Processing method of high-strength conductive Cu-Ni-Si alloy strip

Abstract

The invention discloses a processing method of a high-strength conductive Cu-Ni-Si alloy strip, which comprises the following steps: weighing casting raw materials according to a preset proportioning range, and putting the casting raw materials into a smelting furnace for smelting and casting to obtain a cast ingot; the cast ingot is placed in a heating furnace to be subjected to homogenization treatment, the cast ingot subjected to homogenization treatment is subjected to multi-pass hot rolling treatment, a hot-rolled strip blank is obtained, the hot-rolled strip blank is subjected to double-face milling treatment, and a milled strip blank is obtained; carrying out multi-pass cold rolling treatment on the milled strip blank, and carrying out at least one time of intermediate stress relief annealing treatment among the multi-pass cold rolling treatment to obtain a cold-rolled strip; and the cold-rolled strip is put into a resistance furnace, graded aging treatment is conducted on the cold-rolled strip, and the Cu-Ni-Si alloy strip is obtained. According to the invention, the strength and conductivity of the alloy are improved through a multi-pass hot rolling and cold rolling combined plastic processing scheme and a graded aging treatment process.

Description

Technical Field

[0001] This invention relates to the field of alloy material processing technology, specifically to a processing method for high-strength conductive Cu-Ni-Si alloy strip. Background Technology

[0002] Cu-Ni-Si alloys, as a typical precipitation-strengthened copper alloy, achieve strengthening through the dispersed precipitation of Ni2Si intermetallic compounds, thus possessing high strength, good electrical and thermal conductivity, and excellent corrosion resistance. These properties make them a key basic material in high-tech fields such as new energy vehicles, precision electronics, and aerospace. As end products continue to develop towards higher power density and smaller, lighter designs, the market is placing more stringent demands on the comprehensive performance of Cu-Ni-Si alloy strips, requiring core indicators to simultaneously meet high standards such as tensile strength of not less than 650 MPa and electrical conductivity of not less than 58% IACS.

[0003] However, existing processing techniques for preparing high-performance Cu-Ni-Si alloy strips still have significant shortcomings. Firstly, in terms of plastic processing, traditional single cold rolling processes easily lead to uneven dislocation distribution within the strip, resulting in dislocation accumulation and entanglement. This uneven defect structure, during subsequent aging treatment, causes disordered nucleation sites and significant size distribution of Ni2Si precipitates, making it difficult to form a uniform and dispersed strengthening phase, thus limiting the full realization of the material's strength potential. Secondly, in terms of heat treatment, conventional single aging processes cannot accurately balance the nucleation and growth processes of precipitates: low-temperature aging can obtain fine precipitates, but the nucleation rate is insufficient, resulting in limited strengthening effect; high-temperature aging can increase the precipitation driving force, but it easily causes excessive coarsening of the precipitates, disrupting their coherent relationship with the matrix, leading to decreased strength and hindered improvement in conductivity. Therefore, a single aging regime cannot synergistically optimize the contradictory performance indicators of strength and conductivity. Furthermore, if the homogenization treatment of the ingot at the front end is insufficient, the dendritic segregation of Ni and Si elements will be inherited by the subsequent processing stages, resulting in large fluctuations in strip properties and poor forming consistency.

[0004] In summary, existing technologies, limited by the aforementioned bottlenecks in the processing flow, struggle to stably produce Cu-Ni-Si alloy strips that simultaneously possess ultra-high strength and high conductivity. Therefore, a new processing method is urgently needed to address issues such as dislocation control, precise control of precipitates, and microstructure uniformity, thereby improving the alloy's strength and conductivity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a processing method for high-strength conductive Cu-Ni-Si alloy strip, aiming to improve the alloy's strength and conductivity through a plastic processing scheme combining multi-pass hot rolling and cold rolling and a graded aging treatment process.

[0006] This invention discloses a method for processing high-strength conductive Cu-Ni-Si alloy strip, comprising: Weigh the casting raw materials according to the preset ratio range, and put the casting raw materials into the melting furnace for melting and casting to obtain ingots. The casting raw materials include Cu raw materials, Ni raw materials, Si raw materials and impurities. The ingot is placed in a heating furnace for homogenization treatment. The homogenization treatment temperature is 950~980℃ and the holding time is 3~5 hours. The homogenized ingot is subjected to multiple hot rolling processes to obtain a hot-rolled strip blank, and the hot-rolled strip blank is subjected to double-sided milling to obtain a milled strip blank. The milled strip is subjected to multiple cold rolling processes, and at least one intermediate stress-relieving annealing process is performed between the multiple cold rolling processes to obtain cold-rolled strip. The cold-rolled strip is placed in an electric resistance furnace and subjected to graded aging treatment to obtain Cu-Ni-Si alloy strip. The electric resistance furnace is in an argon atmosphere. The graded aging treatment includes pre-aging treatment and final aging treatment. The Cu-Ni-Si alloy strip includes dispersed Ni2Si precipitates.

