JPH0199768A - Manufacture of metal composite material - Google Patents

Abstract

PURPOSE:To prevent the generation of the crack and shrinkage of a reinforcing material formed body by fixing the reinforcing material forming body to a wall face by a fiber formed body so that it may be located between the wall face demarcating the mold cavity of a mold and the fiber formed body and solidifying it with pressurizing by leading in a molten metal. CONSTITUTION:A reinforcing material formed body 4 is integrally held by a fiber formed body 10 by fitting it into the groove 8 of the fiber formed body 10, which is fitted by the groove 8 part to the lower end of the movable die 14 of a high pressure casting machine 12 by preheating those. And the reinforcing material formed body 4 is fixed so as to locate between the fiber formed body 10 and the wall face 14b of a tip 14a. A molten metal 20 is then poured into the mold cavity 18 demarcated by the main die, etc., of the casting device 12, is pressurized by the movable die 14, is held until being solidified completely and a piston stock is formed. Consequently a good complex having no crack nor deformation can be formed.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a composite material having a metal matrix;
More specifically, it relates to its manufacturing method.

Conventional technology One of the methods for manufacturing composite materials using metal as a matrix is to form a reinforcing material molded body made of fibers or particles, place the reinforcing material molded body in a mold, and place the matrix metal in the mold. A so-called high-pressure casting method is conventionally known in which molten metal is poured and solidified while being pressurized by a movable mold such as a plunger or an upper mold that fits into a mold.

In manufacturing composite materials using this high-pressure casting method, it is difficult to properly composite the parts that come into contact with the movable mold. As described in JP-A No. 60-115360, there is a method of pressurizing the molten metal in a state in which the reinforcing material molded body is floating in the molten metal, and a method of reducing the volume fraction of the reinforcing material molded body. etc. have been devised.

Problems to be Solved by the Invention However, even with these methods, it is still difficult to perform appropriate compositing, especially when the reinforcing material is silicon carbide whiskers, ceramic particles, etc., and it is difficult to form the reinforcing material. If the body is brittle, the reinforcing material molded product is likely to shrink or crack, making it difficult to produce a good composite material.

The inventors of the present invention conducted a detailed experimental study on this problem, and as a result, it was found that the above-mentioned problem is mainly caused by an oxide film formed on the surface of the molten metal. That is, in general, in high-pressure casting, the reinforcing material compact is first contacted with the oxide film of the molten metal, so the oxidation film prevents the molten metal from penetrating well into the reinforcing material compact, resulting in non-uniformity. Temperature and pressure distributions occur, and it is presumed that cracks and shrinkage occur in the reinforcing material molded body due to these.

In view of the above-mentioned problems in the production of metal composite materials by conventional high-pressure casting, the present invention aims to produce metal composite materials that can be composited well without cracking or shrinking the reinforcing material molded body. The purpose is to provide a method.

Means for Solving the Problems According to the present invention, a reinforcing material molded body made of fibers or particles and having a relatively high volume percentage, and fibers having a volume percentage lower than that of the reinforcing material molded material are provided. a molded body, and fixing the reinforcing material molded body to the wall surface by the fiber molded body so that the reinforcing material molded body is located between the wall surface defining a mold cavity of the mold and the fiber molded body. This is achieved by a method for producing a metal composite material, which includes introducing a molten metal of a matrix metal into the mold, and solidifying the molten metal while pressurizing the molten metal in the mold.

Effects and Effects of the Invention According to the present invention, the reinforcing material molded body is fixed to the wall surface of the mold by the fiber molded body so that the reinforcing material molded body is located between the fiber molded body and the wall surface defining the mold cavity of the mold. In this state, the molten matrix metal is introduced into the mold, so the molten matrix metal does not come into direct contact with the reinforcing material compact, but penetrates into the reinforcing material compact after passing through the fiber compact. do. Therefore, the fiber molded body with a low volume fraction functions to support the reinforcing material molded body during the casting process and as a filter for the oxide film existing on the surface of the molten metal, so that when the fiber molded body is not used, In comparison, uniform penetration into the reinforcing material molded body is successfully achieved, which allows for good compounding without causing cracking or shrinkage of the reinforcing material molded body, and it is also possible to achieve good compounding without causing cracking or shrinkage of the reinforcing material molded body. It is possible to prevent the material molded body from being displaced from a predetermined position within the mold.

