JPH09194967A - Silver-oxide type sintered electrical contact material and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silver-oxide system sintered electrical contact material which is not only excellent in the stability or contact resistance, welding resistance and resistance to consumption but also has a high electric conductivity and a manufacturing method thereof. SOLUTION: The manufacturing method for the silver-oxide system sintered electrical contact material is excecuted by sintering, densification-processing and, next, high pressure-internally oxidizing the raw material powder contng. silver, and then heat treating an obtained internally oxidized body in an atmosphere of a oxygen partial pressure lower than that of high pressure-internally oxidation or in an atmosphere substantially not contng. oxygen, and at a temperature above that of high pressure-internally oxidation and at 400 to 960 deg.C in a method of molding., sintering and then high pressure-internally oxidizing raw material powder contng. silver. Further, the silver-oxide system sintered electrical control material has an electric conductivity of >=60% (IACS).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a silver-oxide-based sintered electrical contact material and a method for producing the same.

[0002]

2. Description of the Related Art Silver-oxide type electrical contact materials are relays,
Used in small to large currents in conductor safety breakers, circuit breakers, air circuit breakers, etc. Conventionally, Ag-C has been used as a silver-oxide electrical contact material.
dO-based materials are known. This material is manufactured by a method of internally oxidizing Cd in an Ag-Cd alloy which is a melting / casting material under a low oxygen partial pressure with an oxygen partial pressure of about atmospheric pressure to about 30 atmospheric pressure. And the properties required for electrical contact materials,
It has a relatively well-balanced low contact resistance, high welding resistance and high wear resistance.

However, Ag-CdO type electrical contact materials are
Since it contains Cd which is harmful to the human body, Cd should not be used as much as possible.
Silver produced by a method in which elements such as n, Zn, In, and Mn are added, and these additional elements are internally oxidized under a low oxygen partial pressure.
Oxide-based electrical contact materials have been developed. However, the above-mentioned silver-oxide type electrical contact material has not been able to sufficiently meet the performance improvement required as an electrical contact material. That is, there were the following drawbacks.

(1) As the inside of the material becomes coarser, the oxide becomes coarser and the dispersion state of the oxide particles becomes non-uniform, so that stable contact performance cannot be obtained. (2) Since a thin layer of oxide occurs in the center of the material,
Short life as an electrical contact. (3) To improve the wear resistance and welding resistance of the material,
It is conceivable to increase the concentration of the additive element in the molten / cast material. However, the upper limit of the concentration of the additive element is limited to the range where it can be solid-solubilized in silver, and even if it is within the range where it can be solid-solubilized, a considerable amount of time is required for the internal oxidation step, and sometimes the material is A dense layer of oxide may be formed on the surface and internal oxidation may not proceed.

The reason for (1) above is considered as follows. That is, the particle size of the oxide is determined by the competition between the nucleation rate as the internal oxidation tip passes through and the particle growth rate and coarsening rate following nucleation. For this reason,
In internal oxidation under a low oxygen partial pressure, as the internal oxidation proceeds from the surface of the material to the inside, the diffusion rate of oxygen decreases and the oxide particles become coarse. In an electrical contact material in which the oxide dispersion state is non-uniform in this way, the dispersion state of the oxide in the contact area changes as the wear caused by the arc that occurs when the contact opens and closes, leading to the segregation of silver components. Affects properties such as welding resistance.

The reasons for the above (2) and (3) are as follows.
It is considered as follows. That is, the formation of a dilute layer of oxide in the central part of the material and the formation of a dense layer of oxide on the surface of the material are both due to the fact that the additive element diffused toward the surface because the diffusion rate of oxygen decreased. . The above-mentioned drawbacks caused by the internal oxidation of the additive element in the molten / casting material under the low oxygen partial pressure of oxygen atmospheric pressure to about 30 atmospheric pressure is a high oxygen partial pressure of several hundred atmospheric pressure. This can be solved by adopting the method of internal oxidation under partial pressure.

