RU2300446C2 - Method for producing composition material for electrical- engineering designation - Google Patents

Abstract

FIELD: powder metallurgy, namely production of composition materials on base of tungsten carbide for making electric contacts.

SUBSTANCE: method for producing composition material comprises steps of mixing powders by two stages: at first mixing powders of tungsten-cobalt hard alloy and copper, then mixing prepared mixture with graphite. Alcoholic solution of orthophosphoric acid is added to prepared mixture in quantity providing next relation of components of sintered material, mass %: copper, 30 - 50; nickel, 5.0 - 15.0; graphite, 1.0 - 3.0; phosphorus, 0.8 - 1.5; hard alloy, the balance. Then stages of plasticizing, pressing and liquid-phase sintering in vacuum are realized. At heating process during sintering stage three isothermal soaking stages are performed. At first soaking is performed at temperature of creating easy-to-melt eutectics Cu-P; then sintering is performed at temperature of creating easy-to-melt eutectics Ni - P and third sintering stage is performed at temperature of creating easy-to-melt eutectics Co - P.

EFFECT: enhanced rigidity and wear resistance of material.

2 cl, 2 dwg

Description

The invention relates to the field of powder metallurgy, mainly can be used to obtain electrical contact materials.

Contact materials operating under dynamic loads, in addition to high strength and electrical conductivity, must have sufficiently high hardness and wear resistance. To this end, materials intended for the manufacture of electrical contact products are made on the basis of tungsten carbide with the addition of alloying materials.

Closest to the claimed invention is a method for producing material [Patent for the invention of the Russian Federation No. 2203340, C2, 7 C22C 29/08, B22F 3/12, 2001], consisting of copper, cobalt and tungsten carbide, which consists in mixing powders WC, Co and Cu and adding an orthophosphoric acid alcohol solution to the resulting mixture in such a way that the mixture consisted of components with the following component ratios, wt.%: Copper 10-40, phosphoric acid 0.6-6.0, tungsten carbide and cobalt - the rest. Then, the resulting mass is plasticized with the composition of rubber dissolved in gasoline, and liquid-phase sintering is carried out in vacuum furnaces at a temperature of 1220-1350 ° C. The resulting material has high electrical conductivity and strength, but unsatisfactory hardness and wear resistance, and the proposed method does not ensure the stability of the material properties.

The technical result of the claimed invention is to increase the hardness, strength and wear resistance of carbide electrocontact material with a simultaneous improvement of the method of its manufacture.

The technical result is achieved by a method of manufacturing a composite material for electrical purposes, including mixing powders, introducing into the resulting mixture an alcoholic solution of phosphoric acid, plasticizing, pressing and vacuum liquid phase sintering. In this case, the mixing of the powders is carried out in two stages, first the powders of tungsten-cobalt hard alloy, nickel and copper are mixed, then the resulting mixture is mixed with graphite, after which an alcohol solution of phosphoric acid is introduced in the amount necessary to obtain the following ratio of components in the sintered material, wt.% : copper 30-50; nickel 5.0-15.0; graphite 1.0-3.0; phosphorus 0.8-1.5; hard alloy - the rest; moreover, in the process of heating during sintering produce three isothermal extracts. The first isothermal exposure during heating is carried out at a temperature of formation of a fusible Cu-P eutectic, the second at a temperature of formation of a fusible Ni-P eutectic, and the third at a temperature of formation of a fusible Co-P eutectic. And liquid-phase sintering of the composite material is carried out at the liquidus temperature of the Cu-Ni-Co-P system.

Figure 1 shows the microstructure of a composite material for electrical purposes after etching; figure 2 - etched microstructure of the composite material.

