JPS62238062A - Production of fiber reinforced metallic composite material - Google Patents

Abstract

PURPOSE:To prevent difficult working, dimensional change and shape change by setting a preform into a preheated internal metallic mold and force-feeding a molten metal unidirectionally from the top surface by a pressure casting method so that part of the flowing-down molten metal is forced to the outside of the system. CONSTITUTION:The preform 1 of whiskers molded to conform to the inside surface shape of the internal metallic mold 5 is set into the metallic mold 5 and is preheated at the same instant. The set metallic mold 5 is inserted to the upper part of a base seat plate 6 disposed in a casting mold 2. The base seat plate 6 has plural pieces of fine holes 7 communicating with the top and the bottom and has a cavity 8 of a molten metal pool between said plate and the bottom plate of the press. The molten metal 3 of a matrix metal is then poured into the casting mold 2 and is pressurized from above by a plunger 4. The molten metal 3 is penetrated unidirectionally into the preform only from the top surface thereof. The molten metal flows down while filling the inside of the preform structure and is forced from the fine holes 7 of the base seat plate 6 into the cavity 8. The matrix metal is thereafter allowed to solidify while the prescribed pressure is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improved method for producing fiber-reinforced metal composites by pressure casting using whiskers as reinforcing materials.

[Conventional technology]

Whiskers composed of needle-like single crystals such as SiC, 5iaN*, or graphite are fibrous materials that have excellent physical properties in terms of specific strength, specific modulus, heat resistance, and chemical stability, and are particularly useful for Aρ. It is useful as a composite reinforcing material when typical light metals are used as a matrix.

Conventionally, a pressure casting method has been known as an effective means for manufacturing fiber-reinforced metal composite materials using this type of whiskers. In the pressure casting method, as shown in Fig. 2, a preformed whisker-aggregated preform 1 is placed inside a mold 2 as a fiber skeleton, and a molten matrix metal 3 is poured into the mold 2, which is then heated with a plunger 4. The material is impregnated into the preform structure while being pressed and solidified to form a composite.The most important operational condition when using this method is to maintain the molten state of the matrix metal normally throughout the impregnation process. be. When the molten metal cools during the impregnation process and solidification of the matrix metal occurs, smooth penetration into the preform structure is inhibited, resulting in property defects such as cracks in the composite part, extreme shrinkage deformation of the composite, and heterogeneity of the composite structure. will give.

Additionally, in order to ensure smooth impregnation, the method used up until now has been to infiltrate the molten metal from the top and all sides of the whisker preform in the direction of the arrows, as shown in Figure 2. This leads to a phenomenon in which gas components occluded within the preform structure or component segregation due to certain reactions occurring during impregnation with molten metal are trapped in the center of the composite, causing defects in the structure.

Taking the above matters into consideration, the author has already proposed a composite method in which the whisker preform is set in a preheated inserting mold and inserted into the mold (patent application No. 60-281982).

[Problem that the invention seeks to solve]

According to the decoupling method of the earlier application, impregnation with molten metal is carried out with the whisker preform set in a preheated insert mold, so that the temperature inside the system is sufficiently maintained throughout the impregnation process. , the molten matrix metal permeates unidirectionally from the top surface of the whisker preform, pushing the occluded gas components present inside the preform structure and reactive foreign substances that cause component segregation to the bottom, resulting in structural abnormalities as a whole. This has the effect of obtaining a complex with less.

However, with this method, it is not possible to completely discharge the occluded gas components and reactive foreign substances pushed to the bottom out of the system.
In many cases, it remains in a layer and solidifies at the bottom. Therefore, it is necessary to excise this abnormal tissue portion, which poses problems such as difficult processing, reduction in size, and change in shape.

[Means for solving problems]

The present invention has been made for the purpose of improving the problems of the prior art, and the provided method for manufacturing a fiber-reinforced metal composite includes arranging a whisker preform as a fiber skeleton in a mold. When injecting the molten matrix metal and deconsolidating it by pressure casting, the whisker preform is set in a preheated insert mold and inserted into the mold to form the molten matrix metal.
--The structural feature is that the molten metal is unidirectionally press-fitted from the top surface of the system, and a part of the flowing molten metal is forced out of the system through the pores of the pedestal board while filling the structure of the preform. do.

Hereinafter, the present invention will be explained in detail based on the explanatory diagram of FIG.

First, a whisker preform l that will become a fiber skeleton is set in a preheated insert mold 5. The whisker preform is an aggregate of short fibers formed by a dry or wet method after dismantling generated whiskers such as Src, S13N4, or graphite, and is formed into an outer shape that matches the inner shape of the insert mold 5. be done. The inner insert 5 is made of a hard metal with excellent thermal conductivity, such as tool steel, and the inner surface is formed to follow the final shape, such as a cylinder, an inverted cone, or a concave/convex surface (1/f), and the outer surface is made of a hard metal with excellent thermal conductivity, such as tool steel. It is designed and processed to have an integral or split mold structure so that it comes into close contact with the inner wall of the mold 2 when installed.

