A copper-nickel-silicon alloy strip and a method for producing the same

Abstract

This invention relates to a copper-nickel-silicon alloy strip, its preparation method, and its application. The copper-nickel-silicon alloy strip comprises Ni: 1.5-2.5 wt%, Si: 0.3-0.6 wt%, Mg: 0.005-0.05 wt%, Cr: 0.01-0.3 wt%, Sn: 0.05-0.4 wt%, Zn: 0.05-0.3 wt%, with the balance being Cu and unavoidable trace impurities. The preparation method of the copper-nickel-silicon alloy strip includes: batching and smelting → casting → hot rolling → rough rolling → first annealing → finished product rolling → aging heat treatment → second annealing. The batching and smelting are carried out according to the mass percentage of each element in the copper alloy. The aging heat treatment is a stepped aging heat treatment, first heating to 300-350℃ and holding for 1-2 hours, then raising the temperature to 420-480℃ and holding for 5-10 hours.

Description

Technical Field

[0001] This invention belongs to the field of copper alloy technology, specifically relating to a copper-nickel-silicon alloy strip, its preparation method, and its application. Background Technology

[0002] With the rapid development of the consumer electronics industry, electronic components are also being rapidly updated and iterated. These components are becoming increasingly miniaturized, but at the same time, the power used is increasing, and the requirements for service life and reliability are also becoming more stringent. Consequently, the requirements for connectors are becoming thinner, and their strength, elasticity, conductivity, and stress relaxation resistance are also becoming more demanding. Currently, some connector springs used in electronic devices are made of bronze C5210. Bronze has high strength and good elasticity, but its conductivity, bending resistance, resistance to high-temperature softening, and stress relaxation resistance cannot meet these requirements. Therefore, it is necessary to develop a high-strength, high-elasticity copper alloy strip to meet the needs of these connector springs.

[0003] CN107406915A discloses a copper alloy plate for use in connectors and a method for manufacturing the same. The copper alloy plate comprises the following elements by mass percentage: Ni: 1.0-5.0 wt%, Si: 0.1-2.0 wt%, and further contains at least one element selected from the group consisting of Sn: 0-0.5 wt%, Zn: 0-1.0 wt%, Mg: 0-0.2 wt%, Mn: 0-0.15 wt%, Cr: 0-0.2 wt%, Co: 0-1.5 wt%, Fe: 0-0.02 wt%, and Ag: 0-0.1 wt%. The remainder consists of copper and unavoidable impurities. The copper alloy plate of this invention can achieve a yield strength of 0.2% of 700 MPa or higher and a conductivity of 25% IACS or higher.

[0004] CN118019868A discloses a copper alloy sheet and its manufacturing method. The copper alloy sheet comprises the following elements by mass percentage: Ni or Co or a combination of both: 1.00-5.00 wt%, Si: 0.20-1.50 wt%, and the balance being Cu and unavoidable impurities. It may further contain at least one optional additive selected from the group consisting of Zn, Sn, Mg, Cr, and Fe, ranging from 0.10-1.00 wt%. The nickel-silicon copper alloy of this invention can achieve a tensile strength of 550 MPa or higher. The copper alloy sheet of this invention, manufactured by containing appropriate amounts of one or both of Ni and Co and Si under appropriate manufacturing conditions, can improve the tensile strength of the copper alloy sheet while reducing grain size variation caused by residual Si compounds. The invention mentions that if the Sn content exceeds 0.30 wt%, there is a tendency for decreased conductivity; therefore, the Sn content is preferably 0.10 wt% or higher and 0.30 wt%. Within the range of less than wt%.

[0005] CN101646792A discloses a copper alloy for electronic materials, containing Ni: 1.0-4.5 wt%, Si: 0.50-1.2 wt%, and Cr: 0.003-0.3 wt% (wherein the mass ratio of Ni to Si is 3 ≤ Ni / Si ≤ 5.5), and the remainder contains Cu and unavoidable impurities. This copper alloy can achieve a yield strength of 0.2% above 780 MPa, a conductivity of 40% IACS above, and Cr-Si compounds with a size of 0.1-5 μm dispersed in the material. The atomic concentration ratio of Cr to Si in the dispersed particles is 1-5, and the dispersion density is 1×10⁻⁶. 6 pcs / mm 2 the following.

