Silver tin oxide contact material for magnetic latching relay and preparation method thereof

Abstract

This application discloses a method for preparing silver-tin oxide electrical contact material for magnetic latching relays, comprising the following steps: depositing indium oxide and tin oxide sequentially on the surface of silver powder by physical vapor deposition to obtain a coated powder, wherein the indium oxide content is 0.3~0.8wt%, the tin oxide content is 8~10wt%, and the balance is silver; mixing the coated powder, yttrium-stabilized tetragonal zirconium oxide, and trace additives to obtain a composite powder, wherein the trace additives are copper oxide or tungsten oxide, and the mass ratio of yttrium-stabilized tetragonal zirconium oxide to coated powder is (2~5):100; hot pressing the composite powder at 25~35MPa to obtain a blank, and holding it at that temperature for 1~2h; hot extrusion processing to process the blank into a rod; multi-pass drawing to produce a wire, and performing intermediate annealing treatment during the drawing process, with each annealing time being 1~2h. The electrical contact prepared by this method has high contact resistance stability and arc erosion resistance.

Description

Technical Field

[0001] This application relates to the field of silver-based electrical contact material preparation technology, and in particular to a silver tin oxide electrical contact material for use in magnetic latching relays and its preparation method. Background Technology

[0002] Silver tin oxide (AgSnO2), as an ideal environmentally friendly low-voltage contact material to replace toxic silver cadmium oxide (AgCdO), is widely used in fields such as magnetic latching relays. Its manufacturing processes encompass internal oxidation, sintering extrusion, powder metallurgy, and chemical coating, enabling the production of various product forms such as single-layer / double-layer riveted contacts and plate contacts. This material possesses many excellent properties: low resistivity, effectively reducing power loss; strong resistance to welding, preventing contacts from fusing together under the high temperature and pressure generated during contact closure, ensuring normal relay operation; and excellent resistance to arc erosion, resisting high-temperature ablation during contact opening, extending contact lifespan. Furthermore, doping processes can optimize temperature rise characteristics, ensuring stable performance under different operating conditions, meeting the reliability and stability requirements of magnetic latching relays for contact materials.

[0003] However, existing silver-tin oxide electrical contact materials still have some shortcomings. Regarding arc erosion resistance, although its overall performance is superior to many other materials, under extreme operating conditions of high current and high frequency, the intense thermal and energy shocks generated by the arc will still cause gradual wear of the contact surface material, affecting the contact's service life and reliability. In terms of contact resistance stability, after repeated arc contact, tin oxide will accumulate on the contact surface, leading to increased contact resistance, accelerated temperature rise, and affecting the normal operation of the relay. Summary of the Invention

[0004] To address the shortcomings of traditional electrical contacts used in magnetic latching relays in terms of contact resistance stability and arc erosion resistance, a silver tin oxide electrical contact material for magnetic latching relays and its preparation method are provided.

[0005] The above-mentioned objective of this invention is achieved through the following technical solutions: A method for preparing a silver-tin oxide electrical contact material for use in magnetic latching relays includes the following steps: S1: The coated powder, yttrium-stabilized tetragonal zirconium oxide and trace additives are mixed to obtain a composite powder. The trace additives are copper oxide or tungsten oxide. The mass ratio of yttrium-stabilized tetragonal zirconium oxide to coated powder is (2~5):100. The composite powder is hot-pressed at 700~800℃ to obtain a blank. The pressure is 25~35MPa and the holding time is 1~2h. S2: The billet is processed into bars using a hot extrusion process, with an extrusion ratio of (200~400):1; S3: The wire is produced by multiple drawing processes, and intermediate annealing is performed during the drawing process, with each annealing time being 1~2 hours; The coated powder is obtained by sequentially depositing indium oxide and tin oxide on the surface of silver powder using physical vapor deposition. The coated powder contains 0.3~0.8 wt% indium oxide, 8~10 wt% in tin oxide, and the balance is silver.

