Preparation method of silver tin oxide composite material added with rare earth oxide

Abstract

The invention relates to a preparation method of a silver tin oxide composite material added with rare earth oxide. The preparation method comprises the steps of burdening, smelting, water atomization, powder drying, powder screening, powder mixing, powder oxidation, cold isostatic pressing, sintering, extrusion and wire drawing. According to the silver tin oxide composite material prepared by the method, the granularity of the oxide is fine and uniformly distributed, the electrical performance is enhanced, meanwhile, the influence on the processing performance is small, the cost and process loss of the preparation material are not additionally increased, special equipment does not need to be designed, the silver tin oxide composite material is almost universal with existing production equipment, the whole process is environment-friendly, and the method has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite technology, and specifically relates to a method for preparing a silver-tin oxide composite material with added rare earth oxides. Background Technology

[0002] AgCdO materials can achieve arc extinguishing and heat dissipation through the decomposition and sublimation of CdO, thus earning them the reputation of "universal contact materials." However, the Cd vapor released during CdO decomposition is extremely harmful to human health and the environment, and is gradually being phased out. Silver-tin oxide composite material (AgSnO2) has become the optimal alternative to AgCdO materials due to its excellent arc erosion resistance and anti-welding properties. Unlike AgCdO's arc erosion resistance mechanism, AgSnO2 primarily utilizes the thermal stability of SnO2 particles to increase the viscosity of the contact molten pool, thereby achieving anti-spatter and anti-welding properties. However, with increasingly stringent electrical loads and harsher contact working environments, the performance of AgSnO2 materials urgently needs improvement, especially in sealing applications with impact loads, where the decomposition and reduction of oxides can cause fusion failure.

[0003] Rare earth oxides possess very high thermal stability, with melting points generally above 2000℃. La₂O₃ has a melting point of 2217℃, and CeO₂ reaches as high as 2600℃. Their hardness is comparable to SnO₂, and they also exhibit rich electrical properties. Adding them to AgSnO₂ materials can significantly improve the electrical properties without excessively weakening processing performance. However, rare earth elements have extremely low miscibility with Ag, so they can only be added through a powder mixing process. Due to the extremely poor uniformity of the multi-component powder mixture (Ag powder, SnO₂ powder, ReO powder (rare earth oxides)) and the poor bonding strength between the oxides and the Ag matrix, the material's performance does not meet expectations. Improving the uniformity of the material's microstructure and the bonding strength between the oxides and the Ag matrix are key to improving the material's performance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing silver tin oxide composite material with added rare earth oxides, thereby solving the problem of microstructure uniformity of current silver tin oxide composite materials with added rare earth oxides.

[0005] This invention provides a method for preparing a silver-tin oxide composite material with added rare earth oxides, comprising the following steps:

[0006] (1) Silver ingots, tin ingots and promoting oxides are smelted to obtain an alloy melt;

[0007] (2) The alloy melt is atomized with water to obtain alloy powder, which is then dried and sieved;

[0008] (3) The sieved alloy powder and rare earth oxides are mixed evenly in an offset double motion powder mixer, and then the powder is oxidized.

[0009] (4) The powder obtained in step (3) is cold isostatically pressed into ingots, then sintered, and finally extruded into wires and drawn into wires as required to obtain silver tin oxide composite material with added rare earth oxides.

[0010] Preferably, the promoting oxide in step (1) is one or more of indium ingot, bismuth ingot, and copper ingot.

[0011] Preferably, the alloy melt elemental composition in step (1) is: Sn content 2%-10%, total content of promoting oxides 1.5%-3%, and balance Ag.

[0012] Preferably, the melting temperature in step (1) is 1000-1100℃, and the melting process requires covering the surface of the molten liquid with charcoal.

[0013] Preferably, the water atomization parameters in step (2) are: atomizing water pressure 35-40MPa, and nozzle 3-5mm.

[0014] Preferably, the rare earth oxide in step (3) is one or more of CeO2, La2O3, Yb2O3, and Y2O3, and the content of rare earth elements in the powder is 0.2%-2%. The rare earth oxide is a particle with a D502-4μm, and the mixing method adopts an offset tilting rotation method, so that the powder is rotated and also undergoes transverse shearing motion.

[0015] Preferably, the powder oxidation parameters in step (3) are: 350℃ for 1 hour for powder turning, 500℃ for 1 hour for powder turning, and 600-800℃ for more than 12 hours for powder turning. Powder oxidation is carried out at a low temperature, which can make the powder mix more evenly and also avoid the alloy powder from sticking together and clumping.

[0016] Preferably, the cold isostatic pressure in step (4) is 150-250 MPa.

[0017] Preferably, the sintering parameters in step (4) are: holding at 300-400℃ for 2 hours, holding at 400-600℃ for 2 hours, holding at 850-920℃ for 4 hours, then repressing the ingot under a pressure of 550-600Tf, and holding at 850-920℃ for 4 hours after repressing. The sintering process is carried out in stages, with hot repressing after high-temperature sintering, and then high-temperature sintering again after pressing to improve the density of the material.

[0018] Preferably, the extrusion parameters in step (4) are: pressure ratio 250-350, extrusion speed 1-3 mm / s, and wire diameter 3.5-8 mm.

