Method for preparing silver tin oxide relay contact material by composite powder

Abstract

The application discloses a method for preparing a silver tin oxide relay contact material by a composite powder mixing method, and comprises the following steps: a powder mixing step 1: tin oxide is added into a powder mixer 1, and then part of silver powder is added, wherein the total amount of the silver powder is 1 / 3 of the total amount of the silver powder, the added mass of the silver powder is less than or equal to 1 / 2 of the total amount of the silver powder, the powder is mixed, the powder mixing time is 1.5-2 hours, and the rotating speed of the powder mixer 1 is 100-120 revolutions per minute; a powder mixing step 2: the mixed material in the powder mixer 1 is taken out, and then is added into a powder mixer 2, the remaining silver powder is also added, the powder is mixed, the powder mixing time is 2.5-3 hours, and the rotating speed of the powder mixer is 150-180 revolutions per minute. The composite powder mixing method can effectively solve the oxidation process problem of the silver tin oxide and the agglomeration problem of the tin oxide in the silver base, and can make the microstructure of the silver tin oxide fully uniform. According to a metallographic phase diagram of the silver tin oxide contact material, it can be known that the microstructure of the silver tin oxide is uniform, and almost no defect structure exists; and the physical performance and the electrical life of the contact material can all reach the design standard.

Description

Technical Field

[0001] This invention relates to a method for preparing relay contact materials, and more particularly to a method for preparing silver tin oxide relay contact materials by composite powder mixing. Background Technology

[0002] Contact materials play a crucial role in electrical equipment, directly affecting its conductivity, resistance to arc erosion, and resistance to oxidation and welding. Silver oxide (STI) contacts are critical contact elements in relays, electrical switches, and other electrical devices, primarily responsible for connecting and disconnecting circuits and load current. The quality of STI contacts directly impacts the lifespan of relays and the safety and reliability of electrical equipment. Adding tin oxide as a reinforcing phase to the silver matrix effectively enhances the arc erosion resistance and resistance to welding of STI contact materials. Therefore, STI electrical contact materials are metal composite materials in which tin oxide is uniformly distributed as a dispersed reinforcing phase within a silver matrix.

[0003] As electrical equipment develops towards miniaturization and high performance, the requirements for contact materials are also increasing. Domestic and international scholars typically use the internal oxidation method to prepare silver-tin oxide electrical contact materials. However, the traditional internal oxidation process has some problems, such as uneven oxidation composition, incomplete oxidation, and poor machinability. Because the dense tin oxide film during the oxidation process of silver-tin alloys hinders further oxidation, and tin entering the silver alloy lattice severely impedes oxygen atom diffusion, indium must be added to increase the internal oxidation rate of the silver-tin alloy during the internal oxidation method. The internal oxidation method involves oxidizing the silver-tin alloy at high temperature under specific oxygen pressure conditions. Detailed process flow is as follows... Figure 1 As shown.

[0004] The internal oxidation method for preparing silver tin oxide contact materials has extremely stringent requirements regarding oxygen pressure, oxidation temperature, and oxidation time. Insufficient oxidation will result in a large number of tin atoms in the microstructure of silver tin oxide remaining unoxidized, failing to oxidize into tin oxide for dispersion reinforcement. Excessive oxidation, on the other hand, will cause cracks or even holes in the central part of the silver tin oxide material, severely affecting the contact performance and electrical lifespan of the silver tin oxide contacts. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing silver tin oxide relay contact material by composite powder mixing, which can effectively solve the oxidation process problem of silver tin oxide and the agglomeration problem of tin oxide in silver matrix, so as to make the microstructure of silver tin oxide uniform.

[0006] The technical solution adopted by the present invention to solve its technical problem is as follows:

[0007] A method for preparing silver-tin oxide relay contact material by composite powder mixing includes the following steps:

[0008] Powder mixing step 1: Add all the tin oxide to powder mixer 1, then add some silver powder, with the total amount of silver powder ≤ 1 / 3 of the total amount of silver powder added ≤ 1 / 2 of the total amount of silver powder. Mix the powder for 1.5 to 2 hours, and the speed of powder mixer 1 is 100 to 120 rpm.

[0009] Mixing step 2: Take out all the mixed materials from mixer 1 and add them all to mixer 2. Add all the remaining silver powder as well. Mix the powder for 2.5 to 3 hours at a speed of 150 to 180 revolutions per minute.

[0010] This invention employs a two-stage powder mixing process to ensure that the silver powder and tin oxide powder are fully and uniformly mixed.

