Silver-based electric contact material with high fusion welding resistance and preparation method of silver-based electric contact material

Abstract

The invention relates to the technical field of electrical contact materials, and discloses a preparation method of a silver-based electrical contact material with high fusion welding resistance, which comprises the following steps: an inner layer is a silver metal oxide material which can be selected from one or a combination of more of silver tin oxide, silver copper oxide, silver zinc oxide, silver tin oxide indium oxide and silver cadmium oxide; and the outer layer is made of a silver-based material with a magnetic function and is formed by combining one or more of silver-nickel powder, silver-iron powder and silver-iron oxide powder. According to the silver-based electric contact material with the high fusion welding resistance and the preparation method of the silver-based electric contact material, through a magnetic field generated by the silver-based material with the magnetism on the outer layer, electric arcs of the contact material on the inner layer can be rapidly moved to the edge of a contact and extinguished, the arcing time is effectively shortened, and compared with an electric contact material in the prior art, under the same load condition, the silver-based electric contact material with the high fusion welding resistance and the preparation method thereof have the advantages that the material has high fusion welding resistance; the arc time is shortened by 30%-50%, the fusion welding force is reduced by 40%-60%, the risk of contact fusion welding is greatly reduced, and the fusion welding resistance is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical contact materials, and specifically to a silver-based electrical contact material with high anti-welding performance and a preparation method thereof. Background Art

[0002] In the field of electrical contact applications, welding is a key problem leading to the failure of switching devices; traditional silver metal oxide electrical contact materials are prone to generating arcs during the on and off processes. The high temperature of the arcs melts the contact point metal, which may cause contact welding, seriously affecting the normal operation and electrical life of switchgears; although there are existing technologies for accelerating the movement or extinguishing of arcs through magnetic fields, such as using magnetic blowout technology with ferromagnetic arc starters to make the arcs enter the arc extinguishing grids of the arc extinguishing chamber, the size and structure of the arc extinguishing system of this solution are bulky and not applicable to small-sized relays.

[0003] After retrieval, according to a silver-based electrical contact material with high anti-welding performance, a preparation method and an application disclosed in the invention patent with the Chinese patent publication number "CN116453889A", the silver-based electrical contact material is a wire, which consists of two silver-based contacts with different systems inside and outside: the inner layer is a silver metal oxide material with anti-burning performance, and the outer layer is a silver-based material with magnetic blowout characteristics; first, two silver-based contact powders with different systems are respectively prepared and made into two round ingots with different diameters. After the ingots are sintered and repressed, they are extruded on a double-extrusion rod backward extruder with a peeling extrusion rod and a conventional extrusion rod. Finally, a double-layer wire is formed, drawn to the required specifications, and cold-headed and formed into rivet-type composite electrical contacts; the electrical contact material described in the present invention can accelerate the movement of the arc to the edge of the contact, thereby realizing the rapid extinguishing of the arc, reducing contact burning, and effectively improving the anti-burning performance of the contact.

[0004] This patent prepares a soft magnetic electrical contact material with self-blowing arc characteristics through different process routes. However, in its first solution, the electrical performance of the contact itself is changed, and the second solution is not applicable to the continuous production mode of single-wire relay rivets, with low production efficiency. In addition, in the process of material preparation in the existing technology, there is a lack of in-depth research on the parameter optimization of the sintering and repressing of different material cylindrical ingots and the subsequent extrusion process, resulting in the need to improve the performance stability and consistency of the final product. At the same time, in the aspect of microstructural regulation of the material, how to further enhance the anti-welding performance and comprehensive electrical performance of the material has not been fully considered. Therefore, a silver-based electrical contact material with high anti-welding performance and a preparation method thereof are proposed to solve the above-mentioned problems. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] In view of the deficiencies of the prior art, the present invention provides a silver-based electrical contact material with high anti-welding performance and a preparation method thereof, which has the advantages of significantly improved anti-welding performance and increased production efficiency. It solves the problems in the prior art that in the process of material preparation, there is a lack of in-depth research on the sintering and repressing of cylindrical ingots of different materials and the parameter optimization of subsequent extrusion processes, resulting in the need to improve the performance stability and consistency of the final product. At the same time, in terms of the regulation of the microstructure of the material, the problem of how to further enhance the anti-welding performance and comprehensive electrical performance of the material has not been fully considered.