[0006] Although existing technologies have been researched to improve the performance of nickel-silicon copper alloy strips, such as the alloys and preparation methods disclosed in the aforementioned patents, which have improved the tensile strength and conductivity of the materials to some extent, the improvement in tensile strength and conductivity is limited. Furthermore, connector materials inevitably experience temperature rise during use due to their inherent internal resistance; ensuring that the materials possess the ability to resist stress relaxation caused by temperature rise is also a problem that cannot be ignored.

[0007] In view of the shortcomings of the existing technology, there is an urgent need to prepare a copper-nickel-silicon alloy strip with good conductivity, bending performance, and stress relaxation resistance while ensuring the strength of the strip through the design of alloy composition and process parameters. This invention provides a copper alloy strip for connector contact springs and its preparation method. The prepared alloy strip has high strength, excellent resistance to high-temperature softening, and good conductivity. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention provides a copper-nickel-silicon alloy strip, which has high strength, high elasticity, excellent resistance to high-temperature softening, good bending resistance, and good electrical conductivity.

[0009] This invention provides a copper-nickel-silicon alloy strip comprising the following components by weight percentage: Ni: 1.5-2.5 wt%, Si: 0.3-0.6 wt%, Mg: 0.005-0.05 wt%, Cr: 0.01-0.3 wt%, Sn: 0.05-0.4 wt%, Zn: 0.05-0.3 wt%, with the balance being Cu and unavoidable trace impurities; Preferably, the weight percentages of each component in the copper-nickel-silicon alloy strip are: Ni: 2.0-2.5 wt%, Si: 0.3-0.5 wt%, Mg: 0.005-0.03 wt%, Cr: 0.1-0.2 wt%, Sn: 0.1-0.3 wt%, Zn: 0.1-0.3 wt%, with the balance being Cu and unavoidable trace impurities.

[0010] The copper-nickel-silicon alloy strip includes a second phase, which is Ni3Si or Ni2Si phase. Further, the second phase also includes a Cr phase. The average diameter of the second phase is ≤0.05 μm, and the second phase is dispersed, with a particle size distribution of 2000 particles / μm per unit area. 2 above.

[0011] This invention, by adding an appropriate amount of Cr, can significantly refine the grain structure, improve the hardness and strength of the material, and also enhance the copper alloy's resistance to high-temperature softening, stress relaxation, and wear resistance. After partial Cr solid solution matrix formation and aging treatment, nanoscale fine Cr phases can precipitate at the grain boundaries, further improving the material's mechanical strength. This invention improves the welding performance of this copper alloy by adding an appropriate amount of Zn. Zn can lower the welding temperature and increase the fluidity of the liquid and semi-solid metal in the weld pool, making it easier for the molten metal to fill the gaps in the weld and improving the weld quality. At the same time, Zn has a higher reducing power than Cu and can react with oxygen to generate ZnO during the welding process, avoiding the formation of brittle oxide CuO at the weld and further improving the welding quality of this alloy. This invention adds an appropriate amount of Sn element, which can form an α-phase solid solution with the copper matrix, thereby strengthening the copper alloy matrix and improving the alloy's elasticity and wear resistance. This invention improves the strength and high-temperature softening resistance of the alloy by adding appropriate amounts of Ni and Si elements, which form a second-phase strengthening phase δ-Ni2Si during aging heat treatment, and also form a second-phase strengthening phase β-Ni3Si for aging precipitation. This invention promotes the precipitation of Ni3Si, Ni2Si and Cr second-phase strengthening phases during aging heat treatment by adding an appropriate amount of Mg, while also refining the second-phase strengthening phases to ensure that the strengthening phases are uniformly dispersed on the matrix, thereby maximizing the strengthening effect of the second-phase precipitation. However, if the Mg content exceeds a certain amount, it will reduce the conductivity of this copper alloy. Therefore, in order to ensure the performance of this copper alloy, the Mg content is controlled at 0.005-0.05 wt.

[0012] The copper-nickel-silicon alloy strip has a yield strength ≥800MPa and a conductivity ≥60%IACS.

[0013] At a temperature of 120℃, with an initial stress of 50% of the yield strength, the stress relaxation rate after holding at this temperature for 1000 hours is no higher than 15%.

[0014] No cracking occurs under 180° bending conditions with R / T=0.8 in the Badway direction and R / T=0.5 in the Goodway direction, where R is the bending radius and t is the strip thickness.

[0015] 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 batching, smelting → casting → hot rolling → rough rolling → first annealing → finished product rolling → aging heat treatment → second annealing.

