A method for preparing high-strength and high-conductivity powder metallurgy copper-iron alloy from copper-coated iron powder

Abstract

The present invention relates to a method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy using copper-clad iron powder, belonging to the technical field of electrochemistry and powder metallurgy materials. The method comprises the following steps: S1, iron powder pickling and activation; S2, copper source solution preparation; S3, powder-liquid mixing and replacement; S4, two-stage reduction; S5, powder raw material mixing; S6, raw material pressing and forming; S7, sintering and densification; S8, deformation processing; and S9, high-temperature heat treatment. The method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy using copper-clad iron powder has a uniform structure and good density of the copper-clad iron composite powder coating layer prepared. Compared with the displacement copper plating method, a large amount of loose copper blocks with heterogeneous distribution are not present on the surface. Furthermore, the prepared copper-iron alloy ingot has a low oxygen content, high sintering density, uniform composition without segregation, fine grain size, excellent processing performance, and a small amount of residual solid-solution iron atoms in the copper. It has both high strength and high conductivity and has important application prospects in key components in the fields of electronic information, aerospace, electromagnetic shielding, etc.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemistry and powder metallurgy materials, and in particular to a method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from copper-coated iron powder. Background Art

[0002] With the rapid development of electronic communications, rail transportation and the automotive industry, higher requirements are placed on the strength and electrical conductivity of materials. Copper-iron alloys have become ideal high-strength and high-conductivity materials due to their abundant raw materials, low cost, huge magnetoresistance effect and special physical properties. Copper-coated iron powder is a composite powder formed by uniformly coating copper on the surface of iron powder. The copper-iron alloy prepared using this powder through powder metallurgy technology combines the high electrical and thermal conductivity and good plasticity of copper with the high strength, wear resistance and magnetism of iron.

[0003] Chinese patent CN114293045B discloses a method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy. The above application mixes atomized copper-iron alloy powder and copper-phosphorus alloy powder, and prepares the copper-iron alloy in the form of plates, strips, and rods through cold isostatic pressing, vacuum sintering, and subsequent deformation processing. This provides a method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy with low oxygen content, fine grains, fine and uniformly distributed iron phase, and good processing performance. This method solves the problems of component segregation, coarse grains, and poor processing performance of copper-iron alloys prepared by traditional smelting methods, as well as high oxygen content, high sintering temperature, and difficulty in precipitation of solid-solution iron phase in traditional powder metallurgy copper-iron alloys. Problem: Although the above application improves the performance of copper-iron alloy by adding phosphorus, it mainly relies on traditional powder metallurgy process and does not optimize the surface coating of copper-iron powder. During the sintering process, the mixed powder of copper and iron may have composition segregation, resulting in uneven organization and uneven distribution of iron phase, thereby affecting the overall performance of the alloy. Secondly, although pure titanium powder is used as an oxygen absorber during vacuum sintering, the control effect of oxygen content is not clearly pointed out. Moreover, in traditional powder metallurgy process, high oxygen content is a common problem. High oxygen content will reduce the conductivity and mechanical properties of the alloy. Therefore, the above has certain limitations. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a method for preparing high-strength and high-conductivity powder metallurgy copper-iron alloy from copper-clad iron powder. The method has the advantages of uniform structure and good density of the copper-clad iron composite powder coating layer, and solves the problems of uneven structure and composition segregation of copper-iron mixed powder in traditional powder metallurgy.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from copper-clad iron powder, comprising the following steps:

[0006] S1 Iron powder acid washing and activation: The carbonyl iron powder is placed in an acid solution for cleaning, and a small amount of dispersant and corrosion inhibitor is added at the same time. Then, it is washed with deionized water, filtered and dried to obtain the activated carbonyl iron powder;

[0007] Preparation of S2 copper source solution: fully dissolve water-soluble copper salt in deionized water, add a certain amount of complexing agent and adjust the pH of the copper source solution;

[0008] S3 powder-liquid mixing replacement: add the activated carbonyl iron powder in step S1 into deionized water and heat and stir at 40°C, then slowly dropwise add the copper source solution in step S2 to the suspension. After the reaction is completed, wash with water and filter to obtain the replaced copper-coated iron powder A;

[0009] S4 two-stage reduction: the copper-coated iron powder A replaced in step S3 is added to deionized water and heated at a constant temperature of 40°C with stirring, and then a certain amount of dispersant and reducing agent is added, and the copper source solution in step S2 is added dropwise thereto. After the addition is completed, a small amount of accelerator and strong reducing agent are added, and the temperature is raised to 60°C. After the reaction is completed, the copper-coated iron powder B after two-stage reduction is obtained by washing with water, filtering, and drying;

