Copper alloy and preparation method thereof

Abstract

This invention provides a copper alloy and its preparation method. The copper alloy has the following mass percentage composition: Ni: 0.5–2.0 wt%, S: 0.3–0.8 wt%, P: 0.1–0.3 wt%, Sn: 0.1–0.2 wt%, Si: 0.05–0.2 wt%, with the balance being Cu and unavoidable impurities. The microstructure of the copper alloy contains Cu₂S particles. This invention designs the composition and microstructure of the copper alloy, particularly controlling the content range of Ni, P, and Si elements to give the material high strength and high conductivity. Furthermore, the addition of S element forms Cu₂S particles, thereby improving the material's machinability and facilitating its fabrication into connector components.

Description

Technical Field

[0001] This invention relates to the field of copper alloy technology, and more specifically, to a copper alloy and its preparation method. Background Technology

[0002] High strength and high conductivity have always been the performance requirements for connector materials. With the rapid rise of the new energy market and the rapid development of miniaturization in electronic products, even higher demands are placed on the strength and conductivity of connector materials. Connector terminals are usually machined using Swiss-type lathes, which requires high machinability of the materials to improve processing efficiency.

[0003] Currently, there are few copper alloys on the market that combine high strength, high conductivity, and easy machining. Only C19160 (Pb: 0.8-1.2, Ni: 0.8-1.2, P: 0.15-0.35, Cu: balance) has achieved commercial application. However, this alloy contains Pb, an element harmful to the human body. With increasing environmental awareness, lead-containing copper alloys may face the possibility of being banned. Therefore, in the field of connector materials, there is an urgent need to develop a high-strength, high-conductivity, and easy-machining copper alloy material. Summary of the Invention

[0004] The technical problem to be solved by the present invention is how to provide a copper alloy material that has high strength, high conductivity, easy machinability, and is lead-free.

[0005] To solve the above-mentioned technical problems, the present invention provides a copper alloy, wherein the mass percentage composition of the copper alloy is Ni: 0.5-2.0 wt%, S: 0.3-0.8 wt%, P: 0.1-0.3 wt%, Sn: 0.1-0.2 wt%, Si: 0.05-0.2 wt%, with the balance being Cu and unavoidable impurities, and the microstructure of the copper alloy has Cu2S particles.

[0006] This invention designs the composition and microstructure of copper alloys and controls the content range of Ni, P, and Si elements to give the material high strength and high conductivity. By adding S element to form Cu2S particles, the machinability of the material is improved, making it easier to process into connector components.

[0007] Furthermore, in the copper alloy composition, the ratio of the mass of Ni to the sum of the masses of Si and P, Ni / (Si+P), is 3 to 4. By controlling the proportions of Ni, P, and Si elements, the material can possess both high strength and high electrical conductivity.

[0008] Furthermore, the microstructure of the copper alloy comprises Ni3P particles, Ni5P2 particles, and Ni2Si particles. The design precipitates Ni, P, and Si elements in the copper alloy as intermetallic compounds, which significantly improves the material's strength while reducing the negative impact of P and Si on conductivity.

[0009] Furthermore, the copper alloy has a strength ≥ 550 MPa, a conductivity ≥ 45%, and a relative cutting index ≥ 60% compared to C36000. The relative cutting index = (cutting force of copper alloy / cutting force of C36000) × 100%. This invention provides a lead-free copper alloy material with high strength, high conductivity, and easy machinability, suitable for manufacturing connectors.

[0010] The present invention also provides a method for preparing the above-mentioned copper alloy, comprising the following steps:

[0011] S1. Mechanical alloying: Cu powder and S powder are mixed in a molar ratio of 2:1 and ball-milled to obtain Cu2S powder;

[0012] S2. Ingredients: Prepare ingredients according to the required composition;

[0013] S3. Smelting: Electrolytic copper, nickel ingots, tin ingots and copper-silicon master alloy are melted in sequence. In order to avoid oxidation of Cu2S and phosphorus copper alloy and cause composition fluctuations, Cu2S powder and phosphorus copper alloy are wrapped in copper sheet and added to the furnace to smelt and obtain ingots.

[0014] S4. Hot extrusion: heating the ingot and then extruding it to obtain a wire rod.

