An arc-erosion-resistant copper-silver contact alloy and a method for preparing the same

Abstract

This application relates to the field of electrical contact materials technology, and discloses an arc-erosion resistant copper-silver contact alloy and its preparation method. The method includes mixing silver nitrate, copper nitrate trihydrate, yttrium nitrate hexahydrate, ethylenediaminetetraacetic acid (EDTA), and ammonia to obtain a fully ammonium-state, double-complexed, homogeneous initial mother liquor; pumping ammonium bicarbonate aqueous solution into the fully ammonium-state, double-complexed, homogeneous initial mother liquor and injecting anhydrous ethanol for dynamic coupling co-precipitation; washing with an ethanol-water mixture and anhydrous ethanol and vacuum drying to obtain precursor powder; and after oxidative calcination and hydrogen reduction, cold isostatic pressing and solid-phase densification sintering to obtain the arc-erosion resistant copper-silver contact alloy. This invention avoids the introduction of alkali metal impurities, eliminates the risk of arc reignition, achieves uniform co-precipitation of multi-component metal ions, suppresses the outward splashing of liquid metal, and improves the density and arc-erosion resistance of the arc-erosion resistant copper-silver contact alloy.

Description

Technical Field

[0001] This invention relates to the field of electrical contact materials technology, specifically to an arc-erosion resistant copper-silver contact alloy and its preparation method. Background Technology

[0002] Arc-erosion resistant copper-silver contact alloys are widely used in various low-voltage electrical switches and contactors, serving to connect and disconnect circuits. Currently, the preparation of arc-erosion resistant copper-silver contact alloys usually adopts the chemical co-precipitation method. However, the existing co-precipitation process usually uses sodium-containing reagents for acid-base neutralization or precipitation reactions, which inevitably introduces alkali metal impurities. The low ionization potential alkali metal impurities undergo thermal ionization under the high temperature conditions of the arc generated by the opening and closing of the contacts, causing the arc to reignite and shortening the electrical life of the arc-erosion resistant copper-silver contact alloy.

[0003] Due to the differences in solubility products of silver, copper, and rare earth ions in aqueous solutions, conventional co-precipitation processes cannot control the simultaneous precipitation of multiple metal ions, resulting in variations in the crystallization precipitation sequence. This leads to component segregation and insulating phase agglomeration within the arc-erosion resistant copper-silver contact alloy. The coarsening of the insulating phase particles not only causes fluctuations in contact resistance but also reduces the macroscopic viscosity of the molten pool, causing the arc-erosion resistant copper-silver contact alloy to vaporize and sputter when subjected to high-temperature arc bombardment. Furthermore, conventional aqueous washing and drying processes, due to the high surface tension of water, generate capillary contraction during water evaporation, promoting hard agglomeration of the precursor powder. This makes it difficult to achieve high density in subsequent powder pressing and sintering processes, thereby reducing the conductivity and arc-erosion resistance of the arc-erosion resistant copper-silver contact alloy. Therefore, this invention proposes an arc-erosion resistant copper-silver contact alloy and its preparation method to address the shortcomings of existing technologies. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an anti-arc ablation copper-silver contact alloy and its preparation method, which solves the problems of traditional anti-arc ablation copper-silver contact alloys being prone to introducing alkali metal impurities during preparation, causing arc reignition, and the differences in precipitation sequence of multi-component metal ions during co-precipitation leading to component segregation and insulating phase agglomeration.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides an arc-erosion resistant copper-silver contact alloy, employing the following technical solution: An arc-erosion resistant copper-silver contact alloy comprises an alloy entity prepared from a fully ammonium-state double-complexed homogeneous initial state mother liquor through dynamic coupling co-precipitation, washing, vacuum drying, oxidative calcination, hydrogen reduction, and solid-phase densification sintering. The raw materials for preparing the fully ammonium-state double-complexed homogeneous initial state mother liquor include deionized water, silver nitrate, copper nitrate trihydrate, yttrium nitrate hexahydrate, ethylenediaminetetraacetic acid free acid, and ammonia. The reagents used in dynamic coupling coprecipitation include aqueous ammonium bicarbonate solution and anhydrous ethanol; The reagents used for washing include an ethanol-water mixture and anhydrous ethanol.

[0006] By adopting the above technical solution, the use of ethylenediaminetetraacetic acid (EDTA) free acid and ammonia water to replace conventional sodium-containing salts for in-situ acid-base neutralization and complexation reactions avoids the introduction of alkali metal cations such as sodium ions. The ammonium ions generated after the neutralization of EDTA free acid and ammonia water, as well as all associated nitrogen- and hydrocarbon-containing coordination groups, are volatile and completely decompose into ammonia, carbon dioxide, and water vapor in the subsequent oxidative roasting stage, which then volatilize. The pure grain boundary environment without alkali metal residues avoids the thermal ionization of low-ionization potential impurities under the high temperature of the electric arc, generating secondary electrons and positive... Ions block the formation of conductive plasma channels within the contact gap, eliminating arc reignition and improving the arc erosion resistance of the anti-arc ablation copper-silver contact alloy under an electric field environment. Simultaneously, dynamic coupling co-precipitation enables uniform mixing of silver, copper, and yttrium at the molecular level. The resulting yttrium oxide particles can increase the macroscopic viscosity of the molten copper-silver pool when bombarded by an arc, resisting the mechanical blowing force generated by the expansion of the arc plasma, suppressing the outward splashing behavior of liquid metal, and reducing the mass loss rate of the anti-arc ablation copper-silver contact alloy.

[0007] Preferably, the raw material ratio range for preparing the fully ammonium-state dual-complex homogeneous initial state mother liquor is: Silver nitrate 0.80–0.95 mol; Copper nitrate trihydrate 0.045–0.15 mol; Yttrium nitrate hexahydrate 0.005–0.05 mol; Ethylenediaminetetraacetic acid free acid 0.0525~0.24mol.

[0008] By adopting the above technical solution, the defined molar ratio of silver nitrate, copper nitrate trihydrate and yttrium nitrate hexahydrate ensures that the volume fraction of the conductive matrix and the ablation-resistant dispersed phase in the arc-resistant copper-silver contact alloy is in equilibrium. The amount of ethylenediaminetetraacetic acid added is sufficient to completely complex copper ions and yttrium ions in the mixture, forming a stable homogeneous fluid barrier with a high coordination constant, preventing stepwise hydrolysis or precipitation of metal ions.

[0009] Preferably, solid-phase densification sintering is carried out under nitrogen protection.

[0010] By adopting the above technical solution, nitrogen protection isolates the copper matrix from the conditions for oxidation-reduction reaction with ambient oxygen under high temperature, prevents the formation of copper oxide insulating phase inside the alloy green billet, ensures that the arc-erosion resistant copper-silver contact alloy after densification maintains the original free electron transport network, and guarantees the macroscopic conductivity of the arc-erosion resistant copper-silver contact alloy.

[0011] Secondly, the present invention provides a method for preparing an arc-erosion resistant copper-silver contact alloy, employing the following technical solution: A method for preparing an arc-erosion resistant copper-silver contact alloy includes the following steps: Ethylenediaminetetraacetic acid (EDTA) free acid was suspended and added to deionized water. Ammonia was added dropwise until the EDTA free acid was completely dissolved, resulting in a tetraammonium EDTA solution. Silver nitrate, copper nitrate trihydrate, and yttrium nitrate hexahydrate were added to the tetraammonium EDTA solution. After complete dissolution, the solution was heated in a cyclic heating system at a constant temperature. Ammonia was added dropwise to adjust the pH of the complexed mixture, resulting in a fully ammonium-state double-complexed homogeneous initial state mother liquor. Ammonium bicarbonate aqueous solution was continuously pumped into the initial homogeneous mother liquor of the ammonium-state dual complex to carry out dynamic coupling coprecipitation, so that the pH value of the complex mixture decreased linearly. When the pH value of the complex mixture dropped to the first pH value range, anhydrous ethanol was injected while the ammonium bicarbonate aqueous solution was continuously pumped in until the pH value of the complex mixture dropped to the second pH value range and the volume fraction of anhydrous ethanol in the complex mixture reached the preset volume fraction range. The mixture was then kept warm and aged to obtain a coprecipitation precursor suspension slurry. Solid-liquid separation was performed on the coprecipitation precursor suspension slurry to obtain a wet filter cake of the coprecipitation precursor. The wet filter cake of the coprecipitation precursor was washed sequentially with an ethanol-water mixture and anhydrous ethanol, and then vacuum dried to obtain a multi-metal carbonate mixed precursor powder. Multi-metal carbonate mixed precursor powder is oxidized and calcined in air to obtain mixed oxide phase powder. The mixed oxide phase powder is then reduced in hydrogen atmosphere to obtain reduced composite powder. The reduced composite powder was cold isostatically pressed to obtain an alloy green blank, and the alloy green blank was solidified and sintered to obtain an arc-erosion resistant copper-silver contact alloy.

