A short process preparation method of high-strength high-conductivity Cu-Ag-Sn copper alloy

Abstract

This invention discloses a short-process preparation method for a high-strength, high-conductivity Cu-Ag-Sn copper alloy, belonging to the technical field of high-performance copper alloy materials. The alloy, by mass percentage, comprises: Ag: 0.03%–0.05%, Sn: 0.005%–0.05%, total impurities ≤0.01%, and the balance being Cu. The preparation method completely abandons the traditional homogenization annealing and solution treatment processes, comprising only three core steps: continuous casting to obtain an alloy ingot; cold drawing deformation of the ingot with a total deformation of 75%–85%; and subsequent anomalous hardening annealing at 240℃–260℃ for 30–120 minutes. The alloy prepared by this invention exhibits a unique anomalous hardening effect, with a "hardness after annealing higher than in the cold-drawn state," and its Vickers hardness is increased by 1.2%–10.0% compared to the cold-drawn state, while maintaining a conductivity above 97% IACS. This method is extremely simple, energy-efficient, and cost-effective. The resulting alloy has comprehensive properties similar to the traditional Cu-0.08Ag alloy and can replace the latter in precision conductive structural components such as high-end connectors, lead frames, and commutators.

Description

Technical Field

[0001] This invention relates to the field of high-performance copper alloy materials technology, specifically to an ultra-short process preparation method for high-strength, high-conductivity Cu-Ag-Sn copper alloys that can replace traditional Cu-Ag alloys. Background Technology

[0002] High-strength, high-conductivity copper alloys are indispensable key materials in fields such as electronics, electrical engineering, new energy vehicles, and high-end communications. Among them, silver-containing copper alloys (such as Cu-0.08Ag) are widely used in precision components such as commutators, lead frames, and connectors due to their excellent conductivity and improved strength. However, silver is a precious metal, and its addition significantly increases material costs; moreover, my country's silver resources are relatively scarce. Therefore, developing new copper alloys that can reduce silver content while maintaining or improving overall performance has become an urgent industry need.

[0003] The preparation of traditional high-performance copper alloys (such as Cu-Cr-Zr, Cu-Ni-Si, Cu-Fe, etc.) typically relies on complex deformation heat treatment processes, including lengthy steps such as homogenization annealing, solution treatment, cold deformation, and aging, to control precipitates and achieve strengthening. These pretreatment processes are energy-intensive, lengthy, and costly. For microalloyed systems, homogenization and solution treatment are considered essential steps to obtain a homogeneous supersaturated solid solution. Furthermore, conventional understanding holds that low-temperature annealing after cold deformation usually leads to material recovery or even recrystallization, resulting in a decrease in strength and hardness (softening) in exchange for the recovery of plasticity and conductivity. How to achieve performance breakthroughs, especially the discovery of new performance evolution patterns, while simplifying the process is a major challenge for those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a short-process preparation method for a high-strength, high-conductivity Cu-Ag-Sn copper alloy. This alloy, with extremely low Ag and Sn composite microalloying, completely eliminates the need for homogenization and solution treatment. Through a specific process, it not only achieves performance replacement and surpasses that of traditional Cu-0.08Ag alloys, but also discovers for the first time in this system a unique phenomenon of "abnormal increase in hardness after low-temperature annealing," thus obtaining a novel copper alloy material with an extremely simple process, lower cost, and superior overall performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a short-process preparation method for a high-strength, high-conductivity Cu-Ag-Sn copper alloy, wherein the alloy, by mass percentage, has the following chemical composition: Ag: 0.03%–0.05%, Sn: 0.005%–0.05%, unavoidable total impurities ≤0.01%, and the balance being Cu. The preparation method includes the following steps:

[0007] (1) Upward continuous casting: using copper, silver and tin granules as raw materials, Cu-Ag-Sn alloy rods are obtained by upward continuous casting.

[0008] (2) Direct cold drawing deformation: The alloy casting rod obtained in step (1) is directly subjected to 2-X cold drawing deformations without any intermediate heat treatment, with a section reduction rate of 75% to 85%, to obtain cold drawn wire or rod.

[0009] (3) Abnormal hardening annealing: The cold-drawn material obtained in step (2) is annealed at 240℃~260℃ for 30~120 minutes, followed by air cooling or water cooling.

[0010] Preferably, the casting temperature in step (1) is 1135-1165℃.

[0011] Preferably, the pitch of the upper continuous casting rod in step (1) is 2-5 mm.