[0010] S5: Mixing the powder raw materials: The copper-clad iron powder B prepared by chemical plating in step S4 and the pure copper powder are mixed in proportion, and then placed in a mixer for mixing to prepare a uniformly mixed alloy powder;

[0011] S6: Pressing and forming the raw materials: The alloy powder mixed evenly in step S5 is placed in an elastic rubber bag, and then placed in a cold isostatic press for pressing and forming to obtain a formed green body;

[0012] S7 sintering and densification: placing the green compact pressed in step S6 into a vacuum sintering furnace for sintering to obtain a copper-iron alloy sintered ingot;

[0013] S8 deformation processing: the ingot sintered in step S7 is taken out of the furnace at the sintering temperature, and then hot extruded and drawn to obtain rods and wires, or hot rolled and cold rolled to obtain plates and strips;

[0014] S9 high temperature heat treatment: the rod, wire or plate and strip material after rolling in step S8 is subjected to online solid solution treatment, then placed in a protective environment of hydrogen atmosphere for aging heat treatment, followed by low temperature tension annealing, and finally cleaned to obtain a copper-iron alloy material;

[0015] The aging treatment temperature in step S9 is 350-650°C, the aging time is 4-10h, the low-temperature tension annealing temperature in step S9 is 150-300°C, the annealing time is 2-5h, and the tension is 50-80MPa.

[0016] Furthermore, the acid solution for pickling described in step S1 is at least one of dilute sulfuric acid and dilute hydrochloric acid, and the volume concentration of the solution is 10%-20%. The dispersant described in step S1 is at least one of polyvinyl pyrrolidone, polyethylene glycol and polyvinyl alcohol, and the added mass percentage is 2%-5% of the iron powder. The corrosion inhibitor described in step S1 is at least one of methylthiourea and ethylthiourea, and the added mass percentage is 0.3%-1.2% of the iron powder.

[0017] Furthermore, the water-soluble copper salt in step S2 is at least one of copper sulfate, copper nitrate and copper chloride, and the Cu 2+ The concentration is 0.6-1.2 mol / L, the complexing agent described in step S2 is at least one of sodium citrate, ammonium citrate, polyethylene glycol-ethyl cellulose and disodium ethylenediaminetetraacetic acid, and the added concentration is 6.4-12.7 g / L, and the pH adjustment described in step S2 is glacial acetic acid, and the pH value is 2.2-5.4.

[0018] Furthermore, the dispersant described in step S4 is at least one of polymethyl acrylate and polyurethane, and the added mass percentage is 1.5%-3.5% of the iron powder. The reducing agent described in step S4 is at least one of glyoxylic acid, aminoacetic acid and glucose, and the added concentration is 5.2-8.4 g / L. The strong reducing agent described in step S4 is at least one of sodium hyposulfite, sodium sulfite and tetrabutylammonium borohydrate, and the added concentration is 1.2-4.6 g / L. The accelerator described in step S4 is 2-mercaptobenzothiazole, and the added concentration is 0.6-1.8 g / L.

[0019] Furthermore, the pure copper powder described in step S5 is at least one of water atomized powder, gas atomized powder and water-gas combined atomized powder, with an average particle size of 5-100 μm. The mass ratio of copper powder to copper-clad iron powder in the alloy powder described in step S5 is in the range of: (2:1)-(10:1), and the powder mixing method described in step S5 adopts a mechanical mixing method of a V-type mixer.

[0020] Furthermore, the pressure of the cold isostatic pressing in step S6 is 100-500 MPa, and the holding time is 20-200 s.

[0021] Furthermore, the vacuum degree of the vacuum sintering furnace in step S7 is 10 -1 -10 -3 Pa, sintering temperature is 800-1000°C, and holding time is 3-6h.

[0022] Furthermore, the hot extrusion temperature in step S8 is 600-800°C, and the hot rolling temperature is 600-900°C.

[0023] Furthermore, the solution treatment temperature in step S9 is 800-950° C., and the solution treatment time is 1-4 h.

[0024] Compared with the existing technology, the technical solution of this application has the following beneficial effects:

[0025] The method for preparing high-strength and high-conductivity powder metallurgy copper-iron alloy by using copper-clad iron powder, the prepared copper-clad iron composite powder coating layer has uniform structure and good density, and compared with the replacement copper plating method, there is no large amount of loose copper blocks with heterogeneous distribution on the surface, and the prepared copper-iron alloy ingot has low oxygen content, high sintering density, uniform composition without segregation, fine grain size, excellent processing performance, few residual solid-soluted iron atoms in the copper, and both high strength and high conductivity. At the same time, through the organic combination of chemical copper plating, powder metallurgy, deformation processing and heat treatment processes, the performance of copper-based alloy products is steadily improved. At the same time, the copper-iron alloy prepared by the powder metallurgy method in this application is compared with the traditional melting and casting method. The strength is increased by 3-6%, the conductivity is increased by 8-16%, the cost is reduced by 15-25%, and the production cycle is shortened by about 10-20%, which can realize continuous large-scale production and has important application prospects in key components in the fields of electronic information, aerospace, electromagnetic shielding, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the process structure of the preparation method of the present invention. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] Example 1:

[0029] Example 1 provides a method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy using copper-clad iron powder. In this preparation method, the alloy material is made of the following components by weight percentage: Cu 75.3%, Fe 24.7%, and the element composition ratio is 3:1, as shown in Table 1 below.