[0012] By adopting the above technical solution, the preparation method of the arc-erosion resistant copper-silver contact alloy contains a clear chemical principle and reaction process, the specific mechanism of which is described below: The first stage: Ethylenediaminetetraacetic acid (EDTA) is a solid powder that is sparingly soluble in water. By adding ammonia, an in-situ acid-base neutralization reaction occurs, generating water-soluble EDTA tetraammonium. After adding silver nitrate, copper nitrate trihydrate, and yttrium nitrate hexahydrate, silver ions combine with ammonia molecules to form silver ammonia complex ions. Copper ions and yttrium ions are deeply chelated by the EDTA tetraammonium provided by EDTA tetraammonium, forming copper-EDTA complex ions and yttrium-EDTA complex ions with high stability constants. The multi-metal ions are locked in the aqueous phase by the complexation and shielding barrier, and cannot spontaneously precipitate according to their own solubility product constant.

[0013] The second stage involves continuously pumping in ammonium bicarbonate aqueous solution to linearly decrease the pH of the initial homogeneous mother liquor in the ammonium state double complex. At this point, a chemical decomplexation driving force is generated in the system. When the first pH range is reached, anhydrous ethanol is injected with a delay. Anhydrous ethanol, as a low-polarity antisolvent, reduces the solvent polarity and destroys the polar hydration layer of the metal complex ions. This reduces the solubility product of the free metal ions combining with the carbonate ions provided by ammonium bicarbonate to form carbonate precipitates. The multiple interventions of chemical degradation and abrupt changes in physical dielectric constant eliminate the crystallization sequence differences of silver carbonate, copper carbonate, and yttrium carbonate, which originally had large differences in solubility product.

[0014] The third stage: The wet filter cake of the co-precipitated precursor produced by solid-liquid separation contains a large amount of liquid free water in its internal pores. It is washed with an ethanol-water mixture and anhydrous ethanol. The anhydrous ethanol replaces the residual water in the gaps between the micro particles. Since the surface tension of anhydrous ethanol is much lower than that of deionized water, and the ethanol and the residual water molecules form a low-boiling-point azeotropic mixture, the capillary contraction force is reduced when the ethanol vaporizes and volatilizes during the vacuum drying process, which prevents the primary particles from hard agglomerating. This results in the final multi-metal carbonate mixed precursor powder having free-flowing characteristics and high bulk density.

[0015] In the fourth stage, during the oxidation roasting and hydrogen reduction process, carbonates decompose into oxides upon heating. Subsequently, silver oxide and copper oxide are reduced by hydrogen to metallic silver and metallic copper. However, yttrium oxide has a low enthalpy of formation and cannot be reduced by hydrogen. The non-agglomerated powder state ensures that yttrium oxide particles are uniformly distributed in a nanoscale dispersed state in the copper-silver alloy matrix. In the subsequent cold isostatic pressing and solid-phase densification sintering processes, the dispersed yttrium oxide particles pin the grain boundary sliding, eliminating residual pores inside the alloy green blank. Due to the fine and uniform yttrium oxide phase, the grain boundary scattering effect on the free electron transport path inside the metal is reduced. Finally, the arc-resistant copper-silver contact alloy achieves a combination of high Vickers hardness and high macroscopic conductivity.

[0016] Preferably, the constant temperature range is 60-75℃, and ammonia water is added dropwise to adjust the pH value of the mixture to 11.0-12.0.

[0017] By adopting the above technical solution, the thermodynamic conditions of 60-75℃ ensure that the coordination reaction between the multi-component metal salt and tetraammonium ethylenediaminetetraacetic acid is carried out completely. The pH value is adjusted to a highly alkaline range of 11.0-12.0, which ensures that the silver ammonia complex ions remain stable under this thermodynamic condition. This avoids the premature precipitation of free metal ions during the standing or pipeline transportation stage, and ensures the uniformity of the initial mother liquor.

[0018] Preferably, the concentration range of the ammonium bicarbonate aqueous solution is 1.5 mol / L to 2.5 mol / L, and the pH decrease rate of the coprecipitation mixture is 0.15 pH / min to 0.25 pH / min.

[0019] By adopting the above technical solution, the supply concentration of carbonate ions is correlated with the rate of decrease in solution pH, which ensures stable release of supersaturation during precipitation. The uniform decomposition rate prevents abnormal grain growth caused by local high concentration areas and ensures concentrated size distribution of primary coprecipitated nanoparticles.

[0020] Preferably, the first pH value range is 9.2 to 9.8, the second pH value range is 7.8 to 8.2, the preset volume fraction range is 35% to 45%, and the heat preservation and aging time range is 45 to 90 minutes.

[0021] By adopting the above technical solution, the first pH value range is set as the trigger point for the introduction of anhydrous ethanol, which prevents the metal complex from being directly precipitated due to the premature introduction of anhydrous ethanol, and at the same time prevents the silver carbonate from preferentially nucleating alone due to the premature introduction. The second pH value is defined as 7.8 to 8.2, and with an anhydrous ethanol volume fraction of 35% to 45%, the conversion reaction of all free metal ions from the liquid phase to the solid phase reaches its endpoint. The heat preservation and aging promotes the further maturation of the fine crystal embryos and the stabilization of the phase structure.

[0022] Preferably, the volume fraction of ethanol in the ethanol-water mixture is in the range of 35% to 45%, the vacuum degree of vacuum drying is in the range of 0.08 MPa to 0.1 MPa, the temperature of vacuum drying is in the range of 70 to 90°C, and the time of vacuum drying is in the range of 10 to 14 hours.

[0023] By adopting the above technical solution, washing with a mixture of ethanol and water with matching volume fractions maintains the osmotic pressure balance inside and outside the filter cake, preventing the back dissolution of the precipitated particles. The vacuum negative pressure environment combined with a drying temperature of 70-90℃ utilizes the azeotropic volatility of water-ethanol to remove the binding solvent in the micropores in a short time, cuts off the liquid bridge between particles, and maintains the micro-dispersion state of the precursor powder.

[0024] Preferably, the heating rate of the oxidation roasting is in the range of 2℃ / min to 5℃ / min, the temperature range of the oxidation roasting is 450℃ to 550℃, and the time range of the oxidation roasting is 1.5h to 3h; the heating rate of the hydrogen reduction is in the range of 3℃ / min to 5℃ / min, the temperature range of the hydrogen reduction is 400℃ to 500℃, and the time range of the hydrogen reduction is 1.5h to 3h.

[0025] By adopting the above technical solution, the gradual heating rate avoids the concentrated decomposition of carbonates, which generates a large amount of gas that breaks through the powder skeleton. Specific temperature and time parameters can decompose nitrogen-containing carbon-hydrogen coordination groups and release volatile gases. At the same time, the copper-silver phase is completely metallized during the hydrogen reduction stage, and the spatial dispersion of yttrium oxide particles is preserved, preventing the yttrium oxide particles from coarsening and growing.

[0026] Preferably, the pressure range of cold isostatic pressing is 400MPa to 600MPa, the temperature range of solid-phase densification sintering is 800℃ to 880℃, and the time range of solid-phase densification sintering is 3h to 6h.

[0027] By adopting the above technical solution, the highly free-flowing powder undergoes uniform plastic deformation and compaction under hydrostatic pressure of 400MPa to 600MPa, eliminating the internal local density gradient. Subsequently, solid-phase atomic diffusion sintering occurs at 800℃ to 880℃, and the material fills and closes the geometric voids, enabling the arc-erosion resistant copper-silver contact alloy to achieve high density and improving the macroscopic mechanical load-bearing capacity and continuous charge transport capability.