[0011] Furthermore, mixer 1 is preferably a dual-motion mixer. Mixer 2 is preferably a plow-type mixer.

[0012] Mixer 1 is preferably a dual-motion mixer. This mixer utilizes the eccentric rotation of the hopper and the high-speed stirring motion of the full-size rotating blades to cause the powder to tumble and convection within the hopper space, achieving both "uniformity in large areas" and "thorough mixing in small areas." This solves the mixing problem between tin oxide ultrafine powder and silver powder. Mixer 2 is preferably a plow-type mixer. The high-speed rotation of the plow blades and the discrete stirring greatly increase the mixing speed, solving the workability and uniformity issues of the tin oxide powder-silver powder mixture and the remaining silver powder material, preventing segregation.

[0013] If too little silver powder is added to mixer 1, the workability and uniformity of the tin oxide powder-silver powder mixture and the remaining silver powder material in mixer 2 will be affected, leading to segregation. If too much silver powder is added to mixer 1, the tin oxide ultrafine powder will not be able to mix sufficiently with the silver powder.

[0014] Excessive mixing time will increase energy consumption, while insufficient mixing time will result in uneven mixing. Excessive mixer speed will increase energy consumption and maintenance costs, while insufficient mixer speed will lead to uneven mixing.

[0015] Specifically, the following steps are included:

[0016] ①Powder drying: Dry the silver powder and tin oxide powder;

[0017] Furthermore, in step ①, the mass percentage of silver powder is 87-89%, and the mass percentage of tin oxide powder is 11-13%. The drying temperature is 80-90℃, and the drying time is 2-3 hours.

[0018] ② Powder mixing step 1: Use a dual-motion powder mixer to mix the powder. Add all the tin oxide to the mixing tank, and then add some silver powder. The total amount of silver powder should be 1 / 3 ≤ the mass of silver powder added ≤ 1 / 2 of the total amount of silver powder. The mixing time is 1.5 to 2 hours, and the speed of the powder mixer is 100 to 120 rpm.

[0019] ③ Powder mixing step 2: Use a plow-type powder mixer to mix the powder. Take out all the mixed materials from the double motion powder mixer and add them all into the plow-type powder mixer. Add all the remaining silver powder as well. Mix for 2.5 to 3 hours and the powder mixer speed is 150 to 180 rpm to obtain mixed powder.

[0020] ④ Isostatic pressing: The mixed powder obtained in step ③ isostatically pressed to obtain silver tin oxide mixed powder ingots;

[0021] Furthermore, in step ④, the isostatic pressure is 15–20 MPa, and the pressure holding time is 15–20 seconds.

[0022] ⑤ Sintering: The silver tin oxide mixed powder ingot pressed in step ④ is sintered in air to obtain silver tin oxide alloy ingot, i.e. silver tin oxide blank material.

[0023] Furthermore, in step ⑤, the silver-tin oxide mixed powder ingot is first heated to 300-500℃, then heated to 850-900℃, and held at that temperature for ≥2 hours.

[0024] The silver tin oxide preform material obtained by this invention can be used to prepare wires and sheets. The specific steps are as follows:

[0025] Option 1: Preparation of silver tin oxide wire

[0026] ⑥ Extrusion: The sintered silver-tin oxide alloy ingot is extruded to obtain silver-tin oxide coarse wire;

[0027] Furthermore, in step ⑥, a 1250-ton extrusion press is preferably used for extrusion.

[0028] Furthermore, in step ⑥, the specific extrusion operation is as follows: the extrusion cylinder is heated to 380-420℃ (preferably 400℃), the extrusion die is Ф6.0mm, the extrusion speed is 1.5~2.5mm / S, and water cooling is applied.

[0029] ⑦ Wire drawing: The silver tin oxide coarse wire obtained in step ⑥ is drawn into wire to obtain silver tin oxide relay contact wire material.

[0030] Further, in step ⑦, wire drawing, the following wire drawing die is selected: Ф6.0 / annealed / Ф5.6 / annealed / Ф5.2 / annealed / Ф4.8 / annealed / Ф4.4 / annealed / Ф4.0 / annealed / Ф3.6 / annealed / Ф3.2 / annealed / Ф2.9 / annealed / Ф2.6 / annealed / Ф2.38–0.02mm.

[0031] Furthermore, in step ⑦, during the wire drawing process, the annealing temperature is 550±10℃; the holding time is 0.8-1.2 hours (preferably 1 hour). The wire is removed directly from the furnace under air atmosphere. The process involves one wire drawing and one annealing cycle.

