Copper-silver alloy and preparation method thereof

Abstract

The present application discloses a copper-silver alloy and a preparation method thereof, which comprises the following steps: silver alloying: adding a silver raw material and a rare earth element into a vacuum induction furnace for mixing, heating and melting in a vacuum atmosphere to obtain a silver alloy melt; copper alloying: adding electrolytic copper into a non-vacuum induction furnace for smelting, heating and melting, and then adding phosphorus and rare earth elements for alloying to obtain a copper alloy melt; horizontal continuous casting: horizontally continuous casting the above-mentioned silver alloy melt and copper alloy melt respectively to obtain silver and copper alloy plates; hot extrusion molding: alternately stacking multiple layers of silver alloy plates and copper alloy plates in a "silver-copper-silver-..." manner, placing them in a hot extrusion device for hot extrusion to form a composite plate; cold drawing: cold drawing the composite plate into a material to obtain a copper-silver alloy, which can be used as an electrical contact material. The preparation method is low in cost, and the obtained copper-silver alloy has high conductivity, high hardness and resistance to arc erosion.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy material preparation, and in particular relates to a copper-silver alloy and a preparation method thereof. Background Art

[0002] Electrical contact materials are extremely critical components in electrical equipment, and their performance plays a decisive role in the reliability and service life of the equipment. In the field of electrical contact, silver-copper alloys are widely used due to their good electrical and thermal conductivity. However, the silver content in traditional silver-copper alloys is usually 75%-95%, and the cost of raw materials is relatively high. In addition, its resistance to welding and arc erosion is poor, which can easily cause the circuit to fail to switch normally under conditions such as frequent switching and high current density, affecting the operation of the equipment. To solve these problems, many attempts have been made in related technical fields, such as adding alloying elements to improve performance, but traditional processes make it difficult to achieve a uniform distribution of alloying elements in silver-copper alloys, resulting in poor overall performance improvement. Therefore, it is urgent to develop a preparation method that can significantly improve the anti-welding performance of silver-copper alloys while effectively reducing costs. Summary of the Invention

[0003] The purpose of the present invention is to solve at least one problem in the prior art and to provide a copper-silver alloy and a preparation method thereof.

[0004] To achieve the above object, the present invention proposes a method for preparing a copper-silver alloy, comprising the following steps:

[0005] Silver alloying: silver raw materials and rare earth elements are added into a vacuum induction furnace and mixed. The temperature is raised to 1100-1200°C under vacuum atmosphere and melted to obtain a silver alloy melt.

[0006] Copper alloying: electrolytic copper is added to a non-vacuum induction furnace for smelting. After heating to 1200-1300°C and melting, phosphorus and rare earth elements are added for alloying to obtain a copper alloy melt.

[0007] Horizontal continuous casting: horizontally continuously casting the silver alloy melt and the copper alloy melt to obtain silver alloy plates and copper alloy plates respectively;

[0008] Hot extrusion molding: Multiple layers of silver alloy sheets and copper alloy sheets are alternately stacked in the order of "silver-copper-silver-..." and placed in a hot extrusion device for hot extrusion to form a composite sheet with a dense composite structure;

[0009] Cold drawing: The composite sheet is cold drawn to obtain copper-silver alloy.

[0010] As an optional embodiment, in order to further improve the purity and performance of the copper-silver alloy, the silver raw material in the silver alloying step can be selected as 1# silver raw material with a purity ≥99.9%, and the purity of the electrolytic copper in the copper alloying step can be ≥99.9%.

[0011] As an optional embodiment, in the silver alloying step, the amount of rare earth element added is 0.01%-0.05% of the mass of the silver raw material, and the rare earth element is cerium, lanthanum or a mixed rare earth thereof.

[0012] As an optional embodiment, in the silver alloying step, the vacuum degree of the vacuum induction furnace during the melting process does not exceed 10 -3 Pa, after the silver raw material and rare earth elements are melted to form a melt, the electromagnetic stirring device is turned on and stirred thoroughly for 15-25 minutes. The vacuum setting ensures that oxidation is not easily generated during the melting process, and the electromagnetic stirring can better improve the uniformity of element dispersion.