[0028] This invention provides an arc-erosion-resistant copper-silver contact alloy and its preparation method. It has the following beneficial effects: 1. This invention uses ethylenediaminetetraacetic acid (EDTA) free acid and ammonia water to replace sodium-containing reagents for in-situ neutralization and complexation reactions, avoiding the mixing of alkali metal impurities such as sodium ions into the interior of the arc-resistant copper-silver contact alloy. The alkali metal-free environment prevents the arc-resistant copper-silver contact alloy from generating low-ionization potential substances thermal ionization when subjected to high-temperature arc bombardment, cuts off the generation path of conductive plasma channels, eliminates the risk of arc reignition, and improves the arc-resistant copper-silver contact alloy's arc-resistant performance and electrical life.

[0029] 2. This invention achieves dynamic coupling co-precipitation by continuously pumping ammonium bicarbonate aqueous solution into the homogeneous initial state mother liquor of the all-ammonium state dual complex and injecting anhydrous ethanol. By utilizing the dual intervention of chemical decomplexation and physical polarity abrupt change, the difference in the crystallization sequence of silver, copper and yttrium elements in the formation of carbonate precipitates is eliminated, realizing the synchronous co-nucleation of multi-component metal ions. When the uniformly precipitated yttrium oxide particles form a liquid pool on the surface of the arc-resistant copper-silver contact alloy, they can increase the macroscopic viscosity of the melt, resist the mechanical blowing force generated by the expansion of the arc plasma, and suppress the outward splashing loss of liquid metal.

[0030] 3. This invention uses an ethanol-water mixture and anhydrous ethanol to wash the wet filter cake of the co-precipitated precursor and combines it with a vacuum drying process. By utilizing the low surface tension of anhydrous ethanol and the low-boiling-point azeotrope formed by anhydrous ethanol and residual water molecules, the capillary contraction force generated during the vaporization and evaporation of the liquid in the vacuum drying stage is reduced. The washing and vacuum drying process eliminates the conditions for hard agglomeration of primary particles, so that the multi-metal carbonate mixed precursor powder has high free flow characteristics. This ensures that the arc-resistant copper-silver contact alloy obtains high density and high conductivity after cold isostatic pressing and solid-phase densification sintering. Attached Figure Description

[0031] Figure 1 This is a schematic diagram comparing the absolute precipitation yield of metal elements according to the present invention; Figure 2 This is a schematic diagram comparing the residual sodium content in the contact alloy of the present invention; Figure 3 This is a schematic diagram comparing the fluidity of the present invention; Figure 4 This is a density comparison diagram of the present invention; Figure 5 This is a schematic diagram of the comparison between Hausner and Nabi in this invention; Figure 6 This is a schematic diagram showing the line comparison of the final alloy's macroscopic physical properties and electrical conductivity in this invention; Figure 7 This is a schematic diagram comparing the mass loss rate and the dynamic contact resistance range of the present invention. Figure 8 This is a schematic diagram comparing the arc reignition frequency of the present invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing a fully ammonium-state, dual-complex, homogeneous initial state mother liquor, including the following steps: 2000 mL of deionized water was injected into a continuously stirred reactor equipped with a jacketed temperature control and mechanical stirring device. The mechanical stirring was turned on and the speed was set to 300 rpm. 0.165 mol of ethylenediaminetetraacetic acid free acid was suspended and added to the deionized water. Ammonia water was slowly added dropwise until the ethylenediaminetetraacetic acid free acid was completely dissolved, thus obtaining a tetraammonium ethylenediaminetetraacetic acid solution.

[0034] While maintaining a stirring speed of 300 rpm, add 0.85 mol silver nitrate, 0.12 mol copper nitrate trihydrate, and 0.03 mol yttrium nitrate hexahydrate sequentially to the tetraammonium ethylenediaminetetraacetic acid solution. After the silver nitrate, copper nitrate trihydrate, and yttrium nitrate hexahydrate are completely dissolved, turn on the jacketed circulation heating to keep the fluid temperature in the continuously stirred reactor constant at 65°C.

[0035] Continue to slowly add ammonia water, and use an online pH meter to monitor the pH value of the complexed mixture in the continuously stirred reactor. The pH value of the complexed mixture in the continuously stirred reactor is precisely adjusted and kept constant at 11.5 to obtain the initial state mother liquor of the fully ammonium-state dual complex homogeneous state.

[0036] Preparation Example 2: This preparation example provides a method for preparing a fully ammonium-state, dual-complex, homogeneous initial state mother liquor, including the following steps: 2000 mL of deionized water was injected into a continuously stirred reactor equipped with a jacketed temperature control and mechanical stirring device. The mechanical stirring was turned on and the speed was set to 200 rpm. 0.0525 mol of ethylenediaminetetraacetic acid free acid was suspended and added to the deionized water. Ammonia water was slowly added dropwise until the ethylenediaminetetraacetic acid free acid was completely dissolved, thus obtaining a tetraammonium ethylenediaminetetraacetic acid solution.

[0037] While maintaining a stirring speed of 200 rpm, add 0.95 mol silver nitrate, 0.045 mol copper nitrate trihydrate, and 0.005 mol yttrium nitrate hexahydrate sequentially to the tetraammonium ethylenediaminetetraacetic acid solution. After the silver nitrate, copper nitrate trihydrate, and yttrium nitrate hexahydrate are completely dissolved, turn on the jacketed circulation heating to keep the fluid temperature in the continuously stirred reactor constant at 60°C.

[0038] Continue to slowly add ammonia water, and use an online pH meter to monitor the pH value of the complexed mixture in the continuously stirred reactor. The pH value of the complexed mixture in the continuously stirred reactor is precisely adjusted and kept constant at 12.0 to obtain the initial state mother liquor of the fully ammonium-state dual complexed homogeneous state.

[0039] Preparation Example 3: This preparation example provides a method for preparing a fully ammonium-state, dual-complex, homogeneous initial state mother liquor, including the following steps: 2000 mL of deionized water was injected into a continuously stirred reactor equipped with a jacketed temperature control and mechanical stirring device. The mechanical stirring was turned on and the speed was set to 400 rpm. 0.24 mol of ethylenediaminetetraacetic acid free acid was suspended and added to the deionized water. Ammonia water was slowly added dropwise until the ethylenediaminetetraacetic acid free acid was completely dissolved, thus obtaining a tetraammonium ethylenediaminetetraacetic acid solution.

[0040] While maintaining a stirring speed of 400 rpm, add 0.80 mol silver nitrate, 0.15 mol copper nitrate trihydrate, and 0.05 mol yttrium nitrate hexahydrate sequentially to the tetraammonium ethylenediaminetetraacetic acid solution. After the silver nitrate, copper nitrate trihydrate, and yttrium nitrate hexahydrate are completely dissolved, turn on the jacketed circulation heating to keep the fluid temperature in the continuously stirred reactor constant at 75°C.

[0041] Continue to slowly add ammonia water, and use an online pH meter to monitor the pH value of the complexed mixture in the continuously stirred reactor. The pH value of the complexed mixture in the continuously stirred reactor is precisely adjusted and kept constant at 11.0 to obtain the initial state mother liquor of the fully ammonium-state dual complex homogeneous state.

[0042] Examples 1-3: Example

[0043] This embodiment provides a method for preparing an arc-erosion resistant copper-silver contact alloy, comprising the following steps: Take the fully ammonium-state double-complex homogeneous initial state mother liquor obtained in Preparation Example 1, keep the jacket circulating heating temperature of the continuous stirred reactor constant at 65℃, adjust and keep the mechanical stirring speed constant at 400 rpm, start the precision metering pump of feed channel A, and continuously pump ammonium bicarbonate aqueous solution with a concentration of 2.0 mol / L and pre-saturated with carbon dioxide gas into the continuous stirred reactor, and adjust the flow rate of the precision metering pump of feed channel A so that the pH value of the coprecipitated mixture in the continuous stirred reactor decreases at a linear rate of -0.2 pH / min.

[0044] When the online pH meter detects that the pH value of the coprecipitation mixture in the continuous stirred reactor drops to 9.5, the precision metering pump in feed channel B is triggered to start. While the precision metering pump in feed channel A continues to operate, anhydrous ethanol is injected into the continuous stirred reactor through the precision metering pump in feed channel B in a non-linear incremental program. The flow ratio of the precision metering pumps in feed channel A and feed channel B is controlled so that when the pH value of the coprecipitation mixture in the continuous stirred reactor finally drops to 8.0, the volume fraction of anhydrous ethanol in the coprecipitation mixture in the continuous stirred reactor reaches 40%. The precision metering pumps in feed channel A and feed channel B are then stopped, and the mixture is aged at 65°C and a stirring speed of 400 rpm for 60 minutes to obtain the coprecipitation precursor suspension slurry.

