JPS586772B2 - Manufacturing method of graphite dispersed metal or alloy - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing graphite-dispersed metals or alloys.

As a method for dispersing powder of a metallurgically incompatible substance in a molten metal or alloy, there is a method, for example, of suspending metal-coated graphite powder in a carrier gas and blowing it into the molten metal.

However, this method has the disadvantage of poor productivity because the powder that can be applied to this method is limited to fine powder, and because it takes a long time to inject the graphite, the graphite floats a lot and it is difficult to achieve uniform dispersion.

Conventionally, carbon and graphite materials have been used in crucibles for melting metals, and since they hardly dissolve in each other with metals, the method of directly introducing graphite particles into molten metal and dispersing them was disclosed in Japanese Patent Publication No. 1042/1983. As shown in Japanese Patent Publication No. 45-13224, graphite particles float to the surface of the molten metal or alloy due to the difference in specific gravity, so this was impossible.

Therefore, graphite-metal composites have only been applied in some parts of powder metallurgy technology.

A simple operation of adding graphite particles to a molten metal or alloy and stirring the molten material allows the graphite particles to be dispersed in the molten metal or alloy without floating them. Development of casting technology is desired.

The object of the present invention is to introduce graphite particles into a molten metal or alloy without using a carrier gas, without coating the graphite particles with metal, and without adding carbide-forming elements to disperse the graphite particles. The present invention provides a method for producing a solidified graphite-dispersed metal or alloy at low cost, reliably, and stably in a small number of steps after uniformly dispersing it.

In already proposed methods for producing graphite-dispersed metals or alloys, graphite particles are coated with a metal and blown into a molten metal with a dispersion gas.

These methods require complicated equipment and extra labor for the steps of introducing the dispersion gas and coating the graphite particles with metal, resulting in cost problems.

Furthermore, since it takes a long time to inject graphite, there are drawbacks such as non-uniform dispersion.

In order to solve the above problems, recently, graphite particles coated with a metal or alloy that is compatible with graphite are dispersed in a melt of a metal or alloy that is not compatible with graphite from a metallurgical perspective, and then the melt is solidified. A method for producing a graphite-containing alloy (Japanese Unexamined Patent Publication No. 45603/1983) has been proposed.

After further investigation, we discovered that titanium, chromium, which is a carbide-forming element that is a wetting agent for graphite without metal coating,
Graphite particles were successfully dispersed in a metal melt to which at least one of magnesium, silconium and hyrine was added, and the melt was subsequently solidified.

However, although the high cost of metal coating could be eliminated, for example, graphite particles introduced into a melt of aluminum metal or its alloy, which is easily oxidized, may float to the surface of the melt, and relatively expensive carbide-forming elements may be removed. Despite the addition, the dispersion method remained unreliable.

Moreover, when adding titanium, etc., which has the most remarkable effect among carbide-forming elements, if the amount added is large, it may cause so-called problems such as crushing, scraping, and adhesion of the other material when applied to sliding materials, current collector materials, etc. Since it may cause a staking phenomenon, it is not desirable to add it in excess because it may cause problems in properties.

Therefore, the present inventors have discovered that the graphite particles can be uniformly dispersed by dispersing graphite particles on which a non-metal coating has been formed into a molten metal or alloy, and then solidifying the molten metal.

In other words, due to oxygen in the air adsorbed on graphite particles,
In order to prevent the formation of γ-phase aluminum oxide that inhibits wetting of graphite particles with molten aluminum, graphite particles are immersed in an aqueous solution of aluminum phosphate, an aqueous solution of stannous chloride, etc., and the air adsorbed in the graphite particles is removed. The graphite particles are degassed and then heated to remove moisture, and the graphite particles are coated with powder of aluminum phosphate, stannous chloride, etc. to prevent adsorption of gases such as air.

When this graphite powder is poured into a molten aluminum metal or aluminum alloy, aluminum phosphate, stannous chloride, etc. are dispersed in the molten material, and the surface of the graphite particles reacts with the molten aluminum, resulting in carbonization with good wetting with the aluminum. It is coated with aluminum and dispersed in the melt.

