A high-strength and high-conductivity copper alloy containing boron and a cryogenic deformation heat treatment method thereof

Abstract

The application relates to the technical field of non-ferrous metal material processing, in particular to a high-strength and high-conductivity copper alloy containing boron and a cryogenic deformation heat treatment method thereof. The cryogenic deformation heat treatment method comprises the following steps: vacuum melting and casting and composite purification, homogenization treatment, hot rolling and quenching, three-stage cryogenic plastic deformation treatment, multi-stage cold rolling and grading aging treatment. The application adopts the process of vacuum melting and casting and composite purification, avoids oxidation by adopting vacuum melting and casting, carries out composite purification by combining ultrasonic vibration and electromagnetic stirring, refines melt grains by ultrasonic vibration, promotes FeB phase dispersion precipitation by electromagnetic stirring, and solves the problem of uneven distribution of impurities in traditional melting and casting.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal material processing technology, specifically to a boron-containing high-strength, high-conductivity copper alloy and its cryogenic deformation heat treatment method. Background Technology

[0002] High-strength, high-conductivity copper alloys play an irreplaceable role in key components such as lead frames, high-end connectors, and rail transit contact lines due to their excellent mechanical and electrical properties. Currently, Cu-Ni-Si alloys widely used in industry are mainly strengthened through Ni2Si precipitates. However, these alloys have significant technical drawbacks: First, iron impurities are difficult to completely remove, easily forming coarse Fe-Ni-Si inclusions, reducing the alloy's plasticity and conductivity; second, the grain refinement effect is limited under a single microalloying system, and the uneven distribution of precipitates leads to poor strength-conductivity matching; third, deep cryogenic treatment in traditional manufacturing processes is mostly static heat preservation, which can only introduce a small number of dislocations, resulting in limited strengthening effects; fourth, precipitates tend to coarsen under high-temperature environments, leading to alloy softening and failure.

[0003] To address these issues, existing technologies attempt to introduce boron (B) to form the FeB phase with Fe to purify impurities, or employ cryogenic treatment to refine grains. However, these methods mostly involve adding a single element or combining conventional processes, failing to achieve systematic innovation. For example, some patents simply add boron to adjust the composition ratio without considering the synergistic effects with other microalloying elements; cryogenic treatment often employs a static method of direct liquid nitrogen immersion, without incorporating deformation to introduce high-density defects, making it difficult to precisely control the precipitated phase. Furthermore, existing alloys lack high-temperature stability, exhibiting significant performance degradation in environments above 200°C, limiting their application in high-end, high-temperature environments.

[0004] Based on this, the present invention designs a "Ni-Si-B-Zr-RE" pent-element composite microalloying system and innovatively develops an integrated process of "three-stage cryogenic plastic deformation + multi-stage cold rolling + graded aging". By utilizing the synergistic strengthening between elements and the synergistic control of the process, a multi-scale composite strengthening structure is constructed, which simultaneously improves the strength, conductivity and high-temperature stability, thus solving the technical bottleneck of existing Cu-Ni-Si alloys. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a calcium carbonate filler for rubber reinforcement and its preparation process.

[0006] A boron-containing high-strength, high-conductivity copper alloy, with copper as the base metal, has the following chemical composition by mass percentage: Ni 2.5~3.8%, Si 0.6~1.0%, B 0.002~0.004%, Zr 0.01~0.05%, La+Ce composite alloy: 0.005~0.02%, Fe: 0.01-0.03%, impurities: 0.1%, balance Cu, and the mass ratio of La to Ce is 1:1. Furthermore, the microstructure of the boron-containing high-strength and high-conductivity copper alloy is a multi-scale composite strengthening structure, including an α-Cu matrix, dispersed nanoscale Ni2Si precipitates, ultrafine FeB phase, ZrSi nanophase, and nanotwins.