[0045] The coprecipitation precursor suspension was fed into an industrial centrifuge for solid-liquid separation to obtain a wet filter cake of the coprecipitation precursor. The wet filter cake of the coprecipitation precursor was washed four times with a 40% (v / v) ethanol-water mixture, and then washed once with anhydrous ethanol. The washed wet filter cake of the coprecipitation precursor was transferred to a vacuum drying oven and dried for 12 hours under a vacuum of 0.09 MPa and a temperature of 80 °C to obtain a multi-metal carbonate mixed precursor powder.

[0046] Multi-metal carbonate mixed precursor powder was placed in a muffle furnace and heated to 500°C at a heating rate of 3°C / min under an air atmosphere. The powder was then held at 500°C for 2 hours to obtain mixed oxide phase powder. The mixed oxide phase powder was then transferred to a tube reduction furnace, and hydrogen gas with a purity of not less than 99.999% was introduced. The powder was heated to 450°C at a heating rate of 4°C / min and held at 450°C for 2 hours to obtain reduced composite powder.

[0047] The reduced composite powder was loaded into a flexible mold and cold isostatically pressed under a pressure of 500 MPa to obtain an alloy green billet. The alloy green billet was placed in a sintering furnace under nitrogen protection and solid-state densification sintering was carried out at 850°C for 4 hours to obtain an arc-resistant copper-silver contact alloy. Example

[0048] This embodiment provides a method for preparing an arc-erosion resistant copper-silver contact alloy, comprising the following steps: Take the fully ammonium-state double-complex homogeneous initial state mother liquor obtained in Preparation Example 2, keep the jacket circulating heating temperature of the continuous stirred reactor constant at 60°C, adjust and keep the mechanical stirring speed constant at 300 rpm, start the precision metering pump of feed channel A, and continuously pump ammonium bicarbonate aqueous solution with a concentration of 2.5 mol / L and pre-saturated with carbon dioxide gas into the continuous stirred reactor, and adjust the flow rate of the precision metering pump of feed channel A so that the pH value of the coprecipitated mixture in the continuous stirred reactor decreases at a linear rate of -0.25 pH / min.

[0049] When the online pH meter detects that the pH value of the coprecipitation mixture in the continuous stirred reactor drops to 9.8, the precision metering pump in feed channel B is triggered to start. While the precision metering pump in feed channel A continues to operate, anhydrous ethanol is injected into the continuous stirred reactor through the precision metering pump in feed channel B in a non-linear incremental program. The flow ratio of the precision metering pumps in feed channel A and feed channel B is controlled so that when the pH value of the coprecipitation mixture in the continuous stirred reactor finally drops to 8.2, the volume fraction of anhydrous ethanol in the coprecipitation mixture in the continuous stirred reactor reaches 35%. The precision metering pumps in feed channel A and feed channel B are then stopped, and the mixture is aged at 60°C and a stirring speed of 300 rpm for 90 minutes to obtain the coprecipitation precursor suspension slurry.

[0050] The coprecipitation precursor suspension was fed into an industrial centrifuge for solid-liquid separation to obtain a wet filter cake of the coprecipitation precursor. The wet filter cake of the coprecipitation precursor was washed three times with a 35% (v / v) ethanol-water mixture, and then washed twice with anhydrous ethanol. The washed wet filter cake of the coprecipitation precursor was transferred to a vacuum drying oven and dried for 10 hours under a vacuum of 0.1 MPa and a temperature of 90°C to obtain a multi-metal carbonate mixed precursor powder.

[0051] Multi-metal carbonate mixed precursor powder was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min under an air atmosphere. The powder was then held at 550°C for 1.5 h to obtain mixed oxide phase powder. The mixed oxide phase powder was then transferred to a tube reduction furnace, and hydrogen gas with a purity of not less than 99.999% was introduced. The powder was heated to 500°C at a heating rate of 5°C / min and held at 500°C for 1.5 h to obtain reduced composite powder.

[0052] The reduced composite powder was loaded into a flexible mold and cold isostatically pressed under a pressure of 600 MPa to obtain an alloy green billet. The alloy green billet was placed in a sintering furnace under nitrogen protection and solidified at 880°C for 3 hours to obtain an arc-resistant copper-silver contact alloy. Example

[0053] This embodiment provides a method for preparing an arc-erosion resistant copper-silver contact alloy, comprising the following steps: Take the fully ammonium-state double-complex homogeneous initial state mother liquor obtained in Preparation Example 3, keep the jacket circulating heating temperature of the continuous stirred reactor constant at 75°C, adjust and keep the mechanical stirring speed constant at 500 rpm, start the precision metering pump of feed channel A, and continuously pump ammonium bicarbonate aqueous solution with a concentration of 1.5 mol / L and pre-saturated with carbon dioxide gas into the continuous stirred reactor, and adjust the flow rate of the precision metering pump of feed channel A so that the pH value of the coprecipitated mixture in the continuous stirred reactor decreases at a linear rate of -0.15 pH / min.

[0054] When the online pH meter detects that the pH of the coprecipitated mixture in the continuous stirred reactor has dropped to 9.2, the precision metering pump in feed channel B is activated. While the precision metering pump in feed channel A continues to operate, anhydrous ethanol is injected into the continuous stirred reactor through the precision metering pump in feed channel B in a non-linear incremental program. The flow rate ratio of the precision metering pumps in feed channel A and feed channel B is controlled so that when the pH of the coprecipitated mixture in the continuous stirred reactor finally drops to 7.8, the volume fraction of anhydrous ethanol in the coprecipitated mixture reaches 45%. The precision metering pumps in feed channels A and B are then stopped, and the mixture is aged at 75°C with a stirring speed of 500 rpm for 45 minutes to obtain a coprecipitated precursor suspension slurry.

[0055] The coprecipitation precursor suspension was fed into an industrial centrifuge for solid-liquid separation to obtain a wet filter cake of the coprecipitation precursor. The wet filter cake of the coprecipitation precursor was washed five times with a 45% (v / v) ethanol-water mixture, and then washed once with anhydrous ethanol. The washed wet filter cake of the coprecipitation precursor was transferred to a vacuum drying oven and dried for 14 hours under a vacuum of 0.08 MPa and a temperature of 70°C to obtain a multi-metal carbonate mixed precursor powder.

[0056] The mixed precursor powder of multi-metal carbonates was placed in a muffle furnace and heated to 450°C at a heating rate of 2°C / min under an air atmosphere. It was then held at 450°C for 3 hours to obtain mixed oxide phase powder. The mixed oxide phase powder was then transferred to a tube reduction furnace, and hydrogen gas with a purity of not less than 99.999% was introduced. The furnace was heated to 400°C at a heating rate of 3°C / min and held at 400°C for 3 hours to obtain reduced composite powder.

[0057] The reduced composite powder was loaded into a flexible mold and cold isostatically pressed under a pressure of 400 MPa to obtain an alloy green billet. The alloy green billet was placed in a sintering furnace under nitrogen protection and solid-state densification sintering was carried out at 800°C for 6 hours to obtain an arc-resistant copper-silver contact alloy.

[0058] Comparative Examples 1-5: Comparative Example 1: Compared with Example 1, the difference is that the in-situ acid-base neutralization of ethylenediaminetetraacetic acid and ammonia water and the preparation of homogeneous mother liquor are not carried out. Instead, silver nitrate, copper nitrate trihydrate and yttrium nitrate hexahydrate are directly dissolved in deionized water to form a mixed metal salt pure aqueous solution. Then, only the precision metering pump of feed channel A is started to add ammonium bicarbonate aqueous solution dropwise to the mixed metal salt pure aqueous solution for conventional forward coprecipitation. Anhydrous ethanol is not injected throughout the reaction. Everything else is the same.

[0059] Comparative Example 2: Compared with Example 1, the difference is that in the preparation step of the all-ammonia double complex homogeneous initial state mother liquor, the free acid of ethylenediaminetetraacetic acid is replaced with an equimolar amount of disodium ethylenediaminetetraacetate, and sodium hydroxide aqueous solution is used instead of ammonia to adjust the pH value of the complex mixture, directly constructing an initial state mother liquor containing sodium ions. All other steps are the same.

