Silver-oxide based electric contact material

Abstract

 A silver-oxide based material for electric contacts, which has excellent deposition resistance and consumption resistance. The material is formed by subjecting to an internal oxidation treatment an Ag based alloy consisting essentially of:

Sn:

4 - 11%;

In:

1 - 5%;

Te:

0.05 - 4%; and

Ag and inevitable impurities:

the balance.

If required, at least one of the following elements may be added:

(a) at least one element selected from the group consisting of Fe, Ni, and Co: 0.01 - 1%; and

(b) Cd: 0.05 - 3%.

Description

BACKGROUND OF THE INVENTION

(Field of the Invention)

[0001] This invention relates to silver-oxide based materials for electric contacts for use in various electrical or electronic apparatus.

(Prior Art)

[0002] Conventionally, a great many electrical contact materials have been proposed or used in various electrical or electronic apparatus. Among widely used electric contact materials, there is known, e.g. from Japanese Patent Publication (Kokoku) No. 55-4825 an electric contact material which is formed by subjecting an Ag based alloy consisting essentially of, in weight % (hereinafter the percentage is weight %), 5 - 10% Sn, and 1 - 6% In, and, if required, 0.01 - 0.5% at least one element selected from the group consisting of Fe, Ni, and Co, and the balance of Ag and inevitable impurities, to an internal oxidation treatment in which the Ag based alloy is soaked in an oxidizing atmosphere at a temperature of 650 to 750°C for a predetermined time period.

[0003] In recent years, there has been made a remarkable progress in the development of electrical and electronic apparatus having improved performance and prolonged service lives. Accordingly, there is an increasing demand for materials for electric contacts for use in these electrical and electronic apparatus, which have improved deposition resistance and consumption resistance. However, in actuality, conventional electric contact materials inclusive of the above-mentioned known electric contact material do not have sufficient deposition resistance and consumption resistance to satisfy requirements imposed by recently developed electrical and electronic apparatus.

SUMMARY OF THE INVENTION

[0004] It is, therefore, the object of the invention to provide silver-oxide based materials for electric contacts, which have excellent deposition resistance and consumption resistance and hence prolonged service lives.

[0005] To attain the above object, the present invention provides a silver-oxide based material for electric contacts, having excellent deposition resistance and consumption resistance, the material being formed by subjecting to an internal oxidation treatment an Ag based alloy consisting essentially of:

Sn:

4 - 11%;

In:

1 - 5%;

Te:

0.05 - 4%; and

Ag and inevitable impurities:

the balance.

[0006] If required, at least one of the following elements (a) and (b) may be added:

(a) at least one element selected from the group consisting of Fe, Ni, and Co: 0.01 - 1%; and

(b) Cd: 0.05 - 3%.

[0007] The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description.

DETAILED DESCRIPTION

[0008] Under the above stated circumstances, the present inventors have made many studies in order to obtain silver oxide based electric contact materials having improved deposition resistance and consumption resistance, and reached the following finding:

[0009] A silver-oxide based material for electric contacts, which is formed by subjecting an Ag based alloy consisting essentially of:

Sn:

4 - 11%;

In:

1 - 5%;

Te:

0.05 - 4%;

and, if required, at least one of the following elements (a) and (b):

(a) at least one element selected from the group consisting of Fe, Ni, and Co: 0.01 - 1%; and

(b) Cd: 0.05 - 3%; and
   Ag and inevitable impurities: the balance, to an internal oxidation treatment under the above-mentioned conditions, i.e.:

Atmosphere:

Oxidizing atmosphere;

Oxidizing Temperature:

650 - 750°C; and

Soaking Time:

8 - 26hr,

has by far more excellent deposition resistance and consumption resistance as compared with the aforementioned known silver-oxide based electric contact material.

[0010] The present invention is based upon the above finding, and the silver-oxide based electric contact material according to the invention has the aforementioned chemical compositions.

