JPS5823119A - Method of producing electric contact material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing electrical contact materials used in devices that conduct current and switch.

In particular, the purpose is to improve the properties of Ag-carbide alloys. Among Ag-carbide alloys, Ag-WC alloys have been widely used as contacts in devices such as air breakers and switches due to their excellent arc resistance and welding resistance.

In recent years, devices such as air circuit breakers and switches, including no-fuse breakers, have become smaller and more sophisticated, and as a result, the load on contact materials has become severer, making it necessary to improve contact performance. is strongly requested. In addition, due to the miniaturization of devices, contact dimensions are becoming 74% smaller and contact pressure is decreasing, which increases the wear and tear that occurs when current is cut off, increases the amount of scattering, causes welding of contacts, deteriorates the insulation of devices, and increases G when switching at the rated current. This poses a problem in that the temperature is likely to rise.

One of the ways to respond to such requests for improved characteristics is A.
A contact made by combining graphite (Gr) with g-WO alloy has been developed. This contact opens and closes 4: Due to the arc heat, Gr becomes a reducing gas and prevents oxidation of wC.

This has the effect of suppressing temperature rise and increasing welding resistance due to the lubricity G of Gr. However, the addition of Gr had disadvantages such as consumption and deterioration of insulation properties. For this reason, in small high-performance circuit breakers and switches, the movable contacts contain Ag.
-We contacts and fixed contacts are Ag -WC! -Gr contacts had to be used in combination. However, changing and combining materials for the movable part and the fixed part makes parts management extremely troublesome. Furthermore, even when using such a combination, the contact pressure is small in recent small and high-performance devices, and the arc heat generated during opening and closing often causes abnormal temperature rises, wear, insulation deterioration, and welding, and further improvements in contact performance are required. has been done.

The present invention has been made in view of the above points, and provides a method for manufacturing a highly practical contact alloy that has welding resistance, abrasion resistance, and insulation resistance, and has low temperature rise. It is. Furthermore, the method for producing the alloy of the present invention provides a method for producing an inexpensive contact alloy that can be used as a contact even when the amount of expensive silver is considerably reduced.

The method for producing the alloy according to the invention includes iron group metals, silver, IVa%
Va%VIa%■ A mixed powder of group a metal (A) and graphite is molded and sintered at a temperature higher than the melting point of silver, and during sintering, 7 parts or all of the metal (A) is converted into carbide to form silver and iron group metal. It is characterized by being dispersed in metal.

A method for manufacturing alloy 1 according to the present invention will be described below.

The inventors discovered that silver has a high melting point that is difficult to solidly dissolve in iron group metals and silver.
a, Va % Vla %■ As a result of various studies on alloys to which group a metals (A) are added, alloys in which part or all of the carbides of metal (A) are dispersed in the iron group metals have a high current It has been found that there is extremely little wear and tear due to the arc heat generated during opening and closing, and the effect of reducing insulation deterioration and welding of equipment. It is known in the field of heat-resistant alloys that carbides of metal (A) dispersed in iron group metals have excellent strength and degree of bonding at high temperatures. It has been discovered that the performance as a contact point is significantly improved when an alloy is made of a combination of the following.

Metal (A) and Gr tend to react to form carbides and further react with iron group metals, but these reactions generally only occur at high temperatures, but when Ag is present, Ag becomes a liquid phase during sintering. It was found that the reaction was promoted through this liquid phase. The reaction of the metal (A) with ()r and the iron group metal depends on the sintering temperature and time.For example, at /100C, the metal (A) becomes a carbide if sintered for more than S hours.

However, iron group metals and metals (A) or metals (A)
Carbide has poor oxidation resistance and is oxidized by the arc heat generated during opening and closing, increasing contact resistance and increasing humidity in the equipment. For this reason, when Gr, which has excellent reducing properties, is added to the above contact alloy to prevent oxidation of iron group metals, gold M(A), or carbides of metal (A), Gr decomposes with the heat generated during electrical switching and produces reducing gas. occurs in iron group metals and metals (
A) It was found that metal (Gr) or metal (chrysanthemum carbide) is prevented from oxidation, contact resistance is kept low, temperature rise of equipment is reduced, and welding resistance is improved due to the lubricity of Gr.

In other words, carbides of metal (N) are dispersed in the chain of iron group metals, which have excellent mechanical strength and bonding strength at high temperatures, to improve wear resistance and welding resistance, and to improve reducing properties and lubricity. By adding Gr, conventional Ag-wa system and Ag-
It was possible to obtain an alloy that has high performance welding resistance, wear resistance, insulation resistance, and temperature rise characteristics that could not be expected from We-Gr type contacts.

Iron group metals are FeX C! o, N1, etc., in an amount of 5 to 60% by weight, preferably 20 to 30% by weight.