[0007] Preferably, the preset proportion range of the casting raw materials is as follows: Cu raw material accounts for 97.3~98.5% by mass, Ni raw material accounts for 1.0~1.9% by mass, Si raw material accounts for 0.5~0.8% by mass, and impurities include Fe, Pb and trace impurities, with Fe accounting for less than or equal to 0.03% by mass, Pb accounting for less than or equal to 0.002% by mass, and the sum of the mass percentages of Cu raw material, Ni raw material, Si raw material and impurities is 100%.

[0008] Preferably, the Cu raw material is electrolytic copper with a purity greater than or equal to 99.99%; the Ni raw material is pure nickel with a purity greater than or equal to 99.95%; and the Si raw material is industrial silicon with a purity greater than or equal to 99.9%.

[0009] Preferably, the casting raw materials are fed into a smelting furnace for melting and casting to obtain an ingot, including: The casting raw materials are put into the melting furnace and melted until the casting raw materials are melted. Electromagnetic stirring is performed to obtain a molten liquid with uniform composition. The liquid is then held at the temperature for 40 to 60 minutes. The temperature inside the melting furnace is 1250 to 1300℃. The molten metal is poured into the casting mold at a temperature of 1180~1220℃; The molten liquid after pouring is cooled by water to obtain an ingot. The cooling rate is 8~12℃ / s, and the ingot size is 150mm×420mm×6000mm.

[0010] Preferably, the homogenized ingot is subjected to multiple hot rolling processes to obtain a hot-rolled strip, including: The homogenized ingot is heated to 860~900℃ and held at that temperature for 1.5~2.5 hours to obtain a pretreated ingot. The pretreated ingot is subjected to 7 to 9 hot rolling processes to obtain a hot-rolled strip with a thickness of 16 to 17 mm and a single-pass hot rolling deformation of 10% to 40%.

[0011] Preferably, the hot-rolled strip blank is subjected to double-sided milling to obtain a milled strip blank, including: The hot-rolled strip is subjected to double-sided milling to remove 0.8~1.2 mm of oxide layer and defect layer on the upper and lower surfaces to obtain milled strip. The surface roughness of the milled strip is less than or equal to 0.18 μm, and the thickness tolerance of the milled strip is ±0.05 mm.

[0012] Preferably, the number of passes in the multi-pass cold rolling process is 3 to 5, the rolling speed per pass is 0.3 to 2.3 m / s, the cold rolling deformation per pass is 15 to 25%, and the cumulative cold rolling deformation is 75 to 85%.

[0013] Preferably, the intermediate stress-relief annealing is performed when the cumulative cold rolling deformation reaches 40% to 60%, the annealing temperature of the intermediate stress-relief annealing is 360 to 400°C, the holding time of the annealing is 0.5 to 1.5 hours, and the thickness tolerance of the cold-rolled strip is ±0.02 mm.

[0014] Preferably, the pre-aging treatment temperature is 400~420℃, and the pre-aging treatment holding time is 1.5~2.5 hours; The final aging treatment temperature is 460~480℃, and the holding time for the final aging treatment is 2.5~3.5 hours.

[0015] Preferably, the Cu-Ni-Si alloy strip has a tensile strength range of 650~700MPa, a yield strength range of 620~660MPa, an elongation after fracture range of 12~15%, a conductivity range of 58~62%IACS, a surface roughness of less than or equal to 0.1μm, and a dimensional tolerance of ±0.005mm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves precise control over the alloy microstructure through a multi-pass hot rolling and cold rolling plastic processing scheme and a graded aging treatment process, thereby improving the strength and electrical conductivity of Cu-Ni-Si alloy strips. Multi-pass hot rolling, through controlled gradient deformation, gradually breaks down coarse grains in the ingot microstructure, forming a uniform subcrystalline structure, while simultaneously introducing an appropriate dislocation density for subsequent cold rolling. Intermediate stress-relief annealing effectively eliminates work hardening generated during cold rolling, avoiding cracking tendency caused by excessive dislocation accumulation and ensuring the formability of the cold-rolled strip. In the graded aging treatment stage, pre-aging at a lower temperature provides numerous nucleation sites for the Ni2Si precipitates, forming fine and uniformly distributed initial precipitates. Final aging at a higher temperature promotes the orderly growth of the precipitates while maintaining their coherence with the matrix, ultimately producing a high-strength, high-conductivity Cu-Ni-Si alloy strip. Attached Figure Description

[0017] Figure 1 A schematic flowchart illustrating the processing method of the high-strength conductive Cu-Ni-Si alloy strip provided by the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings.