[0006] By employing the above technical solution, indium oxide and tin oxide are deposited on the silver surface using physical vapor deposition (PVD). This effectively prevents oxide agglomeration, ensuring uniform dispersion of oxide particles within the silver matrix. Furthermore, under the influence of an electric arc, indium oxide promotes the decomposition and reformation of tin oxide, generating a stable indium-tin oxide composite layer, enhancing the arc dispersion capability. The addition of indium oxide also lowers the decomposition temperature of tin oxide, improving arc stability. The added yttrium-stabilized tetragonal zirconium oxide possesses high hardness and a phase transformation toughening effect, inhibiting arc erosion. It maintains chemical stability even at the instantaneous high temperature of the arc, without decomposing or reacting with the silver matrix. The uniformly dispersed yttrium-stabilized zirconium oxide effectively pins grain boundaries and dislocations, hindering grain boundary migration and maintaining a fine-grained structure, which is beneficial for arc dispersion and energy dissipation. Copper oxide or tungsten oxide forms high-melting-point compounds at high temperatures, further inhibiting localized melting at the arc root. The reduction product, copper, improves the wettability and bonding force between silver and oxides, resulting in a denser, stronger, and less prone-to-peel surface oxide layer formed under arc ablation. Tungsten oxide, with its high electron work function, enhances the overall electron work function of the material, leading to a more dispersed arc energy distribution. Tungsten oxide particles undergo localized sintering with other oxides, generating a more complex and heat-resistant composite oxide surface layer, providing a better thermal barrier and arc blocking effect. The hot extrusion process in step S3 induces intense plastic deformation through a high extrusion ratio, refining grains, eliminating porosity, and forming a texture along the extrusion direction, optimizing electron transport paths, and enhancing arc stability and contact resistance stability. Multi-pass drawing and intermediate annealing further refine grains, eliminate internal stress, stabilize the microstructure, and prevent contact surface deformation and resistance fluctuations through cyclic deformation and recrystallization. In summary, this enhances resistance to arc erosion, contact resistance stability, and electrical conductivity.

[0007] Optionally, the deposition temperature in the preparation of the coated powder is 180~190℃.

[0008] By adopting the above technical solution, when the temperature is too low, the deposition rate is slow and the coating layer is incomplete; when the temperature is too high, indium oxide and tin oxide may decompose or agglomerate prematurely. At this temperature, the deposited atoms have sufficient migration energy to form a dense and firmly bonded coating layer, avoid interface defects, ensure the interface bonding strength between oxide and silver powder, and enhance arc erosion resistance, contact resistance stability and conductivity.

[0009] Optionally, in step S1, before mixing the coated powder, yttrium-stabilized tetragonal zirconia, and trace additives, the coated powder is subjected to plasma treatment under an argon atmosphere.

[0010] By adopting the above technical solution, plasma treatment is carried out in an argon atmosphere. High-energy particles bombard the surface of the coated powder to remove organic pollutants and oxide layers, activate surface atoms, increase surface energy and roughness, enhance the interfacial bonding force between the coated powder and yttrium-stabilized zirconium oxide and additives, promote mixing uniformity, and argon gas, as an inert gas, prevents secondary oxidation and ensures surface cleanliness.

[0011] Optionally, the mass ratio of trace additives to coated powder in the composite powder of step S1 is (0.5~2):100.

[0012] By adopting the above technical solution, this ratio ensures that the additives form a nanoscale dispersed phase without disrupting the continuity of the silver matrix. Furthermore, copper oxide or tungsten oxide reacts with silver or oxides during hot pressing to generate a hard phase that pins grain boundaries and inhibits grain growth under arc erosion. At the same time, the low-melting-point phase liquefies under the instantaneous high temperature of the arc, filling microcracks and reducing contact resistance jumps.

[0013] Optionally, the extrusion temperature for step S2 is 700~750℃.

[0014] By adopting the above technical solutions, dynamic recrystallization can be fully carried out within this range, refining the grains while avoiding grain coarsening or zirconium oxide phase transformation. High-temperature plastic deformation promotes dislocation reorganization and texture formation, optimizes grain boundary distribution, and reduces grain boundary resistance.

[0015] Optionally, after obtaining the bar in step S2, the bar is placed in liquid nitrogen at -196°C for cooling for 8~12 hours.

[0016] By adopting the above technical solution, liquid nitrogen cryogenic treatment utilizes the thermal shrinkage effect to generate compressive stress inside the material, refines the grains and increases the dislocation density, stabilizes the oxide distribution, reduces residual stress, suppresses high-temperature phase transformation, enhances interfacial bonding strength, improves resistance to arc erosion, and stabilizes contact resistance.

[0017] Optionally, the annealing temperature in step S3 is 500~600℃.

[0018] By adopting the above technical solution, the annealing temperature of 500~600℃ is selected within the recrystallization temperature range of silver, which can effectively eliminate the internal stress and dislocations generated during drawing, promote recovery and recrystallization, and form stable grain boundaries. This temperature avoids excessive grain growth, ensures uniform grain size, reduces grain boundary scattering, maintains the thermal stability of the oxide, improves resistance to arc erosion, optimizes electrical conductivity, and ensures contact resistance stability.

[0019] The second objective of this invention is as follows: A silver-tin oxide electrical contact material for use in magnetic latching relays, obtained by the above preparation method.

