JPH05205555A - Manufacture of contact material - Google Patents

Abstract

PURPOSE:To provide electric contact material having high degree of sintering easily by using powder, obtained after adding sintering performance improving powder, which makes sintering obstructing material harmless, and processing mechanical alloying, as allay powder. CONSTITUTION:Metal powder for basis material and metal powder for reinforcing contact characteristic are mechanical allaying processed so as to be allay, and the compact of the powder of the allay is sintered so as to obtain contact material formed of sintered body where metal particles for reinforcing the contact characteristic disperse in basis metal. In this case, powder, obtained after adding sintering performance improving powder, which makes sintering obstructing material harmless, to the metal powder for the basis material and the metal powder for reinforcing the contact characteristic, and performing mechanical alloying processing, is used as alloy powder. Powder, for instance titanium powder, tungusten powder, which reacts easily with sintering obstructing material, such as oxygen, carbon, or the like, so as to produce oxide or carbide, as sintering performance improving powder. Thereby contact material having high degree of sintering, where the metal particles are finely dispersed in sufficient quantity, is obtained easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing electric contact materials such as relays, contactors and breakers.

[0002]

2. Description of the Related Art A highly conductive metal substrate (for example, a silver substrate)
By dispersing metal particles (for example, nickel particles) for strengthening contact characteristics (different from the base metal) therein, the metal base (matrix) is strengthened to improve contact characteristics. It is generally said that the contact material in which other metal particles are dispersed in the metal matrix is strengthened because the movement of dislocations in the dispersed particles is hindered (for example, Orowan's theory). In this case, the narrower the space between the metal particles for strengthening the contact characteristics (hereinafter, appropriately referred to as "metal particles for strengthening"), the higher the strengthening effect. To narrow the spacing between the reinforcing metal particles,
The content may be increased or dispersed as finer particles. It can be dispersed in

However, in the former case where the content of the reinforcing metal particles is increased, the electrical characteristics are deteriorated even if the interval between the metal particles is narrowed. That is, when the content of the metal particles is increased, the electric resistance becomes high, and there arises a problem that the necessary electric conductivity cannot be maintained. On the other hand, the latter case, which is aimed at dispersion miniaturization, involves technical difficulties. Conventionally, the above-mentioned contact material is made by a so-called powder metallurgy method. That is, assuming that the metal for the base material is silver, the contact material is a sintered body obtained by mixing and molding silver powder and a metal powder that separates silver into two phases, and firing. The degree of dispersion and refinement of the separated metal is basically governed by the particle size of the metal powder, and it is difficult to proceed with the fine dispersion. Recently, there are ultrafine particles made by evaporating metal in vacuum, and it seems that it is possible to easily realize fine dispersion by using them, but it does not actually work. This is because, even if the ultrafine particles have a small primary particle size, they coagulate and behave as particles having a large secondary particle size at the stage of use, so that eventually they cannot be finely dispersed.

In addition to the above two methods, fine dispersion is promoted by heating to a high temperature where the solid solubility limit of the two-phase separated metal increases, forcibly stirring, and then rapidly cooling (ultra-quenching). However, even if fine dispersion can be achieved, the solid solution limit is low and a sufficient amount of metal particles for strengthening cannot be secured, and as a result, sufficient strengthening cannot be achieved.

Therefore, the inventors have paid attention to the alloy powder which has been recently developed by the mechanical alloying treatment. In the case of this alloy powder, an alloy powder which cannot be obtained by the conventional method can be obtained by mixing two or more kinds of different metal powders in a ball mill (including a vibration mill, an attritor, a planetary ball mill, etc.). By using this method, it is possible to obtain an alloy powder in which the metal is in a solid solution-like state in a range exceeding the solid solution limit in the melting method.

For example, by mechanically alloying a metal powder such as a silver powder, a nickel powder, or an iron powder, a powder containing a large amount of nickel or iron in a solid solution state in a silver base can be obtained. By using this powder, it becomes possible to obtain a contact material in which a sufficient amount of nickel particles and iron particles are finely dispersed in the silver base.