[0020] like Figure 1 As shown in the figure, an embodiment of the present invention provides a processing method for high-strength conductive Cu-Ni-Si alloy strip, including the following steps.

[0021] S1. Weigh the casting raw materials according to the preset ratio range, and put the casting raw materials into the smelting furnace for smelting and casting to obtain ingots.

[0022] In this embodiment of the invention, the casting raw materials include Cu, Ni, Si, and impurities. The Cu raw material accounts for 97.3-98.5% of the total mass, the Ni raw material accounts for 1.0-1.9%, and the Si raw material accounts for 0.5-0.8%. The impurities include Fe, Pb, and trace impurities, with Fe accounting for ≤0.03% and Pb accounting for ≤0.002% of the total mass. The sum of the mass percentages of all raw materials is 100%.

[0023] In the process of obtaining casting raw materials, electrolytic copper with a purity of ≥99.99% is selected as Cu raw material, pure nickel with a purity of ≥99.95% is selected as Ni raw material, and industrial silicon with a purity of ≥99.9% is selected as Si raw material to ensure that the impurity content of the raw materials meets the requirements.

[0024] The casting raw materials are put into the melting furnace and melted until the casting raw materials are melted. Electromagnetic stirring is performed to obtain a molten liquid with uniform composition. The liquid is then held at the temperature for 40 to 60 minutes. The temperature inside the melting furnace is 1250 to 1300℃. The molten liquid is then poured into a casting mold at a temperature of 1180~1220℃; the poured molten liquid is cooled by water cooling to obtain an ingot, with a cooling rate of 8~12℃ / s. The ingot dimensions are 150mm×420mm×6000mm.

[0025] For example, the above-mentioned raw materials are accurately weighed according to the formula and put into a medium-frequency induction melting furnace. The melting temperature is controlled at 1250~1300℃. After the raw materials are completely melted, the electromagnetic stirring device in the furnace is turned on and stirred for 20~30 minutes to make the composition of the melt uniform. Then, it is held at the temperature for 40~60 minutes, during which argon gas protection is used to prevent the melt from oxidizing. After melting, the melt is poured into a casting mold at a temperature of 1180~1220℃. The mold size matches the target ingot. At the same time, the poured melt is cooled by water cooling at a rate controlled at 8~12℃ / s, and finally an ingot with dimensions of 150mm×420mm×6000mm is obtained.

[0026] S2. Place the ingot in a heating furnace for homogenization treatment.

[0027] The purpose of homogenization is to eliminate dendritic segregation in the ingot and ensure a uniform distribution of Ni and Si elements within the copper matrix. In practice, the ingot is placed in a box-type resistance heating furnace and heated to 950-980°C at a heating rate of 5°C / min. After reaching the target temperature, it is held at that temperature for 3-5 hours. After holding, the ingot is cooled to room temperature in the furnace, completing the homogenization process. This treatment reduces the Ni and Si segregation within the ingot to below 0.15, providing a uniform microstructure for subsequent plastic processing.

[0028] S3. The homogenized ingot is subjected to multiple hot rolling processes to obtain a hot-rolled strip blank, and the hot-rolled strip blank is subjected to double-sided milling to obtain a milled strip blank.

[0029] In this embodiment of the invention, the homogenized ingot is first subjected to hot rolling pretreatment. Specifically, the homogenized ingot is placed in a heating furnace, heated to 860~900℃ and held for 1.5~2.5 hours to ensure uniform temperature throughout the ingot and achieve the plastic state required for hot rolling, thus obtaining a pretreated ingot. Subsequently, 7~9 hot rolling processes are performed, with the deformation per pass controlled at 10%~40% to prevent cracking of the ingot due to excessive deformation in the early stages of hot rolling. During the hot rolling process, high-pressure water is used to cool the rolls, maintaining the roll surface temperature ≤150℃, ultimately obtaining a hot-rolled strip with a thickness of 16~17mm.

[0030] After hot rolling, the hot-rolled strip is subjected to double-sided milling to remove 0.8~1.2 mm of oxide layer and defect layer on the upper and lower surfaces to obtain milled strip.

