JPS642178B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses an inorganic short fiber material as a reinforcing material, and uses aluminum or an aluminum alloy (hereinafter referred to as
It's called aluminum. ) and relates to a method for producing a fiber-reinforced aluminum composite molded body. Recently, composite materials in which inorganic short fiber materials such as carbon, silicon carbide, and alumina are used as reinforcing materials and are dispersed in aluminum as a matrix material have been developed with excellent mechanical properties at high temperatures. Attempts have been made to use it in components that require high-temperature properties, such as internal combustion engines. Conventionally, as a method for compositely dispersing such an inorganic short fiber material in aluminum as a matrix material, a method of stirring and mixing the fiber material into molten aluminum has been known. In this case, there is a quantitative restriction on the amount of fibers that can be mixed into the molten metal, and especially when using fibers that are difficult to wet with the molten aluminum, the fibers tend to be locally unevenly distributed and cannot be distributed evenly. It was difficult to obtain a composite material in which a large amount of fiber material was dispersed. Furthermore, Japanese Patent Application Laid-Open No. 59-43835 discloses that a precursor is formed by bringing silicon carbide whiskers into contact with a matrix metal at a temperature of 800°C or higher, and the precursor is placed in the hot water of the matrix metal while remaining in the form of a lump. A method for manufacturing a composite material is disclosed in which the material is stirred and dispersed to form an ingot. With this method, a composite material containing fibers dispersed relatively uniformly can be obtained.
Molten metal containing fibrous materials uniformly dispersed in this manner has a lower fluidity as the fiber concentration increases, making it difficult to cast the mixed molten metal. Furthermore, the composite ingot produced in this way has poor plastic workability, and therefore it is quite difficult to stretch the cast body cast in the form of a billet or slab by extrusion or rolling. It was difficult. The present inventors first centrifugally mixed an inorganic short fiber material into molten aluminum, granulated the mixture appropriately, and then compression-molded the composite granular material while heating it to a molten or semi-molten state. As a result, we succeeded in obtaining an aluminum composite molded body in which a relatively large amount of inorganic short fiber material was uniformly dispersed. (Patent Application No. 58-50504) The compression molded product produced by the above method has excellent mechanical properties even in its original state, so it can be used directly as a molded product such as a machine part. Composite bodies compressed into billet or slab shapes can be subjected to hot plastic processing such as extrusion and rolling, and can be processed into extruded or rolled materials and used in a wide range of fields. It was hot. However, the above conventional method still has the following drawbacks. (1) The molding method of the composite molded body in the above conventional method is as follows:
Composite granules consisting of short fiber material as a reinforcing material and aluminum as a matrix material are heated as they are in a molten or semi-molten state in a mold, and then compression molded using direct mechanical force. However, using such a molding method not only causes various difficulties in the molding process, but also requires strong pressure to obtain a molded product with few internal defects, and it is difficult to mold a complex shape. It was difficult to get a body. (2) The plastic workability of the molded product obtained as described above is not necessarily good, and there are still problems with workability when extruding or rolling the molded product formed into a billet or slab shape. It was something to leave behind. In order to improve the above-mentioned drawbacks of the conventional method, the present inventors conducted further research and found that composite granules of aluminum and fiber material produced in the same manner as in the conventional method were further heated. When mixed into another molten aluminum, the mixed molten material can be easily cast into a mold to form a shaped body by a method similar to that in ordinary gravity casting, and The resulting molded product has much better plastic workability than the composite molded product obtained by the conventional method, and the wrought material obtained by plastic working has better plastic workability than the composite molded product obtained by the conventional method. I found that it was comparable in comparison. The present invention has been made based on the above findings. That is, the present invention mixes an inorganic short fiber material in molten aluminum, granulates this mixture into particles with a diameter of several mm or less, mixes the resulting composite granules into separately heated molten aluminum, and This is a method for producing a fiber-reinforced aluminum composite molded body, in which a mixed melt is cast in a mold and then subjected to plastic working. Next, the present invention will be explained in more detail. In the method of the present invention, first, an inorganic short fiber material as a reinforcing material is mixed into molten aluminum as a matrix material, and this mixture is granulated to temporarily form composite granules. As the aluminum material, 1000 series industrial ordinary aluminum, 4000 series aluminum alloy for casting, etc. can be used as appropriate. Also,