[0030] The specific method is as follows:

[0031] Step S1: Weigh 1 kg of carbonyl iron powder and place it in a 10% dilute sulfuric acid solution to clean it to remove oxides and oil stains on the particle surface and activate the surface. At the same time, add 20 g of PVP as a dispersant and 3 g of methylthiourea as a corrosion inhibitor and stir at room temperature for 20 minutes. Then wash it with deionized water, filter and dry it to obtain the activated carbonyl iron powder.

[0032] Step S2: Copper sulfate was fully dissolved in deionized water to form about 10 L of a copper sulfate solution with a concentration of 0.6 mol / L, 96 g of sodium citrate was added as a complexing agent, and the pH of the copper sulfate solution was adjusted to 5.4 with glacial acetic acid.

[0033] Step S3: Add the activated carbonyl iron powder to deionized water to a volume of 10 L and heat and stir at a constant temperature of 40°C. Then, slowly add 5 L of the prepared copper sulfate solution to the suspension. After the reaction is completed, wash with water and filter to obtain the replaced copper-coated iron powder.

[0034] Step S4: The replaced copper-clad iron powder is added to deionized water to a volume of 10 L and heated at a constant temperature of 40°C with stirring. Subsequently, 15 g of polymethyl acrylate is added as a dispersant and 52 g of glyoxylic acid is added as a reducing agent. Subsequently, 5 L of the prepared copper sulfate solution is slowly added dropwise to the suspension. After the addition is complete, 6 g of 2-mercaptobenzothiazole is added as a promoter and 46 g of sodium hyposulfite is added as a secondary strong reducing agent, and the temperature is raised to 60°C. After the reaction is completed, the copper-clad iron powder is washed with water, filtered, and dried to obtain the two-stage reduced copper-clad iron powder.

[0035] Step S5: Weigh 1315.4 g of water-vapor atomized copper powder with an average particle size of 100 μm and 684.8 g of copper-coated iron powder at a powder mass ratio of 2:1, and then put them into a V-type mixer for mixing for 1.5 hours. After the mixing is completed, a uniformly mixed alloy powder is obtained.

[0036] Step S6: The mixed powder is placed in a silica gel bag with an inner cavity size of 150×100×25 mm. After packaging, the bag is placed in a cold isostatic press for pressing. The cold isostatic pressing pressure is 50 MPa and the holding time is 200 s. After pressing, a 142×87×21 mm plate green body is obtained.

[0037] Step S7: placing the plate green body formed by cold isostatic pressing into a sintering furnace in a hydrogen atmosphere at a sintering temperature of 700° C. for 6 hours to obtain a copper-iron alloy sintered plate blank after sintering.

[0038] Step S8: hot rolling the sintered slab at a temperature of 600° C. to obtain a 15 mm thick slab. The slab is then subjected to surface oxide scale removal and cold rolling for multiple times to obtain an alloy slab with a thickness of 1 mm.

[0039] Step S9: The copper-iron alloy plate is placed at 950°C for solution treatment for 1 hour; then, an aging heat treatment is performed at 650°C for 4 hours; finally, a low-temperature tension annealing is performed at 150°C for 5 hours at a tension of 50 MPa, and a copper-iron alloy plate with a thickness of 1 mm is finally obtained. The strength and conductivity test results are: hardness 234 HV, tensile strength 832 MPa, and conductivity 58% IACS.

[0040] In the above Example 1, copper-clad iron powder was prepared by chemical copper plating, and after mixing with water vapor atomized copper powder, cold isostatic pressing, vacuum sintering, hot rolling and cold rolling were performed. Finally, solution treatment was performed at 950°C for 1 hour, aging treatment was performed at 650°C for 4 hours, and low-temperature tension annealing was performed at 150°C for 5 hours to obtain an alloy plate with a thickness of 1 mm, a hardness of 234 HV, a tensile strength of 832 MPa, and a conductivity of 58% IACS.

[0041] This embodiment demonstrates that by optimizing process parameters, a copper-iron alloy plate with both high strength and high conductivity can be produced, which is suitable for application scenarios with high performance requirements.

