Preparation method of porous metal long and thin tube

Abstract

The invention discloses a preparation method of a porous metal long and thin tube, which comprises the following steps: dissolving metal powder and an organic high-molecular polymer in a solvent according to a certain proportion, mixing to form bubble-free and uniform slurry with certain viscosity, extruding from a mold under the driving of certain power by adopting an extrusion-immersion molding technology based on the principle of a phase inversion method, and carrying out extrusion molding to obtain the porous metal long and thin tube. And immersing into the exchange liquid, curing, winding by using a winding wheel, and collecting in a roll to obtain the required blank. The long-chain interaction force between high-molecular organic matters is utilized, a blank body has high obdurability, during sintering, a sectional sintering mode is adopted, the blank body is placed in a material boat and coiled into a spiral shape, and the porous metal thin tube with the high length-diameter ratio can be obtained through straightening after sintering is completed. The outer diameter of the porous metal long and thin tube prepared by the method is 1-10mm, the wall thickness is 1-3mm, the length of a finished product can reach more than 2m, the average pore diameter is 0.1-10mu m, and the relative air permeability can reach more than 100m < 3 > / (h.KPa.m < 2 >).

Description

Technical Field

[0001] The invention relates to the technical field of powder metallurgy, and in particular to a method for preparing a porous metal long and thin tube. Background Art

[0002] Powder metallurgy porous metal materials have the characteristics of low density, large specific surface area, high specific strength, corrosion resistance, etc., and have many advantages that traditional dense metals cannot match. In recent years, they have attracted much attention and have great application prospects. They are widely used in the fields of aerospace industry, biomedicine, filtration separation, catalysts, battery electrodes, sound absorption and noise reduction, and heat exchange. In recent years, with the rapid development of fine chemicals, semiconductors, and new energy industries, higher requirements have been put forward for metal porous tubes, hoping that they have low permeability resistance, high specific surface area, high packing density, micron to submicron pore size, millimeter outer diameter size, and high aspect ratio.

[0003] The preparation technologies of porous metal materials usually include powder rolling, isostatic pressing, injection molding technology, extrusion technology, etc. Powder rolling is suitable for manufacturing metal sheets, strips, and pipes, especially porous thin strips with high porosity. When producing pipes using powder rolling technology, porous green strips are generally rolled out, and pipe production is achieved through multiple processes such as sintering, curling and welding. This method is suitable for the production of pipes with large diameters and wall thicknesses, and the dimensional accuracy of the production is poor. Isostatic pressing technology is suitable for the production of pipes with larger outer diameters. Its disadvantages are low production efficiency, the size of the pressed blank is limited by the pressure vessel, the surface quality of the blank is poor, and secondary processing is required to achieve the required accuracy. In addition, the wall thickness of the blank produced by this method cannot be too thin, otherwise it is easy to break and shatter during demolding, which seriously affects the yield rate. Injection molding technology uses a large amount of binder, and the pipe will shrink during sintering, and the accuracy of the obtained metal pipe is difficult to control.

[0004] Patent application number 202410783811.7 proposes a method for developing sintered ultrafine metal porous metal tubes using extrusion immersion molding technology. The tube length prepared by this method can reach more than 1m, the average pore size is 0.1-10μm, and the relative permeability can reach 100m 3 / (h·KPa·m 2 ) or more. However, the length of the porous metal tube prepared by the above method is still limited, it is difficult to ensure the formability and integrity of the blank during the preparation process, the preparation process is complicated, the cost is increased, etc. Summary of the invention

[0005] The present invention provides a method for preparing a porous metal long thin tube, aiming to solve the problems existing in the background technology, such as limited length size, difficulty in ensuring the integrity and formability of the blank, complex preparation process, high cost, etc.

[0006] The technical solution provided by the present invention is as follows:

[0007] A method for preparing a porous metal long thin tube comprises the following steps:

[0008] Dissolving an organic high molecular polymer in a solvent to prepare a homogeneous solution with a mass percentage concentration of 5 to 30%;

[0009] The metal powder or alloy powder is mixed with the homogeneous solution in a mass ratio of (1-5):1 to obtain a slurry;

[0010] Extruding the slurry into the exchange liquid through a die to obtain a green body;

[0011] The completely solidified green body is transferred to a winding wheel, and is wound by the winding wheel and collected into a roll;

[0012] The collected green body is coiled into a spiral shape and then sintered by a staged sintering method. The first stage is a degreasing stage, with a heating rate of ≤5°C / min and a holding time of 90 to 180 minutes. The second stage is a sintering molding stage, with a heating rate of ≤10°C / min and a holding time of 120 to 200 minutes. After sintering, straightening is performed to obtain the porous metal long thin tube.

