A Cu-Ni-Si alloy material and its preparation method

Abstract

This invention discloses a Cu-Ni-Si alloy material and its preparation method, belonging to the field of non-ferrous metal processing technology. The preparation method includes: melting and melt protection, horizontal continuous casting, solution treatment, cold rolling, first-stage aging, intermediate cold working, second-stage aging, and low-temperature tension annealing. By using a copper-silicon alloy as the silicon source and combining a melt protection strategy with protective gas and covering agents, this invention effectively solves the problem of crystallizer blockage caused by Si oxidation and slagging during horizontal continuous casting. Simultaneously, by rapidly cooling the horizontal continuous casting to obtain a supersaturated fine-grained billet, combined with direct large-deformation cold rolling without intermediate annealing, and a synergistic heat treatment process of "pre-aging – intermediate cold working – final aging – low-temperature tension annealing," an excellent match is achieved between high strength (>800MPa), high electrical conductivity (>45% IACS), and low stress relaxation rate (<10%). This invention features a short process, low energy consumption, and high yield, making it suitable for the industrial production of high-performance copper alloy strips.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal processing technology, and more specifically, to a Cu-Ni-Si alloy material and its preparation method. Background Technology

[0002] Cu-Ni-Si alloy is an important precipitation-strengthened copper alloy. Due to its good strength, conductivity and stress relaxation resistance, it is widely used in high-performance elastic components in the fields of electronics, electrical engineering, integrated circuit lead frames, various connectors, relays and aerospace.

[0003] Currently, the mainstream production method for Cu-Ni-Si alloys is semi-continuous casting. The typical process flow is: raw material smelting → semi-continuous vertical ingot casting → hot rolling → solution treatment → multi-pass cold rolling → aging strengthening. For example, patent CN110195170A discloses a production method for copper-nickel-silicon alloy strip, which uses semi-continuous casting followed by heating, hot rolling, multiple solution treatments, multiple cold rollings, and aging heat treatment to achieve certain performance characteristics. Another example is patent CN116815008B, which discloses a high-strength, high-conductivity copper-nickel-silicon alloy strip and its preparation method. This method is also based on semi-continuous casting, combined with hot rolling, multi-stage heat treatment, and cold rolling processes to obtain a fine-grained structure and excellent properties.

[0004] However, the aforementioned traditional process based on semi-continuous casting has the following main technical problems:

[0005] 1. Long process and high energy consumption: Hot rolling billet requires heating the ingot to 800-950℃, and subsequent solution treatment and annealing are often required, resulting in a long production cycle and huge energy consumption.

[0006] 2. The yield rate needs to be improved: Semi-continuous castings usually need to be milled after hot rolling to remove surface oxide scale and defects, resulting in material loss and a decrease in the overall yield rate.

[0007] 3. High equipment investment: Semi-continuous casting equipment is heavy and requires the construction of deep foundation pits and heavy support structures, resulting in high equipment investment costs and a large footprint.

[0008] 4. Challenges to compositional uniformity: The cooling rate of semi-continuous casting is relatively slow, which can easily lead to segregation of Ni and Si elements at grain boundaries, affecting the uniformity of precipitation during subsequent aging and the stability of product performance.

[0009] To overcome the aforementioned drawbacks, the industry has attempted to introduce horizontal continuous casting technology to achieve short-process production. However, when applying horizontal continuous casting to Cu-Ni-Si alloys, a unique key process bottleneck arises: the Si element in the alloy is highly susceptible to oxidation during smelting and casting, generating high-melting-point SiO2 slag. This slag adheres to and clogs the crystallizer, severely disrupting production continuity and causing surface and internal defects in the cast billets, resulting in a significant decrease in yield. Therefore, effectively suppressing Si oxidation and slag formation is crucial for achieving short-process production of Cu-Ni-Si alloys through horizontal continuous casting. Summary of the Invention

[0010] (a) Technical problems to be solved

[0011] The first technical problem to be solved by the present invention is to provide a method for preparing Cu-Ni-Si alloy materials, so as to shorten the production process, reduce energy consumption, improve the yield, and solve the problem of Si oxidation and slag formation during horizontal continuous casting.

[0012] The second technical problem to be solved by the present invention is to provide a Cu-Ni-Si alloy material prepared by the above method, which has high strength, high conductivity and excellent stress relaxation resistance.

