JPH03183736A - Silver-oxide electrical 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] [Industrial Application Field] The present invention is directed to silver oxides used today in AC and DC circuits, current circuit breakers, large-capacity switches, etc. used in the atmosphere. The present invention relates to system electrical contact materials.

Such contact materials are broadly classified into Ag-w and Ag-wc-based sintered alloys, Ag-snO2, Ag-cdo, and Ag-ZnO-based sintered alloys, and similar internal oxidation alloys. .

Among these, silver-oxide alloys are those made by mixing and sintering Ag powder and oxide powder, and those made by oxidative roasting, that is, internal oxidation, of molten silver alloys or sintered alloys. There is.

The present invention relates to a novel silver-oxide electrical contact material which has excellent welding resistance and arc resistance using the latter internal oxidation method.

[Prior Art] The silver-oxide contact materials produced by the internal oxidation method used today have stable quality due to the manufacturing process and are used in a wide range of applications. On the other hand, it is limited by alloying conditions, the possibility of internal oxidation, etc., and its welding resistance and abrasion resistance due to electric arc heat are lower than Ag-w and Ag-wc based sintered materials. This is considered a drawback.

The same drawbacks occur with respect to the Ag-snxInyOz and Ag-cdo-snO2 systems. Therefore, an evaluation that satisfies the current interrupting ability has not been obtained.

[Problem to be solved by the invention] Ag-snO produced by the internal oxidation method used today
In the second type material, sn is added to the limit of the solid solution state of Ag, and either In or Bi is added as an internal oxidation promoter, and since both oxides have low melting points, Ag-SnxInyOz, A
The melting point of the alloy oxide contained in these electrical contact materials expressed by the symbol g-SnxIn□Oz is lower, and the heat resistance of the dispersion strengthened material is inevitably inferior. Specifically, it is said that this is because in response to high heat, a low-grade congruent oxide film of silver and solute metal is formed and adhered to the contact surface, making it easier to weld.

In the present invention, Mg, which is a highly heat-resistant oxide, is used as a Ag-sn- When added to Bi-based silver alloys, it enables the creation of internally oxidized alloys and even greater current interruption in that material.

[Means for Solving the Problems] The Mg element described in the present invention has a solid solubility in Ag of about 8% by weight, but has a light specific gravity, and is suitable for Ag, Sn, Cd, Bi,
While the atomic weight of In etc. is 107 to 209,
Mg is 243. Therefore, when compared in weight percent, equal weights of Sn and Bi are dissolved in Ag, and Mgo is 4 to 5 times larger than the oxide precipitated after internal oxidation, and a large volume is dissolved in silver. Although the volume expansion is large due to precipitation and dispersion, Mgo has a melting point of over 2800℃, is thermally stable, and is not corroded by other oxides or Ag-alloys and melts. Since it does not show any reaction to silver, its welding resistance increases.

For the above reasons, the ternary alloy of Ag and Mg-sn-Bi is blended under conditions that allow internal oxidation. The effect appears 0
．． A silver alloy containing 6 w/o Mg made by melting and sintering is oxidized and roasted at an appropriate temperature with high pressure oxygen to produce an alloy in which ultrafine particles are uniformly precipitated and dispersed in a silver matrix. vinegar. M
g, Sn, Bi, the content is the weight in the silver solid solution range,
The specific gravity of Mg is 1.7gr/cc and that of CD is 8.6gr/c.
Since it is lower than c, the amount of molten metal is set at 30 at%.

Therefore, the upper limit of Mg is 5w%, Sn. Naturally, Bi is within the solid solubility limit for Ag, and Bi is within the solid solubility limit for Mg. Since Sn has a solid solubility limit of 8 to 14% by weight for both elements, oxidation can be promoted and a good structure can be obtained by adding a very small amount, as in the case of Ag-Sn alloys. However, it is important for the solute alloy to be a unified solidification component in order to maintain the same function in terms of internal oxidation structure and electrical performance. Therefore, the problem to be solved by the present invention is to internally oxidize a silver alloy to which a ternary eutectic alloy of Mg-Sn-Bi is added in increasing or decreasing amounts depending on the purpose. The stable heat-resistant contact surface with dispersed MgO is suitable for large current arcs.
Even if exposed, there is no surface welding and the Mgo particles
As another effect, Mg. Sn. B
The bonding strength of the composite oxide (i) is large, and a large amount of strain and stress is transferred into the silver matrix to form a hard alloy, which is impossible with a method of mixing and sintering using powder metallurgy. A high-density composite material is obtained. This results in a silver composite having a structure that can withstand high temperatures above the melting point of silver. The effects of blending the alloys will be shown by way of examples. The upper limits of Mg, Sn, and Bi are determined by the eutectic and solid solubility limits, and the minimum value is the lowest value that meets the purpose of use.

For example, Bi is a Sn-Mg2Sn eutectic alloy with Mg of 0.
This is the minimum amount required for internal oxidation of a silver alloy containing 6 wt% Sn and 0.4 wt%. Bi-Sn eutectic alloy is the required weight for internal oxidation of about 10% of Mg, and the upper limit is 30 atomic weight % of ternary eutectic alloy containing intermetallic compounds in silver.
The amounts of Mg, Sn, and Bi are set to contain.

Each shank metal element added in claim 2 can also be used in a low current region, when required, to take advantage of the effect of an oxide with a low melting point or high vapor pressure to stabilize the surface resistance. Yes, but it is rare that it is dedicated to large capacity. For these reasons, it is a well-selected element that dissolves in solid solution, does not inhibit internal oxidation, and has good effects.

[Function] The gist of the function of the present invention is that it is a silver-solid solution alloy that can be internally oxidized. Molding from alloy. The alloy powder is internally oxidized after shaping and sintering.