[0019] This invention combines powder pre-oxidation technology with powder mixing technology, transforming traditional multi-component powder mixing into a two-component mixture of silver alloy powder and rare earth oxide powder. This significantly reduces the difficulty of powder mixing and improves uniformity. Sn and other elements in the alloy powder are uniformly distributed within the Ag lattice. Internal oxidation generates oxides from the solute elements, effectively enhancing the bonding strength between the oxides and the silver matrix. Multiple powder turning during oxidation achieves a mixing effect and prevents alloy powder from agglomerating, resulting in a uniform oxide distribution. Segmented sintering enhances the sintering strength between powders, and hot pressing further increases material density, increasing the bonding force between rare earth oxides and other components. Through these measures, AgSnO2 materials with fine, uniformly distributed oxide particles and excellent electrical and processing properties can be prepared.

[0020] Beneficial effects

[0021] The silver-tin oxide composite material prepared by this invention has a fine and uniform oxide particle size distribution, which enhances electrical properties while having little impact on processing performance. The cost of material preparation and process losses are not increased by extra. No special equipment needs to be designed, and it can be used almost interchangeably with existing production equipment. Moreover, the whole process is environmentally friendly and has good application prospects. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0023] Figure 2 Metallographic (1000X) of AgSnO2(12) material prepared in Example 1.

[0024] Figure 3 Metallographic image of AgSnO2(12) material prepared by ordinary powder mixing process (1000X). Detailed Implementation

[0025] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0026] Example 1

[0027] This embodiment provides a method for preparing a silver-tin oxide composite material with added rare earth oxides, including the following steps:

[0028] 1) Weigh out 27.15 kg of pure silver, 2.4 kg of tin ingots, and 0.45 kg of bismuth ingots, totaling 30 kg, according to the mass ratio of Ag: 90.5%, Sn: 8%, and Bi: 1.5%.

[0029] 2) First, melt the silver ingot in a ceramic crucible at 1050℃, cover the silver surface with charcoal, then add tin ingot and bismuth ingot and stir.

[0030] 3) Water atomization: atomizing water pressure 38MPa, nozzle size 4.0mm;

[0031] 4) Drying powder: Dry at 150℃ for 2 hours, turning the powder over every half hour;

[0032] 5) Sieving: Use a 200-mesh sieve to sieve and remove large particles;

[0033] 6) Powder mixing: Weigh 120.0g of CeO2 powder with D50 of 2μm, and weigh 20kg of alloy powder after sieving. Put them into an offset double motion powder mixer and mix for 2 hours at a speed of 15r / min.

[0034] 7) Powder oxidation: keep at 350℃ for 1 hour and turn the powder, keep at 500℃ for 1 hour and turn the powder, keep at 700℃ for more than 12 hours;

[0035] 8) Cold isostatic pressing: pressing powder into ingots under a pressure of 200MPa;

[0036] 9) Sintering: Hold at 400℃ for 2 hours, hold at 600℃ for 2 hours, hold at 850℃ for 4 hours, then press the ingot under 580Tf pressure, and hold at 900℃ for 4 hours after pressing.

[0037] 10) Extrusion: Pressure ratio 320, average extrusion speed 2mm / s, wire diameter 5.0mm;

[0038] 11) Wire drawing: The extruded wire is drawn to φ1.9mm, and annealing can be carried out when the cumulative amount reaches 20%.

[0039] The AgSnO2(12) material with CeO2 added prepared in this embodiment and the AgSnO2(12) material of the same composition prepared by a conventional powder mixing process (directly mixing silver tin oxide raw material with rare earth oxides) are compared with each other by a 1000-fold gold ratio. Figure 2 and 3 As shown, the oxide material prepared in this embodiment is finer and more evenly distributed.

Claims

1. A method for preparing a silver-tin oxide composite material with added rare earth oxides, characterized in that, Includes the following steps: (1) Silver ingots, tin ingots and promoting oxides are smelted to obtain an alloy melt; (2) The alloy melt is atomized with water to obtain alloy powder, which is then dried and sieved; (3) The sieved alloy powder and rare earth oxides are mixed evenly in an offset double motion powder mixer, and then the powder is oxidized. (4) The powder obtained in step (3) is cold isostatically pressed into ingots, then sintered, and finally extruded into wires and drawn into wires as required to obtain silver tin oxide composite material with added rare earth oxides.

2. The preparation method according to claim 1, characterized in that, The promoting oxide in step (1) is one or more of indium ingot, bismuth ingot, and copper ingot.

3. The preparation method according to claim 1, characterized in that, The alloy melt elemental composition in step (1) is: Sn content 2%-10%, total content of promoting oxides 1.5%-3%, and balance Ag.

4. The preparation method according to claim 1, characterized in that, The melting temperature in step (1) is 1000-1100℃.

5. The preparation method according to claim 1, characterized in that, The water atomization parameters in step (2) are: atomizing water pressure 35-40MPa, and nozzle 3-5mm.

6. The preparation method according to claim 1, characterized in that, The rare earth oxides in step (3) are one or more of CeO2, La2O3, Yb2O3, and Y2O3, and the content of rare earth elements in the powder is 0.2%-2%.

7. The preparation method according to claim 1, characterized in that, The powder oxidation parameters in step (3) are: 350℃ for 1 hour for powder turning, 500℃ for 1 hour for powder turning, and 600-800℃ for more than 12 hours for powder turning.

8. The preparation method according to claim 1, characterized in that, The cold isostatic pressure in step (4) is 150-250 MPa.

9. The preparation method according to claim 1, characterized in that, The sintering parameters in step (4) are: holding at 300-400℃ for 2 hours, holding at 400-600℃ for 2 hours, holding at 850-920℃ for 4 hours, then repressing the ingot under a pressure of 550-600Tf, and then holding at 850-920℃ for 4 hours after repressing.

10. The preparation method according to claim 1, characterized in that, The extrusion parameters in step (4) are: pressure ratio 250-350, extrusion speed 1-3mm / s, and wire diameter 3.5-8mm.

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