JPH0313295B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to electrical contact materials used in equipment that conducts current and switches on and off. In addition, it is particularly aimed at improving the properties of Ag-WC alloys. Conventionally, Ag-WC alloys have excellent arc resistance and welding resistance;
Widely used as contacts in equipment such as switches. However, in recent years, devices such as no-fuse breakers, disconnectors, switches, and other devices have become smaller and more sophisticated, and as a result, the load on contact materials has become severer, and contact performance has become worse. Improvement is strongly required. Additionally, due to the miniaturization of devices, there is a tendency for contact dimensions to become smaller and contact pressure to decrease, resulting in increased wear and tear that occurs when current is turned on or off, increased scattering, welding of contacts, deterioration of insulation of devices, and even lower rated current. Problems have arisen in that the temperature tends to rise when opening and closing. A contact made by adding graphite (Gr) to an Ag-WC alloy was developed as one way to meet the demand for improved characteristics. In this contact, Gr becomes a reducing gas due to the arc heat generated when opening and closing, preventing oxidation of WC, suppressing temperature rise, and increasing welding resistance due to the lubricity of Gr. However, the addition of Gr causes consumption and
The drawback was that the insulation properties deteriorated. For this reason, in small, high-performance circuit breakers and switches, the movable contacts contain Ag.
-The combination of Ag-WC-Gr contacts had to be used for WC contacts and fixed contacts. 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, high-performance devices, and the arc heat generated during opening and closing often causes abnormal temperature rises, wear, insulation deterioration, and welding, and further improves contact performance. is requested. The present invention has been made in view of the above points, and has welding resistance, wear resistance, and insulation resistance.
In addition, the present invention provides a contact alloy with low temperature rise and excellent practicality. Furthermore, the alloy of the present invention provides an inexpensive contact alloy that can be used as a contact even if the amount of expensive silver is considerably reduced. The alloy according to the invention contains 4A in iron group metal and silver.
An electrical contact characterized by containing carbides of group 5A and 6A metals, nitrides and graphite of group 4A, 5A and 6A metals dispersed therein, and in which some or all of the carbides are dissolved in the iron group metal. It is the material. The inventors previously conducted various studies on alloys in which iron group metals and various carbides were added to silver, and as a result, they found that alloys in which some or all of the carbides were solidly dissolved in the iron group metals were generated when the current was switched on and off. It has been found that there is extremely little wear and tear due to arc heat, and the effect of reducing insulation deterioration and welding of equipment. Iron group metals and carbides have poor oxidation resistance and are oxidized by arc heat generated during opening and closing, increasing contact resistance and increasing the temperature of the equipment. Therefore, when Gr, which has excellent reducing properties, is added to the above contact alloy to prevent the oxidation of iron group metals and carbides, Gr decomposes with the heat of electrical switching and generates reducing gas, preventing the oxidation of iron group metals and carbides. It was found that the lubricity of Gr increases welding resistance, reduces contact resistance, reduces equipment temperature rise, and improves welding resistance due to the lubricity of Gr. In other words, carbide is solid-dissolved in iron group metals, which have excellent mechanical strength and bonding strength at high temperatures, to improve wear resistance and welding resistance. By adding conventional Ag-WC
We were able to obtain an alloy with high performance welding resistance, abrasion resistance, insulation resistance, and temperature rise characteristics that could not be expected from the Ag-WC-Gr type or Ag-WC-Gr type contacts. As a result of further research, the inventors found that
When nitrides of group 4A, 5A, and 6A metals are further added to this system, these nitrides react with carbides via Fe group metals during sintering at temperatures above the melting point of silver, and the carbides become fine. It was found that deformation at high temperatures was reduced. Furthermore, it has been found that the addition of these nitrides significantly improves arc wear resistance. These characteristics are thought to be due to the fact that the nitrides react with the dispersed Gr due to the arc heat generated during opening and closing to form carbides, and this reaction is an endothermic reaction and releases _N2 gas, which has an arc-extinguishing effect. The figure shows the free energy change of this reaction, and it can be seen that this reaction proceeds almost at 1500㎜. Iron group metals are Fe, Co, Ni, 5-60% by weight
and preferably 10 to 50% by weight. 5
If it is less than % by weight, the iron group metal will be dispersed in the silver, and solid solution precipitation of carbides will not occur, resulting in no improvement in wear resistance. Also 60
If it exceeds the weight percentage, even if Gr is added, the contact resistance will not decrease and there will be no effect of improving the temperature rise characteristics. As carbides, 4A, 5A, and 6A group carbides such as W, Mo, Ta, Nb, Ti, and Cr are effective, and the amount thereof is preferably 5 to 50% by weight, particularly 20 to 50% by weight, which improves the properties. good. If the carbide content is less than 5% by weight,
The amount of carbide in Ag is too small, resulting in insufficient adhesion resistance, and even if Gr is added in an amount of 50% by weight or more, the contact resistance does not decrease and no improvement in temperature rise characteristics is observed. As the nitride, nitrides of group 4A, 5A, and 6A metals such as Ti, Zr, Nb, Cr, and Mo are effective, and the amount thereof is preferably 0.1 to 30% by weight, particularly 0.5% by weight.
~20% by weight has good properties. This is because if it is less than 0.1% by weight, the effect on wear resistance is small, and if it is more than 30% by weight, even if Gr is added, the contact resistance increases and the temperature increase property is adversely reduced. Next, the effective range of Gr is 1 to 11% by weight, preferably 3 to 7% by weight. If it is less than 1% by weight, no improvement in temperature rise characteristics will be observed even if the iron group metal or carbide is within the above range, and if it is more than 11% by weight, it will be difficult to manufacture the alloy and it will not be practical. Next, the characteristics of the contact alloy according to the present invention will be specifically explained with reference to Examples. Example 1 Each powder was blended in the proportions shown in Table 1, Table 2, Table 3, and Table 4. After mixing, a molded body was made, and the molded body was sintered at a temperature of 1100°C in a hydrogen atmosphere. concluded.
This sintered body was pressurized again to produce an alloy with almost zero porosity. Among the alloys, those in Table 4 are conventional alloys as comparative materials.

