A silver-tungsten contact material mixed powder containing elemental metal additives and a preparation method thereof

Abstract

The present invention discloses a silver-tungsten contact material mixed powder containing elemental metal additives and a preparation method thereof. In this method, the elemental metal powder is first treated in an antioxidant and dispersant solution, and then jointly subjected to ultrasonic dispersion and stirring treatment with tungsten powder. Under the reduction reaction generated by glucose, sodium hydroxide, ammonium ions and silver ions, the obtained silver-tungsten material powder has a uniform metallographic structure. The advantages of the present invention are that during the liquid-phase reduction reaction process, the elemental metal additives can be prevented from reacting with the silver solution by displacement reaction and causing losses. At the same time, the silver powder particles of the silver-tungsten contact material are fine and the metallographic structure is uniform.

Description

Technical Field

[0001] The present invention relates to the field of contact materials for low-voltage power distribution equipment, and particularly to a silver-tungsten contact material mixed powder containing elemental metal additives and a preparation method thereof. Background Art

[0002] Silver-tungsten contact materials are widely used in low-voltage circuit breakers for the functions of connecting, carrying, and breaking currents. The performance of the contact materials largely determines the performance and operation reliability of the circuit breakers. The infiltration-type silver-tungsten (AgW) materials contain micron-sized dispersed tungsten particles as reinforcement phases, which can greatly improve the arc erosion resistance of the materials. The liquid-phase sintering (infiltration) process can ensure good wetting between silver and tungsten particles, thus avoiding material spattering under the action of high-temperature arcs.

[0003] Through retrieval, Chinese Patent CN 104480335 discloses a preparation method of a silver-tungsten contact material. The main method is to mix silver powder and tungsten powder, and place the obtained silver-tungsten mixed powder, high-purity nickel balls, and water in a ball mill for ball milling. The ball-milled silver-tungsten mixed powder is then dried, annealed, formed, and infiltrated to obtain the product. Among them: the weight ratio of the high-purity nickel balls to the silver-tungsten mixed powder is 4-10:1; the amount of water is calculated as adding 120-200 ml of water per 1 kg of silver-tungsten mixed powder; the ball milling time is 12-50 h. In the present invention, the silver-tungsten mixed powder, high-purity nickel balls, and water are placed in a ball mill for ball milling for a specific time according to a specific ratio, which not only makes the mixing of silver powder and tungsten powder more uniform, but also realizes the simultaneous ball milling and addition of the additive nickel. Moreover, the nickel worn from the high-purity nickel balls can be evenly deposited on the surface of the tungsten particles to effectively improve the wettability of silver to tungsten. The obtained material has a uniform structure, high density, and low resistivity. However, the technical solution of this patent has the following disadvantages: the wettability of silver to tungsten mentioned in it is poor. When using the infiltration process to manufacture, trace metal elements such as nickel, cobalt, and iron need to be added to improve the wettability of silver to tungsten so that the silver liquid can penetrate into the silver-tungsten compact to obtain a dense contact. In addition, in this patent scheme, the physical ball milling powder mixing method is used, and the obtained silver-tungsten mixed powder product is not as uniform and fine as the silver-tungsten mixed powder prepared by the chemical coating method.

[0004] Chinese Patent CN 110129603 discloses a manufacturing method and its product of a silver-tungsten contact material. The main method is to add tungsten powder and silver nitrate solution into a reaction vessel, and then add polyethylene glycol, sodium hydroxide and glucose solution into the reaction vessel. After a reduction reaction under ultrasonic oscillation and stirring conditions, silver is precipitated and wrapped outside the tungsten powder to form a composite powder. The structure of the composite powder is as follows: a pure silver shell layer with a thickness of 10-200 nm covers the outside of tungsten particles; (2) Mix the composite powder with silver powder to form a silver-tungsten powder containing 4% silver, and then press it into a contact compact with a porosity of 5-45%; (3) Place the contact compact and silver block in a sintering furnace protected by an ammonia decomposition atmosphere for sintering and infiltration, so as to obtain a silver-tungsten contact material with specified dimensions and composition. The disadvantages of this patent scheme are as follows: Although the chemical coating method is adopted, since sodium hydroxide is first added to react with silver nitrate to form a precipitate of silver hydroxide, and at this time the silver hydroxide is coated on the tungsten powder for precipitation, and then glucose is added for reduction, it will cause the silver hydroxide to separate from the tungsten powder and be reduced back to silver powder, resulting in silver aggregation in the silver-tungsten powder body. Summary of the Invention

[0005] The object of the present invention is to overcome the disadvantages and deficiencies existing in the prior art, and to provide a mixed powder of a silver-tungsten contact material containing elemental metal additives and a preparation method thereof. This method can effectively add elemental metal powder additives into the silver-tungsten contact material by using a chemical coating process, and at the same time, the powder particles of the silver-tungsten contact material are fine and the product metallography is uniform.