[0007] A method for cryogenic deformation heat treatment of boron-containing high-strength and high-conductivity copper alloys, characterized by comprising the following steps: (1) Vacuum casting and composite purification: Copper ingots and alloy elements are proportioned and placed in a vacuum induction furnace. They are melted at 1150~1200℃ and held for 20~30 minutes. Then, composite purification is carried out by ultrasonic vibration and electromagnetic stirring: first, ultrasonic vibration with a power of 600~800W is used for 5~8 minutes, and then electromagnetic stirring is carried out for 10~15 minutes. The current of electromagnetic stirring is 30~40A and the frequency is 50~60Hz. Then, the ingot is cast under a mixed protective atmosphere of argon and nitrogen. (2) Homogenization treatment: The ingot is kept at 920~940℃ for 4.5~5.5h and then cooled to room temperature of 22-24℃ with the furnace to obtain a homogenized ingot; (3) Hot rolling and quenching: The homogenized ingot is heated to 880~900℃, held for 1~1.5h and then hot rolled with a deformation of 60~70%. After hot rolling, it is water quenched to room temperature at a cooling rate of 90~100℃ / s to obtain a supersaturated solid solution. (4) Three-stage cryogenic plastic deformation treatment: ① Gradient cooling: The saturated solid solution is cooled from room temperature to -80℃ at a rate of 5~10℃ / min and held for 1~2h; ② Cryogenic plastic deformation: The saturated solid solution is then cold rolled at -80℃ with a small deformation amount of 10~20%; ③ Constant temperature cryogenic treatment: The temperature of the saturated solid solution is then cooled to -196℃ at a rate of 2~3℃ / min and held for 3~6h, and then naturally heated to room temperature of 22-24℃ to obtain the billet; (5) Multi-stage cold rolling: The billet is subjected to three-stage cold rolling with a total deformation of 70-90%, specifically: 30-40% for the first stage cold rolling, 30-35% for the second stage cold rolling, and 10-15% for the third stage cold rolling. After each stage of cold rolling, the material is relaxed at room temperature for 1-2 hours to obtain the cold-rolled material. (6) Graded aging treatment: ① Pre-aging: Hold the cold-rolled material at 350~400℃ for 1~2h to promote the nucleation of precipitated phases; ② Main aging: Then raise the temperature to 460~490℃ and hold for 3~5h to promote the growth of precipitated phases to the optimal size; ③ Stabilization aging: Finally, control the temperature at 320~340℃ and hold for 1~2h to eliminate internal stress and finally obtain a high-strength and high-conductivity copper alloy containing boron.

[0008] Furthermore, the vacuum degree of the vacuum induction furnace in step (1) is ≤5×10 -3 Pa, the protective atmosphere is a mixture of argon and nitrogen, with argon accounting for 70-80% and nitrogen accounting for 20-30%.

[0009] Furthermore, in step (3), the hot rolling speed is 1.5~2.0m / s, and the quenching cooling is achieved by spray cooling.

[0010] Furthermore, in step (4), the cold rolling speed of cryogenic plastic deformation is 0.5~1.0m / s.

[0011] Furthermore, the heating rate for the graded aging in step (6) is 2~3℃ / min.

[0012] The present invention has the following advantages: 1. This invention employs a vacuum casting and composite purification process. Vacuum casting avoids oxidation, while ultrasonic vibration and electromagnetic stirring are combined for composite purification. Ultrasonic vibration refines the melt grains, and electromagnetic stirring promotes the dispersed precipitation of the FeB phase, thus solving the problem of uneven impurity distribution in traditional casting.

[0013] 2. The cryogenic treatment of this invention is a three-stage process of gradient cooling, cryogenic plastic deformation, and isothermal cryogenic treatment. Gradient cooling induces a small number of dislocations, cryogenic plastic deformation promotes dislocation proliferation and nanotwin nucleation, and isothermal cryogenic treatment further introduces high-density defects and promotes the formation of ultrafine precipitates. This achieves a dynamic strengthening effect by simultaneously introducing defects and strengthening precipitates during the cryogenic process, resulting in an alloy with a tensile strength ≥750MPa, conductivity ≥48%IACS, elongation ≥10%, and a tensile strength retention rate ≥95% after holding at 250℃ for 100 hours. This achieves a triple balance of high strength, high conductivity, and good plasticity.

[0014] 3. This invention uses a three-stage small deformation cold rolling process to replace the traditional large deformation cold rolling process. After each stage of cold rolling, the cold rolling process is relaxed at room temperature to avoid cracking and retain high-density dislocations. The graded aging process is carried out in three steps: pre-aging, main aging, and stabilization aging. This process precisely controls the nucleation, growth, and stabilization of precipitates, achieving the optimal matching of precipitate size and distribution. At the same time, it shortens the process time and improves production efficiency.