At 5% by weight or less, the iron group metal is dispersed in the chain, and the metal (A)
Dispersion of carbides does not occur and wear resistance does not improve. Also 6
If it is 0% by weight or more, even if Or is added, the contact resistance will not decrease and there will be no effect of improving the temperature rise characteristics.

Gold ff (A) is W%MO1Ta, Nb5Ti, O
r.

IVa% Va % Vla %■a of MnX'V etc.
Group metals (A) are effective, and their grade is 5 to 70.
% by weight is preferable, and 20-jtO weight % has particularly good properties. When the metal (A) is 5% by weight or less, the metal (A) in Ag is
), or the metal (A) has too little carbide, resulting in insufficient adhesion resistance, and at 70% by weight or more, even if Gr is added, the contact resistance does not decrease, and no improvement in temperature rise characteristics is observed. Next, the effective range of Gr is /-11% by weight, preferably 3 to 7% by weight.

If it is less than 1% by weight, iron group metal, metal (A) or metal (
Even if the carbide content of A) is within the above range, no improvement in temperature rise characteristics is observed, and if it exceeds 1/wt%, alloy production is difficult and impractical. It should be noted that θ which does not impair the purpose of the present invention
,/wt% of AlXSi, Sθ, To, Bi, Z
Metal elements such as nXQd, nXSn, (1!a, Na, etc.) may be included.

The above alloys can be obtained by sintering at a temperature higher than the melting point of silver. The atmosphere is preferably a reducing gas such as H2εo1 ammonia decomposition gas.

Next, the characteristics of the contact alloy according to the present invention will be specifically explained using examples.

Example/ Each powder was blended in the proportions shown in Table 1, Table 2, Table 3, and Table 3. After mixing, a molded body was made, and the molded body was sintered at a temperature of 1iooc in a hydrogen atmosphere. concluded.

When sintered for 1 hour, a portion was dispersed as carbide in the silver or iron group metal. After sintering for 5 hours, all of the material turned into carbide and was dispersed in silver and iron group metals.

AI, A3, AS1A7, A9 are 7 hours, Ako, Alz
AA, kg% A10 was sintered for S hours. Table 2,
The alloys in Table 3 were sintered for S hours. This sintered body was pressurized again to produce an alloy with almost zero porosity. The alloys in the table are conventional alloys for comparison.

Table l Unit: Weight % Table λ Unit double weight % Table 3
Unit: Weight % Unit: Weight % The alloys prepared as described above were evaluated for current conduction characteristics and wear characteristics using an ASTM tester.

The conditions are A a 10OV N □A, pf/
, O, contact pressure 20θgr, separation force 20θgr, contact shape left x rim x 1.5ttnm, and opening and closing were performed 20,000 times. Table 5 shows the results of voltage variation and amount of wear after 20,000 times of opening and closing.

Table S Example λ Movable contacts were made from the alloys prepared in Example 1, A6, B2, (, l, and comparative materials D/, D2, D3, and D).
After cutting the fixed contact to the same size as the fixed contact, it was bonded to the base metal using resistance brazing, and this was assembled into a circuit breaker with an θA rating, and the contact was tested under the test conditions shown below. As a result of performance evaluation, Table 6 was obtained.

Test conditions: Overload test: Aat20V, 2θQApf 30 times durability test: AC CocoOv-% TaθApf tak times temperature rise test: Ac1.20V, 30A 2H
Short circuit test: AO220Vz 7-3KA p
fO-Left/PO-Co1,2PC1-C! 0 As shown in Table B of Table 6, it can be seen that the alloy of the present invention has low wear, low temperature rise, high dielectric strength, and high performance contact characteristics.

The alloy of the present invention not only has poor contact performance as described above, but also contains a large amount of iron group metals and metal (A), and can greatly reduce the amount of expensive silver, so it is of high industrial value. It is.

Applicant: Sumitomo Electric Industries, Ltd.

Claims (1)

[Claims] (7/) iva % VEL % of the periodic table of elements
VTa % ■ A powder mixture consisting of 3 to 70% by weight of group A metal (4), 7 to 71% by weight of graphite, 5 to 60% by weight of iron group metal, and the balance silver is molded and sintered at a temperature above the melting point of silver. A method for producing an electrical contact material, characterized in that part or all of the metal (A) is dispersed as a carbide in silver or an iron group metal during sintering. (4 metals (N is tungsten, molybdenum, tantalum,
The method for producing an electrical contact material according to claim (1), wherein the metal (A) is at least one of niobium, titanium, chromium, manganese, and vanadium. (The method for producing an electrical contact material according to claim (1), wherein the tri-iron group metal is at least seven of nickel, iron, and cobalt.