A copper-nickel-tin alloy strip and a method of producing the same

Abstract

The application discloses a copper-nickel-tin alloy strip and a preparation method thereof, and relates to the technical field of copper alloys. The application provides a preparation method of a copper-nickel-tin alloy strip. Through a whole-process technology of ball-milling mixing-powder canning hot extrusion-pre-rolling-overaging-large deformation rolling-stress relief annealing, macroscopic segregation of the alloy is eliminated from the source, and uniformity of alloy components and structures is ensured.

Description

Technical Field

[0001] This application relates to the field of copper alloy technology, and in particular to a copper-nickel-tin alloy strip and its preparation method. Background Technology

[0002] Copper-nickel-tin (Cu-Ni-Sn) alloys possess high strength, high elasticity, and high wear resistance, making them one of the ideal materials to replace beryllium copper alloys. They have broad application prospects in high-end manufacturing fields such as precision connectors, radio frequency devices, and aerospace elastic components. As electronic components develop towards miniaturization, ultra-thinness, and high reliability, stringent requirements are placed on Cu-Ni-Sn alloys for ultra-thin dimensions, ultra-high strength, and high conductivity, which traditional manufacturing techniques can no longer meet.

[0003] Currently, the industrial production of Cu-Ni-Sn alloys still relies primarily on traditional casting processes. During solidification, macroscopic segregation of Sn and coarse dendrites easily occur, leading to poor uniformity in alloy composition and properties. Subsequent multiple plastic deformation and heat treatment processes are required to improve the microstructure, resulting in a lengthy process, high energy consumption, and low yield. While powder metallurgy can mitigate compositional segregation at the source, existing Cu-Ni-Sn powder metallurgy routes mostly employ hot pressing or hot extrusion combined with conventional aging, or traditional cold rolling followed by aging. The strengthening mechanism is mainly based on continuous precipitates generated by amplitude modulation decomposition. While these methods improve strength, they also cause supersaturation of matrix solute atoms and significant solid solution scattering effects, resulting in a substantial decrease in conductivity, typically only 8-10% IACS, making it difficult to achieve a synergistic balance between ultra-high strength and high conductivity.

[0004] Therefore, this application is submitted. Summary of the Invention

[0005] Based on this, the purpose of this application is to overcome the shortcomings of the prior art and provide an ultra-high strength, high conductivity, ultra-thin, and uniformly structured copper-nickel-tin alloy strip and its preparation method.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: a method for preparing copper-nickel-tin alloy strip, comprising the following steps: S1. Ball mill Cu powder, Ni powder, and Sn powder and mix them evenly to obtain alloyed powder; S2. The alloyed powder is encapsulated to obtain an alloyed powder blank. The alloyed powder blank is hot-extruded and then cooled to remove the encapsulation, resulting in an extruded blank. S3. The extruded billet is pre-rolled to obtain a pre-deformed billet; S4. The pre-deformed billet is subjected to over-aging treatment and cooled to obtain an over-aged billet; S5. The over-aged billet is subjected to large deformation rolling to obtain strip; S6. The strip is subjected to stress-relief annealing to obtain a copper-nickel-tin alloy strip.

[0007] This application utilizes a complete process—ball milling, powder-clad hot extrusion, pre-rolling, over-aging, large deformation rolling, and stress-relief annealing—to eliminate macroscopic segregation in the alloy at its source, ensuring the uniformity of alloy composition and microstructure. Specifically, pre-rolling introduces numerous dislocations, slip bands, and grain boundary distortions. The precipitates obtained from the over-aging process are discontinuous cellular / lamellar structures. Pre-rolling and over-aging induce discontinuous precipitation, significantly reducing the solute atom concentration in the matrix to improve conductivity. Large deformation rolling controls the morphology distribution of discontinuous precipitates, achieving ultra-high strength through the synergistic strengthening of dislocations and discontinuous precipitated nanofibers. The copper-nickel-tin alloy strip prepared in this application exhibits a tensile strength ≥1200 MPa, conductivity ≥15% IACS, and thickness ≤0.05 mm, combining ultra-thinness, ultra-high strength, and high conductivity. The process is streamlined and highly controllable.

