JPS60155635A - Electrical contact material - Google Patents

Abstract

PURPOSE:To obtain an electrical contact material for medium electric current having improved resistance to welding and consumption by using a composite Ag alloy contg. Bi and Li oxides by a specified amount each (expressed in terms of metal). CONSTITUTION:An electrical contact material is made of a composite Ag alloy contg. 3-6wt% (expressed in terms of Bi) Bi oxide and 0.05-3wt% (expressed in terms of Li) Li oxide. It is effective to add 0.01-0.5wt% Fe, Ni or Co as an Fe group element, and 0.01-0.5wt% one or more kinds of metallic elements each having smaller oxide forming free energy than Li may be added so as to inhibit actively the coarsening of the grains. The metallic elements include Al, Si and Ca.

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to an electrical contact material, specifically an electrical contact material made of a composite alloy containing silver and other metal oxides, and is used for various electrical devices such as electromagnetic contactors and relay breakers. It is used for electrical contacts built into.

[Background technology]

Electrical contact materials are generally required to have characteristics such as low wear, resistance to welding, and low contact resistance. Relays that function as input and output of a circuit are especially required to have weldability that can withstand the rush current that flows during input and output.

Conventionally, electrical contact materials based on silver-cadmium oxide, silver-nickel, and silver-tin oxide are widely known.

Silver-cadmium oxide has excellent adhesion resistance, silver-tin oxide has excellent wear resistance, and silver-nickel has excellent contact resistance characteristics.

Recently, the silver-bismuth oxide system has attracted attention as an electrical contact material with excellent welding resistance. It is disclosed that the two types are contained in a total amount of 0.05 to 3% by weight.

In any case, the performance of τ as well as welding resistance, contact resistance characteristics, and abrasion resistance influences the reliability of the contact opening/closing operation, and if reliability is lacking, the equipment will malfunction. provoke.

[Purpose of the invention]

The present invention provides all electrical contact materials useful for medium current applications, which have improved welding resistance and abrasion resistance of silver-bismuth oxide electrical contact materials.

[Disclosure of the invention]

In other words, the present invention provides an electrical contact material consisting of a composite alloy containing silver and other metal oxides, in which bismuth is added as the other metal oxide to more than 6% by weight on a metal basis, and lithium is added in an amount exceeding 6% by weight on a total metal basis. The present invention provides an electrical contact material characterized by containing 0.05 to 3% by weight.

The present invention will be described in detail below.

The present invention is characterized in that the concentration of bismuth oxide is higher than that of conventional silver-bismuth oxide containing lithium oxide. In other words, bismuth oxide exhibits high properties at the 0.1% by weight level, and tends to deteriorate as the concentration increases up to 3% by weight. It was ensured that the weldability and wear resistance were improved.

This is dispersed in a silver matrix, and as a result of X-ray diffraction, bismuth alone and lithium alone are internally oxidized to α and βB + 20s.
It has been found that LiBiO2 is generated, and this is a cause for concern. In this way, the production of bismuth oxide and composite oxides of lithium and bismuth, which contribute to wear resistance and welding resistance, exceeds triple ist on a metal basis and reaches up to 6% by weight, and lithium t-0.05 weight% on a metal basis. % to 3% by weight. That is, if bismuth is less than 3% by weight based on the metal, the effect of improving both welding resistance and abrasion resistance will be small, and if it exceeds 6% by weight, precipitation will occur, and as a result, a uniform structure will not be obtained. Lithium is 0.055 based on metal standards
This is because if the amount is less than 3% by weight, there is no effect of addition, and if it exceeds 3% by weight, the oxide will significantly aggregate at grain boundaries due to internal oxidation treatment.

More effective is the addition of iron group elements, iron, cobalt, or nickel. Since bismuth oxide, a composite oxide of lithium and bismuth, has a spherical shape, it is well dispersed, but on the other hand, it tends to become enlarged, so it is effective in suppressing this enlargement. This effect is due to the effect of iron group elements on refining crystal grains, which ranges from 0.01 to 0.
．． A range of 5% by weight is suitable. That is, 0.01 weight i
If it is less than s, there is no effect of refining (and if it exceeds 0.5% by weight, segregation will occur and the contact performance will be impaired.

In order to more actively prevent enlargement, it is recommended to add a metal element that has a lower free energy of oxide formation than lithium. When these metal elements are added and internally oxidized, the oxidation process is such that these metal elements are first oxidized and precipitated as a nucleus, and bismuth, lithium oxides, and their composite oxides are precipitated around this nucleus. This is because it is possible to construct an electrical contact material in which fine metal oxides are dispersed in the chains. -These metal elements with low free energy of formation include magnesium, aluminum, silicon, calcium, etc. Any 11! More than i is selectively added and subjected to internal oxidation. The appropriate amount to add is 0.01 to 1% by weight. i.e. 0.0
If the amount is less than 1% by weight, no effect will be observed, and if it exceeds 1% by weight, the processability into contacts will be significantly inhibited.

As mentioned above, the internal oxidation type electrical contact material in which spherical bismuth oxide or bismuth and lithium oxide is dispersed in a predetermined amount has excellent welding resistance and wear resistance. Further improvements in these performances are possible.

Examples are given below.

(Example) First, in addition to the main elements silver, lithium, and bismuth, additional elements iron, cobalt, aluminum, magnesium, silicon, and calcium were selected and combined in a high-frequency furnace in an argon atmosphere. Unraveling surface 18X12111
The mixture was cast into a square mold (No. 1) to obtain an alloy ingot having a desired composition. This ingot was subjected to heating lamp annealing at 700° C. for 10 hours in a nitrogen atmosphere. Next, since this ingot has poor workability and cannot be rolled, a cutter is used to cut this ingot to a thickness of l.
It was cut into pieces (2) and processed as a plate material through a punching step and a molding step to form a fixed contact 45 and a movable contact φ5×12R, and was heated continuously in oxygen at 700° C. for 20 hours to undergo internal oxidation.

When the 1+fr surface of the contact obtained by internal oxidation was observed under a metallurgical microscope, a structure in which spherical oxides were dispersed deep inside was confirmed, and it was confirmed that the internal oxidation had been completed.

Next, the contacts thus obtained were subjected to an opening/closing test using an ASTM type sliding point tester. The conditions are as follows.

Forming pressure AC 100V Soldering current Rush current 118A, Steady 20A Contact force 100
I Opening force 150.9 Number of opening/closing times 1 x 104 times Number of contacts 3 pairs The test results are shown in the table below.

In addition, both the number of welding times and the amount of wear are expressed as the average value per pair, fc0, and the comparative example was made under the same conditions as the example.

〔Effect of the invention〕

As shown in the various compositions in the above embodiments, this invention provides an excellent electrical contact material in which the number of times of welding and the amount of wear are reduced by increasing the magnetization of bismuth.

Claims (4)

[Claims] (1) In an electrical contact material made of a composite alloy containing silver and other metal oxides, the other metal oxides include bismuth of more than 3% by weight and 6% by weight on a metal basis, and lithium of 0.05 to 6% on a metal basis. An electrical contact material characterized by containing triple f%. (2) The electrical contact material according to claim 1, which contains an iron group element of 0.01 to 0.5 weight percent on a metal basis. (3) The electrical contact material according to claim 1 or 2, characterized in that it contains 0.01 to 1% by weight of a metal oxide smaller than the free energy of formation of lithium oxide, 3 (4) The electrical contact material according to claim 3, in which the metal oxide contains one or more selected from the group consisting of magnesium, aluminum, silicon, and calcium.