[0060] Comparative Example 3: Compared with Example 1, the difference is that in the dynamic coupling coprecipitation reaction step, the delayed triggering mechanism is not used. Instead, the precision metering pumps of feed channel A and feed channel B are started simultaneously at the initial state barrier stage when the initial pH value of the coprecipitation mixture in the continuous stirred reactor is 11.5. That is, ammonium bicarbonate aqueous solution and anhydrous ethanol are added dropwise simultaneously from the initial high alkaline homogeneous state. The rest are the same.

[0061] Comparative Example 4: Compared with Example 1, the difference is that in the dynamic coupling coprecipitation reaction step, only the precision metering pump of feed channel A is started to continuously pump in ammonium bicarbonate aqueous solution to reduce the pH value of the coprecipitation mixture in the continuous stirring reactor. The precision metering pump of feed channel B is not started to inject anhydrous ethanol throughout the process, that is, the physical process of dynamic decay of dielectric constant is lacking. Everything else is the same.

[0062] Comparative Example 5: Compared with Example 1, the difference is that in the azeotropic displacement washing and drying steps, only deionized water is used to wash the wet filter cake of the coprecipitated precursor five times, and no ethanol-water mixture or anhydrous ethanol is used for washing and azeotropic displacement throughout the process. All other steps are the same.

[0063] Test Examples 1-5: Test Example 1: Quantitative Test of Metal Residue Rate and Powder Yield in Coprecipitation Liquid Phase Collect the centrifugal mother liquor discharged after solid-liquid separation in Examples 1 to 3 and Comparative Examples 1, 3 and 4 using an industrial centrifuge, and record the total volume of the centrifugal mother liquor.

[0064] Accurately transfer 10 mL of the centrifugal separation mother liquor, and filter the centrifugal separation mother liquor through a polytetrafluoroethylene microporous filter membrane with a pore size of 0.22 μm using a syringe to trap any tiny suspended particles that may exist in the centrifugal separation mother liquor, and obtain a clear test solution.

[0065] Transfer 1.0 mL of the clear test solution into a 100 mL volumetric flask, add 5% nitric acid aqueous solution to the 100 mL volumetric flask and dilute to the mark of the 100 mL volumetric flask, shake well, and the test solution for inductively coupled plasma atomic emission spectrometry is prepared.

[0066] The inductively coupled plasma atomic emission spectrometry (ICP-AES) instrument was used to measure the mass concentrations of silver ions, copper ions, and yttrium ions in the instrument.

[0067] The absolute precipitation yields of silver, copper, and yttrium were calculated by combining the total volume of the mother liquor from centrifugation with the total molar amount of the initially added metal salts.

[0068] Table 1. Absolute precipitation yield test results of silver, copper, and yttrium. Example 1 99.82 99.51 99.14 Example 2 99.75 99.38 98.87 Example 3 99.68 99.62 99.25 Comparative Example 1 98.15 86.42 72.31 Comparative Example 3 97.55 94.21 92.18 Comparative Example 4 98.63 65.47 41.22 Conclusions and Analysis: According to Table 1 and Figure 1 The data shows that the absolute precipitation yields of silver, copper, and yttrium in Examples 1, 2, and 3 all reached over 98.8%, and the yield values ​​of the three metal elements were basically consistent. This proves that the chemical fluid dynamics model coupled with the dynamic decay of dielectric constant and the hysteresis of pH gradient can effectively destroy the deep chelation state of copper and yttrium ions by ethylenediaminetetraacetic acid. The injection of anhydrous ethanol caused a sharp drop in the dielectric constant of the mixed solvent, which not only destroyed the polar hydration layer of the metal complex ions, but also caused the solubility product of the newly free metal ions and the carbonate ions provided by ammonium bicarbonate to form carbonate precipitates to decrease exponentially. This forced silver carbonate, copper carbonate, and yttrium carbonate, which have large differences in solubility product, to lose their independent crystallization sequence and undergo synchronous disordered co-nucleation at the mesoscale, ensuring the complete transformation of the three metal ions from the liquid phase to the solid phase.

[0069] In Comparative Example 4, no anhydrous ethanol was injected during the entire reaction process. The absolute precipitation yield of silver in Comparative Example 4 remained at 98.63%, but the absolute precipitation yields of copper and yttrium were as low as 65.47% and 41.22%, respectively. This proves that simply adding ammonium bicarbonate aqueous solution to lower the pH value to 8.0 is insufficient to break the high-intensity coordination equilibrium between copper ions, yttrium ions and ethylenediaminetetraacetic acid. Without the physical antisolvent suction provided by anhydrous ethanol, the simple chemical decomposition driving force is insufficient to induce the forced co-precipitation of polymetallic ions, resulting in a large amount of undissociated copper and yttrium ions being lost with the mother liquor from centrifugation.

[0070] Comparative Example 1 used conventional forward coprecipitation in pure aqueous phase without the addition of ethylenediaminetetraacetic acid (EDTA) free acid and anhydrous ethanol. In Comparative Example 1, the absolute precipitation yield of silver reached 98.15%, but the absolute precipitation yield of copper decreased to 86.42%, and the absolute precipitation yield of yttrium was as low as 72.31%. This indicates that under the conditions of lack of complexation shielding barrier and forced intervention of transient antisolvent environment, the three free metal ions precipitated stepwise according to their own solubility product constants. Silver carbonate precipitated first, while yttrium carbonate and copper carbonate precipitated later and incompletely, thus destroying the homogeneity of the multiphase components of the precursor powder.

[0071] Comparative Example 3 did not employ a delayed triggering mechanism. Ammonium bicarbonate aqueous solution and anhydrous ethanol were added simultaneously from the initial highly alkaline homogeneous state. Although the absolute precipitation yields of Comparative Example 3 were higher than those of Comparative Example 4, they were inferior to those of Examples 1 to 3. The above results indicate that introducing anhydrous ethanol too early will interfere with the chemical decomposition pathway, causing some stable metal complex salts to directly undergo physical precipitation, deviating from the target carbonate coprecipitation reaction trajectory. The physically precipitated metal complex salts underwent partial re-dissolution and loss during subsequent washing and centrifugation, proving the necessity of the synergistic regulation of the timing of chemical decomposition and physical antisolvent.

[0072] Test Example 2: Detection of Residual Alkali Metal Impurities in Precursors and Alloys Material from the central part of the arc-erosion resistant copper-silver contact alloy prepared in Examples 1 to 3 and Comparative Example 2 was cut off and processed into circular test samples with a diameter of 20 mm and a thickness of 2 mm by slow wire cutting technology.

[0073] The surface of the disc-shaped test sample was polished step by step with silicon carbide sandpaper of different grits until it was mirror-smooth. The polished disc-shaped test sample was then immersed in deionized water and anhydrous ethanol in turn, and ultrasonically cleaned for 15 minutes each to remove mechanical processing contaminants from the surface of the disc-shaped test sample.

[0074] The cleaned circular test samples were placed in a vacuum drying oven and dried at 60°C for 2 hours to obtain the target material for glow discharge mass spectrometry.

[0075] The test target material was loaded into the vacuum test chamber of the glow discharge mass spectrometer, and a vacuum was drawn until the pressure was below 1 × 10⁻⁶. -7 mbar, high-purity argon gas is introduced as the discharge gas, and the discharge voltage is set to 1kV and the discharge current is 2mA.

[0076] The surface of the test target was pre-sputtered for 5 minutes to remove the oxide layer and the adsorbate on the surface of the test target. Then the main data acquisition program was started to continuously acquire the mass spectrometry signal of the test target after sputtering and ionization, and the mass spectrometry peak intensity of sodium was recorded.

[0077] By combining the response factor of the internal standard element, the intensity of the collected sodium element mass spectrum peak is converted into an absolute mass fraction, and the residual sodium element value is read.

[0078] Table 2. Test results of sodium residual content in arc-erosion resistant copper-silver contact alloys Example 1 0.12 Example 2 0.08 Example 3 0.15 Comparative Example 2 158.42 Conclusions and Analysis: According to Table 2 and Figure 2 According to the data, the residual sodium content in the arc-erosion resistant copper-silver contact alloys prepared in Examples 1, 2 and 3 is at a low level, with test values ​​fluctuating between 0.08 ppm and 0.15 ppm, which is on the edge of the detection limit of the trace impurity analyzer. The residual sodium content in the arc-erosion resistant copper-silver contact alloy prepared in Comparative Example 2 is as high as 158.42 ppm.

