Copper-nickel-silicon alloy strip and preparation method and application thereof

Abstract

The invention discloses a copper-nickel-silicon alloy strip and a preparation method and application thereof.The copper-nickel-silicon alloy strip comprises, by mass, 1.8 wt%-2.2 wt% of Ni, 0.4 wt%-0.6 wt% of Si, 0.04 wt%-0.12 wt% of Mg, 0.1 wt%-0.2 wt% of Cr, 0.01 wt%-0.03 wt% of P, the mass content of Ni and the mass content of Zn + Sn meet the condition that Ni / (Zn + Sn) is larger than 1.4 and smaller than 2.5, and the balance copper and inevitable impurities; the copper-nickel-silicon alloy strip comprises a second phase, the second phase is mainly composed of Ni2Si and CrSi3, and the size of the second phase ranges from 0.08 micrometer to 0.50 micrometer. The alloy strip has high strength, excellent conductivity and bending performance and good stress relaxation resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of copper alloys, and in particular to a copper-nickel-silicon alloy strip and a preparation method and application thereof. Background Art

[0002] As key components for current or signal transmission, connectors face increasing demands for higher-quality base materials to meet the growing demands for signal transmission and stability. Conventional tin-phosphorus bronze alloys, such as C5191 and C5210, despite their high strength and elasticity, lag behind copper-nickel-silicon alloys, such as C7025, in terms of stress relaxation resistance, electrical conductivity, and formability. Consequently, various grades of copper-nickel-silicon alloys have been developed for use in the production of various connectors.

[0003] Recent research has found that the strength and electrical conductivity of copper-nickel-silicon alloys are mutually exclusive. Improving the material's strength inevitably leads to a significant decrease in its electrical conductivity, and vice versa. Therefore, finding a balance between strength and electrical conductivity has become a hot topic of research.

[0004] Patent publication CN111621668B discloses a nickel-silicon copper alloy strip and its preparation method. The alloy strip comprises the following elements by weight: Ni: 0.8-1.5wt%, Si: 0.2-0.4wt%, Cr: 0.1-0.5wt%, Mg: 0.05-0.2%, with the remainder being Cu and impurities totaling no more than 0.3wt%. This nickel-silicon copper alloy achieves a tensile strength exceeding 450 MPa and a conductivity exceeding 45% IACS.

[0005] Patent document CN115044801B discloses a copper-nickel-silicon alloy strip and a preparation method thereof. The weight percentage composition of the strip is: Ni: 0.8~1.8%, Si: 0.15~0.35%, Zr: 0.003~0.08%, P: 0.01~0.07%, and the remainder is Cu and unavoidable impurities, and the weight content of Ni and Si satisfies 4≤Ni / Si≤6.2; the copper-nickel-silicon alloy strip of the invention has a tensile strength of above 465MPa and a conductivity of above 45%IACS.

[0006] While existing research has explored improving the performance of nickel-silicon-copper alloy strips, such as the alloys and preparation methods disclosed in the two aforementioned patents, which have achieved some improvement in the material's tensile strength and conductivity, these gains are limited. Furthermore, connector materials inherently experience temperature rise during use due to their inherent internal resistance, posing a significant challenge in ensuring they withstand the stress relaxation associated with this temperature rise.

[0007] In view of the above-mentioned deficiencies in the existing technology, it is urgent to prepare a copper-nickel-silicon alloy strip with good conductivity, bending performance and stress relaxation resistance by designing the alloy composition and process parameters while ensuring the strength of the strip. Summary of the Invention

[0008] In order to solve the problems existing in the prior art, the present invention provides a copper-nickel-silicon alloy strip, which has high strength, excellent conductivity and bending performance, and good resistance to stress relaxation.

[0009] The present invention provides a copper-nickel-silicon alloy strip, comprising the following components in percentage by weight: Ni: 1.8-2.2 wt%, Si: 0.4-0.6 wt%, Mg: 0.04-0.12 wt%, Cr: 0.1-0.2 wt%, and P: 0.01-0.03 wt%, wherein the mass contents of Ni and Zn+Sn satisfy 1.4<Ni / (Zn+Sn)<2.5, and the balance is copper and unavoidable impurities; The copper-nickel-silicon alloy strip includes a second phase, which is mainly Ni2Si and CrSi3. The size of the second phase is 0.08-0.5μm, and the distribution of the second phase is diffuse and uniform.

