Copper-silver alloy and preparation method thereof

Abstract

The invention discloses a copper-silver alloy and a preparation method thereof.The preparation method comprises the following steps that silver alloying is conducted, specifically, a silver raw material and rare earth elements are added into a vacuum induction furnace to be mixed, and a silver alloy melt is obtained after heating and melting are conducted in the vacuum atmosphere; copper alloying is conducted, specifically, electrolytic copper is added into a non-vacuum induction furnace to be smelted, phosphorus and rare earth elements are added for alloying after heating melting, and a copper alloy melt is obtained; horizontal continuous casting: respectively carrying out horizontal continuous casting on the silver alloy melt and the copper alloy melt to obtain a silver alloy plate and a copper alloy plate; the multiple layers of silver alloy plates and the multiple layers of copper alloy plates are alternately stacked in a silver-copper-silver-... mode and placed in hot extrusion equipment to be subjected to hot extrusion, and a composite plate is formed; and cold drawing is conducted, specifically, the composite board is subjected to cold drawing to obtain the copper-silver alloy, the copper-silver alloy can be used as an electric contact material, the preparation method is low in cost, and the prepared copper-silver alloy has high conductivity, high hardness and arc erosion resistance.

Description

Technical Field

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

[0002] As an extremely critical component in electrical equipment, the performance of the electrical contact material plays a decisive role in the reliability and service life of the equipment. In the field of electrical contacts, silver-copper alloys are widely used due to their good electrical conductivity and thermal conductivity. However, in traditional silver-copper alloys, the silver content is usually 75%-95%, resulting in a relatively high raw material cost. In addition, their anti-welding and anti-arc erosion performances are poor, and under working conditions such as frequent switching and high current density, it is easy to cause abnormal on-off of the circuit, affecting the operation of the equipment. To solve these problems, many attempts have been made in the relevant technical fields, such as adding alloying elements to improve the performance, but it is difficult to achieve uniform distribution of alloying elements in silver-copper alloys by traditional processes, resulting in poor improvement of comprehensive performance. 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 purpose, the present invention provides a preparation method of a copper-silver alloy, including the following steps: Silver alloying: adding silver raw materials and rare earth elements into a vacuum induction furnace for mixing, and heating to 1100℃-1200℃ in a vacuum atmosphere for melting to obtain a silver alloy melt; Copper alloying: adding electrolytic copper into a non-vacuum induction furnace for smelting, heating to 1200℃-1300℃ for melting, and then adding phosphorus elements and rare earth elements for alloying to obtain a copper alloy melt; Horizontal continuous casting: performing horizontal continuous casting on the above silver alloy melt and copper alloy melt respectively to obtain silver alloy plates and copper alloy plates; Hot extrusion forming: alternately stacking multiple layers of silver alloy plates and copper alloy plates in the order of "silver-copper-silver-...", and placing them in a hot extrusion device for hot extrusion to form a composite plate with a dense composite structure; Cold drawing: performing cold drawing on the composite plate to form a finished product, and obtaining a copper-silver alloy.

[0005] As an optional implementation manner, 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 the No. 1 silver raw material with a purity ≥99.9%, and the purity of the electrolytic copper in the copper alloying step ≥99.9%.

[0006] As an optional implementation, 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.

[0007] 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 produce a melt, the electromagnetic stirring device is turned on and stirred for 15min-25min. The vacuum setting can ensure that oxidation is not easy to occur during the smelting process, and the electromagnetic stirring can better improve the uniformity of element dispersion.

[0008] As an optional embodiment, in the copper alloying step, phosphorus is added in the form of Cu-P master alloy, the amount of phosphorus added is 0.5%-5% of the mass of the electrolytic copper, 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.

[0009] As an optional embodiment, in the copper alloying step, when smelting electrolytic copper, the molten pool is purified by covering slag, 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 according to demand, including but not limited to 50Hz+200Hz, 60Hz+200Hz, 60Hz+220Hz, so as to further improve the uniformity of alloy element dispersion.