[0079] In Examples 1 to 3, during the preparation stage of the homogeneous initial state mother liquor with double complexation in the all-ammonium state, an in-situ acid-base neutralization reaction was carried out with ethylenediaminetetraacetic acid (EDTA) free acid and ammonia water to generate EDTA tetraammonium solution. This eliminated the introduction of alkali metal cations from the reaction source. After EDTA tetraammonium completed the complexation of copper and yttrium ions and dissociated and precipitated carbonate precursors through the dielectric constant decay mechanism, the ammonium ions entered the subsequent heat treatment process along with the co-precipitated precursor wet filter cake. Since the ammonium ions and all associated nitrogen-containing hydrocarbon coordination groups have the thermodynamic property of volatilization, the ammonium ions and nitrogen-containing hydrocarbon coordination groups were completely decomposed into ammonia, carbon dioxide and water vapor and volatilized during the muffle furnace oxidation roasting stage, thus achieving the purification of the internal chemical composition of the arc-resistant copper-silver contact alloy.

[0080] Comparative Example 2 uses conventional disodium ethylenediaminetetraacetate as a complexing agent. Sodium ions exhibit a strong tendency for liquid-phase retention and grain boundary adsorption in the antisolvent precipitation system of water and ethanol. Even after repeated washing with deionized water and anhydrous ethanol, the sodium ions at the microscale are still inevitably encapsulated in the interstitial spaces of the multi-metal carbonate mixed precursor powder. The physically encapsulated sodium ions cannot volatilize during the oxidation roasting and hydrogen reduction process, and are eventually enriched inside the densified and formed arc-resistant copper-silver contact alloy.

[0081] Sodium ions remaining inside the arc-resistant copper-silver contact alloy have low ionization potential energy. When the arc-resistant copper-silver contact alloy performs a switching action in equipment such as contactors and is bombarded by a high-temperature arc, the high concentration of free sodium ions will rapidly undergo thermal ionization to generate a large number of secondary electrons and positive ions. The conductive plasma channel is reconstructed within the disconnected mechanical gap. The reconstruction of the conductive plasma channel will directly lead to the arc reignition phenomenon, prolong the arcing time and aggravate the material vaporization and splashing loss on the contact surface, thereby damaging the electrical insulation life of the arc-resistant copper-silver contact alloy. The all-ammonium state process path of Examples 1 to 3 eliminates the low ionization potential impurity defect and improves the arc-resistant copper-silver contact alloy's arc erosion resistance performance in an electric field environment.

[0082] Test Example 3: Evaluation of Macroscopic Physical Properties and Flow Properties of Precursor Powder 100g of reduced composite powder was placed in a vacuum drying oven and kept at 60℃ for 2 hours for drying pretreatment to eliminate the influence of trace amounts of moisture in the environment on the surface state of the reduced composite powder and obtain a powder sample for physical testing.

[0083] Weigh 50.0g of physical testing powder sample and pour it into the standard funnel of the Hall flow meter. Open the discharge hole at the bottom of the funnel and start the digital stopwatch simultaneously. Record the accurate time taken for the 50.0g physical testing powder sample to completely flow out of the discharge hole at the bottom of the standard funnel. Obtain the flowability value of the reduced composite powder. If the physical testing powder sample blocks the discharge hole at the bottom of the standard funnel, record it as not flowing.

[0084] Place an internal volume calibrated to 25 cm³ below the Hall effect flow meter. 3A standard cylindrical brass measuring cup is used to continuously and slowly add physical testing powder sample into the standard funnel of the Hall effect flow meter, allowing the powder sample to fall freely and fill the cup. Once the powder sample forms an overflow cone at the top of the cup, a straight stainless steel scraper is used to smoothly scrape away excess powder sample along the upper edge of the cup. The net mass of the powder sample inside the cup is then measured using a 0.01 g electronic balance. The net mass is then divided by 25 cm. 3 The volume was used to calculate the bulk density of the reduced composite powder.

[0085] Weigh 50.0g of physical testing powder sample and place it into a clean glass graduated cylinder with a volume of 100mL. Fix the glass graduated cylinder containing 50.0g of physical testing powder sample onto the fixture assembly of the microcomputer tapped density tester. Set the vibration frequency of the microcomputer tapped density tester to 300 times / min, the vertical amplitude to 3mm, and the total number of vibrations to 3000 times. After the vibration program finishes running, read the compressed volume scale of the physical testing powder sample in the glass graduated cylinder horizontally. Divide the absolute mass of 50.0g by the compressed volume scale to calculate the tapped density value of the reduced composite powder.

[0086] Divide the obtained tap density value by the corresponding loose packing density value to calculate the Hausner ratio, which reflects the friction and agglomeration state between powder particles.

[0087] Table 3. Results of flowability and density tests for reduced composite powders Example 1 26.4 2.15 2.61 1.21 Example 2 28.1 2.08 2.58 1.24 Example 3 25.8 2.18 2.55 1.17 Comparative Example 5 79.6 1.36 2.28 1.68 Conclusions and Analysis: According to Table 3, Figure 3 , Figure 4 and Figure 5 The data show that the flowability values ​​of the reduced composite powders prepared in Examples 1, 2, and 3 are concentrated between 25.8 s / 50 g and 28.1 s / 50 g, exhibiting good free-flow characteristics, and the loose bulk density is maintained at 2.08 g / cm³. 3 Above, with the Hausner ratio controlled below 1.25, the flowability of the reduced composite powder prepared in Comparative Example 5 deteriorated, with a complete outflow time of 79.6 s / 50 g, exhibiting viscous blockage, and the loose bulk density decreased to 1.36 g / cm³. 3 Housenabi rose to 1.68.

[0088] The reason for the difference in the above test results is that the surface tension of the washing solvent interferes with the drying and crystallization process of micro-particles. Comparative Example 5 only used deionized water to slurry and wash the wet filter cake of the coprecipitation precursor. Deionized water has a high surface tension. During the evaporation and dehydration stage in the vacuum drying oven, the liquid deionized water formed capillary contraction force in the gradually shrinking gaps between micro-particles. The capillary contraction force forcibly pulled together the free primary nano-sized precipitate particles and caused irreversible physical adhesion, eventually producing large-sized irregular hard agglomerates. The hard agglomerates contain a large number of closed void structures, resulting in a low spatial packing efficiency of the product of Comparative Example 5, which is manifested as a decrease in loose density. In addition, the surface of the irregular hard agglomerates is rough, and the mechanical interlocking and electrostatic friction between particles increase exponentially, which destroys the macroscopic flow properties of the reduced composite powder.

[0089] Examples 1 to 3 introduce a non-linearly increasing volume fraction of ethanol-water mixture and anhydrous ethanol to repeatedly slurry and wash the wet filter cake of the coprecipitation precursor. Anhydrous ethanol not only replaces the residual water in the gaps between microparticles, but its surface tension is also much lower than that of deionized water. During the heating process in the vacuum drying oven, ethanol and a small amount of residual water molecules form a low-boiling-point azeotropic mixture and preferentially complete vaporization and volatilization. The vaporization and volatilization process removes the powder surface with a low liquid bridge contraction force, which blocks the driving mechanism of hard agglomeration of primary particles from a physical and mechanical perspective. The resulting reduced composite powder maintains the highly dispersed and fine uniform morphology endowed by the coprecipitation reaction. The high fluidity and high bulk density ensure that the reduced composite powder can achieve absolutely uniform cavity filling when it is loaded into a flexible mold for cold isostatic pressing. Uniform cavity filling eliminates the local density gradient inside the green body, avoiding the problems of uneven shrinkage of macroscopic pores and microphase segregation in the later solid-phase densification sintering process. This provides a front-end process guarantee for the anti-arc ablation copper-silver contact alloy to achieve the theoretical density.

[0090] Test Example 4: Final Alloy Macroscopic Physical and Electrical Conductivity Tests The arc-erosion resistant copper-silver contact alloys prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were respectively processed into standard test cuboids with dimensions of 10mm × 10mm × 5mm. All surfaces of the standard test cuboids were polished step by step using 800-grit silicon carbide sandpaper to remove the processing oxide layer and adhering substances on the surface of the standard test cuboids. The polished standard test cuboids were placed in a beaker containing anhydrous ethanol for ultrasonic cleaning for 10 minutes, removed and dried at 60°C to obtain physical property test samples.