Alternatively, the products of the present invention can be manufactured for the first time by utilizing methods and processes with favorable conditions regarding current metallurgical manufacturing technology, such as individually or continuously rust forming into a desired shape and internal oxidation. is possible. However, there is no other way to obtain a silver-oxide contact material, which has not been available in the past. ■
However, in the case of silver alloys with a weight ratio of 5% or less, it is often possible to form them by hot working or the like. Even in such a case, the heat-resistant fine particles of MgO may cause the black part on the surface of the contact to
The lower oxidation layer containing 2O and the white silver color portion exist independently in both the low melting point silver alloy layers, and clearly exhibit an effect without impairing the welding resistance and flow deformation resistance.

Moreover, the metal additive element shown in claim 2 is a relatively low melting point oxide and has a high vapor pressure, and when used with a low current load, it has a cleaning effect due to evaporation of the oxide on the contact surface. It can have performance that meets the application of electrical contact materials for both large and small capacity. As described above, if the wear amount and the instability of welding resistance can be compensated for in the design of the equipment, the material has melting resistance that conventional products do not have even in the event of a large-capacity short circuit. Taking advantage of its characteristics, it is compatible with other oxide-based silver contact materials,
Even when used in combination, the effectiveness is highly evaluated.

By the way, the volatile solution of cdo is around 725℃, and Mg
It is much lower than the melting point of Ag, which is 2800°C.

Example prototype materials (Components fused to Ag and weight NO. Mgwt% Snwt% Biwt% Other wt% 1 4.0 0.3 0.2 - 2 1.0 0.8 0.8 - 3 2.0 1 .5 1.5 - 4 3.0 2.5 2.5 - 5 3.0 2.5 0.25 - 6 2.0 1.5 1.5 Zn0.57 1.5
1.5 1.5 cd3.08 1.5 1.5 1.
5 In1.59 - 8.0 - In3.5 10 - 1.5 - cd14 The above metal component values are weight % contained in silver, and NO9 and 10 of the 10 samples are actually used in the past. This is a typical material that has been used. No. Nos. 1 to 8 are DISC contacts of 4.5 m/mφ×1.0 m/mt made by a casting method.

No. 9, 10, 0.1m/0.1m/
4. Press punched from a composite material having mt of silver ■.
Identical contact samples of 5 m/mφ×1.0 m/m were obtained.

The casting method is a suitable method because it requires less plastic processing and is more stable in terms of component values than the powder sintering method. 4.5 which is melted and has a spherical surface of 30m/mR in the part ■ on the carbon plate.
A mold plate with a number of holes of m/mφ and 1 m/m depth was made into a mold plate, and was pressurized and rapidly solidified using an iron plate cooling mold to obtain the shape of each sample.

All samples were heated at a temperature of 680°C and in 20ATM of oxygen at approximately 5%
It was held for 0 hours to complete internal oxidation.

Traditionally, Ag-Sn, Ag-Sn-Mg alloys, Mg
Silver alloys in which the sum of Sn and Sn exceeds 5% by weight cannot be internally oxidized, and this time as well, NO-1 is Sn-B compared to Mg.
The i-eutectic alloy was added within the Ag-Mg solid solution state. N
The samples O2, 3, and 4 are silver alloys in which a ternary eutectic alloy of Mg-Sn-Bi is added to Ag at varying concentrations. NO-5 is A
Mg-Sn eutectic in g and Bi in solid solution form of both
Silver alloy with added amount. NO-6, 7, 8 are NO. Zn, CD, and In are further added to No. 3 for the purpose of stabilizing the contact under low loads.

By adding Bi appropriately, an internal oxidation structure similar to that of Ag, Sn, and Bi alloys was obtained. However, since the structure is such that the scattered precipitated oxide particles are ultrafine, nearly spherical crystals, all solute components form precipitated particles with a uniform oxide concentration. This fact is the most important physical property in terms of contact performance.

Based on the examples, the physical properties and electrical test results of each sample are shown in a table. As a supplement, sample No. of the present invention. Nos. 1 to 8 were brazed to the test base metal using an alloy of 15 wt % Ag-In and 10 wt % Sn because there was no silver coating on the back surface of the contacts. No. 9 and 10 were general silver brazed.

(1) Special characteristics table-1 Hardness and conductivity after internal oxidation (2) Electrical test Table 2 Test conditions ASTM test consumption Voltage 2100 AC current 50A, opening/closing 60 times/min Contact shape 4. 5m/nφ×1.0m/nt, opening and closing 30,000 times,
Load reactor Pf=0.28, contact pressure 400gr,
Breaking pressure: 600 gr (b) Welding test Contact pressure: 400 gr Peak current value of rechargeable capacitor discharge (A) A tearing force of 800 gr or more added to the contact pressure was defined as the welding limit.

〔Effect of the invention〕

As described in the examples, we cannot find any particularly excellent switching results for medium currents, but NO-5, which has a small amount of Bi added to the eutectic component of Mg-Sn, and Mg-Sn-Bi triple All the samples in which the original eutectic component was added to silver received excellent evaluations for arc resistance and welding resistance, and when used in opposition to other oxide-based contact materials, the advantages of both can be utilized. The matter was confirmed.

Claims (2)

[Claims] (1) Sn and B of 0.1 to 3% by weight each as metal components
A silver-oxide electrical contact material, which is obtained by internally oxidizing a silver alloy containing two elements of i and 0.6 to 5% by weight of Mg as a solid solution. (2) The silver-oxide electrical contact material according to claim 1, wherein the silver alloy further contains 0.1 to 6% by weight of one or more of Cd, In, and Zn.