[0007] (II) Technical Solution

[0008] To achieve the above-mentioned purpose of significantly improving the anti-welding performance and increasing the production efficiency, the present invention provides the following technical solution: A preparation method of a silver-based electrical contact material with high anti-welding performance, including a silver metal oxide material as the inner layer, which can be selected from one or more combinations of silver tin oxide, silver copper oxide, silver zinc oxide, silver tin indium oxide, and silver cadmium oxide;

[0009] The outer layer is a silver-based material with magnetic function, which is composed of one or more powder combinations of silver nickel, silver iron, and silver iron oxide.

[0010] A preparation method of a silver-based electrical contact material with high anti-welding performance includes the following steps:

[0011] S1: Preparation of inner layer powder: Using the coprecipitation method, dissolve silver nitrate and stannous chloride in deionized water according to the stoichiometric ratio, slowly drop the sodium hydroxide solution under stirring, control the reaction pH value to be 8-9, temperature 50-60 °C, and time 2-3 hours. After the reaction, filter, wash, and dry to obtain silver tin oxide powder with a silver content of 85%.

[0012] S2; Preparation of outer layer powder: Using the mechanical alloying method, put silver powder and nickel powder into a high-energy ball mill according to a mass ratio of 7:3, with a ball-to-material ratio of 10:1, and ball mill for 10-12 hours to obtain a uniform silver nickel powder with a silver content of 70%.

[0013] S3: Preparation of cylindrical ingot: Put the outer layer powder into a latex sleeve with a suitable diameter, and perform cold isostatic pressing for a certain time under a certain pressure to obtain an outer layer cylindrical ingot blank;

[0014] Put the inner layer powder into a latex sleeve with a suitable diameter, and perform cold isostatic pressing for a certain time under a certain pressure to obtain an inner layer cylindrical ingot blank;

[0015] Put the outer layer cylindrical ingot blank and the inner layer cylindrical ingot blank into the corresponding atmosphere sintering furnace respectively, and heat to a specific temperature at a certain heating rate and keep it warm;

[0016] After sintering, the outer layer cylindrical ingot and the inner layer cylindrical ingot are respectively repressed with a repressing die with a suitable diameter under a certain pressure;

[0017] S4: Extrusion process: Heat the re-pressed outer layer ingot to a specific temperature, place it in an extrusion cylinder with a suitable diameter, extrude it with a first extrusion rod of a specific diameter, control the extrusion speed, and leave an outer material loop with a certain unilateral wall thickness;

[0018] Place the inner layer ingot inside the loop, and extrude it in the reverse direction with a second extrusion rod of a specific diameter, control the extrusion speed, to form a double-layer wire with the inner layer being the inner layer material and the outer layer being the outer layer material, and control the thickness of the outer layer material;

[0019] S5: Subsequent processing: Perform multi-pass drawing on the double-layer wire, control the area reduction rate of each pass of drawing, after drawing to the required diameter, pair it with a pure copper wire, and under specific cold heading pressure and die temperature conditions, cold heading form a composite rivet electrical contact.

[0020] Preferably, in S1, the preparation of the inner layer powder can also include two other methods: One method uses the sol-gel method, with silver nitrate and zinc acetate as raw materials, dissolve them in an appropriate amount of organic solvent, add a complexing agent and a catalyst, stir to form a sol, and then through processes such as gelation, drying, and calcination, obtain silver-zinc oxide powder with a silver content of 90%;

[0021] Another method uses a pre-oxidation process, mix silver powder and cadmium powder evenly according to a mass ratio of 8.5:1.5, heat it in an oxygen atmosphere to 350 - 450 °C, and keep it warm for 4 - 5 hours to obtain silver cadmium oxide powder with a silver content of 85%.

[0022] Preferably, in S2, the preparation of the outer layer powder can also include two other schemes: One method uses a pre-oxidation process, mix silver powder and iron powder evenly according to a mass ratio of 8:2, heat it in the air to 400 - 500 °C, and keep it warm for 3 - 4 hours to obtain silver iron oxide powder with a silver content of 86%;

[0023] Another method uses a powder mixing process, put silver powder, nickel powder and iron oxide powder into a plowshare type powder mixer according to a mass ratio of 8:1:1, mix the powder for 4 - 5 hours to obtain a uniform silver-nickel-iron oxide powder with a silver content of 80%.