[0016] The batching and smelting steps are as follows: Electrolytic copper is added to the smelting furnace and heated to melt. It is then covered tightly with dry charcoal. The temperature is then raised to 1280-1350℃. Pure nickel, silicon, chromium, zinc, tin and magnesium are added according to the composition ratio. After 30-50 minutes, the slag is skimmed off and covered with a covering agent.

[0017] Preferably, the covering agent is a mixture of cryolite and sodium carbonate.

[0018] More preferably, cryolite and sodium carbonate are mixed in a ratio of 1:0.9-1.2.

[0019] More preferably, cryolite and sodium carbonate are mixed in a 1:1 ratio.

[0020] The casting process provided by this invention is a semi-continuous casting process. Specifically, the copper liquid temperature is controlled at 1220-1270℃, and the casting speed is 50-70 mm / min. During the casting process, the crystallizer is protected by a pure argon gas shield to isolate it from air. The pressure of the argon gas in the crystallizer is 0.005-0.01 MPa, and the flow rate is 30-60 mL / min. Red ingot casting is used, meaning the primary cooling water flow rate in the crystallizer is 20-30 m³ / h, the inlet water temperature is 20-30℃, the outlet water temperature is controlled at 40-50℃, the temperature of the ingot exiting the crystallizer is greater than 680℃, and there is no secondary cooling water after exiting the crystallizer.

[0021] The hot rolling process provided by this invention includes hot rolling and final rolling with online water cooling and quenching. The specific steps are as follows: The ingot is heated to a high temperature and held for 1-2 hours. Then, high-temperature rapid hot rolling is carried out to ensure the final rolling temperature. After final rolling, online water cooling and quenching are used to reduce the temperature of the copper strip.

[0022] Furthermore, the copper strip after online water-cooled quenching is milled.

[0023] The rough rolling process is controlled at a rough rolling rate of 80-98%. The copper-nickel-silicon alloys provided by this invention are age-hardening alloys. To reduce the impact on performance caused by the precipitation and growth of the nickel-silicon phase, this invention minimizes the number of intermediate annealing processes, thus requiring a high processing rate. However, when the processing rate exceeds 98%, the cold working performance of the strip decreases, and the risk of edge cracking increases.

[0024] Preferably, the roughing rate is controlled at 85-98%.

[0025] The rough-rolled product is trimmed.

[0026] The first annealing provided by this invention is solution gas cushion furnace annealing. The annealing method adopts high-temperature rapid annealing in a single-sheet unfolding gas cushion furnace, namely high-temperature rapid solution gas cushion furnace annealing. The heating section of the gas cushion furnace is 10-14m long, the air cooling section is 2.5-3.5m long, and the water cooling section is 2.5-3.5m long. After passing through the water cooling section, the temperature of the copper billet drops to below 40°C. The protective gas in the gas cushion furnace contains 2-4% H2 and the balance is nitrogen.

[0027] After solution annealing in an air cushion furnace, the average grain size of the strip is controlled within 8 μm, the strip hardness is 80-100 HV, the tensile strength is 350-400 MPa, the elongation is 45-55%, and the conductivity is 18-25% IACS.

[0028] Preferably, the finished product rolling process has a processing rate controlled between 45% and 75%. A processing rate of 45% or higher can effectively process the strip structure after solution annealing into a fibrous texture, allowing for recrystallization during subsequent stepped aging to refine the grain structure. Simultaneously, a processing rate of 45% or higher results in a larger distortion energy within the fibrous structure, effectively reducing the aging kinetics of the second phase and promoting the precipitation and dispersion of the second-phase strengthening phase. This ensures a higher quantity and smaller diameter of precipitated phases per unit area.

[0029] The aging heat treatment provided by this invention is a stepped aging heat treatment. After heat treatment, the grain size of the microstructure is ≤3μm, and the average diameter of the three strengthening phases Ni3Si, Ni2Si, and Cr precipitated is ≤0.05μm. Moreover, the number of second strengthening phase particles precipitated per unit area of ​​the microstructure is 2000 / μm. 2 above.

[0030] Cleaning: Degreasing using sodium hydroxide aqueous solution. Acid washing with sulfuric acid concentration of 130-160 g / L. Cleaning and drying in an oven at 75-95℃.

[0031] The aforementioned tension straightening is a 23-roll tension straightening system with a straightening elongation of 0.1-0.3% and a straightening tension of 120-180 N / mm. 2 .

