JPH0636977B2 - Method for producing fiber-reinforced metal composite material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improved method for producing fiber reinforced metal composites by pressure casting with whiskers as reinforcing material.

[Conventional technology]

Whiskers composed of acicular single crystals such as SiC, Si ₃ N ₄ or graphite are fibrous substances with outstanding physical properties in terms of specific strength, specific elastic modulus, heat resistance, chemical stability, etc. It is useful as a composite reinforcing material when a light metal represented by Al is used as a matrix.

Conventionally, a pressure casting method has been known as an effective means for producing a fiber-reinforced metal composite material using this type of whiskers. In the pressure casting method, as shown in FIG. 2, a preformed whisker aggregate preform 1 is placed inside a mold 2 as a fiber skeleton, and a molten metal 3 of a matrix metal is injected into this and then added by a plunger 4. It is impregnated and solidified inside the preform structure under pressure to form a composite, but the most important operational condition when adopting this method is to maintain the molten state of the matrix metal normally throughout the impregnation process. is there. When the molten metal cools during the impregnation process and solidification of the matrix metal occurs, smooth penetration into the preform structure is hindered and property defects such as cracking of the composite part, extreme shrinkage deformation of the composite, and heterogeneity of the composite structure occur. Will be given.

Further, in order to ensure smooth impregnation, a method of permeating molten metal along the direction of the arrow from the top surface and all side surfaces of the whisker preform has been used so far as shown in FIG. This causes a phenomenon in which a gas component stored inside the preform structure or a component deviation due to a certain reaction that occurs when the molten metal is impregnated is contained in the central portion of the composite, which causes a defect in the structure.

In consideration of the above matters, the applicant has already proposed a compounding method that sets a preform of a whisker in a preheated insertion mold and inserts it in the mold (Japanese Patent Application No. 60 -281982).

[Problems to be solved by the invention]

According to the composite method of the above-mentioned prior application, since the molten metal impregnation is performed with the preform of the whisker set in the preheated insertion mold, the heat retention in the system can be sufficiently maintained throughout the impregnation process. The molten metal of the matrix metal unidirectionally permeates from the upper surface of the whisker preform and can push the stored gas components existing inside the preform structure and the reactive foreign substances that cause the component deviation into the bottom part, resulting in the structure as a whole. There is an effect that a composite with few abnormalities can be obtained.

However, with this method, the stored gas component and reactive foreign matter pushed to the bottom cannot be completely discharged out of the system,
In many cases, it solidifies at the bottom while remaining in a layered form. Therefore, it is necessary to excise this abnormal tissue portion, which causes problems such as difficult processing, size reduction, and shape change.

[Means for solving problems]

The present invention has been made for the purpose of improving the problems of the above-mentioned prior art, and the method for producing a fiber-reinforced metal composite material provided is to dispose whisker preforms in a mold as a fiber skeleton. When the molten metal of the matrix metal is injected and compounded by the pressure casting method, the molten metal of the matrix metal is preformed by setting the preform of the whisker in a preheated insertion mold and inserting it in the mold. It is structurally characterized in that it is unidirectionally press-fitted from the upper surface, and a part of the molten metal that flows down while being filled in the structure of the preform is forced out of the system through the pores of the pedestal board.

Hereinafter, the present invention will be described in detail with reference to the explanatory view of FIG.

First, the whisker preform 1 that serves as the fiber skeleton is set in the preheated insertion mold 5. The whisker preform is a short fiber aggregate formed by dismantling the generated whiskers such as SiC, Si ₃ N ₄ or graphite, and then shaped by a dry or wet method, and has an outer shape that matches the inner surface shape of the insertion mold 5. It is formed. The inner insertion mold 5 is made of a hard metal having excellent thermal conductivity such as tool steel, the inner surface is formed to follow the final shape such as a cylinder, an inverted cone or a groove with concave and convex, and the outer surface is a mold at the time of insertion. It is designed and processed into an integral or split type structure so as to be in close contact with the inner wall of 2.

The insertion mold 5 is heated by using an electric furnace or the like before being put into the mold 2, and is preferably preheated to the melting point of the matrix metal or higher. It is effective to preheat the preform 1 of the whisker to be set at the same time. For this purpose, it is operably convenient to preheat the preform of the whisker in a state of being set in the insertion mold.