[0008] In some embodiments of this application, the Cu powder, Ni powder, and Sn powder are prepared by gas atomization. The raw materials used for gas atomization powder preparation are copper plates, nickel plates, and tin ingots with a purity of ≥99.9%. The raw materials are cleaned to remove surface oil and prevent the introduction of impurities.

[0009] In some embodiments of this application, the Cu melt temperature is 1200-1300℃, the Ni melt temperature is 1550-1650℃, the Sn melt temperature is 300-400℃, the atomizing medium is argon or nitrogen, and the atomizing pressure is 4.0-6.0MPa.

[0010] In some embodiments of this application, in step S1, the purity of the Cu powder, Ni powder, and Sn powder is ≥99.9%.

[0011] In some embodiments of this application, in step S1, the average particle size D50 of the Cu powder, Ni powder, and Sn powder is 10-15 μm.

[0012] In some embodiments of this application, in step S1, the Ni powder has a mass percentage content of 8-16% and the Sn powder has a mass percentage content of 5-9% based on the total mass of the alloying powder, with the remainder being Cu powder.

[0013] In some embodiments of this application, in step S1, the ball milling speed is 200-300 r / min, the ball milling time is 8-20 h, the ball milling is carried out under argon, nitrogen or vacuum protection, and the ball-to-material ratio is 5:1-15:1.

[0014] In some embodiments of this application, the specific process of the cladding treatment in step S2 is as follows: oxygen-free copper is selected as the cladding substrate, the alloying powder is uniformly loaded into the cladding, and then the cladding is vacuum-treated to ensure a vacuum degree ≤ 1×10⁻⁶. -2 Pa, thoroughly remove air from the casing to prevent powder oxidation during hot extrusion; after vacuuming, use argon arc welding to seal the opening end of the casing, and then mechanically shape it to ensure the casing has a regular shape and avoid stress concentration during extrusion that leads to uneven deformation.

[0015] In some embodiments of this application, in step S2, the sleeve is removed by milling.

[0016] In some embodiments of this application, in step S2, the alloyed powder blank is preheated to 750-950°C and held at that temperature for 2-4 hours.

[0017] In some embodiments of this application, in step S2, during the hot extrusion molding, the extrusion die is preheated to 500-700°C, the extrusion ratio is 10:1-20:1, and the extrusion rate is 5-15 mm / s.

[0018] In some embodiments of this application, in step S2, the cooling rate is ≥100℃ / s; wherein, after extrusion, the billet is immersed in a cooling medium for rapid cooling, and the cooling medium is water or rapid quenching oil.

[0019] The hot extrusion molding process described above is used in S2 of this application. It can ensure that the billet temperature is uniform and avoid deformation and cracking caused by excessive temperature difference between the billet and the mold. At the same time, the subsequent rapid cooling can effectively inhibit grain growth and premature precipitation of solute elements, obtain fine-grained structure, and retain sufficient supersaturated solid solubility, creating the best conditions for subsequent over-aging treatment.

[0020] In some embodiments of this application, in step S3, the total deformation of the pre-rolling is 30-50%.

[0021] In S3 of this application, the pre-rolling process introduces a large number of dislocations, slip bands, and grain boundary distortions, thereby increasing the discontinuous precipitation nucleation rate and shortening the long-term aging induction period.

[0022] In some embodiments of this application, in step S4, the temperature of the over-aging treatment is 400-550°C, and the holding time is 12-36 hours.

[0023] In S4 of this application, the over-aging treatment induces the generation of discontinuous cellular / lamellar precipitates, which significantly desolvate the matrix and improve conductivity.

[0024] In some embodiments of this application, in step S5, the total deformation of the large deformation rolling is ≥95%, and the thickness of the strip is ≤0.05mm.

