JPH101730A - Method for producing silver-oxide based sintered electrical contact material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a method using powder metallurgy, which can produce a silver-oxide based sintered electrical contact material with good workability, and to improve conductivity, contact resistance, stability of contact resistance, and wear resistance. Provided is a method for producing a silver-oxide based sintered electrical contact material having excellent heat resistance and welding resistance. SOLUTION: (1) Ag powder having an average particle diameter of 10 μm or less, and (2) Ag powder having an average particle diameter of 10 μm or less and a compounding amount of 4 to
15% by weight of Sn powder, Zn powder, In powder or Cd powder, and (3) component containing Sn, Zn, In and Cd.
A first step of mixing at least one oxide selected from the group consisting of an oxide powder having an average particle diameter of 1 μm or less and a compounding amount of 1 to 5% by weight in terms of metal, a mixed powder , A third step of sintering the compact, a fourth step of densifying the sintered body, and a fifth step of internally oxidizing metallic components other than Ag in the densified body.
And a sixth step of heat treating the internal oxidant to remove excess oxygen contained in the internal oxidant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a silver-oxide based sintered electrical contact material.

[0002]

2. Description of the Related Art Silver-oxide based sintered electrical contact materials are used in switching devices such as relays, conductor safety breakers, wiring circuit breakers, air circuit breakers, etc. over a small to large current range.

As a silver-oxide based electric contact material, Ag-oxide
CdO-based, Ag-SnO ₂ Span, Ag-ZnO-based, Ag-
In ₂ O ₃ type, Ag—MnO type and the like are actually used. These electrical contact materials are obtained by obtaining a silver alloy by a casting method, and then, Cd, Sn, and other components other than Ag in the silver alloy.
It is manufactured by a method of internally oxidizing solute components such as Zn, In, and Mn under a low oxygen partial pressure. However, the silver-oxide based electric contact material has the following disadvantages. That is, (1) The oxide becomes coarser and the dispersion state of the oxide particles becomes more non-uniform within the material, 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) In the case of producing a material having a high oxide concentration in order to improve the wear resistance and welding resistance of the material, the concentration of the solute component to be added is limited to a range capable of forming a solid solution in silver,
Even within the range where solid solution is possible, it takes a long time to complete the internal oxidation step, and sometimes a dense layer of oxide is formed on the surface of the material, and the internal oxidation does not progress.

[0004] The above disadvantages can be solved by internal oxidation under a high oxygen partial pressure. However, a material having a high oxide concentration produced by internal oxidation under a high oxygen partial pressure has the following disadvantages. That is, (1) the oxide is precipitated in a wavy or acicular shape, which causes not only abnormal wear and chipping wear, but also a conductivity lower than that of a material manufactured by internal oxidation under the above low oxygen partial pressure. There is also a problem in the stability of the contact resistance as a contact material. (2) Due to the high hardness, it is difficult to process into a predetermined contact shape.

In order to eliminate the drawbacks of the method of internally oxidizing a silver alloy obtained by the casting method as described above, Ag powder, solute component powder and oxide powder are mixed by powder metallurgy, and then molded and sintered. A method is known in which after sintering, the metallic solute component in the sintered body is internally oxidized under a high oxygen partial pressure. However, the silver-oxide-based sintered electrical contact material produced by this method has a problem that the conductivity, the contact resistance, the stability of the contact resistance, the wear resistance, and the welding resistance are all insufficient.

[0006]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has improved a method using the above powder metallurgy, which can produce a silver-oxide-based sintered electrical contact material with good workability.
An object of the present invention is to provide a method for producing a silver-oxide-based sintered electrical contact material having excellent electrical conductivity, contact resistance, stability of contact resistance, wear resistance and welding resistance.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to achieve the above object, and as a result, (1) excellently disperse the particles of oxide powder used as a raw material powder as uniformly and finely as possible. And (2) heat treatment of the internal oxidant to obtain excellent electrical conductivity and contact resistance. That is, the first invention is:
(1) Ag powder having an average particle diameter of 10 μm or less, and (2) Sn powder, Zn powder, In powder or Cd powder having an average particle diameter of 10 μm or less and a blending amount of 4 to 15% by weight,
(3) The component consists of at least one oxide selected from the group consisting of Sn, Zn, In and Cd, has an average particle size of 1 μm or less, and has a compounding amount of 1 to 5% by weight in terms of metal.
A first step of mixing the oxide powder, a second step of molding the mixed powder, a third step of sintering the compact, and a third step of internally oxidizing a metallic solute component in the sintered body. 4. A method for producing a silver-oxide based sintered electrical contact material comprising the step of 4 and the fifth step of heat-treating the internal oxidant in order to remove excess oxygen contained in the internal oxidant (claim 1). .