[0024] Preferably, in S3, put the outer layer powder into a latex sleeve with a diameter of 45 - 55 mm, under a pressure of 230 - 280 MPa, and keep the pressure for 18 - 22 minutes to obtain the outer layer ingot blank;

[0025] Put the inner layer powder into a latex sleeve with a diameter of 35 - 45 mm, under a pressure of 200 - 240 MPa, and keep the pressure for 24 - 28 minutes to obtain the inner layer ingot blank;

[0026] Put the outer circular ingot blank and the inner circular ingot blank into the corresponding atmosphere sintering furnace respectively. The outer layer is heated to 820 - 850°C at a rate of 4 - 6°C per minute and kept warm for 2.2 - 2.8 hours, while the inner layer is heated to 780 - 830°C at a rate of 3 - 5°C per minute and kept warm for 1.8 - 2.3 hours.

[0027] The sintered outer circular ingot is repressed using a repressing die with a diameter of 41 - 51 mm under a pressure of 320 - 380 MPa; the sintered inner circular ingot is repressed using a repressing die with a diameter of 36 - 41 mm under a pressure of 300 - 340 MPa.

[0028] Preferably, in S4, the repressed outer circular ingot is heated to 380 - 420°C, the diameter of the extrusion cylinder is 47 - 57 mm, the diameter of the first extrusion rod is 38 - 46 mm, the speed is 7 - 9 mm / s, leaving a silver-nickel ring with a single-sided wall thickness of 3 - 5 mm.

[0029] Put the inner circular ingot into the ring, with the diameter of the second extrusion rod being 44 - 52 mm, the speed being 5 - 7 mm / s, and the outer layer thickness being 13 - 17% of the wire diameter.

[0030] Preferably, in S5, the double-layer wire is drawn in 4 - 6 passes, and the reduction rate of each pass is controlled to be 12 - 20%, and the processing is carried out under the conditions of a cold heading pressure of 60 - 80 MPa and a die temperature of 22 - 30°C.

[0031] The present invention provides a silver-based electrical contact material with high anti-welding performance prepared according to the described preparation method.

[0032] (III) Beneficial effects

[0033] Compared with the prior art, the present invention provides a silver-based electrical contact material with high anti-welding performance and its preparation method, having the following beneficial effects:

[0034] 1. For the silver-based electrical contact material with high anti-welding performance and its preparation method, through the magnetic field generated by the silver-based material with magnetism in the outer layer, the arc of the inner contact material can be quickly moved to the edge of the contact and extinguished, effectively reducing the arcing time. Compared with the electrical contact materials in the prior art, the arcing time of the material of the present invention is shortened by 30% - 50% under the same load conditions, and the welding force is reduced by 40% - 60%, greatly reducing the risk of contact welding and significantly improving the anti-welding performance.

[0035] 2. For the silver-based electrical contact material with high anti-welding performance and its preparation method, through the optimized preparation process, especially the multi-pass drawing and the precisely controlled cold heading forming process, the production process is more efficient and stable, reducing the rejection rate and the number of reworks. Compared with the traditional process, the production efficiency is increased by 30% - 40%, which is suitable for large-scale industrial production.

[0036] 3. The silver-based electrical contact material with high anti-welding performance and its preparation method. Through precise control of process parameters and microstructure regulation, the produced silver-based electrical contact material has high stability and consistency in performance. The fluctuation range of various performance indicators of the product is significantly reduced, which can better meet the strict requirements of different electrical equipment for material performance, and improve the overall quality and reliability of electrical equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of the silver-based electrical contact material with high anti-welding performance and its preparation method of the present invention;

[0038] Figure 2 It is a specific flow chart of the silver-based electrical contact material with high anti-welding performance and its preparation method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] Embodiment 1

[0041] A silver-based electrical contact material with high anti-welding performance and its preparation method include the following contents:

[0042] Inner layer powder preparation: The silver tin oxide powder is prepared by the co-precipitation method. Silver nitrate and stannous chloride are dissolved in deionized water according to the stoichiometric ratio. Under stirring conditions, sodium hydroxide solution is slowly added dropwise, and the reaction pH value is controlled at 8 - 9, the reaction temperature is 50 - 60 °C, and the reaction time is 2 - 3 hours; after the reaction, the precipitate is filtered, washed, and dried to obtain silver tin oxide powder with a silver content of 85%.

[0043] Outer layer powder preparation: The silver nickel powder is prepared by mechanical alloying. Silver powder and nickel powder are put into a high-energy ball mill according to a mass ratio of 7:3, the ball-to-powder ratio is 10:1, and the ball milling time is 10 - 12 hours to obtain a uniform silver nickel powder with a silver content of 70%.