[0091] The absolute dry mass of the physical performance test sample was measured in air using an analytical balance with an accuracy of 0.01 g. The physical performance test sample was then completely immersed in a pure water measurement medium at a constant temperature of 25°C. The floating and sinking mass of the physical performance test sample in the pure water measurement medium was measured using the bottom-mounted weighing component of the analytical balance. The actual density value of the physical performance test sample was calculated according to Archimedes' principle of water displacement. The actual density value was divided by the theoretically calculated density value of the arc-resistant copper-silver contact alloy to obtain the relative density percentage data.

[0092] Turn on the eddy current conductivity meter and use a standard calibration block to calibrate the accuracy of the eddy current conductivity meter. Randomly select 5 measurement areas on the upper and lower surfaces of the physical performance test sample. Press the contact probe of the eddy current conductivity meter vertically and firmly onto the selected measurement area surface. After waiting for the reading to stabilize, record the macroscopic conductivity value in the form of International Annealed Copper Standard Percentage (%IACS). Add the 10 recorded macroscopic conductivity values ​​together and divide by 10 to calculate the arithmetic mean as the final macroscopic conductivity result of the physical performance test sample.

[0093] The physical performance test sample is placed on the test platform of the Vickers hardness tester. The test load parameter of the Vickers hardness tester is set to 0.98N and the holding time parameter is set to 15s. The Vickers hardness tester is used to press seven diamond-shaped indentations at equal intervals on the surface of the physical performance test sample. The lengths of the two diagonals of each diamond indentation are read using the matching measuring microscope and the corresponding single-point hardness value is calculated. The highest and lowest values ​​among the seven single-point hardness values ​​are removed. The remaining five single-point hardness values ​​are added together and divided by 5 to obtain the final Vickers hardness (HV) data of the physical performance test sample.

[0094] Table 4. Test results of physical and electrical properties of arc-erosion resistant copper-silver contact alloy Example 1 99.4 87.2 93 Example 2 99.1 88.5 91 Example 3 99.6 86.9 95 Comparative Example 1 96.2 79.4 84 Comparative Example 2 98.7 85.1 92 Comparative Example 3 94.5 76.8 81 Comparative Example 4 93.8 75.3 79 Comparative Example 5 91.2 71.6 74 Conclusions and Analysis: According to Table 4 and Figure 6 According to the data, the relative density values ​​of the arc-erosion resistant copper-silver contact alloys prepared in Examples 1, 2 and 3 all reached over 99.1%, the macroscopic conductivity index was in the range of 86.9% IACS to 88.5% IACS, and the Vickers hardness was distributed in the range of 91HV to 95HV. The arc-erosion resistant copper-silver contact alloys prepared in Comparative Examples 1 to 5 showed significant changes in the three key performance indicators. The relative density of Comparative Example 5 dropped to 91.2%, the macroscopic conductivity dropped to 71.6% IACS, and the Vickers hardness was only 74HV.

[0095] The fundamental reason for the excellent comprehensive performance of the arc-erosion resistant copper-silver contact alloys prepared in Examples 1 to 3 lies in the successful physical transfer of the front-end powder homogenization mechanism to the final bulk material structure. The dynamic decay of the dielectric constant and the forced precipitation mechanism coupled with the pH gradient hysteresis deprive the component metal ions of the crystallization time difference. The azeotropic displacement washing eliminates the hard agglomeration effect of nanoparticles. The excellent free flowability ensures that the powder loaded into the flexible mold is in an absolutely uniform spatial packing state. In the cold isostatic pressing process, the agglomerated powder achieves isotropic compaction. In fact, the local stress concentration points inside the alloy green billet are eliminated. During the solid-state densification sintering stage, the in-situ generated yttrium oxide particles cannot cross the grain boundaries to complete macroscopic agglomeration. The yttrium oxide particles are uniformly distributed in the copper-silver alloy matrix in a nanoscale dispersed state. The nanoscale dispersed yttrium oxide particles have a pinning effect on grain boundary sliding, which improves the macroscopic Vickers hardness of the arc-erosion resistant copper-silver contact alloy. The smaller-sized dispersed phase minimizes the grain boundary scattering effect on the free electron transport path inside the metal, ensuring the macroscopic conductivity of the arc-erosion resistant copper-silver contact alloy.

[0096] Comparative Examples 1, 3, and 4 lacked time-controlled fluid physics intervention, resulting in uncontrolled precipitation of the three metal components. Segregation of precursor components was conducted into the final bulk material, leading to the formation of silver-rich and copper-rich regions at the tens of micrometer scale within the arc-resistant copper-silver contact alloy, accompanied by coarse agglomerates of yttrium oxide. These large insulating yttrium oxide phases disrupted the local electronic conductivity network, increasing grain boundary scattering resistance and causing a decline in macroscopic conductivity. Comparative Example 5 used only pure water in the washing process, and the surface tension of deionized water... The mixed precursor powder of multi-metal carbonates undergoes hard agglomeration. Irregularly shaped hard agglomerates are locked by powder bridging during cold isostatic pressing. A large number of geometric voids remain inside the alloy green blank. These geometric voids cannot be filled by atomic diffusion during solid-state densification sintering and eventually become residual pores inside the arc-resistant copper-silver contact alloy. The residual pores cause the relative density to collapse, and at the same time, they destroy the continuity of the mechanical bearing surface and the charge transport channel, causing the Vickers hardness and macroscopic conductivity to deteriorate simultaneously.

[0097] Test Example 5: Arc Erosion Resistance and Electrical Life Test under Relay Operating Conditions Using precision cold heading equipment, the arc-erosion resistant copper-silver contact alloys obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively processed into standard rivet contacts with a head diameter of 4.0 mm, a head thickness of 1.5 mm, and a rivet foot diameter of 2.0 mm.

[0098] Place the standard rivet contact in a glass beaker containing anhydrous ethanol, turn on the ultrasonic cleaner and ultrasonically clean for 15 minutes to remove oil and machining debris from the surface of the standard rivet contact. After cleaning, transfer the standard rivet contact to a vacuum drying oven at 60°C and dry for 2 hours. Use a micro-analytical balance with an accuracy of 0.0001 g to weigh and test the initial absolute mass of the standard rivet contact before cleaning.

[0099] The weighed standard rivet contacts are riveted together and installed on the moving and stationary springs of a dedicated electrical contact simulation test platform. The mechanical distance and closing pressure of the moving and stationary springs are adjusted to ensure that the initial mechanical contact state of each pair of standard rivet contacts remains consistent.

[0100] Set the test electrical parameters of the dedicated electrical contact simulation test platform, set the test load type to resistive load, set the test voltage to DC 220V, set the closing and opening current to 20A, set the operation frequency to 1 time / s, set the contact closing time to 0.5s, the opening time to 0.5s, and set the total number of cycle operations to 100,000.

[0101] A dedicated electrical contact simulation test platform was launched to conduct cyclic breaking tests. During the test, a high-frequency digital oscilloscope was connected to monitor the voltage and current waveforms at both ends of the standard rivet contact in real time. The arc reignition phenomenon that occurred at the moment the standard rivet contact was broken was captured by the high-frequency digital oscilloscope. The total frequency of secondary breakdown or abnormal long arc in 100,000 cycles was counted.

[0102] During the cyclic opening and closing test, every 10,000 cycles, the dynamic contact resistance value of the standard rivet contact in the closed state is measured and recorded once using a four-wire micro resistance tester. The maximum and minimum values ​​of the 10 dynamic contact resistance value records are extracted, and the difference between the maximum and minimum values ​​is calculated to obtain the dynamic contact resistance range.

[0103] After 100,000 cycles, the standard rivet contacts that have been subjected to electric arc bombardment are removed, and the ultrasonic cleaning and vacuum drying steps are repeated. The final absolute mass of the standard rivet contacts is weighed and tested using a micro-analytical balance. The initial absolute mass is subtracted from the final absolute mass, and then divided by 10 to calculate the mass loss rate under the condition of 10,000 cycles.