[0013] (II) Technical Solution

[0014] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0015] A method for preparing a Cu-Ni-Si alloy material includes the following steps:

[0016] a. Smelting and melt protection: The materials are distributed according to the design, and copper-silicon alloy is used as the silicon source for smelting; during the smelting process, a protective gas is introduced into the surface of the melt and a covering agent is applied; after smelting, the melt is kept at a constant temperature and then allowed to stand to remove the slag;

[0017] b. Horizontal continuous casting: The melt processed in step a is subjected to horizontal continuous casting to obtain a 16mm thick billet; the billet pulling speed of the horizontal continuous casting is 160-170mm / min, and the cooling rate is 100-200℃ / s;

[0018] c. Solution treatment: The billet obtained in step b is kept at 840-950℃ for 1-4 hours, and then cooled to room temperature by water;

[0019] d. Cold rolling: After solution treatment, the billet is cleaned (e.g., by brushing or pickling to remove the thin oxide layer) and then directly cold rolled without intermediate annealing. The cold rolling process uses multi-pass rolling, with single-pass deformation controlled at 15-20%, total deformation at 75-95%, and rolling speed of 5-20 m / min, rolling the billet to an intermediate strip with a thickness of 2-5 mm.

[0020] e. First stage of aging: Hold the cold-rolled material at 300-400℃ for 1-4 hours;

[0021] f. Intermediate cold working: The material after the first stage of aging is cold rolled, with a deformation of 10-30% per pass, and the thickness of the strip after rolling is 0.1-1mm;

[0022] g. Second-stage aging: The material after intermediate cold working is held at 450-500℃ for 1-4 hours and then air-cooled to obtain the final alloy material.

[0023] In this invention, a copper-silicon alloy is used instead of pure silicon as the silicon source. Utilizing its better miscibility with the copper matrix and lower oxidation tendency, the formation of SiO2 slag is reduced at the source; this is "raw material-level protection." During the smelting process, a protective gas (such as high-purity nitrogen) is introduced, and a covering agent (such as charcoal) is applied to create a physical isolation and a localized reducing atmosphere, doubly preventing melt oxidation; this is "process-level protection." After smelting, heat preservation and settling promote the floating of any trace inclusions that may form, and then the slag is thoroughly removed, achieving deep purification of the melt; this is "melt-level purification." Through the integrated application of this "three-level protection strategy," the problems of Si oxidation slag formation and crystallizer blockage are systematically solved, clearing the way for the application of horizontal continuous casting in Cu-Ni-Si alloy production.

[0024] This invention employs a horizontal continuous casting process, whose rapid cooling characteristics (100-200℃ / s) help obtain fine-grained billets with high and uniform supersaturation of Ni and Si elements, effectively suppressing the precipitation of coarse primary phases. After solution treatment, the resulting billets can be directly cold-rolled with large deformation without hot rolling. Because the as-cast microstructure is fine and a supersaturated solid solution, it exhibits good processing plasticity, thus eliminating the intermediate annealing step required in conventional processes, significantly shortening the process and reducing energy consumption.

[0025] Furthermore, this invention employs a process route combining staged aging with intermediate cold working. The first stage of aging (pre-aging) is performed at a medium temperature, causing some solute atoms to undergo short-range diffusion, forming early precipitates and eliminating most of the processing stress. The intermediate cold working step introduces a suitable number of dislocations, which become preferential nucleation sites for the strengthening phase during subsequent aging, contributing to the uniform refinement of the precipitates. The second stage of aging (final aging) is performed at a higher temperature, promoting the full precipitation of the Ni2Si strengthening phase, achieving a synergistic improvement in strength and conductivity. Due to the pre-treatment of pre-aging and intermediate cold working, the precipitates after final aging are finer and more dispersed, and the internal stress level is initially optimized.

[0026] As a preferred embodiment of the present invention, after step g, a low-temperature tension annealing step is further included: the material after the second-stage aging is held at 200-250°C for 1-4 hours, while tension is applied along the rolling direction of the material, the tension being 10-30% of the yield strength of the material. This thermo-mechanical coupling treatment improves the stress relaxation resistance through the following mechanisms: (1) promoting the sliding and rearrangement of movable dislocations along the stress direction to form a more stable, low-energy dislocation configuration; (2) eliminating the microscopic internal stresses remaining during cold rolling and aging, reducing the thermal activation driving force of stress relaxation; (3) the tension range ensures that the formed Ni2Si precipitates are not destroyed. By promoting the rearrangement of dislocations to a more stable state through tension, the stress relaxation driving force of the alloy during long-term service is significantly reduced, thereby obtaining excellent stress relaxation resistance (stress relaxation rate <10%), which is crucial for high-precision elastic elements.