[0032] The second annealing provided by this invention is an online stress-relief furnace annealing, using a single-sheet unfolding air cushion furnace annealing, with an annealing temperature of 450-480℃ and a copper strip tension of 150-200 N / mm inside the air cushion furnace. 2 Annealing rate 70-100 m / min, protective gas containing 2-4% H2 and balance nitrogen.

[0033] Preferably, during the batching and smelting processes, 90% high-purity nitrogen and 10% high-purity CO gas are introduced to deoxidize and degas the melt at a pressure of 0.05-0.15 MPa and a bottom-blowing gas flow rate of 15-25 L / min. This alloy contains Si and Mg elements, which are easily oxidized during smelting and casting. After oxidation, these alloying elements cannot be dissolved in the matrix during subsequent heat treatment and cannot precipitate with Ni and Si to form Ni3Si and Ni2Si strengthening phases. However, by introducing 90% high-purity nitrogen and 10% high-purity CO gas as inert and reducing gases, the oxidation of alloying elements during the smelting and casting process can be effectively avoided, ensuring the solid solution aging strengthening effect of the alloy.

[0034] Preferably, during the hot rolling process, the final rolling is carried out in the online water-cooled quenching and solution gas cushion furnace annealing process. The high-temperature rapid hot rolling process involves a temperature of 900-1050℃, a holding time of 1-2 hours, and a rolling speed of 150-250 m / min. Preferably, the temperature of the high-temperature rapid hot rolling is 920-1000℃. The final rolling process involves online water cooling and quenching. The final rolling temperature is above 720°C, and online water cooling and quenching is performed within 10 seconds of the final rolling to reduce the temperature of the copper strip to below 120°C.

[0035] Preferably, the final rolling temperature is 720-800℃, and the temperature of the copper strip after quenching is reduced to 60-120℃.

[0036] The annealing temperature of the high-temperature rapid solution air cushion furnace is 870-920℃, and the annealing speed is 30-50m / min.

[0037] High-temperature rapid hot rolling followed by online water-cooled quenching and high-temperature rapid solution gas cushion furnace annealing significantly improves the solid solubility of the alloy, maximizing the dissolution of Ni, Si, and Cr elements in the copper alloy microstructure within the α matrix. This provides favorable conditions for the dispersion and precipitation of the second phase during subsequent aging heat treatment, increasing the precipitating force of the second phase and facilitating its full precipitation and refinement. Consequently, this further enhances the strength, resistance to high-temperature softening, bending properties, and electrical conductivity of the alloy material.

[0038] Preferably, in the stepped aging heat treatment process, the furnace is first heated to 300-350℃ and held for 1-2 hours, then heated to 420-480℃ and held for 5-10 hours. Using this microstructure-controlled stepped aging treatment process, the second-phase Ni3Si, Ni2Si, and Cr second-phase reinforcing phases are fully precipitated, ensuring that the conductivity is controlled above 60% IACS. Simultaneously, this process ensures that the average diameter of the precipitated reinforcing phase is within 0.05 μm, and the number of second-phase reinforcing phase particles precipitated per unit area is less than 2000 / μm. 2 The above achieves the optimal effect of second-phase dispersion strengthening, greatly improving the material's strength, conductivity, and resistance to high-temperature softening.

[0039] On the other hand, the present invention also provides the application of the copper-nickel-silicon alloy strip in connectors or plugs. The copper-nickel-silicon alloy strip of the present invention possesses high strength, excellent conductivity, bending performance, and good resistance to stress relaxation, making it suitable for connectors, plugs, etc., that require bending or stamping processes.

[0040] Compared with the prior art, the beneficial effects of this invention are as follows: This invention promotes the precipitation of Ni3Si, Ni2Si and Cr second strengthening phases during aging heat treatment by controlling the content of Mg and Cr elements. At the same time, it refines the second strengthening phases and ensures that the strengthening phases are uniformly dispersed on the matrix, thereby maximizing the strengthening effect of the second phase precipitation, improving the hardness and strength of the material, and also enhancing the copper alloy's resistance to high-temperature softening, stress relaxation resistance and wear resistance.