[0015] S5. Pickling: The wire rod is pickled to remove the oxide layer;

[0016] S6. Cold working in one step: The wire blank is cold deformed;

[0017] S7. Solution treatment: The wire blank after one cold working is subjected to online solution treatment;

[0018] S8. Secondary cold working: The solution-treated wire blank is cold-deformed again;

[0019] S9. Aging: The wire blank after secondary cold working is subjected to aging treatment;

[0020] S10. Finished product processing: The aging-treated wire blank is drawn into a finished product.

[0021] This invention employs a process combining mechanical alloying and smelting to form stable Cu2S particles in the alloy, and through specific heat treatment and processing techniques, achieves high strength, high conductivity, and easy-to-cut properties in lead-free copper alloy materials.

[0022] In a preferred or optional embodiment, step S1 specifically includes: placing a mixture of Cu powder and S powder in a ball mill jar, with a steel ball to mixed powder mass ratio of 10-30:1; evacuating the ball mill jar and filling it with argon gas; and ball milling unidirectionally at a speed of 400-500 r / min for 2-6 hours. Stable Cu2S powder is prepared by mechanical alloying, and then the Cu2S powder is added to the alloy through melting, forming stable Cu2S particles in the alloy. These Cu2S particles are hard and brittle, and can play a good chip-breaking role in machining.

[0023] In a preferred or optional embodiment, step S4 specifically includes: heating the ingot to 700-850°C, extruding it in a horizontal extrusion press to obtain a wire rod, and controlling the extrusion speed to be 2-5 mm / s.

[0024] In a preferred or optional embodiment, the processing rate of the first cold working in step S6 is 50% to 70%, the processing rate of the second cold working in step S8 is 30% to 60%, and the processing rate of the finished product processing in step S10 is 10% to 20%. Controlling the processing rate of the first cold working is beneficial to achieving sufficient and uniform precipitation of the precipitated phase and to ensuring that the material has sufficient cold deformation storage energy; controlling the processing rate of the second cold working is beneficial to promoting the precipitation of the precipitated phase in the aging step.

[0025] In a preferred or optional embodiment, the melting temperature in step S3 is 1150–1250°C, and the solution temperature in step S7 is 750–800°C. The solution temperature is controlled to allow the Ni, P, and Si elements in the alloy to dissolve in the copper matrix.

[0026] In a preferred or optional embodiment, in step S9, the aging temperature is 420–470°C, and the holding time is 1–5 hours. Controlling the aging temperature and time allows intermetallic compounds such as Ni3P, Ni5P2, and Ni2Si to precipitate, thereby improving the strength of the alloy.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) This invention achieves lead-free, high-strength, high-conductivity, and easy-to-cut copper alloys by adding Ni, S, P, Sn, and Si elements to copper and by certain heat treatment and processing techniques. The prepared copper alloy has a tensile strength ≥550MPa, conductivity ≥45%, and machinability equivalent to more than 60% of C36000, and has a good application prospect in the field of connectors.

[0029] (2) Regarding the addition of S element in the alloy, the present invention adopts a combination of mechanical alloying and conventional smelting. That is, firstly, a relatively stable Cu2S powder is prepared by mechanical alloying, and then a certain amount of Cu2S powder is added to the alloy through smelting. This process can avoid S from being oxidized during smelting, which would make the composition difficult to control and the SO2 gas produced by oxidation would be harmful to the human body and the environment. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0031] A specific embodiment of the present invention provides a copper alloy containing the following elements and mass percentages: Ni: 0.5-2.0 wt%, S: 0.3-0.8 wt%, P: 0.1-0.3 wt%, Sn: 0.1-0.2 wt%, Si: 0.05-0.2 wt%, impurities, and the balance being Cu, wherein the ratio of the mass of Ni to the sum of the masses of Si and P is Ni / (Si+P) = 3-4, and its chemical composition is shown in the table below.

[0032] Table 1 Composition of Copper Alloy Materials

[0033] Ni S P Sn Si other Cu 0.5-2.0 0.3-0.8 0.1-0.3 0.1-0.2 0.05-0.2 <0.1 margin

[0034] The microstructure of copper alloys consists of Cu2S particles, Ni3P particles, Ni5P2 particles, and Ni2Si particles. Ni3P, Ni5P2, and Ni2Si particles can improve the strength of the alloy, while Cu2S particles can improve the machinability of the alloy.