[0010] The present invention can inhibit the precipitation of Ni and Si elements by adding an appropriate amount of Cr element, thereby reducing the size of the second phase during the aging precipitation of Ni and Si elements. If the Cr content is excessive, a coarse CrSi3 second phase will be formed inside the crystal, resulting in a decrease in the bending performance of the material. The present invention also enriches Zn and Sn elements at the grain boundaries by adding an appropriate amount of Zn and Sn elements, so as to bind Ni and Si elements during the smelting process, avoid agglomeration, inhibit the nucleation and growth of the second phase of Ni and Si elements, and make the second phase distribution more uniform. If the Zn and Sn content is excessive, segregation will form at the grain boundaries, resulting in a decrease in the plasticity of the material. The above two methods make the size of the second phase within a smaller range. Since the second phase provided by the present invention is small in size and relatively evenly distributed, it has higher plasticity and stronger bending resistance. At the same time, due to its small size, it deforms less at higher temperatures and has stronger resistance to stress relaxation.

[0011] In addition, the solid solution strengthening formed by the Cr element and copper provided by the present invention can also compensate for the strength loss caused by the small size of the second phase. Therefore, the copper-nickel-silicon alloy strip provided by the present application has higher strength, and due to the addition of the Cr element, the content of the Ni element and the Si element can be further reduced, which is beneficial to improving the conductive properties of the material.

[0012] By controlling the contents of P and Mg, the present invention achieves deoxidation of molten copper during the smelting process and forms Mg3P2. This strengthens the alloy while increasing the density of the precipitated phase, thereby improving the material's resistance to stress relaxation. Furthermore, Mg has the ability to desulfurize, further purifying the molten copper.

[0013] Preferably, the copper-nickel-silicon alloy strip has a tensile strength of 620-680 MPa and an electrical conductivity of 58% IACS or above.

[0014] Preferably, at a temperature of 150°C, the plastic elongation strength Rp is specified. 0.2 Under the condition that 80% of the initial stress is maintained, the stress relaxation rate is no more than 19.5% after 168h.

[0015] Preferably, under the 180° bending condition, the strip does not crack when R / t≤1.0 is satisfied both perpendicular to the rolling direction and parallel to the rolling direction, where R is the bending radius and t is the strip thickness.

[0016] On the other hand, the present invention also provides a method for preparing the copper-nickel-silicon alloy strip, the process flow of which includes smelting → semi-continuous casting → hot rolling → initial rolling → first annealing → finished product rolling → aging annealing; The copper-nickel-silicon alloy strip is prepared and smelted according to the components thereof; The hot rolling temperature is 900-950° C., the holding time is 2-5 hours, and spraying is performed after hot rolling to achieve inadequate solution treatment.

[0017] The hot rolling process provided by the present invention can also be used as an insufficient solid solution treatment. Since the strip is still maintained at a temperature above 600°C after hot rolling, water spraying and rapid cooling are performed at this time, and the Ni and Si elements will not be fully dissolved. At the same time, due to the presence of Cr, its melting point is higher, and it is enriched at the grain boundaries of the hot-rolled grains, thereby suppressing the agglomeration of Ni and Si elements. In addition, the atomic radius of Cr is larger, and the lattice distortion produced is larger, which is more conducive to the solid solution of Si elements in this area. The final ratio of the mass percentage of (Ni + Si) within the grain and at the grain boundary is in the range of 1.0-1.2. During subsequent aging, a chromium-silicon second phase will precipitate, further suppressing the size of the nickel-silicon second phase. When the hot rolling temperature is too high or the holding time is too long, the solid solution effect of Ni and Si is better, and the regulatory effect of Cr cannot be fully exerted. When the hot rolling temperature is too low or the holding time is too short, the solid solution effect of Ni, Si and Cr will decrease, affecting the effect of subsequent second phase precipitation aging strengthening.