[0044] Cylindrical ingot preparation: The silver nickel powder is put into a latex sleeve with a diameter of 50 mm, and cold isostatic pressing is carried out under a pressure of 250 MPa for a holding time of 20 minutes to obtain a silver nickel round ingot blank with a diameter of 48 mm;

[0045] Put the silver tin oxide powder into a latex sleeve with a diameter of 40 mm, and perform cold isostatic pressing under a pressure of 220 MPa for 25 minutes to obtain a silver tin oxide ingot blank with a diameter of 38 mm.

[0046] Put the silver nickel ingot blank into a vacuum atmosphere sintering furnace and heat it to 850 °C at a heating rate of 5 °C per minute, and hold for 2.5 hours; put the silver tin oxide ingot blank into a nitrogen protection atmosphere sintering furnace and heat it to 800 °C at a heating rate of 4 °C per minute, and hold for 2 hours.

[0047] The sintered silver nickel ingot is repressed using a repressing die with a diameter of 46 mm under a pressure of 350 MPa; the sintered silver tin oxide ingot is repressed using a repressing die with a diameter of 36 mm under a pressure of 320 MPa.

[0048] Extrusion process: Heat the repressed silver nickel ingot to 400 °C, put it into an extrusion cylinder with a diameter of 52 mm, and use a first extrusion rod with a diameter of 42 mm for extrusion. The extrusion speed is 8 mm / s. After extrusion, a silver nickel sleeve with a single-sided wall thickness of 3 mm remains on the inner wall of the extrusion cylinder.

[0049] Put the silver tin oxide ingot into the silver nickel sleeve and use a second extrusion rod with a diameter of 48 mm for reverse extrusion. The extrusion speed is 5 mm / s to form a double-layer wire with silver tin oxide material on the inner layer and silver nickel material on the outer layer. The thickness of the outer layer material is 15% of the diameter of the whole wire.

[0050] Subsequent processing: Perform drawing processing on the double-layer wire. Use 5 passes of drawing, and the reduction rate of each pass is 15%. After drawing to the required diameter, pair it with a pure copper wire and perform cold heading forming to make a composite rivet electrical contact under the conditions of a cold heading pressure of 60 MPa and a die temperature of 25 °C.

[0051] Performance test: Test the made rivet electrical contact in an inductive load household relay with AC250V and 15A. Compared with conventional materials, the electrical life of the material of the present invention has been increased by 18%.

[0052] Example 2

[0053] Preparation of inner layer powder: Prepare silver zinc oxide powder by the sol-gel method. Use silver nitrate and zinc acetate as raw materials, dissolve them in an appropriate amount of organic solvent, add a complexing agent and a catalyst, form a sol under stirring conditions, and then go through processes such as gelation, drying, and calcination to obtain silver zinc oxide powder with a silver content of 90%.

[0054] Preparation of outer-layer powder: Prepare silver iron oxide powder by using a pre-oxidation process. After mixing silver powder and iron powder evenly at a mass ratio of 8:2, heat them in air to 400 - 500 °C and keep warm for 3 - 4 hours to fully oxidize the iron, obtaining silver iron oxide powder with a silver content of 86%.

[0055] Preparation of cylindrical ingot: Put the silver iron oxide powder into a latex sleeve with a diameter of 45 mm, and perform cold isostatic pressing under a pressure of 230 MPa for a holding time of 22 minutes to obtain a silver iron oxide round ingot blank with a diameter of 43 mm;

[0056] Put the silver zinc oxide powder into a latex sleeve with a diameter of 35 mm, and perform cold isostatic pressing under a pressure of 200 MPa for a holding time of 28 minutes to obtain a silver zinc oxide round ingot blank with a diameter of 33 mm;

[0057] Put the silver iron oxide round ingot blank into an air atmosphere sintering furnace, heat it to 880 °C at a heating rate of 4 °C per minute, and keep warm for 2.2 hours; put the silver zinc oxide round ingot blank into a nitrogen - protected atmosphere sintering furnace, heat it to 780 °C at a heating rate of 3 °C per minute, and keep warm for 2.3 hours;

[0058] The sintered silver iron oxide round ingot is repressed using a repressing die with a diameter of 41 mm under a pressure of 320 MPa; the sintered silver zinc oxide round ingot is repressed using a repressing die with a diameter of 31 mm under a pressure of 300 MPa.

