Preparation method of corrosion-resistant copper-iron alloy

Abstract

The invention relates to the technical field of copper alloy materials, in particular to a preparation method of a corrosion-resistant copper-iron alloy, which comprises the following steps: S1, plating copper on the surface of iron powder: performing oil removal cleaning and acid pickling activation on the iron powder with the particle size of 15-50 microns and the purity of more than or equal to 99.8%; the iron powder is treated in a chemical copper plating solution, the formula of the plating solution comprises 10-20 g / L of copper sulfate, 5-10 mL / L of formaldehyde and 20-30 g / L of EDTA, the pH is 11-13, the temperature is 40-60 DEG C, the reaction time is 10-60 minutes, and a copper plating layer with the mass accounting for 20%-30% of that of the iron powder is formed on the surface of the iron powder. The uniform copper plating layer on the surface of the copper-plated iron powder remarkably improves the corrosion resistance of the iron powder. In the cold spraying process, the melting process does not occur, the organization structure of the copper-plated iron powder in the coating can be kept consistent with that of the powder, a plating layer on the surface of the powder is not broken, and the corrosion resistance of the copper-iron alloy coating is guaranteed. The coating prepared through cold spraying is compact in structure and simple in process, the thickness of the coating can be adjusted and controlled, and additive manufacturing can be achieved according to adjustment of process parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of copper alloy materials, and more particularly to a method for preparing a corrosion-resistant copper-iron alloy. Background Art

[0002] Copper-iron alloy, as a structural and functional integrated material, combines the high electrical and thermal conductivity, good ductility and other properties of copper with the strength and good magnetic conductivity of iron. It has excellent performance controllability and has broad application prospects in the fields of integrated circuit lead frames, electrified railway contact networks, large generator rotors, resistance welding electrodes, etc.

[0003] Currently, the preparation methods of copper-iron alloys mainly adopt melting casting and powder metallurgy.

[0004] The copper-iron alloy is prepared by the melting and casting method, which uses pure copper and pure iron as raw materials. The iron is in situ present in the alloy matrix in the form of primary phase and precipitation phase through alloy smelting, forming a copper-iron in situ alloy. Powder metallurgy is the process of pressing and sintering copper-iron alloy powder or a mixture of copper powder and iron powder to prepare copper-iron alloy; The iron element in the copper-iron alloy prepared by the above method exists in the alloy in the form of an iron-rich phase (melting casting method) or in the form of pure iron (powder metallurgy method). Since the corrosion resistance of iron is worse than that of copper, the corrosion resistance of the copper-iron alloy is worse than that of other copper alloys. This is also one of the main factors hindering the application of copper-iron alloys.

[0005] Therefore, we proposed a method for preparing corrosion-resistant copper-iron alloy to solve the above problems. Summary of the Invention

[0006] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a method for preparing a corrosion-resistant copper-iron alloy to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for preparing a corrosion-resistant copper-iron alloy, comprising the following steps: Step S1: Copper plating on the surface of iron powder: Degreasing, cleaning and pickling of iron powder with a particle size of 15 to 50 μm and a purity of ≥99.8%; Treating iron powder in an electroless copper plating solution, wherein the plating solution formula is 10g / L-20g / L copper sulfate, 5mL / L-10mL / L formaldehyde, 20g / L-30g / L EDTA, pH 11-13, temperature 40°C-60°C, reaction time 10-60 minutes, so that a copper plating layer with a mass of 20%-30% of the iron powder is formed on the surface of the iron powder; Clean and dry the copper-plated iron powder; Step S2: preparing a mixed powder: mixing copper-plated iron powder with electrolytic copper powder having a particle size of 20 μm to 50 μm and a purity of ≥99.9% in a weight ratio of (5:1) to (10:1), washing and drying to obtain a copper-iron mixed powder; Step S3: Cold spraying: Using nitrogen as the protective gas, spray the mixed powder onto the surface of the pretreated substrate at a gas pressure of 3-5 MPa, a gas temperature of 500-700°C, and a spraying distance of 10-30 mm to form a Cu-Fe alloy coating with a thickness of 100-1000 μm.