[0032] Option 2: Preparation of silver tin oxide sheets

[0033] ⑥ Extrusion: The sintered silver-tin oxide alloy ingot is extruded to obtain silver-tin oxide sheets;

[0034] Furthermore, in step ⑥, a 1250-ton extrusion press is preferably used for extrusion.

[0035] Furthermore, in step ⑥, the specific extrusion operation is as follows: the extrusion cylinder is heated to 380-420℃ (preferably 400℃), the extrusion die is 5*72mm, and the extrusion speed is 1.5~2.5mm / S.

[0036] ⑦ Composite peripheral argon arc welding: The silver tin oxide sheet extruded by the extruder is combined with a pure silver sheet of the same size and composite peripheral argon arc welding is used to obtain a silver / silver tin oxide composite plate after argon arc welding.

[0037] Furthermore, in step ⑦, the composite surface is cleaned with non-woven fabric soaked in ethanol before welding, and then welded on both sides after drying.

[0038] ⑧ Hot rolling: The silver / silver tin oxide composite plate after argon arc welding is hot rolled;

[0039] Furthermore, in step ⑧, hot rolling is preferably carried out in a 15KW muffle furnace.

[0040] Furthermore, in step ⑧, the hot rolling temperature is 750–800℃, and the holding time is 1.5–2 hours.

[0041] Furthermore, in step ⑧, the hot rolling reduction is greater than 50% to ensure the bonding strength of the silver / silver tin oxide composite plate.

[0042] ⑨ Cold rolling: The hot-rolled silver / silver tin oxide composite plate is cold-rolled according to the dimensional requirements;

[0043] ⑩ Annealing: Anneal the cold-rolled silver / silver tin oxide composite plate to obtain silver tin oxide sheet.

[0044] Furthermore, in step 10, annealing is preferably carried out in a 15KW muffle furnace.

[0045] Furthermore, in step 10, the annealing operation is as follows: heat to 550-600℃, hold in a nitrogen atmosphere for 0.8-1.2 hours (preferably 1 hour), and air-cool to ≤80℃ before removing from the furnace.

[0046] This invention employs a composite powder mixing method, which effectively solves the oxidation process problems of silver tin oxide and the agglomeration problem of tin oxide in the silver matrix, resulting in a sufficiently uniform microstructure of silver tin oxide. Metallographic images of the silver tin oxide contact material prepared by this invention show a uniform microstructure with almost no defects; furthermore, the physical properties and electrical life of the contact material meet design standards.

[0047] This invention employs powder metallurgy to prepare silver-tin oxide electrical contact materials. The distribution and particle size of tin oxide in the mixed powder determine the performance of the silver-tin oxide contacts. Due to the small size of the tin oxide particles, traditional mechanical mixing can cause tin oxide agglomeration. Tin oxide agglomeration leads to a large number of defects in the microstructure of the material, severely affecting the performance of the silver-tin oxide contacts. Therefore, this invention can solve the problem of tin oxide agglomeration in the silver matrix, resulting in a sufficiently uniform microstructure of silver-tin oxide.

[0048] This invention employs powder metallurgy, directly using tin oxide powder as raw material, eliminating the need for tin atom oxidation, and effectively solving the oxidation process problem of silver tin oxide contact materials. Attached Figure Description

[0049] Figure 1 A flowchart of the process for preparing silver tin oxide contact materials using the internal oxidation method in the prior art;

[0050] Figure 2 The image shows the metallographic structure of the silver-tin oxide relay contact material obtained in Example 1 of this invention (50X); 50X is a magnified image of 50 times; the same applies below.

[0051] Figure 3 Metallographic structure (200X) of the silver-tin oxide relay contact material obtained in Example 1 of the present invention;

[0052] Figure 4 The metallographic structure (50X) of the silver-tin oxide relay contact material obtained in Comparative Example 1 of this invention is shown.

[0053] Figure 5 The metallographic structure (200X) of the silver-tin oxide relay contact material obtained in Comparative Example 1 of this invention is shown.

[0054] Figure 6 The metallographic structure (50X) of the silver-tin oxide relay contact material obtained in Comparative Example 2 of this invention is shown.

[0055] Figure 7 The metallographic structure of the silver-tin oxide relay contact material obtained in Comparative Example 2 of this invention is shown in the image (200X). Detailed Implementation

[0056] The present invention will be further described in detail below with reference to specific embodiments.

[0057] Example 1

[0058] The method for preparing silver-tin oxide relay contact material by composite powder mixing in this embodiment includes the following steps:

[0059] ①Powder drying: Dry the silver powder and tin oxide powder;

[0060] In step ①, the mass percentage of silver powder is 88%, and the mass percentage of tin oxide powder is 12%. The drying temperature is 85℃, and the drying time is 2 hours.