The reason for this is considered as follows. That is, it is possible to extremely suppress the decrease in the diffusion rate of oxygen by the internal oxidation under the high oxygen partial pressure, and to finely disperse the oxide particles which are easily coarsened by the internal oxidation under the low oxygen partial pressure. Further, since the additive element is difficult to diffuse toward the surface, a thin layer of oxide is not formed in the central portion of the material, and a dense layer of oxide is not formed on the surface of the material even if the material has a high element concentration.

However, this method has the following drawbacks and remains. That is, (1) since the internal oxide is precipitated in a wavy shape in the material, there is still a problem in wear resistance. (2) The conductivity is lower than that of the material produced by the method of internal oxidation under the low oxygen partial pressure. (3) The stability of the contact resistance still has a problem. (4) Due to its high hardness, it is difficult to process it into a predetermined contact shape.

In order to solve the drawbacks of the method using the melting / casting method as described above, a method using the powder metallurgy method has been proposed. That is, a method is known in which a raw material powder containing silver is molded, sintered, and then internally oxidized under a high oxygen partial pressure. In this method, when the raw material powder is made to contain the additive element in the form of oxide, oxide particles of 1 μm or less are finely and uniformly deposited in the step of internal oxidation under the above-mentioned high oxygen partial pressure, resulting in high temperature of the material. Results in increased strength. Therefore,
It is possible to manufacture a material whose wear resistance is remarkably improved because the wear caused by the arc generated when the contact is opened and closed is suppressed, and the wavy precipitation of the internal oxide ((1) above) that occurs in the material with a particularly high additive element concentration does not occur. it can. However, the silver-oxide-based sintered electrical contact material produced by this method has a problem that the electrical conductivity is still low.

[0010]

Therefore, in view of the above circumstances, the present invention is a silver-oxide system having not only excellent contact resistance stability, welding resistance and wear resistance but also high conductivity. It is an object to provide a sintered electrical contact material and a method for manufacturing the same.

[0011]

The first aspect of the present invention (hereinafter referred to as the first invention) is a method of forming a raw material powder containing silver, sintering the same, and then performing high-pressure internal oxidation. The obtained internal oxidant is an atmosphere having an oxygen partial pressure lower than the oxygen partial pressure of the high-pressure internal oxidation or an atmosphere substantially containing no oxygen, and higher than the temperature of the high-pressure internal oxidation,
And a heat treatment at a temperature of 400 to 960 ° C., which is a method for producing a silver-oxide-based sintered electrical contact material.
Here, the high-pressure internal oxidation means internal oxidation carried out under conditions of an oxygen partial pressure of 50 to 500 atm and a temperature of 200 to 900 ° C.

A second aspect of the present invention (hereinafter referred to as the second aspect of the invention) is the sintered body obtained in the first aspect of the invention.
This is a method of performing internal oxidization after densification processing in order to further improve wear resistance of the silver-oxide-based sintered electrical contact material. A third aspect of the present invention (hereinafter referred to as the third aspect) is produced by the method for producing a silver-oxide sintered electrical contact material according to the first aspect or the second aspect, and has a conductivity of 60%.
It is a silver-oxide type sintered electrical contact material having (IACS) or more.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a silver-oxide-based sintered electrical contact material according to the first invention and the second invention, the additive elements added to Ag are Sn, Zn, In, Al,
Cd, Ga, Mg, Mn, Sb, Ti, Zr, Ca, C
e, Be, Th, Sr, Cr, Hf, Si, Bi, P
At least one selected from the group consisting of b, Fe, Ni and Co can be mentioned. The densification process in the second invention is performed to improve the wear resistance of the produced silver-oxide-based sintered electrical contact material, and specifically, compression process, forging process, extrusion process and the like are performed. Can be mentioned.

