A silver tin oxide internal oxidation production process

Abstract

The application discloses a silver tin oxide production process by internal oxidation, which comprises the following steps: vacuum continuous casting of raw materials to obtain silver alloy wire rods; wire drawing, annealing and shearing of the silver alloy wire rods to obtain silver alloy wire particles; internal oxidation, pickling and compression molding of the silver alloy wire particles to obtain silver alloy ingots; and extrusion sintering, annealing and wire drawing of the silver alloy ingots to obtain silver tin oxide finished products. The application has the advantages of reducing processing procedures and improving the electrical properties of silver tin oxide.

Description

Technical Field

[0001] This application relates to the field of electrical contact materials, and in particular to an internal oxidation process for producing silver tin oxide. Background Technology

[0002] Silver tin oxide is one of the main materials used in the low-voltage electrical appliance industry for silver-based electrical contacts. It has good conductivity, resistance to arc erosion, resistance to welding and burn-off. The performance of silver tin oxide plays a key role in the overall reliability of low-voltage electrical appliances.

[0003] The main manufacturing processes for silver-tin oxide electrical contact materials include powder metallurgy, chemical coating, and internal alloy oxidation. Among these, internal alloy oxidation is currently the primary method used by manufacturers. Internal oxidation involves holding a solid silver-tin alloy at a specific oxygen partial pressure and temperature, allowing oxygen atoms to diffuse along grain boundaries or dislocations into the alloy's interior, preferentially reacting with the more reactive tin, resulting in the dispersion and precipitation of tin oxide particles within the matrix. The traditional production process for internal alloy oxidation includes the following steps: alloy smelting, casting, ingot turning, ingot sintering, alloy extrusion, alloy wire drawing, wire shearing, wire internal oxidation, wire forming, ingot sintering, extrusion, wire drawing, and finished product.

[0004] In addition to the disadvantages of numerous processing steps and long processing cycles, the aforementioned traditional production processes also suffer from the problem of shrinkage cavities in the materials, which affects the electrical properties and stability of the materials. Summary of the Invention

[0005] In order to reduce processing steps and improve the electrical properties of silver tin oxide, this application provides an internal oxidation process for producing silver tin oxide.

[0006] The internal oxidation process for producing silver tin oxide provided in this application adopts the following technical solution: An internal oxidation process for producing silver tin oxide includes the following steps: The raw materials were vacuum continuously cast to obtain silver alloy wire. The silver alloy wire is drawn, annealed, and cut to obtain silver alloy wire pellets. The silver alloy wire is subjected to internal oxidation, acid washing, and pressing to obtain a silver alloy ingot; The silver alloy ingot is extruded, sintered, annealed, and drawn into wire to obtain the finished silver tin oxide product.

[0007] By adopting the above technical solution, the alloy smelting in the traditional production process is replaced by vacuum continuous casting. That is, the raw materials are directly obtained as silver alloy wires after vacuum smelting without ingot formation or extrusion. This can effectively reduce the risk of material oxidation during smelting, reduce shrinkage cavities, and improve the yield of the material. Furthermore, vacuum continuous casting can reduce the number of processes, thereby shortening the material processing cycle.

[0008] Furthermore, after continuous casting, the silver alloy is drawn and sheared into wire pellets, which combines plastic deformation and mechanical shearing. This makes the internal structure of the material more uniform, resulting in a more uniform structure after internal oxidation and improving the stability of the material.

[0009] After oxidation within the silver alloy wire mesh, an additional pickling process is added to remove the silver layer formed by the migration of silver atoms to the surface during the high-temperature oxidation process. This removes the oxygen-deficient areas inside the material after subsequent processing, resulting in smaller fluctuations in the material's electrical properties and greater stability.

[0010] Optionally, in the internal oxidation step, the internal oxidation pressure is 0.2~0.3MPa, the temperature is 650℃~750℃, and the holding time is 20~24h.