[0061] ② Powder mixing step 1: Use a dual-motion powder mixer to mix the powder. Add all the tin oxide to the mixing tank, and then add some silver powder. The amount of silver powder added is 1 / 2 of the total mass of silver powder. The mixing time is 2 hours and the speed of the powder mixer is 100 rpm.

[0062] ③ Powder mixing step 2: Use a plow-type powder mixer to mix the powder. Take out all the mixed materials from the double motion powder mixer and add them all into the plow-type powder mixer. Add all the remaining silver powder as well. Mix for 2.5 hours and the powder mixer speed is 150 rpm to obtain mixed powder.

[0063] ④ Isostatic pressing: The mixed powder obtained in step ③ isostatically pressed to obtain silver tin oxide mixed powder ingots;

[0064] In step ④, the isostatic pressure is 15 MPa, and the pressure holding time is 20 seconds.

[0065] ⑤ Sintering: The silver tin oxide mixed powder ingot pressed in step ④ is sintered in air to obtain silver tin oxide alloy ingot, i.e. silver tin oxide blank material.

[0066] In step ⑤, the silver-tin oxide mixed powder ingot is first heated to 500°C, then heated to 900°C and held at that temperature for 2 hours.

[0067] ⑥ Extrusion: The sintered silver-tin oxide alloy ingot is extruded to obtain silver-tin oxide coarse wire;

[0068] In step ⑥, the extrusion is performed using a 1250-ton extruder.

[0069] In step ⑥, the specific extrusion operation is as follows: the extrusion cylinder is heated to 400℃, the extrusion die is Ф6.0mm, the extrusion speed is 1.5mm / S, and water cooling is used.

[0070] ⑦ Wire drawing: The silver tin oxide coarse wire obtained in step ⑥ is drawn into wire to obtain silver tin oxide relay contact wire material.

[0071] Step 7: Wire drawing. Select the following wire drawing die: Ф6.0 / annealed / Ф5.6 / annealed / Ф5.2 / annealed / Ф4.8 / annealed / Ф4.4 / annealed / Ф4.0 / annealed / Ф3.6 / annealed / Ф3.2 / annealed / Ф2.9 / annealed / Ф2.6 / annealed / Ф2.38–0.02mm.

[0072] In step ⑦, during the wire drawing process, the annealing temperature is 550±10℃; the holding time is 1 hour. The wire is removed directly from the oven under air atmosphere. The process involves one wire drawing and one annealing cycle.

[0073] The physical properties and electrical life performance of the silver tin oxide contact wire material obtained in Example 1 were tested, and the test results are shown in Table 1 and Table 2.

[0074] The testing method standards are: JB / T 8444-2015, GB / T 20235-2006, and GB / T 14048.4-2020.

[0075] As shown in Tables 1 and 2, the physical properties and electrical life of the silver-zinc oxide contact material obtained in Example 1 of this invention can meet the design standards.

[0076] Table 1

[0077] Physical properties of silver tin oxide

[0078]

[0079] Table 2

[0080] 32A relay temperature rise and electrical life test data

[0081]

[0082] The test results above show that the composite powder mixing method used in this invention can effectively solve the problem of tin oxide agglomeration in the silver matrix, making the microstructure of silver tin oxide fully uniform, so that the physical properties and electrical life of the resulting silver zinc oxide contact material can meet the design standards.

[0083] Figure 2 The image shows the metallographic structure of the silver-tin oxide relay contact material obtained in Example 1 of this invention (50X); 50X is a magnified image of 50 times; the same applies below.

[0084] Figure 3 The metallographic structure (200X) of the silver-tin oxide relay contact material obtained in Example 1 of the present invention is shown.

[0085] Metallographic testing was performed on the silver tin oxide contact material obtained in Example 1. The metallographic image of the silver tin oxide contact material prepared in this example shows that the microstructure of silver tin oxide is uniform and there are almost no defective structures. Furthermore, the physical properties and electrical life of the contact material can meet the design standards.

[0086] Example 2

[0087] The method for preparing silver-tin oxide relay contact material by composite powder mixing in this embodiment includes the following steps:

[0088] ①Powder drying: Dry the silver powder and tin oxide powder;

[0089] In step ①, the mass percentage of silver powder is 87%, and the mass percentage of tin oxide powder is 13%. The drying temperature is 90℃, and the drying time is 2 hours.