[0012] Preferably, the upward continuous casting speed in step (1) is 700-900 mm / min when the copper rod diameter is 12 mm; 500-630 mm / min when the copper rod diameter is 15-18 mm; and 350-400 mm / min when the copper rod diameter is 20 mm.

[0013] Preferably, the section reduction rate in step (2) is 80-85%.

[0014] Preferably, the annealing temperature in step (3) is 248℃~252℃, and the holding time is 50~70 minutes.

[0015] Secondly, the present invention provides a high-strength, high-conductivity Cu-Ag-Sn copper alloy material prepared by the above method, the hardness of which after annealing in step (3) is higher than the hardness of which after cold drawing in step (2), and the conductivity is not less than 97% IACS.

[0016] The beneficial effects of this invention are:

[0017] (1) Novel composition design and significant cost advantage: The composite microalloying of Ag and Sn is adopted, with a total addition amount of extremely low (≤0.1%). While significantly saving the amount of expensive silver, the performance is optimized through the synergistic effect of elements, providing a low-cost solution to replace the traditional Cu-0.08Ag alloy.

[0018] (2) Revolutionary simplification of process flow: This invention completely eliminates the energy-consuming and time-consuming homogenization annealing and solution treatment processes. The process flow is shortened to three steps: "upward continuous casting - cold drawing - annealing", which greatly reduces production energy consumption (expected to be reduced by more than 30%) and equipment investment, improves production efficiency, and has outstanding industrial application value and economic benefits.

[0019] (3) Discovery and utilization of the “abnormal hardening effect”: The most core innovation of this invention lies in the discovery that the alloy of this specific composition exhibits an abnormal phenomenon of “hardness increasing instead of decreasing after low-temperature annealing” under a specific short-process technology. The hardness of the annealed alloy can be increased by 1.2% to 10.0% compared to the cold-drawn state, which completely overturns the traditional material science understanding that “annealing leads to softening” and brings unique performance advantages to the alloy of this invention.

[0020] (4) Excellent overall performance: Thanks to the anomalous hardening effect, the alloy of the present invention has both higher hardness and high conductivity (conductivity ≥97% IACS) after annealing. Its overall performance is no less than that of the traditional Cu-0.08Ag alloy, which fully meets the requirements of high-end precision conductive components.

[0021] (5) Unique Strengthening Mechanism: This invention proposes that its anomalous hardening mechanism originates from the unique microstructure formed by the short-process technology. During the large deformation cold drawing process, the microalloying elements in the alloy interact strongly with the generated high-density dislocations, deformation bands, and other defects, and Ag and Sn atoms are "mechanically" captured and enriched around the defects. Subsequent annealing at a specific temperature provides short-range diffusion and ordering kinetics for these Ag-Sn solute atom clusters in a high-energy state, forming extremely fine nanoscale particle phases in situ at the defects, resulting in strong age-hardening. This additional pinning strengthening superimposed on the partially recovered matrix ultimately leads to a net increase in strength. Attached Figure Description

[0022] Figure 1 The images show a TEM comparison of the alloy in Example 2 of this invention in the cold-drawn state (a) and the annealed state at 250℃ / 1h (b). Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Example

[0024] Raw materials were weighed according to the following mass percentages: Ag: 0.03%, Sn: 0.005%, with the balance being high-purity cathode copper (Cu≥99.99%). A Φ20mm casting rod was prepared using the upward continuous casting method.

[0025] The cast rod was subjected to eight cold drawing passes without any heat treatment, resulting in a wire diameter of 8mm and a total deformation of 84%. A portion of the wire was taken as a cold-drawn sample.

[0026] The remaining cold-drawn wire was annealed in an air furnace at 250°C for 1 hour, followed by quenching and water cooling to obtain annealed samples. Example

[0027] The raw materials were weighed according to the following mass percentages: Ag: 0.03%, Sn: 0.03%, with the balance being high-purity cathode copper. The preparation and processing technology was the same as in Example 1. Example

[0028] The raw materials were weighed according to the following mass percentages: Ag: 0.03%, Sn: 0.05%, with the balance being high-purity cathode copper. The preparation and processing techniques were the same as in Example 1. Example

[0029] The raw materials were weighed according to the following mass percentages: Ag: 0.05%, Sn: 0.03%, with the balance being high-purity cathode copper. The preparation and processing techniques were the same as in Example 1.

[0030] Raw materials were weighed by mass percentage: Ag: 0.08%, with the balance being high-purity cathode copper. The conventional process was employed: upward continuous casting → homogenization annealing at 850℃ for 8 hours → solution treatment at 780℃ for 1 hour (water quenching) → cold drawing using the same process (84% deformation) → annealing at 250℃ for 1 hour.