[0011] By adopting the above technical solution, oxygen diffuses into the interior of the alloy, and the pressure and temperature conditions of internal oxidation are controlled, so that the alloying elements react with oxygen to generate oxides and are evenly distributed in the matrix alloy, resulting in a material with a more uniform metallographic structure.

[0012] Optionally, in the pickling step, the silver alloy wire is soaked in a nitric acid solution with a concentration of 10~15wt% for 4~8 minutes.

[0013] By adopting the above technical solution, after the silver tin oxide undergoes internal oxidation, silver will seep out on the material surface to form a silver layer. The above-mentioned concentration of nitric acid will wash away the surface silver layer without damaging the silver tin oxide, ensuring that no oxygen-deficient area is generated in the subsequent processing and improving the electrical properties of the material.

[0014] Optionally, in the vacuum continuous casting step, after the raw material is vacuum melted at 1400~1500℃, it is condensed and drawn, with a drawing speed of 0.1~0.2m / min, so that the diameter of the silver alloy wire is 5~8mm.

[0015] By adopting the above technical solutions, vacuum melting can avoid the oxidation of the alloy during the melting process and reduce defects such as shrinkage cavities and sand holes. Controlling the matching of the traction rate with the target diameter of the wire can provide sufficient plastic deformation for the wire. The silver alloy wire uses a diameter of 5~8mm as the base diameter for subsequent wire drawing. In the subsequent plastic deformation of wire drawing, a fine and uniform grain structure is further formed inside the alloy, which improves the compactness of the alloy. Wires that are too thick or too thin will cause problems such as uneven structure and unstable structure.

[0016] Optionally, in the wire drawing step of the silver alloy wire, a cold drawing method is adopted, and the wire is drawn in multiple passes, with a deformation of 20-40% in each pass, until the wire is drawn to a diameter of 1-1.5 mm.

[0017] By adopting the above technical solution, the wire is drawn in multiple passes and the deformation amount of each pass is controlled to avoid cracks or stress concentration in the wire caused by a large deformation amount in a single pass. At the same time, the alloy grains are further refined by plastic deformation, thereby improving the density and mechanical properties of the wire.

[0018] Drawing the wire to a diameter of 1~1.5mm matches the diameter of the silver alloy wire (5~8mm), ensuring sufficient plastic deformation to make the internal structure of the material uniform, while not damaging the structural stability of the material. This helps oxygen to penetrate the alloy in the subsequent internal oxidation step, forming oxides that are evenly distributed in the matrix alloy, ensuring good mechanical and electrical properties of the material.

[0019] Optionally, in the vacuum continuous casting step, the vacuum degree of vacuum melting is 10. -3 ~10 -5 Pa.

[0020] By adopting the above technical solution, sufficient vacuum can prevent the alloy from being oxidized during the melting process and reduce the generation of defects in the alloy material.

[0021] Optionally, in the shearing step, the length of the silver alloy wire is 10~15mm.

[0022] By adopting the above technical solution, the length of the silver alloy wire is controlled within the range of 10~15mm. This ensures that the wire can form a structurally stable silver alloy ingot in the subsequent pressing process, while avoiding uneven oxygen penetration during the internal oxidation process due to excessively long wire, thus improving the stability of material quality.

[0023] Optionally, in the extrusion sintering step, the sintering temperature is 770~830℃, the holding time is 6~8h, the extrusion rate is 3~7mm / s, and the extrusion pressure is 5~15MPa.

[0024] By adopting the above technical solutions, the sintering temperature, extrusion rate and pressure are controlled to avoid stress concentration or crack defects in the material during the extrusion process. At the same time, the microstructure is optimized to improve the mechanical strength and electrical stability of the finished silver tin oxide product.

[0025] Optionally, in the annealing step after drawing the silver alloy wire, an ammonia decomposition atmosphere is introduced, the annealing temperature is 500~600℃, and the holding time is 1.5~3h.