[0035] The specific design principles of the alloy composition are as follows:

[0036] Ni, P, Si: Ni can be infinitely dissolved in Cu. Although Ni has some strengthening effect when dissolved in Cu, the strengthening effect is limited. After certain heat treatment, Ni, P, and Si elements in copper alloys can precipitate as intermetallic compounds such as Ni3P, Ni5P2, and Ni2Si. These precipitates can significantly improve the strength of the material and also reduce the negative impact of P and Si on conductivity. Due to the incomplete phase transformation reaction, it is difficult to remove P and Si elements dissolved in copper alloys through heat treatment. To maximize the conductivity of the material, the Ni content should be appropriately higher than the P+Si content, while the P+Si content should not be too low; otherwise, the amount of intermetallic compounds precipitated in the material will be limited, and the strengthening effect will be unclear. Therefore, in this invention, while satisfying their respective proportions, the Ni:(P+Si) ratio of the copper alloy should be maintained between 3 and 4 to ensure that the material has both high strength and high conductivity.

[0037] Sulfur (S): Sulfur has zero solid solubility in Cu at room temperature. During solidification, S in Cu alloys forms Cu₂S particles. These particles are hard and brittle, providing excellent chip breaking properties during machining. Furthermore, since S exists as Cu₂S at room temperature, electron scattering is reduced, resulting in minimal impact on the conductivity of the copper alloy. Therefore, adding S to copper alloys can improve machinability with negligible effect on conductivity. However, when the S content is below 0.3 wt%, the improvement in chip breaking performance is not significant; when the S content is above 0.8 wt%, the material becomes more brittle and prone to cracking at high machining rates; when the S content is between 0.3 and 0.8 wt%, both machinability and high machining rates are maintained without cracking.

[0038] Sn: Sn can dissolve in the Cu matrix, negatively impacting the conductivity of Cu. However, Sn dissolved in Cu can significantly increase the lattice distortion of Cu, resulting in a significant increase in the material's strength after cold working. When the Sn content is less than 0.1 wt%, the effect on the copper lattice distortion is small, and the strengthening effect is not significant. When the Sn content is greater than 0.2 wt%, the copper lattice distortion is large, increasing the negative impact on conductivity and causing an excessive decrease in conductivity. In this invention, Sn is controlled at 0.1–0.2 wt%, which ensures both the material's strength and maintains high conductivity.

[0039] In a specific embodiment, the method for preparing the copper alloy includes the following steps:

[0040] S1, Mechanical Alloying

[0041] Cu powder and S powder are mixed in a molar ratio of 2:1 and placed in a stainless steel ball mill jar. The mass ratio of steel balls to powder is 10 to 30:1. The ball mill jar is evacuated and filled with argon gas. The mixture is ball-milled unidirectionally at a speed of 400 to 500 r / min for 2 to 6 hours to obtain Cu2S powder.

[0042] S2, Ingredients

[0043] Prepare the ingredients according to the required composition.

[0044] S3, Smelting

[0045] Semi-continuous casting is adopted. During the smelting process, 20-30cm thick charcoal is used to cover the furnace. Electrolytic copper, nickel ingots, tin ingots, and copper-silicon master alloy are melted in sequence. Then, Cu2S powder and phosphorus copper alloy are wrapped in copper sheet and added to the furnace. The smelting temperature is 1150-1250℃ to obtain the ingot.

[0046] S4, Hot Extrusion

[0047] The ingot is heated to 700-850℃ and extruded in a horizontal extrusion press to obtain a wire rod, with the extrusion speed controlled at 2-5 mm / s.

[0048] S5, pickling

[0049] The extruded wire blank is placed in a solution of water, nitric acid, and sulfuric acid for pickling to obtain a wire blank without an oxide layer.

[0050] S6, One-time cold processing

[0051] The pickled wire blanks are then drawn or cold rolled, with a processing rate of 50-70%.

[0052] S7, solid solution

[0053] The cold-worked wire blank is subjected to online solution treatment so that the Ni, P and Si elements in the alloy are dissolved in the copper matrix. The temperature of the wire blank is controlled at 750-800℃.