[0090] ② Powder mixing step 1: Use a dual-motion powder mixer to mix the powder. Add all the tin oxide to the mixing tank, then add some silver powder. The mass of the silver powder added should be equivalent to 1 / 3 of the total mass of silver powder. Mix for 2 hours and the speed of the powder mixer should be 100 rpm.

[0091] ③ Powder mixing step 2: Use a plow-type powder mixer to mix the powder. Take out all the mixed materials from the double motion powder mixer and add them all into the plow-type powder mixer. Add all the remaining silver powder as well. Mix for 2.5 hours and the powder mixer speed is 180 rpm to obtain mixed powder.

[0092] ④ Isostatic pressing: The mixed powder obtained in step ③ isostatically pressed to obtain silver tin oxide mixed powder ingots;

[0093] In step ④, the isostatic pressure is 15 MPa, and the pressure holding time is 15 seconds.

[0094] ⑤ Sintering: The silver tin oxide mixed powder ingot pressed in step ④ is sintered in air to obtain silver tin oxide alloy ingot, i.e. silver tin oxide blank material.

[0095] In step ⑤, the silver-tin oxide mixed powder ingot is first heated to 300°C, then heated to 900°C and held for 3 hours.

[0096] ⑥ Extrusion: The sintered silver-tin oxide alloy ingot is extruded to obtain silver-tin oxide sheets;

[0097] In step ⑥, a 1250-ton extrusion press is preferably used for extrusion.

[0098] In step ⑥, the specific extrusion operation is as follows: the extrusion cylinder is heated to 400℃, the extrusion die is 5*72mm, and the extrusion speed is 1.5mm / S.

[0099] ⑦ Composite peripheral argon arc welding: The silver tin oxide sheet extruded by the extruder is combined with a pure silver sheet of the same size and composite peripheral argon arc welding is used to obtain a silver / silver tin oxide composite plate after argon arc welding.

[0100] In step ⑦, before welding, the composite surface is cleaned with non-woven fabric soaked in ethanol, and then welded on both sides after drying.

[0101] ⑧ Hot rolling: The silver / silver tin oxide composite plate after argon arc welding is hot rolled;

[0102] In step ⑧, hot rolling is carried out in a 15KW muffle furnace.

[0103] In step ⑧, the hot rolling temperature is 800℃, and the holding time is 1.5 hours.

[0104] In step ⑧, the hot rolling reduction is 55% to ensure the bonding strength of the silver / silver tin oxide composite plate.

[0105] ⑨ Cold rolling: The hot-rolled silver / silver tin oxide composite plate is cold-rolled according to the dimensional requirements;

[0106] ⑩ Annealing: Anneal the cold-rolled silver / silver tin oxide composite plate to obtain silver tin oxide sheet.

[0107] In step 10, annealing is carried out in a 15KW muffle furnace.

[0108] In step 10, the annealing process is as follows: heat to 600℃, hold in a nitrogen atmosphere for 1 hour, and air-cool to 80℃ before removing from the furnace.

[0109] This embodiment employs a composite powder mixing method, which effectively solves the problem of tin oxide agglomeration in the silver matrix, resulting in a uniform microstructure of silver tin oxide. Metallographic images of the silver tin oxide contact material prepared in this embodiment show a uniform microstructure with almost no defects; furthermore, the physical properties and electrical life of the contact material meet design standards.

[0110] Example 3

[0111] The method for preparing silver-tin oxide relay contact material by composite powder mixing in this embodiment includes the following steps:

[0112] ①Powder drying: Dry the silver powder and tin oxide powder;

[0113] In step ①, the mass percentage of silver powder is 89%, and the mass percentage of tin oxide powder is 11%. The drying temperature is 90℃, and the drying time is 3 hours.

[0114] ② Powder mixing step 1: Use a dual-motion powder mixer to mix the powder. Add all the tin oxide to the mixing tank, then add some silver powder. The mass of the silver powder added should be equivalent to 1 / 4 of the total silver powder. Mix for 2 hours and the speed of the powder mixer should be 120 rpm.

[0115] ③ Powder mixing step 2: Use a plow-type powder mixer to mix the powder. Take out all the mixed materials from the double motion powder mixer and add them all into the plow-type powder mixer. Add all the remaining silver powder as well. Mix for 3 hours and the powder mixer speed is 150 rpm to obtain mixed powder.

[0116] ④ Isostatic pressing: The mixed powder obtained in step ③ isostatically pressed to obtain silver tin oxide mixed powder ingots;

[0117] In step ④, the isostatic pressure is 20 MPa, and the pressure holding time is 15 seconds.

[0118] ⑤ Sintering: The silver tin oxide mixed powder ingot pressed in step ④ is sintered in air to obtain silver tin oxide alloy ingot, i.e. silver tin oxide blank material.