[0006] To achieve the above object, the first aspect of the present invention is to provide the following steps:

[0007] S1. Treatment of elemental metal additive powder: Place the elemental metal powder in a mixed solution of an antioxidant and a dispersant, and after ultrasonic dispersion and stirring treatment, wash and filter it with pure water for later use;

[0008] S2. Preparation of silver-containing solution: Add ammonia water, analytical pure nitric acid, and glucose solution to the silver nitrate solution in sequence;

[0009] S3. Reduction reaction: Place tungsten powder, the elemental metal additive powder in step S1, and pure water in a reaction vessel, and after ultrasonic dispersion and stirring treatment, add sodium hydroxide solution to the reaction vessel, and finally add the silver-containing solution prepared in step S2 to the reaction vessel, and a reduction reaction is carried out to obtain a mixed powder of a silver-tungsten contact material containing elemental metal additives.

[0010] A further setting is that the mixed solution of the antioxidant and the dispersant in step S1 is a mixed solution of benzotriazole, oleic acid, polyvinyl alcohol and absolute ethanol, and the mass ratio of benzotriazole, oleic acid, polyvinyl alcohol to absolute ethanol is 1:(0.5-2):(1.5-2.5):(100-500).

[0011] A further setting is that the silver content in the silver nitrate solution in step S2 is 1%-25%.

[0012] A further setting is that ammonia water is added to the silver nitrate solution in step S2, and the pH value is controlled at 7.0-8.0; then analytical pure nitric acid is added, and the pH value is controlled at 0.5-1.5.

[0013] A further setting is that the mass ratio of the silver nitrate solid in S2, the glucose solid in S2, and the sodium hydroxide solid in S3 is 1.5:(0.25-0.45):(0.5-0.8).

[0014] A further setting is that the elemental metal additive is one or a combination of nickel, copper, and cobalt.

[0015] In addition, the present invention also provides a mixed powder of a silver-tungsten contact material containing an elemental metal additive prepared by the preparation method as described.

[0016] The beneficial effects and innovations of the present invention are:

[0017] 1. In the reduction reaction designed in this application, during the liquid-phase reduction reaction process, the elemental metal additive is prevented from reacting with the silver solution by displacement reaction, resulting in loss. At the same time, the powder particles of the silver-tungsten contact material are fine, and the product metallographic structure is uniform. The mechanism is that there are two reduction reactions. Reaction one is that ammonium ions, silver ions, and hydroxide ions will produce silver ammonia complex ions, and then react with the glucose solution to produce reduced silver. Reaction two is that after silver ions react with hydroxide ions to form silver hydroxide precipitate, it reacts with the glucose solution to produce reduced silver. Reaction one is a silver mirror reaction that can coat silver on the surface of tungsten powder and additive powder. Especially when the surface of tungsten powder and additive powder is irregular and concave-convex, the silver layer can adhere to the concave of the powder, reducing the agglomeration of tungsten powder or additive powder in the product metallography. When reaction one and reaction two occur simultaneously, the tungsten powder and silver powder are mixed evenly.

[0018] 2. Since the elemental metal additive powder is treated in an antioxidant and a dispersant, the surface of the additive powder is attached with an antioxidant to prevent oxidation and displacement reaction in the silver nitrate solution, resulting in loss. Under the action of the dispersant, the silver powder particles reduced by the reaction are fine, and the metallographic structure of the silver-tungsten product is more uniform and dispersed. Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, obtaining other drawings based on these drawings still belongs to the scope of the present invention.

[0020] Figure 1 Comparison diagram of the metallographic structure of silver-tungsten products prepared by the process of the present invention and the traditional powder mixing process, where Figure 1 (a) Metallographic structure diagram of the silver-tungsten product prepared by the process of the present invention, Figure 1 (b) Metallographic structure diagram of the silver-tungsten product prepared by the traditional powder mixing process. Detailed implementation manners

[0021] To make the purpose, technical solutions and advantages of the present invention clearer, the following will further describe the present invention in detail with reference to the embodiments.