[0011] The reasons for specifying as above the contents of the component elements of the Ag based alloy before being subjected to the internal oxidation treatment will now be described:

(a) Sn:
   The Sn forms oxides in the alloy, which act to enhance the deposition resistance. However, if the Sn content is less than 4%, the deposition content cannot be enhanced to a desired extent, whereas if the Sn content exceeds 11%, the resulting electric contacts will have excessive contact resistance, and further the silver-oxide based material will have degraded workability in manufacturing electric contacts therefrom. Therefore, the Sn content should be limited to a range of 4 to 11%. A preferable Sn content range is 5 to 8%.

(b) In:
   The In acts to promote oxidation of the Sn component, and also the In itself forms oxides which act to enchance the deposition resistance and consumption resistance. However, if the In content is less than 1%, the above actions cannot be performed to a satisfactory extent, whereas if the In content exceeds 5%, the resulting electric contact material will even have degraded deposition resistance. Therefore, the In content should be limited to a range of 1 to 5%, and preferably 1.5 to 3%.

(c) Te:
   The Te forms oxides which can easily sublime upon generation of an arc due to closure or opening of the electric contacts to thereby further enchance the deposition resistance and consumption resistance. However, if the Te content is less than 0.05%, the above action cannot be performed to a desired extent, while if the Te content is in excess of 4%, it will result in degraded workability. Therefore, the Te content should be limited to a range of 0.05 to 4%, and preferably 0.1 to 1%.

(d) Fe, Ni, and Co:
   One or more of these elements may be added according to necessity. If added, they dissolve in the matrix to finely divide the oxides and the Ag grains to thereby improve the deposition resistance. However, if the total content of these elements is below 0.01%, the above action cannot be performed to a satisfactory degree, whereas if the total content exceeds 1%, degraded workability will result. Therefore the total content of Fe, Ni, and Co should be limited a range of 0.01 to 1%, and preferably 0.05 to 0.2%.

(e) Cd:
   Cd may be added if required, since the Cd cooperates with the Te to further enhance the deposition resistance. If the Cd content is less than 0.05%, desired improvement in the deposition resistance cannot be obtained, whereas in excess of 3%, the consumption resistance will even degrade. Thus, the Cd content should be limited to a range of 0.05 to 3%, and preferably 0.1 to 2%.
Next, examples of silver-oxide based electric contact materials according to the invention will be described.

Example 1

[0012] Ag based alloys having chemical compositions shown in Tables 1 and 2 were smelted in an ordinary type high-frequency smelting furnance and cast under conventional ordinary casting conditions into ingots. The ingots were each hot extruded into a plate having a thickness of 5mm. The plate was then hot rolled, followed by being cold rolled into a sheet having a thickness of 0.6mm. The sheet was cut or sliced in its longitudinal direction into a strip having a width of 2mm. The strip was subjected to an internal oxidation treatment under an oxygen atmosphere at a temperature of 700°C and for a soaking time of 24 hours. The internally oxidized strips were put together and compacted into a billet having a diameter of 70mm. The billet was extruded into a diameter of 7mm, followed by being subjected to wire drawing into a wire having a diameter of 2mm. Finally, the wire was formed, by a header machine, into rivets having a head diameter of 4mm, a head height of 1mm, a leg diameter of 2mm, and a leg length of 2mm. The obtained rivets were adapted as specimens of the silver-oxide based electric contact material according to the present invention (hereinafter referred to as "the present invention contact materials Nos. 1 - 11") and specimens of conventional silver-oxide based electric contact materials (hereinafter referred to as "the conventional contact materials Nos. 1 - 11").

[0013] Then, electrical tests were conducted on the present invention contact materials Nos. 1 - 13 and the conventional contact materials Nos. 1 - 13 by the use of an electric contact testing machine according to ASTM under the following conditions to examine the number of times of deposition and the amount of consumption in order to evaluate the deposition resistance and the consumption resistance:

DC Voltage

: 14V;

Making Current

: 150A;

Breaking Current

: 30A;

Switching Time

: ON for 1 sec. - OFF for 9 Sec.;

Contact Force

: 80g;

Opening Force

: 80g;

Number of Times of Switchings

: 10,000

[0014] The results of the tests are shown in Tables 1 and 2.

