Rare earth modified copper-nickel alloy and electroplating process thereof

Abstract

This invention relates to a rare-earth modified copper-nickel alloy and its electroplating process, belonging to the field of alloy electroplating technology. It addresses the problems of existing copper-nickel alloys exhibiting coarse grains and grain boundary impurities, resulting in high corrosion rates, limited protective effects, poor coating density, and unreasonable addition of rare-earth elements. The invention precisely adds La (La) to a Cu-La master alloy. La refines the copper-nickel alloy grains, purifies grain boundaries, reduces pitting corrosion sources and intergranular corrosion channels, and improves the substrate's corrosion resistance by 30-40%. Vacuum induction melting in the process controls rare-earth burn-off, and optimized electroplating parameters ensure coating uniformity, making it suitable for industrial mass production. Through rare-earth modified substrate and double-layer electroplating protection, the alloy corrosion rate is reduced, and the pre-plated nickel layer forms a good transition with the substrate and Cu-Ni alloy layer, improving the adhesion to level 1 or higher. The main coating is dense and defect-free, effectively blocking the penetration of corrosive media.

Description

Technical Field

[0001] This invention relates to the field of alloy electroplating technology, and in particular to a rare earth modified copper-nickel alloy and its electroplating process. Background Technology

[0002] Copper-nickel alloys are widely used in applications such as ship condenser pipes, chemical pipelines, and electrical equipment connectors due to their excellent corrosion resistance, thermal and electrical conductivity, and mechanical properties.

[0003] The existing copper-nickel alloy matrix contains coarse grains and grain boundary impurities, which easily lead to intergranular corrosion and pitting corrosion, resulting in a high corrosion rate. When the surface is directly exposed to the corrosive medium, the oxide film is easy to fall off and break, resulting in limited protective effect. In the electroplating process, the adhesion between the substrate and the coating is insufficient, which easily leads to peeling and flaking. Moreover, the coating has poor density and cannot effectively block the penetration of corrosive media. At the same time, the addition of rare earth elements in copper-nickel alloys is unreasonable, which can easily lead to rare earth burn-off and component segregation, making it difficult to give full play to the role of refining grains and purifying grain boundaries.

[0004] To address the aforementioned problems, a rare-earth modified copper-nickel alloy and its electroplating process are proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a rare earth-modified copper-nickel alloy and its electroplating process, which solves the problems in the prior art where the existing copper-nickel alloy matrix has coarse grains and grain boundary impurities, which easily lead to intergranular corrosion and pitting corrosion, resulting in a high corrosion rate. When the surface is directly exposed to the corrosive medium, the oxide film is easy to fall off and break, resulting in limited protective effect. In the electroplating process, the adhesion between the substrate and the coating is insufficient, which easily leads to peeling and flaking. Moreover, the coating has poor density and cannot effectively block the penetration of corrosive media. At the same time, the addition of rare earth elements in the copper-nickel alloy is unreasonable, which easily leads to rare earth burn-off and component segregation, making it difficult to give full play to the functions of refining grains and purifying grain boundaries.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a rare earth modified copper-nickel alloy, comprising the following components by mass percentage: Ni: 14%~16%; Fe: 3%~5%; Mn: 0.5%~1.5%; La: 0.1%~0.3%; impurities are strictly controlled, with the balance being Cu. La is added in the form of Cu-La master alloy, and the La content of the Cu-La master alloy is 25%.

[0007] Another technical solution proposed by this invention: A rare earth-modified copper-nickel alloy and its electroplating process are as follows: S1: Raw material pretreatment: Prepare electrolytic Cu, electrolytic Ni, pure Fe, pure Mn and Cu-La master alloy, grind the surface, bake to remove oil and moisture; S2: Smelting process: charge the materials, melt them, add rare earth elements, and then cast them; S3: Pretreatment: Cleaning and activation of rare earth modified copper-nickel alloy; S4: Pre-plating nickel: Use Watt's nickel plating solution for base plating to form a dense transition layer and then rinse; S5: Cu-Ni alloy plating: The main body is corrosion resistant, and a Cu-Ni alloy layer is formed on the surface of the pre-plated nickel layer and then rinsed. S6: Post-treatment: Rinsing and passivation treatment, drying to improve stability.

[0008] Furthermore, the smelting process includes the following steps: S21: Batching and loading: Weigh out electrolytic Cu, electrolytic Ni, and pure Fe according to the above component ratios and load them into the crucible of the vacuum induction furnace; S22: Vacuuming and Melting: Start the vacuum system and heat up to completely melt the raw materials; S23: Refining: Refining for a period of time, followed by vacuum degassing and impurity removal; S24: Add Mn and rare earth elements: Add Mn after argon purging, add Cu-La master alloy, stir with high power to reduce oxidation, add in the form of master alloy to avoid rare earth burn-off and component segregation; S25: Casting and heat treatment: Casting is carried out under heating and argon protection. The ingot is homogenized by heat treatment and then cooled to room temperature in the furnace to obtain a rare earth modified copper-nickel alloy matrix.