[0018] Preferably, the first annealing is performed in an air cushion furnace at a temperature of 800-900°C and a belt speed of 10-35 m / min. Under these annealing conditions, Ni and Si are dissolved before Cr, laying the foundation for subsequent second phase size control.

[0019] The present invention completely transforms the cold-worked structure of the initial rolling into a uniform recrystallized structure by controlling the temperature and holding time of the first annealing, thereby reducing the hardness and laying a foundation for subsequent processing. In addition, since the cooling of the air cushion furnace annealing belongs to quenching cooling, it can prevent excessive grain growth and avoid the agglomeration of Ni and Si elements at the grain boundaries. It can also perform a second solution treatment on the strip, so as to complete the solution of Ni and Si atoms that have not been completely dissolved in the copper matrix during the hot rolling process.

[0020] Preferably, the annealing temperature of the aging annealing is 430-450° C., and the holding time is 6-12 hours.

[0021] The present invention controls the annealing temperature and holding time. During hot rolling and the first annealing, an appropriate amount of Cr has already distributed Ni and Si in appropriate proportions within the grains. Therefore, under the annealing temperature and holding time provided by the present invention for aging annealing, a second phase, namely a nickel-silicon phase, can be fully and uniformly precipitated. The size of the second phase is relatively small, ranging from 0.08 to 0.50 μm, while minimizing strength degradation. Further preferably, the aging annealing is performed in a bell-shaped furnace.

[0022] Preferably, the smelting process is as follows: first, electrolytic copper plates are added according to the components of the copper-nickel-silicon alloy strip. After fusion, nickel ingots, copper-silicon master alloy, zinc ingots, and tin ingots are added. The temperature is raised to 1100-1150°C, followed by the addition of copper-chromium master alloy and holding for 1-2 hours. Finally, the copper-magnesium alloy is added to the molten copper, the temperature is raised to 1250-1300°C, and the temperature is held for 0.1-0.5 hours. Air blowing and deoxidation are performed throughout the smelting process. Because Zn and Sn have lower melting points, their content at grain boundaries is higher during casting. These elements synergistically regulate the solid solution effect of Ni and Si during hot rolling. The smelting temperature of the present invention is 1250-1300°C, ensuring a higher temperature gradient during cooling, maximizing the enrichment effect of Zn and Sn. When the smelting temperature is high, Zn burns out severely; when the smelting temperature is too low, cold shuts will appear on the surface of the ingot, ultimately affecting the surface quality of the material.

[0023] The present invention heats the copper liquid first and then adds the Cr element, which can reduce the agglomeration of Cr during the smelting process, improve the dispersibility of the Cr element in the copper matrix, and facilitate subsequent solid solution treatment.

[0024] Furthermore, preferably, before adding the copper-magnesium alloy, the copper-magnesium alloy is first placed in a copper tube, and then the copper tube containing the copper-magnesium alloy is pressed into the molten copper. The copper-magnesium alloy is added at the end of the smelting process and added in the form of a copper tube (the copper-magnesium alloy of the required composition is crushed and placed in a dried copper tube for later use). This can prevent the Mg element from burning during the smelting process, resulting in low Mg content and unsatisfactory mechanical properties of the material.

[0025] To control oxygen content and prevent connector cracking during processing and use, in addition to the aforementioned deoxidizing elements, the following deoxidation methods are employed during the smelting process. First, red-hot charcoal is placed on the surface of the molten copper in the smelting furnace to create a reducing atmosphere and reduce the ingress of oxygen from the air. Second, an air blowing device is installed beneath the smelting furnace, introducing argon gas at a flow rate of 5-30 LPM. This diffusion effect suppresses oxygen absorption by the molten copper at high temperatures.

[0026] Preferably, the semi-continuous casting temperature is 1230-1270° C. and the casting speed is 80-100 mm / min. The present invention controls the casting temperature and casting speed to control the liquid cavity depth of the ingot, thereby preventing subsequent hot rolling cracking.