Example 2

[0015] Rivets were formed from Ag based alloys having chemical compositions shown in Tables 3 and 4 under the same conditions as in Example 1 described above, to obtain present invention materials Nos. 14 - 29 and conventional materials Nos. 12 - 17.

[0016] Then, electrical tests were conducted on the present invention contact materials Nos. 14 - 29 and the conventional contact materials Nos. 12 - 17 by the use of an electric contact testing machine according to ASTM under the following conditions to examine the number of times of deposition and the amount of consumption in order to evaluate the deposition resistance and the consumption resistance:
DC Voltage  : 24V;
Making Current  : 100A;
Breaking Current  : 20A;
Switching Time  : ON for 1 sec. - OFF for 9 Sec.;
Contact Force  : 100g;
Opening Force :  100g;

Number of Times of Switchings :

5,000

[0017] The results of the tests are shown in Tables 3 and 4.

[0018] It will be learned from Tables 1 to 4 that the present invention contact materials Nos. 1 - 29 all show by far more excellent deposition resistance and consumption resistance than the conventional contact materials Nos. 1 - 17.

[0019] Since silver-oxide based electric contact materials according to the present invention thus possess excellent deposition resistance and consumption resistance, if they are actually used in various electrical or electronic apparatus, they will greatly contribute to improving the performance of the electrical or electronic apparatus as well as to prolongation of the service lives thereof.

Claims

1. A silver-oxide based material for electric contacts, having excellent deposition resistance and consumption resistance, said material being formed by subjecting to an internal oxidation treatment an Ag based alloy consisting essentially of:

Sn:   4 - 11%;

In:   1 - 5%;

Te:   0.05 - 4%; and

Ag and inevitable impurities:   the balance.

2. A silver-oxide based material for electric contacts, having excellent deposition resistance and consumption resistance, said material being formed by subjecting to an internal oxidation treatment an Ag based alloy consisting essentially of:

Sn:   4 - 11%;

In:   1 - 5%;

Te:   0.05 - 4%; and
   at least one element selected from the group consisting of Fe, Ni, and Co: 0.01 - 1%; and

Ag and inevitable impurities:   the balance.

3. A silver-oxide based material for electric contacts, having excellent deposition resistance and consumption resistance, said material being formed by subjecting to an internal oxidation treatment an Ag based alloy consisting essentially of:

Sn:   4 - 11%;

In:   1 - 5%;

Te:   0.05 - 4%;

Cd:   0.05 - 3%; and

Ag and inevitable impurities:   the balance.

4. A silver-oxide based material for electric contacts, having excellent deposition resistance and consumption resistance, said material being formed by subjecting to an internal oxidation treatment an Ag based alloy consisting essentially of:

Sn:   4 - 11%;

In:   1 - 5%;

Te:   0.05 - 4%;

Cd:   0.05 - 3%;
   at least one element selected from the group consisting of Fe, Ni, and Co: 0.01 - 1%; and

Ag and inevitable impurities:   the balance.

5. A silver-oxide based material for electric contacts, as claimed in any of claims 1 - 4, wherein said internal oxidation treatment is carried out under the following conditions:

Atmosphere   : Oxidizing atmosphere:

Oxidizing Temperature   : 650 - 750°C; and

Soaking Time   : 8 - 26hr

6. A silver-oxide based material for electric contacts, as claimed in any of claims 1 - 4, wherein Sn is contained in said Ag based alloy in an amount of 5 - 8%.

7. A silver-oxide based material for electric contacts, as claimed in any of claims 1 - 4, wherein In is contained in said Ag based alloy in an amount of 1.5 - 3%.

8. A silver-oxide based material for electric contacts, as claimed in any of claims 1 - 4, wherein Cd is contained in said Ag based alloy in an amount of 0.1 - 2%.

9. A silver-oxide based material for electric contacts, as claimed in any of claims 1 - 4, wherein at least one element selected from the group consisting of Fe, Ni and Co is contained in said Ag alloy in an amount of 0.05 - 0.2%.