[0009] Furthermore, the preprocessing includes the following steps: S31: Chemical degreasing: Place the rare earth modified copper-nickel alloy workpiece in an alkaline degreasing agent to remove oil stains and organic impurities; S32: Pickling and activation: H2SO4 removes oxide scale, activates the surface, and enhances the adhesion of the coating; S33: Ultrasonic rinsing: Ultrasonic cleaning plus deionized water rinsing to thoroughly remove residue and avoid coating defects.

[0010] Furthermore, the alkaline degreasing agent used in the pretreatment step is formulated as follows: pure water, NaOH 50–60 g / L, Na2CO3 20–30 g / L, Na3PO4 30–40 g / L.

[0011] Furthermore, the formula for the Watt nickel plating solution used in the pre-plating nickel step is: prepared with pure water, NiSO4 6H₂O₂ 250-300g / L, NiCl₂ 6H2O40–60g / L, H3BO335–45g / L.

[0012] Furthermore, the plating solution formulation used for the Cu-Ni alloy layer is as follows: sodium citrate complexing agent: 80–120 g / L; H3BO3: 30–40 g / L; sodium dodecyl sulfate wetting agent: 0.05–0.1 g / L; saccharin brightener: 0.5–1.0 g / L. This plating solution formulation has a pH of 7.0–8.0, an alkaline system, resulting in a more uniform coating and better corrosion resistance. It forms a uniform, dense, and defect-free Cu-Ni alloy layer, blocking corrosive media. The coating composition matches the substrate, resulting in low internal stress, strong adhesion, and a well-structured oxide film that enhances film density and adhesion. The Cu-Ni alloy layer thickness is ≥10 μm, ensuring long-term corrosion resistance.

[0013] Furthermore, the post-processing includes the following steps: S61: Passivation treatment: The workpiece is placed in a chromium-free passivating agent, and a passivation film is formed on the coating surface; S62: Passivation cleaning: Rinse twice with deionized water to remove residual passivation solution; S63: Drying and Cooling: Drying prevents water stains and improves coating stability, while cooling yields the final product.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a rare earth-modified copper-nickel alloy and its electroplating process. By precisely adding La element to a Cu-La master alloy, the La element refines the copper-nickel alloy grains, purifies grain boundaries, reduces pitting corrosion sources and intergranular corrosion channels, and improves the corrosion resistance of the substrate by 30-40%. The vacuum induction melting process controls rare earth burn-off, and the electroplating parameters are optimized to ensure coating uniformity. It is suitable for industrial mass production and solves the problems of existing copper-nickel alloys having coarse grains and grain boundary impurities in the matrix structure, which easily lead to intergranular corrosion and pitting corrosion, resulting in a high corrosion rate. At the same time, the unreasonable addition of rare earth elements in copper-nickel alloys easily leads to rare earth burn-off and compositional segregation, making it difficult to fully play the role of refining grains and purifying grain boundaries.

[0015] 2. The present invention provides a rare earth modified copper-nickel alloy and its electroplating process. Through the rare earth modified substrate and double-layer electroplating protection, the corrosion rate of the alloy is reduced. The pre-plated nickel layer forms a good transition with the substrate and the Cu-Ni alloy layer, and the bonding force is improved to level 1 or above. The main coating is dense and defect-free, effectively blocking the penetration of corrosive media. This solves the problems of existing copper-nickel alloy substrates being directly exposed to corrosive media, where the oxide film is easy to fall off and break, resulting in limited protective effect. In the electroplating process, the bonding force between the substrate and the coating is insufficient, leading to peeling and flaking. Furthermore, the coating has poor density and cannot effectively block the penetration of corrosive media. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In order to solve existing technical problems, such as Figure 1 As shown, the following preferred technical solutions are provided: A rare earth modified copper-nickel alloy comprises, by mass percentage, the following components: Ni: 14%~16%; Fe: 3%~5%; Mn: 0.5%~1.5%; La: 0.1%~0.3%; impurities are strictly controlled, with the balance being Cu. La is added in the form of a Cu-La master alloy, with the La content of the Cu-La master alloy being 25%. La can strengthen grain boundaries, improve oxide film adhesion, and reduce corrosion rate.