According to one detailed feature of the invention, the reinforcing material molded body is held integrally by the fiber molded body while being fitted into the recessed portion of the fiber molded body. According to this method, the reinforcing material molded object, which is often brittle, is protected by the relatively flexible fiber molded object, so that damage to the reinforcing material molded object can be avoided. In addition, since the fiber molded body acts as a heat insulating layer and a layer that suppresses air circulation, even when the molded body is preheated prior to the casting process, the temperature drop in the reinforcing material molded body is reduced and good composite formation is achieved. It is ensured that the reinforcing material is oxidized like carbon particles.

Even in the case of hard reinforcements, their deterioration during preheating is reduced. Furthermore, the region reinforced with a reinforcing material with a relatively high volume fraction is not directly continuous with only the matrix metal, but there is a region reinforced with fibers with a relatively low volume fraction between them. It is possible to avoid problems such as cracks caused by sudden changes in properties.

In addition, as mentioned above, when the reinforcing material molded body is fitted into the recess of the fiber molded body, these molded bodies can be fixed to the mold by press-fitting the recess into the convex part of the mold. preferable. In this case, the orientation of the fibers in the fiber molded body may be arbitrary, but since the fiber molded body receives force from the reinforcing material molded body and the convex portion of the mold, if the fiber orientation is two-dimensional random, The fibers are preferably oriented in a two-dimensional random manner along a plane parallel to the force to which the fiber molding is applied, so that the fiber molding has sufficient elasticity and therefore a sufficient retention function.

According to the results of experimental research conducted by the inventor of the present application, when the volume fraction of the fiber molded body is less than 2%, the fiber molded body cannot perform a good supporting function and function as a filter;
On the other hand, if the volume fraction of the fiber molded body exceeds 15%, the permeability of the molten matrix metal into the fiber molded body becomes poor,
It becomes difficult to perform good compositing. According to another detailed feature of the invention, therefore, the volume fraction of the fibrous molded body is set between 2 and 15%.

In order to set the volume fraction of the fibrous molded body within the above-mentioned range, the fibers constituting the fibrous molded body are preferably short fibers having a relatively large fiber diameter of about 1 to 10 μm.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

Example 1 First, as shown in FIG.
(Tokai Carbon Co., Ltd. "Toka Whisker") by compression molding so that the volume ratio is 20%
A plate-shaped reinforcing material molded body 4 having dimensions of 40×5111111 was formed. In addition, by suction molding and processing alumina fiber 6 ("Safil RFJ" manufactured by IC1), 30
A plate-shaped body having dimensions of x50 x 15iIi and a volume ratio of 7% is formed, and 2
By machining grooves 8 of 0x40x12 squares, a 1° fiber molded body having a U-shaped cross section as shown in FIG. 1 was formed.

Next, the reinforcing material compact 4 is fitted into the groove 8 of the fiber compact 1o, and the reinforcing material compact is held integrally by the fiber compact, and they are preheated to 400'C, and then heated as shown in FIG. By press-fitting the fiber molded body 1o into the lower end of the movable mold 14 of the high-pressure casting device 12 at its groove 8, as shown in FIG. fixed in between.

Next, 2° of molten metal of 740"C aluminum alloy (JIS standard AC8A) is poured into the mold cavity 18 defined by the main mold 16 etc. of the casting device 12, and the molten metal is poured into the mold cavity 18 by the movable mold 14 at a rate of 1200 kg/ C-, and the pressurized state was maintained until the molten metal completely solidified, thereby forming a piston rough material.

When the piston rough material thus formed was cut and the part reinforced with silicon carbide whiskers and alumina fibers was observed, there was no cracking or deformation of the reinforcing material molded body, indicating that the composite was well formed. It was recognized that this was being done.