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[Table] About the alloys made as described above
The current carrying characteristics and wear characteristics were evaluated using an ASTM testing machine. The conditions are AC100V, 50A,
pf1.0, contact pressure 200gr, opening force 200gr, contact shape 5x5x1.5tmm, and opened and closed 20,000 times.
Table 5 shows the results of voltage variation and amount of wear after 20,000 openings and closings.

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[Table] Example 2 Movable contacts 4× were made from the alloys prepared in Example 1, A1, B2, C2, and comparative materials D1, D2, D3, D4.
After cutting the fixed contact to a size of 8 x 8 x 2 mm to a size of 7 x 2 mm, it was bonded to the base metal by resistance brazing, and this was assembled into a 50A rated wiring cutter and tested under the test conditions shown below. As a result of contact performance evaluation, Table 6 was obtained. Test conditions: Overload test: AC220V, 200Apf 50 times Endurance test: AC220V, 50Apf 54 times Temperature rise test: AC220V, 50A 2H Short circuit test: AC220V, 7.5KA pf0.5, 1PO-CO,
2PO−CO

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[Table] As shown in 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 excellent contact performance as described above, but also contains a large amount of iron group metals and carbides, and the amount of expensive silver can be significantly reduced, so it is of high industrial value.

[Brief explanation of the drawing]

The figure shows the change in free energy when carbide is produced from nitride and graphite.

Claims (1)

[Claims] 1. 5 to 50% by weight of carbides of metals from groups 4A, 5A, and 6A of the periodic table of elements, 1 to 11% by weight of graphite, 5 to 60% by weight of iron group metals, 4A, 5A, and 6A. An electrical contact material comprising a sintered material containing 0.1 to 30% by weight of group metal nitride and the balance being silver. 2 The carbide is at least one of tungsten, molybdenum, tantalum, niobium, titanium, and chromium.
The electrical contact material according to claim 1, characterized in that it is a carbide of seeds. 3. The electrical contact material according to claim 1, wherein the nitride is at least one of titanium, zirconium, niobium, chromium, molybdenum, vanadium, and tantalum.