[0027] Preferably, the initial rolling processing rate is selected to be 80-90%. The copper-nickel-silicon alloy series provided by the present invention is an age-hardened alloy. To reduce the impact of the precipitation and growth of the nickel-silicon phase on performance, the present invention minimizes the number of intermediate annealings, thus requiring the use of a high processing rate. However, when the processing rate exceeds 90%, the cold working performance of the strip decreases and the risk of edge cracking increases.

[0028] Preferably, the processing rate of the finished product rolling is 15-35%. Since the material of the present invention is mainly used in connectors, and the connector manufacturing process generally includes bending, while high processing rates can improve the material's strength, they will significantly reduce the material's plasticity. Therefore, the copper-nickel-silicon series materials provided by the present invention mainly utilize aging precipitation strengthening to improve the material's strength, thereby ensuring the material has good bending properties. Therefore, the above parameters are used for finished product rolling.

[0029] In another aspect, the present invention also provides the use of the copper-nickel-silicon alloy strip in connectors or plug-in connectors. The copper-nickel-silicon alloy strip of the present invention exhibits high strength, excellent electrical conductivity, bendability, and good stress relaxation resistance, making it suitable for connectors and plug-in connectors requiring bending or stamping.

[0030] Compared with the prior art, the present invention has the following beneficial effects: The present invention controls the content of Zn and Sn elements so that an appropriate amount of Zn and Sn can be distributed at the grain boundaries during the melting process, so as to bind the Ni and Si elements, minimize the aggregation of Ni and Si, and inhibit the nucleation and growth of the Ni and Si elements. The present invention controls the content of Cr element and adjusts the ratio range of the mass percentage of Ni and Si elements at the grain boundaries and in the crystal during solid solution, so that the size of the second phase precipitated subsequently is smaller. The smaller-sized second phase can improve the plasticity, thereby improving the bending resistance and the stress relaxation resistance at higher temperatures. Due to the supplement of solid solution strengthening formed by the addition of Cr element, a higher strength is maintained. Since part of the Ni and Si elements are replaced by Cr element, the proportion of Ni and Si elements is reduced, thereby improving the electrical conductivity. In summary, the present invention provides a copper-nickel-silicon alloy strip with high bending resistance, stress relaxation resistance, high electrical conductivity and suitable strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a second phase scanning electron microscope photograph of the copper-nickel-silicon alloy strip prepared in Example 1 of the present invention; Figure 2 This is a scanning electron microscope photograph of the ingot after semi-continuous casting of Comparative Example 11 of the present invention; Figure 3 This is a scanning electron microscope photograph of the hot-rolled billet of Comparative Example 11 of the present invention; Figure 4 This is a metallographic photograph of Comparative Example 11 of the present invention after aging; Figure 5 This is a scanning electron microscope photograph of the ingot after semi-continuous casting in Comparative Example 12 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be described below with reference to the following embodiments.

[0033] The present invention is illustrated using 10 examples and 12 comparative examples. The weight percentages of the chemical components of the alloy strips of each example and comparative example are shown in Table 1. The copper-nickel-silicon alloy strip preparation process for the 10 examples is as follows: smelting → semi-continuous casting → hot rolling → milling → initial rolling → air cushion furnace annealing → cleaning → finished product rolling → bell-shaped furnace aging annealing → finished product cleaning → shearing and slitting.

[0034] (1) Melting: First, add the electrolytic copper plate. After it is completely melted, add the nickel ingot and copper-silicon master alloy with the required composition. Heat it to 1100-1150℃. Then add the copper-chromium master alloy with the required composition and keep it warm for 1 hour. Finally, slowly press the copper tube containing the copper-magnesium alloy into the molten copper. Heat it to the melting temperature of 1250-1300℃ and keep it warm for 0.1-0.5 hours. Then perform direct reading spectrum test and analysis on the molten copper. Semi-continuous casting can only be carried out after the composition is qualified. If there is a deviation in the composition, adjust the molten copper composition until the composition is qualified before casting. During the entire smelting process, keep argon gas blowing into the furnace at a gas flow rate of 5-30LPM.