The present invention involves dispersing graphite particles with a coating of aluminum phosphate, stannous chloride, or stannous chloride and palladium chloride on the surface in a melt of a metal or alloy that is metallurgically incompatible with graphite. , relates to a method for producing graphite-dispersed metals or alloys, characterized in that the melt is then solidified.

In the present invention, aluminum, magnesium, nickel, copper, silicon, zinc, lead, tin, and alloys mainly composed of these are used as the molten metal or alloy, but according to the method of the present invention, aluminum metal, etc. It is preferable to use aluminum-based cast alloy ingots commercially available as alloys and other alloys containing aluminum.

Methods for solidifying molten metal include pressure solidification casting, in which a die-casting machine is used, the graphite-dispersed molten metal is poured into it, and the plunger is immediately moved to pressurize and solidify it; or, it is poured into a mold and cooled. There are no particular restrictions on the method of coagulation.

Further, a coating other than metal can be formed on the surface of the graphite particles by treating the graphite particles with an aqueous solution of aluminum phosphate, an aqueous solution of stannous chloride in hydrochloric acid, or an aqueous solution of palladium chloride in hydrochloric acid.

When treating graphite particles with aluminum phosphate, commercially available graphite powder is poured into, for example, a 10% aqueous aluminum phosphate solution and stirred, the precipitated graphite particles are collected and heated at about 200°C for 2 hours. Dry conditions are sufficient.

In addition, when treating graphite particles with an aqueous solution of stannous chloride in hydrochloric acid or further with an aqueous solution of palladium chloride in hydrochloric acid, commercially available graphite particles are treated with 100 g/l of stannous chloride and 10 g/l of concentrated hydrochloric acid.
The graphite particles were poured into an aqueous solution of stannous chloride and hydrochloric acid having a composition of 0 ml/l, stirred and mixed, and the precipitated graphite particles were collected and heated at approximately 200°C.
Although it is sufficient to dry it in a dry state, dispersion becomes easier if it is further treated in the same manner as the former in an aqueous solution of palladium chloride and hydrochloric acid having a composition of 0.2 to 0.5 g/l of palladium chloride and 5 ml/l of concentrated hydrochloric acid.

However, except in special cases, only the former process is more economical in terms of cost.

Furthermore, there are no particular limitations on the thickness or amount of coating obtained by these treatments.

The present invention will be explained below with reference to Examples.

This example is not intended to limit the invention.

Example 1 50-1000 μm flaky graphite (fixed carbon 96.0%
or more, ash content 3.0% or less, volatile content 1.0% or less) 10
% aluminum phosphate aqueous solution, and then stirred and mixed. The precipitated graphite particles were collected and dried for 2 hours in a dryer kept at 200°C. Next, they were poured into molten aluminum metal and stirred. Mix and disperse.

The temperature of the molten metal was maintained at 700°C.

The amount of graphite particles added was within the range shown in Table 1 per 1.500 g of aluminum metal.

As a result, the entire amount of graphite particles introduced was dispersed in the molten metal, and no floating was observed.

When pouring these graphite-dispersed molten metals into a mold and casting them, if 300g (19.65% by volume) of A4 graphite was added, the flow of the molten metal would be poor, and the molten metal would not naturally flow out even if the crucible was tilted or turned upside down. However, the graphite particles did not float.

Therefore, when graphite particles are added and dispersed in pure aluminum metal molten metal, the amount of graphite particles added to maintain the pourable state in the molten metal is No. The amount was about 18% by volume of 3.

Graphite-dispersed molten metals A1 to A3 were poured into a mold, and then cooled and solidified to produce an ingot with a diameter of 100 mm and a length of 50 mm. When the longitudinal section was observed, graphite particles were observed from the bottom to the top of the ingot. were almost evenly distributed.

Similar confirmation was also made when a prototype was produced using a die-casting machine.

FIG. 1 shows a macro cross-sectional photograph of a graphite-dispersed aluminum cast product obtained by this die-casting machine.

