A method for preparing a silver tin oxide contact material having good plasticity and arc erosion resistance

Abstract

The application discloses a preparation method of a silver tin oxide electric contact material with good plasticity and arc erosion resistance, and comprises the following steps: first, taking Ag ingot, Sn ingot and X ingot of an additive element to prepare Ag-Sn alloy powder with a required particle size; the obtained powder is oxidized to obtain AgSnO2 mother powder; then, the required amounts of Ag, Sn and X elements are calculated according to the component proportion of the required preparation material, and are weighed for standby, wherein the Sn and X elements are weighed in the form of AgSnO2 mother powder, and the Ag element is weighed in the form of silver nitrate and AgSnO2 mother powder; then, an alkaline substance in excess of silver nitrate is weighed, and the alkaline substance and the silver nitrate are respectively prepared into solutions; then, the weighed AgSnO2 mother powder is added into the alkaline solution, and the silver nitrate solution is continuously added for reaction to obtain AgSnO2 powder; and finally, the obtained powder is prepared into a silver tin oxide electric contact through a conventional process. The contact prepared by adopting the method has good plasticity and arc erosion resistance.

Description

Technical Field

[0001] This invention relates to a method for preparing silver-based electrical contact materials, specifically a method for preparing a silver-tin oxide electrical contact material with good plasticity and resistance to arc erosion. Background Technology

[0002] Silver-tin oxide electrical contact material is a metal-based composite material composed of Ag as the matrix and SnO2 and other oxide additives as reinforcing phases. The Ag matrix acts as the conductive medium, while the oxides serve as reinforcing phases to improve the material's corrosion resistance. The oxides are brittle, non-conductive substances; their addition reduces the material's conductivity and plasticity, but increases the viscosity of the molten pool, exerting a pinning effect and improving the material's resistance to ablation and welding. Different oxide addition methods have varying effects on the material's plasticity and arc erosion resistance. Therefore, the plasticity and arc erosion resistance of silver-tin oxide materials can be improved by studying the oxide addition method, oxide particle size, and the degree of oxide dispersion within the Ag matrix.

[0003] The addition of oxides to existing silver-tin oxide electrical contact materials can be divided into two categories. One category involves directly adding oxides as raw materials to the Ag matrix. In this type, the oxides and Ag matrix are mixed as completely independent particles, resulting in relatively large oxide particles, good material plasticity, but poor arc erosion resistance. Common preparation processes include powder metallurgy and chemical coating. The other category involves preparing an alloy from the corresponding alloying elements and Ag matrix, followed by oxidation in an oxygen atmosphere. In this type, the oxides precipitate in a wavy pattern, and the in-situ generated oxide particles are dispersed within the Ag matrix, without individual Ag matrix particles. This material exhibits good arc erosion resistance but poor plasticity. Common preparation processes include internal alloy oxidation and alloy powder pre-oxidation. To improve the plasticity and arc erosion resistance of silver-tin oxide materials, some contact manufacturers and research institutions have conducted related research and achieved certain results, such as:

[0004] Patent CN101707153A discloses a method for preparing fine-particle tin oxide-reinforced silver-based electrical contact materials. Specifically, AgSn alloy powder and additives are ball-milled in an oxygen atmosphere with an oxygen pressure of 0.5–5 MPa. The resulting powder is annealed and isostatically pressed into a blank, which is then subjected to sintering, hot pressing, re-firing, and hot extrusion processes to obtain the silver tin oxide material. This invention uses a high-pressure oxidizing atmosphere to ball-mill the AgSn alloy powder and additives, allowing the pre-oxidation of the AgSn alloy powder to occur simultaneously with the ball milling and dispersion process. This results in the SnO2 particles obtained from oxidation being dispersed throughout the Ag matrix, leading to the prepared silver tin oxide material possessing an ideal submicron or nanostructure. However, the method described in this invention requires high-energy ball milling, which consumes a lot of energy. On the other hand, high-energy ball milling can produce flake-shaped or saucer-shaped AgSnO2 submicron or nanoparticles. The porosity of the isostatically pressed blank of this shape is relatively high. High porosity will inevitably reduce the processing performance of the material. Furthermore, since oxidation and high-energy ball milling are carried out simultaneously, the brittle SnO2 particles are mainly distributed on the surface of AgSnO2 submicron or nanoparticles. In addition, the dispersion strengthening of nanoparticles further deteriorates the processing performance of the material. Therefore, the processing performance of the resulting silver tin oxide material is poor.