[0007]

However, the alloy powder produced by the mechanical alloying process has poor sinterability. Impurities (for example, oxygen, carbon, etc.) mixed during the mechanical alloying process become a gas during firing and prevent sintering. Even if fine dispersion can be achieved, if the sintering is not sufficient, a sufficient increase in hardness will not be observed in the obtained contact material, and there will be a problem that the electrical conductivity will decrease. .. Even if the gas generated during firing is removed by a hot isostatic pressing method, a hot pressing method, or the like, it is difficult to sufficiently sinter.

In view of the above circumstances, it is an object of the present invention to provide a method capable of easily obtaining an electric contact material having a high degree of sintering, in which a sufficient amount of metal particles for strengthening a contact are finely dispersed. To do.

[0009]

In order to solve the above-mentioned problems, the present invention provides a contact material comprising a sintered body in which metal particles for enhancing contact characteristics are dispersed in a metal base. In the method for producing a contact material, wherein a sintered body is obtained by firing a molded body of an alloy powder alloyed by mechanical alloying with a metal powder and a metal powder for strengthening contact characteristics, as the alloy powder,
A powder obtained by mechanically alloying with a sinterability improving powder that renders a sintering-inhibiting substance harmless to both metal powders is used.

Highly conductive silver powder is suitable as the metal powder for the base material, and nickel powder and / or iron powder is suitable as the metal powder for strengthening the contact characteristics.
The sinterability improving powder easily reacts (oxidizes or carbonizes) with sintering interfering substances such as oxygen and carbon to form oxides and carbides, but it is highly reactive with titanium powder, tungsten powder, etc. Metal powders are suitable. Other examples include aluminum powder, alkali metal powder, and alkaline earth metal. Calcium powder, barium powder, phosphorus powder, etc. can be used. The powder for improving sinterability may be a nonmetal. Therefore, the alloy powder used in the present invention may contain some non-metal.

On the other hand, examples of the sintering-inhibiting substance include carbon and organic substances containing carbon in addition to oxygen. The mechanical alloying process in the present invention includes, for example, ball milling (vibrating mill, attritor,
It is a method of pulverizing and mixing at room temperature in an inert gas atmosphere to alloy them using a planetary ball mill. Generally, it is preferable to use the balls in an amount of 50 to 200 times the total weight of the powders to be mixed.

As described above, even if a substance that renders the sintering-inhibiting substance harmless is added, it is always possible to avoid mixing the sintering-inhibiting substance as much as possible. It is recommended to put the raw material powder in the ball mill in an inert gas atmosphere (oxygen-free atmosphere) and to prevent the alloy powder from coming into contact with the air even when taking out the produced alloy powder, but it is not necessary to complete it. .. Even if it is perfect, it is impossible to avoid mixing oxygen and carbon from the pot material of the ball mill, etc., and the manufacturing cost will increase drastically with the aim of perfection.

In the alloy powder obtained by the mechanical alloying method, it is preferable that the metal for the base material, the metal for enhancing the contact characteristics and the sinterability improving substance are in a solid solution similar state. For example, if silver and nickel or iron, and further titanium and tungsten are in a solid solution similar state, when X-ray diffraction analysis is performed, when nickel, iron, titanium, and tungsten are not in solid solution with silver, This can be confirmed by the disappearance of the peaks appearing at specific positions.

The preferred blending ratio of each powder to be mixed in the mechanical alloying treatment is as follows. Total amount of metal powder for base material (silver powder, etc.), metal powder for strengthening contact characteristics (nickel powder, iron powder, etc.) and sinterability improving powder (titanium powder, tungsten powder, etc.) 100
1 wt% to 20 wt% of metal powder for strengthening contact characteristics out of wt%
And the sinterability improving powder is 0.1 to 5 wt%,
A formulation in which the balance is metal powder for the base is suitable. If the metal powder for strengthening the contact characteristics is less than 1 wt%, the effect of addition is weak, and if it exceeds 20 wt%, the contact characteristics tend to deteriorate rather. With respect to the powder for improving sinterability, too, if less than 0.1 wt%, the effect of addition is small, and if it exceeds 5 wt%, the contact characteristics tend to deteriorate rather.

The specific amount of the powder for improving the sinterability is determined by measuring the oxygen and carbon contents in the alloy powder obtained by mechanical alloying without adding this powder,
The amount may be set according to this measurement result.

