RU2571296C1 - Composite with graphitized carcass impregnated with copper-based matrix alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: claimed composite contains graphitized carcass impregnated with copper-based matrix alloy including, wt %: the mix of powders of lithium tetraborate and copper-boron foundry alloy with the content of lithium 6%, boron 29% of 0.5-3.0, phosphorus of 4.0-8.0, copper making the rest.

EFFECT: higher electric conductivity and strength.

7 ex, 1 tbl

Description

This invention relates to the field of metallurgy and the production of cast composite materials and castings, can be used to impregnate composite materials having a carbon-graphite frame, which operate under friction conditions as electrical products, such as current collectors, pantograph inserts, electrical brushes, etc. . the details.

Known copper alloy having the following chemical composition (wt.%): A mixture of powders of titanium boride and titanium with a boron content of 30% and titanium 70%, respectively, 0.1-11.0; Cu - the rest (Patent Ru No. 2447171, IPC C22C 9/00; C22C 1/04, publ. 04/10/2012). The alloy provides an increase in the quality of a composite material having a high density and strength, as a result of impregnation with this matrix alloy, but has low electrical properties.

Known composite material containing titanium boride in a copper matrix containing 60 wt.% Titanium and 40 wt.% Boron obtained by powder metallurgy (GB Patent No. 2419604, IPC B22F 3/10; C22C 1/05, publ. 26.01.2006 ) The material has high tensile strength. The disadvantage of this material is its low density and electrical properties.

A composite material is known, consisting of a carbon-graphite frame impregnated with a copper-based matrix alloy, containing, wt.%: Phosphorus 4.0-8.0, zinc 0.5-12.5, iron 0.5-1.5, copper - the rest (Patent RU No. 2466204, IPC C22C 49/02, B22F 3/26, C22C 1/10, publ. 05.31.2011). This material has good compressive strength, but has poor hardness and electrical conductivity.

Known copper alloy having the following chemical composition (wt.%): Aluminum 3.0-12.0; calcium 0.01-0.06; boron 0.01-0.05; tellurium 0.0001-0.001; copper - the rest (Patent RU No. 2026396, IPC C22C 9/01, publ. 09.01.1995.). The alloy has a high tensile strength at medium density and poor electrical conductivity.

The closest in technical essence is a composite material containing a carbon-graphite frame impregnated with a copper-based matrix alloy containing phosphorus 4.0-11.0 wt.% And additionally oxygen-free copper 5.0-18.0 wt.% As an inoculator, (Patent RU No. 2430983, IPC С22С 9/00, C22C 1/04, published on 10/10/2011). The composite material has good strength, but insufficient density and conductive characteristics, and the alloy has insufficient fluidity.

The objective of the invention is to provide a matrix alloy with high casting and conductive properties.

The technical result of this invention is a composite material having increased electrical conductivity while maintaining strength characteristics.

The technical result is achieved in a composite material containing a carbon-graphite skeleton impregnated with a phosphorus-based matrix alloy based on copper, the alloy containing a mixture of lithium tetraborate powders and copper-boron alloys with a content of 6% and boron in a mixture of 29%, in the following ratio of components alloy, wt.%:

Mixture of lithium tetraborate powders and ligatures copper-boron with content in a mixture of lithium 6% and boron 29% 0.5-3.0 Phosphorus 4.0-8.0 Copper Rest

The content of the mixture of Li ₂ B ₄ O ₇ powders and copper-boron ligature 29% boron and 6% lithium is achieved by adding copper-boron ligature (Standard SM121C) with boron content of 2.0 wt.%, Copper - the rest. The use of a mixture with the declared content of Li and B leads to an increase in interfacial interaction between the impregnating copper-based alloy and graphite, an increase in fluidity and a decrease in the wetting angle to 40 °, which allows the matrix alloy to penetrate better into the pores of the carbon-graphite frame.

Lithium in a mixture of Li tetraborate and Cu-B master alloy, with a Li content of 6% and B 29%, increases the strength properties and reduces the ductility of the alloy. With increasing lithium content, the strength and yield strengths of alloys increase, and their plastic properties decrease. When alloyed with lithium, the electrical characteristics of the alloy increase, since lithium is a superconducting metal.

Boron serves as a sealant for many composite materials. In copper alloys, boron effectively reduces grain size, which significantly improves the mechanical properties of the alloy and reduces the number of internal defects of the final products, increases the fluidity of the alloy, and in copper alloys, boron prevents grain growth during heating. In this case, boron does not adversely affect the electrical conductivity.

The combined effect of boron and lithium on copper alloys contributes to the formation of double phases of copper - boron and boron - lithium solid solutions, which improves the conductive and strength characteristics of CM.