[0013] As an optional embodiment, in the copper alloying step, phosphorus is added in the form of a Cu-P master alloy, the amount of phosphorus added is 0.5%-5% of the mass of the electrolytic copper, and the amount of rare earth elements added is 0.02%-0.08% of the mass of the electrolytic copper, and the rare earth elements are cerium, lanthanum or mixed rare earths thereof.

[0014] As an optional embodiment, during the copper alloying step, the molten pool is purified by covering the slag when smelting electrolytic copper, and the melt is subjected to dual-frequency electromagnetic stirring after adding phosphorus and rare earth elements. The frequency of the dual-frequency electromagnetic stirring can be set as required, including but not limited to 50Hz+200Hz, 60Hz+200Hz, and 60Hz+220Hz, to further improve the uniformity of alloy element dispersion.

[0015] As an optional embodiment, during the horizontal continuous casting step, the casting speed is controlled to be 1 cm / s-10 cm / s, the cooling water temperature is 20°C-30°C, and the continuous casting process is carried out under protective gas conditions. During the continuous casting process, the silver alloy melt and the copper alloy melt are subjected to online electromagnetic stirring to refine the grains. The protective gas includes, but is not limited to, argon or nitrogen.

[0016] As an optional implementation, the thickness of the silver alloy plate and the copper alloy plate is 50 mm-200 mm.

[0017] As an optional embodiment, in the hot extrusion forming step, the hot extrusion temperature is controlled at 600-800°C, the pressure is 100-300 MPa, the extrusion ratio is 20:1-50:1, and the number of stacked layers of silver alloy sheet material and copper alloy sheet material is 5-20. The number of stacked layers of silver alloy sheet material and copper alloy sheet material can be set based on user performance requirements and can be set to 5, 7, 8, 10, 15, or 20 layers.

[0018] As an optional implementation, the contact surfaces of the silver alloy plate and the copper alloy plate are polished to a roughness Ra≤1.6 μm before hot extrusion.

[0019] As an optional embodiment, in the cold drawing step, the composite sheet is subjected to multiple cold drawing passes, and the deformation of a single pass is controlled at 5%-15%. When the deformation is large, annealing is performed to relieve stress.

[0020] The present invention also provides a copper-silver alloy prepared according to the above-mentioned copper-silver alloy preparation method, and the copper-silver alloy is used as an electrical contact material.

[0021] Beneficial effects of the present invention:

[0022] 1. The preparation method of the present invention combines a silver and copper alloy alternating layer structure design with a composite molding process. Silver alloy sheets and copper alloy sheets are alternately stacked and hot extruded to form a layered structure perpendicular to the contact surface. This structure gives the copper-silver alloy material a high electrical conductivity close to that of pure silver. When used as an electrical contact material, the copper-silver alloy can effectively disperse local heat during high current shocks, inhibit contact welding and material transfer, and increase the number of anti-welding times by 2-3 times (≥2000 times) compared to traditional silver-copper alloys. This significantly extends the service life of the electrical contact material and solves the problem of existing single alloys being prone to failure under high-load conditions.

[0023] 2. The hot extrusion molding step of the preparation method of the present invention adopts a "silver-copper-silver-..." alternating structure and uses copper alloy plates as a supporting layer, which greatly reduces the amount of silver used. Copper alloy plates are lower in cost than silver alloy plates. When silver-copper alloy is used as an electrical contact material, the cost can be greatly reduced compared to traditional silver contacts, significantly improving the economic efficiency of industrial production.

[0024] 3. In the copper alloying step of the preparation method of the present invention, the cost of melting electrolytic copper in a non-vacuum induction furnace is reduced by 40% compared with the traditional vacuum melting process. The addition of phosphorus can improve the oxidation resistance of the copper layer, and the addition of rare earth elements can refine the grains, thereby avoiding the need for a complex vacuum environment while ensuring the strength of the copper layer.

[0025] 4. The preparation method of the present invention optimizes microstructural properties through rare earth alloying and multi-process synergistic optimization: the rare earth elements in the silver-copper alloy can purify the molten pool and are evenly distributed at the grain boundaries as nano-scale compounds to refine the grains, enhance the grain boundary bonding strength and high-temperature resistance; the horizontal continuous casting process uses online electromagnetic stirring to reduce component segregation, and hot extrusion can form a 1-3μm interface diffusion layer on the contact surface of the silver and copper alloy plates, achieving a strong metallurgical bond between the layers.