[0020] In summary, this application has at least the following beneficial effects: (1) Physical vapor deposition is used to achieve uniform nanoscale coating of oxides in silver matrix, and combined with the synergistic effect of indium oxide and tin oxide and the phase transformation toughening and pinning effect of yttrium-stabilized zirconium oxide, the resistance to arc erosion is enhanced. (2) Yttrium-stabilized tetragonal zirconia can effectively suppress arc erosion by means of high hardness, phase transformation toughening and high temperature stability, and maintain fine grain structure by pinning grain boundary dislocations, thereby promoting arc dispersion and energy dissipation. (3) By optimizing the hot extrusion process to induce strong plastic deformation to refine the grains, and by combining multiple drawing and intermediate annealing to eliminate internal stress and stabilize the structure, the long-term stability of the contact resistance is guaranteed. Detailed Implementation

[0021] raw material Yttrium-stabilized tetragonal zirconium oxide, model JA-TAP-3mol, ZrO2 content 94.7wt%, purchased from Shandong Shengtai Zirconium Resources Co., Ltd. Tin oxide, indium oxide, silver powder, copper oxide powder (average particle size 1.5µm), tungsten oxide powder (average particle size 1.5µm), tin oxide powder (average particle size 1.5µm), and indium oxide powder (average particle size 2.0µm) are all commercially available.

[0022] Preparation Example 1 A coated powder is prepared from 90.5 kg of silver powder, 0.5 kg of indium oxide, and 9 kg of tin oxide. The preparation method is as follows: A fluidized bed physical vapor deposition apparatus is used, with a vacuum degree ≤1×10⁻⁶. -3 Under conditions of Pa and temperature of 185℃, indium oxide and tin oxide were sequentially deposited on the surface of silver powder. When using an indium oxide target for deposition, the power was 4kW and the time was 30min. When using a tin oxide target for deposition, the power was 4.5kW and the time was 45min. After the deposition process was completed, the powder was cooled to 40℃ under an argon atmosphere and discharged to obtain coated powder.

[0023] Preparation Example 2 A coated powder differs from Preparation Example 1 in that: at a temperature of 180°C, indium oxide and tin oxide are sequentially deposited on the surface of silver powder; the rest is the same as Preparation Example 1.

[0024] Preparation Example 3 A coated powder differs from Preparation Example 1 in that: at a temperature of 190°C, indium oxide and tin oxide are sequentially deposited on the surface of silver powder; the rest is the same as Preparation Example 1.

[0025] Preparation Example 4 A coated powder differs from Preparation Example 1 in that: at a temperature of 175°C, indium oxide and tin oxide are sequentially deposited on the surface of silver powder; the rest is the same as Preparation Example 1.

[0026] Preparation Example 5 A coated powder differs from Preparation Example 1 in that: at a temperature of 195°C, indium oxide and tin oxide are sequentially deposited on the surface of silver powder; the rest is the same as Preparation Example 1.

[0027] Preparation Example 6 A coated powder differs from Preparation Example 1 in that it is prepared from 91.7 kg of silver powder, 0.3 kg of indium oxide, and 8 kg of tin oxide; the rest of the powder is the same as in Preparation Example 1.

[0028] Preparation Example 7 A coated powder differs from Preparation Example 1 in that it is prepared from 89.2 kg of silver powder, 0.8 kg of indium oxide, and 10 kg of tin oxide; the rest of the powder is the same as Preparation Example 1.

[0029] Example 1 A silver-tin oxide electrical contact material for use in magnetic latching relays is prepared from the following components by weight: 100 kg of coated powder, 4 kg of yttrium-stabilized tetragonal zirconium oxide, and 1 kg of copper oxide powder.

[0030] Its preparation method is as follows: S1: The coated powder was plasma-treated in 200W argon plasma for 15 minutes. The coated powder, yttrium-stabilized tetragonal zirconia, and copper oxide were then added to a mixer and mixed at 200 rpm for 3 hours to obtain a composite powder. The composite powder was then loaded into a graphite mold and transferred to a vacuum hot-pressing sintering furnace. The furnace cavity was evacuated to a vacuum level of 1×10⁻⁶. -2 Pa, heated to 750°C at a rate of 12°C / min, then pressure of 30 MPa was applied and maintained at this temperature and pressure for 1.5 h, heating was stopped, the furnace body was allowed to cool naturally to 200°C, the pressure was released, and the billet was obtained, wherein the coating powder was derived from preparation example 1; S2: Preheat the billet at 700℃ for 60 minutes, then add the preheated billet into an extrusion cylinder at 730℃ for extrusion. The extrusion ratio (the ratio of the extrusion cylinder area to the product interface area) is 300:1, and the extrusion rod advance speed is 10mm / s. The extruded bar is cooled to room temperature (25℃) under an argon protective atmosphere to obtain the bar. The bar is then placed in a -196℃ liquid nitrogen cryogenic treatment for 10 hours and naturally heated to room temperature (25℃). S3: The bar stock is drawn in multiple passes. In this embodiment, three passes are used. The first pass has an inlet diameter of 9.0 mm and an outlet diameter of 6.0 mm; the second pass has an inlet diameter of 6 mm and an outlet diameter of 3.5 mm; and the third pass has an inlet diameter of 3.5 mm and an outlet diameter of 2 mm. After the first and second passes, annealing is performed under a vacuum of 5 × 10⁻⁶. - 3 Pa, annealing temperature is 550℃, holding time is 1.5h, and then furnace cooled to 300℃ to obtain wire with a diameter of 2.0mm.