[0059] Extrusion process: Heat the repressed silver iron oxide round ingot to 380 °C, put it into an extrusion cylinder with a diameter of 47 mm, and extrude it using a first extrusion rod with a diameter of 38 mm at an extrusion speed of 7 mm per second. After extrusion, a silver iron oxide ring with a single - side wall thickness of 4 mm is left on the inner wall of the extrusion cylinder;

[0060] Put the silver zinc oxide round ingot into the silver iron oxide ring, and perform reverse extrusion using a second extrusion rod with a diameter of 44 mm at an extrusion speed of 6 mm per second to form a double - layer wire with silver zinc oxide material as the inner layer and silver iron oxide material as the outer layer. The thickness of the outer - layer material is 13% of the diameter of the whole wire.

[0061] Subsequent processing: Perform drawing processing on the double - layer wire. Use 6 - pass drawing, with a reduction rate of 12% for each pass. After drawing to the required diameter, pair it with a pure copper wire, and under the conditions of a cold - heading pressure of 70 MPa and a die temperature of 22 °C, cold - head and form a composite - type rivet electrical contact.

[0062] Performance test: Test the obtained rivet electrical contact in an LED load relay with AC250V and 38 9 - W downlights. Compared with conventional materials, the electrical life of the material of the present invention is increased by 15%.

[0063] Example Three

[0064] Inner layer powder preparation: Prepare silver cadmium oxide powder by using a pre-oxidation process. After mixing silver powder and cadmium powder evenly according to a mass ratio of 8.5:1.5, heat them in an oxygen atmosphere to 350 - 450 °C and keep the temperature for 4 - 5 hours to obtain silver cadmium oxide powder with a silver content of 85%.

[0065] Outer layer powder preparation: Prepare silver nickel iron oxide powder by using a powder mixing process. Put silver powder, nickel powder and iron oxide powder into a plowshare type powder mixer according to a mass ratio of 8:1:1, and mix the powder for 4 - 5 hours to obtain uniform silver nickel iron oxide powder with a silver content of 80%.

[0066] Cylindrical ingot preparation: Put the silver nickel iron oxide powder into a latex sleeve with a diameter of 55 mm, and perform cold isostatic pressing under a pressure of 280 MPa for a holding time of 18 minutes to obtain a silver nickel iron oxide round ingot blank with a diameter of 53 mm;

[0067] Put the silver cadmium oxide powder into a latex sleeve with a diameter of 45 mm, and perform cold isostatic pressing under a pressure of 240 MPa for a holding time of 24 minutes to obtain a silver cadmium oxide round ingot blank with a diameter of 43 mm;

[0068] Put the silver nickel iron oxide round ingot blank into a vacuum atmosphere sintering furnace, and heat it to 820 °C at a heating rate of 6 °C per minute and keep the temperature for 2.8 hours; put the silver cadmium oxide round ingot blank into a nitrogen - protected atmosphere sintering furnace, and heat it to 830 °C at a heating rate of 5 °C per minute and keep the temperature for 1.8 hours;

[0069] The sintered silver nickel iron oxide round ingot is repressed by using a repressing die with a diameter of 51 mm under a pressure of 380 MPa; the sintered silver cadmium oxide round ingot is repressed by using a repressing die with a diameter of 41 mm under a pressure of 340 MPa.

[0070] Extrusion process: Heat the repressed silver nickel iron oxide round ingot to 420 °C, put it into an extrusion cylinder with a diameter of 57 mm, and extrude it by using a first extrusion rod with a diameter of 46 mm. The extrusion speed is 9 mm / s. After extrusion, a silver nickel iron oxide ring with a single - side wall thickness of 5 mm is left on the inner wall of the extrusion cylinder;

[0071] Put the silver cadmium oxide round ingot into the silver nickel iron oxide ring, and perform reverse extrusion by using a second extrusion rod with a diameter of 52 mm. The extrusion speed is 7 mm / s to form a double - layer wire with silver cadmium oxide material as the inner layer and silver nickel iron oxide material as the outer layer. The thickness of the outer layer material is 17% of the diameter of the whole wire.

[0072] Subsequent processing: The double-layer wire is drawn. Four passes of drawing are adopted, and the area reduction rate for each pass of drawing is 20%. After drawing to the required diameter, it is paired with a pure copper wire. Under the conditions of a cold heading pressure of 80 MPa and a die temperature of 30 °C, a composite rivet electrical contact is cold-headed and formed.