[0119] In step ⑤, the silver oxide tin mixed powder ingot is first heated to 500℃, then heated to 850℃ and held for 2 hours.

[0120] ⑥ Extrusion: The sintered silver-tin oxide alloy ingot is extruded to obtain silver-tin oxide coarse wire;

[0121] In step ⑥, the extrusion is performed using a 1250-ton extruder.

[0122] In step ⑥, the specific extrusion operation is as follows: the extrusion cylinder is heated to 420℃, the extrusion die is Ф6.0mm, the extrusion speed is 2.5mm / S, and water cooling is used.

[0123] ⑦ Wire drawing: The silver tin oxide coarse wire obtained in step ⑥ is drawn into wire to obtain silver tin oxide relay contact wire material.

[0124] Step 7: Wire drawing. Select the following wire drawing die: Ф6.0 / annealed / Ф5.6 / annealed / Ф5.2 / annealed / Ф4.8 / annealed / Ф4.4 / annealed / Ф4.0 / annealed / Ф3.6 / annealed / Ф3.2 / annealed / Ф2.9 / annealed / Ф2.6 / annealed / Ф2.38–0.02mm.

[0125] In step ⑦, during the wire drawing process, the annealing temperature is 550±10℃; the holding time is 1.2 hours. The wire is removed directly from the oven under air atmosphere. The process involves one wire drawing and one annealing cycle.

[0126] This embodiment employs a composite powder mixing method, which effectively solves the problem of tin oxide agglomeration in the silver matrix, resulting in a uniform microstructure of silver tin oxide. Metallographic images of the silver tin oxide contact material prepared in this embodiment show a uniform microstructure with almost no defects; furthermore, the physical properties and electrical life of the contact material meet design standards.

[0127] Comparative Example 1

[0128] This comparative example is modified except for steps ② and ③: use a dual-motion powder mixer to mix the powder, add all the tin oxide to the mixing tank, then add all the silver powder, mix for 2 hours, and the powder mixer speed is 100 rpm to obtain mixed powder;

[0129] The remaining operating steps and parameters are the same as in Example 1.

[0130] The physical properties and electrical life performance of the silver tin oxide contact wire material obtained in Comparative Example 1 were tested, and the test results are shown in Tables 3 and 4.

[0131] The testing method standards are: JB / T 8444-2015, GB / T 20235-2006, and GB / T 14048.4-2020.

[0132] As shown in Tables 3 and 4, the physical properties and electrical life of the silver-zinc oxide contact material obtained in Comparative Example 1 of this invention failed to meet the design standards.

[0133] The test results above show that the single-mixing method used in this comparative example cannot solve the problem of tin oxide agglomeration in the silver matrix, resulting in an uneven microstructure of tin oxide silver. Consequently, the physical properties and electrical life of the obtained zinc oxide silver contact material failed to meet the design standards.

[0134] Figure 4 The metallographic structure (50X) of the silver-tin oxide relay contact material obtained in Comparative Example 1 of this invention is shown.

[0135] Figure 5 The metallographic structure (200X) of the silver-tin oxide relay contact material obtained in Comparative Example 1 of this invention is shown.

[0136] Metallographic analysis was performed on the silver tin oxide contact material obtained in Comparative Example 1. The metallographic image of the silver tin oxide contact material prepared in this comparative example shows that the microstructure of silver tin oxide is uneven and there are many defects. Furthermore, the physical properties and electrical life of the contact material tested both failed to meet the design standards.

[0137] Table 3

[0138] Physical properties of silver tin oxide

[0139]

[0140] Table 4

[0141] 32A relay temperature rise and electrical life test data

[0142]

[0143] Comparative Example 2

[0144] This comparative example is modified except for steps ② and ③: use a plow-type powder mixer to mix the powder, add all the tin oxide to the mixing tank, then add all the silver powder, mix for 2.5 hours, and the powder mixer speed is 150 rpm to obtain mixed powder;

[0145] The remaining operating steps and parameters are the same as in Example 1.

[0146] The physical properties and electrical life performance of the silver tin oxide contact wire material obtained in Comparative Example 2 were tested, and the test results are shown in Tables 5 and 6.

[0147] The testing method standards are: JB / T 8444-2015, GB / T 20235-2006, and GB / T 14048.4-2020.

[0148] As shown in Tables 5 and 6, the physical properties and electrical life of the silver-zinc oxide contact material obtained in Comparative Example 2 of this invention failed to meet the design standards.