[0010] As an optional embodiment, 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, the continuous casting process is carried out under the protection of protective gas, and the silver alloy melt and the copper alloy melt are subjected to online electromagnetic stirring to refine the grains during the continuous casting process. The protective gas includes but is not limited to argon or nitrogen.

[0011] As an optional implementation, the thickness of the silver alloy plate and the copper alloy plate is 50 mm-200 mm.

[0012] As an optional embodiment, in the hot extrusion forming step, the hot extrusion temperature is controlled at 600-800°C, the pressure is 100-300MPa, the extrusion ratio is 20:1-50:1, and the number of superimposed layers of the silver alloy sheet and the copper alloy sheet is 5-20. The number of superimposed layers of the silver alloy sheet and the copper alloy sheet can be set according to the user's performance requirements, and can be set to 5 layers, 7 layers, 8 layers, 10 layers, 15 layers, or 20 layers.

[0013] As an optional implementation, the contact surfaces of the silver alloy sheet and the copper alloy sheet are polished to a roughness Ra≤1.6 μm before hot extrusion.

[0014] As an alternative embodiment, in the cold drawing step, the composite sheet is cold drawn in multiple passes, and the deformation amount per pass is controlled within 5%-15%. When the deformation amount is large, stress relief is carried out by annealing.

[0015] The present invention also provides a copper-silver alloy prepared by the preparation method of the above copper-silver alloy, and the copper-silver alloy is used as an electrical contact material.

[0016] Beneficial effects of the present invention: 1. In the preparation method of the present invention, by combining the design of the alternating laminated structure of silver and copper alloys with the composite forming process, the silver alloy sheet and the copper alloy sheet are alternately stacked and hot extruded to form a layered structure perpendicular to the contact surface of the contact. This structure enables the copper-silver alloy material to have a high electrical conductivity close to that of pure silver. When the copper-silver alloy is used as an electrical contact material, it can effectively disperse the local heat during high-current impact, inhibit contact welding and material transfer, and increase the number of anti-welding times by 2-3 times (≥2000 times) compared with the traditional silver-copper alloy, significantly extending the service life of the electrical contact head material and solving the problem that the existing single alloy is prone to failure under high-load working conditions.

[0017] 2. In the hot extrusion forming step of the preparation method of the present invention, an "Ag-Cu-Ag-..." alternating structure is adopted, and the copper alloy sheet is used as the support layer, greatly reducing the usage amount of silver. The cost of the copper alloy sheet is lower than that of the silver alloy sheet. When the copper-silver alloy is used as the electrical contact head material, the cost can be greatly reduced compared with the traditional silver contact, significantly improving the economic efficiency of industrial production.

[0018] 3. In the copper alloying step of the preparation method of the present invention, the cost is reduced by 40% by using a non-vacuum induction furnace to melt electrolytic copper compared with the traditional vacuum melting process. Adding phosphorus elements can improve the oxidation resistance of the copper layer, and adding rare earth elements can refine the grains, avoiding the need for a complex vacuum environment while ensuring the strength of the copper layer.

[0019] 4. The preparation method of the present invention optimizes the microstructure properties through rare earth alloying and multi-process coordination: rare earth elements in the copper-silver alloy can purify the molten pool and are uniformly distributed at the grain boundaries in the form of nano-scale compounds to refine the grains, enhancing the grain boundary bonding force and high-temperature resistance; online electromagnetic stirring is adopted during the horizontal continuous casting process to reduce composition segregation, and hot extrusion can form an interface diffusion layer with a thickness of 1-3 μm on the contact surface of the silver and copper alloy sheets, realizing a firm metallurgical bond between layers.

[0020] 5. The copper-silver alloy prepared by the preparation method of the present invention has an electrical conductivity ≥98% IACS and a hardness ≥120 HV, and has high electrical conductivity, high hardness and arc erosion resistance. Its comprehensive performance is superior to that of traditional single silver and copper alloys, meeting the requirements of high-end electrical contact materials.

[0021] The features and advantages of the present invention will be described in detail through examples in conjunction with the drawings. Brief Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the silver-copper alloy electrical contact material according to an embodiment of the present invention.