[0015] 4. This invention uses a mixture of argon and nitrogen for protection instead of graphite covering, reducing pollution and optimizing process parameters to shorten the heat preservation time, reduce energy consumption, and is suitable for large-scale industrial production. Attached Figure Description

[0016] Figure 1 This is a flowchart of the cryogenic deformation heat treatment method for boron-containing high-strength and high-conductivity copper alloys according to the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention. Example 1

[0018] A boron-containing high-strength, high-conductivity copper alloy, the raw materials are formulated by mass percentage as follows: Ni: 3.0%, Si: 0.7%, B: 0.003%, Zr: 0.03%, La: 0.005%, Ce: 0.005%, Fe: 0.02%, with the remainder being Cu.

[0019] Deep cryogenic deformation heat treatment methods for boron-containing high-strength, high-conductivity copper alloys, such as Figure 1 As shown, the process includes the following steps: (1) Vacuum casting and composite purification: vacuum degree 3×10 -3 Pa, 1180℃ melting, heat preservation for 25 min, ultrasonic vibration power 700W, time 6 min, electromagnetic stirring current 35A, frequency 55Hz, time 12 min, argon + nitrogen (75%+25%) mixed protection casting; (2) homogenization treatment: heat preservation at 930℃ for 5 h, and furnace cooling to room temperature 23℃; (3) hot rolling and quenching: heat preservation at 890℃ for 1.2 h, hot rolling deformation amount 65%, rolling speed 1.8 m / s, then water quenching to room temperature 22℃, water quenching cooling speed 95℃ / s; (4) three-stage deep cryogenic plastic deformation: ① gradient cooling to -80℃ at a rate of 8℃ / min, heat preservation for 1.5 h; ② cold rolling at -80℃, cold rolling speed is 0 .5m / s; deformation amount 15%; ③ cool down to -196℃ at a rate of 2℃ / min, hold for 4h, and then naturally heat up to room temperature 23℃ to obtain the billet; (5) -80℃ multi-stage cold rolling: the billet first-stage cold rolling deformation amount 35%, room temperature relaxation 1.5h; second-stage cold rolling deformation amount 32%, room temperature relaxation 1.5h; third-stage cold rolling deformation amount 13%, room temperature relaxation 1.5h to obtain the cold-rolled material; (6) graded aging: ① pre-aging: hold the cold-rolled material at 380℃ for 1.5h; ② main aging: heat up to 470℃ and hold for 4h, heating rate 5℃ / min; ③ stabilization aging: cool down to 330℃ and hold for 1.5h to obtain the boron-containing high-strength and high-conductivity copper alloy. Example 2

[0020] A boron-containing high-strength, high-conductivity copper alloy, the raw materials are formulated by mass percentage as follows: Ni: 3.8%, Si: 1.0%, B: 0.004%, Zr: 0.05%, La: 0.01%, Ce: 0.01%, Fe: 0.03%, with the remainder being Cu.

[0021] Deep cryogenic deformation heat treatment methods for boron-containing high-strength, high-conductivity copper alloys, such as Figure 1 As shown, the process includes the following steps: (1) Vacuum casting and composite purification: vacuum degree 3×10 -3 Pa, 1200℃ melting, heat preservation for 30 min, ultrasonic vibration power 800W, time 8 min, electromagnetic stirring current 40A, frequency 60Hz, time 15 min, argon + nitrogen (80%+20%) mixed protection casting; (2) homogenization treatment: heat preservation at 940℃ for 5.5 h, furnace cooling to room temperature 24℃; (3) hot rolling and quenching: heat preservation at 900℃ for 1.5 h, hot rolling deformation amount 70%, rolling speed 2.0 m / s, then water quenching to room temperature 22℃, water quenching cooling speed 100℃ / s; (4) three-stage deep cryogenic plastic deformation: ① gradient cooling at a rate of 10℃ / min to -80℃, heat preservation for 2 h; ② cold rolling at -80℃, The cold rolling speed is 0.8 m / s and the deformation is 20%; ③ The temperature is gradually reduced to -196℃ at a rate of 3℃ / min, held for 6 hours, and then naturally heated to room temperature of 24℃ to obtain the billet; (5) -80℃ multi-stage cold rolling: the billet is cold rolled for 40% deformation at the first stage and relaxed at room temperature for 2 hours; the cold rolled for 35% deformation at the second stage and relaxed at room temperature for 2 hours; the cold rolled for 15% deformation at the third stage and relaxed at room temperature for 2 hours to obtain the cold rolled material; (6) graded aging: ① pre-aging: the cold rolled material is held at 400℃ for 2 hours; ② main aging: the temperature is raised to 490℃ and held for 5 hours at a rate of 5℃ / min; ③ stabilization aging: the temperature is lowered to 340℃ and held for 2 hours to obtain a high-strength and high-conductivity copper alloy containing boron. Example 3