[0042] Example 2:

[0043] Example 2 provides a method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy using copper-clad iron powder. In this preparation method, the alloy material is made of the following components by weight percentage: Cu83.4%, Fe16.6%, and the element composition ratio is 5:1, as shown in Table 1 below.

[0044] The specific method is as follows:

[0045] Step S1: Weigh 1 kg of carbonyl iron powder and place it in a 15% dilute sulfuric acid solution to clean it to remove oxides and oil stains on the particle surface and activate the surface. At the same time, add 30 g of polyethylene glycol as a dispersant and 5 g of ethylthiourea as a corrosion inhibitor and stir at room temperature for 20 minutes. Then wash it with deionized water, filter and dry it to obtain the activated carbonyl iron powder.

[0046] Step S2: Copper nitrate was fully dissolved in deionized water to form about 10 L of a copper nitrate solution with a concentration of 0.8 mol / L, 85 g of ammonium citrate was added as a complexing agent, and the pH of the copper nitrate solution was adjusted to 4.2 with glacial acetic acid.

[0047] Step S3: Add the activated carbonyl iron powder to deionized water to a volume of 10 L and heat and stir at a constant temperature of 40° C. Then, slowly add 5 L of the prepared copper nitrate solution to the suspension. After the reaction is completed, wash with water and filter to obtain the replaced copper-coated iron powder.

[0048] Step S4: The replaced copper-clad iron powder is added to deionized water to a constant volume of 10 L and heated at a constant temperature of 40°C with stirring. Subsequently, 20 g of polyurethane is added as a dispersant and 64 g of glycine is added as a reducing agent. Subsequently, 5 L of the prepared copper nitrate solution is slowly added dropwise to the suspension. After the addition is completed, 10 g of 2-mercaptobenzothiazole is added as a promoter and 40 g of sodium sulfite is added as a secondary strong reducing agent, and the temperature is raised to 60°C. After the reaction is completed, the copper-clad iron powder is washed with water, filtered, and dried to obtain the two-stage reduced copper-clad iron powder.

[0049] Step S5: Weigh 3745.6 g of water-atomized copper powder with an average particle size of 60 μm and 1254.2 g of copper-coated iron powder at a powder mass ratio of 3:1, and then put them into a V-type mixer for mixing for 1.5 hours. After the mixing is completed, a uniformly mixed alloy powder is obtained.

[0050] Step S6: The mixed powder is placed in a silica gel bag with an inner cavity size of 200×150×30 mm. After packaging, the bag is placed in a cold isostatic press for pressing. The cold isostatic pressing pressure is 150 MPa and the holding time is 100 s. After pressing, a 188×135×26 mm plate green body is obtained.

[0051] Step S7: Place the green sheet formed by cold isostatic pressing into a vacuum sintering furnace, evacuate the vacuum and perform vacuum sintering with a vacuum degree of 10-1 Pa, a sintering temperature of 800°C, and a holding time of 5 hours. After sintering, a copper-iron alloy sintered sheet is obtained.

[0052] Step S8: hot rolling the sintered slab at a temperature of 900° C. to a thickness of 10 mm. The slab is then subjected to surface oxide scale removal and cold rolling for multiple times to obtain an alloy strip with a thickness of 0.5 mm.

[0053] Step S9: The copper-iron alloy strip is placed at 900°C for solution treatment for 2 hours; then, it is subjected to aging heat treatment at 550°C for 6 hours; finally, it is subjected to low-temperature tension annealing at 200°C for 4 hours at a tension of 60 MPa, ultimately obtaining a copper-iron alloy strip with a thickness of 0.5 mm. The strength and conductivity test results are as follows: hardness 193 HV, tensile strength 723 MPa, and conductivity 66% IACS.

[0054] In the above Example 2, copper-clad iron powder was prepared by chemical copper plating and mixed with water-atomized copper powder. After cold isostatic pressing, vacuum sintering, hot rolling and cold rolling, it was finally solution treated at 900°C for 2 hours, aged at 550°C for 6 hours, and low-temperature tension annealing at 200°C for 4 hours to obtain an alloy strip with a thickness of 0.5 mm. The alloy strip had a hardness of 193 HV, a tensile strength of 723 MPa, and a conductivity of 66% IACS.

[0055] This embodiment shows that by precisely controlling the process parameters, the electrical conductivity and mechanical properties of the alloy can be effectively improved, making it suitable for fields such as electronics and electromagnetic shielding.

[0056] Example 3:

[0057] Example 3 provides a method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy using copper-clad iron powder. In this preparation method, the alloy material is made of the following components by weight percentage: Cu 90.1%, Fe 9.9%, and the element composition ratio is 9:1, as shown in Table 1 below.