[0041] This invention significantly improves the solid solubility of the alloy through a process of high-temperature rapid hot rolling followed by online water-cooled quenching and high-temperature rapid solution gas cushion furnace annealing. This maximizes the dissolution of Ni, Si, and Cr elements in the copper alloy microstructure within the α matrix, providing favorable conditions for the strengthening and dispersed precipitation of the second phase during subsequent aging heat treatment. In other words, it increases the precipitation motive force of the second phase during subsequent aging heat treatment, facilitating the full precipitation and refinement of the second phase, thereby further improving the strength, high-temperature softening resistance, bending properties, and electrical conductivity of the alloy material. Attached Figure Description

[0042] Figure 1 This is a scanning electron microscope (SEM) image of the second phase of the copper-nickel-silicon alloy strip obtained in Example 4 of the present invention. Detailed Implementation

[0043] Those skilled in the art can refer to the content of this document and appropriately replace and / or modify the process parameters to achieve the desired results. However, it should be particularly noted that all similar replacements and / or modifications are obvious to those skilled in the art and are considered to be included in this invention. The products and preparation methods described in this invention have been described through preferred examples, and those skilled in the art can obviously modify or appropriately change and combine the products and preparation methods described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0044] Unless otherwise defined, the technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention pertains. This invention uses the methods and materials described herein; however, other suitable methods and materials known in the art may also be used. The materials, methods, and examples described herein are illustrative only and are not intended to be limiting. All publications, patent applications, patent cases, provisional applications, database entries, and other references mentioned herein are incorporated herein by reference in their entirety. In case of conflict, the definitions included in this specification shall prevail.

[0045] Unless otherwise stated, all percentages, parts, proportions, etc. are by weight; other statements include, but are not limited to, “wt%” meaning weight percentage, “mol%” meaning mole percentage, and “vol%” meaning volume percentage.

[0046] When quantities, concentrations, or other numerical values ​​or parameters are given as ranges, preferred ranges, or a series of upper and lower preferred values, it should be understood that they specifically disclose all ranges formed by any pair of values ​​of any larger or preferred range limit and any smaller or preferred range limit, regardless of whether the ranges are disclosed separately. For example, when describing a range of “1 to 5 (1-5)”, the described range should be understood to include ranges such as “1 to 4 (1-4)”, “1 to 3 (1-3)”, “1 to 2 (1-2)”, “1 to 2 (1-2) and 4 to 5 (4-5)”, “1 to 3 (1-3) and 5”, etc. Unless otherwise stated, where numerical ranges are described herein, the ranges are intended to include the range endpoints as well as all integers and fractions within that range.

[0047] When the term “about” is used to describe the endpoint of a numerical value or range, the disclosure should be understood to include the specific value or endpoint referred to.

[0048] Furthermore, unless explicitly stated otherwise, "or" refers to an inclusive "or" rather than an exclusive "or". For example, any of the following conditions apply to condition A "or" B: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist).

[0049] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of the invention are intended to indicate that the number of times the said element or component appears (i.e., occurs) is not limited. Therefore, “a” or “an” should be understood to include one or at least one, and unless the quantity is explicitly stated to be singular, the singular form of the elements or components also includes the plural case.

[0050] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the phrase "comprising an element defined as..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0051] Unless otherwise specified, the materials, methods, and examples described herein are exemplary and not limiting. While similar or equivalent methods and materials can be used to implement or test the invention, suitable methods and materials are described herein.

[0052] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0053] This invention selects 10 embodiments and 7 comparative examples for illustration. The mass percentage of the chemical composition of the alloy strip in each embodiment and comparative example is shown in Table 1. The preparation process of the copper-nickel-silicon alloy strip in the 10 embodiments is as follows: batching and melting → semi-continuous casting → hot rolling + final rolling with online water cooling quenching → milling → rough rolling → edge trimming → solution gas cushion furnace annealing → finished product rolling → stepped aging heat treatment → cleaning → 23-roll bending and straightening → online stress-relief furnace annealing → slitting and packaging.

[0054] 1) Batching and Smelting: Electrolytic copper is added to the smelting furnace and heated to melt. The molten copper in the furnace must be tightly covered with dry charcoal, with a charcoal covering thickness of 100-150 mm, ensuring no copper is exposed to air. The temperature is then raised to 1280-1350℃, and pure nickel, silicon, chromium, zinc, tin, and magnesium are added according to the specified proportions. After 30-50 minutes, slag is skimmed off. A covering agent of cryolite and sodium carbonate in a 1:1 ratio is used for further covering, with a covering thickness of 70-90 mm. The three gas diffusers installed at the furnace bottom are opened, and 90% high-purity nitrogen and 10% high-purity CO gas are introduced to deoxidize and degas the melt. The gas pressure is 0.05-0.15 MPa, and the bottom-blowing gas flow rate is 15-25 L / min. After holding the gas for 20-40 minutes, the temperature of the molten copper is lowered to 1220-1270℃ to begin casting.