[0016]

In the method of manufacturing the contact material according to the present invention, since the powder obtained by alloying the metal powder for the base material and the metal powder for strengthening the contact characteristics by the mechanical alloying treatment is used, the metal particles for strengthening the contact characteristics should be sufficient. Finely dispersed in various amounts. Further, in the case of the present invention, the mechanical alloying treatment is performed by adding the powder for improving the sinterability, and the mixed sintering interfering substance reacts with the powder for improving the sinterability in the granulation step or the firing step, and is burned. It has been changed to oxides and carbides that do not impair the binding property, and as a result, the gas generation phenomenon at the firing stage can be avoided, and a sufficiently sintered contact material can be obtained.
Further, the oxides and carbides generated by the reaction remain in the sintered body in a finely dispersed state, but they do not pose any problem and rather contribute to the improvement of the contact characteristics.

It is possible to mix the sinterability-improving powder after the mechanical alloying treatment, that is, to add it later, but the post-addition does not exert an appropriate detoxifying effect. When added afterwards, the sinterability improving powder cannot be spread evenly just by mixing normally, and oxygen and carbon that are not sufficiently close to the sinterability improving powder become unreacted and become a gas and burned. Because it interferes with the result. When the powder for improving sinterability is mixed at the stage of mechanical alloying, that is, when it is added in advance, the powder for improving sinterability is uniformly dispersed throughout the mechanical alloying process, and oxygen and carbon mixed as impurities are removed. All of them react with the powder for improving the sinterability and change into substances that do not harm the sintering, and the sintering proceeds sufficiently.

FIG. 1 is a graph showing the material density (filling rate) in each contact material manufacturing process, the solid line shows the case of the present invention, and the broken line shows the conventional case. In the conventional method, the generation of oxygen gas or carbon gas hinders the sintering, and the density is greatly lowered by the firing, whereas in the method of the present invention, the density is improved by the firing, and the sintering interfering substance is It can be seen that it is sufficiently harmless.

FIG. 2 is a graph showing the material hardness in each manufacturing process of the contact material, in which the solid line shows the case of the present invention and the broken line shows the case of the prior art. Even if the density is finally increased by compression if the sintering is not sufficient, the hardness is very low because the grain boundaries are not firmly bonded to each other as in the conventional case, whereas the hardness is very low. When the sintering is sufficient, the grain boundaries are firmly bonded to each other, and the hardness is high, and important properties such as welding resistance are improved.

Further, in the case of the present invention, in carrying out the treatment, it is necessary to carry out a treatment which is particularly difficult because the operation of adding an appropriate amount of the sinterability improving powder is added during the mechanical alloying treatment. Without, it is very easy to implement and good contact materials can be easily obtained.

[0021]

Embodiments of the present invention will be described below. The present invention is of course not limited to the following embodiments. -Example 1-Silver powder, nickel powder, and titanium powder in a weight ratio of 87: 1
It was weighed at a ratio of 0: 3 and set in a steel pot in a glove box which had been purged with argon gas. The silver powder is a 350 mesh electrolytic silver powder, and the nickel powder is carbonyl nickel powder.

The total amount of powder and the amount of stainless steel balls were set to be 1: 100 in weight ratio. And
Mechanical alloying treatment was performed in a low energy ball mill for 300 hours to obtain an alloy powder. In this alloy powder, the presence of nickel and titanium dispersed in silver in a solid-solution-like state was analyzed by X-ray diffractometry, and peaks appearing when undissolved nickel and titanium were present. Was confirmed by disappearing and not existing.

Subsequently, the alloy powder was molded into a cylindrical shape having a diameter of 20 mm at a pressure of 10 kgf / mm ² and then fired. In the firing process, heat treatment is performed at a temperature of 850 ° C. for 4 hours, and then 450
After hot extruding at a temperature of 90 ° C. and a pressure of 90 kgf / mm ² , heat treatment was performed again at a temperature of 850 ° C. for 4 hours to obtain a sintered body. Subsequently, the sintered body was hot extruded at a temperature of 450 ° C. to obtain a wire contact material having a diameter of 6 mm. FIG. 3 is a scanning electron micrograph showing the metallographic structure of this wire. It can be clearly seen that nickel and titanium compounds are finely dispersed in the silver base.