In addition, for the purpose of comparison, a reinforcing material molded body similar to the reinforcing material molded body 4 was formed, and the reinforcing material molded body was fixed by being fitted into a groove formed at the lower end of the movable mold 14, and the above-mentioned example Casting was carried out using the same procedure and conditions as in the case of 2. When the composite reinforced part of the obtained piston rough material was observed, cracks had occurred in the reinforced material molded body, and the thickness was 51 to 3.
It was observed that the number decreased to 1. In this case, when the reinforcing material molded body was press-fitted into the groove at the tip of the movable mold, its corner was damaged.

Example 2 As shown in FIG. 3, by compression molding boron carbide particles 22 (average particle size 2μ), the volume fraction was reduced to 50%.
A disk-shaped reinforcing material molded body 24 with an outer diameter of 401111% and a thickness of 15fflIll was formed. Also, alumina fiber 2
6 ("Safil" manufactured by IC1), and the inner diameter was 40 mm so that the volume ratio was 12%.

A cup-shaped fiber molded body 28 having an outer diameter of 50 mm, a height of 20 cm, and a bottom wall thickness of 5 mm was formed.

Next, as shown in FIG. 4, the reinforcing material molded body 24 is fitted into the fiber molded body 28 to hold the reinforcing material molded body integrally with the fiber molded body, and then the reinforcing material molded body 24 is cast. By fitting the fiber molded body 28 into the plunger 34 so that it is located between the wall surface 34a of the tip end of the plunger 34 that fits into the lower mold 32 of the device 30 and the bottom wall of the fiber molded body 28, the fiber molded body 28 is inserted into the plunger 34. Fixed. Next, 700° C. molten magnesium alloy (JIS standard MCI) is poured into the mold cavity 36 defined by the lower mold 32 and the like, and after fixing the upper mold 40 to the lower mold 32, the plunger 34 is moved upward. By driving the molten metal
The molten metal was pressurized at a pressure of 0 kg/cj, and the pressurized state was maintained until the molten metal completely solidified, thereby forming a cup-shaped rough material.

When the thus formed cup-shaped raw material was cut and the part reinforced with boron carbide particles and alumina fibers was observed, it was found that no deformation or cracks had occurred in the reinforcing material molded body.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to these embodiments, and various other embodiments are possible within the scope of the present invention. This will be obvious to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the reinforcing material molded article and the fiber molded article in a state assembled with each other in Example 1, and FIG. 2 is the reinforcing material molded article and the fiber molded article shown in FIG. 1. An illustrative cross-sectional view showing the casting process carried out using
4 is a cross-sectional view showing the reinforcing material molded body and the fiber molded body assembled together, and FIG. 4 is a casting process performed using the reinforcing material molded body and the fiber molded body shown in FIG. 3. FIG. 2...Silicon carbide whisker, 4...Reinforcing material molded body. 6... Alumina fiber, 8... Groove, 10... Fiber molded body. DESCRIPTION OF SYMBOLS 12... Casting device, 14... Movable mold, 16... Main mold, 18... Mold cavity, 20... Molten aluminum alloy, 22... Boron carbide particles, 24...
... Reinforcement molded body, 26 ... Alumina fiber, 28 ...
・Fiber molded body. 30... Casting device, 32... Lower die, 34... Plunger. 36... Mold cavity, 38... Molten magnesium alloy, 40... Upper mold patent Applicant: Toyota Motor Corporation representative
1 reward for patent attorney Masaki Akashi! To N, So 3

Claims (3)

[Claims] (1) A reinforcing material molded body made of fibers or particles and having a relatively high volume percentage, and a fiber molded body having a lower volume percentage than the reinforcing material molded material are prepared, and the reinforcing material molded material is placed in a mold cavity of a casting mold. The reinforcing material molded body is fixed to the wall surface by the fiber molded body so as to be located between the wall surface defining the fiber molded body, and a molten metal of matrix metal is introduced into the mold, and the molten metal is A method for manufacturing a metal composite material that solidifies while being pressurized in a mold. (2) In the method for manufacturing a metal composite material according to claim 1, the reinforcing material molded body is held integrally by the fiber molded body in a state where it is fitted into a recess of the fiber molded body. A method for producing a metal composite material, characterized in that: (3) In the method for manufacturing a metal composite material according to claim 1 or 2, the volume fraction of the fiber molded body is 2 to 15
%.