[0023] In the figure: 1. Electrical contact material; 11. Silver alloy sheet; 12. Copper alloy sheet; 13. Electrical contact head. Detailed Embodiments

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application.

[0025] Embodiment 1 This embodiment provides a preparation method for a copper-silver alloy, including the following steps: Silver alloying: Take a 1# silver ingot with a purity of 99.99% and add it to a vacuum induction furnace. Add a Ce-La mixed rare earth (Ce:La = 3:1) according to 0.03% of the mass ratio of the silver ingot to the vacuum induction furnace. Under the condition that the vacuum degree is ≤ 10 -3 Pa, heat it up to 1150 °C and melt it. Then, start electromagnetic stirring (rotation speed 150 r / min) and stir for 15 min to form a uniform silver alloy melt; Copper alloying: Add electrolytic copper with a purity of 99.95% to a non-vacuum induction furnace for smelting. Add a Cu-P master alloy (P content 15%) according to 1.5% of the mass ratio of the electrolytic copper and a Ce-La composite rare earth (Ce:La = 3:1) according to 0.05% of the mass ratio of the electrolytic copper. Place it in the non-vacuum induction furnace, cover the slag, and then heat it up to 1250 °C and melt it. Start dual-frequency electromagnetic stirring (dual frequencies are 50 Hz + 200 Hz) and stir for 20 min to obtain a copper alloy melt; Horizontal continuous casting: Continuously cast the above silver alloy melt. During the continuous casting process, continuously cast at a drawing speed of 5 cm / s, the cooling water temperature is 25 °C, and online electromagnetic stirring (frequency 80 Hz). Cast it into a 100-mm-thick silver alloy sheet under argon protection; Continuously cast the above copper alloy melt. During the continuous casting process, continuously cast at a drawing speed of 8 cm / s, the cooling water temperature is 25 °C, and online electromagnetic stirring (frequency 80 Hz). Cast it into a 100-mm-thick copper alloy sheet; Hot extrusion forming: Polish the contact surfaces of 5 layers of silver alloy sheets and 5 layers of copper alloy sheets to a roughness Ra ≤ 1.6 μm, stack them alternately in the order of "silver - copper - silver -...", place them in a hot extrusion equipment, and conduct hot extrusion at a temperature of 700 °C, a pressure of 200 MPa, and an extrusion ratio of 20:1 to form a composite sheet with a thickness of 50 mm and a dense composite structure (the thickness of each layer of silver and copper alloy sheets is initially compressed to 5 mm / layer); Cold drawing: Cold draw the composite sheet into a finished product, control the final deformation amount to be 20% (the thickness of each layer of silver and copper alloy sheets is 4 mm / layer), and obtain a copper - silver alloy with a thickness of 40 mm.

[0026] Among them, the grain size of the silver alloy sheet is 6 μm, and the grain size of the copper alloy sheet is 7 μm.

[0027] Example 2 This example provides a method for preparing a copper - silver alloy, including the following steps: Silver alloying: Take a 1# silver ingot with a purity of 99.99% and add it to a vacuum induction furnace. Add La rare earth to the vacuum induction furnace according to the mass ratio of the silver ingot of 0.02%, and heat it up to 1180 °C for melting under the condition of a vacuum degree ≤ 10 -3 Pa. After melting, start electromagnetic stirring (rotation speed 120 r / min), and stir for 15 min to form a uniform silver alloy melt; Copper alloying: Add electrolytic copper with a purity of 99.95% to a non - vacuum induction furnace for smelting. Add Cu - P master alloy (P content 12%) according to the mass ratio of electrolytic copper of 0.8% and add Ce rare earth according to the mass ratio of electrolytic copper of 0.04%. Place it in a non - vacuum induction furnace, cover the slag, and heat it up to 1250 °C for melting. Start dual - frequency electromagnetic stirring (dual frequencies are 50 Hz + 200 Hz), and stir for 20 min to obtain a copper alloy melt; Horizontal continuous casting: Conduct continuous casting on the above - mentioned silver alloy melt. During the continuous casting process, conduct continuous casting at a drawing speed of 3 cm / s, the cooling water temperature is 22 °C, with on - line electromagnetic stirring (frequency 70 Hz), and cast it into a silver alloy sheet with a thickness of 80 mm under argon protection; Conduct continuous casting on the above - mentioned copper alloy melt. During the continuous casting process, conduct continuous casting at a drawing speed of 6 cm / s, the cooling water temperature is 28 °C, with on - line electromagnetic stirring (frequency 70 Hz), and cast it into a copper alloy sheet with a thickness of 80 mm; Hot extrusion forming: Polish the contact surfaces of 3 layers of silver alloy sheets and 3 layers of copper alloy sheets to a roughness Ra ≤ 1.6 μm, stack them alternately in the order of "silver - copper - silver -...", place them in a hot extrusion equipment, and conduct hot extrusion at a temperature of 650 °C, a pressure of 150 MPa, and an extrusion ratio of 30:1 to form a composite sheet with a thickness of 16 mm and a dense composite structure (the thickness of each layer of silver and copper alloy sheets is initially compressed to 2.67 mm / layer); Cold drawing: Cold draw the composite sheet into finished products, control the final deformation amount to be 10% (the thickness of each layer of silver and copper alloy sheet is 2.4 mm / layer), and obtain a copper-silver alloy with a thickness of 14.4 mm.