-Example 2-A silver powder, a nickel powder, and a tungsten powder in a weight ratio of 8
A contact material was obtained in the same manner as in Example 1 except that weighing was performed at a ratio of 7: 10: 3. FIG. 4 is a scanning electron micrograph showing the metal structure of the wire material which is the contact material obtained in Example 2. After all, it is well understood that nickel and tungsten compounds are finely dispersed in the silver base.

Example 3 The same as Example 1 except that the nickel powder was replaced with iron powder and silver powder, iron powder, and titanium powder were weighed at a weight ratio of 87: 10: 3. To obtain the contact material. -Comparative Example 1-A contact material was obtained in the same manner as in Example 1 except that silver powder and nickel powder were weighed at a weight ratio of 90:10.

The Vickers hardness of the wire material which is the contact material of the examples and comparative examples was measured. The hardness was measured under the condition that a load of 100 g was applied for 15 seconds. The measurement results are shown in Table 1. Furthermore, using the obtained contact material, the head diameter is 4
A rivet contact having a diameter of 2 mm and a foot diameter of 2 mm was prepared and subjected to an ASTM type contact tester to examine the welding resistance, which is important as a contact property. The measurement conditions are as follows.

Inrush current: 90 A Steady current: 2
0A load ... Capacitor load The result is shown by ρ90 of the number of initial welding. The results are shown in Table 1.

[0028]

[Table 1]

As shown in Table 1, the contact materials of the examples show an increase of about 20% in hardness as compared with the contact materials of the comparative examples, and accordingly, the welding resistance is improved. I understand. That is, it was possible to improve the sinterability and improve the contact characteristics by adding the sinterability improving powder.

[0030]

As described above, in the method of manufacturing the contact material according to the present invention, the metal powder for the base material and the metal powder for strengthening the contact characteristics are alloyed by the mechanical alloying treatment. A sufficient amount of metal particles for strengthening contact characteristics can be finely dispersed, and mechanical alloying treatment is performed by adding powder for improving sinterability. At the stage, it has been changed to a substance that does not interfere with the sinterability by reacting with the powder for improving sinterability, so that the sintering is sufficient, and an appropriate amount of sinterability is obtained during the mechanical alloying process. Since an operation involving extra difficulty is not added to the extent that an operation of adding the improving powder is added, it is possible to easily obtain a contact material having excellent characteristics.

[Brief description of drawings]

FIG. 1 is a graph showing a material density (filling rate) in each manufacturing process of a contact material.

FIG. 2 is a graph showing the material hardness of each manufacturing process of a contact material.

FIG. 3 is a scanning electron micrograph showing the surface (metal structure) of the contact material of Example 1.

4 is a scanning electron micrograph showing the surface (metal structure) of the contact material of Example 2. FIG.

Claims (5)

[Claims] 1. To obtain a contact material composed of a sintered body in which metal particles for enhancing contact characteristics are dispersed in a metal substrate, a mechanical alloying treatment is performed on the metal powder for substrate and the metal powder for enhancing contact characteristics. In the method for producing a contact material, the sintered body is obtained by firing a molded body of alloy powder alloyed by A method for producing a contact material, which comprises using a powder obtained by mechanically alloying by adding a powder for improving property. 2. Of the total amount of the metal powder for the base material, the metal powder for strengthening the contact characteristics and the powder for improving the sinterability of 100 wt%, the metal powder for strengthening the contact characteristics is 1 to 20 wt%, The method for producing a contact material according to claim 1, wherein the powder for improving the binding property is 0.1 to 5 wt% and the balance is a metal powder for a base material. 3. The base metal powder is silver powder, the contact property enhancing metal powder is nickel powder and / or iron powder, and the sinterability improving powder is titanium powder and / or
Alternatively, the method for producing a contact material according to claim 1 or 2, which is a tungsten powder. 4. The mechanical alloying treatment is performed so that the metal powder for the base material, the metal powder for strengthening the contact characteristics, and the powder for improving the sinterability are in a solid solution similar state. A method for producing the contact material described. 5. The mechanical alloying treatment is carried out by using a ball mill with the amount of balls being 50 to 200 times the total weight of the metal powder for strengthening contact characteristics and the powder for improving sinterability. 5. The method for manufacturing the contact material according to any one of 1 to 4.