[0031] For example, a CNC double-sided milling machine is used to mill the upper and lower surfaces of the strip blank by 0.8~1.2mm respectively to completely remove the oxide layer, rolling defect layer and microcracks on the surface; after milling, the surface roughness of the milled strip blank is inspected by a laser roughness tester to ensure that the surface roughness is ≤0.18μm, and the thickness dimensional tolerance is guaranteed to be ±0.05mm by multi-point measurement with a micrometer.

[0032] Through multi-pass hot rolling, the coarse columnar crystals inside the ingot are gradually broken down into fine equiaxed crystals. Simultaneously, a uniformly distributed dislocation network is introduced during the deformation process. Compared to the localized dislocation accumulation that easily occurs in traditional single-pass hot rolling with large deformation, this invention controls the deformation amount by 10% to 40% per pass, allowing dislocations generated in each deformation pass to diffuse uniformly and form a stable subgrain structure. The subgrain size can be controlled within 15 to 20 μm. This uniform subgrain structure not only provides a good plasticity foundation for subsequent cold rolling but also serves as uniform nucleation sites for Ni₂Si precipitates during subsequent aging treatment, avoiding coarsening of the precipitates caused by localized defects.

[0033] The subsequent double-sided milling process further eliminated the iron oxide scale and microcracks on the surface of the hot-rolled strip: the 0.8~1.2mm surface layer removed by milling included the CuO-Cu2O composite oxide layer (about 0.3~0.5mm thick) formed by high-temperature oxidation during hot rolling and the microcrack area of ​​1~2μm on the surface. After milling, the surface of the strip showed a uniform metallic luster, and the flatness error of the milled strip was ≤0.03mm / m as measured by a coordinate measuring machine, providing a flat processing base for the stable subsequent cold rolling.

[0034] S4. Perform multiple cold rolling processes on the milled strip blank, and perform at least one intermediate stress-relieving annealing process between the multiple cold rolling processes to obtain cold-rolled strip.

[0035] In this embodiment of the invention, the number of passes in the multi-pass cold rolling process is 3 to 5, the rolling speed per pass ranges from 0.3 to 2.3 m / s, the cold rolling deformation per pass ranges from 15 to 25%, and the cumulative cold rolling deformation ranges from 75 to 85%. Intermediate stress-relief annealing is performed when the cumulative cold rolling deformation reaches 40% to 60%, the annealing temperature for intermediate stress-relief annealing is 360 to 400°C, the holding time for annealing is 0.5 to 1.5 hours, and the thickness tolerance of the cold-rolled strip is ±0.02 mm.

[0036] For example, the cold rolling process uses a four-roll reversible cold rolling mill, with 3-5 passes: the first pass has a rolling speed of 0.3-0.5 m / s and a deformation of 20%-25%; subsequent passes gradually increase the rolling speed to 1.5-2.3 m / s, with a single pass deformation of 15%-20%, and a cumulative cold rolling deformation of 75-85%. When the cumulative cold rolling deformation reaches 40%-60%, intermediate stress-relieving annealing is performed: the cold-rolled strip is placed in a box-type resistance furnace, heated to 360-400℃, held for 0.5-1.5 hours, and then cooled to room temperature with the furnace. This treatment eliminates the processing stress generated during cold rolling, preventing cracking or warping of the strip in subsequent rolling. The final thickness of the cold-rolled strip is adjusted according to the target product, with a thickness tolerance controlled within ±0.02 mm.

[0037] S5. Place the cold-rolled strip into an electric resistance furnace and perform graded aging treatment on the cold-rolled strip to obtain Cu-Ni-Si alloy strip.

[0038] In this embodiment of the invention, the resistance furnace is in an argon atmosphere. The graded aging treatment includes pre-aging treatment and final aging treatment. The pre-aging treatment temperature is 400~420℃, and the holding time is 1.5~2.5 hours. The final aging treatment temperature is 460~480℃, and the holding time is 2.5~3.5 hours. The Cu-Ni-Si alloy strip includes dispersed Ni2Si precipitates. The tensile strength of the Cu-Ni-Si alloy strip ranges from 650~700MPa, the yield strength ranges from 620~660MPa, the elongation after fracture ranges from 12~15%, the electrical conductivity ranges from 58~62%IACS, the surface roughness is less than or equal to 0.1μm, and the dimensional tolerance is ±0.005mm.