At this time, it is possible to control the degree of shrinkage in the vertical direction of the composite material by adjusting the preheating temperature of the insertion mold and the preform, and thus the fiber volume ratio (Vf) can be determined by calibrating in advance. It can be adjusted appropriately.

Insertion mold 5 with whisker preform 1 set
Is then attached to the upper part of the pedestal board 6 arranged in the mold 2. The pedestal board 6 is provided with a plurality of pores 7 penetrating vertically and has a structure in which a cavity 8 for the molten metal reservoir is formed between the pedestal board 6 and the press bottom board. Throughout the impregnation process, the mold is entirely heated by the attached heating device.

Subsequently, the melt 3 of the matrix metal is poured into the mold, and the plunger 4 pressurizes the melt from above. By pressurization, the molten metal 3 permeates in the direction of the arrow only from the upper surface of the whisker preform 1, flows down while filling the inside of the preform structure, and is extruded from the pores 7 of the pedestal board 6 to the space 8. Molten metal 3 is empty 8
And then the matrix metal is solidified while maintaining a predetermined pressure.

[Work]

According to the above-mentioned manufacturing method, the molten metal of the matrix metal unidirectionally permeates from the upper surface of the whisker preform to push down the stored gas components and reactive foreign matters existing inside the preform structure to the bottom, and finally the pores 7 Is squeezed out into the void 8 outside the system. This action and the sufficient heat retaining action by the insert mold work together to form a composite state without tissue abnormality.

〔Example〕

Diameter 0.5-1.5μm, length 60-100μm, density 3.18g /
cm ³ , SiC whiskers having crystal form β type properties are well solved and then dispersed in pure water to form a wet whisker cake by a pressurizing method, followed by heat drying to a diameter of 80 mm,
A cylindrical preform having a height of 140 mm and a fiber volume ratio (Vf) of 15% was prepared.

The above SiC whisker preform has an inner diameter of 80 mm,
Insert and set in the tool steel (SK material) inner insertion mold with an outer diameter of 120 mm and a height of 140 mm, and put it in an electric furnace at 730 ° C.
Preheated to. Then insert the preheated insert mold into the upper part of the bottom cavity type pedestal (height 10 mm) having 5 through holes of 3 mm diameter installed in the mold (inner diameter 120 mm) maintained at the temperature of 300 ° C. I wore it.

A molten metal of a matrix Al alloy (JIS standard 6061) having a hot water temperature of 850 ° C. was poured into the mold, and the plunger was pushed down from the top at a speed of 2 mm / sec. Pressurization of the plunger is
The molten metal that has flowed down in the preform structure is squeezed out from the pores of the pedestal board and solidified from the state of filling the void to 1000
It was kept at ks / cm ² .

The SiC whisker-reinforced Al composite material thus obtained had no defects such as cracks and cracks in the structure, and no abnormal structure portion due to component deviation was observed up to the bottom surface.

Gas content of this composite was measured by Landsley method
The amount was 0.66 cc / 100 g, which was extremely small, and the tensile strength was 47.7 kg / mm ^2, which was a good composite property.

〔The invention's effect〕

According to the present invention, the normal molten metal state is maintained in the impregnation process during pressure casting, the unidirectional permeation from the upper surface of the preform, and the action of the stored gas component and the reaction foreign matter to be extruded out of the system synergistically. It is possible to obtain a composite structure having a uniform property with no deviation abnormality, which is superior to the desired technique. Therefore, it is of great value as a mass production technology for producing a high-performance fiber-reinforced metal composite material using whiskers as a reinforcement material.

[Brief description of drawings]

FIG. 1 is a sectional view of an apparatus for explaining the method of the present invention, FIG.
FIG. 1 is a sectional view of an apparatus for explaining a conventional pressure casting method. 1 ... Whisker preform, 2 ... Mold, 3 ...
Matrix metal melt, 4 …… plunger, 5 ……
Insertion mold, 6 ... Pedestal base, 7 ... Pores, 8 ... Vacancy.

Claims (1)

[Claims] 1. A whisker preform is placed in a mold as a fiber skeleton, and a molten metal of a matrix metal is poured into this to form a composite by a pressure casting method. The molten metal of the matrix metal is unidirectionally pressed from the upper surface of the preform by setting it in the mold and inserting it into the mold, and part of the molten metal that flows down while filling the structure of the preform is placed on the base plate. A method for producing a fiber-reinforced metal composite material, which comprises pressurizing it out of the system through pores.