The raw material powder to be subjected to the powder metallurgy method is usually
The additive element is contained in an oxide form in an amount of 1 to 30% by weight and in a metallic form in an amount of 0.5 to 20% by weight. If the amount of the oxide is less than 1% by weight, the conductivity of the silver-oxide-based sintered electrical contact material is high and the contact resistance is low, but the wear resistance and the welding resistance are deteriorated. When it exceeds the above range, the wear resistance and the welding resistance are improved, but the conductivity is lowered, the contact resistance is further increased, and the resistance becomes unstable.

In the first and second inventions, after the high-pressure internal oxidation, the obtained internal oxidant is subjected to an atmosphere having an oxygen partial pressure lower than the oxygen partial pressure of the high-pressure internal oxidation or an atmosphere containing substantially no oxygen. , And higher than the temperature of the high-pressure internal oxidation and at a temperature of 400 to 960 ° C. is important. By performing the heat treatment in this way, the third
The invention is capable of producing a silver-oxide-based sintered electrical contact material having an electrical conductivity of 60% (IACS) or more.

The reason for this is considered as follows. That is, during high-pressure internal oxidation, oxygen is excessively diffused into the material under a high oxygen partial pressure, so that oxygen is supersaturated as a solid solution in the material even after high-pressure internal oxidation. This supersaturated solid solution oxygen reduces the conductivity of the silver-oxide-based sintered electrical contact material. By performing the heat treatment as described above, oxygen dissolved in the supersaturation as a solid solution is released, and the conductivity becomes 60% (IAC).
It is believed that S) and above silver-oxide based sintered electrical contact materials can be produced. The temperature of this heat treatment is 400 ° C
If it is less than the above, the above-mentioned release of oxygen is not sufficient, and the conductivity is 60.
% (IACS) or more of a silver-oxide-based sintered electrical contact material is difficult to manufacture, and above 960 ° C., melting of the material becomes conspicuous. The atmosphere in the heat treatment is preferably an atmosphere having an oxygen partial pressure of 0.21 atm or less or an atmosphere containing substantially no oxygen because the atmosphere preparation is simple and easy. The heat treatment improves the conductivity of the silver-oxide-based sintered electrical contact material, so that the temperature rise during opening and closing of the contact is reduced, and therefore the contact resistance is lower and more stable.

[0017]

EXAMPLES Examples of the second and third inventions, comparative examples and conventional examples will be described below. [Example 1] 9 wt% of Sn was contained, and the balance was substantially Ag.
Was melted by a helium gas atomizing method at a cooling rate of 104 to 105 ° C./s to prepare an Ag—Sn alloy powder having an average particle diameter of 10 μm or less.
11% by weight and 4% by weight of SnO ₂ powder (average particle size of 0.1 μm or less) and Al ₂ O ₃ powder (average particle size of 0.1 μm or less) were added to this alloy powder and mixed by a ball mill.
The raw material powder thus obtained was compacted using a mold, the compact was sintered in a vacuum atmosphere, and further densified by extrusion to obtain a billet. A rivet was obtained from the extruded billet through the wire rod.

Next, the rivet is set at a temperature of 500 ° C. and an oxygen partial pressure of 3
High-pressure internal oxidation was performed under the conditions of 00 atm. The conductivity was measured with respect to the obtained internal oxidant (the method for measuring the conductivity is
Thereafter, the same applies to other examples, comparative examples, and conventional examples).
Then, in order to remove excess oxygen, the internal oxidant was heat-treated under the conditions of a temperature of 900 ° C., a holding time of 16 hours, and an atmospheric nitrogen stream (oxygen partial pressure of 0 atm). The contact resistance and the conductivity of the obtained electrical contact were measured (the method of measuring the contact resistance is the same in other examples, comparative examples, and conventional examples hereinafter). Furthermore, in order to examine the contact characteristics of this electrical contact, after opening the electrical contact on a copper base metal, a switching test was performed using an electromagnetic contactor. The test conditions are AC220.
V, 50 Hz, reactor load 150 A, switching frequency 0.
It was set to 1 second ON-2.9 seconds OFF, and opened / closed 30000 times (maximum). After the switching test, the contact resistance was measured, and the consumption amount was calculated as the difference in the weight of the electrical contacts before and after the switching test. Table 1 shows the obtained results.

