JPH02137662A - Production of fiber reinforced metallic parts - Google Patents

Abstract

PURPOSE:To prevent the generation of cracks which are the cause for the degradation of strength on the surface of a fiber molding by previously applying a sealing agent onto at least the part, which constitutes the product as it is, of the entire surface of the fiber molding in contact with a mold. CONSTITUTION:Ceramics fibers, such as alumina fibers, are first compressively molded to form the fiber molding 1 having the shape approximate to the shape of a piston at the time of producing, for example, the piston of an internal combustion engine. Curable silicone is then applied by dipping as the sealing agent on the surface, which is in contact with the metallic mold, on the inner side of the fiber molding 1, i.e., the surface in contact with the core mold 3, and thereafter, the silicone is dried to form a thin curable silicone layer 11. This fiber molding q is preheated to the temp. at which the curable silicone is not converted to ceramics. The heated molding is set in the core mold 3 of the metallic mold 2 of a high-pressure casting device. The molten metal of an Mg or Al alloy is immediately poured into the cavity 4 and is solidified while the molten metal is pressurized up to a prescribed pressure by a pressurizing punch 5. The required parts, such as the outer peripheral surface and peak surface, of the resulted molding are machined and piston ring grooves 6, etc., are machined thereto, by which the piston is completed in the final.

Description

[Detailed Description of the Invention] Industrial Field of Application This invention is a fiber reinforced technology in which aluminum alloys, magnesium alloys, etc. are reinforced with ceramic fibers. Therefore, these materials are used as a matrix metal, and ceramic fibers such as alumina, metal fibers, etc. are blended to form a fiber-reinforced metal composite material.

For example, fiber-reinforced metals with aluminum alloys or magnesium alloys as matrix metals are being used for internal combustion engine pistons, but the manufacturing method is to first compression-mold ceramic fibers such as alumina fibers, as shown in Figure 4. A fiber molded body 1 having a shape similar to that of a piston is formed as shown in FIG. Then, this fiber molded body 1 is set in a heated state in a mold 2 of a high-pressure casting apparatus, more specifically, in a core mold 3 thereof. Next, a molten aluminum alloy or magnesium alloy is poured into the cavity 4 of the mold 2, and is pressurized by a pressure punch 5 to solidify as it is.

As a result, a molded product that roughly follows the desired piston shape is obtained, so the necessary parts such as the outer peripheral surface and top surface are machined, and the piston ring groove 6 and other parts are machined as shown in FIG. Finally, the piston is completed (for example, Japanese Patent Laid-Open No. 133359/1983).

Problems to be Solved by the Invention For example, in the piston as described above, the inner surface thereof is not particularly machined, and the surface of the cast product becomes the product surface as it is. More specifically, this inner surface has a shape in which the surface of the fiber molded body I is exposed as it is.

However, in reality, when setting the fiber molded body l in the core mold 3, the molded body 1 and the mold surface do not completely match, and some gaps 7 are created, so the molten metal enters there and the final Specifically, a thin metal layer 8 (see FIG. 5) consisting only of matrix metal is formed on the surface of the fiber molded body 1, that is, the fiber-reinforced composite material portion.

This metal layer 8 is thin and naturally has low strength, so when the piston is used, cracks easily occur due to peeling at the interface with the fiber-reinforced metal layer, and these cracks further propagate to the fiber-reinforced metal layer. , there is a risk of reducing the strength of the entire piston.

Incidentally, even if a thin metal layer as described above is formed on the surface portion to be machined after casting, it will of course not make any difference to the number of ships.

Means for Solving the Problems Therefore, the present invention involves setting a fiber molded body made by molding fibers such as ceramics into a predetermined shape in a mold, pouring molten matrix metal into it, and molding it into one piece. In the method for manufacturing fiber-reinforced metal parts, a sealing agent such as hardening silicone or heat-resistant resin is applied in advance to at least a portion of the mold contacting surface of the fiber molded body that will become the product surface as it is. It is characterized by what it did.