[0058] The specific method is as follows:

[0059] Step S1: Weigh 2 kg of carbonyl iron powder and place it in a 18% dilute hydrochloric acid solution to clean it to remove oxides and oil stains on the particle surface and activate the surface. At the same time, add 80 g of polyvinyl alcohol as a dispersant and 20 g of methylthiourea as a corrosion inhibitor and stir at room temperature for 20 minutes. Then wash it with deionized water, filter and dry it to obtain the activated carbonyl iron powder.

[0060] Step S2: Copper chloride was fully dissolved in deionized water to form about 20 L of a copper chloride solution with a concentration of 1.0 mol / L, 210 g of PEG-EC was added as a complexing agent, and the pH of the copper chloride solution was adjusted to 3.5 with glacial acetic acid.

[0061] Step S3: Add the activated carbonyl iron powder to deionized water to a volume of 20 L and heat and stir at a constant temperature of 40°C. Then, slowly add 10 L of the prepared copper chloride solution to the suspension. After the reaction is completed, wash with water and filter to obtain the replaced copper-coated iron powder.

[0062] Step S4: The replaced copper-coated iron powder is added to deionized water to a volume of 20 L and heated at a constant temperature of 40°C with stirring. Subsequently, 50 g of polymethyl acrylate is added as a dispersant and 152 g of glucose is added as a reducing agent. Subsequently, 10 L of the prepared copper chloride solution is slowly added dropwise to the suspension. After the addition is completed, 28 g of 2-mercaptobenzothiazole is added as a promoter and 68 g of tetrabutylammonium borate is added as a secondary strong reducing agent. The temperature is raised to 60°C. After the reaction is completed, the copper-coated iron powder is washed with water, filtered, and dried to obtain the two-stage reduced copper-coated iron powder.

[0063] Step S5: Weigh 11810.9 g of aerosolized copper powder with an average particle size of 30 μm and 2288.3 g of copper-coated iron powder at a powder mass ratio of 5:1, and then put them into a V-type mixer for mixing for 1.5 hours. After the mixing is completed, a uniformly mixed alloy powder is obtained.

[0064] Step S6: The mixed powder is placed in a silica gel bag with an inner cavity size of φ95×300 mm. After packaging, the powder is placed in a cold isostatic press for pressing. The cold isostatic pressing pressure is 300 MPa and the holding time is 50 s. After the pressing is completed, a φ90×289 mm rod green body is obtained.

[0065] Step S7: Place the cold isostatically pressed green bar into a vacuum sintering furnace, evacuate the vacuum and perform vacuum sintering with a vacuum degree of 10-2 Pa, a sintering temperature of 900°C, and a holding time of 4 hours to obtain a copper-iron alloy sintered bar blank.

[0066] Step S8: The sintered rod blank is subjected to hot extrusion treatment at a temperature of 600° C. The diameter of the rod after extrusion is 15 mm. The surface oxide scale is then removed and the rod is drawn to an alloy rod with a diameter of 5 mm.

[0067] Step S9: The copper-iron alloy rod is placed at 850°C for solution treatment for 3 hours; then, it is subjected to aging heat treatment at 450°C for 8 hours; finally, it is subjected to low-temperature tension annealing at 250°C for 3 hours at a tension of 70 MPa, and finally, a copper-iron alloy rod with a diameter of 5 mm is obtained. The strength and conductivity test results are as follows: hardness 162 HV, tensile strength 621 MPa, and conductivity 72% IACS.

[0068] In Example 3 above, copper-clad iron powder was prepared by chemical copper plating, and after mixing with atomized copper powder, cold isostatic pressing, vacuum sintering, hot extrusion, and drawing were performed. Finally, solution treatment was performed at 850°C for 3 hours, aging treatment was performed at 450°C for 8 hours, and low-temperature tension annealing was performed at 250°C for 3 hours to obtain an alloy rod with a diameter of 5 mm, a hardness of 162 HV, a tensile strength of 621 MPa, and a conductivity of 72% IACS.

[0069] This embodiment demonstrates that by optimizing the process flow, copper-iron alloy rods with both high strength and high conductivity can be produced, which are suitable for fields such as aerospace and electronic information.

[0070] Example 4:

[0071] Example 4 provides a method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy using copper-clad iron powder. In this preparation method, the alloy material is made of the following components by weight percentage: Cu 95.1%, Fe 4.9%, and the element composition ratio is 19:1, as shown in Table 1 below.

