JPH03183735A - Silver-oxide contact material - Google Patents

Abstract

PURPOSE:To improve the deposition resistance of the contact material by incorporating specified amounts of Sn, Ca and Bi into an Ag matrix and subjecting the alloy to internal oxidation. CONSTITUTION:The electrical contact material is formed of silver-oxides obtd. by subjecting an Ag alloy contg., by weight, 2 to 12% Sn, 0.5 to 5.0% Ca and 0.1 to 1.4% Bi to internal oxidation. By this compsn., a good alloy having dispersed structure can be obtd. Or, an Ag alloy including a ternary eutectic alloy constituted of each 0.6 to 5% Sn, Ca and Bi is subjected to internal oxidation. Alloy oxides having high diffusing rate at the time of subjecting the ternary alloy to internal oxidation and having a low concn. segregating degree from the surface part to the central part are precipitated. By the effect of adding Ca, excellent arc resistance and capacity advantageous to the application for DC power relays and current breakers can be obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to switching equipment for direct current and alternating current, which is used in the air.
It relates to electrical contact materials used in current breakers and the like. Traditional silver monoxide based materials are made by sintering methods and internal oxidation.

The present invention is a silver-oxide electrical contact material produced by the latter method, which is used in a wide range of applications from light loads to large capacity loads, and which has improved anti-welding properties.

[Prior art] Similar materials used today are Ag-Cdo, A
g-Zno, Ag-SnO2 system, especially Ag-
In the S4O2 system, internal oxidation does not proceed when the weight percent of Sn is less than 5. Therefore, there are materials that include a technique to achieve successful internal oxidation by adding In and Bi elements.

These are the melting point of SnO2, 1625℃, and the melting point and high temperature, in order to form a common oxide with the additive element.
There are many places where the contact characteristics deteriorate. Furthermore, in practical applications, especially as contacts for DC enclosures, there is a tendency for problems such as transfer, generation of projectiles, welding, and wear and welding when interrupting large currents to occur.

On the other hand, improvement research on sintered materials of Ag+SnO2 (8 to 12□) has been carried out in various overseas research and development projects, and although there is some information that progress has been made gradually, Perhaps because of this, sufficient density and cohesive force could not be obtained,
The current situation is that repeated overload tests and large current interruption tests are not satisfactory [Problems to be solved by the invention] As mentioned above, the Ag-SnxBiyOz-based material produced by the internal oxidation method has poor quality in practical terms. It is highly rated for its stability. In order to have general heat resistance, Ca, which can be alloyed with both Ag and Sn, is added to a material with a light specific gravity within the allowable range for curing, and has a melting point of approximately 2000°C, such as CaJnO3.
By finely precipitating and dispersing oxide particles that reach 100%, overcoming the physical recessiveness of Bi, which promotes internal oxidation, and precipitating and dispersing heat-resistant particles superior to SnO2 in a silver matrix, The target is direct current, alternating current, and conventionally considered special use. The aim is to develop heat-resistant contact materials. Ca
The specific gravity of silver is light, 1.54 g/cc, and although it is a small amount in terms of weight ratio, it occupies a large volume in silver, and compared to those of Sn and Ca, the weight to volume ratio is about 5. It's double. From a metal phase diagram observation, the solidification point of an Ag alloy containing 5.6% by weight of Ca decreases to 653°C. After being cooled from the melting point of Ag (960° C.) until it reaches 653° C., a liquid phase and a mixed solid phase of CaAg4 or a compound thereof coexist. This has a significant relationship with the internal oxidation temperature. Furthermore, in the X-ray analysis of the coagulation phase, Ag and various compounds are mixedly present.

Such an alloy produces many atomic gaps during the cooling and heating processes, which inhibits plasticity, but also has the advantage that the oxygen diffusion rate increases during internal oxidation. Therefore, internal oxidation of the silver alloy can be successfully achieved to a certain extent by heating under high pressure oxygen (10 to 50 ATM) and at low temperature (near 650° C.) without adding Bi as an oxidation promoter.

The silver monoxide contact material can ensure stable performance due to the dispersion of heat-resistant oxide particles such as CaSnO3.

C
As an aXSnYOZ+Ag alloy, the melting point is at least higher than that of SnO2, the dispersed particles are fine, the diffusion range is narrow, and the dispersion is uniform.

As mentioned above, in the Ag-SnO2-BiXO3 system, 220 Volt and 2000 Amp are cut off in the AC circuit. Since the DC circuit is limited to switching at 24 Volts and 20 Amps, the goal of the development is to add CaO, which has alloying properties, to Ag, Sn, and Bi to create an internally oxidized material with even greater durability.

[Means for Solving the Problems] As already described in the previous paragraph, in order to add Ca to the Ag-Sn alloy and establish an internal oxidation progression mechanism, three items are specifically described as claimed in the patent. By describing the content in detail, the means and methods will be clarified.

