JPH055139A - Method for producing silver or silver-copper alloy-metal oxide composite material - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for producing a silver or silver-copper alloy-metal oxide composite material having sufficient toughness as an electrode material. [Structure] A mixture containing silver, or silver and copper, and a predetermined element in a metallic and / or oxide form is placed under heating and under a high oxygen partial pressure so that a liquid phase and a solid phase coexist. The material is obtained and then subjected to heavy working and heating to impart toughness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a method for producing a silver or silver-copper alloy-oxide composite material suitable as an electrode material which is continuously used under a large capacity load current.

[0002]

2. Description of the Related Art Electric welding is frequently used for assembling various metal plates in automobiles, electric appliances and the like. This electric welding requires an electrode having a high electric conductivity and a high heat resistance, and a hard copper alloy such as Cr-Cu is generally used. Especially when a large capacity load current is used, a metal oxide, A material obtained by sintering ceramic powder such as carbide with copper is used. However, the dispersion-strengthened material obtained by sintering is 1
For continuous use in applications exceeding 10,000 amperes, the welding resistance and wear resistance are not sufficient, and the electrode life is extremely short.

Such a short electrode life directly increases the production cost, reduces the working capacity due to the necessity of frequently replacing the electrodes, and indirectly increases the production cost. Under such circumstances, development of an electrode material having a longer life is awaited.

[0004]

DISCLOSURE OF THE INVENTION In order to overcome the drawbacks of the internal oxidation method for silver-based electrical contact materials, the present inventor first
According to the binary diagram of the silver-oxygen binary state, it was noted that there is a state in which the α phase of silver and the liquid phase of Ag ₂ O coexist at a temperature of 507 ° C. or higher and an oxygen partial pressure of 414 atm or higher. In this state, the solute element is rapidly oxidized, and the wettability with silver is greatly improved even with the oxide added by the above liquid phase generation, and an extremely hard and dense silver-oxide composite material is obtained. It was found that it can be obtained. According to this high-pressure oxidation method, even an element that forms a heat-resistant oxide can be easily oxidized,
It has been found that a composite material containing a large amount of a heat-resistant oxide can also be produced, and that this material can realize superior performance to conventional hard copper alloys and dispersion strengthened copper alloys.

However, according to this high-pressure oxidation method, the material has poor toughness and is easily damaged by impact. This is not practical as an electrode material.

An object of the present invention is to provide a method for producing a silver or silver-copper alloy or metal oxide composite material having sufficient toughness as an electrode material.

[0007]

In order to achieve the above object, the method for producing a silver-metal oxide composite material of the present invention comprises (A)
Silver and (a) 0.5 to 25% by weight of metal, Mg, A
l, Zr, Ca, Ce, Be, Th, Sr, Ti, C
at least one element selected from r, Hf and Si in metallic and / or oxide form, and optionally (b) 0.01 to 5 wt% Bi, Pb, C in terms of metal
A mixture containing at least one element selected from d, Zn, Sn, Sb, Mn, Fe, Ni and Co in a metallic and / or oxide form is heated and placed under high oxygen partial pressure. The state where the phase and the solid phase coexist, or a state close to that,
As a result, when a metallic element is present, the metal is precipitated as an oxide, and then the oxygen partial pressure is lowered to cool the material, and (B) the material obtained in the (A) step is subjected to strong working. It has a processing step of removing precipitation strain by heating and re-sintering. Also, silver-copper alloy-
In the method for producing a metal oxide composite material, silver and copper in a weight percentage equal to or less than silver are used instead of silver in the step (A).

[0008]

The mother substrate is made of silver or a silver-copper alloy because the electrode material is required to have high electric conductivity. In particular, if a metal oxide is mixed in order to improve welding resistance and wear resistance, a decrease in electric conductivity is unavoidable, and silver and a silver-copper alloy are suitable for maintaining a required electric conductivity. In the case of a silver-copper alloy, copper is effective in improving the mechanical strength of the electrode at a high temperature, but since it is more likely to oxidize as the amount of copper increases, it is necessary to keep the amount of copper equal to or less than that of silver.

The oxide of the element (a) has good heat resistance and is effective in improving welding resistance and wear resistance, but its content must be 0.5 to 25% by weight in terms of metal. .. If it is less than 0.5% by weight, the heat resistance of the composite material is insufficient, and if it exceeds 25% by weight, the matrix is relatively insufficient and the electrical conductivity is too low, and the hardness after high-pressure oxidation treatment is high. Past, (B)
This is because the processing step of becomes difficult.

On the other hand, although the oxide of the element (b) is not so good in heat resistance itself, it has an effect of assisting the oxidation during the oxidative precipitation of the element (a).
It is advisable to add in the range of up to 5% by weight. If it is less than 0.01% by weight, the effect of assisting the oxidation of the element (a) is not sufficient, and if it is added in an amount of more than 5% by weight, the effect of assisting the oxidation is not so improved, and rather the heat resistance strength of the obtained composite material is improved. It may decrease.