[0013] Furthermore, the metal powder or alloy powder is one of stainless steel metal powder, tungsten powder, nickel powder, titanium powder, copper powder, iron-chromium-aluminum alloy powder, iron-chromium-nickel alloy powder, iron-aluminum alloy powder, Hastelloy powder, and monel alloy powder.

[0014] Furthermore, the organic high molecular polymer is one of polyacrylonitrile, polyethersulfone, polysulfone, polyvinylidene fluoride, cellulose, and polyvinylidene fluoride with a molecular weight greater than 30,000;

[0015] The solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone or a mixture of two or more thereof.

[0016] Furthermore, the exchange liquid is one or a mixture of ethanol, propanol, ethylene glycol, glycerol, glucose aqueous solution or pure water.

[0017] Furthermore, the slurry is mixed uniformly by one or more methods selected from the group consisting of mechanical stirring, ball milling, and ultrasonic high-frequency oscillation;

[0018] The mixed slurry is degassed by a vacuum degassing device, the degassing temperature is 10 to 40°C, the vacuum degree is -0.1 to -0.99 MPa, and the degassing time is 10 to 35 minutes;

[0019] The viscosity of the slurry is 2000-100000 mPa·s.

[0020] Furthermore, the slurry is extruded through the die at a speed of 0.5 to 1000 ml / min, and the extrusion power is one or a combination of air pressure, air pressure piston, gear pump, and injection pump;

[0021] The blank is transferred to the winding wheel by a transmission roller, the transfer speed is 0.5-5 m / min, the outer diameter of the winding wheel is 1-3 m, and the linear speed is 3-40 m / min.

[0022] Furthermore, the outer diameter of the porous metal long thin tube is 1 to 10 mm, the wall thickness is 1 to 3 mm, the average pore size is 0.1 to 10 μm, and the relative air permeability reaches 100 m 3 / (h·KPa·m 2 ).

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention utilizes the long-chain intermolecular forces of high molecular organic polymers to ensure that the length and size range of the blank in the molding stage is not limited; in addition, a degassing process is added in the molding stage, which can effectively avoid the defects that may occur in the blank during molding, ensure the integrity of the molding stage, and is suitable for the preparation of porous metal long thin tubes of 2 meters and above;

[0025] 2. The present invention adjusts the ratio of high molecular organic polymer and metal powder, and this ratio is more suitable for the molding of porous metal tubes with a small outer diameter size range;

[0026] 3. In the sintering stage, the present invention uses a more detailed temperature rise program to effectively control the shrinkage of the green body, so that when the green body is coiled into a spiral shape, there will be no defects at the place with a larger curvature, thus ensuring the integrity of the sintering stage;

[0027] 4. The present invention is simple to operate, has a wide range of applications, and has high practical value. It can be extended to the forming of porous metal tubes with smaller outer diameters, and is particularly suitable for preparing porous metal tubes with a high aspect ratio;

[0028] 5. By using the method provided by the present invention, the length of the tube can be adjusted arbitrarily according to the demand. The porous metal long and thin tube prepared by the present invention has an outer diameter of 1 to 10 mm, a wall thickness of 1 to 3 mm, a finished product length of more than 2 m, an average pore diameter of 0.1 to 10 μm, and a relative air permeability of up to 100 m 3 / (h·KPa·m 2 );

[0029] 6. The porous metal long and thin tubes prepared by the present invention have small pore size, uniform air permeability, high strength and toughness, excellent corrosion resistance, and a wide range of applications. They can be used in the aerospace industry, biomedicine, filtration separation, catalysts, battery electrodes, sound absorption and noise reduction, heat exchange and other fields of filtration, separation, purification, flow control and other technical fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic flow chart of a method for preparing a porous metal long thin tube provided by the present invention;

[0031] Figure 2 A schematic diagram of a winding wheel for the porous metal long thin tube blank provided by the present invention.