[0039] Specifically, in the graded aging treatment of cold-rolled strip, a pre-aging treatment is first performed. The cold-rolled strip is placed in an electric resistance furnace and heated to 400~420℃, held for 1.5~2.5 hours. During this stage, a large number of fine Ni2Si precipitate nucleation sites are formed in the copper matrix. After pre-aging, the strip is cooled to room temperature in the furnace, and then a final aging treatment is performed. The strip is heated to 460~480℃ and held for 2.5~3.5 hours to promote the orderly growth of the precipitates and maintain their coherent relationship with the matrix. Argon gas is used for protection throughout the aging process to prevent oxidation of the strip surface. After the aging treatment, the strip is polished to finally obtain Cu-Ni-Si alloy strip. The Cu-Ni-Si alloy strip has a tensile strength of 650~700MPa, a yield strength of 620~660MPa, an elongation after fracture of 12~15%, an electrical conductivity of 58~62%IACS, a surface roughness of ≤0.1μm, and a dimensional tolerance of ±0.005mm, meeting the application requirements of high-performance fields.

[0040] The following three embodiments are provided to specifically illustrate the processing method of Cu-Ni-Si alloy strip provided by the present invention, and the performance of Cu-Ni-Si alloy strip prepared in the three embodiments is tested.

[0041] Example 1 (Optimal Process Parameters): 1. Raw material preparation and smelting / casting: Weigh the raw materials: 98.5% electrolytic copper (Cu≥99.99%), 1.0% pure nickel (Ni≥99.95%), and 0.5% industrial silicon (Si≥99.9%). The impurity content is controlled to be Fe≤0.03% and Pb≤0.002%, with the remainder being unavoidable trace impurities.

[0042] The raw materials were added to the melting furnace and held at 1250℃ for 40 minutes with continuous electromagnetic stirring to ensure uniform composition of the melt. Casting was then carried out at 1180℃ using water cooling (cooling rate 10℃ / s) to prepare ingots of 150mm×420mm×6000mm. The surface of the ingots showed no obvious defects such as porosity or shrinkage cavities.

[0043] 2. Homogenization treatment: The ingot is fed into a walking beam furnace and held at 960℃ for 4 hours. After homogenization, the dendritic segregation of the ingot is completely eliminated, the solid solubility of Ni and Si elements reaches more than 99.5%, and the grain size is uniform.

[0044] 3. Hot rolling treatment: 880℃ hot rolling mill using multi-pass hot rolling process (optimized pass count based on 150mm ingot): First pass: 150mm → 134mm (deformation 10.7%). Second pass: 134mm → 110mm (deformation 17.9%). Third pass: 110mm → 83mm (deformation 24.5%) 4th pass: 83mm → 58mm (deformation 30.1%) 5th pass: 58mm → 39mm (deformation 32.7%) 6th pass: 39mm → 24mm (deformation 38.1%) 7th pass: 24mm → 16.5mm (deformation 31.2%). The rolling speed for each pass is controlled at 1.0~3.0m / s, and a hot-rolled strip with a thickness of 16.5mm is finally obtained. The strip surface is smooth and free of cracks and oxide inclusions.

[0045] 4. Double-sided milling: A 16.5mm thick hot-rolled strip blank is fed into a double-sided milling machine to remove 1.0mm of oxide layer and defect layer from the upper and lower surfaces, finally obtaining a 14.5mm thick clean strip blank. The surface roughness Ra of the strip blank after milling is ≤0.15μm, and the dimensional tolerance is ±0.05mm.

[0046] 5. Multi-pass cold rolling and intermediate stress-relief annealing: The process involves five cold rolling passes using a four-roll reversible cold rolling mill, combined with one intermediate stress-relief annealing (designed to maintain deformation based on a 14.5mm net surface area blank). The specific process is as follows: First cold rolling: 14.5mm → 11.5mm (20.7%), rolling speed 0.3m / s; Second cold rolling: 11.5mm → 8.5mm (26.1%), rolling speed 1.5m / s; Third cold rolling: 8.5mm → 5.5mm (35.3%), rolling speed 1.8m / s; Stress-relief annealing: Hold at 380℃ for 1 hour; Fourth cold rolling: 5.5mm → 3.5mm (36.4%), rolling speed 2.0m / s; Fifth cold rolling pass: 3.5mm → 2.9mm (17.1%), rolling speed 2.2m / s; The cumulative deformation was 1 - (2.9 / 14.5) = 80%, which met the design requirements. A cold-rolled strip with a thickness of 2.9 mm was finally obtained. The strip surface was smooth, without edge cracks or wavy defects, and the dimensional tolerance was ±0.02 mm.

[0047] 6. Tiered timeliness processing: The cold-rolled strip is fed into an argon-protected aging furnace and subjected to a "low-temperature pre-aging + high-temperature final aging" process. Pre-aging: The temperature was increased to 410℃ at 5℃ / min and held for 2h to promote uniform nucleation of Ni2Si precipitates; Final aging: Continue heating to 470℃ (heating rate 5℃ / min), hold for 3 hours to allow the precipitated phase to grow appropriately and maintain coherence; After aging, the furnace is cooled to below 200°C, and then air-cooled to room temperature to obtain the finished Cu-Ni-Si alloy strip.