In the present invention, both the element (a) and the element (b) may be contained in the form of metal or oxide, or in combination. The mixture of silver, or silver and copper, and the element of (a) and optionally the element of (b) present may be an alloy or a sintered body, and may be an alloy powder, a sintered body powder or It may be a mixed powder of these and silver powder. When an oxide is used, the particle size is preferably 0.1 μm or less.

The above-mentioned silver, or a mixture of silver and copper, and the element of (a) and the element of (b) which is optionally present are placed under high oxygen partial pressure under heating, and a liquid phase and a solid phase coexist. Or it should be in a state close to it. When the element (a) and the element (b) which is present in the mixture are metallic, the metal is precipitated as an oxide, while when added as an oxide, Ag ₂ The liquid phase of O fills the voids with the oxide particles. As a result, the oxygen partial pressure is lowered, and if cooled, hard or dense silver or silver in which the oxide of the element (a) and the element (b) which is present in some cases are finely and uniformly dispersed in the mother substrate. A copper alloy-metal oxide composite material is obtained.

In the above, the temperature at which the liquid phase and the solid phase coexist and the oxygen partial pressure are 507 ° C. or higher and 414 atm or higher in the case of pure gold, but copper, the element of (a) and depending on the case (b). In the case of a silver alloy containing the element (1), this condition is generally lowered to some extent, so it is practical to find the optimum condition within a temperature range of 350 to 830 ° C. and an oxygen partial pressure of 100 to 450 atm.

The following five methods are possible for the processing step (B). That is, (1) the material after the step (A) is wrapped in a metal tube and subjected to hot plastic working, or (2) the material is once crushed and compression-molded and then sintered, or (3) the material. Is crushed once, compressed and sintered, and hot plastically processed,
(4) The material is once crushed, compression-molded, and then subjected to high-pressure oxidation treatment again, or (5) when the mixture to be subjected to the step (A) is a powder, the powder after the step is compression-molded and baked. It is either tied.

In the case of (1), when the metal tube is plastically deformed by hot, the metal tube is plastically deformed, but the silver or silver-copper alloy-metal oxide composite material is repeatedly broken to remove the precipitation strain and re-sinter. However, it becomes a slip deformation due to silver. This increases the toughness of the material and makes it possible to obtain the strength required as an electrode material.

In (2), (3) and (4), once crushed, the precipitation strain is released, and toughness is imparted by compression molding, sintering and subsequent plastic working. The high-pressure oxidation treatment after compression molding of (4) is convenient for forming a silver film on the grain boundaries and the powder surface. That is, when a solid phase and a liquid phase coexist, a liquid phase of Ag ₂ O is generated at the grain boundaries and the powder surface,
By reducing the oxygen partial pressure and cooling, this part returns to pure gold. In this way, this material can be easily deformed and can be plastically worked. In the method (5), the mixing of silver powder facilitates plastic working.

[0017]

[Example] Sample No. 1, 2 ... An alloy having the composition shown in Table 1 was heated and melted at 1000 to 1100 ° C. in a high frequency melting furnace, and this was poured into a graphite mold to obtain a plate-shaped mass of about 5 kg. Next, the upper and lower surfaces of the lump are chamfered by about 2 mm, the plate pressure is reduced by 80% by hot rolling, and the plate material having a thickness of 0.7 mm is further cold rolled, and the obtained plate is punched by a press, I made a chip of 2 mm square. This was internally oxidized by the oxidation treatment shown in Table 1 and then temporarily sintered at a pressure of 1 ton / cm ² to form a billet, heated to 850 ° C. and hot extruded to obtain a diameter of 6 m.
Got m sticks. This rod was cut into a disk having a thickness of 3 mm, and heat-treated in nitrogen at 900 ° C. for 2 hours to obtain an electrode material.

Sample No. 3 ... An alloy having the composition shown in Table 1 was melted by heating in vacuum in the same manner as above, and centrifugally sprayed in nitrogen gas to obtain a powder having a particle size of several hundreds of microns. This was subjected to an oxidation treatment shown in Table 1 and further pulverized, then compacted and filled in a copper tube having a thickness of 1 mm, formed into a billet, and then subjected to hot extrusion at 800 ° C. The obtained rod was further processed with a swager to have a diameter of 6 mm. From this, a disk having a thickness of 3 mm was cut and heat-treated at 900 ° C. for 2 hours in a vacuum of 10 ⁻³ torr to obtain an electrode material.

Sample Nos. 4, 5 ... Alloys having the compositions shown in Table 1 were melted in the same manner as above, and the molten metal was made into alloy powder by the water atomizing method. After the powder was subjected to the oxidation treatment shown in Table 1, the powder was crushed with a ball mill and then powder compacted at a pressure of 1 ton / cm ² , and the powder was kept in vacuum at 750 ° C. Hold for about 3 hours to reduce and sinter, diameter 6
A disk having a size of 3 mm and a thickness of 3 mm was formed into an electrode material.