[0149] The test results above show that the single-mixing method used in this comparative example cannot solve the problem of tin oxide agglomeration in the silver matrix. The microstructure of tin oxide is uneven, and thus the physical properties and electrical life of the resulting zinc oxide contact material fail to meet the design standards.

[0150] Figure 6 The metallographic structure (50X) of the silver-tin oxide relay contact material obtained in Comparative Example 2 of this invention is shown.

[0151] Figure 7 The metallographic structure of the silver-tin oxide relay contact material obtained in Comparative Example 2 of this invention is shown in the image (200X).

[0152] Metallographic analysis was performed on the silver tin oxide contact material obtained in Comparative Example 2. The metallographic image of the silver tin oxide contact material prepared in this comparative example shows that the microstructure of silver tin oxide is uneven and there are many defects. Furthermore, the physical properties and electrical life of the contact material tested both failed to meet the design standards.

[0153] Table 5

[0154] Physical properties of silver tin oxide

[0155]

[0156] Table 6

[0157] 32A relay temperature rise and electrical life test data

[0158]

[0159] Through the above tests on the physical properties and electrical life performance of the silver tin oxide relay contact materials obtained in Examples 1-3 and Comparative Examples 1-2, it can be seen that the electrical life of the silver tin oxide relay contact materials obtained in Examples 1-3 of the present invention can meet the design standards. However, Comparative Examples 1-2 use a single-stage powder mixing process, which causes tin oxide to agglomerate in the silver matrix, resulting in an uneven microstructure of the silver tin oxide and affecting the electrical life of the silver zinc oxide AC contactor contact material.

Claims

1. A method for preparing silver-tin oxide relay contact material by composite powder mixing, characterized in that, Includes the following steps: Option 1: Preparation of silver tin oxide wire ①Powder drying; ② Powder mixing step 1: Add all the tin oxide to powder mixer 1, then add some silver powder. The total amount of silver powder should be 1 / 3 ≤ the mass of silver powder added should be ≤ 1 / 2 of the total amount of silver powder. Mix the powder for 1.5 to 2 hours. The speed of powder mixer 1 should be 100 to 120 rpm. ③ Powder mixing step 2: Take out all the mixed materials from powder mixer 1 and add them all to powder mixer 2. Add all the remaining silver powder as well. Mix the powder for 2.5 to 3 hours at a speed of 150 to 180 revolutions per minute. ④Isostatic pressure; ⑤ Sintering; ⑥ Squeeze; ⑦ Drawing the wire yields silver-tin oxide relay contact wire material; Option 2: Preparation of silver tin oxide sheets ①Powder drying; ② Powder mixing step 1: Add all the tin oxide to powder mixer 1, then add some silver powder. The total amount of silver powder should be 1 / 3 ≤ the mass of silver powder added should be ≤ 1 / 2 of the total amount of silver powder. Mix the powder for 1.5 to 2 hours. The speed of powder mixer 1 should be 100 to 120 rpm. ③ Powder mixing step 2: Take out all the mixed materials from powder mixer 1 and add them all to powder mixer 2. Add all the remaining silver powder as well. Mix the powder for 2.5 to 3 hours at a speed of 150 to 180 revolutions per minute. ④Isostatic pressure; ⑤ Sintering; ⑥ Squeeze; ⑦ Composite peripheral argon arc welding; ⑧ Hot-rolled; ⑨ Cold rolling; ⑩ Annealing yields silver tin oxide sheets.

2. The method for preparing silver-tin oxide relay contact material by composite powder mixing according to claim 1, characterized in that, Mixer 1 is a dual-motion mixer; and / or, mixer 2 is a plow-type mixer.

3. The method for preparing silver-tin oxide relay contact material by composite powder mixing according to claim 1 or 2, characterized in that, Specifically, the following steps are included: ①Powder drying: Dry the silver powder and tin oxide powder; ② Powder mixing step 1: Use a dual-motion powder mixer to mix the powder. Add all the tin oxide to the mixing tank, and then add some silver powder. The total amount of silver powder should be 1 / 3 ≤ the mass of silver powder added should be ≤ 1 / 2 of the total amount of silver powder. The mixing time is 1.5~2 hours, and the speed of the powder mixer is 100~120 rpm. ③ Powder mixing step 2: Use a plow-type powder mixer to mix the powder. Take out all the mixed materials from the double motion powder mixer and add them all into the plow-type powder mixer. Add all the remaining silver powder as well. Mix for 2.5 to 3 hours and the powder mixer speed is 150 to 180 rpm to obtain mixed powder. ④ Isostatic pressing: The mixed powder obtained in step ③ isostatically pressed to obtain silver tin oxide mixed powder ingots; ⑤ Sintering: The silver tin oxide mixed powder ingot pressed in step ④ is sintered in air to obtain silver tin oxide alloy ingot, i.e. silver tin oxide blank material.