[0073] Performance test: The prepared rivet electrical contact is tested in a relay with an AC 250 V, 10 A resistive load. Compared with conventional materials, the electrical life of the material of the present invention is increased by 20%, the arcing time is significantly shortened, and the welding marks on the contact surface are significantly reduced, further verifying the effectiveness of the material of the present invention in improving the anti-welding performance.

[0074] Therefore, as shown by the above embodiments, different from the traditional single material or simple mixed material structure, the double-layer structure designed by the present invention gives full play to the good electrical and thermal conductivity of the inner silver metal oxide material and the magnetic field arc-blowing effect of the outer silver-based magnetic material. The two work together to effectively improve the anti-welding performance.

[0075] At the same time, in the optimization of process parameters, in each link such as cylindrical ingot preparation, sintering and repressing, extrusion, and subsequent processing, the process parameters are precisely studied and optimized. For example, different sintering atmospheres, heating rates, holding times, and repressing pressures are adopted for cylindrical ingots of different materials; during the extrusion process, parameters such as extrusion temperature, speed, pressure, and the diameter ratio of the extrusion rod are precisely controlled. These optimized parameters can significantly improve the stability and consistency of product performance.

[0076] Moreover, through the precise control of process parameters during the preparation process, effective regulation of the microstructure of the material is achieved, including the control of grain size and distribution and the optimization of the material interface structure, thereby further enhancing the anti-welding performance and comprehensive electrical performance of the material.

[0077] In summary, for the silver-based electrical contact material with high anti-welding performance and its preparation method, through the magnetic field generated by the magnetic silver-based material on the outer layer, the arc of the inner contact material can be quickly moved to the edge of the contact and extinguished, effectively reducing the arcing time. Compared with the electrical contact materials of the prior art, the material of the present invention has a 30%-50% shorter arcing time and a 40%-60% lower welding force under the same load conditions, greatly reducing the risk of contact welding and significantly improving the anti-welding performance.

[0078] Furthermore, through the optimized preparation process, especially the multi-pass drawing and precisely controlled cold heading forming process, the production process is more efficient and stable, reducing the scrap rate and the number of reworks. Compared with the traditional process, the production efficiency is increased by 30%-40%, which is suitable for large-scale industrial production.

[0079] Secondly, through precise control of process parameters and microstructure regulation, the produced silver-based electrical contact materials have high stability and consistency in performance. The fluctuation range of various performance indicators of the products is significantly reduced, enabling better meeting the strict requirements of different electrical equipment for material performance, and improving the overall quality and reliability of electrical equipment.

[0080] It should be noted that in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0081] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a silver-based electrical contact material with high resistance to welding, characterized in that: The inner layer includes a silver metal oxide material, which can be selected from one or more combinations of silver tin oxide, silver copper oxide, silver zinc oxide, silver tin oxide indium oxide, and silver cadmium oxide; The outer layer is a silver-based material with magnetic function, which is composed of one or more powders of silver nickel, silver iron, and silver iron oxide.

2. The method for preparing a silver-based electrical contact material with high anti-welding performance according to claim 1, characterized in that: The following steps are involved: S1: Preparation of inner layer powder: using coprecipitation method, dissolve silver nitrate and stannous chloride in deionized water according to the stoichiometric ratio, slowly add sodium hydroxide solution under stirring, control the reaction pH value to 8-9, temperature to 50-60°C, time to 2-3 hours, filter, wash and dry after the reaction to obtain silver tin oxide powder with a silver content of 85%; S2; outer layer powder preparation: using mechanical alloying method, silver powder and nickel powder are put into a high-energy ball mill at a mass ratio of 7:3, a ball-to-material ratio of 10:1, and ball milled for 10-12 hours to obtain a uniform silver-nickel powder with a silver content of 70%; S3: Preparation of cylindrical ingot: put the outer layer powder into a latex sleeve with a suitable diameter, and cold isostatically press it under a certain pressure for a certain time to obtain an outer layer round ingot blank; The inner layer powder is placed in a latex sleeve of suitable diameter, and cold isostatically pressed under a certain pressure for a certain period of time to obtain an inner layer round ingot blank; The outer layer round ingot blank and the inner layer round ingot blank are placed in a corresponding atmosphere sintering furnace, heated to a specific temperature at a certain heating rate and kept warm; The sintered outer and inner round ingots are respectively pressed under a certain pressure using a pressing mold with a suitable diameter; S4: Extrusion process: the outer layer round ingot after re-pressing is heated to a specific temperature, placed in an extrusion cylinder with a suitable diameter, extruded with a first extrusion rod with a specific diameter, and the extrusion speed is controlled to leave an outer layer material trap with a certain single-side wall thickness; An inner round ingot is placed in the trap, and a second extrusion rod with a specific diameter is used to extrude the ingot in the opposite direction, and the extrusion speed is controlled to form a double-layer wire with an inner layer of inner layer material and an outer layer of outer layer material, and the thickness of the outer layer material is controlled; S5: Subsequent processing: The double-layer wire is drawn in multiple passes, and the surface reduction rate of each drawing pass is controlled. After drawing to the required diameter, it is paired with pure copper wire. Under specific cold heading pressure and mold temperature conditions, composite rivet electrical contacts are formed by cold heading.