[0027] As a further improvement of the present invention, the Cu-Ni-Si alloy material described in step a comprises, by weight percentage: Ni 1.8-4.0 wt%, Si 0.5-1.0 wt%, with a Ni to Si weight ratio of 2-4:1, and the balance being Cu and unavoidable impurities. This composition range matches the rapid cooling characteristics of horizontal continuous casting, which is beneficial for obtaining a solid solution with high supersaturation.

[0028] To further optimize performance, the composition may also include one or more microalloying elements selected from Mg, Cr, Y, and Zr. These microalloying elements have a deep synergistic effect with the rapid cooling process of horizontal continuous casting. Specifically, Mg (0.01-0.3wt%) can refine the Ni2Si precipitate, keeping it fine and dispersed, thereby improving strength without reducing conductivity; Cr (0.05-0.5wt%) preferentially forms the Cr2Si phase, optimizing the Ni / Si ratio and promoting the full precipitation of Ni2Si; Y (0.02-0.3wt%) can purify the melt, reduce inclusions, and enrich at the solid-liquid interface, promoting the transformation of columnar crystals to equiaxed crystals; Zr (0.01-0.3wt%) forms the ZrSi2 phase under rapid cooling conditions, serving as a heterogeneous nucleation core, refining the as-cast grains, and suppressing the segregation of Ni and Si elements at grain boundaries.

[0029] As another preferred embodiment of the present invention, when the Ni content is high (≥3.5wt%), in order to cope with its segregation tendency, an electromagnetic auxiliary module can be activated during the horizontal continuous casting process described in step b, and the magnetic field strength is controlled at 0.2-0.3T to further reduce the elemental segregation and ensure the uniformity of the microstructure.

[0030] The present invention also provides a Cu-Ni-Si alloy material prepared by any of the above methods. This material has fine grains and uniformly dispersed nanoscale Ni2Si precipitates, thereby achieving an excellent match of high strength (tensile strength >800MPa), high conductivity (>45%IACS) and low stress relaxation rate (<10%), and can stably prepare ultrathin strips of 0.1-1mm.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. A "three-level protection strategy" was proposed to overcome the bottleneck of horizontal continuous casting: Through integrated innovation of "raw material level (copper-silicon alloy) - process level (protective gas + covering agent) - melt level (static purification)," the oxidation slag formation of Si element and the crystallizer blockage problem were effectively suppressed from the root, so that the horizontal continuous casting technology can be stably and continuously applied to the production of high Si content Cu-Ni-Si alloy, laying the foundation for the industrialization of short process technology.

[0033] 2. Short process, low energy consumption, and small equipment investment: It eliminates the hot rolling and intermediate annealing processes in traditional processes, significantly shortening the production cycle and reducing overall energy consumption. At the same time, horizontal continuous casting equipment is lightweight, requires no deep foundation pit, and has a much lower equipment investment cost than semi-continuous casting, making it easy to retrofit existing plants.

[0034] 3. Uniform microstructure and superior performance: Utilizing the rapid cooling characteristics of horizontal continuous casting, a billet with uniform composition and fine grains is obtained, effectively suppressing elemental segregation. Combined with a unique heat treatment process of "pre-aging - intermediate cold working - final aging - low-temperature tension annealing," precise control over the size and distribution of precipitated phases and the internal stress state of the material is achieved. The final product achieves high strength (>800MPa) and high electrical conductivity (>45%IACS), while maintaining a stress relaxation rate as low as 5.5%, superior to the more than 12% of traditional processes, meeting the stringent requirements for long-term dimensional stability in high-reliability applications.

[0035] 4. High yield: Due to the solution of slag formation problem, the surface and internal defect rate of the billet is greatly reduced, and milling treatment is not required, resulting in a significant improvement in the overall yield of the material. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] Example 1

[0038] This embodiment provides a Cu-Ni-Si alloy material and its preparation method.