[0048] Example 2 (lower limit of parameters) A processing method for high-performance Cu-Ni-Si alloy strip, the specific steps of which are as follows: 1. Raw material preparation and smelting / casting: The raw material composition is Cu 97.3%, Ni 1.7%, Si 0.6%, Fe 0.03%, Pb 0.002%, with the remainder being unavoidable impurities. The smelting temperature is 1260℃, held for 30 minutes, and then cast into ingots of 150mm×420mm×6000mm.

[0049] 2. Homogenization treatment: Hold at 950℃ for 3 hours under argon protection, then cool with the furnace. Dendritic segregation in the ingot is eliminated, and Ni and Si are completely dissolved.

[0050] 3. Hot rolling treatment: Heat to 860℃ and hold for 1.5h, then perform multi-pass hot rolling (150mm→134mm→110mm→83mm→58mm→39mm→24mm→16.5mm, with deformation amounts of 10.7%, 17.9%, 24.5%, 30.1%, 32.7%, 38.7%, and 31.2% for each pass) at a rolling speed of 1.0~3.0m / s to obtain a 16.5mm thick hot-rolled strip.

[0051] 4. Double-sided milling: After milling, the blank thickness is 14.5mm, and the surface roughness Ra≤0.18μm.

[0052] 5. Multi-pass cold rolling and intermediate stress-relief annealing: 3 passes of cold rolling combined with 1 intermediate stress-relief annealing, with a cumulative deformation of 75%. First cold rolling pass: 14.5mm → 10.5mm (27.6%), rolling speed 1.0m / s; Second cold rolling: 10.5mm → 6.5mm (38.1%), rolling speed 1.3m / s; Intermediate stress-relief annealing: Hold at 380℃ for 1 hour; Third cold rolling: 6.5mm → 3.6mm (44.6%), rolling speed 1.6m / s; The cumulative deformation is 1 - (3.6 / 14.5) = 75.2%, which meets the requirements.

[0053] 6. Staged aging treatment: pre-aging at 400℃ for 1.5h, final aging at 460℃ for 2.5h, argon protection, and furnace cooling.

[0054] Example 3 (Parameter Upper Limit) A processing method for high-performance Cu-Ni-Si alloy strip, the specific steps of which are as follows: 1. Raw material preparation and smelting / casting: The raw material composition is Cu 97.7%, Ni 1.9%, Si 0.8%, Fe 0.02%, Pb 0.001%, with the remainder being unavoidable impurities. The smelting temperature is 1300℃, held for 50 min, and then cast into ingots of 150mm×420mm×6000mm.

[0055] 2. Homogenization treatment: Hold at 980℃ for 5 hours under argon protection, then cool with the furnace. The ingot has uniform grain size, and the Ni and Si solid solubility reaches 99.8%.

[0056] 3. Hot rolling treatment: Heat to 900℃ and hold for 2.5h, then perform multi-pass hot rolling (150mm→134mm→110mm→83mm→58mm→39mm→24mm→16.5mm, with deformation amounts of 10.7%, 17.9%, 24.5%, 30.1%, 32.7%, 38.7%, and 31.2% for each pass) at a rolling speed of 1.0~3.2m / s to obtain a 16.5mm thick hot-rolled strip.

[0057] 4. Double-sided milling: After milling, the blank thickness is 14.5mm and the surface roughness Ra≤0.12μm.

[0058] 5. Multi-pass cold rolling and intermediate stress-relief annealing: 4 passes of cold rolling combined with 1 intermediate stress-relief annealing, with a cumulative deformation of 85%. First pass: 14.5mm → 11.0mm (24.1%), rolling speed 1.3m / s; Second pass: 11.0mm → 7.5mm (31.8%), rolling speed 1.6m / s; Third pass: 7.5mm → 4.0mm (46.7%), rolling speed 1.9m / s; Stress-relief annealing: 380℃×1h; 4th pass: 4.0mm → 2.1mm (47.5%), rolling speed 2.3m / s; The cumulative deformation is 1 - (2.1 / 14.5) = 85.5%, which meets the requirements.

[0059] 6. Staged aging treatment: pre-aging at 420℃ for 2.5h, final aging at 480℃ for 3.5h, argon protection, and furnace cooling.