[0025] In S5 of this application, the large deformation rolling modulates the discontinuous precipitates into a nanofiber-like directional arrangement to achieve strong conduction synergy.

[0026] In some embodiments of this application, in step S6, the stress-relief annealing temperature is 200-300°C and the belt speed is 10-20 m / min.

[0027] In a second aspect of this application, this application provides a method for preparing copper-nickel-tin alloy strip to obtain copper-nickel-tin alloy strip.

[0028] In a third aspect, this application provides the application of the copper-nickel-tin alloy strip in the manufacture of precision connectors, radio frequency components, and elastic components.

[0029] Compared with the prior art, the beneficial effects of this application are as follows: This application uses powder metallurgy process to avoid the macroscopic segregation and coarse dendrite problems caused by traditional casting; The copper-nickel-tin alloy strip prepared by this application has a tensile strength ≥1200MPa, conductivity ≥15%IACS, and thickness ≤0.05mm, and has the characteristics of ultra-thinness, ultra-high strength, and high conductivity; The preparation method of copper-nickel-tin alloy strip provided by this application has a simplified process flow, strong controllability, low energy consumption, and moderate cost, and is suitable for industrial mass production. Attached Figure Description

[0030] Figure 1 The image shows the SEM image of the extruded billet microstructure obtained in Example 1. Figure 2 The image shows the SEM image of the microstructure of the copper-nickel-tin alloy strip obtained in Example 1. Detailed Implementation

[0031] To better illustrate the purpose, technical solution, and advantages of this application, the following description, in conjunction with the accompanying drawings and specific embodiments, will further explain this application. The purpose is to provide a detailed understanding of the content of this application, not to limit it. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this application. Unless otherwise specified, the experimental reagents and instruments designed in the embodiments and comparative examples of this application are commonly used reagents and instruments, all of which are commercially available. Unless otherwise specified, the experimental methods used in the embodiments and comparative examples are conventional methods; and unless otherwise specified, the raw materials used in parallel experiments are from the same batch.

[0032] The raw materials used in specific embodiments of this application are described below, but are not limited to the following raw materials: Copper plate (Jiangxi Copper Co., Ltd.), nickel plate (Tianjin Haoyuan Metal Materials Co., Ltd.), tin ingot (Suzhou Haichuan Rare Metals Products Co., Ltd.): purity ≥ 99.9%.

[0033] Example 1 A method for preparing a copper-nickel-tin alloy strip includes the following steps: S1. Copper plates, nickel plates, and tin ingots with a purity ≥ 99.9% are cleaned and then powdered by gas atomization to obtain Cu powder, Ni powder, and Sn powder, respectively; melt temperature: Cu 1250℃, Ni 1600℃, Sn 350℃, atomization medium is nitrogen, atomization pressure is 5.0MPa, and the average particle size of the powder after sieving is 15μm; Cu powder, Ni powder, and Sn powder were weighed according to the mass percentages of Ni 9%, Sn 6%, and the balance Cu, and then ball-milled and mixed. The ball-to-powder ratio was 10:1, the ball milling speed was 200 r / min, and the ball milling time was 15 h to obtain alloyed powder. S2. The alloyed powder is encapsulated to obtain an alloyed powder blank. The alloyed powder blank is hot-extruded and then cooled to remove the encapsulation, resulting in an extruded blank. The specific process for cladding is as follows: Oxygen-free copper is selected as the cladding substrate. The alloying powder is uniformly packed into the cladding, and then the cladding is vacuumed to 5×10⁻⁶. -3 Pa, the opening end of the sheath is sealed by argon arc welding, and then mechanically shaped after welding.

[0034] The hot extrusion process is as follows: the alloyed powder billet is preheated to 850°C and held for 2 hours, the extrusion die is preheated to 600°C, the extrusion ratio is 15:1, and the extrusion rate is 10 mm / s.