[0035] (2) Semi-continuous casting: casting temperature is 1230~1270℃, casting speed is 80~100mm / min, and ingot thickness is 180mm.

[0036] (3) Hot rolling: The ingot is subjected to large deformation hot rolling processing, the hot rolling heating temperature is 900-950℃, the holding time is 2-5h, the total processing rate of hot rolling is more than 90%, the thickness of the strip is 15.0mm, the final rolling temperature is 700℃, and then water is sprayed immediately for online solution treatment.

[0037] (4) Milling surface: The milling thickness of the upper and lower surfaces is 0.6-1.0mm respectively, so as to remove foreign matter such as oxide scale dissolved in the hot-rolled billet surface online, and prevent defects such as peeling during cold rolling.

[0038] (5) Initial rolling: Choose a processing rate of 80-90% for cold rolling to reduce the number of intermediate annealing times.

[0039] (6) Air cushion furnace annealing: Select 800-900℃ as annealing temperature and 10-35m / min as belt speed for air cushion furnace expansion annealing, laying the foundation for subsequent finished product cold rolling and aging annealing.

[0040] (7) Cleaning: Use three sets of cleaning brushes with mesh sizes of 400, 600 and 1200 respectively. The pressure reduction is controlled at 10-25% and the conveying speed is 35-55m / min.

[0041] (8) Finished product rolling: Cold rolling is performed at a processing rate of 15-35% to ensure that the strip has good bending performance.

[0042] (9) Bell furnace aging annealing: 430-450℃ as annealing temperature, 6-12h as holding time for aging annealing. Figure 1 As shown, after annealing at 440°C and holding time of 8 hours, the size of the second phase inside the strip is 0.08-0.5μm and is evenly distributed, which makes the strip have higher strength and better bending performance than conventional copper-nickel-silicon strip.

[0043] (10) Finished product cleaning: Use three sets of cleaning brushes with mesh sizes of 400, 600 and 1200 respectively. The pressure reduction is controlled at 5-15%, and the conveying speed is 30-60m / min.

[0044] (11) Cutting and striping: According to the subsequent connector substrate processing requirements, striping can be performed in any width within the range of 25-400mm.

[0045] The chemical composition of the copper-nickel-silicon alloy of the present invention is detailed in Table 1, the key process operating parameters are detailed in Table 2, and the performance test data of the alloy strip are detailed in Table 3.

[0046] The difference between Comparative Example 1 and Example 1 is that no Cr element is added. Other chemical compositions are shown in Table 1.

[0047] The difference between Comparative Example 2 and Example 1 is that no Zn element is added. Other chemical compositions are shown in Table 1.

[0048] The difference between Comparative Example 3 and Example 1 is that no Sn element is added. Other chemical compositions are shown in Table 1.

[0049] The difference between Comparative Example 4 and Example 1 is that the content of Mg element is 0.02 wt %. Other chemical compositions are shown in Table 1.

[0050] The difference between Comparative Example 5 and Example 1 is that no online spraying is performed during hot rolling.

[0051] The difference between Comparative Example 6 and Example 1 is that the hot rolling temperature is 700°C.

[0052] The difference between Comparative Example 7 and Example 1 is that the annealing temperature of the air cushion furnace is 750°C.

[0053] The difference between Comparative Example 8 and Example 1 is that the processing rate of the finished product rolling is 45%.

[0054] The difference between Comparative Example 9 and Example 1 is that the aging annealing temperature in the bell-jar furnace is 480°C.

[0055] The difference between Comparative Example 10 and Example 1 is that the aging annealing time in the bell-jar furnace is 4 h.

[0056] The difference between Comparative Example 11 and Example 1 is that the Cr content is 1.0%.

[0057] The difference between Comparative Example 12 and Example 1 is that the contents of Zn and Sn are 1.5% and 0.8%.

[0058] The above examples and comparative examples were analyzed for electrical conductivity, hardness, tensile strength, bending performance, stress relaxation resistance, elemental analysis, second phase particle morphology and distribution, and metallographic photographs.