[0028] Among them, the grain size of the silver alloy sheet is 5 μm, and the grain size of the copper alloy sheet is 8 μm.

[0029] Example 3 This example provides a method for preparing a copper-silver alloy, including the following steps: Silver alloying: Take a 1# silver ingot with a purity of 99.99% and add it to a vacuum induction furnace. Add Ce rare earth according to the mass ratio of 0.01% of the silver ingot to the vacuum induction furnace. Under the condition that the vacuum degree ≤ 10 -3 Pa, heat up to 1130 °C and melt, then start electromagnetic stirring (rotation speed 100 r / min), stir for 20 min, and form a uniform silver alloy melt; Copper alloying: Add electrolytic copper with a purity of 99.95% to a non-vacuum induction furnace for melting. Add Cu-P master alloy (P content 20%) according to the mass ratio of 0.5% of the electrolytic copper, add La rare earth according to the mass ratio of 0.02% of the electrolytic copper, place it in the non-vacuum induction furnace, cover the slag, then heat up to 1200 °C and melt, start dual-frequency electromagnetic stirring (dual frequencies are 60 Hz + 220 Hz), stir for min, and obtain a copper alloy melt; Horizontal continuous casting: Continuously cast the above silver alloy melt. During the continuous casting process, continuously cast at a drawing speed of 1 cm / s, the cooling water temperature is 20 °C, and online electromagnetic stirring (frequency 50 Hz), and cast into a 50 mm thick silver alloy sheet under argon protection; Continuously cast the above copper alloy melt. During the continuous casting process, continuously cast at a drawing speed of 3 cm / s, the cooling water temperature is 30 °C, and online electromagnetic stirring (frequency 60 Hz), and cast into a 50 mm thick copper alloy sheet; Hot extrusion forming: Polish the contact surfaces of 4 layers of silver alloy sheets and 4 layers of copper alloy sheets to a roughness Ra ≤ 1.6 μm, and stack them alternately in the order of "silver - copper - silver -...", place them in a hot extrusion equipment, and perform hot extrusion at a temperature of 680 °C, a pressure of 180 MPa, and an extrusion ratio of 20:1 to form a 20 mm thick composite sheet with a dense composite structure (the thickness of each layer of silver and copper alloy sheet is initially compressed to 2.5 mm / layer); Cold drawing: Cold draw the composite sheet into finished products, control the final deformation amount to be 20% (the thickness of each layer of silver and copper alloy sheet is 2 mm / layer), and obtain a copper-silver alloy with a thickness of 16 mm.

[0030] Among them, the grain size of the silver alloy sheet is 5.6 μm, and the grain size of the copper alloy sheet is 7.2 μm.