4. The method for preparing silver-tin oxide relay contact material by composite powder mixing according to claim 3, characterized in that, In step ①, the mass percentage of silver powder is 87-89%, and the mass percentage of tin oxide powder is 11-13%; and / or, the drying temperature is 80-90℃, and the drying time is 2-3 hours.

5. The method for preparing silver-tin oxide relay contact material by composite powder mixing according to claim 3 or 4, characterized in that, In step ④, the isostatic pressure is 15~20MPa, and the pressure holding time is 15~20 seconds.

6. The method for preparing silver-tin oxide relay contact material by composite powder mixing according to claim 3 or 4, characterized in that, In step ⑤, the silver oxide tin mixed powder ingot is first heated to 300~500℃, then the temperature is raised to 850~900℃ and held for ≥2 hours.

7. The method for preparing silver-tin oxide relay contact material by composite powder mixing according to claim 3 or 4, characterized in that, The obtained silver-tin oxide preform material is used to prepare wires and sheets. The specific steps are as follows: Option 1: Preparation of silver tin oxide wire ⑥ Extrusion: The sintered silver-tin oxide alloy ingot is extruded to obtain silver-tin oxide coarse wire; ⑦ Wire drawing: The silver tin oxide coarse wire obtained in step ⑥ is drawn into wire to obtain silver tin oxide relay contact wire material; Step 7: Wire drawing, using the following drawing die: Ф6.0 / annealed / Ф5.6 / annealed / Ф5.2 / annealed / Ф4.8 / annealed / Ф4.4 / annealed / Ф4.0 / annealed / Ф3.6 / annealed / Ф3.2 / annealed / Ф2.9 / annealed / Ф2.6 / annealed / Ф2.38–0.02 mm; Option 2: Preparation of silver tin oxide sheets ⑥ Extrusion: The sintered silver-tin oxide alloy ingot is extruded to obtain silver-tin oxide sheets; ⑦ Composite peripheral argon arc welding: The silver tin oxide sheet extruded by the extruder is combined with a pure silver sheet of the same size and composite peripheral argon arc welding is used to obtain a silver / silver tin oxide composite plate after argon arc welding. ⑧ Hot rolling: The silver / silver tin oxide composite plate after argon arc welding is hot rolled; ⑨ Cold rolling: The hot-rolled silver / silver tin oxide composite plate is cold-rolled according to the dimensional requirements; ⑩ Annealing: Anneal the cold-rolled silver / silver tin oxide composite plate to obtain silver tin oxide sheet.

8. The method for preparing silver-tin oxide relay contact material by composite powder mixing according to claim 7, characterized in that, Option 1: Preparation of silver tin oxide wire. In step ⑥, extrusion is performed using a 1250-ton extruder; and / or, in step ⑥, the specific extrusion operation is as follows: the extrusion cylinder is heated to 380-420℃, the extrusion die is Ф6.0mm, the extrusion speed is 1.5~2.5mm / s, and water cooling is used; and / or, in step ⑦, during wire drawing, the annealing temperature is 550±10℃; the holding time is 0.8-1.2 hours; the wire is drawn in air and then directly removed from the furnace; annealing is performed once during wire drawing.

9. The method for preparing silver-tin oxide relay contact material by composite powder mixing according to claim 7 or 8, characterized in that, Option 2: When preparing silver tin oxide sheets, in step ⑥, extrusion is performed using a 1250-ton extruder; and / or, in step ⑥, the specific extrusion operation is as follows: the extrusion cylinder is heated to 380-420℃, the extrusion die is 5*72mm, and the extrusion speed is 1.5~2.5mm / s; and / or, in step ⑧, hot rolling is performed in a 15kW muffle furnace; and / or, in step ⑧, the hot rolling temperature is 750~800℃, and the holding time is 1.5~2 hours; and / or, in step ⑧, the hot rolling reduction is greater than 50%.

10. The method for preparing silver-tin oxide relay contact material by composite powder mixing according to claim 7 or 8, characterized in that, Option 2: In the preparation of silver tin oxide sheets, in step 10, annealing is carried out in a 15kW muffle furnace; and / or, in step 10, the annealing operation is as follows: heating to 550~600℃, holding at a nitrogen atmosphere for 0.8-1.2 hours, and air cooling to a temperature ≤80℃ before removing from the furnace.

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