JPS6018736B2 - electrical contact materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrical contact materials, particularly silver-metal oxide contact materials.

Silver-cadmium oxide contacts are widely used as silver-oxide contact materials.

Silver cadmium monoxide contacts exhibit excellent properties on average in terms of contact resistance, lacquer resistance, abrasion resistance, etc. required for contact materials, and their machinability is sufficient for practical use. They are often used in load current ranges of several amperes or more, such as relays, no-fuse breakers, and power switches for household electronic equipment. However, in recent years, as safety regulations have become stricter for various types of power switching equipment, contact materials have come to be required to have even higher characteristics. Especially in household electronic equipment,
Switches are required to be easy to operate and have a four-type design, and from a safety standpoint, there is a strong desire to improve both the performance of welding, which can lead to inability to open the switch, and the performance of wear, which can lead to deterioration of dielectric strength. moreover,
As shown in the figure, in devices that obtain DC power for operation by directly rectifying AC power from a commercial power supply 1, as the surge withstand current of the diode 2 improves, the resistance of the resistor 3 for diode protection increases. There is a tendency to make the value r extremely small and to reduce the operating power of the device. This is switch 4
In addition, when performing single-wave rectification as shown in the figure, the load current of the switch becomes directional. The switch contacts are extremely susceptible to wear and tear, causing the switch to become inoperable. From this point of view as well, improvements in welding resistance and abrasion resistance are desired. Note that 5 in the figure is a load, and 6 is a capacitance. In view of the above points, the present invention provides a novel contact material that can replace silver-cadmium oxide contacts, and basically relates to improving the characteristics of silver-bismuth tin oxide contact materials. This is a proposal.

A contact material in which bismuth oxide is dispersed in a silver matrix is a contact material with low contact resistance and excellent welding resistance, as disclosed in Hakama Seki Sho 52-13356 Publication. The problem was found to be a large amount of wear and tear.

The inventors conducted various studies to improve this point, and added a tin oxide other than bismuth oxide to the silver matrix, and reacted these two oxides to form bismuth tin oxide ( We have developed a material in which this is dispersed as Bi2Sn207). Although this material showed good properties in terms of welding and abrasion resistance, it had the drawback of poor machinability.
Naturally, limits had to be placed on the amount of oxide that could be dispersed in the silver matrix.

The inventors continued to improve the material in which bismuth tin oxide is dispersed in the silver matrix, and found that machinability could be significantly improved by improving the manufacturing method of the material. By increasing the amount of oxide that can be dispersed in the matrix, it was possible to see a significant improvement in contact switching performance. That is, the material shown in the present invention has bismuth tin oxide (Bi2Sn207) dispersed as a main oxide in a silver matrix, and tin oxide (Sn02) as an auxiliary oxide.
) containing 3 to 6% by weight of bismuth and 6 to 1% by weight of tin (excluding 6% by weight), The desired performance can be achieved depending on the balance of silver.

Particularly, remarkable switching performance can be expected in a light-operation switch with a large inrush current as shown in the figure. Next, the material of the present invention will be explained in more detail.

The contact material according to the present invention contains bismuth tin oxide Bi2Sn207 and tin oxide (Sq02
) are dispersed. The former oxide (Bj2S
n207) is a mixture of bismuth oxide (Bi3) and tin oxide (Sn02) in a molar ratio of 1:2.
By heating within the range of 00, it is produced as an oxide with a yellowish stone structure. It has a melting point of 120,000 or more, exhibits sublimation properties, and when dispersed in a silver matrix, it has a remarkable effect of improving welding resistance. Therefore, as a method for dispersing bismuth tin oxide in a silver matrix, a ternary alloy of silver-bismuth-tin is heated in an oxidizing atmosphere, and bismuth and tin are selectively oxidized. However, when converted from the above molar ratio, the throat mass weight x and the tin weight y in the ternary alloy are y/x20.
57... Bismuth tin oxide (Bi2Sn207) can be generated according to the relationship [1}.

However, due to the relationship of formula '1', it is difficult to reliably convert bismuth and tin alloyed with silver into bismuth tin oxide through internal oxidation treatment, and especially for silver. When the amount of solid dissolved bismuth is large as in the present invention, the segregated bismuth becomes bismuth oxide (Bi20
3) becomes more likely to exist.

As a result, when bismuth oxide is present, an improvement effect on welding resistance is recognized, but when the previously mentioned inrush current is large and the DC load circuit is switched on and off, the amount of wear increases, which is not desirable. It does not become a state. In this sense, it is necessary to prevent bismuth oxide from existing alone by internally oxidizing a ternary alloy containing a sufficient amount of tin for bismuth. The ratio x and the tin weight ratio y are x≦y
…■ It is desirable to have the following relationship.

On the other hand, this results in the silver matrix containing tin oxide. Although tin oxide (Sn02) does not have a large effect of improving the welding resistance, it is recognized that it has the effect of reducing the amount of wear. Therefore, for the intended use of the material of the present invention, its presence is rather preferable. However, if the amount of tin oxide increases too much, the welding resistance may deteriorate, and it is not desirable to have an excessive amount of tin oxide relative to the amount of bismuth. The relationship between x and y is approximately y≦2. Ball … [3
' should be limited by '.

Further, since tin oxide has a relatively low specific gravity, its volume ratio when dispersed in a silver matrix is large. and,
Since the thermal decomposition temperature is high, there is a strong tendency to decrease the electrical conductivity of the material and increase the contact resistance. Also from this point of view, an excessive amount of bell oxide is not desirable. The material of the present invention exhibits excellent contact characteristics due to the synergistic effect of bismuth tin oxide, which has a low sublimation temperature, and tin oxide, which has a high sublimation decomposition temperature, as described above. In order to bring out the characteristics, the metal component composition of the silver-oxide contact material of the present invention must be at least bismuth 3-3.
6% by weight, 6-1% by weight of tin (excluding 6% by weight)
, the remainder is Ag.