[0005] Chinese patent CN106653410A discloses a high-performance, environmentally friendly silver-tin oxide electrical contact material and its preparation method. This silver-tin oxide electrical contact material consists of a multi-layered coating powder prepared by a chemical coating method. The multi-layered structure of the coating powder includes a tin oxide core, a bismuth oxide layer coating the surface of the tin oxide core, a silver layer coating the surface of the bismuth oxide layer, and other non-ferrous metal oxide layers coating the surface of the silver layer. The tin oxide matrix is ​​mainly composed of tin dioxide, the bismuth oxide layer is mainly composed of bismuth trioxide, the silver layer is mainly composed of silver, and the other non-ferrous metal oxide layers are composed of other non-ferrous metal oxides. The silver-tin oxide contact material prepared by this invention has good uniformity and significantly improved processing performance. However, it does not solve the problem of large oxide particle size. Furthermore, the multi-layered cyclic coating of oxides further increases the particle size of the oxides, making the production process relatively complex, with many production steps and difficult process control.

[0006] Chinese patent CN107988505A discloses a method for preparing a low-contact-resistance, high-performance silver-tin oxide electrical contact material. The steps are as follows: First, melting and casting Ag ingots, Sn ingots, In ingots, and additive X; second, extruding or forging the obtained ingots; third, grinding and polishing; fourth, double-sided three-layer cold lamination or double-sided three-layer hot lamination; fifth, heat treatment; sixth, cold rolling and stamping; seventh, internal oxidation; and eighth, cleaning, etc., to obtain the low-contact-resistance, high-performance silver-tin oxide electrical contact material. The silver-tin oxide electrical contact material prepared by this method has a smooth contact surface, low contact resistance and temperature, and significantly improved material hardness and electrical life. However, because the oxide content gradually increases from the outer (pure silver) to the inner (AgSnO2) of the working surface, meaning the contact surface to the interior has a distinct layered distribution, the performance of the remaining material will significantly decrease as the high-performance surface layer is ablated, resulting in some material waste and relatively high cost. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing a silver tin oxide electrical contact material with good plasticity and resistance to arc erosion, in order to address the shortcomings of the existing technology.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A method for preparing a silver-tin oxide electrical contact material with good plasticity and resistance to arc erosion includes the following steps:

[0010] 1) Ag-Sn alloy powder with particle size D90≤30μm and D50 in 10~15μm is prepared by processing Ag ingot, Sn ingot and X ingot; wherein, X is one or more of any elements that can form alloys with Ag and Sn and can improve their electrical properties;

[0011] 2) The obtained Ag-Sn alloy powder was prepared by powder alloy pre-oxidation under low temperature and high oxygen pressure conditions to obtain AgSnO2 master powder with a particle size D50 of 12-17 μm. The SnO2 precipitate particle size in the obtained AgSnO2 master powder reached the nanoscale. The low temperature and high oxygen pressure refers to the conditions of pressure of 20-40 atmospheres and oxidation temperature ≤600℃.

[0012] 3) Calculate the required amounts of Ag, Sn, and X elements according to the required composition ratio of the materials to be prepared, and weigh them for later use; when weighing, Sn and X elements are weighed in the form of AgSnO2 master powder, and Ag elements are weighed in two forms, one part in the form of silver nitrate and the remaining part in the form of AgSnO2 master powder.

[0013] 4) Weigh out an excess of alkaline substance relative to the mass of silver nitrate, and then use water to prepare alkaline solution and silver nitrate solution respectively;

[0014] 5) Add the weighed AgSnO2 mother powder to an alkaline solution to obtain an alkaline suspension; then add the prepared silver nitrate solution to the alkaline suspension to react until all the silver ions in the silver nitrate solution are replaced, and AgSnO2 powder with a pure silver layer on the surface of the AgSnO2 mother powder is obtained.