[0039] Alloy composition (wt%): Ni 1.8%, Si 0.5% (Ni / Si=3.6:1), Mg 0.2% (added as CuMg10 master alloy), balance Cu and unavoidable impurities (total ≤0.1%). Raw materials: cathode copper, nickel plate, CuSi50, CuMg10.

[0040] The preparation steps are as follows:

[0041] (1) Smelting and melt protection: The prepared raw materials are added to the medium-frequency induction furnace for smelting. Charcoal is used as a covering agent to cover the surface of the molten pool, and nitrogen gas with a purity of ≥99.99% (flow rate 0.8 L / min) is introduced into the melt for protection. After the raw materials are completely melted, the temperature is maintained at 1300℃ for 20 min, and then left to stand for 6 min to completely remove the slag.

[0042] (2) Horizontal continuous casting: The purified melt is introduced into a holding furnace for horizontal continuous casting. A crystallizer with a double water jacket cooling structure is used, and the cooling water pressure is controlled at 0.25 MPa to achieve a cooling rate of approximately 150℃ / s. The billet pulling adopts a "pull-stop-reverse push" cycle mode, with a pulling speed of 160 mm / min. A billet with a thickness of 16 mm is obtained.

[0043] (3) Solution treatment: The billet is kept at 900℃ for 2 hours and then rapidly cooled to room temperature by water.

[0044] (4) Cold rolling: The solution-treated billet is directly cold rolled in multiple passes on a four-roll cold rolling mill at a rolling speed of 6 m / min and a total deformation of 81.25%, from a thickness of 16 mm to a thickness of 3.0 mm. No intermediate annealing is performed during the rolling process.

[0045] (5) First stage of aging: keep the cold-rolled strip at 350℃ for 2 hours and then air cool.

[0046] (6) Intermediate cold working: The pre-aged strip is subjected to multiple cold rolling passes with a total deformation of 90%, and finally rolled to a strip thickness of 0.3 mm. The deformation of a single pass is controlled at 15-20%.

[0047] (7) Second stage of aging: The strip after intermediate cold processing is kept at 480℃ for 2 hours and then air-cooled.

[0048] (8) Low-temperature tension annealing: The strip after the second stage of aging is subjected to low-temperature tension annealing on a continuous annealing line at a temperature of 220°C and held for 2 hours. At the same time, tension is applied along the rolling direction, and the tension is 15% of the yield strength of the material at this time. Then, it is air-cooled to obtain the final alloy strip.

[0049] The performance of the alloy strip prepared in this embodiment was tested, and the results are shown in Table 1.

[0050] Example 2

[0051] This embodiment provides a Cu-Ni-Si alloy material and its preparation method.

[0052] Alloy composition (wt%): Ni 3.0%, Si 1.0% (Ni / Si=3.0:1), Cr 0.1% (added as CuCr10 master alloy), balance Cu and unavoidable impurities.

[0053] The preparation steps are as follows:

[0054] (1) Melting and melt protection: Same as in Example 1, but the melting temperature is increased to 1300℃ and the holding time is extended to 22min to ensure that Cr is completely dissolved.

[0055] (2) Horizontal continuous casting: billet speed 165 mm / min, cooling water pressure 0.3 MPa, the rest is the same as in Example 1.

[0056] (3) Solution treatment: keep warm at 920℃ for 2 h, then cool with water.

[0057] (4) Cold rolling: Total deformation 96%, rolled to 2.5 mm thickness.

[0058] (5) First stage of aging: 380℃ for 1.5 h, then air cooling.

[0059] (6) Intermediate cold working: The pre-aged strip is subjected to multiple cold rolling passes with a total deformation of 80%, and finally rolled to a strip thickness of 0.5 mm. The deformation of a single pass is controlled at 15-20%.

[0060] (7) Second stage of aging: 485℃ for 2 hours, followed by air cooling.

[0061] (8) Low-temperature tension annealing: the tension is 20% of the yield strength, the temperature is 230℃, and the holding time is 1.5 h.

[0062] The performance of the alloy strip prepared in this embodiment was tested, and the results are shown in Table 1.

[0063] Example 3

[0064] This embodiment provides a Cu-Ni-Si alloy material and its preparation method.

[0065] Alloy composition (wt%): Ni 4.0%, Si 1.0% (Ni / Si=4.0:1), Zr 0.2% (added as CuZr10 master alloy), balance Cu and unavoidable impurities.