[0026] 5. The silver-copper alloy prepared by the preparation method of the present invention has an electrical conductivity of ≥98% IACS and a hardness of ≥120 HV. It has high conductivity, high hardness and resistance to arc erosion. Its comprehensive performance is better than that of traditional single silver and copper alloys, meeting the needs of high-end electrical contact materials.

[0027] The features and advantages of the present invention will be described in detail through embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the structure of the silver-copper alloy electrical contact material according to an embodiment of the present invention.

[0029] In the figure: 1. electrical contact material; 11. silver alloy plate; 12. copper alloy plate; 13. electrical contact head. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0031] Example 1

[0032] This embodiment provides a method for preparing a copper-silver alloy, comprising the following steps:

[0033] Silver alloying: take 99.99% pure No. 1 silver ingot and put it into vacuum induction furnace, add Ce-La mixed rare earth (Ce:La=3:1) according to the mass ratio of silver ingot 0.03% and put it into vacuum induction furnace, and keep the vacuum degree ≤10 -3 After heating to 1150 °C under Pa conditions and melting, electromagnetic stirring (speed 150 r / min) was turned on and stirred for 15 min to form a uniform silver alloy melt;

[0034] Copper alloying: Electrolytic copper with a purity of 99.95% was added to a non-vacuum induction furnace for smelting. A Cu-P master alloy (P content of 15%) was added at a mass ratio of 1.5% of the electrolytic copper, and a Ce-La composite rare earth (Ce:La=3:1) was added at a mass ratio of 0.05% of the electrolytic copper. The copper was placed in a non-vacuum induction furnace, covered with slag, and heated to 1250°C for melting. Dual-frequency electromagnetic stirring (dual frequency of 50Hz+200Hz) was started and stirred for 20 minutes to obtain a copper alloy melt.

[0035] Horizontal continuous casting: The silver alloy melt is continuously cast at a casting speed of 5 cm / s, a cooling water temperature of 25°C, and online electromagnetic stirring (frequency of 80 Hz) under argon protection to form a 100 mm thick silver alloy plate; the copper alloy melt is continuously cast at a casting speed of 8 cm / s, a cooling water temperature of 25°C, and online electromagnetic stirring (frequency of 80 Hz) to form a 100 mm thick copper alloy plate;

[0036] Hot extrusion molding: The contact surfaces of five layers of silver alloy sheets and five layers of copper alloy sheets were polished to a roughness of Ra ≤ 1.6 μm. They were then stacked alternately in a "silver-copper-silver-..." pattern and placed in a hot extrusion machine. Hot extrusion was performed at a temperature of 700°C, a pressure of 200 MPa, and an extrusion ratio of 20:1 to form a 50 mm thick composite sheet with a dense composite structure (the thickness of each silver and copper alloy sheet layer was initially compressed to 5 mm / layer).

[0037] Cold drawing: The composite sheet is cold drawn to control the final deformation to 20% (the thickness of each silver and copper alloy sheet layer is 4 mm / layer), and a copper-silver alloy with a thickness of 40 mm is obtained.

[0038] Among them, the grain size of the silver alloy plate is 6μm, and the grain size of the copper alloy plate is 7μm.

[0039] Example 2

[0040] This embodiment provides a method for preparing a copper-silver alloy, comprising the following steps:

[0041] Silver alloying: take 99.99% pure 1# silver ingot and put it into vacuum induction furnace, add La rare earth according to the mass ratio of silver ingot to 0.02% and put it into vacuum induction furnace, and keep the vacuum degree ≤10 -3 After heating to 1180 °C under Pa conditions and melting, electromagnetic stirring (speed 120 r / min) was turned on and stirred for 15 min to form a uniform silver alloy melt;

[0042] Copper alloying: Electrolytic copper with a purity of 99.95% was added to a non-vacuum induction furnace for smelting. A Cu-P master alloy (P content of 12%) was added at a mass ratio of 0.8% of the electrolytic copper, and Ce rare earth was added at a mass ratio of 0.04% of the electrolytic copper. The copper was placed in a non-vacuum induction furnace, covered with slag, and heated to 1250°C for melting. Dual-frequency electromagnetic stirring (dual frequency of 50 Hz + 200 Hz) was started and stirred for 20 minutes to obtain a copper alloy melt.