Introduction to the alloy composition of a mixture of powders of lithium tetraborate and copper-boron ligature less than 0.5 wt.% Is not enough, because will not lead to any significant deoxidation in the structure of the alloy and an increase in the electrical conductive and casting properties of the alloy and, accordingly, does not improve the properties of CM.

Introduction to the alloy composition of a mixture of powders of lithium tetraborate and copper-boron ligature more than 5.0 wt.% Leads to cost overrun of the expensive additive, its irrational use in the absence of further increase in casting and conductive properties of the alloy and the composite material obtained on its basis.

Specific Manufacturing Example

EXAMPLE 1

The alloy is prepared as follows: GOST 4515-93 phosphate grade MF9 grade copper (with a copper content of 90.5-91.5 wt.%, Phosphorus - 8.5-9.5 wt.%) At a temperature of 850 ° C is added 2.5 wt.% A mixture of powders of lithium tetraborate and copper-boron ligature, pre-prepared and placed in a copper tube with sealed ends, including: copper-boron ligature (containing boron - 2.0 wt.%, Copper - the rest). Melting is carried out in an inert gas in an induction furnace (Indutherm VC-400 vacuum injection molding machine). The design of the furnace allows continuous mixing of the alloy ingredients in a vacuum and casting under argon pressure.

KM is produced by impregnating a frame from carbon graphite of the AG-1500 grade with a matrix alloy under a pressure of 12 MPa at a temperature of 1105 ° C and holding under pressure for 20 minutes.

As the technological characteristics of the alloy, its fluidity, the wetting angle with respect to the carbon-graphite frame in air, hardness and electrical conductivity were studied.

As the technological characteristics of CM, the density and compressive strength were determined.

To determine the surface tension of the alloys, carbon-graphite substrates were made on which alloy samples were placed. The weighed substrates, in turn, were placed in a boulder tube for heating in a tubular furnace. Then, the surface tension was calculated by the Darcy method from the drop contour. The measurement of the contact angle and the subsequent calculation of surface tension were carried out at a temperature of 850 ° C.

The fluidity of the alloy with respect to the carbon-graphite frame was determined by the depth of flowing of the alloy into the holes with a diameter of 1.0 mm, made in the bottom of the carbon-graphite glass. For this, a carbon-graphite cup of a smaller diameter was inserted into a graphite glass with a conical base, internal dimensions: height 65 mm, diameter 22 mm, with 4 holes made in it. Thus, drops of the melt flowing through the holes were collected at the bottom of the outer graphite cup. Drops were weighed and the volume of metal flowing through the holes was calculated. Then calculated the depth of flowing of the alloy into the holes. Penetration was determined as the average value of the leakage depth from three experiments. The tests were carried out in an argon atmosphere.

The isothermal exposure time of the alloy at a temperature of 1105 ° C was 20 min, the constancy of the metallostatic pressure on the bottom of the glass was ensured by pouring the alloy into the glass of one level along the upper edge.

The hardness of the matrix alloy was determined on cylindrical samples with a diameter of 20 ± 0.2 mm and a height of 20 mm on a Brinell press.

The specific electrical conductivity of the matrix alloy was determined on cylindrical samples with a diameter of 20 ± 0.2 mm and a height of 5 mm by the eddy current method on a Vikhr-AM instrument according to GOST 27333-87 after preliminary preparation of the samples according to GOST 193-79.

CM density was determined as the percentage of filling of open pores. The volume of open pores was determined on samples pre-impregnated with water in a vacuum, with subsequent determination of the weight and volume of the water that filled the sample. The convergence of the results is within a 1% error with the determination of open porosity on the mercury porosimeter.

The compressive strength of CMs was determined on cylindrical samples with a diameter of 20 ± 0.2 mm and a height of 20 mm when setting the tensile testing machine to a maximum load of 10,000 N.

The research results are presented in the table.

EXAMPLES 2-7

The preparation of the alloy and the conditions for its testing are similar to example 1.

Examples for varying the composition of the alloy, justifying the effect of the content of lithium tetraborate on the technological characteristics of the alloy and CM, are given in the table.

Thus, the proposed composite material containing a carbon-graphite skeleton impregnated with a copper-based matrix alloy containing phosphorus and a mixture of lithium tetraborate powders and copper-boron alloys has enhanced electrical conductivity while maintaining the strength characteristics of the composite material.

Claims (1)

A composite material containing a carbon-graphite skeleton impregnated with a phosphorus-based matrix alloy of copper, characterized in that the alloy contains a mixture of lithium tetraborate powders and copper boron alloys with a content of 6% lithium and boron in a mixture of 29% in the following ratio of alloy components, wt .%:
a mixture of lithium tetraborate powders and ligatures copper-boron with content in a mixture of lithium 6% and boron 29% 0.5-3.0 phosphorus 4.0-8.0 copper Rest