[0022] A boron-containing high-strength, high-conductivity copper alloy, the raw materials are formulated by mass percentage as follows: Ni: 2.5%, Si: 0.6%, B: 0.002%, Zr: 0.01%, La: 0.0025%, Ce: 0.0025%, Fe: 0.01%, with the remainder being Cu.

[0023] Deep cryogenic deformation heat treatment methods for boron-containing high-strength, high-conductivity copper alloys, such as Figure 1 As shown, the process includes the following steps: (1) Vacuum casting and composite purification: vacuum degree 3×10 -3Pa, 1150℃ melting, heat preservation for 20 min, ultrasonic vibration power 600W, time 5 min, electromagnetic stirring current 30A, frequency 50Hz, time 10 min, argon + nitrogen (70%+30%) mixed protection casting; (2) homogenization treatment: heat preservation at 920℃ for 4.5 h, furnace cooling to room temperature 22℃; (3) hot rolling and quenching: heat preservation at 880℃ for 1 h, hot rolling deformation amount 60%, rolling speed 1.5 m / s, then water quenching to room temperature 22℃, water quenching cooling speed 90℃ / s; (4) three-stage deep cryogenic plastic deformation: ① gradient cooling to -80℃ at a rate of 5℃ / min, heat preservation for 1 h; ② cold rolling at -80℃, cold rolling The speed is 1.0 m / s, and the deformation is 10%; ③ The temperature is gradually reduced to -196℃ at a rate of 2℃ / min, and held for 3 hours. Then the temperature is naturally raised to room temperature of 22℃ to obtain the billet; (5) -80℃ multi-stage cold rolling: the billet is cold rolled for 30% deformation at the first stage and relaxed at room temperature for 1 hour; the cold rolled for 30% deformation at the second stage and relaxed at room temperature for 1 hour; the cold rolled for 10% deformation at the third stage and relaxed at room temperature for 1 hour to obtain the cold rolled material; (6) graded aging: ① pre-aging: the cold rolled material is held at 350℃ for 1 hour; ② main aging: the temperature is raised to 460℃ and held for 3 hours at a rate of 5℃ / min; ③ stabilization aging: the temperature is lowered to 320℃ and held for 1 hour to obtain a high-strength and high-conductivity copper alloy containing boron.

[0024] Comparative Example 1: Compared with Example 1, Comparative Example 1 differs in that the ingredients are proportioned by mass percentage as follows: Ni 3.0%, Si 0.7%, B 0.003%, Fe 0.02%, with the remainder being Cu, and the remaining processes are the same as in Example 1.

[0025] Comparative Example 2: Compared with Example 1, Comparative Example 2 differs in that the alloy composition is the same as that of Example 1, the cryogenic treatment adopts the process of directly holding at -196°C for 8 hours, and the rest of the process is the same as that of Example 1.

[0026] Tensile specimens were prepared according to GB / T228.1-2010 standard in Examples 1-3 and Comparative Examples 1-2, and room temperature tensile tests were performed using an electronic universal testing machine at a tensile rate of 1×10⁻⁶. -3 s -1 Each sample was tested three times, and the average value was taken. The high temperature stability test was conducted by keeping the sample in a constant temperature chamber at 250℃ for 100 hours and then performing a tensile test according to the above standard. The results are shown in Table 1.

[0027] According to the GB / T3048.2-2007 standard, the room temperature conductivity was tested using a four-probe conductivity meter. Each sample of Examples 1-3 and Comparative Examples 1-2 was tested 5 times, and the average value was taken. The results are shown in Table 2.

[0028] Table 1

[0029] Table 2

[0030] The embodiments of the present invention have an alloy with a tensile strength ≥750MPa and an elongation ≥10%, breaking through the bottleneck of existing Cu-Ni-Si alloys where "the conductivity decreases as the strength increases". After holding at 250℃ for 100 hours, the tensile strength retention rate is ≥95%, which is better than existing alloys (usually ≤90%). The conductivity is ≥48%, meeting the requirements of high-end high-temperature resistant applications and achieving a triple balance of high strength, high conductivity and good plasticity.