[0104] Table 5. Test results of electrical contact performance of copper-silver contact alloy with arc erosion resistance Example 1 1.15 0.38 0 Example 2 1.28 0.45 1 Example 3 1.12 0.35 0 Comparative Example 1 3.65 1.54 4 Comparative Example 2 5.82 2.76 93 Comparative Example 3 2.84 1.21 3 Conclusions and Analysis: According to Table 5, Figure 7 and Figure 8According to the data, the arc-resistant copper-silver contact alloys prepared in Examples 1, 2, and 3 exhibited good arc resistance during 100,000 high-current DC load cycle interruptions. The mass loss rate remained at a low level of 1.12 mg / 10,000 cycles to 1.28 mg / 10,000 cycles, the dynamic contact resistance difference was less than 0.45 mΩ, and the arc reignition frequency was almost zero. In contrast, the mass loss rate of Comparative Examples 1 and 3 increased to over 2.84 mg / 10,000 cycles, and the dynamic contact resistance difference significantly increased. The test results of Comparative Example 2 deteriorated, with the arc reignition frequency surging to 93 times, the mass loss rate reaching as high as 5.82 mg / 10,000 cycles, and the dynamic contact resistance difference reaching 2.76 mΩ.

[0105] Examples 1 to 3 utilize a synergistic process of preparing precursors using a fully ammonium-state dual-complex homogeneous initial-phase mother liquor and a dynamic decay of dielectric constant. The temporal coupling effect of chemical decomplexation and antisolvent precipitation forces large-volume yttrium ions to undergo synchronous co-nucleation with copper and silver ions, forming yttrium oxide particles within the final arc-resistant copper-silver contact alloy. When the standard rivet contact breaks, generating a high-temperature arc of several thousand degrees Celsius, local metal melting occurs on the contact surface, forming a molten pool. High-melting-point, nanoscale, highly dispersed yttrium oxide particles are suspended in the liquid copper-silver molten pool, increasing its macroscopic viscosity. This high-viscosity molten pool resists the mechanical blowing force generated by the arc plasma expansion, suppressing the outward splashing of liquid metal and reducing mass loss rate from a physical fluid perspective. Simultaneously, the highly dispersed yttrium oxide particles prevent the formation of large-area insulating oxide enrichment zones on the contact surface, ensuring the effective contact area of ​​conductive spots during subsequent closing operations and maintaining high stability of the dynamic contact resistance difference.

[0106] Due to the lack of fluid physics intervention or the absence of a delayed triggering mechanism, Comparative Examples 1 and 3 experienced component segregation in the multi-metal carbonate mixed precursor powder. The coarse and agglomerated yttrium oxide phase failed to increase the overall viscosity of the liquid copper-silver molten pool, leading to intensified metal vaporization and splashing under arc erosion, increased mass loss rate, and random exposure of the coarse insulating phase on the contact surface blocked the electron transport channel, resulting in drastic fluctuations in dynamic contact resistance.

[0107] Comparative Example 2, due to the introduction of disodium ethylenediaminetetraacetate in the raw material stage, left trace sodium impurities inside the anti-arc ablation copper-silver contact alloy. The ionization energy of sodium is only 5.14 eV, far lower than that of silver and copper. Within milliseconds after the standard rivet contact completes mechanical disconnection, the residual arc heat causes the sodium atoms on the contact surface to undergo violent thermal ionization. The large number of released secondary electrons and positive ions, under the influence of the strong electric field in the gap between the plates, re-establish plasma conductive channels, triggering arc reignition. Frequent arc reignition subject the standard rivet contact to thermal bombardment, resulting in deep melting, peeling, and oxidation of the surface alloy material, which damages the electrical life of the anti-arc ablation copper-silver contact alloy. The all-ammonia in-situ salt production process of Examples 1 to 3 eliminated low-ionization potential alkali metal contamination, ensured the recovery of the dielectric strength of the mechanical break gap, and removed the hidden danger of arc reignition.

Claims

1. A copper-silver contact alloy resistant to arc erosion, characterized in that, It is prepared from a fully ammonium-state dual-complex homogeneous initial state mother liquor through dynamic coupling co-precipitation, washing, vacuum drying, oxidative calcination, hydrogen reduction and solid-phase densification sintering; The raw materials for preparing the fully ammonium-state dual-complex homogeneous initial state mother liquor include deionized water, silver nitrate, copper nitrate trihydrate, yttrium nitrate hexahydrate, ethylenediaminetetraacetic acid free acid, and ammonia. The reagents used in the dynamic coupling coprecipitation include aqueous ammonium bicarbonate solution and anhydrous ethanol; The reagents used for washing include an ethanol-water mixture and anhydrous ethanol.

2. The anti-arc erosion copper-silver contact alloy according to claim 1, characterized in that, The raw material ratio range for preparing the fully ammonium-state dual-complex homogeneous initial state mother liquor is as follows: The silver nitrate content is 0.80–0.95 mol; The amount of copper nitrate trihydrate is 0.045–0.15 mol; The amount of yttrium nitrate hexahydrate is 0.005–0.05 mol. The free acid of ethylenediaminetetraacetic acid is 0.0525–0.24 mol.

3. The arc-erosion resistant copper-silver contact alloy according to claim 1, characterized in that, The solid-state densification sintering was carried out under nitrogen protection.

4. A method for preparing an arc-erosion resistant copper-silver contact alloy as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Ethylenediaminetetraacetic acid (EDTA) free acid was suspended and added to deionized water. Ammonia was added dropwise until the EDTA free acid was completely dissolved to obtain a tetraammonium EDTA solution. Silver nitrate, copper nitrate trihydrate, and yttrium nitrate hexahydrate were added to the tetraammonium EDTA solution. After complete dissolution, the solution was heated in a cyclic heating system at a constant temperature. Ammonia was added dropwise to adjust the pH of the complexed mixture to obtain a fully ammonium-state dual-complex homogeneous initial state mother liquor. Ammonium bicarbonate aqueous solution is continuously pumped into the initial state mother liquor of the all-ammonium dual complex to carry out dynamic coupling co-precipitation, so that the pH value of the complex mixture decreases linearly. When the pH value of the complex mixture drops to the first pH value range, anhydrous ethanol is injected while the ammonium bicarbonate aqueous solution is continuously pumped in until the pH value of the complex mixture drops to the second pH value range and the volume fraction of anhydrous ethanol in the complex mixture reaches the preset volume fraction range. The mixture is then aged at a constant temperature to obtain a coprecipitation precursor suspension slurry. The coprecipitation precursor suspension slurry was subjected to solid-liquid separation to obtain a wet filter cake of the coprecipitation precursor. The wet filter cake of the coprecipitation precursor was washed sequentially with an ethanol-water mixture and anhydrous ethanol, and then vacuum dried to obtain a multi-metal carbonate mixed precursor powder. The multi-metal carbonate mixed precursor powder is oxidized and calcined in air to obtain mixed oxide phase powder, and the mixed oxide phase powder is reduced in hydrogen atmosphere to obtain reduced composite powder. The reduced composite powder is cold isostatically pressed to obtain an alloy green blank, and the alloy green blank is then solidified and sintered to obtain the arc-erosion resistant copper-silver contact alloy.

5. The preparation method according to claim 4, characterized in that, The constant temperature range is 60-75℃, and the pH value of the mixture is adjusted to 11.0-12.0 by adding ammonia water dropwise.

6. The preparation method according to claim 4, characterized in that, The concentration range of the ammonium bicarbonate aqueous solution is 1.5 mol / L to 2.5 mol / L, and the pH decrease rate of the coprecipitation mixture is 0.15 pH / min to 0.25 pH / min.

7. The preparation method according to claim 4, characterized in that, The first pH value range is 9.2 to 9.8, the second pH value range is 7.8 to 8.2, the preset volume fraction range is 35% to 45%, and the heat preservation and aging time range is 45 to 90 minutes.

8. The preparation method according to claim 4, characterized in that, The volume fraction of ethanol in the ethanol-water mixture ranges from 35% to 45%, the vacuum degree of the vacuum drying ranges from 0.08 MPa to 0.1 MPa, the temperature range of the vacuum drying ranges from 70 to 90°C, and the time range of the vacuum drying ranges from 10 to 14 hours.

9. The preparation method according to claim 4, characterized in that, The heating rate of the oxidation calcination ranges from 2℃ / min to 5℃ / min, the temperature range of the oxidation calcination ranges from 450℃ to 550℃, and the time range of the oxidation calcination ranges from 1.5h to 3h. The heating rate of the hydrogen reduction ranges from 3℃ / min to 5℃ / min, the temperature range of the hydrogen reduction ranges from 400℃ to 500℃, and the time range of the hydrogen reduction ranges from 1.5h to 3h.

10. The preparation method according to claim 4, characterized in that, The pressure range of the cold isostatic pressing is 400MPa to 600MPa, the temperature range of the solid-phase densification sintering is 800℃ to 880℃, and the time range of the solid-phase densification sintering is 3h to 6h.

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