Heat-treated wrought alloys such as 6000 series and 7000 series may also be used. As the fiber material, carbon fibers, silicon carbide fibers, alumina, and other appropriate inorganic short fiber materials can be used. These fiber materials have a length of 10~
It is appropriate to use a material with a thickness of about 500μ. The mixing ratio of the fiber material to the molten aluminum can be appropriately selected depending on the use of the composite material to be manufactured. Generally speaking, in order to exhibit sufficient mechanical strength, it is desirable to mix the fibrous material to the granules at a mixing ratio of about 10 to 40% by volume. As for the mixing method, if the proportion of the fiber material to be mixed is relatively small compared to the molten aluminum, it can be mixed by mechanical stirring into the molten aluminum. When using fiber materials that are difficult to wet with molten metal,
When mixing a relatively large amount of fibrous material with molten aluminum, a centrifugal device is used to sufficiently infiltrate the molten aluminum into the gaps between the fibrous materials and evenly disperse the fibrous materials into the molten metal. It is preferable to mix using centrifugal pressure. By such a method, the molten aluminum sufficiently penetrates into the gaps between the fibrous materials, and it is possible to obtain a mixture that has good adhesion and contains a large amount of fibrous materials evenly distributed. Next, the mixture obtained as described above is granulated, and if the density of the fibers contained in the mixture is relatively low, this granulation can be carried out using known methods for producing aluminum grains, for example, The molten mixture can be flowed down onto a rapidly rotating disk and shaken off by centrifugal force to form granules, but when the fiber content density in the mixture is high and the viscosity of the molten mixture is high, Since the molten material exhibits almost no fluidity, the solidified mixture may be left as is or heated to a soft state, and then crushed or ground using a crusher or impeller. It can be granulated by doing this. The preferred granularity is several mm or less, and more preferably the granularity is adjusted to about 0.1 to 3 mm. If the granularity of this mixed granular material of aluminum material and short fiber material is too large, the short fiber material will be loosened by slight stirring during mixing with molten aluminum in the next step, and will be distributed uniformly into the molten metal. Dispersion will significantly reduce the fluidity of the molten metal, and will also impair the plastic workability of the cast body.
It is desirable that the granularity does not exceed a diameter of several mm. Next, after mixing the fiber composite granules produced by the above steps into heated molten aluminum,
This mixed molten material is cast into billets, slabs, or other appropriately shaped molds. The same type of aluminum alloy may be used, or a different type of aluminum alloy may be used. The mixing ratio of the molten aluminum and the composite granules can be determined as appropriate depending on the intended use of the composite molded body, the density of the fibrous material contained in the granules, the size of the granules, and the like. Generally speaking, diameter 0.1 containing about 20 to 35% by volume of fiber material
When using granules of ~3 mm, the final molded product can be mixed in such a proportion that it contains about 2 to 15% by volume of fibrous material, resulting in casting that has favorable plastic workability and mechanical strength. You can get a body. The temperature of the molten aluminum is lowered by mixing the particulates. Therefore, by heating the molten metal to a high temperature in advance, or while heating it,
After mixing the aluminum granules composited with the short fiber material obtained in the previous step, gentle stirring is continued. By mixing, the primary aluminum matrix forming the granules becomes molten, which prevents the fibrous material within the granules from being dispersed into the secondary molten aluminum. In other words, it becomes a large number of fine aggregated particles that are uniformly distributed and suspended in the molten metal, while maintaining almost the same state as when they were confined within the granules. Next, the molten aluminum in which the fiber material is suspended is cast into a billet, slab, or other arbitrary shape mold. Casting can be performed in the same manner as normal gravity casting. During casting, it is preferable to solidify the molten metal under pressure in order to prevent the casting structure of the casting from becoming dense and the occurrence of casting defects. In the method of the present invention, the composite cast body obtained by casting as described above is subjected to plastic working.
