FR2558640A1 - COMPOSITE MATERIAL FOR CONTACT ELEMENTS OF ELECTRICAL CONTROLS - Google Patents

Abstract

A COMPOSITE MATERIAL FOR ELECTRIC CONTACT ELEMENTS IN CONTROL DEVICES USED IN HIGH CURRENT TECHNOLOGY, IN WHICH, IN A FIRST METAL CONSTITUENT ARE INCLUDED IN A HETEROGENEOUS FORM A SECOND METALLIC CONSTITUENT AND A NON-METALLIC CONSTITUENT, MUST BE IMPROVED. AN OPTIMUM COMBINATION OF SAFETY AGAINST WELDING, WEAR RESISTANCE AND LOW HEAT RELEASE. FOR THIS PURPOSE IT IS PROVIDED THAT PARTICLES 1 OF THE NON-METALLIC CONSTITUENT ARE COATED BY THE COMMON METAL CONSTITUENT 2, AND THAT SUCH COATED PARTICLES ARE INCLUDED IN A NOBLE METAL CONSTITUENT FORMING A MATRIX 3.

Description

Composite material for contact elements of

electrical controls.

  The invention relates to a composite material for electric control contact elements used in the high currents technique, in which

  are heterogeneously included in a first con-

  as a metallic metal constituent a second common metal component and a nonmetallic component,

in the form of particles.

  A thin-film composite material of universal use, which can therefore also be used for

  contact layers resistant to electrical erosion

  DE-AS 24 48 738. Dust particles of metal, for example molybdenum, are provided with a metallic coating, for example silver and sintered on a metal support for

  forming a thin layer composite material. The inclu-

  non-metallic constituents is not indi-

cated.

  A sintered material for contacts, intended for

  electrical contact elements in control devices used in the technology of currents

  strong is the subject of DE 31 16 442 A1. It is constituted

  killed by two base metals, copper and silver, which

  present in microstructures separated from each other.

  In the base metals are included metal oxides

  such as CdO and Bi203. This is about

  contact elements which must have a high resistance to welding and good wear resistance, as well as low heating in connection with high conductivity. The results obtained in this way, however, do not appear to be sufficient for all

  uses. Especially when it comes to

  must be absolutely reliable and avoid any welding, such composite materials

are failing.

  The choice of the constituents of the composite materials depends essentially on the main specification that the contact elements must satisfy. So,

  for example, composite materials are used

  naked silver / graphite for electrical contact elements

  in high-voltage direct current or alternating current control units when the main requirement is high safety against welding. The percentage of graphite of the fixed contact elements is here from 3 to 5% by weight (K. Mler and D. Steckel "A new process for producing complex composite materials containing graphite"

DE-Z Metal 7/1982, pages 743-746).

  The resistance to welding of these composite materials is remarkable, both when switching on and when the circuit is closed, it supports extremely short circuit currents.

  strong. The composite materials silver / graphite

  0.5 to 5% by weight of graphite have a resistance

  This is a weak contact, since no solid oxides form on the contact surface. However, a high percentage of graphite which increases the

  safety against welding leads to a sharp decrease

resistance to wear.

  The wear resistance of such silver / graphite composite materials can be improved by the addition of nickel, copper or copper oxide. The making

  such materials are usually made according to the

  powder metallurgy by sintering; this results in a statistically random distribution of the carbon and nickel particles in the silver matrix. These composite materials present, especially with

  higher nickel contents than composite materials

  binary positions silver / graphite, the major disadvantage

  more heating with the current

  tinu, which results from oxidation and thus from

  increased electrical resistance of the metallic constituents

non noble ones.

  The object of the invention is to improve a composite material

  posite for electrical contact elements of the aforementioned type so as to combine high reliability against welding with wear resistance and low heating. This object is achieved by the fact that the particles of the non-metallic constituents are coated by the common metallic component, and

  that these coated particles are included in the

  of noble metal forming the matrix.

  This gives a composite material having a

  combination of safety against welding, resistance

  surprisingly favorable wear and warm-up

  ble for electrical contact elements. These favorable properties can be explained by the fact that by using nonmetallic particles coated in the metal matrix, oxidation can be prevented.

  of the common metal by its local connection with the

  non-metallic phase and possibly the reorganizing action

  ductrice of it. For this reason, we can

  drastically increase the proportion of common metal

  in such a composite material and thus reduce nota-

  the proportion of noble metal.

  The coating of the particles of the nonmetallic component

  It is advantageous to use the most common of the two metallic constituents and, in this case, the most noble of these constituents is used

  suitable material for the matrix.

  Depending on their manufacture, the particles can be

  in random or random form

  me of marbles. The thickness of the coating layer,

  which can possibly be applied by galvanisa-

  In the case of a particle size of between 0.1 and 0.3 mm, it is between 10 and 80 gm. Of course, you usually have to look for a perfectly closed coating of the particles, but you can still obtain

  good efficiency even with partial coating-

  openly. In the case of a high percentage of the constituent used for the coating, the addition of this constituent in the form of powder particle size

  appropriate may also be appropriate.