Before inserting the insert mold 5 into the mold 2, it is heated using an electric furnace or the like, preferably to a temperature higher than the melting point of the matrix metal. It is effective to preheat the whisker preform 1 to be set at the same time, and for this purpose, it is operationally convenient to preheat the whisker preform 1 while it is set in the insert mold.

At this time, it is possible to control the degree of vertical shrinkage of the composite material by adjusting the preheating temperature of the insert mold and preform, so by weighing in advance, the fiber volume ratio (vr) can be controlled. It can be adjusted as appropriate.

The inner mold 5 in which the whisker preform is set is then inserted into the upper part of the pedestal board 6 placed in the mold 2. The pedestal board 6 is equipped with a plurality of pores 7 passing through the top and bottom,
It has a structure in which a cavity 8 for a molten metal reservoir is formed between the press bottom plate and the press bottom plate. Throughout the impregnation process, the mold is heated entirely by an attached heating device.

Subsequently, a molten metal 3 of the matrix metal is poured into the mold and pressurized with a plunger 4 from above. Due to the pressurization, the molten metal 3 permeates only from the upper surface of the whisker preform 1 in the direction of the arrow, flows down while filling the preform structure, and is forced out into the cavity 8 through the pores 7 of the pedestal board 6. Molten metal 3 is empty space 8
After filling, the matrix metal is solidified while maintaining a predetermined pressure.

[For production]

According to the above-described manufacturing method, the molten metal of the matrix metal permeates in one direction from the top surface of the whisker preform, pushes the occluded gas components and reactive foreign substances present inside the preform structure down to the bottom, and finally ends up in the pores 7. It is forced out into the cavity 8 outside the system. This effect, together with the sufficient heat retention effect of the insert mold, function effectively to form a composite condition free of tissue abnormalities.

〔Example〕

S having a diameter of 0.5 to 1.5μ, a length of 60 to 100μ, a density of 3.18 g/am3, and a β-type crystalline property.
After thoroughly dissolving the iC whiskers, they were dispersed in pure water, and a wet whisker cake was formed by excessive pressure, which was then heated and dried to form a cake with a diameter of 80 JIJ! , height L 40 ffx.

A cylindrical preform with wL fiber volume ratio Vr) of 15% was created.

The above SiC whisker preform has an inner diameter of 8ONJ.
I, outer diameter 120III11! It was inserted and set into a tool steel (SK material) inner mold with a height of 140 mm, and this was placed in an electric furnace and preheated to 730°C. The preheated inner mold was inserted into a mold (inner diameter 120°C) maintained at a temperature of 300°C.
It was inserted into the upper part of a hollow-bottom pedestal board (height l0xi) having five through-holes with a diameter of 3H installed at the center of the pedestal (Rm).

Matrix AQ alloy (JIS
Pour molten metal of standard 6061) from the top and pour 2ffj! /
It pushed Blancheer down at the speed of seconds. The pressurization of the bran shear was maintained at 1 OOO kg/cm'' until the molten metal flowing down within the preform structure was squeezed out from the pores of the pedestal and filled the voids until it solidified.

The SiC whisker-reinforced AQ composite thus obtained had no defects such as cracks or cracks in the structure, and no abnormal structure due to component segregation was observed down to the bottom surface.

When the amount of gas contained in this composite material was measured by the Lansley method, it was 0.66 cc/1009, which was a very small amount, and the tensile strength was 47.7 kg/xx'', indicating good composite properties.

〔Effect of the invention〕

According to the present invention, the functions of maintaining a normal molten metal state during the impregnation process during pressure casting, unidirectional permeation from the upper surface of the preform, and pressing out of the system of occluded gas components and reactive foreign substances work synergistically to It is possible to obtain a homogeneous composite structure with no segregation abnormalities, which is even better than the proposed technique. Therefore, it is of great value as a mass production technology for manufacturing high-performance fiber-reinforced metal composites using whiskers as reinforcing materials.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the device for explaining the method of the present invention;
The figure is a sectional view of an apparatus for explaining a conventional pressure casting method. l... Whisker preform, 2... Mold, 3
... Molten matrix metal, 4... Blancheer,
5... Insertion mold, 6... Pedestal board, 7... Pore,
8... Blank space. 1st EI 2nd blade

Claims (1)

[Claims] A whisker preform is placed in a mold as a fiber skeleton, and molten matrix metal is injected into the mold to form a composite by pressure casting.The whisker preform is set in a preheated insert mold. By inserting the matrix metal into the mold, the molten metal is unidirectionally pressed into the preform from the top surface, and part of the molten metal that flows down while filling the structure of the preform is passed through the pores of the base plate. A method for producing a fiber-reinforced metal composite material, characterized by extruding it out of the system.