[0055] 2) Semi-continuous casting: The copper molten metal is cast at a temperature controlled between 1220-1270℃, with a casting speed of 50-70 mm / min. During the casting process, the crystallizer is protected by a pure argon gas shield to isolate it from air. The argon gas pressure inside the crystallizer is 0.005-0.01 MPa, and the flow rate is 30-60 mL / min. Red ingot casting is used, meaning the primary cooling water flow rate in the crystallizer is 20-30 m³ / h, the inlet water temperature is 20-30℃, and the outlet water temperature is controlled at 40-50℃. The temperature of the ingot exiting the crystallizer is greater than 680℃, and there is no secondary cooling water after exiting the crystallizer. The ingot casting dimensions are 180*630mm*8000mm.

[0056] 3) Hot rolling + final rolling with online water cooling and quenching: The ingot is heated to 920℃-1000℃ and held at that temperature for 1-2 hours. Then, hot rolling begins at a speed of 150-250 m / min, ensuring the final rolling temperature is above 720℃. Simultaneously, online water quenching is performed within 10 seconds of the final rolling to reduce the copper strip temperature to below 120℃. The thickness after hot rolling is 12.5±0.5 mm, and the width after widening is 650±5 mm.

[0057] 4) Milling: The milling amount on one side is 0.5-0.8mm, and the thickness after milling is 11±0.5mm.

[0058] 5) Rough rolling: The rough rolling processing rate is controlled at 85-98%.

[0059] 6) Edge trimming: 7-8mm on one side, resulting in a width of 635±0.5mm after trimming. 7) Solution annealing in an air cushion furnace: A single-sheet unfolded air cushion furnace is used for annealing at a temperature of 870-920℃ and a speed of 30-50 m / min. The heating section of the air cushion furnace is 12m long, the air-cooling section is 3m long, and the water-cooling section is 3m long. After the water-cooling section, the temperature of the copper billet drops below 40℃. The protective gas in the air cushion furnace contains 2-4% H2 and the balance is nitrogen. After solution annealing, the average grain size of the strip is controlled within 8μm, the strip hardness is 80-100HV, the tensile strength is 350-400MPa, the elongation is 45-55%, and the conductivity is 18-25%IACS.

[0060] 8) Finished product rolling: The processing rate is controlled at 45-75%.

[0061] 9) Stepped aging heat treatment: First, heat to 300-350℃ in a bell-jar furnace and hold for 1-2 hours. Then, raise the temperature to 420-480℃ and hold for 5-10 hours. After heat treatment, the grain size of the microstructure should be ≤3μm, and the average diameter of the three strengthening phases Ni3Si, Ni2Si, and Cr precipitated should be ≤0.05μm, with the number of second strengthening phase particles precipitated per unit area of ​​the microstructure being 2000 / μm. 2 above.

[0062] 10) Cleaning: Degreasing with sodium hydroxide aqueous solution. Acid washing with sulfuric acid concentration of 130-160 g / L. Cleaning and drying in an oven at 75-95℃.

[0063] 11) 23-roll tension straightening: straightening elongation rate is 0.1-0.3%, straightening tension is 120-180 N / mm 2 .

[0064] 12) Online stress-relief furnace annealing: Single-sheet unfolded air cushion furnace annealing is adopted, with an annealing temperature of 450-480℃ and a copper strip tension of 150-200 N / mm inside the air cushion furnace. 2Annealing rate 70-100 m / min, protective gas containing 2-4% H2 and balance nitrogen.

[0065] 13) Finished product slitting and packaging.

[0066] The chemical composition details of the copper-nickel-silicon series alloys of the present invention are shown in Table 1, and the key process operation parameters are shown in Table 2. The performance test data of the alloy strip are detailed in Table 3.

[0067] The difference between Comparative Example 1 and Example 4 is that no Cr element was added to the alloy elements.

[0068] The difference between Comparative Example 2 and Example 4 is that in step 7), solution annealing is performed in an air cushion furnace. A single-sheet unfolding air cushion furnace is used for annealing at a temperature of 650°C and a speed of 25 m / min.

[0069] The difference between Comparative Example 3 and Example 4 is that in step 9), a stepped aging heat treatment is performed. The temperature is raised to 315°C and held for 1.9 hours. Then the temperature is raised to 540°C and held for 9.5 hours.

[0070] The difference between Comparative Example 4 and Example 4 is that the content of Zn in the alloying elements is 0.550 wt%.

[0071] The difference between Comparative Example 5 and Example 4 is that the Si content in the alloying elements is 0.90 wt%.