[0043] Horizontal continuous casting: The silver alloy melt was continuously cast at a casting speed of 3 cm / s, a cooling water temperature of 22°C, online electromagnetic stirring (frequency of 70 Hz), and argon protection to form an 80 mm thick silver alloy plate; the copper alloy melt was continuously cast at a casting speed of 6 cm / s, a cooling water temperature of 28°C, and online electromagnetic stirring (frequency of 70 Hz) to form an 80 mm thick copper alloy plate;

[0044] Hot extrusion molding: The contact surfaces of three layers of silver alloy sheet and three layers of copper alloy sheet were polished to a roughness of Ra ≤ 1.6μm. They were then stacked alternately in a "silver-copper-silver-..." pattern and placed in a hot extrusion machine. Hot extrusion was performed at a temperature of 650°C, a pressure of 150MPa, and an extrusion ratio of 30:1 to form a composite sheet with a dense composite structure of 16mm in thickness (the thickness of each silver and copper alloy sheet layer was initially compressed to 2.67mm / layer);

[0045] Cold drawing: The composite sheet is cold drawn to control the final deformation to 10% (the thickness of each silver and copper alloy sheet layer is 2.4 mm / layer), and a copper-silver alloy with a thickness of 14.4 mm is obtained.

[0046] Among them, the grain size of the silver alloy plate is 5μm, and the grain size of the copper alloy plate is 8μm.

[0047] Example 3

[0048] This embodiment provides a method for preparing a copper-silver alloy, comprising the following steps:

[0049] Silver alloying: take 99.99% pure 1# silver ingot and put it into vacuum induction furnace, add Ce rare earth according to the mass ratio of silver ingot to 0.01% and put it into vacuum induction furnace, and keep the vacuum degree ≤10 -3 After heating to 1130 °C under Pa conditions and melting, electromagnetic stirring (speed 100 r / min) was turned on and stirred for 20 min to form a uniform silver alloy melt;

[0050] Copper alloying: electrolytic copper with a purity of 99.95% is added to a non-vacuum induction furnace for smelting. Cu-P master alloy (P content 20%) is added at a mass ratio of 0.5% of the electrolytic copper, and La rare earth is added at a mass ratio of 0.02% of the electrolytic copper. The copper is placed in a non-vacuum induction furnace, covered with slag, and heated to 1200°C for melting. Dual-frequency electromagnetic stirring (dual frequency of 60Hz+220Hz) is turned on and stirred for min to obtain a copper alloy melt.

[0051] Horizontal continuous casting: The silver alloy melt is continuously cast at a casting speed of 1 cm / s, a cooling water temperature of 20°C, online electromagnetic stirring (frequency 50 Hz), and argon protection to form a 50 mm thick silver alloy plate; the copper alloy melt is continuously cast at a casting speed of 3 cm / s, a cooling water temperature of 30°C, and online electromagnetic stirring (frequency 60 Hz) to form a 50 mm thick copper alloy plate;

[0052] Hot extrusion molding: The contact surfaces of four layers of silver alloy sheets and four layers of copper alloy sheets were polished to a roughness of Ra ≤ 1.6 μm. They were then stacked alternately in a "silver-copper-silver-..." pattern and placed in a hot extrusion machine. Hot extrusion was performed at a temperature of 680°C, a pressure of 180 MPa, and an extrusion ratio of 20:1 to form a composite sheet with a dense composite structure of 20 mm in thickness (the thickness of each silver and copper alloy sheet layer was initially compressed to 2.5 mm / layer);

[0053] Cold drawing: The composite sheet is cold drawn to control the final deformation to 20% (the thickness of each silver and copper alloy sheet layer is 2 mm / layer), and a copper-silver alloy with a thickness of 16 mm is obtained.

[0054] Among them, the grain size of the silver alloy plate is 5.6μm, and the grain size of the copper alloy plate is 7.2μm.