To obtain the claimed material, powders of tungsten-cobalt carbide type VK6 or VK8 (respectively in wt.%: 94% WC + 6% Co and 92% WC + 8% Co) are added with nickel and copper powders and mixed for 45-60 minutes . Then graphite powder is introduced into the resulting mixture and kneading is carried out for 10-15 minutes, i.e. so that graphite partially envelops particles of nickel, copper and cobalt. An alcoholic solution of orthophosphoric acid H ₃ PO ₄ + C ₂ H ₅ OH is added to the resulting mixture, stirred for 10-15 minutes, and then the steps are carried out according to the standard technological process of powder metallurgy before sintering of products, i.e. the resulting mixture is plasticized with a rubber gasoline solution, and articles are pressed from it. The amount of an orthophosphoric acid alcohol solution is added such that as a result, 0.8-1.5% by weight of phosphorus is contained in the material.

Liquid phase sintering of products is carried out in vacuum furnaces. In the process of heating to sintering temperature, three isothermal extracts are produced. The first isothermal exposure during heating is carried out at the temperature of formation of the fusible Cu-P eutectic, i.e. at a temperature of 600-714 ° C for 5-10 minutes, depending on the phosphorus content in the mixture. The second isothermal exposure during heating is carried out at the temperature of formation of the low-melting eutectic Ni-P, i.e. at a temperature of 860-880 ° C for 15-20 minutes The third isothermal exposure during heating is carried out at the temperature of formation of the fusible Co-P eutectic, i.e. at a temperature of 1000-1050 ° C for 20-25 minutes The liquid phase sintering of the composite material is carried out for 60-100 min at the liquidus temperature of the Cu-Ni-Co-P system, taking into account the ratios of the components, i.e. for the claimed material is 1150-1220 ° C.

Thanks to the inventive method of mixing the components of the composite material are evenly distributed throughout the volume of the material, which is a sign of the stability of physico-mechanical properties and structure throughout the volume of the material. The fusible eutectics CuP, NiP, and CoP formed during sintering activate the dissolution of solid phases (tungsten carbides) in the liquid phase (copper) and improve the processes of wetting of the components together.

It was experimentally found that the tungsten carbide grains present in the inventive material during sintering form a carbide framework 1 (FIGS. 1, 2), which provides high hardness to the product. Since nickel, cobalt and copper are not carbide-forming elements, the graphite in the material is released in the form of misoriented plate inclusions 2 (FIGS. 1, 2), which impart high wear resistance to the material. Since the Cu-Co system itself is immiscible under thermodynamic conditions, when studying the microstructure, phases of copper 3 were found (Fig. 1), which provide high electrical conductivity and strength of the composite material. During sintering, copper forms continuous solid solutions with nickel. Nickel significantly hardens copper. Due to the claimed ratio of components, the composite material bundle is similar in composition to copper-nickel alloys of the nickel silver type, which are distinguished by high corrosion resistance, high mechanical properties, and are well processed by pressure. As a result, the inventive material has a density of 9.0-10.0 g / cm ³ , Brinell hardness of at least 1000 MPa, tensile strength of 600-900 MPa, and additional alloying with nickel ensures the stability of obtaining the necessary material properties.

Claims (2)

1. A method of manufacturing a composite material for electrical purposes, including mixing powders, introducing into the resulting mixture an alcohol solution of phosphoric acid, plasticizing, pressing and vacuum liquid phase sintering, characterized in that the mixing of the powders is carried out in two stages, first powders of tungsten-cobalt hard alloy, nickel and copper, then the resulting mixture is mixed with graphite, after which an alcohol solution of phosphoric acid is introduced in an amount necessary to obtain the following ratio of components in the sintered material, wt.%: Copper 30-50 Nickel 5.0-15.0 Graphite 1.0-3.0 Phosphorus 0.8-1.5 Hard alloy Rest moreover, during heating during sintering, three isothermal extracts are made: the first at the temperature of formation of the fusible Cu-P eutectic, the second at the temperature of formation of the fusible Ni-P eutectic, and the third at the temperature of the formation of Co-P fusible eutectic. 2. The method according to claim 1, characterized in that the liquid-phase sintering is carried out at a liquidus temperature of the Cu-Ni-Co-P system.

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