[0072] The difference between Comparative Example 6 and Example 4 is that the content of Mg in the alloying elements is 0.100 wt%.

[0073] The difference between Comparative Example 7 and Example 4 is that step 9) heat treatment did not use stepped aging heat treatment. The temperature was raised to 320°C and held for 10 hours.

[0074] Mechanical property testing: The room temperature tensile test was conducted on an electronic universal mechanical property testing machine in accordance with GB / T 228.1-2010 Metallic materials, tensile testing - Part 1: Room temperature test method. A 20 mm wide specimen with a head was used, and the tensile speed was 5 mm / min.

[0075] Hardness testing: The test was conducted in accordance with the requirements of GB / T 4340.0-2009 Metallic Materials Vickers Hardness Test - Part 1: Test Method. The test strip size was 30mm × 30mm, the load was 1 kg, and the loading time was 15 s.

[0076] Conductivity test: According to GB / T 3048.2-2007 Electrical properties test method for wires and cables Part 2: Resistivity test for metallic materials, expressed as %IACS.

[0077] Metallographic grain size test: The grain size in the photographs acquired under a 5000x metallographic microscope was tested according to the intercept method in GB / T 6394-2007, "Method for Determination of Average Grain Size of Metals". The sample width was 10 mm and the length was 10 mm.

[0078] Bending test: A 10mm wide sample is taken in the Badway direction and bent 180° with a bending radius R=0.8T (band thickness). The bent area is then observed under an optical microscope for cracks. Similarly, a 10mm wide sample is taken in the Goodway direction and bent 180° with a bending radius R=0.5T (band thickness). The bent area is then observed under an optical microscope for cracks.

[0079] High-temperature softening resistance test: After holding at 300℃ for 100 hours, the strength and hardness were tested and calculated.

[0080] Tensile strength test: The room temperature tensile test was conducted on an electronic universal mechanical performance testing machine in accordance with GB / T 228.1-2010 Metallic materials, tensile testing - Part 1: Room temperature test method. The test specimen was dumbbell-shaped, the width of the tensile specimen was 20 mm, and the tensile speed was 5 mm / min.

[0081] Stress relaxation resistance test: The stress relaxation resistance test requires 120℃, initial stress of 50% of yield strength, and 1000h heat preservation, and then the stress relaxation rate is calculated.

[0082] Composition analysis: The laboratory direct-reading spectrometer was used to perform composition analysis according to the standard "YS / T 482-2022 Analysis Methods for Copper and Copper Alloys: Spark Discharge Atomic Emission Spectrometry".

[0083] The size and distribution of the precipitated phases in the alloy were analyzed using field emission scanning electron microscopy.

[0084] Metallographic photographs were taken using a metallographic microscope.

[0085] Table 1 Chemical composition (wt%) of the embodiments and comparative examples of the present invention

[0086] Table 2 Key process parameter control of embodiments and comparative examples of the present invention

[0087] Table 3. Organization and performance of embodiments and comparative examples of the present invention.

[0088] Comparative analysis of the embodiments and comparative examples demonstrates that the chemical composition and processing technology of the present invention have a significant impact on the performance of the strip. The above embodiments and comparative examples were analyzed for conductivity, hardness, tensile strength, bending performance, stress relaxation resistance, elemental analysis, second phase morphology and distribution, and metallographic photographs.

[0089] like Figure 1 As shown, after processing using the process described in this invention, the second phase mainly consists of Ni3Si, Ni2Si, and Cr, with an average diameter ≤0.050μm, and is uniformly distributed in a diffuse manner within the matrix.

[0090] Comparative Example 1 shows that when no Cr element is added, the nickel-silicon second phase precipitated during aging is coarse, and the hardness and tensile strength of the strip are both low, which does not meet the strength requirements of the connector substrate material.

[0091] Comparative Example 2 shows that when the annealing temperature of the air cushion furnace is 650℃, the solid solution effect of Ni and Si elements is poor, the final precipitated phase during aging is also large, and the mechanical properties and bending properties of the strip are significantly reduced.

[0092] As can be seen from Comparative Example 3, since the strip is mainly strengthened by aging heat treatment, when the aging heat treatment temperature is too high, the solid solubility gradient difference between Ni and Si precipitates is small, resulting in incomplete precipitation of Ni and Si. At the same time, the aging temperature of 540℃ exacerbates the growth of the precipitated phase.