[0072] The specific method is as follows:

[0073] Step S1: Weigh 2 kg of carbonyl iron powder and place it in a 20% dilute hydrochloric acid solution to clean it to remove oxides and oil stains on the particle surface and activate the surface. At the same time, add 100 g of PVP as a dispersant and 24 g of ethylthiourea as a corrosion inhibitor and stir at room temperature for 20 minutes. Then wash it with deionized water, filter and dry it to obtain the activated carbonyl iron powder.

[0074] Step S2: Copper sulfate is fully dissolved in deionized water to form about 20 L of a copper sulfate solution with a concentration of 1.2 mol / L, 254 g of disodium ethylenediaminetetraacetic acid is added as a complexing agent, and the pH of the copper chloride solution is adjusted to 2.2 with glacial acetic acid.

[0075] Step S3: Add the activated carbonyl iron powder to deionized water to a volume of 20 L and heat and stir at a constant temperature of 40°C. Then, slowly add 10 L of the prepared copper sulfate solution to the suspension. After the reaction is completed, wash with water and filter to obtain the replaced copper-coated iron powder.

[0076] Step S4: The replaced copper-clad iron powder is added to deionized water to a volume of 20 L and heated at a constant temperature of 40°C with stirring. Subsequently, 70 g of polyurethane is added as a dispersant and 168 g of glycine is added as a reducing agent. Subsequently, 10 L of the prepared copper sulfate solution is slowly added dropwise to the suspension. After the addition is completed, 36 g of 2-mercaptobenzothiazole is added as a promoter and 48 g of sodium sulfite is added as a secondary strong reducing agent, and the temperature is raised to 60°C. After the reaction is completed, the copper-clad iron powder is washed with water, filtered, and dried to obtain the two-stage reduced copper-clad iron powder.

[0077] Step S5: Weigh 13062.6 g of water-vapor atomized copper powder with an average particle size of 5 μm and 1257.6 g of copper-clad iron powder at a powder mass ratio of 10:1, and then put them into a V-type mixer for mixing for 1.5 hours. After the mixing is completed, a uniformly mixed alloy powder is obtained.

[0078] Step S6: The mixed powder is placed in a silica gel bag with an inner cavity size of φ95×300mm. After packaging, the powder is placed in a cold isostatic press for pressing. The cold isostatic pressing pressure is 500MPa and the holding time is 10s. After pressing, a rod blank of φ88×283mm is obtained.

[0079] Step S7: Place the cold isostatically pressed green bar into a vacuum sintering furnace, evacuate the vacuum and perform vacuum sintering with a vacuum degree of 10-3 Pa, a sintering temperature of 1000°C, and a holding time of 3 hours to obtain a copper-iron alloy sintered bar blank.

[0080] Step S8: The sintered rod blank is subjected to hot extrusion treatment at a temperature of 800° C. The diameter of the rod after extrusion is 10 mm. The surface oxide scale is then removed and the rod is drawn into an alloy wire with a diameter of 0.5 mm.

[0081] Step S9: The copper-iron alloy wire is subjected to solution treatment at 800°C for 4 hours; then, an aging heat treatment is performed at 350°C for 10 hours; finally, a low-temperature tension annealing is performed at 300°C for 2 hours at a tension of 80 MPa, and a copper-iron alloy wire with a diameter of 0.5 mm is obtained. The strength and conductivity test results are as follows: hardness 146 HV, tensile strength 552 MPa, and conductivity 78% IACS.

[0082] In the above Example 4, copper-clad iron powder was prepared by chemical copper plating and mixed with water vapor atomized copper powder. After cold isostatic pressing, vacuum sintering, hot extrusion and drawing, it was finally solution treated at 800°C for 4 hours, aged at 350°C for 10 hours, and low-temperature tension annealing at 300°C for 2 hours to obtain an alloy wire with a diameter of 0.5 mm, a hardness of 146 HV, a tensile strength of 552 MPa, and a conductivity of 78% IACS.

[0083] This embodiment shows that by precisely controlling the process parameters, the electrical conductivity and mechanical properties of the alloy can be effectively improved, making it suitable for fields such as high-precision electronic components and electromagnetic shielding.

[0084] The alloy composition, hardness, tensile strength and electrical conductivity in Examples 1-4 are listed in Table 1:

[0085] Table 1 Composition, hardness, strength and conductivity of different copper-iron alloys

[0086] Cu(wt.%) Fe(wt.%) Cu:Cu-Fe Hardness (HV) Tensile strength (MPa) Electrical conductivity (IACS) Example 1 75.3 24.7 2:1 234 832 58% Example 2 83.4 16.6 3:1 193 723 66% Example 3 90.1 9.9 5:1 162 621 72% Example 4 95.1 4.9 10:1 146 552 78%

[0087] Therefore, in Examples 1-4, compared with the prior art, the present application has the following key points:

[0088] 1) Based on powder metallurgy, the present invention uses chemical copper plating to prepare a copper-clad iron composite powder with a uniform surface coating. The iron content of the mixed powder is controlled to be 4.9% to 24.7%. By combining the high strength of the iron-based core with the excellent corrosion resistance and high thermal conductivity of the copper-based shell, the copper-clad iron composite powder solves the problems of uneven organization, component segregation, and structural instability that occur during the production process of traditional copper-iron mixed powders.