(1) Sn in Content Explanation Ag regarding Paragraph 1 of Patent Claim
The minimum weight of Sn is at least 2% by weight, which is necessary for acid solubility, and the maximum is A.
The solid solubility limit in g is 12% by weight, and Ca is 0.5% by weight.
In the above, CaSn
3 (89.9% dSn), and the maximum value was at the eutectic point of Ag-Ca, 5.2% by weight.

Bi has the maximum solid solubility limit with respect to Sn. The minimum value is S
This value is necessary to increase the internal oxidation rate of the Ag-Sn alloy where the minimum value of n is 2% by weight. The intermetallic compound formed between Sn and Ca is Ca2Sn (60■%Sn).
, CaSn (74.7% Sn), CaSn3 (89.
Three types are known: 8■%Sn).

The most stable bond is CaSn, whose oxide properties are also known. The melting point of CaSnO3 is approximately 2000℃
So, it is located between CaO (2600℃) and SnO2 (1600℃), and the higher the Ca component ratio, the closer the melting point is to that of CaO, and the melting point of CaSnO3 is almost the same as the boiling points of SnO2 and Ag. There is. In the first term, 14% by weight or less of Bi is added to the Sn of the Ag-CaSn alloy, and
As the internal oxidation progresses, the i element moves from the Ag-Sn solid solution phase to the defective part where Bi is broken during solidification, and as the SnBi eutectic alloy progresses, it becomes a diffusion nucleus rather than Sn, increasing the concentration diffusion rate, resulting in good dispersion. A textured alloy is obtained.

(2) Explanation of content of item 2 of the patent claim By adjusting the composition ratio of the ternary eutectic alloy of Sn, Bi, and Ca to be alloyed with Ag, the solidification point of the Ag-alloy is lowered, and the composition The ratio is constant, the diffusion rate during internal oxidation of the three elements is fast, and the alloy oxide with the lowest concentration and precipitation is precipitated from the surface to the center. The alloy concentration of the three elements, which takes advantage of the above advantages, is near the cubic ratio at the eutectic point. Bi-C
The eutectic point of a is 41.5% by weight of Bi and the melting point is 786°C.
, the eutectic point of Sn-Bi is 57% by weight of Bi and the melting point is 13
5℃, Sn-Ca eutectic point, 40 between Ca-Ca2Sn
．． 6% by weight of Sn(E1). The eutectic point of CaSn-CaSn3 is Sn86% by weight and (E2) exists, but the E1 eutectic point is advantageous when the amount of the ternary alloy is small. The amount of Sn is increased slightly from the average distribution ratio, and the component ratio is divided into three parts. Bi, which is 5.0% by weight, which is close to the solid solubility limit in Ag, increases brittleness and has a large amount of wear and tear, resulting in a material with little adhesiveness. becomes. Suitable for applications that take advantage of its welding resistance properties.

(3) Explanation of content of claim 3 Regarding the Sn-Ca alloy with eutectic points E1 and E2 described in the previous paragraph, as an Ag-Ca eutectic alloy, the melting temperature decreases to 800°C when the Ca amount is 3% by volume. , and the composition of the Ag-Sn-Ca alloy, in which Sn does not exceed 5% by weight and internally oxidizable Sn is blended with 4.5% by weight or less, falls within this range.
1. Due to the eutectic point of Sn-Ca in E2 or the forging effect of a silver alloy containing an appropriate amount of CaSn compound, gaps that become internal oxidation nuclei are formed in the alloy, and the oxygen pressure is increased to about 40 ATM to recrystallize. In order to reduce crystal growth, the oxidation temperature is set well below the freezing point. Alternatively, it is advantageous to sinter the molten alloy powder, reshape it, and then internally oxidize it. S
Although n is a small amount, the specific gravity of Ca is small, and the surface area of the oxide particles in silver becomes large. Furthermore, since it does not contain low-melting-point elements such as Bi, the brittleness and heat resistance of Ca are added to SnO2, and it has effective characteristics in opening and closing DC circuits, etc.

Furthermore, under internal oxidation conditions, the progress rate of Ag-Sn 4% is slower than that of the AG-Sn-Bi alloy even at important high oxygen pressures, and the precipitated particles are not clear. As mentioned in the present invention, C
The weight that can be hot-formed with a element is AG-Sn (4
□%), the experimental result is a limit of 0.4% by weight, so we finally achieved a good structure and contact properties while increasing the processing rate by covering the surface with silver or hot extrusion, etc. is obtained.

The above is an explanation of the contents of each patent claim.