[0026] Optionally, the raw materials contain the following components by weight percentage: Ag 89%~90.5%, Sn 6.5%~7.5%, In 2%~2.5%, with the balance being trace elements, including one or more of nickel, bismuth, lanthanum, and cerium.

[0027] In summary, this application has the following beneficial effects: 1. The raw materials in this application are directly processed into silver alloy wires through vacuum melting without ingot formation or extrusion. This effectively reduces the risk of oxidation during melting and minimizes shrinkage cavities, thus increasing the yield. Furthermore, vacuum continuous casting reduces processing steps and shortens the material processing cycle. After continuous casting, the silver alloy wires are drawn and sheared into pellets, combining plastic deformation and mechanical shearing to create a more uniform internal structure. This results in a more uniform structure after internal oxidation, improving material stability. An acid pickling process is added after internal oxidation of the silver alloy pellets to remove the silver layer formed by silver atom migration to the surface during high-temperature internal oxidation. This removes oxygen-depleted areas within the material after subsequent processing, resulting in smaller fluctuations in electrical properties and greater stability.

[0028] 2. In the silver alloy wire and its drawing process, this application controls the matching of the traction rate with the target diameter of the wire, which can provide sufficient plastic deformation for the wire. The silver alloy wire is used as the base diameter for subsequent drawing with a diameter of 5~8mm. In the subsequent plastic deformation of the wire drawing, a fine and uniform grain structure is further formed inside the alloy, which improves the compactness of the alloy and ensures good material mechanical and electrical properties. Attached Figure Description

[0029] Figure 1 This is a morphological diagram of the silver tin oxide product obtained in Example 1 of this application.

[0030] Figure 2 This is a morphological diagram of the silver tin oxide product obtained in Comparative Example 1 of this application.

[0031] Figure 3 This is a morphological diagram of the silver tin oxide product obtained in Comparative Example 2 of this application. Detailed Implementation

[0032] In addition to the problems of numerous processing steps and long processing cycles, the traditional internal oxidation production process of silver tin oxide also suffers from low yield. In the traditional process, the alloy raw materials are melted in the air and then cast into a fixed mold, which makes them prone to premature oxidation, resulting in non-selective oxidation of the surface or the whole, generating oxide inclusions. These oxide inclusions hinder the normal solidification of the molten metal, leading to defects such as shrinkage cavities and cracks inside the ingot, reducing the density, plasticity and toughness of the material. Therefore, the oxidized parts of the ingot surface need to be machined after casting to remove the shrinkage cavities at the head and tail of the ingot, resulting in a low yield.

[0033] Furthermore, the inventors discovered that the unstable electrical properties of silver tin oxide materials obtained by the traditional internal oxidation process are due to the structural characteristics of the silver tin oxide materials. During the high-temperature internal oxidation process, the atomic diffusion ability is enhanced, and silver atoms migrate rapidly to the surface along defect channels such as grain boundaries or dislocations, resulting in a higher silver concentration on the surface than in the bulk phase. This leads to the exudation of a silver layer on the surface of the material. After the wire-particle molding process, an oxygen-deficient region is formed inside the material, affecting the electrical properties of the material.

[0034] Therefore, this application provides an internal oxidation process for producing silver tin oxide. After the material is melted in a vacuum melting furnace, the alloy wire is directly condensed and drawn out, avoiding the risk of oxidation during melting and improving the yield of the material.

[0035] After online intragranular oxidation, pickling is performed to remove the silver layer that seeps onto the material surface, thus avoiding oxygen-deficient areas in subsequent processing and improving the electrical properties of the material.

[0036] Furthermore, the material is not ingot-forming or directly granulated after smelting, because the inventors discovered that directly obtaining granular solids from molten alloys through cooling and solidification can easily cause compositional segregation due to rapid cooling, leading to unevenness during the subsequent internal oxidation process. Therefore, the silver alloy in this application is first formed into wire after continuous casting, and then drawn and sheared into granules. Through the plastic deformation step, the internal structure of the material after internal oxidation is made more uniform, improving the electrical properties of the final product.