According to a second aspect of the present invention, in the first aspect, after the step of sintering the compact and performing the step of densifying the sintered body, the metallic solute component in the densified body is internally oxidized. (Step 2).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

[Mixed Powder] The raw material powder used in the method for producing a silver-oxide-based sintered electrical contact material of the present invention includes (1) Ag powder,
(2) Sn powder, Zn powder, In powder or Cd powder, and (3) at least one oxide powder selected from the group consisting of Sn, Zn, In and Cd. Ag powder is a main raw material constituting a silver-oxide based sintered electrical contact material. Sn powder, Zn powder, In powder or C powder
The powder d is oxidized in a subsequent internal oxidation step, and is finely dispersed and precipitated as an internal oxide to increase the high-temperature strength. Further S
At least one oxide powder selected from the group consisting of n, Zn, In, and Cd makes it difficult to form a dense oxide film on the surface of a sintered body or a densified body in an internal oxidation step, and the internal oxide And the internal stress generated due to expansion due to the internal oxidation is reduced at the particle interface of the oxide powder. Therefore, cracks are less likely to occur on the surface, and the yield is improved.

It is important to disperse such oxide powder particles as uniformly and finely as possible. Uneven dispersion of the oxide powder particles causes the following disadvantages. That is, during the production of the silver-oxide based sintered electrical contact material, the internal oxide is precipitated in a wavy or acicular shape in the internal oxidation step. Therefore, when the silver-oxide based sintered electrical contact material is used, abnormal wear or chipping wear occurs. Even if the internal oxide does not have a wavy or needle-like precipitation, the dispersion state of the oxide powder particles at the contact portion changes with the progress of consumption due to the opening and closing of the sintered electrical contact during use (segregation of the Ag component may occur). Advance), characteristics such as contact resistance and wear resistance are affected.
Therefore, stable electrical contact characteristics cannot be obtained, leading to a decrease in the reliability of the electrical contacts. Hereinafter, the raw material powder will be further described.

(1) Ag powder (a) The average particle size is 10 μm or less, preferably 1 μm or more. If the average particle size of the Ag powder exceeds 10 μm, the oxide powder particles are scattered around the Ag powder particles having an average particle size of more than 10 μm, so that the above-described oxidation in the sintered body obtained later is performed. The dispersion of the material powder particles becomes non-uniform. On the other hand, when the average particle size is less than 1 μm, the dispersion state of the oxide powder particles is not greatly improved, and this is economically disadvantageous.

(2) Sn powder, Zn powder, In powder and Cd powder (a) Component Only one of these single powders is blended and used. Ag
When it is used as an alloy powder with, for example, or when two or more kinds of these single powders are used, it takes time for the internal oxidation step, and the dispersion and particle size of the internal oxide generated by being oxidized in the internal oxidation step Tends to be uneven. (B) Average particle size is 10 μm or less, preferably 1 μm or more. The reason is the same as the reason for the Ag powder. (C) The blending amount is 4 to 15% by weight. When the content is less than 4% by weight, the amount of the internal oxide is too small, so that the conductivity is high and the contact resistance is small, but the wear resistance and the welding resistance are deteriorated. On the other hand, 15
If the content exceeds 10% by weight, the wear resistance and the welding resistance are improved, but the electrical conductivity is reduced, and the contact resistance is large and unstable.