[Effects of the invention] Within the range of ingredients that can be produced by the internal oxidation method of Ag-Sn alloys, the effect of Bi addition as in conventional Ag-Sn-Bi and alloys, as well as the negative effect on the contrary, can be eliminated. The purpose of the invention is to obtain the effect of ultrafine particles that are more stable than SnO2 by dispersing a heat-resistant alloy oxide (CaXSnYOZ) in the silver matrix as precipitated particles through Ca and Sn bonds that form a highly heat-resistant oxide. shall be. Of course. Regarding Ag-Sn (45%), it was also found that during internal oxidation, the rate was higher than that of the single alloy. Addition of Ca element, which has a high affinity for oxygen and has a light specific gravity, has the effect of promoting internal oxidation, making the precipitated particles finer, and improving the heat resistance effect. As a supplement, the low specific gravity of Ca is similar to Sn, Ca, etc. in silver. It is an electrical contact material that can be used for switching in large-capacity circuits, regardless of AC or DC, without increasing the weight content.

[Example] In Table-1. The components of the blended silver alloy and the measured values of physical adhesion after oxidation are shown.

(1) Silver alloy components and physical properties after oxidation in the sample. NO-1 to NO5 are alloys included in the scope of the present invention. Due to its low plasticity, it was melted in an argon atmosphere and cast onto a carbon mold plate having a hole in the form of 4.5 m/mφ x 1 m/m deep. Before solidification, it was pressed with a cooling mold and cooled and molded. NO-6 and NO-7 are 30m/mφ×100m/mL castings, 10m/m
Preheated to 750°C in the form of a tape of φ x 1 m/m
Extrude with a pressure of 200□. With that tape, 4.5
It was punched out into a disk shape of 1 m/mT in m/mφ. NO
-8 to 9 are current products, which are samples pressed to 4.5 m/mφ from a 1 m/mT plate lined with 0.1 m/MT Ag. NO-1 to NO-7, 40 at low temperature (670℃)
NO-8 to NO-9 were heated under ATM oxygen pressure for about 50 hours to complete internal oxidation at 720°C. 1
It is internally oxidized at 0ATM (O2).

The electrical conductivity is a value measured by a sigma tester, and the hardness is a value determined by a general Rockwell hardness meter F scale. In terms of structure, NO-1, NO-7, and NO-8 are good, and the others are normal. In addition, it was observed that samples NO-1 to NO-6 had a small oxide diluted layer in the center. Ag-
When Ca is added to the Sn alloy, the alloy brittleness increases and crystal defects occur in the Ag-Ca eutectic alloy, which is a mixture of Ag and compounds with various molecular structures, and is difficult to process and reheat. By. The crystal space created when the molecular structure changes,
It is assumed that the defect is a defect, etc., and during internal oxidation, the defect is thought to act as a diffusion route for oxygen and as a precipitated nucleus, and S
When the n content was 4% by weight, clear grain precipitation of the internal oxidation structure of the silver-alloy containing Ca was confirmed.

(2) Electrical Properties Among the samples shown in Table 1, NO-1 to NO-7 do not have an Ag lining, so a test base ( Copper), brazed, NO-8
For NO-9, a general brazing material was used.

Test conditions (a) Contact wear amount AC 220Vo by ASTM tester
lt Current 50Amp Power factor 0. Closing frequency: 60 times/minute Contact pressure: 400g Separation force: 600g Closing frequency: 30,000 times The test will be discontinued if welding or abnormal wear occurs in the middle.

(b) Welding test contact pressure 400g Welding is when a separation force of 1kg or more is required at the peak current value (A) for discharge of a rechargeable capacitor. For each subject, tests are conducted three times with the same current, increasing in steps of 500A.

ASTM result NO. 2 and NO. 6 is a smooth wear surface, and NO. 1, NO. No. 2 produced a small amount of arc during the welding test, and was observed to be advantageous as a contact in the circuit breaker.

[Effects of the Invention] As described in the Examples, the effect of adding Ca is excellent in arc resistance, and in common, less arcing occurs during separation. Therefore, a small amount of current generation is an advantageous performance for DC power relays and current circuit breakers.

It was also confirmed that this material is more effective than conventional silver-oxide contact materials for this purpose.

Claims (3)

[Claims] (1) Metal components: 2 to 12% by weight of Sn;
A silver-oxide electrical contact material obtained by internally oxidizing a silver alloy containing 5 to 5.0% by weight of Ca and 0.1 to 1.4% by weight of each element. (2) A silver-oxidized silver-oxide electrical contact material obtained by internally oxidizing a silver alloy containing a ternary eutectic alloy of Sn, Ca, and Bi, each of which has a metal component of 0.6 to 5% by weight. (3) Metal components: 1.0 to 4.5% by weight of Sn and 0.0% by weight.
A silver-oxide electrical contact material obtained by internally oxidizing a silver alloy containing 01 to 3.0% by weight of Ca.