3. The method for preparing a silver-based electrical contact material with high resistance to welding according to claim 2, characterized in that: In S1, the inner layer powder preparation may also include two other methods: one method adopts a sol-gel method, using silver nitrate and zinc acetate as raw materials, dissolving them in an appropriate amount of organic solvent, adding a complexing agent and a catalyst, stirring to form a sol, and then gelling, drying, calcining and other processes to obtain silver zinc oxide powder with a silver content of 90%; The other method uses a pre-oxidation process, in which silver powder and cadmium powder are uniformly mixed in a mass ratio of 8.5:1.5, heated to 350-450° C. in an oxygen atmosphere, and kept warm for 4-5 hours to obtain silver cadmium oxide powder with a silver content of 85%.

4. The method for preparing a silver-based electrical contact material with high resistance to welding according to claim 2, characterized in that: In S2, the outer layer powder preparation may also include two other schemes: one method adopts a pre-oxidation process, silver powder and iron powder are mixed evenly in a mass ratio of 8:2, heated to 400-500° C. in air, and kept warm for 3-4 hours to obtain silver iron oxide powder with a silver content of 86%; Another method uses a powder mixing process, in which silver powder, nickel powder and iron oxide powder are put into a plowshare type powder mixer at a mass ratio of 8:1:1, and the powders are mixed for 4-5 hours to obtain a uniform silver-nickel-iron oxide powder with a silver content of 80%.

5. The method for preparing a silver-based electrical contact material with high anti-welding performance according to claim 2, characterized in that: In S3, the outer layer powder is placed in a latex sleeve with a diameter of 45-55 mm, the pressure is 230-280 MPa, and the pressure holding time is 18-22 minutes to obtain an outer layer round ingot blank; The inner layer powder is placed in a latex sleeve with a diameter of 35-45 mm, the pressure is 200-240 MPa, and the pressure holding time is 24-28 minutes to obtain an inner layer round ingot blank; The outer layer round ingot blank and the inner layer round ingot blank are placed in the corresponding atmosphere sintering furnace respectively, the outer layer is heated to 820-850°C at 4-6°C / min and kept at this temperature for 2.2-2.8 hours, and the inner layer is heated to 780-830°C at 3-5°C / min and kept at this temperature for 1.8-2.3 hours; The outer round ingot after sintering is re-pressed at a pressure of 320-380 MPa using a 41-51 mm diameter re-pressing mold; the inner round ingot after sintering is re-pressed at a pressure of 300-340 MPa using a 36-41 mm diameter re-pressing mold.

6. The method for preparing a silver-based electrical contact material with high anti-welding performance according to claim 1, characterized in that: In S4, the outer layer round ingot after re-pressing is heated to 380-420°C, the diameter of the extrusion cylinder is 47-57 mm, the diameter of the first extrusion rod is 38-46 mm, the speed is 7-9 mm / second, and a silver-nickel ring with a single-side wall thickness of 3-5 mm is left; The inner layer round ingot is placed in the trap, with the second extrusion rod having a diameter of 44-52 mm, a speed of 5-7 mm / sec, and an outer layer thickness of 13-17% of the wire diameter.

7. The method for preparing a silver-based electrical contact material with high anti-welding performance according to claim 1, characterized in that: In S5, the double-layer wire is drawn in 4-6 passes, and the surface reduction rate of each drawing pass is controlled to be 12-20%, and the cold heading pressure is 60-80MPa and the mold temperature is 22-30℃.

8. A silver-based electrical contact material with high resistance to welding prepared by the preparation method according to claim 2.

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