[0055] The present invention also provides a silver-copper alloy prepared according to the above-mentioned method for preparing the copper-silver alloy, which can be used as an electrical contact material. Figure 1 The present electrical contact material 1 comprises three layers of silver alloy sheet material 11 and two layers of copper alloy sheet material 12. The contact surface between the silver alloy sheet material 11 and the copper alloy sheet material 12 forms a transition layer. The lower portion of the electrical contact material 1, indicated by the dashed box in the figure, represents its working surface, serving as the electrical contact 13. The copper layer accounts for 40%-50% of the five-layer structure, saving 30%-50% of silver compared to conventional single-silver alloy structures.

[0056] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention falls within the protection scope of the present invention.

Claims

1. A method for preparing a copper-silver alloy, characterized in that: The following steps are involved: Silver alloying: silver raw materials and rare earth elements are added into a vacuum induction furnace and mixed. The temperature is raised to 1100-1200°C under vacuum atmosphere and melted to obtain a silver alloy melt. Copper alloying: electrolytic copper is added to a non-vacuum induction furnace for smelting. After heating to 1200-1300°C for melting, phosphorus and rare earth elements are added for alloying to obtain a copper alloy melt. The phosphorus addition amount is 0.5%-5% of the mass of the electrolytic copper, and the rare earth element addition amount is 0.02%-0.08% of the mass of the electrolytic copper. Horizontal continuous casting: horizontally continuously casting the silver alloy melt and the copper alloy melt to obtain silver alloy plates and copper alloy plates, respectively. During the horizontal continuous casting process, the silver alloy melt and the copper alloy melt are subjected to online electromagnetic stirring to refine the grains; Hot extrusion molding: Multiple layers of the aforementioned silver alloy sheet and copper alloy sheet are alternately stacked in a "silver-copper-silver-..." pattern, and placed in a hot extrusion device for hot extrusion at a temperature of 600°C-800°C, a pressure of 100MPa-300MPa, and an extrusion ratio of 20:1-50:1 to form a composite sheet with a dense composite structure; Cold drawing: The composite sheet is cold drawn to obtain copper-silver alloy.

2. The method for preparing a copper-silver alloy according to claim 1, wherein: In the silver alloying step, the amount of rare earth element added is 0.01%-0.05% of the mass of the silver raw material, and the rare earth element is cerium, lanthanum or a mixed rare earth thereof.

3. The method for preparing the copper-silver alloy according to claim 1, wherein: In the silver alloying step, the vacuum degree of the vacuum induction furnace during the melting process does not exceed 10 -3 Pa, after the silver raw material and the rare earth element are melted to produce a melt, the electromagnetic stirring device is turned on and stirred thoroughly for 15min-25min.

4. The method for preparing a copper-silver alloy according to claim 1, wherein: In the copper alloying step, phosphorus is added in the form of a Cu-P master alloy, and the rare earth element is cerium, lanthanum or a mixed rare earth thereof.

5. The method for preparing the copper-silver alloy according to claim 1, wherein: In the copper alloying step, when smelting electrolytic copper, the molten pool is purified by covering with slag, and after adding phosphorus and rare earth elements, the melt is subjected to dual-frequency electromagnetic stirring.

6. The method for preparing a copper-silver alloy according to claim 1, wherein: In the horizontal continuous casting step, the casting speed is controlled to be 1 cm / s-10 cm / s, the cooling water temperature is 20° C.-30° C., and the continuous casting process is carried out under protective gas protection conditions.

7. The method for preparing a copper-silver alloy according to claim 1, wherein: The thickness of the silver alloy plate and the copper alloy plate is 50mm-200mm.

8. The method for preparing a copper-silver alloy according to claim 1, wherein: In the hot extrusion forming step, the number of stacked layers of the silver alloy plate and the copper alloy plate is 5-20.

9. The method for preparing a copper-silver alloy according to claim 1, wherein: The contact surfaces of the silver alloy plate and the copper alloy plate are polished to a roughness Ra≤1.6 μm before hot extrusion.

10. The method for preparing a copper-silver alloy according to claim 1, wherein: In the cold drawing step, the composite sheet is subjected to multiple cold drawing passes, and the deformation of a single pass is controlled within 5%-15%. When the deformation is large, annealing is performed to relieve stress.

11. A copper-silver alloy prepared according to the method for preparing a copper-silver alloy according to any one of claims 1 to 10, characterized in that: The copper-silver alloy is used as an electrical contact material.

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