[0066] The preparation steps are as follows:

[0067] (1) Smelting and melt protection: Same as in Example 1. The order of adding raw materials is to add cathode copper, nickel plate, CuZr10 first, and CuSi50 last.

[0068] (2) Horizontal continuous casting: billet speed 165 mm / min, cooling water pressure 0.35 MPa. Since the Ni content is ≥3.5 wt%, the electromagnetic auxiliary module is activated with a magnetic field strength of 0.25 T.

[0069] (3) Solution treatment: keep warm at 950℃ for 1.5 h, then cool with water.

[0070] (4) Cold rolling: intermediate strip rolled from 16 mm thickness to 2.0 mm thickness.

[0071] (5) First stage of aging: 400℃ for 1 h, then air cooling.

[0072] (6) Intermediate cold working: The pre-aged strip is subjected to multiple cold rolling passes with a total deformation of 90%, and finally rolled to a strip thickness of 0.2 mm. The deformation of a single pass is controlled at 15-30%.

[0073] (7) Second stage of aging: heat preservation at 500℃ for 1.5 h, followed by air cooling.

[0074] (8) Low-temperature tension annealing: the tension is 25% of the yield strength, the temperature is 240℃, and the holding time is 1 h.

[0075] The performance of the alloy strip prepared in this embodiment was tested, and the results are shown in Table 1.

[0076] Example 4

[0077] This embodiment provides a Cu-Ni-Si alloy material and its preparation method.

[0078] Alloy composition (wt%): Ni 2.5%, Si 1.0% (Ni / Si=2.5:1), Y 0.1% (added as CuY10 master alloy), balance Cu and unavoidable impurities.

[0079] The preparation steps are as follows:

[0080] (1) Melting and melt protection: The holding time is extended to 21 min, and the rest is the same as in Example 1.

[0081] (2) Horizontal continuous casting: billet speed 165 mm / min, cooling water pressure 0.3 MPa, the rest is the same as in Example 1.

[0082] (3) Solution treatment: keep warm at 880℃ for 3 h, then cool with water.

[0083] (4) Cold rolling: 75% total deformation, rolling intermediate strip from 16mm thickness to 4.0mm thickness.

[0084] (5) First stage of aging: 320℃ for 3 hours, followed by air cooling.

[0085] (6) Intermediate cold working: The pre-aged strip is subjected to multiple cold rolling passes with a total deformation of 80%, and finally rolled to a strip thickness of 0.8 mm. The deformation of a single pass is controlled at 15-20%.

[0086] (7) Second stage of aging: 460℃ for 2.5 h, then air cooling.

[0087] (8) Low-temperature tension annealing: the tension is 12% of the yield strength, the temperature is 210℃, and the holding time is 3 h.

[0088] The alloy strip prepared in this embodiment was subjected to performance tests, and the results are shown in Table 1.

[0089] Example 5

[0090] This embodiment provides a Cu-Ni-Si alloy material and its preparation method, focusing on the composite addition of two microalloying elements, Mg and Cr, to synergistically improve the material's strength and conductivity. The synergistic effect of Mg and Cr is manifested in: Mg refines the Ni2Si precipitate phase, while Cr forms the Cr2Si phase, consuming some Si. Together, they make the Ni2Si precipitation more uniform and dispersed, while the Cr2Si phase itself also has a precipitation strengthening effect. Experiments show that Example 5 with Mg+Cr composite addition (tensile strength 845 MPa, conductivity 46.8% IACS) has a 1.3 percentage point increase in conductivity compared to Example 2 with single addition (tensile strength 860 MPa, conductivity 45.5% IACS), demonstrating the synergistic advantage of composite addition.

[0091] Alloy composition (wt%): Ni 2.2%, Si 0.8% (Ni / Si = 2.75:1), Mg 0.15% (added with CuMg10 master alloy), Cr 0.2% (added with CuCr10 master alloy), balance Cu and unavoidable impurities (total ≤0.1%). Raw materials: cathode copper, nickel plate, CuSi50, CuMg10, CuCr10.

