CS248368B1 - Copper, nickel and boron based alloy for contact elements in electrical engineering - Google Patents

Abstract

The solution concerns an alloy based on copper, nickel and boron for contact elements in electrical engineering, the solid skeleton of which is made of tungsten or molybdenum, most often supplemented with copper, which, however, does not perfectly fill the porous material of the contacts, does not wet tungsten or molybdenum, does not form alloys with them and has a high value of cold electron emission, which can lead to voltage failure of the component. Therefore, an alloy of copper, nickel and boron with a composition of 0.1 to ^0.5 wt. % nickel, 0.02 to 0.5 wt. % boron, the rest is copper is used for impregnation of the basic tungsten or molybdenum body. This reduces cold electron emission, limits the occurrence of unsaturated sites, improves wetting and extends the life of the contact. The alloy can be used for filling the contacts of vacuum arresters, or for collectors and rings of electrical rotating machines and contact elements in electrical engineering.

Description

The invention relates to a copper-nickel-boron-based alloy for contact elements in electrical engineering, which is suitable, for example, for vacuum interrupter contacts.

Until now, vacuum interrupters contacts, especially for use in vacuum contactors up to 10 kV and currents of approximately 630 kA, are made of tungsten or molybdenum, most often filled with copper.

Tungsten or molybdenum forms a solid contact skeleton that resists vacuum arc erosion imparting mechanical strength and hardness to the contact, and limits their weldability. The vacuum interrupter contact metals are vaporized during the switching function. The metal vapors gushing from the formed cathode spot at the negative contact are ionized by the electric field between the disconnected contacts and become carriers thereof during the current flow.

There are some drawbacks to contacting, wherein the porous tungsten or molybdenum contact skeleton is saturated with copper. Copper does not wet well tungsten or molybdenum, nor does it form alloys. Therefore, often the porous metal skeleton is not fully saturated with copper.

There are places where copper contact does not fill the spaces between unsintered tungsten or molybdenum grains. These places, which are difficult to detect in contact, are a source of residual gases, which are gradually released by the working erosion of the contact into the vacuum interrupter space and damage its breaking properties.

This also limits the service life and reliable function of the vacuum interrupter. Another deficiency of copper, which is most often saturated with porous contact materials, is the relatively high value of cold electron emission.

The vacuum interrupter in the off state, when the contacts are spaced apart, flows in the order of milliamperes at the applied voltage of tens of kilovolts. This leads to contact heating which sometimes leads to avalanche increase in electron emission, sometimes to voltage failure of the vacuum interrupter.

The tungsten / copper or molybdenum / copper contact bodies are difficult to braze to the incoming copper bars due to the poor wettability of the tungsten and molybdenum carcasses by silver-based solders, which are most commonly used in vacuum technology.

The above-mentioned drawbacks are eliminated by an alloy based on copper, nickel and boron for the contact elements in the electrical engineering according to the invention, which consists in using an alloy with a composition of 0.1 to 1.5% by weight. % nickel, 0.02 to 0.5 wt. boron, the rest of the copper.

An advantage of said alloy is that the addition of nickel reduces cold electron emission to one tenth of the emission value compared to pure copper. Nickel in a concentration of 0.1 to 1.5 wt. due to the reaction with tungsten or molybdenum, it facilitates their wetting when the carcass is saturated and thus reduces the occurrence of unsaturated sites in the porous carcass of contact.

Boron in an amount of 0.02 to 0.5 wt. it facilitates the wetting process of tungsten or molybdenum by effectively deoxidizing the copper and the surface of the contact skeleton, reducing the opacity of the vacuum interrupter contact material during its operation and thereby mainly improving its service life. Another advantage of boron over other deoxidizing additives is the minimal impact on the electrical and thermal conductivity of the Cu-Ni-B alloy.

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Exemplary embodiment

Made of alloy of composition in% by weight. Copper 99.0%, Nickel 0.9% and Boron 0.1% a square washer of approximately 1 mm thickness was produced. The pad was placed in a hydrogen furnace and placed on a porous tungsten tablet. After heating above the melting point of the alloy, the molten alloy is sucked into the pores of tungsten by capillary forces. The hydrogen atmosphere reduces the surface oxide residues of the porous tungsten and the boron component in the alloy facilitates wetting of the tungsten.

The tungsten contact formed in this way has perfectly filled pores and meets the required characteristics for opening in vacuum contactors:

Low current ripping from current zero / low chopping /

High svaruvzdornost 8 kA.s ^_1

High breaking capacity of 5 kA

Optimal voltage properties (low transition resistance and high and long-term breakdown resistance).

The alloy according to the invention can be used, in particular, for filling the pores of the vacuum interrupters or the interrupters. for collectors and rings of electric rotating machines and contact elements in electrical engineering.

Claims (1)

Copper-nickel-boron-based alloy for contact elements in electrical engineering, characterized in that it contains 0.1 to 1.5 wt. 0.02 to 0.5 wt. boron, the rest of the copper.