(3) At least one oxide powder selected from the group consisting of Sn, Zn, In and Cd. (A) The average particle size is 1 μm or less, preferably 0.1 μm or less. When the average particle size of the oxide powder exceeds 1 μm, the dispersion of the particles of the oxide powder tends to be uneven. (B) Compounding amount It is 1 to 5% by weight in terms of metal. When the content is less than 1% by weight, the above-mentioned effect of the oxide powder is dilute. On the other hand, when the content is more than 5% by weight, the conductivity is reduced, and the contact resistance becomes large and unstable. No more increase.

[Densification Processing] Densification processing is performed on the sintered body and before internal oxidation. By the internal oxidation in this manner, the bonding force between the particles in the sintered electrical contact material becomes stronger than in the case where the densification processing is not performed, and the sintered electrical contact material having an appropriate hardness that does not easily crack on the surface. It becomes a contact material. Examples of densification include extrusion, compression, and forging.

[Internal Oxidation] By performing internal oxidation, a reduction in the diffusion rate of oxygen is extremely suppressed, and internal oxide particles that are easily coarsened are finely and uniformly deposited and dispersed to 1 μm or less throughout the sintered electrical contact material. Can be done. As a result, the sintered electrical contact material has an increased high-temperature strength, and thus the consumption of the sintered electrical contact material by an arc generated when the contacts are opened and closed is suppressed. Such improvement in wear resistance
It also prevents welding due to Ag segregation that progresses with an increase in the number of times of opening and closing.

(1) Oxygen partial pressure and temperature The oxygen partial pressure is 30 to 600 kgf / cm ² , and the temperature is 2
The temperature is preferably from 00 to 900 ° C. Oxygen partial pressure is 30k
If it is less than gf / cm ² , as described in the related art, (a) the inner oxide becomes coarser as it goes inside the material, (b) a thin layer of oxide is formed in the center of the material,
And (c) the phenomenon that a dense layer of oxide is formed on the material surface is likely to occur. Since the diffusion rate of oxygen decreases in any of these cases, (a) the rate of growth and coarsening of internal oxide particles is higher than the rate of nucleation when the tip of internal oxidation passes, and (b) This is a phenomenon caused by the diffusion of the solute element toward the surface.
Preferably, the temperature is increased or decreased to adjust the oxygen partial pressure.

(2) Time The time required for precipitating the internal oxide by internal oxidation is only about two-thirds as compared with the case where the same amount of oxide is precipitated using the ingot material.

[Heat Treatment] In the internal oxidant obtained in the internal oxidation step, oxygen is dissolved in a supersaturated form. The oxygen dissolved in the supersaturation lowers the conductivity of the produced silver-oxide based sintered electrical contact material. In order to release and remove such excess oxygen, the obtained internal oxidant is heat-treated. This heat treatment improves the conductivity of the silver-oxide based sintered electrical contact material, so that the temperature rise during contact opening and closing is small, and the contact resistance is low and stable.

(1) Atmosphere An atmosphere having an oxygen partial pressure lower than that of the internal oxidation or an atmosphere containing substantially no oxygen is preferable. Above all, it is more preferable to prepare an atmosphere having an oxygen partial pressure of 0.21 kgf / cm ² or less or an atmosphere containing substantially no oxygen, because the atmosphere is easily prepared.

(2) Temperature The temperature is preferably higher than the temperature of the internal oxidation and at a temperature of 400 to 960 ° C. If the temperature is lower than 400 ° C., the above-mentioned oxygen is not sufficiently removed, and it is difficult to produce a silver-oxide-based sintered electrical contact material having excellent conductivity. On the other hand, if the temperature exceeds 960 ° C., melting of the internal oxidant becomes conspicuous.

[Total oxide content in sintered electrical contact material] The total oxide content in the sintered electrical contact material produced by the method of the present invention is 1 to 30% by weight. If it is less than 1% by weight, the conductivity of the sintered electrical contact material is high and the contact resistance is small, but the wear resistance and the welding resistance are deteriorated. On the other hand, 30% by weight
When it exceeds, the wear resistance and the welding resistance are improved, but the electrical conductivity is reduced, the contact resistance is large, and it becomes unstable.