[0054] S8, Secondary Cold Working

[0055] The solution-treated wire blank is then drawn or cold-rolled again, with a processing rate of 50-70%.

[0056] S9, Timeliness

[0057] After secondary cold working, the wire blank undergoes aging treatment at a temperature of 420–470℃ for 1–5 hours.

[0058] S10, Finished Product Processing

[0059] The aged wire blanks are then drawn into finished products, with a processing rate of 10-20%.

[0060] There are two problems with conventional smelting methods for sulfur (S): first, S readily combines with oxygen, making composition difficult to control; second, the SO2 gas produced by the oxidation of S is harmful to human health and the environment. To improve the machinability of the alloy by adding S, while avoiding oxidation during smelting and the environmental and personnel hazards during production, this invention employs a combination of mechanical alloying and conventional smelting. First, relatively stable Cu2S powder is prepared using mechanical alloying, and then a certain amount of Cu2S powder is added to the alloy through smelting. The copper alloy prepared by this invention has the following properties: tensile strength ≥ 550 MPa, electrical conductivity ≥ 45%, and a relative cutting index ≥ 60% compared to leaded brass C36000. The relative cutting index is calculated as: (Cu alloy cutting force / C36000 cutting force) × 100%.

[0061] The technical solution and effects of the present invention will be illustrated below with specific embodiments.

[0062] Example 1

[0063] The mass percentage composition of the copper alloy is as follows: Ni: 0.8wt%, S: 0.3wt%, P: 0.15wt%, Sn: 0.1%; Si: 0.06%, with the balance being Cu. The ratio of the mass of Ni to the sum of the masses of Si and P is Ni / (Si+P) = 3.81.

[0064] The preparation steps are as follows:

[0065] 1) Mechanical alloying: Cu powder and S powder are mixed in a molar ratio of 2:1 and placed in a stainless steel ball mill jar. The mass ratio of steel balls to powder is 20:1. The ball mill jar is evacuated and filled with argon gas. The ball mill is unidirectionally milled at a speed of 400 r / min for 6 hours.

[0066] 2) Ingredients: Prepare ingredients according to the required composition.

[0067] 3) Smelting: Semi-continuous casting is adopted. During the smelting process, 20-30cm thick charcoal is used to cover the furnace. Electrolytic copper, nickel ingots, tin ingots and copper-silicon intermediate alloy are melted in sequence. Then, Cu2S powder and phosphorus copper alloy are wrapped in copper sheet and added to the furnace. The smelting temperature is 1180℃ to obtain ingots.

[0068] 4) Hot extrusion: The ingot is heated to 750℃ and extruded in a horizontal extrusion press to obtain a wire rod, with the extrusion speed controlled at 4mm / s.

[0069] 5) Pickling: The extruded wire blank is placed in a solution of water, nitric acid and sulfuric acid for pickling to obtain a wire blank without an oxide layer.

[0070] 6) Single cold working: The pickled wire blank is drawn or cold rolled, with a processing rate of 55%.

[0071] 7) Solution treatment: The cold-worked wire blank is subjected to online solution treatment, and the temperature of the wire blank is controlled at 760℃.

[0072] 8) Secondary cold working: The solution-treated wire blank is subjected to cold deformation at a processing rate of 40%.

[0073] 9) Aging: The wire blank after the second cold working is subjected to aging treatment at a temperature of 450℃ for 5 hours.

[0074] 10) Finished product processing: The aged wire blanks are drawn into finished products, with a processing rate of 11%.

[0075] Example 2

[0076] The mass percentage composition of the copper alloy is as follows: Ni: 1.2wt%, S: 0.5wt%, P: 0.2wt%, Sn: 0.15%; Si: 0.15%, with the balance being Cu. The ratio of the mass of Ni to the sum of the masses of Si and P is Ni / (Si+P) = 3.43.

[0077] The preparation steps are as follows:

[0078] 1) Mechanical alloying: Cu powder and S powder are mixed in a molar ratio of 2:1 and placed in a stainless steel ball mill jar. The mass ratio of steel balls to powder is 20:1. The ball mill jar is evacuated and filled with argon gas. The ball mill is unidirectionally milled at a speed of 450 r / min for 6 hours.