[0031] Comparative Example 1 A silver-tin oxide electrical contact material for use in magnetic latching relays is prepared from the following raw materials: 88.5 kg of silver powder, 0.5 kg of indium oxide powder, 4 kg of yttrium-stabilized tetragonal zirconium oxide, 9 kg of tin oxide powder, and 1 kg of copper oxide powder.

[0032] Its preparation method is as follows: S1: Silver powder, indium oxide powder, yttrium-stabilized tetragonal zirconium oxide, tin oxide powder and copper oxide powder are added to a ball mill and mixed at 300 r / min for 10 h with a ball-to-material ratio of 10:1 to obtain composite powder; S2: Load the composite powder into a graphite mold and transfer it to a vacuum hot-pressing sintering furnace. Evacuate the furnace cavity to 1×10⁻⁶. - 2 Pa, heated to 750℃ at a rate of 12℃ / min, then pressure of 30MPa was applied, and the temperature and pressure were maintained at this level for 1.5 hours. Heating was then stopped, and the furnace body was allowed to cool naturally to 200℃. The pressure was then released to obtain the billet. S3: Preheat the billet at 700℃ for 60 minutes, then add the preheated billet into an extrusion cylinder at 730℃ for extrusion. The extrusion ratio (the ratio of the extrusion cylinder area to the product interface area) is 300:1, and the extrusion rod advance speed is 10mm / s. The extruded bar is cooled to room temperature (25℃) under an argon protective atmosphere to obtain the bar. The bar is then subjected to deep cryogenic treatment in liquid nitrogen at -196℃ for 10 hours and then naturally heated to room temperature (25℃). S4: The bar stock is drawn in multiple passes. In this embodiment, three passes are used. The first pass has an inlet diameter of 9.0 mm and an outlet diameter of 6.0 mm; the second pass has an inlet diameter of 6 mm and an outlet diameter of 3.5 mm; and the third pass has an inlet diameter of 3.5 mm and an outlet diameter of 2 mm. After the first and second passes, annealing is performed under a vacuum of 5 × 10⁻⁶. - 3 Pa, annealing temperature is 550℃, holding time is 1.5h, and then furnace cooled to 300℃ to obtain wire with a diameter of 2.0mm.

[0033] Comparative Example 2 A silver-tin oxide electrical contact material for magnetic latching relays differs from Example 1 in that it uses zirconium oxide powder of equal mass instead of yttrium-stabilized tetragonal zirconium oxide; the rest is the same as in Example 1.

[0034] Example 2 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that tungsten oxide is used instead of copper oxide; the rest is the same as in Example 1.

[0035] Example 3 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that copper oxide is not added; the rest is the same as Example 1.

[0036] Example 4 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the coating powder is derived from Preparation Example 2; the rest is the same as in Example 1.

[0037] Example 5 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the coating powder is derived from Preparation Example 3; the rest is the same as in Example 1.

[0038] Example 6 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the coating powder is derived from Preparation Example 4; the rest is the same as in Example 1.

[0039] Example 7 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the coating powder is derived from Preparation Example 5; the rest is the same as in Example 1.

[0040] Example 8 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that it does not undergo plasma treatment; the rest is the same as Example 1.

[0041] Example 9 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that: the copper oxide content is 0.5 kg; the rest is the same as in Example 1.

[0042] Example 10 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that: the amount of copper oxide is 2 kg; the rest is the same as in Example 1.

[0043] Example 11 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the copper oxide content is 0.3 kg; the rest is the same as in Example 1.

[0044] Example 12 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that: the copper oxide content is 2.3 kg; the rest is the same as in Example 1.

[0045] Example 13 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the extrusion temperature in step S2 is 700°C; the rest is the same as in Example 1.

[0046] Example 14 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the extrusion temperature in step S2 is 750°C; the rest is the same as in Example 1.