[0037] The following is in conjunction with the appendix Figures 1-3 This application will be described in further detail.

[0038]

Example 1

[0039] The components of the raw material, by weight percentage, are: Ag 89%, Sn 7.5%, In 2.5%, with the balance being nickel.

[0040] In the vacuum continuous casting process, the raw materials are fed into a vacuum melting furnace for vacuum melting, and the vacuum degree of the vacuum melting is 10. - 3 Pa, the melting temperature is 1400℃, and after reaching the temperature, it is held for 5 minutes. During the holding process, stirring is started. After the holding is completed, the material is discharged, the cooling water of the crystallizer is turned on, the traction rod is started, and the traction rod pulls the solidified silver alloy wire downward at a traction speed of 0.1m / min, so that the diameter of the silver alloy wire is 8mm.

[0041] S2. The silver alloy wire is drawn, annealed, and cut to obtain silver alloy wire pellets.

[0042] In the wire drawing process, a cold drawing method is used, which involves multiple wire drawing passes. The deformation amount of each wire drawing pass before the last pass is 20%, and the wire is drawn to a diameter of 1.5mm. In the annealing step, the drawn silver alloy wire is placed in a pit-type atmosphere furnace, and an ammonia decomposition atmosphere is introduced. The annealing temperature is 500℃ and the holding time is 3h. In the shearing step, the annealed silver alloy wire is cut, and the length of the resulting silver alloy wire pellet is 10mm.

[0043] S3. The silver alloy wire is internally oxidized, acid-washed, and pressed to obtain a silver alloy ingot.

[0044] In the internal oxidation step, the silver alloy wire is placed in a tubular internal oxidation furnace for internal oxidation. The internal oxidation pressure is 0.2 MPa, the temperature is 750℃, and the holding time is 20 h. In the pickling step, the internally oxidized silver alloy wire is immersed in a 10wt% nitric acid solution for 8 minutes. After immersion, the silver alloy wire is washed multiple times with deionized water and then the moisture is removed by a hot spin dryer. In the pressing step, the acid-washed silver alloy wire is pressed using a four-column hydraulic press to form a silver alloy ingot with a diameter of 80mm.

[0045] S4. The silver alloy ingot is extruded, sintered, annealed, and drawn into wire to obtain the finished silver tin oxide product.

[0046] In the extrusion sintering step, the silver alloy ingot is placed in a box-type resistance furnace for sintering at a temperature of 770℃ and a holding time of 8h. The ingot is then extruded at the specified temperature using an extrusion die with a diameter of 5mm. The extrusion rate is 3mm / s and the extrusion pressure is 15MPa. In the annealing step, a pit-type resistance furnace is used, an air atmosphere is introduced, the annealing temperature is 700℃, and the holding time is 2h; In the wire drawing process, a hot drawing method is used, which involves multiple wire drawing passes. The deformation amount of each wire drawing pass before the last pass is 20%. The wire is drawn to the target diameter, and an annealing is performed after each wire drawing pass. The annealing is carried out in a pit-type resistance furnace with an air atmosphere. The annealing temperature is 700℃ and the holding time is 2 hours.

[0047]

Example 2

[0048] The components of the raw material, by weight percentage, are: Ag 90.5%, Sn 6.5%, In 2%, with the balance being nickel.

[0049] In the vacuum continuous casting process, the raw materials are fed into a vacuum melting furnace for vacuum melting, and the vacuum degree of the vacuum melting is 10. - 5 Pa, the melting temperature is 1500℃, and after reaching the temperature, it is held for 5 minutes. During the holding process, stirring is started. After the holding is completed, the material is discharged, the cooling water of the crystallizer is turned on, the traction rod is started, and the traction rod pulls the solidified silver alloy wire downward at a traction speed of 0.2m / min, so that the diameter of the silver alloy wire is 8mm.

[0050] S2. The silver alloy wire is drawn, annealed, and cut to obtain silver alloy wire pellets.