[0079] 2) Ingredients: Prepare ingredients according to the required composition;

[0080] 3) Smelting: Semi-continuous casting is adopted. During the smelting process, 20-30cm thick charcoal is used to cover the metal. Electrolytic copper, nickel ingots, tin ingots, and copper-silicon master alloy are melted in sequence. Then, Cu2S powder and phosphorus copper alloy are wrapped in copper sheet and added to the furnace. The smelting temperature is 1200℃ to obtain ingots.

[0081] 4) Hot extrusion: The ingot is heated to 800℃ and extruded in a horizontal extrusion press to obtain a wire rod, with the extrusion speed controlled at 5mm / s;

[0082] 5) Pickling: The extruded wire blank is placed in a solution of water, nitric acid and sulfuric acid for pickling to obtain a wire blank without an oxide layer;

[0083] 6) Single cold working: The pickled wire blank is drawn or cold rolled, with a processing rate of 60%;

[0084] 7) Solution treatment: The cold-worked wire blank is subjected to online solution treatment, and the temperature of the wire blank is controlled at 780℃;

[0085] 8) Secondary cold working: The solution-treated wire blank is subjected to cold deformation again with a processing rate of 30%;

[0086] 9) Aging: The wire blank after the second cold working is subjected to aging treatment at a temperature of 455℃ for 4 hours.

[0087] 10) Finished product processing: The aged wire blanks are drawn into finished products, with a processing rate of 13%.

[0088] Example 3

[0089] The mass percentage composition of the copper alloy is as follows: Ni: 1.9wt%, S: 0.75wt%, P: 0.3wt%, Sn: 0.18%; Si: 0.2%, with the balance being Cu. The ratio of the mass of Ni to the sum of the masses of Si and P is Ni / (Si+P) = 3.80.

[0090] The preparation steps are as follows:

[0091] 1) Mechanical alloying: Cu powder and S powder are mixed in a molar ratio of 2:1 and placed in a stainless steel ball mill jar. The mass ratio of steel balls to powder is 20:1. The ball mill jar is evacuated and filled with argon gas. The ball mill is unidirectionally milled at a speed of 500 r / min for 6 hours.

[0092] 2) Ingredients: Prepare ingredients according to the required composition;

[0093] 3) Smelting: Semi-continuous casting is adopted. During the smelting process, 20-30cm thick charcoal is used to cover the metal. Electrolytic copper, nickel ingots, tin ingots, and copper-silicon master alloy are melted in sequence. Then, Cu2S powder and phosphorus copper alloy are wrapped in copper sheet and added to the furnace. The smelting temperature is 1250℃ to obtain ingots.

[0094] 4) Hot extrusion: The ingot is heated to 850℃ and extruded in a horizontal extrusion press to obtain a wire rod, with the extrusion speed controlled at 4.5mm / s;

[0095] 5) Pickling: The extruded wire blank is placed in a solution of water, nitric acid and sulfuric acid for pickling to obtain a wire blank without an oxide layer;

[0096] 6) Single cold working: The pickled wire blank is drawn or cold rolled, with a processing rate of 50%;

[0097] 7) Solution treatment: The cold-worked wire blank is subjected to online solution treatment, and the temperature of the wire blank is controlled at 800℃;

[0098] 8) Secondary cold working: The solution-treated wire blank is subjected to cold deformation at a processing rate of 60% again;

[0099] 9) Aging: The wire blank after the second cold working is subjected to aging treatment at a temperature of 470℃ for 1 hour.

[0100] 10) Finished product processing: The aged wire blanks are drawn into finished products, with a processing rate of 19%.

[0101] Comparative Example 1

[0102] The mass percentage composition of the copper alloy is: Ni: 0.8wt%, P: 0.15wt%, with the balance being Cu.

[0103] The preparation steps are as follows:

[0104] 1) Ingredients: Prepare ingredients according to the required composition;

[0105] 2) Smelting: Semi-continuous casting is adopted. During the smelting process, 20-30cm thick charcoal is used to cover the furnace. Electrolytic copper and nickel ingots are melted in sequence. Phosphorus copper alloy is wrapped with copper sheet and added to the furnace. The smelting temperature is 1180℃ to obtain ingots.