  The concept of metallic constituents may include

  both pure metals and metal alloys

  based on a metallic constituent. The constitution

  Non-metallic killing is graphite; however, the new composite material structure can be expected to have considerable advantages also with other non-metallic constituents such as

  oxides (eg CdO) and carbides (e.g.

full WC).

  The coated particles may be present in the matrix advantageously in statistically distributed

  uniform. In another embodiment suitable for

  the coated particles can be

  clusters by being grouped into filaments.

  appropriate provision may provide that the filaments

  a sheath made of a metallic material, which possibly coincides with the material of the constituent used

for the coating.

  An appropriate composition may be designed such

  so that the nonmetallic constituent is

  phite, and that the constituent used for the sheath is nickel, while the constituent used as a matrix is silver. It seems appropriate to have here a percentage of graphite of 1 to 10% by weight, a percentage of nickel of 5 to 80% by weight

  and a silver percentage of 10 to 90% by weight,

  relative to the weight of the finished composite material. A composition comprising 3% by weight of graphite, 35% by weight of nickel and 62% by weight of

weight of money.

  Alternatively, a composition may be

  of such a composite material by replacing, in

  the constituents and compositions mentioned above, the percentage

  nickel stage with a percentage of copper also between 5 and 80% by weight, preferably% by weight. The percentage of graphite and the

  of money remain within the limits indicated.

  In the drawing are schematically shown embodiments of the composite material, drawing in which: - Figure 1 is an isometric view of a contact element made of composite material with included particles; and FIG. 2 is an isometric view of a contact element made of composite material with inclusions in

  form of parallel oriented filaments.

  In FIG. 1, particles 1 of graphite having

  average diameter of 0.15 mm are provided with a coating

  2 nickel having a thickness of 40 gm. The

  Particles are in a matrix of pure silver.

  The percentage of graphite is 3% by weight, the

  percentage of nickel 35% by weight and the percentage

  of 62% by weight, based on the weight of the

finished composite material.

  In the embodiment of FIG. 2, the size of the graphite particles 1 and the thickness of the layer 2 are unchanged. The coated particles, however, were first compacted to form filaments 4 and these are included in the matrix

of money 3 being oriented.

  The manufacture of such a composite material will be

  explained below using an example.

  A nickel coating 40 gm thick is deposited by a known electrolysis process on graphite powder having a particle size of:

  <0.15 mm. The coated graphite powder is

  awarded in pure silver tubes (diameter 9 mm,

  0.3 mm wall thickness) and a bundle of these

  completed is then formed, without removal of co-

  skins, by indirect extrusion in four phases for

  form a composite cable 5 mm in diameter. The c & -

  composite manufactured in the first phase is

  several times and composite cables with embedded filaments made of coated particles are bundled as

  initial tubes and undergo another conformation.

  After four compression phases, there is in the composite material, whose structure is represented

  in Figure 2, 500,000 filaments included in the

  in silver, each of which contains the particles

graphite coated with nickel.

  In order to obtain a good metallic bond between the metallic material of the matrix and the coating material, it is also possible to use in addition

a homogenization treatment.

Claims (11)

Claims.   1. Composite material for electric control contact elements used in the high currents technique, in which a second metallic noble metal component is included heterogeneously a second common metallic constituent   and a non-metallic constituent in the form of   characterized in that the particles (1) of the   non-metallic constituent are coated by the   metal compound (2), and that these coated particles are included in the metal component noble forming a matrix (3).   2. Composite material according to claim 1, characterized   characterized in that the coated particles (1, 2) are distributed in the matrix (3) in a statistically uniform manner.   3. Composite material according to claim 1, characterized   in that the coated particles (1, 2) are   included in matrix (3) with a pre- ferential.   4. Composite material according to claim 3, characterized   characterized in that the coated particles (1, 2) are grouped together to form filaments (4) and these   are included in the matrix (3) while being oriented.   5. Composite material according to claim 1, characterized   in that the non-metallic constituent is graphite, the component used for the coating is nickel, and the constituent used as a matrix is money.   6. Composite material according to claim 5, characterized   characterized in that the percentage of graphite is 1 - 10% by weight the percentage of nickel is 5 - 80% by weight and the percentage of silver is 10 - 90% by weight,   relative to the weight of the finished composite material.   7. Composite material according to claim 6, characterized   characterized in that the percentage of graphite is 3% by weight the percentage of nickel is 35% by weight   and the silver percentage is 62% by weight.   8. Composite material according to claim 1, characterized   characterized in that the non-metallic constituent is graphite, the constituent used for the coating   is copper and the constituent used as a matrix it's money.   9. Composite material according to claim 8,   characterized in that the percentage of graphite is 1 - 10% by weight the percentage of copper is 5 - 80% by weight and the percentage of silver is 10 - 90% by weight,   relative to the weight of the finished composite material.   10. Composite material according to claim 9, characterized in that the percentage of graphite is 3% by weight, the percentage of copper is 35% by weight   and the silver percentage is 62% by weight.   11. Composite material according to claim 1, characterized in that, for a mean particle size <0.15 mm, the thickness of the coating is gm.