JPS589135B2 - Method for producing graphite-dispersed aluminum or aluminum alloy and method for producing graphite-dispersed metal or alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing graphite-dispersed aluminum or aluminum alloys and 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, the powder that can be used in this method is limited to fine powder, and since it takes a long time to inject the graphite, the graphite floats frequently, making it difficult to uniformly disperse the powder, resulting in poor productivity.

Conventionally, carbon and graphite materials have been used in rubbo for melting metals, and since they hardly dissolve in each other with metals, it is not possible to directly introduce graphite particles into molten metal and disperse them. As shown in Japanese Patent Publication No. 45-13224, this was impossible because graphite particles would float to the surface of the molten metal or alloy due to the difference in specific gravity.

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

It is desired to develop a casting technology that allows graphite particles to be dispersed without floating by a simple operation of adding graphite particles to a melt of metal or alloy and stirring the melt, and containing a large amount of graphite particles. .

The object of the present invention is to uniformly introduce graphite particles into a molten metal or alloy without using a carrier gas, without coating the graphite particles with metal, and without adding any carbide-forming elements to disperse the graphite particles. It is an object of the present invention to provide a method for manufacturing a solidified graphite-dispersed metal or alloy at low cost and reliably through a small number of steps.

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 the melt are dispersed in a melt of a metal or alloy that is not compatible with graphite from a metallurgical point of view. A method for producing graphite-containing alloys (Japanese Unexamined Patent Publication No. 45603/1983) has been proposed, which is characterized by solidifying the material.

Subsequently, as a result of further investigation, it was found that at least one of the carbide-forming elements titanium, chromium magnesium, zirconium, and phosphorus, which are wetting agents with graphite, even without metal coating.
The researchers succeeded in dispersing graphite particles in a molten metal containing 100% carbon dioxide, and then solidifying the molten metal.

However, although the high cost of metal coating can 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 it is said that the floated graphite cannot be redispersed. Despite the addition, the dispersion method remained unreliable.

A similar situation was observed when the metal-coated graphite powder was contained in an amount of 5% by volume or more.

That is, the speed at which the graphite particles floated to the surface of the molten metal was extremely fast, and they floated to the surface in an instant, and the floated graphite powder could not be dispersed again by stirring.

When adding titanium, which is the most effective of the carbide-forming elements, if the amount added is large, it will segregate outside the vicinity of the graphite particles, so when applied to sliding materials, current collector materials, etc. It is undesirable to add too much because it causes a galling phenomenon (galling phenomenon) and a deterioration of current collection characteristics in a relatively large current region, as it may cause problems in characteristics.

In order to solve the above-mentioned problems, the present inventor discovered that when graphite particles are introduced and dispersed into molten metal, the reason why the graphite particles float to the surface of the molten metal is that the graphite particles and the molten metal do not get wet. has reached a state where it is covered with something that prevents it from coming into contact with the molten metal, but if a substance that forms an obstruction is present or formed in the molten metal or in the environment, the formed substance I thought it was for a reason.

As a result of various studies, the present inventor found that there is a state in which substantially no gas, oil, etc. is adsorbed on the surface of graphite particles, and a state in which substantially no gas, oil, fat, oxides, etc. are adsorbed on the surface of the graphite particles, and a state in which there is substantially no adsorption of gas, oil, fat, or oxides in the melt. After maintaining the graphite particles in a non-forming state,
It has been found that if the graphite powder is added and stirred at a temperature in the range of 1300° C., graphite powder can be easily dispersed in the molten aluminum metal or aluminum alloy in an amount that causes the flowability of the molten metal to be lost by simply stirring and mixing the molten metal.

When introducing and dispersing reduction-cleaned graphite particles into a melt whose surface is maintained in a non-oxidizing or reducing atmosphere, large-scale equipment and troublesome work are required to carry out the process in the absence of any oxygen. In contrast, the present invention provides a method in which graphite particles can be dispersed in a melt even in the presence of some oxygen.

That is, when graphite particles are introduced into molten aluminum (Al), oxygen in the air that was initially attached or adsorbed to the graphite particles reacts with the Al, forming a γ phase around the graphite particles that inhibits wetting with the Al. Aluminum oxide (Al2O3) is generated, but if the temperature of the melt is increased to 850℃ or higher, γ-Al2
O3 is transferred to α-Al2O3.

During this phase transition, Al2O3 contracts and α-Al2O3
is separated from the graphite and settles to the bottom of the melt.