[0008] In a preferred embodiment, the pickling activation in step S1 uses dilute hydrochloric acid or dilute sulfuric acid with a concentration of 0.5 mol / L to 2 mol / L, and the pickling time is 5 minutes to 15 minutes.

[0009] In a preferred embodiment, the thickness of the copper coating of the copper-plated iron powder in step S1 is 0.5 μm to 2 μm.

[0010] In a preferred embodiment, the weight ratio of the electrolytic copper powder to the copper-plated iron powder in the mixed powder in step S2 is 7:1 to 8:1.

[0011] In a preferred embodiment, the porosity of the cold-sprayed coating in step S3 is ≤2%, and the bonding strength between the coating and the substrate is ≥100 MPa.

[0012] In a preferred embodiment, in step S3, the substrate is aluminum, copper or stainless steel, and the substrate surface pretreatment includes sandblasting or chemical cleaning.

[0013] In a preferred embodiment, during spraying in step S3, the nitrogen flow rate is 50 m³ / h to 100 m³ / h, and the nozzle movement speed is 50 mm / s to 200 mm / s.

[0014] In a preferred embodiment, the corrosion resistance of the Cu-Fe alloy coating is verified by a salt spray test, and the corrosion weight loss rate is reduced by ≥50% compared with the uncoated copper iron powder coating.

[0015] A corrosion-resistant copper-iron alloy coating has a composition of 75% to 95% Cu and 5% to 25% Fe, and has no oxide inclusions on the surface.

[0016] In a preferred embodiment, the electrical conductivity is ≥80% IACS and the hardness is ≥120 HV, and the material is suitable for integrated circuit lead frames or resistance welding electrodes.

[0017] Technical effects and advantages of the present invention: Compared with the existing Cu-Fe alloy, the present invention has the following advantages: 1. The uniform copper coating on the surface significantly improves the corrosion resistance of the iron powder.

[0018] 2. No melting process occurs in the cold spraying process, the organizational structure of the copper-plated iron powder in the coating can be consistent with the powder, and the coating on the powder surface will not crack, thus ensuring the corrosion resistance of the copper-iron alloy coating.

[0019] 3. The coating prepared by cold spraying has a dense structure and a simple process. The coating thickness can be controlled, and additive manufacturing can be achieved by adjusting the process parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the process roadmap of the present invention; Figure 2 This is a comparison chart of the salt spray test of the corrosion-resistant copper-iron alloy and the copper-iron alloy in the present invention. DETAILED DESCRIPTION

[0021] 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.

[0022] Cold spray technology is based on using compressed gas (nitrogen, helium, etc.) as an accelerating gas flow to drive powder particles (particle size 1-50um) to collide with the substrate at low temperature (<1000℃), supersonic speed (300-1200 m / s) and in a completely solid state, causing the particles to undergo strong plastic deformation and deposit to form a coating.

[0023] Compared with traditional casting and powder metallurgy methods, cold spraying has the following advantages: 1. No melting-solidification process occurs during cold spraying, the powder hardly undergoes oxidation, decomposition and phase change, and there is no mutual dissolution between metals, which has little thermal impact on the substrate and powder particles.

[0024] The coating is dense, has low porosity, and has a high bond strength of over 100 MPa. Furthermore, the coating is internally compressive, making it suitable for thick coatings and can be directly sprayed to form bulk materials or components.

[0025] Reference Figure 1-2 The technical solution of the present invention is to prepare a uniform copper plating layer of a certain thickness on the surface of iron powder, and then mechanically mix the obtained Cu-coated Fe powder with atomized copper powder in a certain ratio, select copper-iron mixed powder with a suitable particle size range, and use cold spray technology to prepare a Cu-Fe alloy coating.

[0026] The steps and conditions for preparing the corrosion-resistant Cu-Fe alloy coating are as follows: 1. Copper plating on iron powder: (1) Ultrasonic degreasing and cleaning of the iron powder with acetone to remove surface oxides and impurities. (2) Soaking in dilute hydrochloric acid (HCl) or sulfuric acid (H2SO4) to remove the oxide film and activate the surface. (3) Electroless copper plating of the iron powder. (4) Rinse the copper-plated iron powder with deionized water until neutral and vacuum dry (60-80°C) to prevent oxidation.