[0019] To further illustrate the above embodiments, the present invention also provides an implementation scheme: a rare earth modified copper-nickel alloy and its electroplating process, comprising the following steps: Step 1: Raw material pretreatment: Prepare electrolytic Cu, electrolytic Ni, pure Fe, pure Mn and Cu-La intermediate alloy, grind the surface, bake to remove oil and moisture. Grind the surface of all raw materials to remove oxide scale, and bake at 150-200℃ to remove oil and moisture. Step 2: Smelting process: The raw materials are melted, rare earth elements are added, and then the mixture is cast. Step 3: Pretreatment: Cleaning and activation of rare earth modified copper-nickel alloy; Step 4: Pre-plating with nickel: Use Watt's nickel plating solution for pre-plating to form a dense transition layer, then rinse. This pre-plating serves as the base layer. Watt's nickel plating is performed at pH 4.0-4.6, temperature 50-60℃, and current density 1-2 A / dm³. 2 The time is 5-10 minutes to form a dense transition layer, which prevents diffusion between the substrate and the coating, improves the adhesion and corrosion resistance, and forms a dense nickel transition layer with a thickness of 1-3 μm on the surface of the workpiece. After removal, rinse twice with deionized water. Step 5: Plating Cu-Ni alloy layer: The main body is corrosion resistant, the composition matches the substrate, and the internal stress is small. A Cu-Ni alloy layer with a thickness of 5-15μm is formed on the surface of the pre-plated nickel layer. After removal, rinse with deionized water 3 times. Step 6: Post-treatment: Rinse and passivate, then dry to improve stability.

[0020] 2. An electroplating process for a rare earth modified copper-nickel alloy as described in claim 1, characterized in that the smelting process includes the following steps: Step 1: Batching and loading: Weigh out electrolytic Cu, electrolytic Ni, and pure Fe according to the above component ratios and load them into the crucible of the vacuum induction furnace; Step 2: Vacuuming and Melting: Start the vacuum system and evacuate the furnace to a vacuum level of 0.5-1.0 Pa. Raise the temperature to 1480-1520℃ to completely melt the raw materials. Step 3: Refining: Refining for 20 minutes, followed by vacuum degassing and impurity removal; Step 4: Add Mn and rare earth elements: Purge with argon to 3-4 × 10⁻⁴ 4 Pa, add Mn, cool to 1250-1300℃, add Cu-La master alloy wrapped with Ni foil, stir at high power for less than 5 minutes to reduce oxidation, add in the form of master alloy to avoid rare earth burn-off and component segregation, the rare earth content is controlled at ppm level, excessive amount will form brittle phase and reduce toughness. Step 5: Casting and heat treatment: Heat to 1360±10℃, cast under argon protection, place the ingot at 900-950℃ for homogenization heat treatment for 4-6 hours, and cool to room temperature with the furnace to obtain rare earth modified copper-nickel alloy matrix.

[0021] Preprocessing includes the following steps: Step 1: Chemical degreasing: Immerse the rare earth modified copper-nickel alloy workpiece in an alkaline degreasing agent at 60-80℃ for 10-15 minutes to remove oil stains and organic impurities. Step 2: Pickling and activation: 10-15% H2SO4, room temperature, 1-3 min, to remove oxide scale, activate the surface, and enhance the adhesion of the coating; Step 3: Ultrasonic rinsing: Ultrasonic cleaning followed by deionized water rinsing to thoroughly remove residue and avoid coating defects.

[0022] The formula for the alkaline degreasing agent used in the pretreatment step is as follows: prepared with pure water, NaOH 50-60g / L, Na2CO3 20-30g / L, Na3PO4 30-40g / L.

[0023] The formula for the Watt nickel plating solution used in the pre-plating nickel step is: pure water, NiSO4 6H₂O₂ 250-300g / L, NiCl₂ 6H2O40-60g / L, H3BO335-45g / L.

[0024] The plating solution formula used for plating Cu-Ni alloy layers is as follows: Sodium citrate complexing agent: 80-120 g / L; H3BO3: 30-40g / L; Sodium dodecyl sulfate wetting agent: 0.05-0.1 g / L; Saccharin brightener: 0.5-1.0g / L.

[0025] This plating solution has a pH of 7.0-8.0, making it an alkaline system. This results in a more uniform and corrosion-resistant coating, forming a uniform, dense, and defect-free Cu-Ni alloy layer that blocks corrosive media. The coating composition matches the substrate, resulting in low internal stress, strong adhesion, and an oxide film structure that enhances film density and adhesion. The Cu-Ni alloy layer thickness is ≥10μm, ensuring long-term corrosion resistance.

[0026] Post-processing includes the following steps: Step 1: Passivation treatment: Immerse the workpiece in a chromium-free passivating agent at room temperature for 1-3 minutes to form a passivation film on the coating surface, further improving corrosion resistance; Step 2: Passivation cleaning: Rinse twice with deionized water to remove residual passivation solution; Step 3: Drying and cooling: The drying temperature is 80-100℃, and the time is 10-15 minutes to prevent water stains and improve the stability of the coating. After cooling, the final product is obtained.