[0106] 3) Hot extrusion: The ingot is heated to 750℃ and extruded in a horizontal extrusion press to obtain a wire rod, with the extrusion speed controlled at 4mm / s;

[0107] 4) Pickling: The extruded wire blank is placed in a solution of water, nitric acid and sulfuric acid for pickling to obtain a wire blank without an oxide layer;

[0108] 5) Single cold working: The pickled wire blank is drawn or cold rolled, with a processing rate of 55%;

[0109] 6) Solution treatment: The cold-worked wire blank is subjected to online solution treatment, and the temperature of the wire blank is controlled at 760℃;

[0110] 7) Secondary cold working: The solution-treated wire blank is subjected to cold deformation again with a processing rate of 40%;

[0111] 8) Aging: The wire blank after the second cold working is subjected to aging treatment at a temperature of 450℃ for 5 hours.

[0112] 9) Finished product processing: The aged wire blanks are drawn into finished products, with a processing rate of 11%.

[0113] Comparative Example 2

[0114] The mass percentage composition of the copper alloy is: Ni: 1.2wt%, S: 0.5wt%, P: 0.2wt%, with the balance being Cu.

[0115] The preparation steps are as follows:

[0116] 1) Mechanical alloying: Cu powder and S powder are mixed in a molar ratio of 2:1 and placed in a stainless steel ball mill jar. The mass ratio of steel balls to powder is 20:1. The ball mill jar is evacuated and filled with argon gas. The ball mill is unidirectionally milled at a speed of 450 r / min for 6 hours.

[0117] 2) Ingredients: Prepare ingredients according to the required composition;

[0118] 3) Smelting: Semi-continuous casting is adopted. During the smelting process, 20-30cm thick charcoal is used to cover the ingots. Electrolytic copper and nickel ingots are melted in sequence. Then, Cu2S powder and phosphorus copper alloy are wrapped in copper sheet and added to the furnace. The smelting temperature is 1200℃ to obtain ingots.

[0119] 4) Hot extrusion: The ingot is heated to 800℃ and extruded in a horizontal extrusion press to obtain a wire rod, with the extrusion speed controlled at 5mm / s;

[0120] 5) Pickling: The extruded wire blank is placed in a solution of water, nitric acid and sulfuric acid for pickling to obtain a wire blank without an oxide layer;

[0121] 6) Single cold working: The pickled wire blank is drawn or cold rolled, with a processing rate of 60%;

[0122] 7) Solution treatment: The cold-worked wire blank is subjected to online solution treatment, and the temperature of the wire blank is controlled at 780℃;

[0123] 8) Secondary cold working: The solution-treated wire blank is subjected to cold deformation again with a processing rate of 30%;

[0124] 9) Aging: The wire blank after the second cold working is subjected to aging treatment at a temperature of 455℃ for 4 hours.

[0125] 10) Finished product processing: The aged wire blanks are drawn into finished products, with a processing rate of 13%.

[0126] Comparative Example 3

[0127] The mass percentage composition of the copper alloy is: Ni: 1.9wt%, P: 0.3wt%, Sn: 0.18%; Si: 0.2%, with the balance being Cu.

[0128] The preparation steps are as follows:

[0129] 1) Ingredients: Prepare ingredients according to the required composition;

[0130] 2) Smelting: Semi-continuous casting is adopted. During the smelting process, 20-30cm thick charcoal is used to cover the furnace. Electrolytic copper, nickel ingots, tin ingots, copper-silicon master alloy are melted in sequence. Phosphorus copper alloy is wrapped with copper sheet and added to the furnace. The smelting temperature is 1250℃ to obtain ingots.

[0131] 3) Hot extrusion: The ingot is heated to 850℃ and extruded in a horizontal extrusion press to obtain a wire rod, with the extrusion speed controlled at 4.5mm / s;

[0132] 4) Pickling: The extruded wire blank is placed in a solution of water, nitric acid and sulfuric acid for pickling to obtain a wire blank without an oxide layer;

[0133] 5) One-time cold working: The pickled wire blank is drawn or cold rolled, with a processing rate of 50%;

[0134] 6) Solution treatment: The cold-worked wire blank is subjected to online solution treatment, and the temperature of the wire blank is controlled at 800℃;

[0135] 7) Secondary cold working: The solution-treated wire blank is subjected to cold deformation at a processing rate of 60% again;

[0136] 8) Aging: The wire blank after the second cold working is subjected to aging treatment at a temperature of 470℃ for 1 hour.