[0051] In the wire drawing process, a cold drawing method is used, which involves multiple wire drawing passes. The deformation amount of each wire drawing pass before the last pass is 40%, and the wire is drawn to a diameter of 1.5mm. In the annealing step, the drawn silver alloy wire is placed in a pit-type atmosphere furnace, and an ammonia decomposition atmosphere is introduced. The annealing temperature is 600℃ and the holding time is 1.5h. In the shearing step, the annealed silver alloy wire is cut, and the length of the resulting silver alloy wire pellet is 15mm.

[0052] S3. The silver alloy wire is internally oxidized, acid-washed, and pressed to obtain a silver alloy ingot.

[0053] In the internal oxidation step, the silver alloy wire is placed in a tubular internal oxidation furnace for internal oxidation. The internal oxidation pressure is 0.3 MPa, the temperature is 650℃, and the holding time is 24h. In the pickling step, the internally oxidized silver alloy wire is immersed in a 15wt% nitric acid solution for 4 minutes. After immersion, the silver alloy wire is washed multiple times with deionized water and then the moisture is removed by a hot spin dryer. In the pressing step, the acid-washed silver alloy wire is pressed using a four-column hydraulic press to form a silver alloy ingot with a diameter of 80mm.

[0054] S4. The silver alloy ingot is extruded, sintered, annealed, and drawn into wire to obtain the finished silver tin oxide product.

[0055] In the extrusion sintering step, the silver alloy ingot is placed in a box-type resistance furnace for sintering at a temperature of 830℃ and a holding time of 6h. Then, it is extruded at the temperature. An extrusion die with a diameter of 5mm is selected for extrusion, the extrusion rate is 7mm / s, and the extrusion pressure is 5MPa. In the annealing step, a pit-type resistance furnace is used, an air atmosphere is introduced, the annealing temperature is 800℃, and the holding time is 2h; In the wire drawing process, a hot drawing method is used, and the wire is drawn in multiple passes. The deformation amount of each wire drawing before the last pass is 40%. The wire is drawn to the target diameter, and an annealing is performed after each wire drawing. The annealing is carried out in a pit-type resistance furnace with an air atmosphere. The annealing temperature is 800℃ and the holding time is 2h.

[0056]

Example 3

[0057] In step S1, the diameter of the silver alloy wire obtained after vacuum casting of the raw material is 5mm. In step S2, the diameter of the silver alloy wire after cold drawing is 1 mm.

[0058]

Example 4

[0059] In step S1, the diameter of the silver alloy wire obtained after vacuum casting of the raw material is 10 mm.

[0060]

Example 5

[0061] In step S1, the diameter of the silver alloy wire obtained after vacuum casting of the raw material is 4 mm.

[0062]

Example 6

[0063] In step S2, the diameter of the silver alloy wire after cold drawing is 2mm.

[0064]

Example 7

[0065] In step S2, the diameter of the silver alloy wire after cold drawing is 0.5 mm.

[0066] Comparative Example 1 An internal oxidation process for producing silver tin oxide is described. The difference between this comparative example and Example 1 is that there is no acid washing step after internal oxidation.

[0067] Specifically, the S3 steps are as follows: The silver alloy wire is internally oxidized and then pressed to obtain a silver alloy ingot.

[0068] In the internal oxidation step, the silver alloy wire is placed in a tubular internal oxidation furnace for internal oxidation. The internal oxidation pressure is 0.2 MPa, the temperature is 750℃, and the holding time is 20 h. In the pressing step, the internally oxidized silver alloy wire is pressed using a four-column hydraulic press to form a silver alloy ingot with a diameter of 80mm.

[0069] Comparative Example 2 An internal oxidation process for producing silver tin oxide includes the following steps: Weigh out the following by weight percentage: Ag 89%, Sn 7.5%, In 2.5%, with the balance being nickel, as raw materials. Put the raw materials into a melting furnace and melt at 1400℃. After reaching the temperature, hold for 5 minutes. Start stirring during the holding process. After the holding is completed, discharge the material and pour it into a mold to form an alloy ingot.