[0032] The reference numerals are as follows:

[0033] 1-concentric double-channel extrusion die; 2-exchange liquid; 3-winding wheel. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the embodiments described below are part of the embodiments of the present application, not all of the embodiments.

[0035] like Figure 1 As shown, the present invention provides a method for preparing a porous metal long thin tube, comprising the following steps:

[0036] Step S1, dissolving an organic high molecular polymer in a solvent to prepare a homogeneous solution with a mass percent concentration of 5 to 30%.

[0037] The organic high molecular polymer is one of polyacrylonitrile, polyethersulfone, polysulfone, polyvinylidene fluoride, cellulose and polyvinylidene fluoride with a molecular weight greater than 30,000.

[0038] The solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone or a mixture of two or more thereof.

[0039] Step S2, mixing the metal powder or alloy powder and the homogeneous solution in a mass ratio of (1-5):1 to obtain a slurry.

[0040] The metal powder or alloy powder is one of stainless steel metal powder, tungsten powder, nickel powder, titanium powder, copper powder, iron-chromium-aluminum alloy powder, iron-chromium-nickel alloy powder, iron-aluminum alloy powder, Hastelloy powder, and monel alloy powder. The material of the stainless steel metal powder can be: 310, 310s, 304, 304L, 316, 316L, etc.

[0041] Step S3: Extruding the slurry into the exchange liquid through a mold to obtain a green body.

[0042] The exchange liquid is one or a mixture of ethanol, propanol, ethylene glycol, glycerol, glucose aqueous solution or pure water.

[0043] Step S4: convey the completely solidified green body to the winding wheel, and use the winding wheel to wind it and collect it into a roll.

[0044] Step S5, coiling the collected green body into a spiral shape and then sintering it by a staged sintering method, the first stage is a degreasing stage, the heating rate is ≤5°C / min, and the insulation time is 90-180min; the second stage is a sintering molding stage, the sintering temperature is 0.5-0.9 times the melting point of the metal powder or alloy powder, the heating rate is ≤10°C / min, and the insulation time is 120-200min. After sintering is completed, straightening is performed to obtain a porous metal long thin tube.

[0045] Figure 2 This is a schematic diagram of the operation of step 3 and step 4, wherein 1 is a concentric double-channel extrusion die, 2 is an exchange liquid, and 3 is a winding wheel.

[0046] In step S2, the slurry is mixed uniformly by one or more methods selected from the group consisting of mechanical stirring, ball milling, and ultrasonic high-frequency oscillation, and the viscosity of the slurry is 2000 to 100000 mPa·s.

[0047] The uniformly mixed slurry is degassed by a vacuum degassing device, the temperature during degassing is 10-40°C, the vacuum degree is -0.1-0.99MPa, and the degassing time is 10-35min. Compared with the traditional preparation process, the present invention adds a degassing process, which can effectively avoid defects that may occur in the blank during molding, ensure the integrity of the molding stage, and is suitable for the preparation of porous metal long thin tubes of 2 meters and above.

[0048] Optionally, the slurry is extruded through the die at a speed of 0.5 to 1000 ml / min, and the extrusion power is one or a combination of air pressure, air pressure piston, gear pump, and injection pump.

[0049] The blank is transferred to the winding wheel by a transmission roller, the transfer speed is 0.5-5 m / min, the outer diameter of the winding wheel is 1-3 m, and the line speed is 3-40 m / min.

[0050] Optionally, the outer diameter of the prepared porous metal long thin tube is 1 to 10 mm, the wall thickness is 1 to 3 mm, the finished product length can reach more than 2 m, the average pore diameter is 0.1 to 10 μm, and the relative air permeability can reach 100 m 3 / (h·KPa·m 2 )above.

[0051] The porous metal long thin tube and the preparation method thereof provided by the present invention are further illustrated and described below in conjunction with embodiments.