[0035] Immediately after extrusion, the billet is immersed in water for rapid cooling at a rate of 120℃ / s; the extruded billet is then obtained by milling and turning to remove the shroud. S3. The extruded billet is pre-rolled with a deformation of 40% to obtain a pre-deformed billet; S4. The pre-deformed billet is subjected to an aging treatment at a temperature of 480°C for 24 hours. After being removed and cooled to room temperature, an over-aged billet is obtained. S5. The over-aged billet is subjected to large deformation rolling with a total deformation of 96% to obtain a strip with a thickness of 0.045 mm. S6. The strip is subjected to stress-relief annealing at a temperature of 250°C and a conveying speed of 15 m / min to obtain a copper-nickel-tin alloy strip.

[0036] Example 2 Compared with Example 1, the differences are as follows: the melt temperature in step S1 is different, Cu is 1280℃, Ni is 1580℃, Sn is 370℃, the atomizing medium is argon, the atomizing pressure is 4.5 MPa, and the particle size after powder sieving is 12μm; the extrusion ratio in step S2 is 18:1, and the cooling medium is rapid quenching oil; the stress-relief annealing temperature in step S6 is 280℃, and the conveyor belt speed is 20m / min; the remaining components, weight parts, and preparation methods are exactly the same.

[0037] Example 3 Compared with Example 1, the differences are as follows: in step S1, the ball-to-material ratio is 12:1, the ball milling speed is 250 r / min, and the ball milling time is 12 h; in step S2, the casing is evacuated to 8 × 10⁻⁶. -3 Pa, the billet is preheated to 880℃ and held for 2.5h; in step S4, the pre-deformed billet undergoes over-aging treatment, the over-aging treatment process being held at 520℃ for 18h; in step S5, the total deformation during rolling is 97%, resulting in a strip with a thickness of 0.042mm. The remaining components, weight parts, and preparation methods are completely identical.

[0038] Example 4 Compared with Example 1, the differences are as follows: in step S1, the powder ratio is 10% Ni, 8% Sn, and the balance is Cu; in step S2, the extrusion rate is 8 mm / s and the extrusion ratio is 12:1; in step S4, the pre-deformed billet undergoes an over-aging treatment, which involves holding at 500°C for 32 h; in step S5, the total deformation during rolling is 97%, resulting in a strip with a thickness of 0.042 mm. The remaining components, weight parts, and preparation methods are completely identical.

[0039] Example 5 Compared with Example 1, the differences are as follows: in step S1, the atomization pressure is 5.5 MPa and the average powder particle size is 10 μm; in step S2, the extrusion die is preheated to 650°C and the extrusion rate is 15 mm / s; in step S3, the pre-rolling deformation is 30%; and in step S4, the pre-deformed billet undergoes an over-aging treatment, wherein the over-aging treatment process involves holding at 400°C for 36 h. The remaining components, weight parts, and preparation methods are completely identical.

[0040] Comparative Example 1 The only difference from Example 1 is that the encapsulation process is omitted, and the alloyed powder is directly hot-extruded. The remaining components, weight parts, and preparation methods are exactly the same.

[0041] The copper-nickel-tin alloy strip prepared in Comparative Example 1 showed obvious oxidation on its surface and cracked during the rolling process.

[0042] Comparative Example 2 The only difference from Example 1 is that in S4, the pre-deformed billet is subjected to a conventional aging process at an aging temperature of 400°C and an aging time of 2 hours. The other components, weight parts, and preparation methods are exactly the same.

[0043] Comparative Example 3 The only difference from Example 1 is that: Steps S1 and S2 are exactly the same; S3. The extruded billet is subjected to large deformation rolling with a deformation of 96%, and then conventional aging process is adopted with an aging temperature of 400℃ and an aging time of 2h to obtain strip. S4. The strip is subjected to stress-relief annealing at a temperature of 250°C and a conveying speed of 15 m / min to obtain a copper-nickel-tin alloy strip.