[0031] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A boron-containing high-strength, high-conductivity copper alloy, characterized in that, With copper as the base metal, the alloy's chemical composition by mass percentage is: Ni 2.5~3.8%, Si 0.6~1.0%, B 0.002~0.004%, Zr 0.01~0.05%, La+Ce 0.005~0.02%, Fe 0.01-0.03%, impurities 0.1%, and the balance being Cu; the mass ratio of La to Ce is 1:

1.

2. The boron-containing high-strength, high-conductivity copper alloy according to claim 1, characterized in that, The microstructure of boron-containing high-strength and high-conductivity copper alloys is a multi-scale composite strengthening structure, including an α-Cu matrix, dispersed nanoscale Ni2Si precipitates, ultrafine FeB phase, ZrSi nanophase, and nanotwins.

3. A method for cryogenic deformation heat treatment of a boron-containing high-strength, high-conductivity copper alloy as described in claim 1, characterized in that, Includes the following steps: (1) Vacuum casting and composite purification: Copper ingots and alloy elements are proportioned and placed in a vacuum induction furnace. They are melted at 1150~1200℃ and held for 20~30 minutes. Then, composite purification is carried out by ultrasonic vibration and electromagnetic stirring: first, ultrasonic vibration with a power of 600~800W is used for 5~8 minutes, and then electromagnetic stirring is carried out for 10~15 minutes. The current of electromagnetic stirring is 30~40A and the frequency is 50~60Hz. Then, the ingot is cast under a mixed protective atmosphere of argon and nitrogen. (2) Homogenization treatment: The ingot is kept at 920~940℃ for 4.5~5.5h and then cooled to room temperature of 22-24℃ with the furnace to obtain a homogenized ingot; (3) Hot rolling and quenching: The homogenized ingot is heated to 880~900℃, held for 1~1.5h and then hot rolled with a deformation of 60~70%. After hot rolling, it is water quenched to room temperature at a cooling rate of 90~100℃ / s to obtain a supersaturated solid solution. (4) Three-stage cryogenic plastic deformation treatment: ① Gradient cooling: The saturated solid solution is cooled from room temperature to -80℃ at a rate of 5~10℃ / min and held for 1~2h; ② Cryogenic plastic deformation: The saturated solid solution is then cold rolled at -80℃ with a small deformation amount of 10~20%; ③ Constant temperature cryogenic treatment: The temperature of the saturated solid solution is then cooled to -196℃ at a rate of 2~3℃ / min and held for 3~6h, and then naturally heated to room temperature of 22-24℃ to obtain the billet; (5) Multi-stage cold rolling: The billet is subjected to three-stage cold rolling with a total deformation of 70-90%, specifically: 30-40% for the first stage cold rolling, 30-35% for the second stage cold rolling, and 10-15% for the third stage cold rolling. After each stage of cold rolling, the material is relaxed at room temperature for 1-2 hours to obtain the cold-rolled material. (6) Graded aging treatment: ① Pre-aging: Hold the cold-rolled material at 350~400℃ for 1~2h to promote the nucleation of precipitated phases; ② Main aging: Then raise the temperature to 460~490℃ and hold for 3~5h to promote the growth of precipitated phases to the optimal size; ③ Stabilization aging: Finally, control the temperature at 320~340℃ and hold for 1~2h to eliminate internal stress and finally obtain a high-strength and high-conductivity copper alloy containing boron.

4. The cryogenic deformation heat treatment method according to claim 3, characterized in that, The vacuum degree of the vacuum induction furnace in step (1) is ≤5×10 -3 Pa, the protective atmosphere is a mixture of argon and nitrogen, with argon accounting for 70-80% and nitrogen accounting for 20-30%.

5. The cryogenic deformation heat treatment method according to claim 3, characterized in that, In step (3), the hot rolling speed is 1.5~2.0m / s, and the quenching cooling is achieved by spray cooling.

6. The cryogenic deformation heat treatment method according to claim 3, characterized in that, In step (4), the cold rolling speed of cryogenic plastic deformation is 0.5~1.0m / s.

7. The cryogenic deformation heat treatment method according to claim 3, characterized in that, In step (6), the heating rate for the staged aging process is 2~3℃ / min.

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