrograph of the metal wire obtained in this embodiment is as follows: Figure 5 As shown, from Figure 5 It can be seen that the obtained metal wire is continuous, uniform in diameter, smooth in surface and slightly oxidized.

[0074] Example 4

[0075] This embodiment provides a method for preparing a metal wire for low-temperature refrigeration, which is different from the method in Embodiment 1 only in that the heating power is 0.8 kW.

[0076] The optical micrograph of the product obtained in this example is as follows Figure 6 As shown, from Figure 6 It can be seen that the obtained product is a dumbbell-shaped wire.

[0077] Example 5

[0078] This embodiment provides a method for preparing a metal wire for low-temperature refrigeration, which is different from the method in Embodiment 1 only in that the heating power is 3.0 kW.

[0079] The product obtained in this example is too large to be tested with an optical microscope. Figure 7 As shown, from Figure 7 It can be seen that the obtained product is in a lump-like form.

[0080] Example 6

[0081] This embodiment provides a method for preparing a metal wire for low-temperature refrigeration, which is different from the method in Embodiment 1 only in that the diameter of the through hole is 0.3 mm.

[0082] The optical micrograph of the product obtained in this example is as follows Figure 8 As shown, from Figure 8 It can be seen that the obtained product is a spherical object with a larger particle size and a poor surface condition.

[0083] Example 7

[0084] This embodiment provides a method for preparing a metal wire for low-temperature refrigeration, which is different from the method in Embodiment 1 only in that the pressure difference is 5 kPa.

[0085] The optical micrograph of the product obtained in this example is as follows Fig. 9 As shown, from Fig. 9 It can be seen that the obtained product is spherical with dispersed size.

[0086] Example 8

[0087] This embodiment provides a method for preparing a metal wire for low-temperature refrigeration, which is different from the method in Embodiment 1 only in that the pressure difference is 53 kPa.

[0088] The product obtained in this example is too large to be tested with an optical microscope. Fig.10 As shown, from Fig.10 It can be seen that the obtained product is in the form of discs.

[0089] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a metal wire for low-temperature refrigeration, characterized in that: The preparation method comprises the following steps: (1) placing a metal raw material into a crucible and sealing it, with a microporous sheet disposed at the bottom of the crucible, heating the crucible under a protective atmosphere by controlling the heating power to melt the metal raw material, and then performing heat preservation and refining to obtain a molten liquid; (2) A protective gas is filled into the crucible to make the pressure inside the crucible greater than the external pressure, so that the molten liquid is squeezed out of the microporous sheet under the action of pressure difference and gravity, and then cooled to obtain a metal wire.

2. The preparation method according to claim 1, characterized in that: The metal raw material in step (1) contains any one of Pb, Bi or Sn or a combination of at least two thereof; Preferably, the purity of the metal raw material is ≥99.9wt.%; Preferably, the metal raw material is polished to remove oxide scale and impurities on the surface before being placed in the crucible.

3. The preparation method according to claim 1 or 2, characterized in that: The crucible in step (1) is placed in a cavity for heating; Preferably, the cavity is evacuated and filled with protective gas in sequence before heating; Preferably, the vacuum degree at the end of the vacuuming is ≤5Pa; Preferably, the protective gas comprises nitrogen and / or an inert gas; Preferably, the inert gas comprises argon; Preferably, the protective gas is filled into the cavity until the pressure is equal to the external atmospheric pressure.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The heating power in step (1) is 1.0-2.0 kW; Preferably, the heating method includes induction heating.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The time of heat preservation and refining in step (1) is 15-30 minutes.

6. The preparation method according to any one of claims 1 to 5, characterized in that: Step (1) The microporous sheet is provided with through holes; Preferably, the diameter of the through hole is 0.1-0.2 mm.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The pressure difference in step (2) is 10-50 kPa.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) grinding a metal raw material to remove oxide scale and impurities on the surface, placing it in a crucible and sealing it, wherein the metal raw material contains any one of Pb, Bi or Sn or a combination of at least two of them, and the purity of the metal raw material is ≥99.9wt.%, a microporous sheet is arranged at the bottom of the crucible, and a through hole with a diameter of 0.1-0.2mm is arranged in the microporous sheet, the crucible is placed in a cavity, and then the cavity is evacuated to an end vacuum degree of ≤5Pa, and then a protective gas is filled until the pressure in the cavity is equal to the external atmospheric pressure, and the heating power is controlled to be 1.0-2.0kW to perform induction heating on the crucible to melt the metal raw material, and then heat preservation and refining are performed for 15-30min to obtain a molten liquid; (2) A protective gas is filled into the crucible so that the pressure inside the crucible is greater than the pressure inside the cavity and the pressure difference is 10-50 kPa, so that the molten liquid is squeezed out of the microporous sheet under the action of the pressure difference and gravity, and then cooled to obtain a metal wire.

9. A metal wire material for low temperature refrigeration, characterized in that: The metal wire material for low-temperature refrigeration is obtained by the preparation method of the metal wire material for low-temperature refrigeration according to any one of claims 1 to 8.

10. A use of the metal wire material for low temperature refrigeration as claimed in claim 9, characterized in that: The metal wire material for low-temperature refrigeration is used as a cold storage material for a refrigerator.

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