Among these compositional components, 3% by weight is the lower limit for bismuth to be effective for the above-mentioned uses.
The upper limit is limited to 6% by weight due to segregation as a silver alloy and workability as a material. Regarding tin, it is desirable that the amount is more than 6% by weight from the viewpoint of consumability of the contact material, but the upper limit is limited to 1% by weight from the viewpoint of contact resistance and processability of the material. In addition, in the material according to the present invention, addition of a certain amount of oxide of nickel or cobalt as an additional oxide leads to improvement in contact characteristics.

In particular, it is recognized that the amount of consumption can be reduced by the addition of Ni by extinguishing arc discharge or by increasing the hardness of the material. The amount that can be added is 0.5% by weight based on the metal component composition ratio.
It is as follows. If added in excess of this amount, the solid solubility limit with respect to Ag is small, and as a result, it will be polarized during ingot production as shown in Examples below, and as a result, it will not be homogeneously dispersed as an oxide, resulting in poor workability. Moreover, adding an excessive amount has an adverse effect on the welding resistance, which is not desirable. On the other hand, the amount at which the effect of its addition is recognized is 0.1% by weight.
It is. In order to make the materials of the present invention explained above more specific, the following examples will be shown.

According to the composition of the present invention, a total of 200 ta of silver, bismuth, tin, nickel, and cobalt is melted, and silver-bismuth-
They made ingots whose main ingredient was tin.

Melting was carried out using an alumina crucible in an argon atmosphere using a high frequency furnace. In addition, when adding nickel and cobalt, a tin-nickel alloy or a tin-cobalt alloy containing 75 to 8% by weight of tin was prepared and used as a master alloy. The molten metal is 15 x 30 x 7 parts.
was cast into a mold. The ingot thus produced was immediately ground into scale-like chips with a thickness of one foot using a rolling mill. Usually, a silver alloy containing 1% by weight or more of bismuth has almost no workability, so when an ingot with a thickness of 15 mm is rolled, it naturally cracks and is crushed into scaly chips. This is in the air of 75,000, 6
Bismuth and tin were selectively oxidized by heating the bait for a certain period of time. Next, this was rolled again using a rolling mill to form chips with a thickness of 0.2 ribs. At this time, the oxide particles dispersed in the silver matrix are pulverized into fine particles by the oxidation treatment, which has a great effect on imparting machinability when the final wire is made.
The chips with a thickness of 0.2 ribs were cleaned, then loaded into a cylindrical mold with a diameter of 20 mm and molded at a pressure of 8 tons per body. This molded body was then heated and bonded in air at a temperature of 900° C. for 2 hours. Further, this Akatsuki compact was loaded into a warm heating mold having a diameter of 20.5 willow, and after applying a pressure of 8 tons/ground at 400 qo for 1 minute, it was sintered again in air at 900 qo for 4 hours. This bran compact was then extruded at a temperature of 550° C. and processed into a wire rod with a diameter of 3 mm. Finally, 830qo
After being hammered for 1 hour, it was processed into a contact stud having a spherical head with a diameter of 5 ribs and a curvature radius of 7 sides, and was used as a sample for a contact opening/closing test. The contact characteristics were evaluated by tests conducted using the circuit shown in the figure.

That is, an ASTM type tester was used as the switch 4, and the opening/closing conditions were set at a contact force of 30 mm, a separation force of 40 mm, and an opening/closing speed of 10 mm/sec, and the test load was a commercial power supply voltage of 100 mm.
V, 60Hz, protective resistor r=0.50, load R: 20
0, Capacity C=1140AF (350W for charging/discharging.V3
Three 80F capacitors are connected in parallel. ). Therefore, the rush current has a peak of 28 and a steady state. The evaluation of the contact characteristics was based on the number of welds during 2×1 turns under the above conditions, that is, the number of times a force exceeding 40 degrees was required to open the contacts, and the wear and tear of the contacts after 2×1 turns. This was determined based on the amount of consumption, especially the amount of consumption on the positive electrode side. The number of test samples was 6 pairs each, and the minimum and maximum values of each characteristic are shown in the table below. For reference, test results for silver-cadmium oxide (by internal oxidation method) are also shown as a comparative sample. As is clear from the results in the table below, the contact material according to the present invention exhibits extremely superior values in both welding and wear characteristics compared to conventional cadmium oxide contacts.

[Brief explanation of drawings]

The figure is for explaining an example of a typical convenient form of the electrical contact material according to the present invention.

Claims (1)

[Claims] 1. The oxides dispersed in the silver matrix are bismuth tin oxide (Bi_2Sn_2O_7) and tin oxide (Sn
O_2), characterized in that its metal alloy components are 3 to 6% by weight of bismuth, 6 to 10% by weight of tin (excluding 6% by weight), and the balance is silver. Electrical contact materials. 2 The oxides dispersed in the silver matrix are bismuth tin oxide (Bi_2Sn_2O_7) and tin oxide (Sn
O_2) and nickel oxide (NiO) or cobalt oxide (CoO), the metal alloy components of which are 3-6% by weight of bismuth and 6-10% by weight of tin (in terms of metal). However, excluding 6% by weight), 0.1 to 0.5% by weight of one of nickel or cobalt,
An electrical contact material characterized in that the balance is silver.