[0137] 9) Finished product processing: The aged wire blanks are drawn into finished products, with a processing rate of 19%.

[0138] Comparative Example 4

[0139] The mass percentage composition of the copper alloy is as follows: Ni: 0.8wt%, S: 0.3wt%, P: 0.15wt%, Sn: 0.1%; Si: 0.06%, with the balance being Cu. The ratio of the mass of Ni to the sum of the masses of Si and P is Ni / (Si+P) = 3.81.

[0140] The preparation steps are as follows:

[0141] 1) Ingredients: Prepare ingredients according to the required composition.

[0142] 2) Smelting: Semi-continuous casting is adopted. During the smelting process, 20-30cm thick charcoal is used to cover the furnace. Electrolytic copper, nickel ingots, tin ingots, and copper-silicon intermediate alloy are melted in sequence. Then, S powder and phosphorus copper alloy are wrapped in copper sheet and added to the furnace. The smelting temperature is 1180℃ to obtain ingots.

[0143] 3) Hot extrusion: The ingot is heated to 750℃ and extruded in a horizontal extrusion press to obtain a wire rod, with the extrusion speed controlled at 4mm / s.

[0144] 4) Pickling: The extruded wire blank is placed in a solution of water, nitric acid and sulfuric acid for pickling to obtain a wire blank without an oxide layer.

[0145] 5) Single cold working: The pickled wire blank is drawn or cold rolled, with a processing rate of 55%.

[0146] 6) Solution treatment: The cold-worked wire blank is solution treated online, and the temperature of the wire blank is controlled at 760℃.

[0147] 7) Secondary cold working: The solution-treated wire blank is subjected to cold deformation at a processing rate of 40%.

[0148] 8) Aging: The wire blank after the second cold working is subjected to aging treatment at a temperature of 450℃ for 5 hours.

[0149] 9) Finished product processing: The aged wire blanks are drawn into finished products, with a processing rate of 11%.

[0150] The electrical conductivity, tensile strength, and machinability of the copper alloys prepared in Examples 1-3 and Comparative Examples 1-4 were tested, and the results are recorded in Table 3. The test methods are as follows:

[0151] Conductivity: Tested according to GB / T 32791-2016 "Eddy Current Test Method for Conductivity of Copper and Copper Alloys";

[0152] Tensile strength: Tested in accordance with GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature";

[0153] Relative cutting index: The cutting force is calculated based on the cutting force of the cutting force tester and compared with that of leaded brass C36000. Then, the relative cutting index is obtained according to the formula: Relative cutting index = Cutting force of copper alloy / Cutting force of C36000 × 100%.

[0154] Table 2. Performance comparison of materials in each embodiment and comparative example.

[0155] serial number Conductivity / % IACS Tensile strength / MPa Relative cutting index Example 1 53 553 62％ Example 2 49 565 68％ Example 3 45 590 70％ Comparative Example 1 56 520 20％ Comparative Example 2 50 535 63％ Comparative Example 3 46 585 25％ Comparative Example 4 54 550 30％

[0156] Based on the test results, the following conclusions can be drawn: the copper alloy wires prepared in each embodiment have a conductivity of 45%–53%, a tensile strength of 553–590 MPa, and a relative cutting index of 62%–70%, exhibiting high strength, high conductivity, and easy machinability. Comparing Example 1 with Comparative Example 1, the addition of Si and Sn elements significantly improves the material strength with a relatively small decrease in conductivity, while the addition of S element greatly improves the material's machinability. Comparing Example 2 with Comparative Example 2, the addition of Si and Sn elements significantly improves the material strength with a relatively small decrease in conductivity. Comparing Example 3 with Comparative Example 3, the addition of S element alone has no significant effect on the material's conductivity and tensile strength, but can significantly improve machinability. Comparing Example 1 with Comparative Example 4, Comparative Example 4 uses S powder for addition, and most of the S oxidizes during the smelting process, resulting in a reduced number of Cu2S particles in the final product, leading to decreased machinability.