[0044] Comparative Example 4 The only difference from Example 1 is that step S4 is different, in which the pre-deformed billet is subjected to aging treatment at a temperature of 480°C for 8 hours, and then cooled to room temperature to obtain the billet; the remaining components, weight parts and preparation methods are exactly the same.

[0045] Comparative Example 5 The only difference from Example 1 is that step S4 is different, in which the pre-deformed billet is subjected to aging treatment at a temperature of 350°C for 24 hours, and then cooled to room temperature to obtain the billet; the remaining components, weight parts and preparation methods are exactly the same.

[0046] Comparative Example 6 The only difference from Example 1 is that step S3 is different, in which the extruded billet is pre-rolled with a deformation of 20% to obtain a pre-deformed billet; the remaining components, weight parts and preparation methods are exactly the same.

[0047] Comparative Example 7 The only difference from Example 1 is that step S3 is different, in which the extruded billet is pre-rolled with a deformation of 60% to obtain a pre-deformed billet; the remaining components, weight parts and preparation methods are exactly the same.

[0048] Comparative Example 8 The only difference from Example 1 is that the cooling method in step S2 is different, the cooling medium is 10% PVP water-based slow cooling liquid, and the cooling rate is 80℃ / s; the other components, weight parts and preparation methods are exactly the same.

[0049] Performance testing (1) Tensile strength: The room temperature tensile test was conducted using an electronic universal mechanical testing machine, referring to the national standard GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test at room temperature". The surface of the gauge section of the specimen should be flat, free of scratches and oxidation defects. During the tensile test, the separation rate of the testing machine clamps was set to 5 mm / min, and the load was continuously applied until the specimen broke. The maximum test force F was automatically recorded by the testing machine, and the tensile strength R was calculated based on the original cross-sectional area S of the specimen. The calculation formula is R = F / S, and the result is in MPa. The arithmetic mean of three parallel tests was taken as the final test result.

[0050] (2) Conductivity: The conductivity of the strip was determined using an eddy current conductivity meter, referring to the national standard GB / T 32791-2016 "Eddy Current Test Method for Conductivity of Copper and Copper Alloys". During the test, the eddy current probe was vertically coupled to the surface of the copper alloy strip, ensuring that the test location was flat and free of oil, oxide scale, or other non-conductive coatings. An appropriate test frequency was selected according to the actual thickness of the strip, and the conductivity value displayed by the instrument was directly read. The result was expressed as the International Annealed Copper Standard Percentage (%IACS). At least 5 points were measured at different locations for each sample, and the average value was taken after removing the maximum and minimum values.

[0051] (3) Hardness: The hardness was determined using a Vickers hardness tester in accordance with the national standard GB / T 4340.1-2009 "Metallic Materials - Vickers Hardness Test - Part 1: Test Method". During the test, the sample was placed stably on a rigid support table, and a test force was applied at a rate of 0.2 mm / s. After reaching the specified test force, the load was held for 10 s, and then the test force was smoothly removed. The lengths d1 and d2 of the two diagonals of the indentation were measured, and their arithmetic mean d was taken. The Vickers hardness value was calculated using the formula HV = 0.1891 × F / d² (where F is the test force in N; d is the arithmetic mean of the indentation diagonals in mm). The final result was the arithmetic mean of at least 5 valid indentation points.

[0052] The test results are shown in Table 1.

[0053] Table 1 In summary, this invention employs a specific ball milling-powder-clad hot extrusion-pre-rolling-over-aging-large deformation rolling-stress-relief annealing process. Powder metallurgy eliminates the compositional segregation and coarse microstructure problems of traditional casting from the source, ensuring high uniformity of alloy composition and microstructure. Pre-deformation and over-aging induce discontinuous precipitation, significantly reducing the concentration of solute atoms in the matrix and significantly improving conductivity. Large deformation rolling regulates the precipitated phases into a nanofiber-like directional arrangement, forming a synergistic strengthening mechanism of high-density dislocations and nanofibers. Ultimately, it produces ultra-high strength, high conductivity copper-nickel-tin alloy ultrathin strips with tensile strength ≥1200MPa, conductivity ≥15%IACS, and thickness ≤0.05mm.