[0015] 6) The obtained AgSnO2 powder is subjected to isostatic pressing, sintering and extrusion processes to obtain silver tin oxide electrical contact material with good plasticity and resistance to electric arc erosion.

[0016] In step 1) of the above preparation method, element X as an additive can be a conventional choice in the prior art, specifically selected from one or more combinations of Bi, Cu, In, Ni, Sb and Zn. In this step, for the ratio of Ag ingot, Sn ingot and X ingot, those skilled in the art can use existing knowledge to roughly weigh the required amount of Ag, Sn and X elements according to the composition ratio of the material to be prepared. For example, if AgSnO2(8) contacts need to be prepared later, Ag ingot and Sn ingot can be weighed in a weight ratio of 77.7 to 90.5: 9.5 to 22.3; or if AgSnO2(12) contacts containing 1% added element X need to be prepared later, Ag ingot, Sn ingot and X ingot can be weighed in a weight ratio of 64.9 to 85.7: 12.8 to 31.45: 1.5 to 3.65.

[0017] In step 1) of the above preparation method, Ag ingots, Sn ingots, and X ingots can be processed using existing conventional techniques to obtain Ag-Sn alloy powder with a particle size D90 ≤ 30 μm and D50 between 10 and 15 μm. The applicant has found that spherical or near-spherical Ag-Sn alloy powder has a certain influence on the performance of the obtained silver-tin oxide electrical contact material. Therefore, this application preferably uses an atomization process to obtain spherical or near-spherical Ag-Sn alloy powder with a particle size meeting the above requirements.

[0018] The applicant discovered in experiments that AgSnO2 master powder with a particle size D50 of 12–17 μm could only be obtained under low temperature and high oxygen pressure conditions, and the SnO2 precipitate particle size in the obtained AgSnO2 master powder reached the nanoscale. In step 2) of the above preparation method, the pre-oxidation time under conditions of 20–40 atmospheres and oxidation temperature ≤600℃ is usually 24–96 h, and the oxidation temperature is further preferred to be 350–450℃.

[0019] In step 3) of the above preparation method, the composition ratio of the silver tin oxide electrical contact material to be prepared is the same as that in the prior art. Preferably, in the silver tin oxide contact material to be prepared, the content of tin oxide is 5-15 wt%, the content of element X (calculated as its oxide) is 0-2 wt%, and the balance is Ag; more preferably, the content of tin oxide is 8-12 wt%, the content of element X (calculated as its oxide) is 0-2 wt%, and the balance is Ag.

[0020] In step 3) of the above preparation method, the silver weighed in the form of silver nitrate accounts for 30-70 wt% of the total weight of Ag element, more preferably 40-60 wt% of the total weight of Ag element. In this way, the silver that is replaced can be better and more completely coated on the surface of AgSnO2 master powder, thereby better improving the plasticity and conductivity of the obtained material.

[0021] In step 4) of the above preparation method, the preferred molar ratio of silver nitrate to the alkaline substance is 1:1.1 to 1.3. The alkaline substance can be a conventional choice in the prior art, preferably sodium hydroxide or ammonia. There are no particular requirements for the concentrations of the alkaline solution and the silver nitrate solution; preferably, the concentration of the alkaline solution is 4 to 6 mol / L, and the concentration of the silver nitrate solution is 2 to 4 mol / L.

[0022] The applicant's experience shows that the time required for the prepared silver nitrate solution to be added to the alkaline suspension and reacted until all the silver ions in the silver nitrate solution are displaced is usually greater than or equal to 2 hours. In this application, it is preferred that the reaction time for the prepared silver nitrate solution to be added to the alkaline suspension is 2 to 3 hours.

[0023] In step 6) of the above preparation method, the isostatic pressing, sintering, and extrusion processes are operated in the same way as existing conventional processes. Specifically, the isostatic pressing pressure is usually 100-300 MPa; sintering is carried out in an air atmosphere, the sintering temperature is usually 900-960℃, and the sintering time is 5-10 hours; the extrusion temperature is usually 800-900℃, and the extrusion ratio is 150-250. In this step, after extruding to obtain AgSnO2 wire or strip, the wire is drawn and annealed to the required size using conventional drawing processes, and then processed into integral or composite silver oxide rivet contacts using a riveting machine; after rolling the obtained strip to the required size, it is stamped to obtain silver oxide sheet contacts of the corresponding specifications.