[0093] Comparative Example 4 shows that when the Zn content is 0.55 wt%, the Zn content at the grain boundaries in the ingot is relatively high, which ultimately leads to a decrease in the conductivity and bending performance of the aged strip.

[0094] As shown in Comparative Example 5, when the Si content is 0.90 wt%, the Si content exceeds the content required to form Ni3Si and Ni2Si, resulting in excess Si being dissolved in the matrix, which greatly reduces the conductivity of the alloy and also reduces its plasticity.

[0095] As shown in Comparative Example 6, when the Mg content is 0.10 wt%, excess Mg will form coarse and brittle intermetallic compounds Mg2Si with Ni and Si in the alloy. These compounds cannot play a dispersive strengthening role and instead reduce the plasticity of the alloy, leading to bending and cracking. At the same time, excessive Mg content leads to a decrease in the conductivity of the alloy.

[0096] Comparative Example 7 shows that when step aging heat treatment was not used, but instead heating to 320℃ and holding for 10 hours, this heat treatment did not meet the conditions for complete aging precipitation of the alloy. As a result, the dissolved Si and Ni in the alloy did not precipitate completely, and therefore the conductivity, strength, and high-temperature softening resistance were not significantly improved.

[0097] As can be seen from Table 3, the alloy strips provided in Examples 1-10 of the present invention have suitable hardness, tensile strength, electrical conductivity, bending performance and stress relaxation rate.

Claims

1. A copper-nickel-silicon alloy strip, characterized by, It includes the following components in weight percentage: Ni: 1.5-2.5 wt%, Si: 0.3-0.6 wt%, Mg: 0.005-0.05 wt%, Cr: 0.01-0.3 wt%, Sn: 0.05-0.4 wt%, Zn: 0.05-0.3 wt%, with the balance being Cu and unavoidable impurities; The copper-nickel-silicon alloy strip includes a second phase, which comprises Ni3Si and Ni2Si phases, and the average diameter of the second phase is ≤0.05μm.

2. The Cu-Ni-Si alloy strip according to claim 1, wherein the second phase is in a dispersed state, and the number of second phase particles precipitated per unit area of the structure is 2000 / μm2. 2 above; preferably, the second phase further includes a Cr phase.

3. The Cu-Ni-Si alloy strip according to claim 1, characterized by The yield strength of the copper-nickel-silicon alloy strip is ≥800MPa, and the conductivity is ≥60%IACS.

4. The Cu-Ni-Si alloy strip according to claim 1, characterized by At a temperature of 120℃, with an initial stress of 50% of the yield strength, the stress relaxation rate after 1000h of heat preservation is no higher than 15%; under 180° bending conditions, no cracking occurs with R / T=0.8 in the Badway direction and R / T=0.5 in the Goodway direction, where R is the bending radius and t is the strip thickness.

5. A method of producing the copper-nickel-silicon alloy strip according to any one of claims 1 to 4, characterized by, The process flow of the preparation method includes batching, smelting → casting → hot rolling → rough rolling → first annealing → finished product rolling → aging heat treatment → second annealing.

6. The method for preparing copper-nickel-silicon alloy strip according to claim 5, characterized in that, The hot rolling process includes hot rolling and final rolling with online water cooling and quenching. The hot rolling temperature is 900-1050℃ and the rolling speed is 150-250m / min. Preferably, the hot rolling temperature is 920-1000℃; After hot rolling, the copper strip undergoes final rolling and online water cooling quenching at a final rolling temperature of 720°C or higher. The final rolling temperature is reduced to below 120°C within 10 seconds by online water cooling quenching.

7. The method for preparing copper-nickel-silicon alloy strip according to claim 5, characterized in that, The first annealing is solution annealing in an air cushion furnace, with an annealing temperature of 870-920℃ and an annealing rate of 30-50m / min.

8. The method of producing a copper-nickel-silicon alloy strip according to claim 5, characterized by, The second annealing is an online stress-relief furnace annealing, with an annealing temperature of 450-480℃ and an annealing speed of 70-100m / min.

9. The method of producing a copper-nickel-silicon alloy strip according to claim 5, characterized by, The finished product has a processing rate of 45-75%, and the aging heat treatment is a stepped aging heat treatment, first heating to 300-350℃ and holding for 1-2 hours, and then heating to 420-480℃ and holding for 5-10 hours.

10. The application of a copper-nickel-silicon alloy strip according to any one of claims 1-4 or a copper-nickel-silicon alloy strip prepared by the preparation method according to any one of claims 5-9 in a connector or plug.

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