Each oxidation treatment was carried out as follows. That is, the sample is inserted into an oxidation container, first the inside of the container is replaced with nitrogen gas, then the temperature is raised to a predetermined temperature, pure oxygen is allowed to flow into the container, and the oxygen pressure is increased to a predetermined value. The sample was taken out after being kept for 48 hours and then cooled under reduced pressure.

Welding test: Diameter 6m treated by each of the above methods
A disk having a thickness of 3 mm and a thickness of 3 mm was inserted and joined to the tip of a standard electrode holder and subjected to a comparative test of electrode life. Cr-C with a diameter of 16 mm and a height of 25 mm as an electrode holder
u standard product with a diameter of 6 mm and a depth of 2 m at the tip
A hole of m was carved, the disc was press-fitted and joined, and the upper end surface was sharpened and polished into a trapezoid having a diameter of 5 mm to obtain a test electrode. As the material to be welded, two 0.8 mm thick galvanized steel sheets were stacked and used. Welding current is 8,000 amps or 1
It was set at 5,000 amps. For comparison of electrode life, a Cr-Cu electrode was used for 8,000 amps, and an alumina-dispersed copper electrode was used for 15,000 amps. The results are shown in Table 1.

[0022]

[Table 1]

From Table 1, the electrode material of the present invention is a conventional Cr-
It can be seen that the life is about three times longer than that of the Cu and alumina dispersed copper electrode material.

[0024]

According to the method of the present invention, a high strength and high toughness silver or silver-copper alloy-metal oxide composite material can be obtained, and a practical electrode material can be manufactured.

Claims (1)

Claims: (A) Silver and (a) 0.5 to 0.5 in terms of metal.
25% by weight of Mg, Al, Zr, Ca, Ce, Be, T
0.01 to 5% by weight in terms of a metal and / or an oxide of at least one element selected from h, Sr, Ti, Cr, Hf and Si, and optionally (b) metal.
Bi, Pb, Cd, Zn, Sn, Sb, Mn, Fe,
A state where a mixture containing at least one element selected from Ni and Co in a metallic state and / or an oxide state is heated and placed under a high oxygen partial pressure, or a state where a liquid phase and a solid phase coexist or a state close thereto. Accordingly, when the element of (a) and the element of (b) which is present in some cases are metallic, the element is precipitated as an oxide, and then the oxygen partial pressure is reduced to cool, and ( B) A method for producing a silver-metal oxide composite material, comprising: a step of subjecting the material obtained in the step (A) to strong working and heating to remove precipitation strain and re-sinter. 2. (A) Silver, copper in an amount equal to or less than silver, and (a) 0.5 to 25% by weight of Mg, A in terms of metal.
l, Zr, Ca, Be, Th, Sr, Ti, Cr, Hf
And at least one element selected from Si in a metallic and / or oxide form, and optionally (b) 0.01 to 5% by weight of Bi, Pb, Cd, Zn, in terms of metal.
A mixture containing at least one element selected from Sn, Sb, Mn, Fe, Ni and Co in metallic and / or oxide form is heated and placed under high oxygen partial pressure to form a liquid phase and a solid phase. In a state of coexisting with or close to it, and when the element of (a) and the element of (b) which is present in some cases are metallic, the element is precipitated as an oxide and then the oxygen partial pressure is changed. Silver-copper alloy-metal oxide composite having a step of lowering and cooling, and a step of (B) a step of subjecting the material obtained in the step (A) to strong working and removing the precipitation strain by heating and resintering Material manufacturing method. 3. The method according to claim 1, wherein the mixture in step (A) is an alloy. 4. The method according to claim 1, wherein the mixture in step (A) is a sintered body. 5. The method according to claim 1, wherein the mixture in the step (A) is alloy powder, sintered powder, or a mixed powder of these and silver powder. 6. The method according to claim 1, wherein the oxide used in the step (A) has a particle size of 0.1 μm or less. 7. The method according to claim 1, wherein, in the processing step (B), the material after the step (A) is wrapped in a metal tube and molded by hot plastic working. 8. The method according to claim 1, wherein in the processing step (B), the material after the step (A) is once crushed, and compression-molded and then sintered.
Method 3, 4, or 5. 9. The process of (B), wherein the material after the process of (A) is once crushed, compressed and sintered, and hot plastically worked. Method 5 10. The method according to claim 5, wherein in the processing step (B), the powder after the step (A) is compression molded and sintered. 11. A state in which a liquid phase and a solid phase coexist in the processing step (B) in which the material after the step (A) is once crushed, compression-molded, then reheated and placed under high oxygen partial pressure. And then cooling by lowering the oxygen partial pressure.