[0031] Performance testing:

[0032] The hardness and conductivity of the cold-drawn and annealed samples from Examples 1-3, as well as the annealed sample from Comparative Example 1, were tested respectively. The results are recorded in Table 1.

[0033] Table 1. Comparison of alloy properties between the examples and comparative examples Results analysis:

[0034] From Table 1 and Figure 1 It can be known that:

[0035] 1. Alloys in Examples 1-4 of this invention, after undergoing the same annealing at 250℃ / 1h, all exhibit significantly higher hardness than their cold-drawn state, achieving an "abnormal hardness enhancement" with an enhancement range of 1.2% to 10.0%.

[0036] 2. Although the total Ag content (≤0.08%) of the alloy of the present invention is lower than that of the Cu-0.08Ag alloy of Comparative Example 1, its comprehensive performance after annealing is similar to that of Comparative Example 1, and its raw material price advantage is obvious.

[0037] 3. Regarding conductivity, the conductivity of the alloy of the present invention after annealing is restored to 97.4% to 97.9% IACS. Although it is slightly lower than that of Comparative Example 1 of Cu-0.08Ag alloy (99% IACS), it still remains at an extremely high level, fully meeting the requirements of most high-strength and high-conductivity application scenarios, and achieving an excellent balance between strength and conductivity.

[0038] Figure 1 The results showed that the alloy of Example 1 had an extremely high dislocation density in the cold-drawn state (a); while after annealing at 250°C (b), the dislocation density hardly decreased (only recovery occurred), but at the same time, a large number of nanoscale fine precipitates were uniformly dispersed in the matrix (shown by red circles in the figure), which provided direct microstructural evidence for the anomalous hardening effect.

[0039] In summary, this invention, through unique composition design and revolutionary short-process technology, successfully prepared a high-performance Cu-Ag-Sn alloy with "abnormal hardening effect." Its comprehensive mechanical properties are similar to those of the traditional Cu-0.08Ag alloy, but its production process is shorter and the cost is lower, giving it enormous market application potential.

[0040] The above description is merely 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 method for preparing a Cu-Ag-Sn copper alloy, characterized in that, The chemical composition, by mass percentage, is as follows: Ag: 0.03%–0.05%, Sn: 0.005%–0.05%, unavoidable total impurities ≤0.01%, and the balance is Cu. The preparation method includes the following steps: (1) Upward continuous casting: using copper, silver and tin granules as raw materials, Cu-Ag-Sn alloy rods are obtained by upward continuous casting. (2) Direct cold drawing deformation: The alloy casting rod obtained in step (1) is subjected to 2-8 passes of cold drawing deformation without any intermediate heat treatment, with a total deformation of 75% to 85%, to obtain cold-drawn wire or rod. (3) Abnormal hardening annealing: The cold-drawn material obtained in step (2) is annealed at 240℃~260℃ for 30~120 minutes, and then quenched and water-cooled to room temperature; The absence of any intermediate heat treatment in step (2) means that no heat treatment is applied to the material to change its microstructure or solute distribution after the upper continuous casting step and before the anomalous hardening annealing step.

2. The preparation method according to claim 1, characterized in that, In step (1), the casting temperature of the upward continuous casting is 1135-1165℃, and the pitch of the casting rod is 2-5mm.

3. The preparation method according to claim 1, characterized in that, In step (1), when the diameter of the copper rod is 12mm, the upward continuous casting speed is 700-900mm / min; when the diameter of the copper rod is 15-18mm, the upward continuous casting speed is 500-630mm / min; and when the diameter of the copper rod is 20mm, the upward continuous casting speed is 350-400mm / min.

4. The preparation method according to claim 1, characterized in that, In step (3), the annealing temperature is 248℃~252℃ and the holding time is 50~70 minutes.

5. The preparation method according to claim 1, characterized in that, The step (2) of not undergoing any intermediate heat treatment also includes not performing homogenization heat treatment and solution heat treatment.

6. A high-strength, high-conductivity Cu-Ag-Sn copper alloy material prepared by the method according to any one of claims 1 to 5.

7. The Cu-Ag-Sn copper alloy material according to claim 6, characterized in that, The conductivity of the alloy material is not less than 97% IACS.

8. The Cu-Ag-Sn copper alloy material according to claim 6 or 7, characterized in that, The alloy has the composition of Cu-0.05Ag-0.03Sn.

9. The alloy material according to claim 8, characterized in that, The alloy material has an HV hardness of 124 or higher.

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