RU2368971C1 - Material for high-current sliding electrocontact - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to powder metallurgy, particularly to antifriction materials. It can be used for manufacturing of current-collecting brush, particularly homopolar generators or current-collecting shoes, contacting to rail. Composite material of following composition, wt %: copper 18-46; graphite 2-3; treated steel "ШХ15" - the rest.

EFFECT: material allows high wear resistance in conditions of dry sliding electro-contact and provides increasing of mechanical properties of current collector at satisfactory electroconductivity of friction zone.

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Description

The invention relates to powder metallurgy, in particular to antifriction materials used for the manufacture of collector brushes, in particular unipolar generators or collector shoes in contact with the rail.

To work under these conditions, high electrical conductivity, good mechanical properties and high resistance to electrical erosion at a current density of more than 100 A / cm ^{2 are} required.

Known sintered material based on copper of the following composition (wt.%) [1]:

Graphite 0.5-6 Tin 2-13 Nickel 3-15 Lead 2-8 Copper rest

The disadvantages of the known material are low mechanical strength and low wear resistance with increased roughness of the steel counterbody resulting from electroerosion.

Known sintered material for contact plates of current collectors of the following composition, wt.% [2]:

Nickel 1-10 Copper 5-30 Tin 1-5 Lead 8-20 Boron nitride 1-10 Iron rest

The disadvantages of this material are low electrical conductivity, low mechanical properties and high wear rate at a current density above 100 A / cm ² under sliding conditions on the counterbody with increased roughness (Ra> 0.63).

The closest in purpose, phase composition and the achieved result is a composite containing wt.%: Graphite - 8-18, copper - 8-20, iron - the rest [3].

The disadvantages of this composite are low mechanical properties, wear resistance and electrical conductivity, which are especially manifested when sliding with a current density of more than 100 A / cm ² .

The objective of the invention is to develop a material for a high-current sliding electrical contact with increased wear resistance in a dry sliding electrical contact, increasing the mechanical properties of the current collector with satisfactory electrical conductivity of the friction zone.

To achieve the specified technical effect, a composite material is proposed that contains copper, graphite, and additionally contains particles of steel ШХ15, processed from grinding slurry of bearing production in the following ratio of components, wt.%:

Copper 18-46 Graphite 2-3 Recycled ShH15 steel rest

Comparison with the prototype allows us to conclude that the claimed material differs from the known introduction of a new component, namely ШХ15 steel, processed from grinding sludge from bearing production, as well as the absence of refractory (boron nitride) and low-melting (tin, lead) components. The increase in mechanical properties occurs due to the formation of a matrix-filled structure. Low electrical resistivity and low porosity of the material were obtained due to the combination of an extended copper matrix and particles of recycled steel SHX15 uniformly located in it, as well as due to the partial filling of particles of steel SHX15 with developed internal porosity of micron and submicron size with copper. Such a composite structure has no analogues, because the composition Cu-steel ШХ15-graphite is presented at two scale levels - at the level of the composite as a whole (sample scale, i.e., more than 1 mm) and at the particle level of ШХ15 steel (particle scale, i.e., less than 100 μm). The increase in wear resistance occurs due to relaxation of the deformation of the material of the friction zone by phase transformation. The surface layer in this case has the properties of a viscous fluid and can be deformed without the accumulation of structural defects with satisfactory ductility, which allows forming a sufficiently large total area of the actual contact. The last factor determines the low electrical resistance of the friction zone.

The introduction of copper more than 46% reduces the hardness and wear resistance, and also increases the coefficient of friction. A copper content of less than 18% leads to an increase in brittleness, a decrease in the thermal and electrical conductivity of the tribocontact. The introduction of graphite contributes to the processes of pressing and sintering, improves the tribological characteristics of the contact. A graphite content of less than 2% increases the coefficient of friction and increases adhesion to the counterbody, and more than 3% leads to a decrease in the strength and electrical conductivity of the tribosystem as a whole.

Example.

The powders of the components are mixed in a vibratory mill for 2 hours. The dried powder mixture is placed in a steel mold with upper and lower punches and pressed at room temperature with a pressure of 550 MPa. Pressed briquettes are sintered at a temperature of 1080-1100 ° C in vacuum.

A metallographic study showed that the composites have a matrix-filled structure. Electrical resistivity, porosity and mechanical properties are determined by standard methods.

The maximum achievable current density and the corresponding wear rate, contact electrical resistance, friction coefficient, porosity, electrical resistivity, hardness and flexural strength of sintered composites based on recycled steel ШХ15 are presented in the table.

The wear intensity Ih is determined by the ratio Ih = h / L, where h is the change in the height of the sample due to wear, L is the friction path (36 km). It is believed that the catastrophic wear regime is realized at Ih ~ 100 μm / km. The maximum achievable current density jk, the electrical resistance of the friction zone Rk and the corresponding wear rate are presented in the table. Sliding with the current collector was carried out at a speed of 5 m / s along the counterbody of steel 45 (50 HRC) with a roughness of 1.25.

Information sources

1. Pat. Japan 48-20963. Wear-resistant sintered alloy based on copper, publ. 06/25/73.

2. A.S. 465439, C22C 33/02, H01H 1/02, publ. 03/30/1975.

3. RU 2126457, C22C 33/02, B60L 5/08, H01H 1/02, publ. 02.20 1999.

Table Cu SHX15 FROM j _to A / cm ² I _h , μm / km R _to f P, ρ, HB σ _and Ohm % Ohm * m MPa MPa one 22 76 2 170 96 0.11 0.24 9 0.15 1700 - 2 eighteen 79 3 250 86 0.13 0.21 16 0.25 2190 1163 3 24 73 3 310 62 0.063 0.23 eleven 0.21 2050 905 four 46 51 3 170 78 0.058 0.27 eighteen 0.17 820 221

Claims (1)

A material for a high-current sliding electrical contact containing copper, graphite, characterized in that it additionally contains particles of steel ШХ15, processed from grinding slurry of bearing production, in the following ratio of components, wt.%:
Copper 18-46 Graphite 2-3 Recycled ShH15 steel Rest