The surfaces of the graphite particles released from the γ-Al2O3 coating react with the molten Al, and are covered with aluminum carbide (Al2O3), which has good wettability with Al, and are dispersed in the melt.

During the melting process, molten Al also generates γ-Al2O3 on the surface of the melt due to oxides on the surface, air existing near the surface, etc., and some of it gets caught up in the graphite particles that are thrown into the melt and enters the melt. , some of it remains on the surface of the melt, but the temperature is 850℃
If the temperature exceeds that level, it transforms into α-Al2O3 and sinks into the melt.

The present invention maintains a melt of aluminum or an aluminum alloy in a state substantially free from contamination and generation of gas, oil, fat, oxides, etc., and maintains a melting temperature of the melt at 850 to 1300°C.
A method for producing graphite-dispersed aluminum or aluminum alloy, which comprises dispersing graphite particles in a state in which gas, oil, etc. are not substantially adsorbed or attached to their surfaces, and then solidifying the molten material. The molten aluminum alloy is maintained in a state where there is substantially no contamination or generation of gas, oil, fat, oxides, etc., the melting temperature of the melt is set at 850 to 1300°C, and the graphite particles are coated with gas, oil, etc. on the surface. A method for producing graphite-dispersed aluminum metal or aluminum alloy, and melting of aluminum or aluminum alloy, characterized by dispersing it in a state where it is not substantially adsorbed or attached, then adding an additive, melting it, and solidifying it. The melting temperature of the molten material is kept at 8.0
At a temperature of 50 to 1300°C, graphite particles are exposed to a gas on their surface.
Graphite-dispersed aluminum or aluminum alloy, which is obtained by dispersing in a state where oils and fats are not substantially adsorbed or attached, and then solidifying the molten material, can be optionally added to a molten metal or alloy that is not compatible with graphite from a metallurgical perspective. The present invention relates to a method for producing graphite-dispersed metals or alloys, which comprises melting a graphite-dispersed metal or alloy with the following composition and then solidifying it.

To summarize, the first invention is a method of dispersing graphite in aluminum or an aluminum alloy, and the second invention is a method of adding additives to the graphite-dispersed aluminum or molten aluminum alloy obtained by the first invention. ,
The third invention is a method of dispersing the graphite-dispersed aluminum or aluminum alloy in a metal or a molten metal.

The metal or alloy melt usually consists of materials that are metallurgically incompatible with graphite.

This metal or alloy melt mainly consists of aluminum, magnesium, nickel, copper, silicon, zinc lead, tin, and alloys based on these.

The solubility of graphite in melts of these metals or alloys is said to be extremely low, in fact less than 0.005% by weight, and these metals or alloys are generally said to be metallurgically incompatible with graphite. ing.

In order for the graphite particles to be dispersed in the melt, the melting temperature of the melt is extremely important.

In the present invention, the melting temperature of the melt is adjusted to the Al2O3 coating (γ
- 850 to 1300 of the combustion extinction start temperature of Al2O3)
The range was ℃.

If the temperature is lower than 850°C, graphite floats to the surface of the molten metal due to the influence of the γ-Al2O3 coating, which inhibits the wettability of aluminum and graphite.

In addition, it is not a good idea to raise the temperature of the molten alloy above 1,300° C., since it becomes susceptible to gas absorption and the integrity of the solidified ingot is impaired.

In the present invention, aluminum, magnesium, nickel, copper, silicon, zinc, lead, tin, and alloys mainly composed of these are used as the metal or alloy melt.

In addition, as a method of solidifying the molten metal, 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 the metal. There are no particular restrictions on the method of cooling and solidifying.

In addition, in order to make the surface of graphite particles substantially free from adsorption and adhesion of gases, oils, and other substances, for example, graphite particles of high purity should be used and they should be exposed to a hydrogen gas atmosphere. It is subjected to reduction treatment and then vacuum sealed.

In order to make the molten metal or alloy substantially free of contamination and generation of gases, oils, fats, oxides, etc., use high-purity metals or alloys as described above, and apply degreasing and cleaning solvents. After washing by immersion in the argon gas atmosphere and completely drying in an argon gas atmosphere, dissolution is also performed in the argon gas atmosphere.

Furthermore, in the present invention, additives include necessary elements other than the melt, such as Cu, Zn, Sn, Pb, Mn, Si, P
, Ni, Fe, Mg, Ag, Bi, Sb and Ti, Zr
, Hf, V, Nb, Ta, Mo, Co, and other interstitial carbide forming elements and their alloy compounds are used.