This plastic working can be performed in the same manner as in hot extrusion, hot rolling, etc. of ordinary aluminum materials. The composite molded article of the present invention obtained by the above-mentioned plastic working exhibits excellent properties in terms of mechanical strength and wear resistance, and can be used in its original shape or, if necessary, by heat treatment or cutting. It can be processed, forged, etc. and used in a wide range of other mechanical parts. As described above, the present invention involves granulating a mixture of inorganic short fiber material and molten aluminum into fine particles with a diameter of several mm or less, mixing the granules into separately heated molten aluminum, and casting this mixture. As a result, the castability of the fiber-mixed molten metal is significantly improved, and the cast bodies thus obtained have much better plastic workability than those obtained by conventional methods. This invention makes it possible to efficiently mass-produce fiber-reinforced aluminum molded bodies, and can be said to be an invention of great industrial value. Next, examples of the method of the present invention are listed. Example 1 Using 2017Al alloy as the matrix material,
Alumina short fibers (diameter 3 μm x average length approximately 120 μm) were used as the inorganic short fiber reinforcing material. Alumina short fiber material containing 30% by volume of aluminum was placed in a centrifugal container, heated and molten aluminum was poured into the container, centrifugally mixed, and then the mixture was heated to 500°C and placed in a crusher ( The mixture was crushed using an attrition mill to obtain composite granules with a diameter of 0.1 to 3 mm. Molten aluminum (2017Al alloy) made by heating and melting 30 parts of the composite granules thus obtained at 750℃
After mixing and stirring for a while, 40 mm in diameter x
It was cast into a billet shape in a cylindrical mold with a length of 120 mm. The obtained composite casting was placed in a container of an extruder and hot extruded into a round bar shape with a diameter of 10 mm (temperature
450℃). (Sample A) Example 2 30 parts of the composite granules produced in the same manner as in Example 1 were converted into molten aluminum in the same manner as in Example 1 (however, 6061Al alloy molten metal was used). After stirring and mixing for a while, the mixture was poured into a billet shape into a cylindrical mold with a diameter of 40 mm and a length of 120 mm. The obtained composite cast body was extruded into a round bar shape with a diameter of 10 mm in the same manner as in Example 1. (Sample B). Example 3 30 parts of the composite granules produced in the same manner as in Example 1 were placed in 70 parts of molten aluminum (6061Al alloy was used) in the same manner as in Example 2, and after stirring and mixing for a while, It was pressure cast into a billet shape (pressure: 150 kg/cm ² ) in a cylindrical mold with a diameter of 40 mm and a length of 120 mm. The obtained composite cast body was extruded into a round bar shape with a diameter of 10 mm in the same manner as in Example 1. (Sample C) Example 4 20 parts of the composite granules produced in the same manner as in Example 1 were placed in 80 parts of molten aluminum (6061Al alloy) in the same manner as in Example 2, and after stirring and mixing for a while. As in Example 3, it was pressure cast into a billet shape with a diameter of 40 mm and a length of 120 mm. The obtained composite cast body was extruded into a round bar shape with a diameter of 10 mm in the same manner as in Example 1. (Sample D) Samples A, B, and C obtained in Examples 1 to 4
and D, the mechanical properties were measured at room temperature and high temperature, and the results were as shown in the following table.

[Table] The * mark in the table indicates the Okoshi method (speed 1.5m/S,
This is the wear loss at a distance of 66.6 m and a final load of 21 kg). The drawing is an enlarged longitudinal section photograph (magnification x 5) of Sample C. As can be seen from the figure, in the composite material obtained by the method of the present invention, the short fiber material as a reinforcing material is symmetrically bonded to the aluminum matrix material along the plastic working direction with good adhesion. It is contained in a distributed manner, thereby improving the mechanical strength of the composite material.

[Brief explanation of the drawing]

The figure is an enlarged cross-sectional photograph (magnification x 5) of a composite material obtained by the method of the present invention.

Claims (1)

[Claims] 1. Mix inorganic short fiber material in molten aluminum, granulate this mixture into granules of several mm or less, mix the resulting composite granules into separately heated molten aluminum, and prepare the fibrous material in the composite granules. Fiber-reinforced aluminum is produced by forming a large number of fine aggregate grains into a uniformly distributed and suspended state in the molten metal, casting this mixed melt in a mold, and then subjecting it to plastic working. Method for manufacturing a composite molded body.