[0052] Example 1

[0053] Polyacrylonitrile with a molecular weight of 50,000 was dissolved in N-methylpyrrolidone to prepare a homogeneous solution with a mass percentage concentration of 23%. Stainless steel powder with an average particle size of 10 μm and the homogeneous solution were added in batches at a mass ratio of 2:1. A vacuum degassing device was used for degassing. The degassing temperature was 40°C, the vacuum degree was -0.99 MPa, the degassing time was 35 min, and the slurry viscosity was 35000 mPa·s. The extrusion immersion molding technology is adopted. Under the drive of the injection pump, the slurry is extruded from the mold at a speed of 20 ml / min. The exchange liquid is ethanol. The fully solidified green body is sent to the winding wheel at a uniform speed using a transmission roller, and is wound on the winding wheel and collected in a roll. The transmission wheel speed is 3 m / min, the outer diameter of the winding wheel is 3 m, and the line speed is 10 m / min. After the green body is washed, it is sintered. The green body is coiled into a spiral shape and placed in a material boat. A segmented sintering method is used. In the first stage, the temperature is increased from room temperature to 600°C and kept for 180 minutes. The heating rate is 2°C / min. In the second stage, the temperature is increased from 600°C to 1100°C and kept for 200 minutes. The heating rate is 10°C / min. After sintering, it is straightened to obtain a finished porous metal slender tube.

[0054] The porous metal long thin tube prepared by the above method is characterized by an outer diameter of 2±0.05mm, a wall thickness of 0.6±0.03mm, a finished product length of more than 5m, an average pore diameter of 10μm, and a relative air permeability of up to 100m 3 / (h·KPa·m 2 )above.

[0055] Implementation Case 2

[0056] Polyacrylonitrile with a molecular weight of 80,000 was dissolved in N-methylpyrrolidone to prepare a homogeneous solution with a mass percentage concentration of 30%. Tungsten powder with an average particle size of 3 μm and the homogeneous solution were added in batches at a mass ratio of 2:1. A vacuum degassing device was used for degassing. The degassing temperature was 20°C, the vacuum degree was -0.97 MPa, the degassing time was 35 min, and the slurry viscosity was 50000 mPa·s. The extrusion immersion molding technology is adopted. Under the drive of the injection pump, the slurry is extruded from the mold, the extrusion speed is 15ml / min, the exchange liquid is 75wt.% ethanol aqueous solution, the fully solidified green body is sent to the winding wheel at a uniform speed by a transmission roller, and is wound by the winding wheel and collected in a roll. The transmission wheel speed is 3m / min, the outer diameter of the winding wheel is 3m, and the line speed is 15m / min. After the green body is washed, it is sintered, and the obtained green body is coiled into a spiral shape and placed in a material boat. A segmented sintering method is used. In the first stage, the temperature is increased from room temperature to 600℃ and kept warm for 180min, and the heating rate is 1℃ / min. In the second stage, the temperature is increased from 600℃ to 1250℃ and kept warm for 200min, and the heating rate is 5℃ / min. After sintering, it is straightened to obtain a finished porous metal slender tube.

[0057] The porous metal long thin tube prepared by the above method is characterized by an outer diameter of 1.8±0.05mm, a wall thickness of 0.6±0.03mm, a finished product length of more than 5m, an average pore diameter of 10μm, and a relative air permeability of up to 120m 3 / (h·KPa·m 2 )above.

[0058] Example 3

[0059] Polyacrylonitrile with a molecular weight of 80,000 was dissolved in N-methylpyrrolidone to prepare a homogeneous solution with a mass percentage concentration of 30%. Nickel powder with an average particle size of 6 μm and the homogeneous solution were added in batches at a mass ratio of 2:1. A vacuum degassing device was used for degassing. The degassing temperature was 30°C, the vacuum degree was -0.98 MPa, the degassing time was 35 min, and the slurry viscosity was 50000 mPa·s. The extrusion immersion molding technology is adopted. Under the drive of the injection pump, the slurry is extruded from the mold, the extrusion speed is 10ml / min, the exchange liquid is 50wt.% ethanol aqueous solution, the fully solidified green body is sent to the winding wheel at a uniform speed by a transmission roller, and is wound by the winding wheel and collected into rolls. The transmission wheel speed is 1m / min, the outer diameter of the winding wheel is 1m, and the line speed is 15m / min. After the green body is washed, it is sintered, and the obtained green body is coiled into a spiral shape and placed in a material boat. A segmented sintering method is used. The first stage is the degreasing stage, the heating rate is 2℃ / min, and the insulation time is 120min; the second stage is the sintering molding stage, the heating rate is 5℃ / min, and the insulation time is 120min. After sintering, it is straightened to obtain a porous metal slender tube product.