[0027] The particle size of the iron powder is 15-50μm, and the purity of the iron powder is ≥99.8%.

[0028] In the electroless copper plating process, the plating solution formula is: copper sulfate (CuSO4·5H2O): 10-20 g / L; formaldehyde (HCHO, reducing agent): 5-10 mL / L; EDTA (chelating agent): 20-30 g / L; pH adjuster (NaOH): maintain pH 11-13; temperature 40-60°C, stirring speed controlled to suspend iron powder, reaction time 10-60 minutes.

[0029] The mass of the copper coating in the copper-plated iron powder is 20%-30% of the mass of the iron powder.

[0030] 2. Preparation of mixed powder: (1) According to the chemical composition requirements, electrolytic copper powder and copper-plated iron powder of the required proportion are mechanically mixed to obtain the ingredients. (2) Pretreatment: The mixed powder is ultrasonically degreased with acetone to remove surface oxides and impurities. It is then dried in a vacuum drying oven at 80°C for 1 hour to obtain the copper-iron mixed powder for cold spraying.

[0031] The particle size of electrolytic copper powder is 20-50μm, and the purity of electrolytic copper powder is ≥99.9%; 3. Cold spraying: The cold spraying process is used to spray copper-iron mixed powder onto the pretreated substrate surface to produce a Cu-Fe alloy coating.

[0032] In the cold spraying process, the protective gas used during spraying is nitrogen, the gas pressure during spraying is 3MPa~5MPa, the gas temperature is 500℃~700℃, and the spraying distance between the nozzle and the substrate surface is 10mm~30mm.

[0033] Example 1 1. Copper plating on the surface of iron powder (1) Use acetone to ultrasonically degrease the iron powder to remove surface oxides and impurities; (2) Soak in dilute hydrochloric acid (HCl) to remove the oxide film and activate the surface.

[0034] (3) Chemical copper plating is performed on the surface of the iron powder. Formula of chemical copper plating solution: Copper sulfate (CuSO4·5H2O): 10 g / L; Formaldehyde (HCHO, reducing agent): 8 mL / L; EDTA (chelating agent): 20 g / L; pH 11; The temperature was 60°C, the iron powder was suspended by electromagnetic stirring, and the reaction time was 60 minutes. The mass of the copper coating in the copper-plated iron powder was 20% of the mass of the iron powder.

[0035] (4) Wash the copper-plated iron powder with deionized water until it is neutral and vacuum dry to prevent oxidation.

[0036] 2. Preparation of mixed powder: (1) Electrolytic copper powder and copper-plated iron powder were mixed in a weight ratio of 10:1 and mixed evenly by mechanical mixing.

[0037] (2) Pretreatment: The mixed powder was ultrasonically degreased with acetone to remove surface oxides and impurities. The powder was then dried in a vacuum drying oven at 80°C for 1 hour to obtain the copper-iron mixed powder for cold spraying.

[0038] 3. Cold spraying: A cold spray process was used to apply a copper-iron powder mixture to a pretreated copper substrate to create a Cu-Fe alloy coating. The specific process involved using nitrogen as the shielding gas at a pressure of 3 MPa, a working temperature of 600°C, a spray distance of 20 mm from the nozzle to the substrate, and a coating thickness of 300 μm.

[0039] Example 2 1. Copper plating on the surface of iron powder (1) Use acetone to ultrasonically degrease the iron powder to remove surface oxides and impurities; (2) Soak in dilute hydrochloric acid (HCl) to remove the oxide film and activate the surface.

[0040] (3) Chemical copper plating is performed on the surface of the iron powder.

[0041] Chemical copper plating solution formula: Copper sulfate (CuSO4·5H2O): 20 g / L; Formaldehyde (HCHO, reducing agent): 10 mL / L; EDTA (chelating agent): 20 g / L; pH 11; The temperature was 60°C, and the iron powder was suspended by electromagnetic stirring for 30 minutes. The mass of the copper coating in the copper-plated iron powder was 30% of the mass of the iron powder.

[0042] (4) Wash the copper-plated iron powder with deionized water until it is neutral and vacuum dry to prevent oxidation.