[0157] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A copper alloy, characterized in that, The copper alloy has the following mass percentage composition: Ni: 0.5-2.0 wt%, S: 0.3-0.8 wt%, P: 0.1-0.3 wt%, Sn: 0.1-0.2 wt%, Si: 0.05-0.2 wt%, with the balance being Cu and unavoidable impurities. The ratio of the mass of Ni to the sum of the masses of Si and P is Ni / (Si+P) = 3-4. The microstructure of the copper alloy consists of Cu2S particles, Ni3P particles, Ni5P2 particles, and Ni2Si particles. The copper alloy is prepared by the following method: S1. Mechanical alloying: Cu powder and S powder are mixed in a molar ratio of 2:1 and ball-milled to obtain Cu2S powder; S2. Ingredients: Prepare ingredients according to the required composition; S3. Smelting: Electrolytic copper, nickel ingots, tin ingots and copper-silicon master alloy are melted in sequence. Then, Cu2S powder and phosphorus copper alloy are wrapped in copper sheet and added to the furnace to smelt and obtain ingots. S4. Hot extrusion: heating the ingot and then extruding it to obtain a wire rod. S5. Pickling: The wire rod is pickled to remove the oxide layer; S6. Cold working in one step: The wire blank is cold deformed; S7. Solution treatment: The wire blank after one cold working is subjected to online solution treatment; S8. Secondary cold working: The solution-treated wire blank is cold-deformed again; S9. Aging: The wire blank after secondary cold working is subjected to aging treatment; S10. Finished product processing: The aging-treated wire blank is drawn into a finished product.

2. The copper alloy according to claim 1, characterized in that, The copper alloy has a strength ≥550MPa, a conductivity ≥45%, and a relative cutting index ≥60% compared to C36000. The relative cutting index = cutting force of copper alloy / cutting force of C36000 × 100%.

3. A method for preparing a copper alloy as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Mechanical alloying: Cu powder and S powder are mixed in a molar ratio of 2:1 and ball-milled to obtain Cu2S powder; S2. Ingredients: Prepare ingredients according to the required composition; S3. Smelting: Electrolytic copper, nickel ingots, tin ingots and copper-silicon master alloy are melted in sequence. Then, Cu2S powder and phosphorus copper alloy are wrapped in copper sheet and added to the furnace to smelt and obtain ingots. S4. Hot extrusion: heating the ingot and then extruding it to obtain a wire rod. S5. Pickling: The wire rod is pickled to remove the oxide layer; S6. Cold working in one step: The wire blank is cold deformed; S7. Solution treatment: The wire blank after one cold working is subjected to online solution treatment; S8. Secondary cold working: The solution-treated wire blank is cold-deformed again; S9. Aging: The wire blank after secondary cold working is subjected to aging treatment; S10. Finished product processing: The aging-treated wire blank is drawn into a finished product.

4. The method for preparing the copper alloy according to claim 3, characterized in that, Step S1 specifically includes: placing the mixture of Cu powder and S powder in a ball mill jar, with a mass ratio of steel balls to mixed powder of 10~30:1, evacuating the ball mill jar and filling it with argon gas, and ball milling in one direction at a speed of 400~500 r / min for 2~6 hours.

5. The method for preparing the copper alloy according to claim 3, characterized in that, Step S4 specifically includes: heating the ingot to 700~850℃, extruding it in a horizontal extrusion press to obtain a wire rod, and controlling the extrusion speed at 2~5mm / s.

6. The method for preparing the copper alloy according to claim 3, characterized in that, The processing rate of the first cold processing in step S6 is 50%~70%, the processing rate of the second cold processing in step S8 is 30%~60%, and the processing rate of the finished product processing in step S10 is 10%~20%.

7. The method for preparing the copper alloy according to claim 3, characterized in that, In step S3, the melting temperature is 1150-1250℃, and in step S7, the solution treatment temperature is 750-800℃.

8. The method for preparing the copper alloy according to claim 3, characterized in that, In step S9, the aging temperature is 420~470℃ and the heat preservation time is 1~5 hours.