[0022]

【Example】

[Example 1] Ag powder (average particle size of 10 µm or less), Sn
Powder (average particle size of 10 μm or less) and SnO ₂ powder (average particle size of 0.1 μm or less) were mixed by a ball mill. Blending in this case, Sn powder is 8.7 wt% (11 wt% in terms of SnO ₂₎ were as SnO ₂ powder is 4 wt% (3.2 wt% in Sn conversion). After the obtained mixed powder was compacted in a mold, the compact was sintered in a vacuum atmosphere, and further extruded into an extruded billet. The extruded billet was processed into a button-shaped bimetallic contact. Next, the bimetal contact was internally oxidized at a temperature of 500 ° C. and an oxygen partial pressure of 300 kgf / cm ² , and then kept in a nitrogen stream at a temperature of 900 ° C. for 16 hours to remove excess oxygen.

In order to examine the contact characteristics of the obtained bimetal contact, Vickers hardness (Hv) and conductivity (% (IAC)
After measuring S)), the following opening / closing test was performed. That is, the above-mentioned bimetal contact sample was welded to a copper base metal, then incorporated into a commercially available electromagnetic contactor having a rated current of 25 A, and the open / close test conditions were set to 220 V AC, 50 Hz, and a reactor load of 1.
50A, opening / closing frequency 0.1 second ON-2.9 second OFF, opening / closing frequency 100000 times.

After the opening and closing test, the contact resistance (mΩ) was measured.
The consumption (mg) was calculated as the weight difference between the bimetallic contact samples before and after the opening / closing test, and the presence or absence of welding of the bimetallic contact samples was observed. Table 1 shows the obtained results.

Examples 2 to 9 Tests were carried out in the same manner as in Example 1 except that the oxide powder mixed with the Ag powder and the Sn powder in a ball mill and the compounding amount were as follows.
That is, Example 2 4% by weight of In ₂ O ₃ powder (3.
Example 3 4% by weight of ZnO powder (3.2 in terms of Zn)
Example 4 4% by weight of CdO powder (3.5 in terms of Cd)
Example 5 2% by weight of SnO ₂ powder (1% by Sn conversion)
6% by weight) and ₂ % by weight of In ₂ O ₃ powder (1.7 in terms of In).
Example 6 2% by weight of SnO ₂ powder (1% by Sn conversion)
6% by weight) and 2% by weight of ZnO powder (1.6% by weight in terms of Zn) Example 7: 2% by weight of In ₂ O ₃ powder (1% by weight in terms of In).
7% by weight) and 2% by weight of ZnO powder (1.6% by weight in terms of Zn). Example 8 2% by weight of In ₂ O ₃ powder (1% by weight in terms of In).
7% by weight) and 2% by weight of CdO powder (1.8% by weight in terms of Cd) Example 9: 2% by weight of ZnO powder (1.6% in terms of Zn)
% By weight) and 2% by weight of CdO powder (1.8% by weight in terms of Cd) The results obtained are shown in Table 1.

[Example 10] A metal powder mixed with a Ag powder and SnO ₂ powder in a ball mill together with a ball mill was used as an In powder, and its compounding amount was 9.1% by weight (11% by weight in terms of In ₂ O ₃ ). Except for the above, the test was performed in the same manner as in Example 1. Table 1 shows the obtained results.

[Examples 11 to 15] Ag powder and In
A test was conducted in the same manner as in Example 10 except that the oxide powder mixed with the powder in a ball mill and the compounding amount thereof were as follows. That is, Example 11: 4% by weight of ZnO powder (3.
Example 12 4% by weight of CdO powder (3% in terms of Cd)
Example 13 2% by weight of SnO ₂ powder (1.6% by weight in Sn conversion) and ₂ % by weight of In ₂ O ₃ powder (1.7% by weight in In conversion) Example 14 2% by weight of SnO ₂ powder (1.6% by weight in Sn conversion) and 2% by weight of ZnO powder (1% in Zn conversion)
Example 15 2% by weight of ZnO powder (1% in terms of Zn)
6% by weight) and 2% by weight of CdO powder (1.8% by weight in terms of Cd) The results obtained are shown in Table 1.

Example 16 A metal powder mixed with an Ag powder and SnO ₂ powder in a ball mill was used as a Zn powder, and the blending amount was 8.8% by weight (11% by weight in terms of ZnO). The test was performed in the same manner as in Example 1. Table 1 shows the obtained results.