[0059] Conductivity test: The test is carried out in accordance with the requirements of GB / T 32791-2016 Copper and copper alloy electrical conductivity eddy current test method, and the test strip size is 100mm×100mm.

[0060] Hardness test: carried out in accordance with the requirements of GB / T 4340.0-2009 Metallic materials Vickers hardness test Part 1: Test method. The test strip size is 30mm×30mm, the loading load is 1kg, and the loading time is 15s.

[0061] Tensile strength test: The room temperature tensile test is carried out on an electronic universal mechanical properties testing machine in accordance with GB / T 228.1-2010 Tensile tests on metallic materials - Part 1: Room temperature test methods. The test specimen is dumbbell-shaped, the tensile specimen width is 20 mm, and the tensile speed is 5 mm / min.

[0062] The bending performance test was carried out in accordance with GB / T 232-2010 Metallic Materials Bending Test Methods, with a bending angle of 180° parallel to the rolling direction and perpendicular to the rolling direction. The test strip had a width of 10 mm and a length of 50 mm.

[0063] Stress relaxation resistance testing was conducted in accordance with the requirements of GB / T 39152-2020 Copper and Copper Alloys - Bending Stress Relaxation Test Method. Sample width was 10 mm, and the length was sheared according to the standard. The test temperature was 150°C, and the stress relaxation rate was calculated using an initial stress of 80% of the specified plastic elongation strength Rp0.2.

[0064] The elemental analysis, precipitate particle size and distribution of the alloy were analyzed using a field emission scanning electron microscope JSM-IT700HR.

[0065] The metallographic photographs were taken using a Leica DMi8 metallographic microscope. The sample width is 10 mm and the length is 10 mm.

[0066] By comparing and analyzing the examples and comparative examples, it can be seen that the chemical composition and processing technology of the present invention have a significant impact on the performance of the strip. Figure 1As shown, after processing using the process described in the present invention, the secondary phase is mainly Ni2Si and CrSi3, with a size range of 0.08-0.50μm and a dispersed and uniform distribution in the matrix. Comparative Examples 1, 2, and 3 show that when no Cr, Zn, or Sn elements are added, the nickel-silicon secondary phase precipitated during aging is coarse, and the hardness and tensile strength of the strip are both low, failing to meet the strength requirements of the connector base material. Comparative Example 4 shows that when the Mg content is 0.02 wt%, not only does the hardness and strength of the strip decrease significantly, but the stress relaxation rate also increases significantly, indicating that the Mg content is crucial for improving the material's resistance to stress relaxation.

[0067] It can be seen from Comparative Example 5 that when hot rolling is not carried out with online spraying, the size of the nickel-silicon phase increases to 1.2 μm, the mechanical properties of the strip decrease slightly, but the bending performance decreases significantly, and the stress relaxation rate also increases; it can be seen from Comparative Example 6 that when the hot rolling temperature is 700°C, the solid solution effect of Ni and Si elements is poor, the final aging precipitation phase is also large, and the mechanical properties and bending properties of the strip are significantly reduced; it can be seen from Comparative Example 7 that when the air cushion furnace annealing temperature is 750°C, the size of the precipitate phase is also large, and the strength and hardness are not significantly improved.

[0068] From Comparative Example 8, it can be seen that since the strip is mainly strengthened by aging, although the finished product processing rate is increased to 45%, the mechanical properties of the strip are not significantly improved, but the bending performance of the strip is reduced; from Comparative Examples 9 and 10, it can be seen that the aging strengthening effect of the strip is closely related to the temperature and time of aging annealing. In order to ensure that the mechanical properties of the material meet the requirements of the connector base material, the annealing process must be carried out within the annealing process range of the claims of the present invention. From Comparative Example 11, it can be seen that if Figure 2 、 Figure 3 and Figure 4 As shown in FIG1 , the energy spectrum test shows that the Cr content in the ingot is 0.99% and 1.02% at the grain boundary, that is, there is no obvious difference in composition. After hot rolling, the Cr content in the grain boundary and in the grain is 0.95% and 1.05% respectively. The mass ratio of (Ni+Si) in the grain boundary and in the grain is 1.5. A coarse second phase exists in the final aged strip, and the electrical conductivity, bending performance and stress relaxation resistance of the strip are poor. Comparative Example 12 shows that Figure 5 As shown in Figure 3, when the Sn and Zn contents are high, the Sn and Zn contents at the grain boundaries in the ingot are high, which ultimately leads to a decrease in the electrical conductivity and bending performance of the aging strip.