[Examples 2 to 9] Ag-Sn alloy powder was added,
11% by weight and 4% by weight of SnO ₂ powder (average particle size of 0.1 μm or less) and oxide powders shown in Table 1 (all of which have an average particle size of 0.1 μm or less) were added and mixed by a ball mill. Was tested as in Example 1. The results are shown in Table 1.

[Example 10] Ag-Sn alloy powder was added with S
The same test as in Example 1 was carried out except that 15% by weight of nO ₂ powder (average particle size: 0.1 μm or less) was added and mixed in a ball mill. The results are shown in Table 1.

[0021]

[Table 1]

Examples 11 to 19 (1) A molten metal containing 9% by weight of Zn and the balance being substantially Ag was atomized by a helium gas atomizing method at a cooling rate of 104 to 105 ° C./s, and That an Ag—Zn alloy powder having an average particle size of 10 μm or less was produced,
(2) To the Ag—Zn alloy powder of (1), ZnO powder (average particle size 0.1 μm or less) and oxide powders shown in Table 2 (both average particle size 0.1 μm or less) were 11 weight each. %,
4% by weight was added and mixed by a ball mill, and (3) in order to remove excess oxygen, the temperature was 900 ° C., the holding time was 16 hours, and the atmosphere was atmospheric (oxygen partial pressure was 0.21 atm). The same test as in Example 1 was carried out except that the oxidant was heat-treated. Table 2 shows the results.

[Example 20] Z powder was added to Ag-Zn alloy powder.
The same test as in Example 11 was carried out except that 15% by weight of nO powder (average particle size: 0.1 μm or less) was added and mixed by a ball mill. Table 2 shows the results.

[0024]

[Table 2]

[Examples 21 to 29] (1) A molten metal containing 9% by weight of In and the balance being substantially Ag was atomized by a helium gas atomizing method at a cooling rate of 104 to 105 ° C./s, and Table 2 shows that an Ag-In alloy powder having an average particle size of 10 µm or less was prepared, and (2) (1) the Ag-In alloy powder was an In ₂ O ₃ powder (average particle size of 0.1 µm or less). 1 of each oxide powder (all have an average particle size of 0.1 μm or less)
The same test as in Example 1 was conducted except that 9% by weight and 1% by weight were added and mixed by a ball mill. The results are shown in Table 3.

Example 30 Ag-In alloy powder was added with I
The same test as in Example 21 was carried out except that 20% by weight of n ₂ O ₃ powder (average particle size: 0.1 μm or less) was added and mixed in a ball mill. The results are shown in Table 3.

[0027]

[Table 3]

[Conventional Example] A molten metal was cast by a melting / casting method to prepare an Ag-Cd alloy ingot. This alloy ingot was rolled to obtain a wire rod, and a rivet was obtained from the wire rod. Next, the rivet was subjected to high-pressure internal oxidation under the conditions of a temperature of 500 ° C. and an oxygen partial pressure of 300 atm. The electrical contact obtained is 13
It contained wt% CdO. For this electrical contact,
Contact resistance and conductivity were measured. Further, in order to examine the contact characteristics of this electric contact, a switching test was conducted in the same manner as in Example 1. Further, after the switching test, the contact resistance was measured, and the consumption amount was calculated as the difference in the weight of the electrical contacts before and after the switching test. Table 4 shows the obtained results.

[Comparative Example 1] A molten metal was cast by a melting / casting method to prepare an Ag-Sn alloy ingot. This alloy ingot was rolled to obtain a wire rod, and a rivet was obtained from the wire rod. Next, the rivet was subjected to high-pressure internal oxidation under the conditions of a temperature of 500 ° C. and an oxygen partial pressure of 300 atm. The internal oxidant obtained is
It contained 15% by weight of SnO ₂ . The conductivity of this internal oxidant was measured. Then, in order to remove excess oxygen, the internal oxidant was heat-treated under the conditions of a temperature of 900 ° C., a holding time of 16 hours, and an atmospheric nitrogen stream (oxygen partial pressure of 0 atm), and thereafter, as in Example 1. Tested. Table 4 shows the obtained results.

