JPS6410581B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention uses an inorganic short fiber material as a reinforcing material, and uses this as a matrix material of aluminum or an aluminum alloy (hereinafter referred to as aluminum).
The present invention relates to a method for manufacturing a composite cast body containing the present invention dispersed therein. Conventional technology Recently, composite materials in which carbon, silicon carbide, alumina, or other inorganic short fiber materials are used as reinforcing materials and are dispersed in aluminum as a matrix material have been developed. In addition, it has excellent mechanical strength and wear resistance, so
Attempts have been made to use it widely as various mechanical components. Conventionally, as a method for obtaining an aluminum cast body containing such a composite inorganic short fiber material, a method is known in which a short fiber material is filled in a mold and molten aluminum is mixed under pressure into the mold. However, in the cast bodies obtained in this manner, the fibrous material contained therein tends to be locally unevenly distributed, making it difficult to obtain a composite containing the fibrous materials evenly dispersed therein. Therefore, as described above, the solidified lump obtained by pressurizing and mixing molten aluminum with the fiber material is heated and remelted either as is or by adding molten aluminum to it, and then recast into a mold of the desired shape. There have also been attempts to do so. However, the molten metal obtained in this way contains a large amount of fiber material irregularly, so it has extremely poor flow and is difficult to cast into a mold with a complicated shape. Composite cast bodies are subject to their own limitations in terms of shape. The present inventors first crushed a solidified lump obtained by pressurizing and mixing molten aluminum with an inorganic short fiber material into fine particles, and then added the crushed particles secondarily. We proposed a method for manufacturing composite cast bodies in which aluminum is melted into molten metal and the molten metal is cast into molds of arbitrary shapes. (Patent Application No. 59-65690) The method of the above-mentioned Japanese Patent Application No. 59-65690 involves first crushing the composite coagulate of inorganic short fiber material and aluminum into fine particles, and then By remelting into the added molten aluminum,
This method improves the flow of the fiber-containing molten metal and facilitates recasting of the composite solidified material, but this method also has the following drawbacks:
However, there were the following drawbacks. That is, in this method, the composite solidified material obtained by pressurizing and mixing molten aluminum with inorganic short fiber material is strongly reinforced by a large amount of irregularly contained fiber material. Since it is solidified, it is extremely difficult to crush it, and it takes a considerable amount of time to industrially obtain a large amount of fine particles. Means for Solving the Problems As a result of further research in order to solve the problems in the above-mentioned conventional method, the inventors of the present invention discovered that a method of stirring and mixing an inorganic short fiber material as a reinforcing material in a container. Therefore, the fibrous materials can become entangled with each other and aggregate to form a large number of fine fluff-like agglomerated particles, and the molten metal obtained by mixing molten aluminum with the fibrous materials aggregated in the form of fluffs does not contain the fibrous materials. Compared to conventional molten metal containing irregularly contained materials, it has much better fluidity and can be easily cast into molds of arbitrary shapes, and the cast bodies cast in this way are comparable to conventional composite cast bodies. We have discovered a series of facts such as that it has much better plastic workability and can be easily made into a composite drawn material by extrusion or rolling. The present invention has been made based on the above findings. That is, in the present invention, an inorganic short fiber material is preliminarily formed into a large number of fluff-like aggregates, and the fiber mixed molten metal obtained by mixing the fiber aggregates with molten aluminum is used as it is or once solidified and then remelted, This is a method for manufacturing fiber-reinforced aluminum composite castings that can be cast into arbitrary shapes. The method of the present invention will be explained in more detail below. In the method of the present invention, the inorganic short fiber material used as a reinforcing material is first made into a large number of fluff-like aggregates, but the inorganic short fiber material used is:
Carbonaceous fibers, silicon carbide fibers, alumina fibers, and other appropriate fiber materials can be used. Agglomeration can be carried out by placing these fiber materials in a mixing container equipped with stirring blades, a rotary mixer, a V-type mixer, etc., and stirring and mixing them for a while. For example, if fibrous materials are placed in a small mixing container equipped with stirring blades and stirred for about 5 to 30 minutes, the fibrous materials in the container will be moderately cut and intertwined with each other, depending on the type of fibrous material. There is a difference in diameter from 0.1 to
A large number of fluff-like agglomerated particles with a particle size of about 3 mm are obtained. Regarding the length of the fiber material for agglomeration, commercially available short fiber materials containing relatively long fibers of about several centimeters can be used as they are, but the length of the fiber material for agglomeration is 1 cm or less, preferably about 0.1 to 1 cm. It is desirable to use a fibrous material whose grain size has been adjusted to shorten the time required for agglomeration and to obtain well-defined agglomerated particles. Agglomeration of the fiber material can be achieved by stirring the dry fiber material as it is, but it is possible to reduce the loss caused by the scattering of finely cut fiber materials caused by stirring and to shorten the time. In order to efficiently aggregate the fibers into green balls, it is desirable to sprinkle a small amount of water on the fibrous material and stir it while providing appropriate moisture to cause the flocculation. Furthermore, agglomeration can also be achieved by stirring the fibrous material in a state in which it is thickly suspended in a suitable dispersion medium such as water or a lower alcohol. Next, after drying the fluff-like fiber aggregates prepared as described above, if necessary, molten aluminum as a matrix material is mixed therein.
As the molten aluminum, 100 series industrial ordinary purity aluminum, 4000 series aluminum for casting, and other suitable alloy materials depending on the purpose can be used. Further, a 6000 series or 7000 series heat-treated alloy for drawing may also be used. In order to mix the molten aluminum into the fiber aggregates, it is desirable to apply pressure to the molten metal so that the molten aluminum sufficiently penetrates into the voids within the fiber granules. This pressurized mixing can also be performed by pressurizing the molten metal into the fiber particles housed in a container using a high-pressure press, but in order to sufficiently penetrate the molten metal into the fiber aggregates, a centrifugal device may be used. When mixing under centrifugal pressure, the molten aluminum can more easily penetrate into the inside of the fiber aggregates. The fiber content in the mixture of fiber agglomerates and molten aluminum obtained in this way is about 5 to 20% by volume, but the fiber agglomerates are kept in a compressed state and the molten metal is mixed under pressure. By this method, a mixed molten metal containing fibers at a high density of about 30% by volume can be obtained. When preparing such a mixed molten metal containing fiber particles at a high density, a small amount of extremely fine inorganic powder with a diameter of several μ or less, such as aluminum oxide, which does not easily react with molten aluminum, is added to the fiber agglomerated particles in advance. It is desirable to sprinkle the fiber particles with the molten metal in order to help uniformly disperse the fiber particles in the molten metal when the mixed molten metal is solidified and then remelted. Next, the molten metal mixed with the fluffy fiber agglomerated grains and molten aluminum obtained as described above is cast into a mold of an arbitrary shape. It is preferable to solidify the composite solidified mass once, re-melt it by heating, and then cast it, as this makes the casting operation easier and it is easier to obtain a well-balanced cast body. Remelting of the composite agglomerates can be done using external heat furnaces normally used for metal melting, but melting can be done more efficiently when using high frequency or low frequency induction furnaces. . The melting may be carried out in the form of the solidified lump as it is, or may be carried out by crushing the solidified lump into lumps and granules of an appropriate size, if necessary. During casting, it is desirable to add an appropriate amount of molten aluminum secondarily in order to adjust the content of fiber material in the molten metal to a concentration appropriate for the intended use of the cast body. The mixed molten metal of the fiber material and molten aluminum obtained as described above contains the short fiber material dispersed in the form of fluff-like aggregates, so the conventional fiber material is irregularly contained in the same shape. It has