[0027] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0028] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A rare earth-modified copper-nickel alloy, characterized in that, This rare earth-modified copper-nickel alloy comprises the following components by weight percentage: Ni: 14%~16%; Fe: 3%~5%; Mn: 0.5%~1.5%; La: 0.1%~0.3%; Impurities are strictly controlled, with the balance being Cu. La is added in the form of a Cu-La master alloy, and the La content of the Cu-La master alloy is 25%. The steps for producing this rare-earth modified copper-nickel alloy and its electroplating process are as follows: S1: Raw material pretreatment: Prepare electrolytic Cu, electrolytic Ni, pure Fe, pure Mn and Cu-La master alloy, grind the surface, bake to remove oil and moisture; S2: Smelting process: charge the materials, melt them, add rare earth elements, and then cast them; S3: Pretreatment: Cleaning and activation of rare earth modified copper-nickel alloy; S4: Pre-plating nickel: Use Watt's nickel plating solution for base plating to form a dense transition layer and then rinse; S5: Cu-Ni alloy plating: The main body is corrosion resistant, and a Cu-Ni alloy layer is formed on the surface of the pre-plated nickel layer and then rinsed. S6: Post-treatment: Rinsing and passivation treatment, drying to improve stability.

2. An electroplating process for a rare earth modified copper-nickel alloy as described in claim 1, characterized in that, The smelting process includes the following steps: S21: Batching and loading: Weigh out electrolytic Cu, electrolytic Ni, and pure Fe according to the above component ratios and load them into the crucible of the vacuum induction furnace; S22: Vacuuming and Melting: Start the vacuum system and heat up to completely melt the raw materials; S23: Refining: Refining for a period of time, followed by vacuum degassing and impurity removal; S24: Add Mn and rare earth elements: Add Mn after argon purging, add Cu-La master alloy, stir with high power to reduce oxidation, add in the form of master alloy to avoid rare earth burn-off and component segregation; S25: Casting and heat treatment: Casting is carried out under heating and argon protection. The ingot is homogenized by heat treatment and then cooled to room temperature in the furnace to obtain a rare earth modified copper-nickel alloy matrix.

3. An electroplating process for a rare earth modified copper-nickel alloy as described in claim 2, characterized in that, The preprocessing includes the following steps: S31: Chemical degreasing: Place the rare earth modified copper-nickel alloy workpiece in an alkaline degreasing agent to remove oil stains and organic impurities; S32: Pickling and activation: H2SO4 removes oxide scale, activates the surface, and enhances the adhesion of the coating; S33: Ultrasonic rinsing: Ultrasonic cleaning plus deionized water rinsing to thoroughly remove residue and avoid coating defects.

4. An electroplating process for a rare earth modified copper-nickel alloy as described in claim 3, characterized in that, The alkaline degreasing agent used in the pretreatment step has the following formula: pure water, NaOH 50–60 g / L, Na2CO3 20–30 g / L, Na3PO4 30–40 g / L.

5. An electroplating process for a rare earth modified copper-nickel alloy as described in claim 4, characterized in that, The formula for the Watt nickel plating solution used in the pre-plating nickel step is: prepared with pure water, NiSO4... 6H₂O₂ 250-300g / L, NiCl₂ 6H2O40–60g / L, H3BO335–45g / L.

6. An electroplating process for a rare earth modified copper-nickel alloy as described in claim 5, characterized in that, The plating solution formula used for plating the Cu-Ni alloy layer is as follows: Sodium citrate complexing agent: 80–120 g / L; H3BO3: 30–40 g / L; Sodium dodecyl sulfate wetting agent: 0.05–0.1 g / L; Saccharin brightener: 0.5–1.0 g / L. This plating solution has a pH of 7.0–8.0, an alkaline system, resulting in a more uniform and corrosion-resistant coating. It forms a uniform, dense, and defect-free Cu-Ni alloy layer, blocking corrosive media. The coating composition matches the substrate, resulting in low internal stress, strong adhesion, and a well-structured oxide film that enhances film density and adhesion. The Cu-Ni alloy layer thickness is ≥10 μm, ensuring long-term corrosion resistance.

7. An electroplating process for a rare earth modified copper-nickel alloy as described in claim 6, characterized in that, The post-processing includes the following steps: S61: Passivation treatment: The workpiece is placed in a chromium-free passivating agent, and a passivation film is formed on the coating surface; S62: Passivation cleaning: Rinse twice with deionized water to remove residual passivation solution; S63: Drying and Cooling: Drying prevents water stains and improves coating stability, while cooling yields the final product.

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