Comparative Example 2 (1) A molten metal was cast by a melting / casting method to obtain Ag-Zn.
An alloy ingot was produced, and (2) in order to remove excess oxygen, a temperature of 900 ° C., a holding time of 16 hours,
The test was performed in the same manner as in Comparative Example 1 except that the internal oxidant was heat-treated under the conditions of atmospheric air (oxygen partial pressure of 0.21 atm). The internal oxidant contained 15% by weight of ZnO. The results are shown in Table 4.

[Comparative Example 3] A test was performed in the same manner as Comparative Example 1 except that an Ag-In alloy ingot was produced by casting a molten metal by a melting / casting method. The internal oxidant is
It contained 20% by weight of In ₂ O ₃ . The results are shown in Table 4.

[0032]

[Table 4]

The following can be said from Tables 1 to 4. That is, each of the electrical contacts manufactured in Examples 1 to 30 has stability of conductivity and contact resistance comparable to those of the conventional Ag-CdO-based electrical contacts, and has excellent welding resistance and resistance. It was also consumable. On the other hand, none of the electrical contacts manufactured in Comparative Examples have sufficient welding resistance and wear resistance.

[0034]

According to the silver-oxide sintered electrical contact material of the present invention and the silver-oxide sintered electrical contact material produced by the method for producing the same, the electrical conductivity, wear resistance, and welding resistance are improved. It is possible to provide a silver-oxide-based sintered electrical contact material having excellent contact resistance and stable contact resistance.

Claims (7)

[Claims] 1. After molding and sintering a raw material powder containing silver,
In the high-pressure internal oxidation method, the internal oxidant obtained by the high-pressure internal oxidation is treated in an atmosphere having an oxygen partial pressure lower than the oxygen partial pressure of the high-pressure internal oxidation, or an atmosphere containing substantially no oxygen, and the high-pressure internal oxidation. Higher than the oxidation temperature and 400
A method for producing a silver-oxide-based sintered electrical contact material, which comprises heat-treating at a temperature of ˜960 ° C. 2. After molding and sintering a raw material powder containing silver,
In the method of high-pressure internal oxidation, after sintering, densification, and then high-pressure internal oxidation, the obtained internal oxidant is treated with an oxygen partial pressure lower than that of the high-pressure internal oxidation. A method for producing a silver-oxide-based sintered electrical contact material, which comprises performing heat treatment in an atmosphere or an atmosphere substantially containing no oxygen, and at a temperature higher than the temperature of the high-pressure internal oxidation and a temperature of 400 to 960 ° C. 3. The method for producing a silver-oxide-based sintered electrical contact material according to claim 2, wherein the densification processing is compression processing, forging processing or extrusion processing. 4. The method for producing a silver-oxide-based sintered electrical contact material according to claim 1, 2 or 3, wherein the oxygen partial pressure during the heat treatment is 0.21 atm or less. 5. The raw material powder is Sn, Zn, In, Al,
Cd, Ga, Mg, Mn, Sb, Ti, Zr, Ca, C
e, Be, Th, Sr, Cr, Hf, Si, Bi, P
5. At least one element selected from the group consisting of b, Fe, Ni and Co is contained in an oxide form of 1 to 30% by weight and a metallic form of 0.5 to 20% by weight. The method for producing a silver-oxide-based sintered electrical contact material according to 1. 6. The high pressure internal oxidation is carried out at an oxygen partial pressure of 50 to 500.
It carries out on the conditions of atmospheric pressure and temperature 200-900 degreeC.
A method for producing a silver-oxide-based sintered electrical contact material according to any one of 1. 7. A silver-oxide-based sintered electrical contact material produced by the method according to claim 1 and having an electrical conductivity of 60% (IACS) or more.