Function: In the present invention, a pore sealant is applied to the fiber molded article before it is set in the mold. Since the surface of the fiber molded body is thinly covered with this sealant, even if there is some gap between the surface of the sealant layer and the mold surface, the fiber reinforced metal layer after molding will A metal layer consisting only of matrix metal does not adhere to the surface.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIG. 1.2.

In this embodiment, the present invention is applied to the production of a piston for an internal combustion engine, and first, ceramic fibers such as alumina fibers are compression-molded to form a fiber molded body l that approximates the shape of a piston. Next, curable silicone is applied as a sealant by dipping to the inner mold contacting surface of the fiber molded body 1, that is, the area in contact with the core mold 3, and dried to form a thin curable silicone layer 11. form.

Next, this fiber molded body 1 is preheated at a temperature at which the curable silicon does not turn into a ceramic, and is set in the mold 2 of an IT;77 pressure casting machine, specifically, in the core mold 3 thereof.

Immediately, molten magnesium alloy or aluminum alloy is poured into the cavity 4 and solidified while being pressurized to a predetermined pressure using a pressure punch 5.

Then, necessary parts such as the outer circumferential surface and the top surface of the obtained molded product are machined, and the piston ring grooves 6 and the like are machined, and finally a piston as shown in FIG. 2 is completed. Incidentally, the curable silicon layer 11 on the inner surface may be removed by suitable heat treatment or the like.

When the piston thus formed was cut and the composite state was inspected, no metal layer consisting only of matrix metal was observed on the inner surface that was in contact with the core mold 3.

That is, by applying a pore sealant such as curable silicone as described above, the adhesion with the core mold 3 can be improved.
1-C. It becomes difficult for the molten metal to enter into gaps. Moreover, even if there is a slight gap between the curable silicone layer 11 and the mold surface, since the surface of the fiber molded body 1 is sealed by the curable silicone layer 11, the adhesion of the matrix metal layer will be prevented. It will be blocked.

Next, FIG. 3 shows an example in which a relatively shallow undercut portion 12 is provided on the inner surface of the fiber molded body I in contact with the core mold 3.

In this case, by applying a sealant such as curable silicone to the inner surface of the fiber molded body 1, the undercut portion 12 becomes substantially flat or has a weakened unevenness.

As the core mold 3, one having a shape without an undercut portion is used.

When the molten metal is poured and pressurized in this way, the molten metal penetrates only into the fiber molded body l at the undercut portion 12, and the curable silicone layer 11 prevents it from leaking to the core mold 3 side. Therefore, an undercut shape that conforms to the molded shape of the fiber molded body 1 can be reliably obtained.

That is, it is possible to easily form an undercut shape without using a divided core mold.

It goes without saying that this invention can be applied to the manufacture of various fiber-reinforced metal parts other than the above-mentioned piston.

Effects of the Invention As is clear from the above explanation, according to the method for manufacturing fiber-reinforced metal parts according to the present invention, a thin metal layer made only of matrix metal is formed on the surface of the fiber molded article, that is, the surface of the fiber-reinforced metal layer. Never. Therefore, it is possible to prevent the occurrence of cracks that cause a decrease in strength.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of the manufacturing method according to the present invention, Fig. 2 is a cross-sectional view of a piston manufactured by this manufacturing method, and Fig. 3 shows an example in which the piston has an undercut portion. FIG. 4 is an explanatory diagram showing a conventional manufacturing method, and FIG. 5 is a sectional view of a conventional piston produced by this manufacturing method. DESCRIPTION OF SYMBOLS 1... Fiber molded object, 3... Core mold, 11... Curable silicone layer.

Claims (1)

[Claims] (1) Manufacture of fiber-reinforced metal parts in which a fiber molded body made by molding ceramic fibers into a predetermined shape is set in a mold, and molten matrix metal is poured into the molded body and molded into one piece. A method for manufacturing a fiber-reinforced metal component, characterized in that a pore sealant is applied in advance to at least a portion of the mold contacting surface of the fiber molded body that will become the product surface as it is.