[0047] Example 15 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the extrusion temperature in step S2 is 650°C; the rest is the same as in Example 1.

[0048] Example 16 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the extrusion temperature in step S2 is 800°C; the rest is the same as in Example 1.

[0049] Example 17 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that: step S2 is not cooled with liquid nitrogen; the rest is the same as Example 1.

[0050] Example 18 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the annealing temperature in step S3 is 500°C; the rest is the same as in Example 1.

[0051] Example 19 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the annealing temperature in step S3 is 600°C; the rest is the same as in Example 1.

[0052] Example 20 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the annealing temperature in step S3 is 450°C; the rest is the same as in Example 1.

[0053] Example 21 A silver-tin oxide electrical contact material for use in magnetic latching relays differs from Example 1 in that the annealing temperature in step S3 is 650°C; the rest is the same as in Example 1.

[0054] Example 22 A silver-tin oxide electrical contact material for use in magnetic latching relays: prepared from the following components by weight: 100 kg of coating powder, 2 kg of yttrium-stabilized tetragonal zirconium oxide, and 0.2 kg of copper oxide, wherein the coating powder is derived from preparation example 6.

[0055] Its preparation method is as follows: S1: The coated powder was plasma-treated in 200W argon plasma for 15 minutes. The coated powder and copper oxide were then added to a mixer and mixed at 200 rpm for 3 hours to obtain a composite powder. The composite powder was then loaded into a graphite mold and transferred to a vacuum hot pressing sintering furnace. The furnace cavity was evacuated to 1×10⁻⁶. -2 Pa, heated to 700℃ at a rate of 12℃ / min, then a pressure of 25MPa was applied, and the temperature and pressure were maintained for 1 hour. Heating was then stopped, and the furnace body was allowed to cool naturally to 200℃. The pressure was then released to obtain the billet. S2: Preheat the billet at 700℃ for 60 minutes, then add the preheated billet into an extrusion cylinder at 730℃ for extrusion. The extrusion ratio is 200:1, and the extrusion rod advance speed is 10mm / s. The extruded bar is cooled to room temperature (25℃) under an argon protective atmosphere to obtain the bar. The bar is then placed in a -196℃ liquid nitrogen cryogenic treatment for 10 hours and naturally heated to room temperature (25℃). S3: The bar stock is drawn in multiple passes. In this embodiment, three passes are used. The first pass has an inlet diameter of 9.0 mm and an outlet diameter of 6.0 mm; the second pass has an inlet diameter of 6 mm and an outlet diameter of 3.5 mm; and the third pass has an inlet diameter of 3.5 mm and an outlet diameter of 2 mm. After the first and second passes, annealing is performed under a vacuum of 5 × 10⁻⁶. - 3 Pa, annealing temperature is 550℃, holding time is 1h, and then furnace cooling is carried out to 300℃ to obtain wire with a diameter of 2.0mm.

[0056] Example 23 A silver-tin oxide electrical contact material for use in magnetic latching relays is prepared from the following components by weight: 100 kg of coating powder, 5 kg of yttrium-stabilized tetragonal zirconium oxide, and 2 kg of copper oxide. The coating powder is derived from Preparation Example 7.

[0057] Its preparation method is as follows: S1: The coated powder was plasma-treated in 200W argon plasma for 15 minutes. The coated powder and copper oxide were then added to a mixer and mixed at 200 rpm for 3 hours to obtain a composite powder. The composite powder was then loaded into a graphite mold and transferred to a vacuum hot pressing sintering furnace. The furnace cavity was evacuated to 1×10⁻⁶. -2 Pa, heated to 800℃ at a rate of 12℃ / min, then a pressure of 35MPa was applied, and the temperature and pressure were maintained for 2 hours. Heating was then stopped, and the furnace body was allowed to cool naturally to 200℃. The pressure was then released to obtain the billet. S2: Preheat the billet at 700℃ for 60 minutes, then add the preheated billet into an extrusion cylinder at 730℃ for extrusion. The extrusion ratio is 400:1, and the extrusion rod feed speed is 10mm / s. The extruded bar is cooled to room temperature (25℃) under an argon protective atmosphere to obtain the bar. The bar is then placed in a -196℃ liquid nitrogen cryogenic treatment for 10 hours and naturally heated to room temperature (25℃). S3: The bar stock is drawn in multiple passes. In this embodiment, three passes are used. The first pass has an inlet diameter of 9.0 mm and an outlet diameter of 6.0 mm; the second pass has an inlet diameter of 6 mm and an outlet diameter of 3.5 mm; and the third pass has an inlet diameter of 3.5 mm and an outlet diameter of 2 mm. After the first and second passes, annealing is performed under a vacuum of 5 × 10⁻⁶. - 3 Pa, annealing temperature is 550℃, holding time is 2h, and then furnace cooled to 300℃ to obtain wire with a diameter of 2.0mm.