[0060] The porous metal long thin tube prepared by the above method is characterized by an outer diameter of 1.8±0.05mm, a wall thickness of 0.6±0.03mm, a finished product length of more than 5m, an average pore diameter of 10μm, and a relative air permeability of up to 120m 3 / (h·KPa·m 2 )above.

[0061] By adopting the method provided by the present invention, the length of the tube can be adjusted arbitrarily according to the demand. The porous metal long thin tube prepared by the present invention has an outer diameter of 1 to 10 mm, a wall thickness of 1 to 3 mm, a finished product length of more than 2 m, an average pore diameter of 0.1 to 10 μm, and a relative air permeability of up to 100 m 3 / (h·KPa·m 2 The porous metal long thin tube prepared by the present invention has small pore size, uniform air permeability, high strength and toughness, excellent corrosion resistance, and a wide range of applications, and can be used in the fields of filtration, separation, purification, flow control, etc. in the fields of aerospace industry, biomedicine, filtration separation, catalysts, battery electrodes, sound absorption and noise reduction, and heat exchange.

[0062] The above is only the best specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application shall be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for preparing a porous metal long thin tube, characterized in that: The following steps are involved: Dissolving an organic high molecular polymer in a solvent to prepare a homogeneous solution with a mass percentage concentration of 5 to 30%; The metal powder or alloy powder is mixed with the homogeneous solution in a mass ratio of (1-5):1 to obtain a slurry; Extruding the slurry into the exchange liquid through a die to obtain a green body; The completely solidified green body is transferred to a winding wheel, and is wound by the winding wheel and collected into a roll; The collected green body is coiled into a spiral shape and then sintered by a staged sintering method. The first stage is a degreasing stage, with a heating rate of ≤5°C / min and a holding time of 90 to 180 minutes. The second stage is a sintering molding stage, with a heating rate of ≤10°C / min and a holding time of 120 to 200 minutes. After sintering, straightening is performed to obtain the porous metal long thin tube.

2. The method for preparing the porous metal long thin tube according to claim 1, characterized in that: The metal powder or alloy powder is one of stainless steel metal powder, tungsten powder, nickel powder, titanium powder, copper powder, iron-chromium-aluminum alloy powder, iron-chromium-nickel alloy powder, iron-aluminum alloy powder, Hastelloy powder, and monel alloy powder.

3. The method for preparing the porous metal long thin tube according to claim 1, characterized in that: The organic high molecular polymer is one of polyacrylonitrile, polyethersulfone, polysulfone, polyvinylidene fluoride, cellulose and polyvinylidene fluoride with a molecular weight greater than 30,000; The solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone or a mixture of two or more thereof.

4. The method for preparing the porous metal long thin tube according to claim 1, characterized in that: The exchange liquid is one or a mixture of ethanol, propanol, ethylene glycol, glycerol, glucose aqueous solution or pure water.

5. The method for preparing a porous metal long thin tube according to any one of claims 1 to 4, characterized in that: The slurry is mixed uniformly by one or more methods including mechanical stirring, ball milling, and ultrasonic high-frequency oscillation; The mixed slurry is degassed by a vacuum degassing device, the degassing temperature is 10 to 40°C, the vacuum degree is -0.1 to -0.99 MPa, and the degassing time is 10 to 35 minutes; The viscosity of the slurry is 2000-100000 mPa·s.

6. The method for preparing the porous metal long thin tube according to claim 5, characterized in that: The slurry is extruded through the die at a speed of 0.5 to 1000 ml / min, and the extrusion power is one or a combination of air pressure, air pressure piston, gear pump, and injection pump; The blank is transferred to the winding wheel by a transmission roller, the transfer speed is 0.5-5 m / min, the outer diameter of the winding wheel is 1-3 m, and the linear speed is 3-40 m / min.

7. The method for preparing the porous metal long thin tube according to claim 6, characterized in that: The outer diameter of the porous metal long thin tube is 1 to 10 mm, the wall thickness is 1 to 3 mm, the average pore size is 0.1 to 10 μm, and the relative air permeability reaches 100 m 3 / (h·KPa·m 2 ).

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