[0043] 2. Preparation of mixed powder: (1) Electrolytic copper powder and copper-plated iron powder were mixed in a weight ratio of 5:1 and mixed evenly by mechanical mixing.

[0044] (2) Pretreatment: The mixed powder was ultrasonically degreased with acetone to remove surface oxides and impurities. The powder was then dried in a vacuum drying oven at 80°C for 1 hour to obtain the copper-iron mixed powder for cold spraying.

[0045] 3. Cold spraying: A cold spray process was used to apply a copper-iron powder mixture to a pretreated copper substrate to create a Cu-Fe alloy coating. The specific process involved using nitrogen as the shielding gas at a pressure of 4 MPa, a working gas temperature of 700°C, a spray distance of 30 mm from the nozzle to the substrate, and a coating thickness of 800 μm.

[0046] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a corrosion-resistant copper-iron alloy, characterized in that: The following steps are involved: Step S1: Copper plating on the surface of iron powder: Degreasing, cleaning and pickling of iron powder with a particle size of 15 to 50 μm and a purity of ≥99.8% are performed; Treating iron powder in an electroless copper plating solution, wherein the plating solution formula is 10g / L-20g / L copper sulfate, 5mL / L-10mL / L formaldehyde, 20g / L-30g / L EDTA, pH 11-13, temperature 40°C-60°C, reaction time 10-60 minutes, so that a copper plating layer with a mass of 20%-30% of the iron powder is formed on the surface of the iron powder; Clean and dry the copper-plated iron powder; Step S2: preparing a mixed powder: mixing copper-plated iron powder with electrolytic copper powder having a particle size of 20 μm to 50 μm and a purity of ≥99.9% in a weight ratio of (5:1) to (10:1), washing and drying to obtain a copper-iron mixed powder; Step S3: Cold spraying: Using nitrogen as the protective gas, spray the mixed powder onto the surface of the pretreated substrate at a gas pressure of 3-5 MPa, a gas temperature of 500-700°C, and a spraying distance of 10-30 mm to form a Cu-Fe alloy coating with a thickness of 100-1000 μm.

2. The method for preparing a corrosion-resistant copper-iron alloy according to claim 1, wherein: In step S1 , the pickling activation is performed using dilute hydrochloric acid or dilute sulfuric acid with a concentration of 0.5 mol / L to 2 mol / L, and the pickling time is 5 minutes to 15 minutes.

3. The method for preparing a corrosion-resistant copper-iron alloy according to claim 1, wherein: The copper coating thickness of the copper-plated iron powder in step S1 is 0.5 μm to 2 μm.

4. The method for preparing a corrosion-resistant copper-iron alloy according to claim 1, wherein: The weight ratio of the electrolytic copper powder to the copper-plated iron powder in the mixed powder in step S2 is 7:1 to 8:

1.

5. The method for preparing a corrosion-resistant copper-iron alloy according to claim 1, wherein: The porosity of the cold-sprayed coating in step S3 is ≤2%, and the bonding strength between the coating and the substrate is ≥100 MPa.

6. The method for preparing a corrosion-resistant copper-iron alloy according to claim 1, wherein: In step S3, the substrate is aluminum, copper or stainless steel, and the substrate surface pretreatment includes sandblasting or chemical cleaning.

7. The method for preparing a corrosion-resistant copper-iron alloy according to claim 1, wherein: During spraying in step S3, the nitrogen flow rate is 50m³ / h to 100m³ / h, and the nozzle moving speed is 50mm / s to 200mm / s.

8. The method for preparing a corrosion-resistant copper-iron alloy according to claim 1, wherein: The corrosion resistance of the Cu-Fe alloy coating was verified by salt spray test, and the corrosion weight loss rate was reduced by ≥50% compared with the uncoated copper iron powder coating.

9. A corrosion-resistant copper-iron alloy coating, characterized in that: The invention is prepared by the method according to any one of claims 1 to 8, wherein the composition thereof is 75% to 95% Cu, 5% to 25% Fe, and has no oxide inclusions on the surface.

10. The method for preparing a corrosion-resistant copper-iron alloy according to claim 9, characterized in that: Its electrical conductivity is ≥80%IACS and hardness is ≥120HV, making it suitable for integrated circuit lead frames or resistance welding electrodes.

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