Examples 17 to 21 Ag powder and Zn
A test was conducted in the same manner as in Example 16 except that the oxide powder mixed with the powder in a ball mill and the compounding amount thereof were as follows. That is, Example 17: 4% by weight of In ₂ O ₃ powder (3.3% by weight in terms of In) Example 18: 4% by weight of CdO powder (3% by weight of Cd)
Example 19: 2% by weight of SnO ₂ powder (1.6% by weight in terms of Sn) and ₂ % by weight of In ₂ O ₃ powder (1.7% by weight in terms of In) 2% by weight of SnO ₂ powder (1.6% by weight in Sn conversion) and 2% by weight of ZnO powder (1% in Zn conversion)
Example 21 2% by weight of ZnO powder (1% in terms of Zn)
6% by weight) and 2% by weight of CdO powder (1.8% by weight in terms of Cd) The results obtained are shown in Table 1.

Example 22 A metal powder mixed with an Ag powder and SnO ₂ powder in a ball mill together with a ball mill was used as Cd powder, and the blending amount was 9.6% by weight (11% by weight in terms of CdO). The test was performed in the same manner as in Example 1. Table 1 shows the obtained results.

Examples 23 to 27 Ag powder and Cd
A test was conducted in the same manner as in Example 22 except that the oxide powder mixed with the powder in a ball mill and the compounding amount thereof were as follows. That is, Example 23: 4% by weight of I ₂ O ₃ powder (3.
Example 24 4% by weight of ZnO powder (3% in terms of Zn)
Example 25 2% by weight of SnO ₂ powder (1.6% by weight in terms of Sn) and ₂ % by weight of In ₂ O ₃ powder (1.7% by weight in terms of In) Example 26 2% by weight of SnO ₂ powder (1.6% by weight in Sn conversion) and 2% by weight of ZnO powder (1% in Zn conversion)
Example 27 2% by weight of ZnO powder (1% by Zn conversion)
6% by weight) and 2% by weight of CdO powder (1.8% by weight in terms of Cd) The results obtained are shown in Table 1.

Comparative Example 1 Ag powder mixed with Sn powder and SnO ₂ powder in a ball mill together with an Ag powder having an average particle size of 2
The test was performed in the same manner as in Example 1 except that the thickness was 0 μm. Table 1 shows the obtained results.

[0033] [Conventional Example 1] by casting the molten metal by casting, to prepare a 11.8 wt% (15 wt% in SnO ₂煌Ki calculation) including Ag-Sn alloy ingot Sn. This alloy ingot was rolled to obtain a button-shaped bimetal contact. Next, the bimetal contact was oxidized at a temperature of 500 ° C. and an oxygen partial pressure of 300 kgf / cm ² . In order to examine the contact characteristics of the obtained bimetal contact, Vickers hardness (Hv) and conductivity (% (IACS)) were obtained in the same manner as in Example 1.
And the contact resistance (mΩ) were measured, the consumption (mg) was calculated as the weight difference between the bimetallic contact sample before and after the opening / closing test, and the presence or absence of welding of the bimetallic contact sample was observed. Table 1 shows the obtained results.

[Conventional Example 2] A molten metal was cast by a casting method, and Cd was 11.4% by weight (13% by weight in terms of CdO).
After producing an Ag-Cd alloy ingot containing the same, the same test as in Conventional Example 1 was performed. Table 1 shows the obtained results.