[0054] Figure 1 The image shows the SEM image of the extruded billet obtained in Example 1. After hot extrusion, the billet was directly water-cooled, and the alloy underwent sufficient dynamic recrystallization, resulting in a microstructure dominated by equiaxed recrystallized grains with a grain size of approximately 10-20 μm. No large amount of coarse second phase was observed inside the matrix, and only a small amount of fine second phase was present at some grain boundaries. The matrix maintained a high degree of supersaturated solid solubility.

[0055] Figure 2 The image shows the SEM image of the copper-nickel-tin alloy strip obtained in Example 1. The alloy was subjected to aging treatment and rolling plastic deformation in sequence after extrusion and water cooling solution treatment. The original equiaxed recrystallized grains were significantly elongated under the action of rolling external force, forming deformed fibrous structure extending along the deformation direction. The complete equiaxed grain outline disappeared, and some precipitated phases were distributed along the rolling deformation streamline. The plastic deformation encapsulated and rearranged the precipitated phases in the deformed matrix.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A method of producing a copper-nickel-tin alloy strip, characterized by, Includes the following steps: S1. Ball mill Cu powder, Ni powder, and Sn powder and mix them evenly to obtain alloyed powder; S2. The alloyed powder is encapsulated to obtain an alloyed powder blank. The alloyed powder blank is hot-extruded and then cooled to remove the encapsulation, resulting in an extruded blank. S3. The extruded billet is pre-rolled to obtain a pre-deformed billet; S4. The pre-deformed billet is subjected to over-aging treatment and cooled to obtain an over-aged billet; S5. The over-aged billet is subjected to large deformation rolling to obtain strip; S6. The strip is subjected to stress-relief annealing to obtain a copper-nickel-tin alloy strip.

2. The method for preparing copper-nickel-tin alloy strip as described in claim 1, characterized in that, In S1, the purity of the Cu powder, Ni powder, and Sn powder is ≥99.9%; And / or, the average particle size D50 of the Cu powder, Ni powder, and Sn powder is 10-15 μm; And / or, based on the total mass of the alloyed powder, the Ni powder has a mass percentage content of 8-16%, the Sn powder has a mass percentage content of 5-9%, and the balance is Cu powder; And / or, the ball milling speed is 200-300 r / min, the ball milling time is 8-20 h, the ball milling is carried out under argon, nitrogen or vacuum protection, and the ball-to-material ratio is 5:1-15:

1.

3. The method for preparing copper-nickel-tin alloy strip as described in claim 1, characterized in that, In step S2, the alloyed powder blank is preheated to 750-950℃ and held at that temperature for 2-4 hours. And / or, in the hot extrusion molding, the extrusion die is preheated to 500-700°C, the extrusion ratio is 10:1-20:1, and the extrusion rate is 5-15 mm / s; And / or, the cooling rate is ≥100°C / s.

4. The method for preparing copper-nickel-tin alloy strip as described in claim 1, characterized in that, In step S3, the total deformation during pre-rolling is 30-50%.

5. The method for preparing copper-nickel-tin alloy strip as described in claim 1, characterized in that, In step S4, the temperature of the over-aging treatment is 400-550℃, and the holding time is 12-36h.

6. The method for preparing copper-nickel-tin alloy strip as described in claim 1, characterized in that, In S5, the total deformation of the large deformation rolling is ≥95%, and the thickness of the strip is ≤0.05mm.

7. The method for preparing copper-nickel-tin alloy strip as described in claim 1, characterized in that, In step S6, the stress-relief annealing temperature is 200-300℃ and the belt speed is 10-20m / min.

8. A copper-nickel-tin alloy strip prepared by the method for preparing copper-nickel-tin alloy strip according to any one of claims 1-7.

9. The application of the copper-nickel-tin alloy strip as described in claim 8 in the manufacture of precision connectors, radio frequency components, and elastic components.

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