[0058] Examples 1-23 and Comparative Examples 1-2 were tested, and the results are as follows: The volume resistivity of Examples 1-23 and Comparative Examples 1-2 was tested according to GB / T 15078-2021 "Method for Measurement of Contact Resistance of Precious Metal Electrical Contact Materials". The volume resistivity of the electrical contact materials of Examples 1-23 and Comparative Examples 1-22 was measured after heating to 150°C and holding for 1 hour and then naturally cooling to 25°C. The sample was a wire with an original gauge length of 100 mm and a diameter of 2 mm. The test temperature was 25°C, and the test was conducted under DC current conditions of 50 mA, open circuit voltage of 1 V, and static contact pressure of 100 cN. The increase rate of volume resistivity was calculated, and the measurement results are shown in Table 1.

[0059] Table 1. Detection results of volume resistivity and increase rate of volume resistivity

[0060] Table 1. Detection results of volume resistivity and increase rate of volume resistivity (continued)

[0061] Examples 1-23 and Comparative Examples 1-2 were all processed into rivet contacts of 3×0.8+1.5×1.5R8 and 3×0.8+1.5×1.5F, respectively, and were assembled on a simulated electrical performance testing machine as moving and stationary contacts for relay simulated electrical life test. The test conditions are shown in Table 2, and the test results are shown in Table 3.

[0062] Table 2 Simulated Electrical Performance Test Conditions

[0063] Table 3 Results of Relay Simulated Electrical Life Test

[0064] Based on Tables 1 and 3, the analyses of Examples 1-23 and Comparative Examples 1-2 are as follows: Comparing Example 1 and Comparative Example 1, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact material in Example 1 are both less than those of the electrical contact material in Comparative Example 1. The electrical lifetime of the electrical contact material in Example 1 is greater than that of the electrical contact material in Comparative Example 1.

[0065] The difference between Example 1 and Comparative Example 1 is that: in Example 1, the electrical contact material is coated with indium oxide, tin oxide and silver using physical vapor deposition; indium oxide and tin oxide are deposited on the silver surface using physical vapor deposition, so that the oxide particles are more uniformly dispersed in the silver matrix; it can be seen that it is necessary to use physical vapor deposition to coat indium oxide, tin oxide and silver into powder for the electrical contact material.

[0066] Comparing Example 1 and Comparative Example 2, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact material in Example 1 are both less than those of the electrical contact material in Comparative Example 2. The electrical lifetime of the electrical contact material in Example 1 is greater than that of the electrical contact material in Comparative Example 2.

[0067] The difference between Example 1 and Comparative Example 2 is that yttrium-stabilized tetragonal zirconium oxide was added to the electrical contact in Example 1. Yttrium-stabilized tetragonal zirconium oxide can inhibit arc erosion, maintain chemical stability under the instantaneous high temperature of the arc, and the yttrium-stabilized tetragonal zirconium oxide uniformly dispersed in the silver matrix can effectively pin grain boundaries and dislocations, hinder grain boundary migration, maintain fine grain structure, and facilitate arc dispersion and energy dissipation. It can be seen that the addition of yttrium-stabilized tetragonal zirconium oxide to the electrical contact is necessary.

[0068] Comparing Examples 1-2 and Example 3, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact materials in Examples 1-2 are both less than those of the electrical contact materials in Example 3. The electrical lifetime of the electrical contact materials in Examples 1-2 is also greater than that of the electrical contact materials in Example 3.

[0069] The difference between Examples 1-2 and Example 3 is that tungsten oxide or copper oxide was added to the electrical contact material in Examples 1-2. Copper oxide or tungsten oxide forms a high-melting-point compound at high temperatures, which inhibits local melting at the root of the arc and improves the wettability and bonding force between silver and oxides. This makes the surface oxide layer formed under arc ablation denser, stronger, and less prone to peeling. Tungsten oxide has a high electron work function, which can improve the overall electron work function of the material, making the arc energy more dispersed. Tungsten oxide particles undergo local sintering with other oxides to generate a more heat-resistant composite oxide surface layer. It can be seen that adding tungsten oxide or copper oxide to the electrical contact material is superior.

[0070] Comparing Examples 1 and 4-7, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact material in Example 1 are both less than those of the electrical contact materials in Examples 4-7, and the electrical lifetime of the electrical contact material in Example 1 is greater than that of the electrical contact materials in Examples 4-7. Furthermore, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact materials in Examples 4-5 are both less than those of the electrical contact materials in Examples 6-7, and the electrical lifetime of the electrical contact materials in Examples 4-5 is greater than that of the electrical contact materials in Examples 6-7.