[0070] The alloy ingot is machined and then extruded into wire at 700°C using a hot extrusion press. It is then cold-drawn and drawn to a diameter of 1.5 mm. The drawn wire is then placed in a pit-type atmosphere furnace and annealed at 500°C for 3 hours. After the annealing is completed, it is cut into 10 mm long wire pellets.

[0071] The silver alloy wire was internally oxidized by placing it in a tubular internal oxidation furnace at a pressure of 0.2 MPa and a temperature of 750°C for 20 hours. Then, the internally oxidized silver alloy wire was immersed in a 10 wt% nitric acid solution for 8 minutes. After immersion, the silver alloy wire was washed multiple times with deionized water and then dried with a hot spin dryer.

[0072] The acid-washed silver alloy wire pellets were pressed using a four-column hydraulic press to form silver alloy ingots with a diameter of 80 mm. The silver alloy ingots were then sintered in a box-type resistance furnace at 770℃ for 8 hours. Following sintering, a 5 mm diameter die was used for extrusion at a rate of 3 mm / s and a pressure of 15 MPa. After extrusion, the ingots were annealed in a pit-type resistance furnace with an air atmosphere at 700℃ for 2 hours.

[0073] Finally, a hot drawing method is used, with multiple drawing passes. The deformation amount of each drawing pass before the last pass is 20%. The wire is drawn to the target diameter to obtain the finished silver tin oxide product.

[0074] Comparative Example 3 An internal oxidation process for producing silver tin oxide includes the following steps: Weigh out the following by weight percentage: Ag 89%, Sn 7.5%, In 2.5%, with the balance being nickel, as raw materials. Put the raw materials into a vacuum melting furnace and melt at 1400℃. After reaching the temperature, hold for 5 minutes. Start stirring during the holding process. After the holding is completed, discharge the material and solidify it through atomization cooling to form granular alloy.

[0075] The granular alloy was internally oxidized by placing it in a tubular internal oxidation furnace at an internal oxidation pressure of 0.2 MPa, a temperature of 750℃, and a holding time of 20 h. Then, the internally oxidized granular alloy was immersed in a 10 wt% nitric acid solution for 8 min. After immersion, the granular alloy was washed multiple times with deionized water and then dried with a hot spin dryer.

[0076] The pickled granular alloy was pressed using a four-column hydraulic press to form silver alloy ingots with a diameter of 80 mm. The silver alloy ingots were then sintered in a box-type resistance furnace at 770℃ for 8 hours. Following sintering, a 5 mm diameter die was used for extrusion at a rate of 3 mm / s and a pressure of 15 MPa. After extrusion, the ingots were annealed in a pit-type resistance furnace with an air atmosphere at 700℃ for 2 hours.

[0077] Finally, a hot drawing method is used, with multiple drawing passes. The deformation amount of each drawing pass before the last pass is 20%. The wire is drawn to the target diameter to obtain the finished silver tin oxide product.

[0078] Performance testing Alloy morphology: The silver-tin oxide products of Example 1, Comparative Example 1, and Comparative Example 2 were analyzed for alloy morphology. The results are as follows: Figure 1 , Figure 2 and Figure 3 As shown.

[0079] Elongation: The silver tin oxide products of Examples 1-7 and Comparative Examples 1-3 were subjected to elongation tests. The elongation of silver tin oxide products with different diameters was tested, and the results are shown in Table 1.

[0080] Table 1

[0081] Electrical life: Electrical life tests were conducted on the silver tin oxide products of Examples 1-7 and Comparative Examples 1-3. The silver wire was φ2.2mm, and the rivets were made with heads of φ4.4mm×1.0mm. The test load conditions were: resistive, voltage 250V, current 30A, on / off time ratio 1s:1s, and moving / stationary contact gap 0.6mm. When the contacts partially melted and stuck together due to the high temperature of the electric arc during the on / off process and could not be separated normally, the number of electrical life tests was recorded. The results are shown in Table 2.