[0031] The present invention also provides a silver-copper alloy prepared according to the above method for preparing a copper-silver alloy, and this silver-copper alloy can be used as an electrical contact material. Refer to Figure 1 , this electrical contact material 1 has a structure of three layers of silver alloy plates 11 and two layers of copper alloy plates 12. The contact surface between the silver alloy plate 11 and the copper alloy plate 12 is a transition layer. The lower part of the electrical contact material 1 selected by the dashed box shown in the figure is its working surface, which is used as an electrical contact head 13. In the five-layer structure of the electrical contact material, the proportion of the copper layer can reach 40%-50%, saving 30%-50% of silver material compared with the traditional single silver alloy.

[0032] The above embodiments are illustrative of the present invention, not limitations thereof. Any solution obtained by simply transforming the present invention belongs to the protection scope of the present invention.

Claims

1. A method for preparing a copper-silver alloy, characterized in that, It includes the following steps: Silver alloying: Add silver raw materials and rare earth elements into a vacuum induction furnace for mixing. After heating to 1100°C - 1200°C and melting under a vacuum atmosphere, a silver alloy melt is obtained; Copper alloying: Add electrolytic copper into a non-vacuum induction furnace for smelting. After heating to 1200°C - 1300°C and melting, add phosphorus element and rare earth elements for alloying to obtain a copper alloy melt; Horizontal continuous casting: Conduct horizontal continuous casting on the above-mentioned silver alloy melt and copper alloy melt respectively to obtain silver alloy plates and copper alloy plates; Hot extrusion forming: Stack multiple layers of the above-mentioned silver alloy plates and copper alloy plates alternately in the order of "silver - copper - silver - …", and place them in a hot extrusion device for hot extrusion to form a composite plate with a dense composite structure; Cold drawing: Cold draw the composite plate into a finished product to obtain a copper-silver alloy.

2. The method for preparing the copper-silver alloy according to claim 1, characterized in that: In the silver alloying step, the addition amount of rare earth elements is 0.01% - 0.05% of the mass of silver raw materials, and the rare earth elements are cerium, lanthanum or their mixed rare earth.

3. The preparation method of the copper-silver alloy according to claim 1, characterized in that: In the silver alloying step, during the melting process, the vacuum degree of the vacuum induction furnace does not exceed 10 -3 Pa. After the silver raw material and the rare earth element are melted to generate a melt, the electromagnetic stirring device is started and stirred sufficiently for 15 min - 25 min.

4. The preparation method of the copper-silver alloy according to claim 1, characterized in that: In the copper alloying step, the phosphorus element is added in the form of a Cu-P master alloy. The addition amount of the phosphorus element is 0.5% - 5% of the mass of electrolytic copper, and the addition amount of rare earth elements is 0.02% - 0.08% of the mass of electrolytic copper. The rare earth elements are cerium, lanthanum or their mixed rare earth.

5. The preparation method of the copper-silver alloy according to claim 1, characterized in that: In the copper alloying step, cover the slag to purify the molten pool when smelting electrolytic copper, and perform double-frequency electromagnetic stirring on the melt after adding the phosphorus element and rare earth elements.

6. The preparation method of the copper-silver alloy according to claim 1, wherein: In the horizontal continuous casting step, control the drawing speed at 1 cm / s - 10 cm / s, the cooling water temperature at 20°C - 30°C. The continuous casting process is carried out under the protection of a protective gas, and online electromagnetic stirring is performed on the silver alloy melt and copper alloy melt during the continuous casting process to refine the grains.

7. The preparation method of the copper-silver alloy according to claim 1, characterized in that: The thickness of the silver alloy plates and copper alloy plates is 50 mm - 200 mm.

8. The preparation method of the copper-silver alloy according to claim 1, characterized in that: 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 plates and copper alloy plates is 5 - 20 layers.

9. The preparation method of the copper-silver alloy according to claim 1, characterized in that: The contact surface of the silver alloy plates and copper alloy plates is polished to a roughness Ra ≤ 1.6 μm before hot extrusion.

10. The preparation method of the copper-silver alloy according to claim 1, characterized in that: In the cold drawing step, perform multi-pass cold drawing on the composite plate. The single-pass deformation amount is controlled at 5% - 15%. When the deformation amount is large, remove the stress by annealing.

11. A copper-silver alloy prepared by 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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