[0035]

[Table 1] Vickers hardness Conductivity Contact resistance Consumption amount Welding presence / absence (Hv)% (IACS) (mΩ) (mg) Example 1 135 43 1.6 165 None Example 2 132 40 1.3 155 None Example 3 130 42 1.3 160 None Example 4 136 49 1.2 200 None Example 5 133 44 1.4 170 None Example 6 130 41 1.5 165 None Example 7 139 43 1.2 176 None Example 8 132 44 1.3 186 None Example 9 130 42 1.3 185 None Example 10 115 59 1.3 180 None Example 11 125 57 1.2 179 None Example 12 115 60 1.1 189 None Example 13 120 58 1.3 179 None Example 14 118 56 1.3 180 180 None Example 15 122 61 1.2 185 None Example 16 130 5 1.5 170 None Example 17 131 52 1.3 172 None Example 18 129 53 1.2 175 None Example 19 125 56 1.4 169 None Example 20 119 57 1.3 176 None Example 21 122 56 1.2 180 None Example 22 110 62 1.3 200 None Example 23 109 60 1.1 220 None Example 24 105 63 1.1 225 None Example 25 106 59 1.3 209 None Example 26 110 60 1.3 210 None Example 27 112 60 1.2 232 None Comparative example 1 120 45 2.0 200 None Conventional example 1 150 40 1.7 170 None Conventional example 2 95 65 1.0 260 None

The following can be said from Table 1. That is, (1) the conventional electrical contact manufactured by the casting method has low workability due to high hardness (conventional example 1), or has good workability but low wear resistance (conventional example 2). (2) In contrast, the electrical contacts manufactured in Examples 1 to 27 all had excellent workability, electrical conductivity, contact resistance, stability of contact resistance, wear resistance and welding resistance. . (3) The electrical contact of Comparative Example 1 had an average particle size of 20 μm A
Since g powder was used, the contact resistance was not sufficient.

[0037]

According to the production method of the present invention, a silver-oxide based sinter having excellent workability, conductivity, contact resistance, stability of contact resistance, wear resistance and welding resistance is excellent. The resulting electrical contact material is obtained.

Claims (7)

[Claims] 1. An (1) Ag powder having an average particle size of 10 μm or less, and (2) an Ag powder having an average particle size of 10 μm or less and a compounding amount of 4 to
15% by weight of Sn powder, Zn powder, In powder or Cd powder, and (3) component containing Sn, Zn, In and Cd.
A first step of mixing at least one oxide selected from the group consisting of an oxide powder having an average particle diameter of 1 μm or less and a compounding amount of 1 to 5% by weight in terms of metal, a mixed powder , A third step of sintering the compact, a fourth step of internally oxidizing metallic components other than Ag in the sintered body, and removing excess oxygen contained in the internal oxidant. A method of producing a silver-oxide based sintered electrical contact material comprising a fifth step of heat treating the internal oxidant for the purpose. 2. An (1) Ag powder having an average particle size of 10 μm or less, and (2) an Ag powder having an average particle size of 10 μm or less and a compounding amount of 4 to 4 μm.
15% by weight of Sn powder, Zn powder, In powder or Cd powder, and (3) component containing Sn, Zn, In and Cd.
A first step of mixing at least one oxide selected from the group consisting of an oxide powder having an average particle diameter of 1 μm or less and a compounding amount of 1 to 5% by weight in terms of metal, a mixed powder , A third step of sintering the compact, a fourth step of densifying the sintered body, and a fifth step of internally oxidizing metallic components other than Ag in the densified body.
And a sixth step of heat-treating the internal oxidant in order to remove excess oxygen contained in the internal oxidant. 3. The method for producing a silver-oxide-based sintered electrical contact material according to claim 2, wherein the densification is extrusion, compression, or forging. 4. The internal oxidation is carried out at a partial pressure of oxygen of 30 to 600 k.
The method for producing a silver-oxide-based sintered electrical contact material according to claim 1, wherein the gf / cm ² and the temperature are 200 to 900 ° C. 5. 5. The method of claim 4, wherein the oxygen partial pressure is adjusted by increasing or decreasing the temperature. 6. The heat treatment of the internal oxidant is performed in an atmosphere having an oxygen partial pressure lower than the oxygen partial pressure of the internal oxidation or an atmosphere substantially free of oxygen, and at a temperature higher than the temperature of the internal oxidation and 400 to 960 ° C. The method for producing a silver-oxide-based sintered electrical contact material according to any one of claims 1 to 5, which is performed at a temperature of: 7. The atmosphere having an oxygen partial pressure lower than the oxygen partial pressure for internal oxidation is 0.21 kgf / cm ² or less.
4. The method for producing a silver-oxide based sintered electrical contact material according to item 1.