Example 2 The same procedure as in Example 1 was carried out except that the temperature of the molten metal was raised to about 1200° C., and the same results as in Example 1 were obtained.

Example 3 Graphite particles obtained in the same manner as in Example 1 were poured into a commercially available molten aluminum casting alloy (AC8A) shown in Table 2 and stirred and mixed. As a result, the graphite particles were dispersed without floating. did.

That is, a graphite-dispersed alloy was obtained in which 20% by weight of graphite particles were dispersed in AC8A.

Example 4 Even when the ingots obtained in Examples 1 to 3 were remelted and melted again, graphite particles were dispersed without floating on the surface of the molten metal.

Example 5 The flaky graphite of 50 to 1000 μm used in Example 1 was put into a stannous chloride hydrochloric acid aqueous solution having a composition of 100 g/l of stannous chloride and 100 ml/l of concentrated hydrochloric acid, then stirred and mixed, and allowed to settle. Collect and wash the graphite particles with water.

Then palladium chloride 0.2-0.5 g/l, concentrated hydrochloric acid 5
Palladium chloride was stirred and mixed in an aqueous solution of hydrochloric acid having a composition of ml/l, and the precipitated graphite particles were collected and washed with water at 200°C.
It was dried for 2 hours.

Stirring and mixing in each aqueous hydrochloric acid solution was carried out at 200 revolutions (rpm) for 2 minutes, and washing with water was carried out in an amount 5 times the amount of the treatment solution used.

The graphite particles thus obtained were poured into molten aluminum metal and dispersed by stirring and mixing.

The temperature of the molten metal was maintained at 700°C.

The amount of graphite particles added was the same as in Example 1.

As a result, the same results as in Example 1 were obtained.

Example 6 Example 5 was carried out in the range where the temperature of the molten metal was increased to approximately 1200°C.
As a result, the same results as in Example 5 were obtained.

Example 7 A stannous chloride hydrochloric acid aqueous solution having a composition of 200 f/l of stannous chloride and 200 ml/l of concentrated hydrochloric acid was poured into a pre-weighed graphite particle container, mixed and stirred, and the graphite particles settled. Take a fraction and wash with water in 5 times the volume of the treated solution at 1200℃ for 2
Dry for an hour.

Stirring and mixing were performed at 200 revolutions (rpm) for 2 minutes.

The graphite particles thus obtained were put into a molten aluminum metal, stirred and mixed in the same manner as in Example 5, and the same results as in Example 5 were obtained.

Example 8 The graphite particles obtained in Example 5 and Example 7 were
Commercially available aluminum casting alloy ingots (A
C8A) When the graphite particles were poured into the molten metal and stirred and mixed, the graphite particles were dispersed without floating.

That is, a graphite-dispersed alloy was obtained in which 20% by weight of graphite particles were dispersed in AC8A.

Example 9 Even when the ingots obtained in Examples 5 to 8 were remelted and remelted, graphite particles were dispersed without floating on the surface of the molten metal.

According to the present invention, graphite-dispersed metals or alloys can be produced reliably and at low cost.

Further, as shown in FIG. 1, graphite particles are obtained in a uniformly dispersed state, and even if the ingot is remelted and melted again, the graphite particles can be dispersed without floating.

Therefore, the self-lubricating property of graphite is imparted to metals, alloys, etc., and it is lightweight, has high strength, and has wear resistance, making it suitable for use in sliding contact mechanism elements such as bearings, pistons, cylinders, gears, etc. On the other hand, it also has unique properties as an anti-vibration material, and can also be used for audio equipment components.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional macro photograph of a graphite-dispersed aluminum casting obtained in Example 1 of the present invention.

Claims (1)

[Claims] 1. Graphite particles with a coating of aluminum phosphate, stannous chloride, or stannous chloride and palladium chloride formed on the surface are dispersed in a melt of a metal or alloy that is metallurgically incompatible with graphite, and then A method for producing a graphite-dispersed metal or alloy, which comprises solidifying a molten material.