a much better flow than molten metal, and can be cast into a composite body of a desired shape by gravity casting, continuous water cooling casting, die casting, molten metal forging, or other appropriate methods. In addition, the billet or slab-shaped cast body cast by the method of the present invention has much better plastic workability than the conventional composite cast body containing irregular fiber materials, and has much better plastic workability than ordinary aluminum alloys. In the same manner as extrusion or rolling, the material can be easily hot-stretched to form a composite aluminum material in the form of a bar or plate reinforced with inorganic short fiber material. Effects of the Invention As described above, in the present invention, an inorganic short fiber material as a reinforcing material is prepared in advance as a large number of fluff-like aggregates, and molten aluminum is mixed under pressure with the molten metal, which is obtained by mixing the molten metal as it is, or Since this is a manufacturing method for composite cast bodies that is once solidified and then remelted and cast, it is possible to crush the composite solidified mass of fiber material and molten aluminum into fine granules as in Japanese Patent Application No. 59-65690. Therefore, compared to the method of Japanese Patent Application No. 59-65690, this method reduces production costs and facilitates industrial mass production. Compared to the molten metal used in conventional composite casting production, in which the molten metal is directly dispersed in the molten aluminum, it has far superior castability, and it is possible to easily cast castings with complex shapes. The cast body obtained by this process has excellent effects such as having plastic workability and being able to be easily subjected to complex stretching processing. Examples Next, examples of the method of the present invention are listed. Example 1 Using 2017Al alloy as the matrix material,
Alumina short fiber (diameter 3μ x length
0.1 to 1 cm) was used. The alumina fiber material from No. 2 was placed in a container with a capacity of 5 and equipped with stirring blades, and stirred and mixed for approximately 20 minutes until the average particle size was approximately
A large number of fluff-like aggregates of 0.6 mm were obtained. The above fiber aggregate particles (0.4 kg) were placed in a centrifugal container,
After adding 4 kg of heated molten aluminum alloy (A2017 alloy) to this and centrifugally mixing for about 15 minutes, the contents were solidified. The above solidified mass (4.4 kg) was placed in a graphite crucible and heated in an electric furnace.
After melting at 650°C and stirring thoroughly, it was cast into a billet shape with a diameter of 40 mm and a length of 120 mm using a mold. The billet-shaped composite cast body was hot extruded (450°C) to form a round bar with a diameter of 10 mm (Sample A). Example 2 Alumina fiber aggregates were prepared in the same manner as in Example 1. 5 g of fine alumina powder (average particle size: about 0.1 μm) was added to the fiber aggregate particles 20 and thoroughly sprinkled thereon. The above fiber agglomerates (0.4 kg) were placed in a centrifugal container, and molten aluminum alloy (A2017
After pouring 3.5 kg of molten aluminum (A2017 alloy) and mixing by centrifugation, the contents were added unsolidified into 3.5 kg of molten aluminum (A2017 alloy) prepared in advance, stirred thoroughly, and cast into a cylindrical mold. , diameter 40mm x length
A billet-shaped composite casting of 120 mm was obtained. The above composite cast body was hot extruded (450°C) into a round bar shape with a diameter of 10 mm. (Sample B) Example 3 Fiber aggregate particles prepared in the same manner as Example 1 0.4
kg and molten aluminum alloy (ADC12 alloy) 4 kg
The molten metal obtained by re-melting the centrifugal mixed solidified material at approximately 680℃ is cast into a 100mm vertical die casting machine using a 250T pressurized die casting machine.
It was injection molded into a flat plate with dimensions of 50 mm in width and 5 mm in thickness. By injection molding, the fiber agglomerates dispersed in the molten metal were loosened into single fibers to obtain a die-cast body in which the fibers were uniformly dispersed in the aluminum matrix. (Sample C) The mechanical properties of Samples A, B, and C obtained in Examples 1 to 3 were measured, and the results were as shown.

[Table] Quantity.

Claims (1)

[Claims] 1. The inorganic short fiber material is made into a large number of fluff-like aggregates in advance, and the fiber mixed molten metal obtained by mixing the fiber aggregates with molten aluminum is directly mixed.
Alternatively, a method for manufacturing a fiber-reinforced aluminum composite cast body, which is characterized in that it is once solidified, then remelted, and then cast into an arbitrary shape.