[0024] Compared with the prior art, the present invention is characterized by:

[0025] 1. Ag element is weighed in two forms: silver nitrate and Ag ingot, which are used in the subsequent chemical co-deposition method and powder alloy pre-oxidation process, respectively. The preparation process combines the two processes of powder alloy pre-oxidation and chemical co-deposition.

[0026] 2. A special low-temperature, high-oxygen-pressure pre-oxidation process was used to obtain AgSnO2 master powder with a specific particle size and nanoscale SnO2 precipitates on the surface (the particle size D50 of the AgSnO2 master powder is 12-17 μm, and the SnO2 precipitate particle size in the obtained AgSnO2 master powder reaches the nanoscale). Based on the obtained master powder, a chemical co-deposition method was used to prepare AgSnO2 powder with a micron-thick pure silver layer on the outer layer and nanoscale SnO2 precipitate particle size. The combination of the two processes effectively improved the dispersion of the reinforcing phase in the microstructure, further improved the plasticity and conductivity of the material, and improved the plasticity and arc erosion resistance of the obtained silver tin oxide material, which is beneficial to the stability of the subsequent product quality. AgSnO2 electrical contact material is a metal matrix composite material composed of Ag as the matrix and SnO2 and other oxide additive ceramic particles as the reinforcing phase. The Ag matrix acts as a conductive medium, and the ceramic oxide particles act as reinforcing phases to improve the corrosion resistance of the material. Ceramic oxide particles are brittle, non-conductive substances. Their addition reduces the conductivity and plasticity of the material, but increases the viscosity of the molten pool, exerting a pinning effect on the molten pool and improving the material's resistance to ablation and welding. The Ag matrix is ​​the best conductive medium, possessing excellent ductility and plasticity. As a ceramic matrix composite material, AgSnO2 has certain voids between particles in its microstructure. Higher porosity deteriorates the material's plasticity, conductivity, and electrical properties. Composite materials with brittle phase particles in contact have higher porosity than those with plastic phase particles on the surface. Therefore, coating the AgSnO2 masterbatch particles with a layer of plastic Ag matrix can improve the material's conductivity and plasticity. Meanwhile, the nano-sized brittle SnO2 precipitated on the surface of the AgSnO2 masterbatch particles ensures the pinning effect of the ceramic oxide, giving the material good resistance to arc erosion. Attached Figure Description

[0027] Figure 1 The images are SEM images (20000×) of Ag-Sn(12.5) alloy powder before and after oxidation in Example 1 of this invention; where (a) is before oxidation and (b) is after oxidation.

[0028] Figure 2 The image shows the particle size distribution of Ag-Sn(12.5) alloy powder before and after oxidation in Example 1 of this invention; where (a) is before oxidation and (b) is after oxidation.

[0029] Figure 3 SEM images of AgSnO2(8) powder prepared in Example 1, Comparative Example 1-1 and Comparative Example 1-2 of the present invention are shown; wherein, (a) is Example 1, (b) is Comparative Example 1-1 and (c) is Comparative Example 1-2. Detailed Implementation

[0030] To better explain the technical solution of the present invention, the present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0031] Example 1: Preparation of AgSnO2(8)

[0032] 1) Weigh Ag ingots and Sn ingots at a weight ratio of 87.5:12.5, prepare Ag-Sn alloy powder by atomization, and pass through a 500-mesh sieve to obtain Ag-Sn(12.5) alloy powder with a particle size D90≤30μm and D50 in the range of 10~15μm (e.g. Figure 1 (a) Figure 2 As shown in (a), the mass percentage of Sn is 12.5%;