[0089] 2) The complexing agents (sodium citrate, ammonium citrate, polyethylene glycol-ethylcellulose, and disodium ethylenediaminetetraacetic acid) used during the replacement process have minimal impact on the coating layer, reducing the deposition rate of the innermost copper layer during the replacement process, achieving high uniformity and coverage of the initial copper coating layer with strong adhesion. The accelerator (2-mercaptobenzothiazole) used during the second reduction process effectively accelerates the copper coating speed and density in the later stages of the coating, forming a thicker copper coating layer on the surface of the Fe powder particles.

[0090] 3) The present invention combines high-temperature sintering of copper-iron alloys with deformation processing. The deformation processing temperature after sintering must be strictly controlled to prevent the occurrence of processing defects such as cracks, peeling, and wrinkles. At the same time, the process parameters of solid solution and aging heat treatment, including temperature and time, are optimized to strengthen the copper alloy matrix and improve its mechanical properties, and also effectively improve the electrical conductivity and corrosion resistance of the copper-iron alloy. The low-temperature tension annealing process can eliminate some movable dislocations within the alloy, leaving immobile dislocations, which can improve the alloy's stress relaxation performance to a certain extent.

[0091] In summary, this application combines high-temperature sintering of copper-iron alloy with deformation processing. The deformation processing temperature after sintering must be strictly controlled to prevent the occurrence of processing defects such as cracks, peeling, and wrinkles; at the same time, the process parameters of solid solution and aging heat treatment, including temperature and time, are optimized, which can not only strengthen the copper alloy matrix and improve its mechanical properties, but also effectively improve the conductivity and corrosion resistance of the copper-iron alloy; the low-temperature tension annealing process can eliminate some movable dislocations inside the alloy, leaving immovable dislocations, which can improve the stress relaxation performance of the alloy to a certain extent.

[0092] The working principle of the above embodiment is as follows: using carbonyl iron powder and copper salt solution as raw materials, adding a certain amount of dispersant, reducing agent, etc., preparing copper-clad iron powder by chemical copper plating, and then combining the powder metallurgy process to mix the atomized copper powder and copper-clad iron powder to obtain uniform powder, forming and sintering to obtain a dense billet, and then performing deformation heat treatment to obtain copper-iron alloy plates, strips, rods and wires with uniform Fe phase distribution. Directly using copper-iron mixed powder will cause problems such as uneven organization and component segregation of powder metallurgy copper-iron materials. Copper-clad iron composite powder is a metal-coated powder with iron as the "core" and copper as the "shell". Its compression The product has good performance and low sintering temperature. The obtained product has the advantages of high strength of the iron-based core and excellent corrosion resistance and high thermal conductivity of the copper-based shell. It can effectively solve the problems of uneven organization, component segregation, and low conductivity caused by the difficulty in precipitation of residual solid-dissolved iron atoms in copper in the production process of traditional copper-iron mixed powder. At the same time, when the copper-clad iron powder is prepared by the chemical copper plating method, copper can be evenly deposited on the surface of the iron matrix, avoiding the heterogeneous distribution of a large number of loose copper blocks on the surface of the iron matrix of the copper-clad iron powder prepared by the displacement copper plating method. Therefore, the chemical copper plating method is an effective technology for preparing high-activity and high-stability copper-clad iron powder.