[0071] The difference between Examples 1, 4-5, and 6-7 is that the deposition temperature during the preparation of the electrical contact material coating powder in Examples 1 and 3-4 is 180-190℃. At this temperature, the deposited atoms have sufficient migration energy to form a dense and firmly bonded coating layer, avoiding interface defects, ensuring the interfacial bonding strength between the oxide and silver powder, and enhancing arc erosion resistance, contact resistance stability, and conductivity. Therefore, a deposition temperature of 180-190℃ is preferred for the preparation of the electrical contact material coating powder.

[0072] Comparing Examples 1 and 8, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact material in Example 1 are both less than those of the electrical contact material in Example 8. The electrical lifetime of the electrical contact material in Example 1 is greater than that of the electrical contact material in Example 8.

[0073] The difference between Example 1 and Example 8 is that: in Example 1, the electrical contact material is subjected to plasma treatment of the coated powder; at this temperature, the deposited atoms have sufficient migration energy to form a dense and firmly bonded coating layer, avoiding interface defects, ensuring the interfacial bonding strength between the oxide and the silver powder, and enhancing arc erosion resistance, contact resistance stability and conductivity; it can be seen that plasma treatment of the coated powder is superior for electrical contact materials.

[0074] Comparing Examples 1 and 9-12, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact material in Example 1 are both less than those of the electrical contact materials in Examples 9-12, and the electrical lifetime of the electrical contact material in Example 1 is greater than that of the electrical contact materials in Examples 9-12. Similarly, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact materials in Examples 9-10 are both less than those of the electrical contact materials in Examples 11-12, and the electrical lifetime of the electrical contact materials in Examples 9-10 is greater than that of the electrical contact materials in Examples 11-12.

[0075] The difference between Examples 1, 9-10, and 11-12 is that in Examples 1 and 9-10, the mass ratio of trace additives to coated powder in the composite powder of electrical contact materials is (0.5-2):100. This ratio ensures that the additives form a nanoscale dispersed phase without disrupting the continuity of the silver matrix. Furthermore, during the hot pressing process, copper oxide or tungsten oxide reacts with silver or oxides to generate a hard phase, which pins the grain boundaries and inhibits grain growth under arc erosion. Therefore, a mass ratio of trace additives to coated powder of (0.5-2):100 in the composite powder of electrical contact materials is preferred.

[0076] Comparing Examples 1 and 13-16, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact material in Example 1 are both less than those of the electrical contact materials in Examples 13-16, and the electrical lifetime of the electrical contact material in Example 1 is greater than that of the electrical contact materials in Examples 13-16. Similarly, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact materials in Examples 13-14 are both less than those of the electrical contact materials in Examples 15-16, and the electrical lifetime of the electrical contact materials in Examples 13-14 is greater than that of the electrical contact materials in Examples 15-16.

[0077] The difference between Examples 1, 13-14 and 15-16 is that: in Examples 1 and 13-14, the extrusion temperature of the electrical contact material in step S2 is 700-750℃; within this range, dynamic recrystallization is fully carried out, refining the grains while avoiding grain coarsening or zirconium oxide phase transformation. High-temperature plastic deformation promotes dislocation reorganization and texture formation, optimizes grain boundary distribution, and reduces grain boundary resistance; it can be seen that an extrusion temperature of 700-750℃ in step S2 of the electrical contact material is superior.

[0078] Comparing Example 1 and Example 17, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact material in Example 1 are both less than those of the electrical contact material in Example 17. Therefore, the electrical lifetime of the electrical contact material in Example 1 is greater than that of the electrical contact material in Example 17.

[0079] The difference between Example 1 and Example 17 is that: in Example 1, the rod material obtained in step S2 of the electrical contact material is cooled with liquid nitrogen; the deep cryogenic treatment of liquid nitrogen, by means of thermal shrinkage effect, generates compressive stress inside the material, refines the grains, increases dislocation density, stabilizes oxidation, reduces residual stress, improves resistance to arc erosion and stabilizes contact resistance; it can be seen that the rod material obtained in step S2 of the electrical contact material is cooled with liquid nitrogen.

[0080] Comparing Examples 1 and 18-21, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact material in Example 1 are both less than those of the electrical contact materials in Examples 18-19, and the electrical lifetime of the electrical contact material in Example 1 is greater than that of the electrical contact materials in Examples 18-19. Similarly, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact materials in Examples 18-19 are both less than those of the electrical contact materials in Examples 20-21, and the electrical lifetime of the electrical contact materials in Examples 18-19 is greater than that of the electrical contact materials in Examples 20-21.