[0092] The preparation steps are as follows:

[0093] (1) Smelting and Melt Protection: The prepared raw materials are added to the medium-frequency induction furnace for smelting. Charcoal is used as a covering agent to cover the surface of the molten pool, and nitrogen gas with a purity of ≥99.99% (flow rate 0.8 L / min) is introduced into the melt for protection. After the raw materials are completely melted, the temperature is maintained at 1300℃ for 22 min to ensure that Mg and Cr are fully dissolved and evenly distributed. Then, the mixture is allowed to stand for 7 min to thoroughly remove the slag.

[0094] (2) Horizontal continuous casting: The purified melt is introduced into a holding furnace for horizontal continuous casting. A crystallizer with a double water jacket cooling structure is used, and the cooling water pressure is controlled at 0.28 MPa to achieve a cooling rate of approximately 160℃ / s. The billet pulling adopts a "pull-stop-reverse push" cycle mode with a pulling speed of 162 mm / min. A billet with a thickness of 16 mm is obtained.

[0095] (3) Solution treatment: The billet is kept at 910℃ for 2 hours and then rapidly cooled to room temperature by water.

[0096] (4) Cold rolling: The solution-treated billet is directly cold rolled in multiple passes on a four-roll cold rolling mill at a rolling speed of 8 m / min and a total deformation of 81.25%, from a thickness of 16 mm to a thickness of 3.0 mm. No intermediate annealing is performed during the rolling process.

[0097] (5) First stage of aging: keep the cold-rolled strip at 360℃ for 2 hours and then air cool.

[0098] (6) Intermediate cold working: The pre-aged strip is subjected to multiple cold rolling passes with a total deformation of 90%, and finally rolled to a strip thickness of 0.3 mm. The deformation of a single pass is controlled at 15-20%.

[0099] (7) Second stage of aging: The strip after intermediate cold processing is kept at 475℃ for 2 hours and then air-cooled.

[0100] (8) Low-temperature tension annealing: The strip after the second stage of aging is subjected to low-temperature tension annealing on a continuous annealing line at a temperature of 225°C and held for 2 hours. At the same time, tension is applied along the rolling direction, and the tension is 18% of the yield strength of the material at this time. Then, it is air-cooled to obtain the final alloy strip.

[0101] The performance of the alloy strip prepared in this embodiment was tested, and the results are shown in Table 1.

[0102] Example 6

[0103] This embodiment provides a Cu-Ni-Si alloy material and its preparation method, focusing on using a Ni / Si ratio close to the lower limit (2:1) and combining it with Zr microalloying to enhance the grain refinement effect. When the Ni / Si ratio decreases to 2:1, Si is relatively excess, and Zr forms the ZrSi2 phase with the excess Si, refining the as-cast grains. Simultaneously, the excess Si can form a small amount of elemental Si precipitation during aging, further improving strength. Experiments show that the tensile strength (855 MPa) of Example 6 is higher than theoretically expected, demonstrating the strengthening contribution of the ZrSi2 phase.

[0104] Alloy composition (wt%): Ni 2.0%, Si 1.0% (Ni / Si = 2.0:1), Zr 0.15% (added as CuZr10 master alloy), balance Cu and unavoidable impurities (total ≤0.1%). Raw materials: cathode copper, nickel plate, CuSi50, CuZr10. The order of adding raw materials is: cathode copper, nickel plate, CuZr10 first, and CuSi50 last.

[0105] The preparation steps are as follows:

[0106] (1) Smelting and Melt Protection: The prepared raw materials are added to the medium-frequency induction furnace for smelting. Charcoal is used as a covering agent to cover the surface of the molten pool, and nitrogen gas with a purity of ≥99.99% (flow rate 0.9 L / min) is introduced into the melt for protection. After the raw materials are completely melted, the temperature is maintained at 1320℃ for 25 min to ensure that Zr is fully dissolved and evenly distributed, and then allowed to stand for 8 min to completely remove the slag.

[0107] (2) Horizontal continuous casting: The purified melt is introduced into a holding furnace for horizontal continuous casting. A crystallizer with a double water jacket cooling structure is used, and the cooling water pressure is controlled at 0.32 MPa to achieve a cooling rate of approximately 180℃ / s. The billet pulling adopts a "pull-stop-reverse push" cycle mode, with a pulling speed of 168 mm / min. A billet with a thickness of 16 mm is obtained.

[0108] (3) Solution treatment: The billet is kept at 940℃ for 1.5 h and then rapidly cooled to room temperature by water.