[0033] 2) The obtained Ag-Sn alloy powder was pre-oxidized for 72 hours at a pressure of 30 atm and a temperature of 400℃ to obtain AgSnO2 master powder with a particle size D50 of 12-17 μm. The SnO2 precipitates in the obtained AgSnO2 master powder reached the nanoscale (e.g., ...). Figure 1 (b) Figure 2 (b) is shown);

[0034] 3) Weigh the AgSnO2 mother powder and silver nitrate prepared in step 2) in a weight ratio of 50:78.74 (i.e., AgSnO2 mother powder: pure silver = 50:50, weight ratio), and then weigh sodium hydroxide equivalent to 1.2 times the molar amount of silver nitrate for later use;

[0035] 4) Weigh out sodium hydroxide and silver nitrate and prepare sodium hydroxide solution and silver nitrate solution respectively with water, wherein the concentration of sodium hydroxide solution is 5 mol / L and the concentration of silver nitrate solution is 3 mol / L;

[0036] 5) Add the AgSnO2 mother powder weighed in step 3) to the prepared sodium hydroxide solution and stir evenly to obtain an alkaline suspension; then add the prepared silver nitrate solution to the above alkaline suspension and stir for 2.5 h to obtain AgSnO2(8) powder with a pure silver layer on the surface of the AgSnO2 mother powder (e.g. Figure 3 (a) As shown, the particle size D50 of the obtained AgSnO2(8) powder is 14-20 μm;

[0037] 6) The obtained AgSnO2(8) powder is pressed into a blank under isostatic pressure of 100MPa; the obtained blank is sintered at 930℃ for 6h in air atmosphere to obtain AgSnO2(8) ingot blank; the obtained ingot blank is extruded at 850℃ (extrusion ratio of 200) into plate or wire, and then processed into AgSnO2(8) sheet or rivet contact.

[0038] Comparative Example 1-1: Preparation of AgSnO2(8)

[0039] Repeat Example 1, except that steps 1) and 3) are performed as follows:

[0040] 1) Weigh Ag ingots and Sn ingots at a weight ratio of 91.4:8.6, prepare Ag-Sn alloy powder by atomization, and pass through a 500-mesh sieve to obtain Ag-Sn(8.6) alloy powder with a particle size D90≤30μm and D50 in 10~15μm, wherein the mass percentage of Sn is 8.6%.

[0041] 3) Weigh the AgSnO2 mother powder and silver nitrate prepared in step 2) in a weight ratio of 75:39.37 (i.e., AgSnO2 mother powder: pure silver = 75:25, weight ratio), and then weigh sodium hydroxide equivalent to 1.2 times the molar amount of silver nitrate for later use.

[0042] The AgSnO2 masterbatch prepared in this comparative example has a pure silver coating on its surface. The AgSnO2(8) powder is as follows: Figure 3 As shown in (b).

[0043] Comparative Examples 1-2: Preparation of AgSnO2(8)

[0044] Repeat Example 1, except that steps 1) and 3) are performed as follows:

[0045] 1) Weigh Ag ingots and Sn ingots in a weight ratio of 73:27, prepare Ag-Sn alloy powder by atomization, and pass through a 500-mesh sieve to obtain Ag-Sn(27) alloy powder with a particle size D90≤30μm and D50 in 10~15μm, wherein the mass percentage of Sn is 27%.

[0046] 3) Weigh the AgSnO2 mother powder and silver nitrate prepared in step 2) in a weight ratio of 25:118.11 (i.e., AgSnO2 mother powder: pure silver = 25:75, weight ratio), and then weigh sodium hydroxide equivalent to 1.2 times the molar amount of silver nitrate for later use.

[0047] The AgSnO2 masterbatch prepared in this comparative example has a pure silver coating on its surface. The AgSnO2(8) powder is as follows: Figure 3 As shown in (c).

[0048] Example 2: Preparation of AgSnO2(10)

[0049] 1) Weigh Ag ingots and Sn ingots in a ratio of 83.5:16.5, prepare Ag-Sn alloy powder by atomization, and pass through a 500-mesh sieve to obtain Ag-Sn(16.5) alloy powder with a particle size D90≤30μm and D50 in 10~15μm, wherein the mass percentage of Sn is 16.5%;

[0050] 2) The obtained Ag-Sn alloy powder was pre-oxidized for 72 hours under a pressure of 30 atmospheres and a temperature of 400℃ to obtain AgSnO2 master powder with a particle size D50 of 12 to 17 μm. The SnO2 precipitate particle size in the obtained AgSnO2 master powder reached the nanoscale.