[0069] Table 1 Composition of alloy strips of Examples and Comparative Examples Table 2 Key process control parameters of Examples and Comparative Examples Table 3 Properties of alloy strips of Examples and Comparative Examples As can be seen from Table 3, the alloy strips provided by Examples 1-10 of the present invention have suitable hardness, tensile strength, electrical conductivity, bending properties and stress relaxation rate.

Claims

1. A copper-nickel-silicon alloy strip, characterized in that: The invention comprises the following components in percentage by weight: Ni: 1.8-2.2 wt%, Si: 0.4-0.6 wt%, Mg: 0.04-0.12 wt%, Cr: 0.1-0.2 wt%, and P: 0.01-0.03 wt%, wherein the mass contents of Ni and Zn+Sn satisfy 1.4<Ni / (Zn+Sn)<2.5, and the balance is copper and unavoidable impurities; The copper-nickel-silicon alloy strip comprises a second phase, the second phase mainly comprises Ni2Si and CrSi3, and the size of the second phase is 0.08-0.50 μm.

2. The copper-nickel-silicon alloy strip according to claim 1, characterized in that: The copper-nickel-silicon alloy strip has a tensile strength of 620-680 MPa and an electrical conductivity of 58% IACS or more.

3. The copper-nickel-silicon alloy strip according to claim 1, characterized in that: At a temperature of 150°C, the specified plastic elongation strength Rp 0.2 Under the condition of 80% of the initial stress, the stress relaxation rate is not higher than 19.5% after 168h; Under the 180° bending condition, no cracking occurs when R / t≤1.0 is satisfied both perpendicular to and parallel to the rolling direction, where R is the bending radius and t is the strip thickness.

4. A method for preparing a copper-nickel-silicon alloy strip according to any one of claims 1 to 3, characterized in that: The process flow of the preparation method includes smelting → semi-continuous casting → hot rolling → initial rolling → first annealing → finished product rolling → aging annealing; The copper-nickel-silicon alloy strip is prepared and smelted according to the components thereof; The hot rolling temperature is 900-950° C., and the holding time is 2-5 hours.

5. The method for preparing the copper-nickel-silicon alloy strip according to claim 4, characterized in that: The hot rolling is followed by spraying, and the mass percentage of (Ni+Si) in the grains and at the grain boundaries of the billet after spraying is 1.0-1.

2.

6. The method for preparing the copper-nickel-silicon alloy strip according to claim 4, characterized in that: The first annealing is performed in an air cushion furnace, the temperature of the first annealing is 800-900° C., and the conveying speed is 10-35 m / min.

7. The method for preparing the copper-nickel-silicon alloy strip according to claim 4, characterized in that: Preferably, the annealing temperature of the aging annealing is 430-450° C., and the holding time is 6-12 hours.

8. The method for preparing the copper-nickel-silicon alloy strip according to claim 4, characterized in that: The smelting process is as follows: first, electrolytic copper plates are added according to the components of the copper-nickel-silicon alloy strip, and after fusion, nickel ingots, copper-silicon master alloys, zinc ingots and tin ingots are added, the temperature is raised to 1100-1150° C., and then copper-chromium master alloys are added, and the temperature is kept for 1-2 hours. Finally, copper-magnesium alloys are added to the copper liquid, the temperature is raised to 1250-1300° C., and the temperature is kept for 0.1-0.5 hours. Air blowing and deoxidation operations are always performed during the entire smelting process.

9. The method for preparing a copper-nickel-silicon alloy strip according to claim 4, wherein: The processing rate of the finished product rolling is 15-35%.

10. Use of the copper-nickel-silicon alloy strip according to any one of claims 1 to 3 in a connector or a connector.

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