[0109] (4) Cold rolling: The solution-treated billet is directly cold rolled in multiple passes on a four-roll cold rolling mill at a rolling speed of 10 m / min and a total deformation of 87.5%, from a thickness of 16 mm to a thickness of 2.0 mm. No intermediate annealing is performed during the rolling process.

[0110] (5) First stage of aging: keep the cold-rolled strip at 380℃ for 1.5 h and then air cool.

[0111] (6) Intermediate cold working: The pre-aged strip is subjected to multiple cold rolling passes with a total deformation of 90%, and finally rolled to a strip thickness of 0.2 mm. The deformation of a single pass is controlled at 15-25%.

[0112] (7) Second stage of aging: The strip after intermediate cold processing is kept at 490℃ for 1.5 h and then air-cooled.

[0113] (8) Low-temperature tension annealing: The strip after the second stage of aging is subjected to low-temperature tension annealing on a continuous annealing line at a temperature of 235°C and held for 1.5 h. At the same time, tension is applied along the rolling direction, and the tension is 22% of the yield strength of the material at this time. Then, it is air-cooled to obtain the final alloy strip.

[0114] The performance of the alloy strip prepared in this embodiment was tested, and the results are shown in Table 1.

[0115] Comparative Example 1: Cu-3.0Ni-1.0Si alloy (composition same as Example 2) prepared by traditional semi-continuous casting + hot rolling process. The surface defect rate of the billet after milling is about 8%, the Ni segregation is about 0.12 wt%, the tensile strength of the final product is 780 MPa, the conductivity is 46.0% IACS, and the stress relaxation rate is 12.5%.

[0116] Comparative Example 2: Cu-3.0Ni-1.0Si alloy was prepared using a conventional horizontal continuous casting process (without employing the three-level protection strategy of this invention, i.e., using pure silicon as the silicon source, only charcoal covering, and no gas protection). During the casting process, the crystallizer began to show signs of blockage at 28 minutes. After cleaning the crystallizer, a large amount of black SiO2 slag was found adhering to the inner wall, and the surface of the cast billet showed obvious pits and cracks, making it impossible to proceed to the subsequent rolling process. This confirms that the three-level protection strategy of this invention is the key to solving the slag problem in horizontal continuous casting and ensuring continuous production.

[0117] Comparative Example 3: The same alloy composition as Example 2 (Ni 3.0wt%, Si 1.0wt%, Cr 0.1wt%) was used, but the preparation process was traditional semi-continuous casting + hot rolling + solution treatment + cold rolling + single-stage aging (400℃×4h), without intermediate cold working, second-stage aging, and low-temperature tension annealing. Therefore, the precipitates were coarse and the internal stress was high, resulting in poor stress relaxation resistance. The performance test results are shown in Table 1.

[0118] Table 1 Performance Test Results

[0119]

[0120] Table 2. Scope and Function of Microalloying Elements

[0121]

[0122] As can be seen from the data in Table 1, Examples 1-6 using the technical solution of this invention exhibit low surface defect rates in the cast billets, eliminating the need for milling. The final products all possess tensile strengths greater than 800 MPa and electrical conductivity greater than 44.5% IACS. In particular, the stress relaxation rate at 150℃ / 100 h is all below 7.5%, achieving a good balance between high strength, high electrical conductivity, and excellent stress relaxation resistance. Compared to the comparative examples, the overall performance advantages of this invention are significant, especially in terms of significantly improved stress relaxation resistance.

[0123] This invention introduces horizontal continuous casting, a "pull-stop-reverse push" cycle mode, and a double-water jacket cooling process to obtain alloy materials with excellent comprehensive performance. Horizontal continuous casting: refers to a casting process in which molten metal solidifies in a crystallizer in a horizontal direction, distinct from the vertical ingot casting of semi-continuous casting; "pull-stop-reverse push" cycle mode: refers to the cyclic action of the horizontal continuous casting machine's dummy bar first pulling the billet forward (pulling length), stopping (releasing internal stress), and then pushing the billet backward (reducing the adhesion between the billet and the crystallizer); stress relaxation rate: refers to the degree of stress decay over time in an alloy during a stress relaxation test. In this patent, it specifically refers to the ratio of the difference between the initial stress (σ0) and the residual stress (σt) after continuous loading to the initial stress (σ0) after applying and maintaining the initial total strain (the initial stress corresponding to this strain is approximately 50% of its 0.2% yield strength) on a sample in the peak aging state at 150℃ for 100 hours (calculated as: stress relaxation rate = (σ0 - σt)). t () / σ0×100%); Double water jacket cooling: refers to a structure in which two independent water jackets are set outside the crystallizer (the inner layer covers the main body of the crystallizer and the outer layer covers part of the cooling area), and a cooling rate of 100-200℃ / s is achieved through dual temperature control.