[0051] 3) Weigh the AgSnO2 mother powder and silver nitrate prepared in step 2) in a weight ratio of 50:78.74 (i.e., AgSnO2 mother powder: pure silver = 50:50, weight ratio), and then weigh sodium hydroxide equivalent to 1.2 times the molar amount of silver nitrate for later use;

[0052] 4) Weigh out sodium hydroxide and silver nitrate and prepare sodium hydroxide solution and silver nitrate solution respectively with water, wherein the concentration of sodium hydroxide solution is 5 mol / L and the concentration of silver nitrate solution is 3 mol / L;

[0053] 5) The AgSnO2 mother powder weighed in step 3) is added to the prepared sodium hydroxide solution and stirred evenly to obtain an alkaline suspension; then the prepared silver nitrate solution is added to the above alkaline suspension and stirred for 2.5 h to obtain AgSnO2(10) powder with a pure silver layer on the surface of the AgSnO2 mother powder. The particle size D50 of the obtained AgSnO2(10) powder is 14-20 μm.

[0054] 6) The obtained AgSnO2(10) powder is pressed into a blank under isostatic pressure of 100MPa; the obtained blank is sintered at 930℃ for 6h in air atmosphere to obtain AgSnO2(10) ingot blank; the obtained ingot blank is extruded at 850℃ (extrusion ratio of 200) into plate or wire, and then processed into AgSnO2(10) sheet or rivet contact.

[0055] Example 3: Preparation of AgSnO2(12)

[0056] 1) Weigh Ag ingots, Sn ingots and Bi ingots in a ratio of 79.5:18.4:2.1, prepare Ag-Sn-Bi alloy powder by atomization, and pass through a 500-mesh sieve to obtain Ag-Sn(18.4)-Bi(2.1) alloy powder with a particle size D90≤30μm and D50 in 10~15μm, wherein the mass percentage of Sn is 18.4%;

[0057] 2) The obtained Ag-Sn-Bi alloy powder was pre-oxidized for 72 hours under a pressure of 30 atmospheres and a temperature of 400℃ to obtain AgSnO2T master powder with additives, and the powder particle size D50 was 12-17μm. The Bi element content in the AgSnO2T master powder was 1%, and the SnO2 precipitate particle size in the obtained AgSnO2T master powder reached the nanoscale.

[0058] 3) Weigh the AgSnO2 mother powder and silver nitrate prepared in step 2) in a weight ratio of 50:78.74 (i.e., AgSnO2 mother powder: pure silver = 50:50, weight ratio), and then weigh sodium hydroxide equivalent to 1.2 times the molar amount of silver nitrate for later use;

[0059] 4) Weigh out sodium hydroxide and silver nitrate and prepare sodium hydroxide solution and silver nitrate solution respectively with water, wherein the concentration of sodium hydroxide solution is 5 mol / L and the concentration of silver nitrate solution is 3 mol / L;

[0060] 5) Add the AgSnO2T mother powder weighed in step 3) to the prepared sodium hydroxide solution and stir evenly to obtain an alkaline suspension; then add the prepared silver nitrate solution to the above alkaline suspension and stir for 2.5 h to obtain AgSnO2(12)T powder with a pure silver layer on the surface of the AgSnO2T mother powder. The particle size D50 of the obtained AgSnO2(12)T powder is 14-20 μm.

[0061] 6) The obtained AgSnO2(12)T powder is pressed into a blank under isostatic pressure of 100MPa; the obtained blank is sintered at 930℃ for 6h in air atmosphere to obtain AgSnO2(12)T ingot blank; the obtained ingot blank is extruded at 850℃ (extrusion ratio of 200) into plate or wire, and then processed into AgSnO2(12)T sheet or rivet contact.