[0093] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0094] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing high-strength and high-conductivity powder metallurgy copper-iron alloy from copper-clad iron powder, characterized in that: The following steps are involved: S1 Iron powder acid washing and activation: The carbonyl iron powder is placed in an acid solution for cleaning, and a small amount of dispersant and corrosion inhibitor is added at the same time. Then, it is washed with deionized water, filtered and dried to obtain the activated carbonyl iron powder; Preparation of S2 copper source solution: fully dissolve water-soluble copper salt in deionized water, add a certain amount of complexing agent and adjust the pH of the copper source solution; S3 powder-liquid mixing replacement: add the activated carbonyl iron powder in step S1 into deionized water and heat and stir at 40°C, then slowly dropwise add the copper source solution in step S2 to the suspension. After the reaction is completed, wash with water and filter to obtain the replaced copper-coated iron powder A; S4 two-stage reduction: the copper-coated iron powder A replaced in step S3 is added to deionized water and heated at a constant temperature of 40°C with stirring, and then a certain amount of dispersant and reducing agent is added, and the copper source solution in step S2 is added dropwise thereto. After the addition is completed, a small amount of accelerator and strong reducing agent are added, and the temperature is raised to 60°C. After the reaction is completed, the copper-coated iron powder B after two-stage reduction is obtained by washing with water, filtering, and drying; S5: Mixing the powder raw materials: The copper-clad iron powder B prepared by chemical plating in step S4 and the pure copper powder are mixed in proportion, and then placed in a mixer for mixing to prepare a uniformly mixed alloy powder; S6: Pressing and forming the raw materials: The alloy powder mixed evenly in step S5 is placed in an elastic rubber bag, and then placed in a cold isostatic press for pressing and forming to obtain a formed green body; S7 sintering and densification: placing the green compact pressed in step S6 into a vacuum sintering furnace for sintering to obtain a copper-iron alloy sintered ingot; S8 deformation processing: the ingot sintered in step S7 is taken out of the furnace at the sintering temperature, and then hot extruded and drawn to obtain rods and wires, or hot rolled and cold rolled to obtain plates and strips; S9 high temperature heat treatment: the rod, wire or plate and strip material after rolling in step S8 is subjected to online solid solution treatment, then placed in a protective environment of hydrogen atmosphere for aging heat treatment, followed by low temperature tension annealing, and finally cleaned to obtain a copper-iron alloy material; The aging treatment temperature in step S9 is 350-650°C, the aging time is 4-10h, the low-temperature tension annealing temperature in step S9 is 150-300°C, the annealing time is 2-5h, and the tension is 50-80MPa.

2. The method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from a copper-clad iron powder according to claim 1, characterized in that: The acid solution for pickling described in step S1 is at least one of dilute sulfuric acid and dilute hydrochloric acid, and the volume concentration of the solution is 10%-20%. The dispersant described in step S1 is at least one of polyvinyl pyrrolidone, polyethylene glycol and polyvinyl alcohol, and the added mass percentage is 2%-5% of the iron powder. The corrosion inhibitor described in step S1 is at least one of methylthiourea and ethylthiourea, and the added mass percentage is 0.3%-1.2% of the iron powder.

3. The method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from a copper-clad iron powder according to claim 1, characterized in that: The water-soluble copper salt in step S2 is at least one of copper sulfate, copper nitrate and copper chloride, and the Cu in the copper source solution is 2+ The concentration is 0.6-1.2 mol / L, the complexing agent described in step S2 is at least one of sodium citrate, ammonium citrate, polyethylene glycol-ethyl cellulose and disodium ethylenediaminetetraacetic acid, and the added concentration is 6.4-12.7 g / L, and the pH adjustment described in step S2 is glacial acetic acid, and the pH value is 2.2-5.

4.

4. The method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from a copper-clad iron powder according to claim 1, characterized in that: The dispersant described in step S4 is at least one of polymethyl acrylate and polyurethane, and the added mass percentage is 1.5%-3.5% of the iron powder. The reducing agent described in step S4 is at least one of glyoxylic acid, aminoacetic acid and glucose, and the added concentration is 5.2-8.4 g / L. The strong reducing agent described in step S4 is at least one of sodium hyposulfite, sodium sulfite and tetrabutylammonium borohydrate, and the added concentration is 1.2-4.6 g / L. The accelerator described in step S4 is 2-mercaptobenzothiazole, and the added concentration is 0.6-1.8 g / L.

5. The method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from a copper-clad iron powder according to claim 1, characterized in that: The pure copper powder described in step S5 is at least one of water atomized powder, gas atomized powder and water-gas combined atomized powder, and has an average particle size of 5-100 μm. The mass ratio of copper powder to copper-clad iron powder in the alloy powder described in step S5 is in the range of: (2:1)-(10:1). The powder mixing method described in step S5 adopts a mechanical mixing method of a V-type mixer.

6. The method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from a copper-clad iron powder according to claim 1, characterized in that: The pressure of the cold isostatic pressing in step S6 is 100-500 MPa, and the holding time is 20-200 s.

7. The method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from a copper-clad iron powder according to claim 1, characterized in that: The vacuum degree of the vacuum sintering furnace in step S7 is 10 -1 -10 -3 Pa, sintering temperature is 800-1000°C, and holding time is 3-6h.

8. The method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from a copper-clad iron powder according to claim 1, characterized in that: The hot extrusion temperature in step S8 is 600-800°C, and the hot rolling temperature is 600-900°C.

9. The method for preparing a high-strength and high-conductivity powder metallurgy copper-iron alloy from a copper-clad iron powder according to claim 1, characterized in that: The solution treatment temperature in step S9 is 800-950°C, and the solution treatment time is 1-4h.

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