[0082] Table 2

[0083] like Figures 1-3 As shown, the silver tin oxide prepared in Example 1 has a uniform and dense microstructure; the silver tin oxide prepared in Comparative Examples 1 and 2 has oxygen-deficient regions, which affects the electrical properties of the material, and the microstructure uniformity is also significantly inferior to that of Example 1. This proves that the traditional internal oxidation process easily oxidizes the silver alloy during the smelting and casting process, causing problems such as shrinkage cavities and sand holes, which affect the structural stability.

[0084] As can be seen from Tables 1 and 2, the elongation and electrical lifetime of the silver tin oxide prepared in Example 1 are better than those of the silver tin oxide prepared in Comparative Examples 1-3, which proves the importance of pickling after the internal oxidation step and shows a significant improvement over the traditional internal oxidation process.

[0085] Comparing Example 1 with Examples 4-7, it can be seen that controlling the diameter of the silver alloy wire and matching it with the diameter after drawing can provide sufficient plastic deformation for the wire, making the internal structure of the alloy more dense and uniform, thereby improving elongation and electrical life, and improving processability and electrical properties.

[0086] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A process for producing silver tin oxide via internal oxidation, characterized in that: Includes the following steps: The raw materials were vacuum continuously cast to obtain silver alloy wire. The silver alloy wire is drawn, annealed, and cut to obtain silver alloy wire pellets. The silver alloy wire is subjected to internal oxidation, acid washing, and pressing to obtain a silver alloy ingot; The silver alloy ingot is extruded, sintered, annealed, and drawn into wire to obtain the finished silver tin oxide product.

2. The internal oxidation process for producing silver tin oxide according to claim 1, characterized in that: In the internal oxidation step, the internal oxidation pressure is 0.2~0.3MPa, the temperature is 650℃~750℃, and the holding time is 20~24h.

3. The internal oxidation process for producing silver tin oxide according to claim 1, characterized in that: In the pickling step, the silver alloy wire is soaked in a nitric acid solution with a concentration of 10~15wt% for 4~8 minutes.

4. The internal oxidation process for producing silver tin oxide according to claim 1, characterized in that: In the vacuum continuous casting process, the raw material is melted in a vacuum at 1400~1500℃, then condensed and drawn at a rate of 0.1~0.2m / min, so that the diameter of the silver alloy wire is 5~8mm.

5. The internal oxidation process for producing silver tin oxide according to claim 4, characterized in that: In the wire drawing process of the silver alloy wire, a cold drawing method is used, and the wire is drawn in multiple passes. The deformation amount of each pass is 20-40%, and the wire is drawn to a diameter of 1-1.5 mm.

6. The internal oxidation process for producing silver tin oxide according to claim 4, characterized in that: In the vacuum continuous casting process, the vacuum degree of vacuum melting is 10. -3 ~10 -5 Pa.

7. The internal oxidation process for producing silver tin oxide according to claim 1, characterized in that: During the shearing step, the length of the silver alloy wire is 10~15mm.

8. The internal oxidation process for producing silver tin oxide according to claim 1, characterized in that: In the extrusion sintering step, the sintering temperature is 770~830℃, the holding time is 6~8h, the extrusion rate is 3~7mm / s, and the extrusion pressure is 5~15MPa.

9. The internal oxidation process for producing silver tin oxide according to claim 1, characterized in that: In the annealing step after drawing the silver alloy wire, an ammonia decomposition atmosphere is introduced, the annealing temperature is 500~600℃, and the holding time is 1.5~3h.

10. The internal oxidation process for producing silver tin oxide according to claim 1, characterized in that: The components in the raw materials, by weight percentage, are: Ag 89%~90.5%, Sn 6.5%~7.5%, In 2%~2.5%, with the balance being trace elements, including one or more of nickel, bismuth, lanthanum, and cerium.

Images