[0081] The difference between Examples 1, 18-19 and 20-21 is that the annealing temperature of step S3 for the electrical contact material in Examples 1 and 18-19 is 500-600℃. This temperature range can effectively eliminate internal stress and dislocations caused by drawing, promote recovery and recrystallization to form stable grain boundaries, avoid excessive grain growth, ensure uniform size, reduce grain boundary scattering, stabilize oxides, improve resistance to arc erosion, optimize conductivity, and stabilize contact resistance. It can be seen that an annealing temperature of 500-600℃ in step S3 for the electrical contact material is superior.

[0082] Comparing Examples 1 and 22-23, the initial volume resistivity and the rate of increase in volume resistivity after heating of the electrical contact material in Example 1 are both less than those of the electrical contact materials in Examples 22-23, and the electrical lifetime of the electrical contact material in Example 1 is greater than that of the electrical contact material in Examples 22-23.

[0083] The difference between Example 1 and Examples 22-23 is as follows: In Example 1, the mass ratio of the electrical contact material coating powder, yttrium-stabilized tetragonal zirconium oxide, and copper oxide powder is 100:4:9. The coating powder contains 0.5 wt% indium oxide, 9 wt% tin oxide, and the balance is silver. In step S1, the composite powder is hot-pressed at 750°C to obtain a blank, with a pressure of 30 MPa and a holding time of 1.5 h. In step S2, the extrusion ratio is 300:1. In step S3, each retraction... The annealing time is 1.5h. It can be seen that the mass ratio of the coating powder, yttrium-stabilized tetragonal zirconium oxide and copper oxide powder of the electrical contact material is 100:4:9. In the coating powder, the indium oxide content is 0.5wt%, the tin oxide content is 9wt%, and the balance is silver. In step S1, the composite powder is hot-pressed at 750℃ to obtain the blank, the pressure is 30MPa, and the holding time is 1.5h. In step S2, the extrusion ratio is 300:1. In step S3, the annealing time for each step is 1.5h, which is more optimal.

[0084] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of protection claimed by the present invention, they are protected by patent law.

Claims

1. A method for preparing silver-tin oxide electrical contact material for use in magnetic latching relays, characterized in that, Includes the following steps: S1: The coated powder, yttrium-stabilized tetragonal zirconium oxide and trace additives are mixed to obtain a composite powder. The trace additives are copper oxide or tungsten oxide. The mass ratio of yttrium-stabilized tetragonal zirconium oxide to coated powder is (2~5):

100. The composite powder is hot-pressed at 700~800℃ to obtain a blank. The pressure is 25~35MPa and the holding time is 1~2h. S2: The billet is processed into bars using a hot extrusion process, with an extrusion ratio of (200~400):1; S3: The wire is produced by multiple drawing processes, and intermediate annealing is performed during the drawing process, with each annealing time being 1~2 hours; The coated powder is obtained by sequentially depositing indium oxide and tin oxide on the surface of silver powder using physical vapor deposition. The coated powder contains 0.3-0.8 wt% indium oxide, 8-10 wt% in tin oxide, and the balance is silver.

2. The method for preparing a silver-tin oxide electrical contact material for a magnetic latching relay according to claim 1, characterized in that, The deposition temperature in the preparation of the coated powder is 180~190℃.

3. The method for preparing a silver-tin oxide electrical contact material for a magnetic latching relay according to claim 1, characterized in that, In step S1, before mixing the coated powder, yttrium-stabilized tetragonal zirconia, and trace additives, the coated powder is subjected to plasma treatment, which is carried out under an argon atmosphere.

4. The method for preparing a silver-tin oxide electrical contact material for a magnetic latching relay according to claim 1, characterized in that, The mass ratio of trace additives to coated powder in the composite powder of step S1 is (0.5~2):

100.

5. The method for preparing a silver-tin oxide electrical contact material for a magnetic latching relay according to claim 1, characterized in that, The extrusion temperature in step S2 is 700~750℃.

6. The method for preparing a silver-tin oxide electrical contact material for a magnetic latching relay according to claim 1, characterized in that, After obtaining the rod in step S2, the rod is placed in liquid nitrogen at -196°C for cooling for 8~12 hours.

7. The method for preparing a silver-tin oxide electrical contact material for a magnetic latching relay according to claim 1, characterized in that, The annealing temperature in step S3 is 500~600℃.

8. A silver-tin oxide electrical contact material for use in magnetic latching relays, obtained by the preparation method according to any one of claims 1 to 7.

Images