[0062] The plasticity and arc erosion resistance of the contact materials prepared in Examples 1-3, Comparative Example 1-1, and Comparative Example 1-2 were tested, and the results are shown in Tables 1 and 3 below.

[0063] Table 1 Mechanical properties of AgSnO2 materials prepared in each example

[0064]

[0065] The AgSnO2(8) wire prepared according to the method described in Example 1 of this invention and commercial AgSnO2(8) wire were processed into 3×0.8+1.5×1.5R8 and 3×0.8+1.5×1.5F rivet contacts, which were respectively used as dynamic and static contacts and assembled on a simulated electrical performance testing machine for relay simulated electrical life test. The test conditions are shown in Table 2 and the test results are shown in Table 3.

[0066] Table 2 Simulated Electrical Performance Test Conditions

[0067]

[0068] Table 3 Results of Simulated Electrical Performance Tests

[0069]

[0070] As shown in Table 3, Example 1 has the best performance, while Comparative Examples 1-2 have the worst. The main reason for the poor electrical life of Comparative Examples 1-2 is that the masterbatch is coated with more pure silver, which causes local pure silver segregation and slightly poor oxide dispersion. This results in premature welding failure of electrical components during the electrical life test.

Claims

1. A method for preparing a silver-tin oxide electrical contact material with good plasticity and resistance to arc erosion, comprising the following steps: 1) Ag-Sn alloy powder with particle size D90≤30μm and D50 in 10~15μm is prepared by processing Ag ingot, Sn ingot and X ingot; wherein, the X element is one or more of Bi, Cu, In, Sb and Zn. 2) The obtained Ag-Sn alloy powder was prepared by powder alloy pre-oxidation under low temperature and high oxygen pressure conditions to obtain AgSnO2 master powder with a particle size D50 of 12~17μm. The SnO2 precipitate particle size in the obtained AgSnO2 master powder reached the nanoscale. The low temperature and high oxygen pressure refers to the conditions of pressure of 20~40 atmospheres and oxidation temperature ≤600℃. 3) Calculate the required amounts of Ag, Sn, and X elements according to the required composition ratio of the materials to be prepared, and weigh them for later use. When weighing, Sn and X elements are weighed in the form of AgSnO2 master powder, and Ag elements are weighed in two forms: a portion is weighed in the form of silver nitrate, and the remainder is weighed in the form of AgSnO2 master powder. The silver weighed in the form of silver nitrate accounts for 30-70 wt% of the total weight of Ag elements. 4) Weigh out an excess of alkaline substance relative to the amount of silver nitrate, and then use water to prepare alkaline solution and silver nitrate solution respectively. 5) Add the weighed AgSnO2 mother powder to an alkaline solution to obtain an alkaline suspension; then add the prepared silver nitrate solution to the alkaline suspension to react until all the silver ions in the silver nitrate solution are replaced, and AgSnO2 powder with a pure silver layer on the surface of the AgSnO2 mother powder is obtained. 6) The obtained AgSnO2 powder is subjected to isostatic pressing, sintering and extrusion processes to obtain silver tin oxide electrical contact material with good plasticity and resistance to electric arc erosion.

2. The preparation method according to claim 1, characterized in that, In step 3), the silver weighed in the form of silver nitrate accounts for 40-60 wt% of the total weight of Ag element.

3. The preparation method according to claim 1, characterized in that, In step 2), the oxidation temperature is 350~450℃.

4. The preparation method according to claim 1, characterized in that, In step 4), the molar ratio of silver nitrate to alkaline substance is 1:1.1~1.

3.

5. The preparation method according to claim 1, characterized in that, In step 4), the alkaline substance is sodium hydroxide or ammonia.

6. The preparation method according to claim 1, characterized in that, In step 4), the concentration of the alkaline solution is 4~6 mol / L, and the concentration of the silver nitrate solution is 2~4 mol / L.

7. The preparation method according to claim 1, characterized in that, In step 5), the reaction time is ≥2h.

8. The preparation method according to any one of claims 1 to 7, characterized in that, In step 3), the content of tin oxide in the silver tin oxide contact material to be prepared is 5~15wt%, the content of element X as its oxide is 0~2wt%, and the balance is Ag.

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