[0124] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a Cu-Ni-Si alloy material, characterized in that, Includes the following steps: a. Smelting and melt protection: The materials are distributed according to the design, and copper-silicon alloy is used as the silicon source for smelting; during the smelting process, a protective gas is introduced into the surface of the melt and a covering agent is applied; after smelting, the melt is kept at a certain temperature and then allowed to stand to remove the slag; b. Horizontal continuous casting: The melt processed in step a is subjected to horizontal continuous casting to obtain a billet with a thickness of 16 mm; the billet pulling speed of the horizontal continuous casting is 160-170 mm / min, and the cooling rate is 100-200 °C / s; c. Solution treatment: The billet obtained in step b is kept at 840-950℃ for 1-4 hours, and then cooled to room temperature by water; d. Cold rolling: The solution-treated billet is directly cold rolled to the target thickness without intermediate annealing. The cold rolling adopts multi-pass rolling, with the deformation amount of a single pass controlled at 15-20%, the total deformation amount at 75-95%, and the rolling speed at 5-20 m / min, rolling the billet into an intermediate strip with a thickness of 2-5 mm. e. First stage of aging: Hold the cold-rolled material at 300-400℃ for 1-4 hours; f. Intermediate cold working: The material after the first stage of aging is cold rolled, with a deformation of 10-30% per pass, and the thickness of the strip after rolling is 0.1-1mm; g. Second-stage aging: The material after intermediate cold working is held at 450-500℃ for 1-4 hours and then air-cooled to obtain the final alloy material.

2. The preparation method according to claim 1, characterized in that, After step g, step h-low temperature tension annealing is also included: the material after the second stage of aging is kept at 200-250℃ for 1-4 hours, and tension is applied along the rolling direction of the material. The tension is 10-30% of the yield strength (σ0.2) of the material after the second stage of aging. A constant tension control mode is adopted, and the tension fluctuation is controlled within ±5%.

3. The preparation method according to claim 1 or 2, characterized in that, The protective gas in step a is nitrogen, with a flow rate of 0.5-1.0 L / min; the covering agent is charcoal or boron anhydride-based glass flux.

4. The preparation method according to claim 1 or 2, characterized in that, The horizontal continuous casting in step b is carried out using a crystallizer, which is equipped with a double water jacket cooling structure to achieve a cooling rate of 100-200℃ / s; the horizontal continuous casting adopts a "pull-stop-reverse push" cycle mode to control the billet pulling process.

5. The preparation method according to claim 1 or 2, characterized in that, The composition of the Cu-Ni-Si alloy material described in step a, by weight percentage, includes: Ni 1.8-4.0wt%, Si 0.5-1.0wt%, Ni to Si weight ratio of 2-4:1, and the balance being Cu and unavoidable impurities.

6. The preparation method according to claim 5, characterized in that, The composition also includes one or more microalloying elements selected from Mg, Cr, Y, and Zr, wherein the content of Mg is 0.01-0.3wt%, the content of Cr is 0.05-0.5wt%, the content of Y is 0.02-0.3wt%, and the content of Zr is 0.01-0.3wt%.

7. The preparation method according to claim 5, characterized in that, When the Ni content is ≥3.5wt%, the electromagnetic auxiliary module is activated during the horizontal continuous casting process described in step b, and the magnetic field strength is controlled at 0.2-0.3T.

8. The preparation method according to claim 1 or 2, characterized in that, Step d involves cold rolling the billet to an intermediate strip with a thickness of 2-5 mm, and step f involves intermediate cold working to roll the strip to a finished strip with a thickness of 0.1-1 mm.

9. A Cu-Ni-Si alloy material, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The Cu-Ni-Si alloy material according to claim 9, characterized in that, Its tensile strength is greater than 800 MPa, its electrical conductivity is greater than 45% IACS, and its stress relaxation rate is less than 10% after being subjected to an initial stress of 50% of its 0.2% yield strength at 150℃ for 100 hours.

Images