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%
The ash content (ash content: 3.0% or less, volatile content: 10% or less) was reduced at approximately 500° C. for 2 hours in a hydrogen gas atmosphere, then cooled and vacuum sealed.

On the other hand, after degreasing and cleaning an aluminum base metal (JIS H 2102 Special Class 1), it was heated at 200°C in an argon gas atmosphere.
A graphite Lupo (diameter 80 mm x length 26
0 mm) and dissolved.

Next, this molten metal was maintained at 850 to 1300°C, and the graphite particles described above were added at a constant stirring speed of 200 revolutions (r.p.m.) at an addition rate of 75 g/min.

The amount of graphite added to 1500 g of aluminum ingot was varied in the four ranges shown in Table 1.

*Calculated as Al: 2.6 g/cm3 and graphite: 2.2 g/cm3.

As a result, the entire amount of graphite particles introduced was dispersed in the molten metal,
It did not float to the surface of the molten metal.

When pouring these graphite dispersed molten metals into a mold and casting, A4
When 300 g (19.65% by volume) of graphite was added, the flow of the melt was poor and the melt became a paste that did not naturally flow out even if the crucible was tilted or turned upside down, but graphite particles did not float.

Therefore, in the case where graphite particles were dispersed without being added to the pure aluminum molten metal, the amount of graphite particles added to maintain a pourable state was about 18% by volume of A3.

The graphite-dispersed molten metals A1 to A3 above 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 observing the longitudinal section, it was found that graphite was present from the bottom to the top of the ingot. The particles were almost uniformly dispersed.

A macro cross-sectional photograph of an A3 cast product among the obtained ingots is shown in FIG.

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

FIG. 2 shows a macro cross-sectional photograph of a graphite-dispersed aluminum cast product obtained by this die-casting machine.

In each case, the black spots 1 in the figures are graphite particles, and the other parts 2 are basic metals or alloys.

Example 2 The molten metal was cleaned to be completely free of oil and fat and heated to 1000±
The graphite particles obtained in Example 1 were charged into the molten metal in the same manner as in Example 1 while the temperature was maintained at 50°C without an argon gas atmosphere (metal vapor was generated in the air). Similar results to Example 1 were obtained.

In other words, if the graphite particles and metal have been purified, they can be dispersed even in the air.

Example 3 The graphite particles obtained in Example 1 were washed with a commercially available aluminum casting alloy ingot (AC8A) shown in Table 2 to a state free of oil and fat adhesion, and melted in the air to form a molten metal of 850 to 1300.
When the graphite particles were placed in a temperature of ℃, the graphite particles were dispersed without floating.

That is, 20% by weight (22.1%) of graphite particles was added to AC8A.
A graphite-containing aluminum alloy was obtained in which the graphite-containing aluminum alloy was dispersed (equal to volume %).

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.

Comparative Example 1 An attempt was made to inject and disperse the graphite particles obtained in Example 1 into a molten metal using cutting oil adhering to it. As a result, the cutting oil burned on the surface of the molten metal, and the introduced graphite floated to the surface of the molten metal. It happened.

Example 5 The graphite particles obtained in Example 1 were washed with a commercially available aluminum casting alloy ingot (AC8A) free of oil and fat, and dissolved in the air at 1000±50° C. Example 1
As a result of cooling and solidifying, AC
An ingot of graphite-dispersed aluminum alloy in which graphite particles were dispersed in 8A was obtained.

Next, the same amount of this ingot was poured into 500 g of molten copper and stirred and mixed. As a result, the graphite was dispersed without floating.

Example 6 When the graphite-dispersed molten metal obtained in Example 1 was poured into molten copper at the same ratio, the graphite was dispersed without floating.

Example 7 When the ingots obtained in Examples 5 and 6 were remelted and melted again, graphite particles were dispersed without floating on the surface of the molten metal.

Example 8 No. of Example 1 1~No. Metallic silicon, nickel, copper, magnesium, and titanium were sequentially added to the graphite-dispersed melt or pasty melt obtained in step 4, and were completely dissolved.

The amount added was intentionally 81.7Al-12Si-105Cu-
It was made to be 1.0Mg-1.75Ni-2.5Ti.

At this time, the graphite particles did not float up. The pasty melt of No. 4 was now ready for pouring.