[0060] The performance of the Cu-Ni-Si alloy strips prepared in the above three embodiments was tested, and the test results are shown in Table 1:

[0061] As can be seen, Example 1 achieves the optimal balance between strength, plasticity, and conductivity, with fine and uniform grains and the best surface quality. Example 2 suffers from slightly lower strength and conductivity due to its lower parameters, while Example 3, although possessing the highest strength and best conductivity, has a narrower plasticity margin, and its excessively fine grains may affect the stability of subsequent forming. Considering both process robustness and service reliability, Example 1 is the preferred solution for industrial mass production.

[0062] The following two comparative examples further illustrate the technical advantages of the processing method for high-strength conductive Cu-Ni-Si alloy strip provided in this application.

[0063] Comparative Example 1 (Single cold rolling without intermediate annealing): A single cold rolling process (without intermediate stress-relief annealing) was adopted, and the number of hot rolling passes was adjusted simultaneously based on a 150mm ingot. The cumulative cold rolling deformation was 80%, and the remaining process parameters were the same as in Example 1.

[0064] Performance test results: tensile strength 625MPa, yield strength 595MPa, elongation after fracture 8%, electrical conductivity 45%IACS, obvious cracking at the strip edge, severe dislocation accumulation, and insufficient Ni2Si precipitate nucleation.

[0065] Comparative Example 2 (Single Aging Process) A single aging process (450℃×4h) was used instead of graded aging. The hot rolling parameters were adjusted based on a 150mm ingot, and the remaining process parameters were the same as in Example 1.

[0066] Performance test results: tensile strength 635MPa, yield strength 605MPa, elongation after fracture 11%, electrical conductivity 44%IACS, Ni2Si precipitates coarsened to 25nm, coherent relationship destroyed, strengthening effect weakened.

[0067] Comparative experiments show that the present invention significantly improves the comprehensive performance of Cu-Ni-Si alloy strip through the synergistic effect of homogenization optimization, multi-pass cold rolling combined with intermediate stress-relief annealing, and graded aging innovation. It solves the problems of uneven precipitate distribution, poor performance matching, and easy cracking of strip in traditional processes, and has significant technical advantages.

[0068] As can be seen from the above technical solution, this application provides a processing method for high-strength conductive Cu-Ni-Si alloy strip, comprising: weighing casting raw materials according to a preset proportion range, and feeding the casting raw materials into a melting furnace for melting and casting to obtain an ingot; placing the ingot in a heating furnace for homogenization treatment, performing multi-pass hot rolling treatment on the homogenized ingot to obtain a hot-rolled strip blank, and performing double-sided milling treatment on the hot-rolled strip blank to obtain a milled strip blank; performing multi-pass cold rolling treatment on the milled strip blank, and performing at least one intermediate stress-relieving annealing treatment between the multi-pass cold rolling treatment to obtain a cold-rolled strip; placing the cold-rolled strip in a resistance furnace, and performing graded aging treatment on the cold-rolled strip to obtain a Cu-Ni-Si alloy strip.

[0069] This invention achieves precise control over the alloy microstructure through a multi-pass hot rolling and cold rolling plastic processing scheme and a graded aging treatment process, thereby improving the strength and electrical conductivity of Cu-Ni-Si alloy strips. Multi-pass hot rolling, through controlled gradient deformation, gradually breaks down coarse grains in the ingot microstructure, forming a uniform subcrystalline structure, while simultaneously introducing an appropriate dislocation density for subsequent cold rolling. Intermediate stress-relief annealing effectively eliminates work hardening generated during cold rolling, avoiding cracking tendency caused by excessive dislocation accumulation and ensuring the formability of the cold-rolled strip. In the graded aging treatment stage, pre-aging at a lower temperature provides numerous nucleation sites for the Ni2Si precipitates, forming fine and uniformly distributed initial precipitates. Final aging at a higher temperature promotes the orderly growth of the precipitates while maintaining their coherence with the matrix, ultimately producing a high-strength, high-conductivity Cu-Ni-Si alloy strip.

[0070] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., 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 processing high-strength conductive Cu-Ni-Si alloy strip, characterized in that, include: Weigh the casting raw materials according to the preset proportion range, and put the casting raw materials into the melting furnace for melting and casting to obtain ingots. The casting raw materials include Cu raw materials, Ni raw materials, Si raw materials and impurities. The ingot is placed in a heating furnace for homogenization treatment at a temperature of 950-980°C for 3-5 hours. The homogenized ingot is subjected to multiple hot rolling processes to obtain a hot-rolled strip blank, and the hot-rolled strip blank is subjected to double-sided milling to obtain a milled strip blank. The milled strip is subjected to multiple cold rolling processes, and at least one intermediate stress-relieving annealing process is performed between the multiple cold rolling processes to obtain cold-rolled strip. The cold-rolled strip is placed in an electric resistance furnace and subjected to graded aging treatment to obtain Cu-Ni-Si alloy strip. The electric resistance furnace is in an argon atmosphere. The graded aging treatment includes pre-aging treatment and final aging treatment. The Cu-Ni-Si alloy strip includes dispersed Ni2Si precipitates.