[0022] Embodiment 1

[0023] (1) Prepare a 500 ml solution by mixing benzotriazole, oleic acid, polyvinyl alcohol and absolute ethanol in a mass ratio of 1:0.5:1.5:300;

[0024] (2) Under the action of ultrasonic dispersion and stirring, place 1.5 g of nickel powder and 1.5 g of copper powder in the solution prepared in (1), treat for 20 min, and then filter and wash for later use;

[0025] (3) Dissolve 62.96 g of silver nitrate in 1000 ml of pure water, keep stirring, first add ammonia water solution until the pH reaches 8.0; continue to keep stirring, then add analytical pure nitric acid solution until the pH reaches 1.0; continue to keep stirring, and finally add 14 g of glucose and stir until dissolved and clarified to obtain a reaction silver-containing solution;

[0026] (4) Dissolve 32 g of sodium hydroxide in 500 ml of pure water and cool to room temperature;

[0027] (5) Mix 157 g of tungsten powder, the nickel powder and copper powder in step (2) with 3000 ml of pure water, perform ultrasonic dispersion and stirring treatment for 20 min, then continue to keep ultrasonic and stirring, first add the sodium hydroxide solution in step (4) thereto, and then add the reaction silver-containing solution in step (3) at a flow rate of 40 ml / min;

[0028] (6) After all the silver-containing solution is added, continue to keep ultrasonic dispersion and stirring for 5 min. After the reaction is completed, wash and dry the silver-tungsten mixed powder to obtain the required AgW80 mixed powder.

[0029] FromFigure 1 As can be seen from (a) and (b), for the silver-tungsten mixed powder with the same composition, the metallographic structure of the (a) product is highly dispersed, and the consistency of the contact material is improved significantly compared with the (b) product. The main reason is that in the silver reduction reaction, the silver mirror phenomenon allows silver powder to adhere to the depressions of the powder body. At the same time, under the action of the dispersant on the surface of the additive powder, the silver powder particles reduced by the reaction are fine, and the metallographic structure of the product is more uniform.

[0030] Example Two

[0031] (1) Prepare 100 L of solution with the mass ratio of benzotriazole, oleic acid, polyvinyl alcohol to absolute ethanol being 1:0.5:1.5:300.

[0032] (2) Under the action of ultrasonic dispersion and stirring, place 0.3 Kg of nickel powder, 0.2 Kg of copper powder and 0.1 Kg of cobalt powder into the solution prepared in (1), treat for 20 min, and then filter and wash for later use.

[0033] (3) Dissolve 4.72 Kg of silver nitrate in 200 L of pure water, keep stirring, add ammonia water until the pH reaches 8.0; continue to stir, then add analytical pure nitric acid solution until the pH reaches 1.0; continue to stir, and finally add 1.15 Kg of glucose and stir until dissolved and clarified to obtain the reaction silver-containing solution.

[0034] (4) Dissolve 2.4 Kg of sodium hydroxide in 100 L of pure water and cool to room temperature.

[0035] (5) Mix 26.4 Kg of tungsten powder, the nickel powder and copper powder in step (2) with 1000 L of pure water, perform ultrasonic dispersion and stirring treatment for 40 min, continue to maintain ultrasonic and stirring, first add the sodium hydroxide solution in step (4) thereto, and then add the reaction silver-containing solution in step (3) at a flow rate of 5 L / min.

[0036] (6) After all the silver-containing solution is added, continue to maintain ultrasonic dispersion and stirring for 5 min. After the reaction is completed, wash and dry the silver-tungsten mixed powder to obtain the required AgW90 mixed powder.

[0037] The above-disclosed are only the preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. A preparation method of a silver-tungsten contact material mixed powder containing elemental metal additives, characterized in that it includes the following steps: S1. Treatment of elemental metal additive powder: Place the elemental metal additive powder in a mixed solution of antioxidant and dispersant, after ultrasonic dispersion and stirring treatment, wash and filter with pure water for later use; In step S1, the mixed solution of antioxidant and dispersant is a mixed solution of benzotriazole, oleic acid, polyvinyl alcohol and absolute ethanol, and the mass ratio of benzotriazole, oleic acid, polyvinyl alcohol to absolute ethanol is 1:(0.5 - 2):(1.5 - 2.5):(100 - 500); The elemental metal additive is one or a combination of nickel, copper, and cobalt; S2. Preparation of silver-containing solution: Add ammonia water, analytical pure nitric acid, and glucose solution to the silver nitrate solution in sequence; In step S2, the silver content of the silver nitrate solution is 1% - 25%; In step S2, add ammonia water to the silver nitrate solution to control the pH value at 7.0 - 8.0; then add analytical pure nitric acid to control the pH value at 0.5 - 1.5; S3. Reduction reaction: Place tungsten powder, the elemental metal additive powder in step S1, and pure water in a reaction vessel, after ultrasonic dispersion and stirring treatment, then add sodium hydroxide solution to the reaction vessel, and finally add the silver-containing solution prepared in step S2 to the reaction vessel to obtain a silver-tungsten contact material mixed powder containing elemental metal additives through a reduction reaction; The mass ratio of silver nitrate solid for preparing the silver nitrate solution in step S2, glucose solid for preparing the glucose solution in step S2, and sodium hydroxide solid for preparing the sodium hydroxide solution in step S3 is 1.5:(0.25 - 0.45):(0.5 - 0.8).

2. A silver-tungsten contact material mixed powder containing elemental metal additives prepared by the preparation method according to claim 1.

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