Furthermore, graphite particles were added to the total weight ratio of 17.45% (20
As a result of adding an amount equal to (volume %), it dispersed without floating.

Torera no. 1~No. 4 (with the same blending composition) was 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 observing the longitudinal section, it was found that the bottom of the ingot was lower than the bottom of the ingot. Graphite particles were almost uniformly dispersed all the way to the top.

A cross-sectional macro photograph of the obtained ingot is shown in FIG.

In FIG. 3, black spots 1 are graphite particles, and other parts 2 are base metals or alloys.

A similar confirmation was also made when a prototype was made using a die-cast gun making machine.

Example 9 The graphite particles obtained in Example 1 were poured into a molten metal of 1000+50°C which had been cleaned from a commercially available aluminum casting alloy ingot (AC8A) and dissolved in the air. As a result, the graphite particles were It dispersed without surfacing.

2% by weight of titanium was added to the graphite-dispersed molten metal for the purpose of forming a titanium (titanium carbide) layer on the surface layer of the graphite particles.

As a result, a graphite-containing alloy was obtained in which 20% by weight of graphite particles were dispersed in an AC8A system coated with a titanium (titanium carbide) layer.

FIG. 4 shows a state in which titanium was not added, and FIG. 5 shows a state in which titanium was added.

Comparing the two, it was found that in the case of the one to which titanium was added, a titanium (titanium carbide) layer 4 was formed around the graphite, as shown in FIG.

In addition, in FIGS. 4 and 5, 3 is crystallized nickel.

Example 10 Even when the ingots obtained in Examples 8 and 9 were remelted and remelted, graphite particles were dispersed without floating on the surface of the molten metal.

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

What's more, the manufacturing method is a brilliant reversal of what was once declared to be impossible.

As shown in FIGS. 1 and 2, 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, it has become possible to freely create parts that have the self-lubricating properties of graphite added to metals or alloys, and are lightweight, have high strength and wear resistance, and are suitable for sliding contact mechanisms such as bearings, pistons, etc.
It is suitable for use in cylinders, gears, etc., and also has unique properties as an anti-vibration material, so it can also be used in audio equipment components, etc.

[Brief explanation of drawings]

Figure 1 is a cross-sectional macro photograph of an ingot obtained in Example 1 of the present invention, Figure 2 is a cross-sectional macro photograph of a graphite-dispersed aluminum cast product obtained by a die-casting machine, and Figure 3 is an example of the present invention. 8 is a cross-sectional macro photograph of the ingot obtained in Example 8, FIG. 4 is a microstructure photograph showing the surrounding area of graphite of the ingot without titanium addition obtained in Example 9, and FIG. 5 is a photograph of the structure obtained in Example 9. This is a photograph showing the structure around graphite in an ingot to which titanium has been added. Explanation of symbols 1...Graphite particles, 2...Base metal or alloy, 3...Crystallized nickel, 4...Titanium (titanium carbide) layer.

Claims (1)

[Scope of Claims] 1 A melt of aluminum or an aluminum alloy is maintained in a state substantially free from contamination and generation of gas, oil, fat, oxides, etc., and the melting temperature of the melt is set at 850 to 1300°C, and graphite particles are A method for producing graphite-dispersed aluminum or aluminum alloy, which comprises dispersing graphite in a state in which gas, oil, etc. are not substantially adsorbed or attached to its surface, and then solidifying the melt. 2 The melt of aluminum or aluminum alloy is maintained in a state substantially free from contamination and generation of gas, oil, fat, oxides, etc., the melting temperature of the melt is set at 850 to 1300°C, and graphite particles are coated on the surface with gas, 1. A method for producing graphite-dispersed aluminum or an aluminum alloy, which comprises dispersing in a state in which oils and fats are not substantially adsorbed or attached, then adding additives, melting, and solidifying. 3 The melt of aluminum or aluminum alloy is maintained in a state substantially free from contamination and generation of gas, oil, fat, oxides, etc., the melting temperature of the melt is set at 850 to 1300°C, and graphite particles are coated on the surface with gas, Graphite-dispersed aluminum or aluminum alloy is dispersed in a state in which oils and fats are not substantially adsorbed or adhered, and then the molten material is solidified into a molten metal or alloy that is metallurgically incompatible with graphite. 1. A method for producing a graphite-dispersed metal or alloy, which comprises melting an arbitrary mixture and then solidifying it.