2. The processing method of the high-strength conductive Cu-Ni-Si alloy strip according to claim 1, characterized in that, The preset proportion range of the casting raw materials is as follows: the mass percentage of Cu raw material is 97.3~98.5%, the mass percentage of Ni raw material is 1.0~1.9%, the mass percentage of Si raw material is 0.5~0.8%, and the impurities include Fe, Pb and trace impurities, with the mass percentage of Fe less than or equal to 0.03% and the mass percentage of Pb less than or equal to 0.002%. The sum of the mass percentages of Cu raw material, Ni raw material, Si raw material and impurities is 100%.

3. The processing method for the high-strength conductive Cu-Ni-Si alloy strip according to claim 2, characterized in that, The Cu raw material is electrolytic copper, and the purity of the Cu raw material is greater than or equal to 99.99%; the Ni raw material is pure nickel, and the purity of the Ni raw material is greater than or equal to 99.95%; the Si raw material is industrial silicon, and the purity of the Si raw material is greater than or equal to 99.9%.

4. The processing method of the high-strength conductive Cu-Ni-Si alloy strip according to claim 1, characterized in that, The step of feeding the casting raw materials into a smelting furnace for melting and casting to obtain ingots includes: The casting raw materials are put into a melting furnace and melted until they are molten. The furnace is then stirred electromagnetically to obtain a molten liquid with uniform composition. The liquid is then kept at a constant temperature for 40 to 60 minutes. The temperature inside the melting furnace is 1250 to 1300°C. The molten liquid is poured into a casting mold at a temperature of 1180~1220℃; The molten liquid after pouring is cooled by water to obtain the ingot. The cooling rate is 8~12℃ / s. The size of the ingot is 150mm×420mm×6000mm.

5. The processing method of the high-strength conductive Cu-Ni-Si alloy strip according to claim 1, characterized in that, The process of performing multiple hot rolling processes on the homogenized ingot to obtain a hot-rolled strip includes: The homogenized ingot is heated to 860~900℃ and held at that temperature for 1.5~2.5 hours to obtain a pretreated ingot. The pretreated ingot is subjected to 7 to 9 hot rolling processes to obtain the hot-rolled strip blank, the thickness of the hot-rolled strip blank is 16 to 17 mm, and the deformation of a single hot rolling pass is between 10% and 40%.

6. The processing method of the high-strength conductive Cu-Ni-Si alloy strip according to claim 1, characterized in that, The process of performing double-sided milling on the hot-rolled strip to obtain a milled strip includes: The hot-rolled strip is subjected to double-sided milling to remove 0.8~1.2 mm of oxide layer and defect layer on the upper and lower surfaces to obtain the milled strip. The surface roughness of the milled strip is less than or equal to 0.18 μm, and the thickness tolerance of the milled strip is ±0.05 mm.

7. The processing method of the high-strength conductive Cu-Ni-Si alloy strip according to claim 1, characterized in that, The number of passes in the multi-pass cold rolling process is 3 to 5, the rolling speed per pass is 0.3 to 2.3 m / s, the cold rolling deformation per pass is 15 to 25%, and the cumulative cold rolling deformation is 75 to 85%.

8. The processing method of the high-strength conductive Cu-Ni-Si alloy strip according to claim 7, characterized in that, The intermediate stress-relief annealing treatment is carried out when the cumulative cold rolling deformation reaches 40%~60%, the annealing temperature of the intermediate stress-relief annealing treatment is 360~400℃, the holding time of the annealing treatment is 0.5~1.5 hours, and the thickness tolerance of the cold-rolled strip is ±0.02mm.

9. The processing method of the high-strength conductive Cu-Ni-Si alloy strip according to claim 1, characterized in that, The pre-aging treatment temperature is 400~420℃, and the pre-aging treatment holding time is 1.5~2.5 hours; The final aging treatment is performed at a temperature of 460~480℃, and the holding time for the final aging treatment is 2.5~3.5 hours.

10. The processing method of the high-strength conductive Cu-Ni-Si alloy strip according to claim 1, characterized in that, The Cu-Ni-Si alloy strip has a tensile strength range of 650~700MPa, a yield strength range of 620~660MPa, an elongation after fracture range of 12~15%, a conductivity range of 58~62%IACS, a surface roughness of less than or equal to 0.1μm, and a dimensional tolerance of ±0.005mm.

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