JPH0732332A - Manufacture of hollow preform of metal based composite material and casting mold for manufacturing the same - Google Patents

Abstract

PURPOSE:To improve strength by a method wherein an outer mold and an inner mold are respectively divided axially to make upper and lower part outer molds and upper and lower part inner molds, and the lower part outer mold and the lower part inner mold are divided peripherally. CONSTITUTION:A tape 30 is stuck from inside to a divided part of a lower part inner mold 26 and a divided part between the lower part inner mold and an upper part inner mold 25 to form an integral inner mold 24. The inner mold 24 is placed at a central part on a floor mold 20. An upper part outer mold 22 and a lower part outer mold 23 are integrated with a tape 31 to form an outer mold 21 in parallel therewith. The outer mold 21 is placed on the floor mold 20 so as to enclose the inner mold 25. Then, slurry wherein a specific binder, water, etc., are mixed in a silicon carbide whisker is charged between the outer mold 21 and the inner mold 24. The silicon carbide whisker is deposited in the slurry, and water which is contained by about 75% in completion of deposit is discharged through an hole part of the outer mold 21 and the inner mold 24, or from a bottom part of the outer mold 21 or by vaporization. Then, a hollow preform of a metal group composite material is formed between the lower part outer mold 23 and the lower part inner mold 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hollow preform which serves as a strengthening mechanism in the production of hollow metal-based composite materials such as satellite parts and flying parts, and the manufacturing method thereof. It relates to a mold used for.

[0002]

2. Description of the Related Art Metal matrix composite materials have been developed to improve the properties of metals, and various materials such as clad materials, dispersion strengthened metals and fiber reinforced composite materials are known. Among them, the fiber reinforced metal (FRM), which is a fiber reinforced composite material, is formed by first forming a preformed body (preform) that serves as a reinforcing mechanism with ceramic fibers or metal fibers, and then high pressure casting etc. Is a metal matrix such as aluminum or titanium cast into. Since such a fiber-reinforced metal has a strengthening mechanism different from that of metals and the like and does not rely on dislocation theory, it has excellent strength and elastic modulus at high temperatures. Especially, when a ceramic fiber is used as a reinforcing fiber, Since it is characterized by excellent specific strength and specific rigidity, it is being used in various applications such as turbine blades of jet engines for aircraft.

In the production of fiber reinforced metal (FRM) using ceramic fibers such as silicon carbide (SiC) whiskers and alumina (Al ₂ O ₃ ) short fibers, a method for molding the above preform is as follows. A mechanical molding method and a papermaking method are roughly classified. Here, the above-mentioned mechanical forming method is to press a ceramic reinforcing fiber with a press to form a desired preform. Although the forming is easy, the reinforcing fiber is destroyed by the forming pressure and the aspect ratio (fiber Since the length / fiber diameter) becomes small, there is a drawback that the reinforcing effect of FRM obtained by casting a metal is reduced.

On the other hand, in the papermaking method, as shown in FIG. 3, a ceramic is provided in a cavity 4 of a mold 3 in which a floor mold 1 and a cylindrical outer mold 2 are integrally molded of a porous material. A preform was obtained by injecting a slurry prepared by mixing a certain proportion of water and a binder such as soluble starch into the reinforcing fiber, and removing the water to complete the drying, and then removing the mold 3 described above. The preform has an advantage that it has a large reinforcing effect because the aspect ratio is almost unchanged.

[0005]

However, in the above-described papermaking method, in the drying / shrinking process in the cavity 4, since the drying speed in each part of the injected slurry is different, the strength of the preform itself is exceeded. The internal stress is generated and the preform is easily cracked.
It was limited to the molding of solid preforms.
That is, when an attempt is made to manufacture a hollow preform by using the outer mold and the inner mold by the above-mentioned papermaking method, there are the following specific problems.

First, in the process of drying and shrinking the slurry in the cavity, since the easiness of drying is different in each part, macroscopically nonuniform drying and shrinking occurs, and as a result, internal stress is generated in the preform. In this case, the solid preform does not exceed the preform strength because the internal stress does not exceed the preform strength because the symmetry and the center and the outer periphery of the solid preform are balanced, but the hollow preform has a thin wall, In addition, since there is no central portion and the balance with the outer peripheral portion cannot be achieved, there is a large tendency for cracking. here,
This type of crack is roughly classified into the following three types. Inner mold adjacent part cracking Since the slurry dries and shrinks as a whole, a strong internal stress is generated in the part of the preform which is in contact with the inner mold, and as a result, a crack is generated in that part. Through-hole cracking Since hollow preforms have a poor balance during drying and shrinking as described above, macro internal stress is stronger than solid preforms, and the strength is also weak. The cracks generated inside are connected to each other to form a through crack. Outer mold adjacent portion cracking When the outer mold of the mold is removed, the parallelism between the preform and the outer mold is likely to shift, so that scratches and cracks due to the outer mold occur on the outer periphery of the preform.

Another problem is that it is difficult to remove the inner mold from the mold after preform molding. That is, as described above, after the slurry is dried and shrunk, a strong internal stress is generated in the portion of the preform which is in contact with the inner mold, so that it becomes difficult to remove the inner mold from the preform after molding, and it is impossible to force. If you try to remove it with a strong force, the preform will crack. Due to such various problems, it has hitherto been impossible to produce a desired hollow preform by a papermaking method or the like, and its solution has been desired.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the invention according to claim 1 has a cylindrical outer die and an inner die having a drainage mechanism, respectively. It is divided in the axial direction into upper and lower outer molds and upper and lower inner molds, and the divided lower outer mold and lower inner mold are each divided in the circumferential direction, and then the upper and lower outer molds and the upper and lower inner molds are floor molds. After placing on top, a slurry containing water and ceramic reinforcing fibers is injected between the upper and lower outer molds and the upper and lower inner molds, and then water in the slurry is drained to remove the lower outer mold and the lower inner mold. After forming a hollow preform between and and removing the upper outer mold and the upper inner mold, the lower outer mold and the lower inner mold are separated from the respective divided parts and removed from the floor mold to obtain a hollow preform. It is a thing.

The invention described in claim 2 is the same as claim 1.
The ceramic reinforcing fiber described in (1) is characterized in that it is a whisker of silicon carbide or a short fiber of alumina.

Further, a third aspect of the present invention relates to a manufacturing mold for carrying out the invention according to the first or second aspect, which has a water draining mechanism, a floor mold, and A cylindrical outer mold placed on the floor mold, and a cylindrical inner mold disposed in the outer mold and injecting a slurry containing water and ceramic reinforcing fibers between the outer mold and the outer mold. And an outer mold and an inner mold, each of which is composed of an upper and lower outer mold and an upper and lower inner mold that are axially divided, and the divided lower outer mold and lower inner mold are each circumferentially divided. It is configured.

[0011]

According to the present invention, the outer mold and the inner mold are divided in the axial direction into the upper and lower outer molds and the upper and lower inner molds, respectively, and water in the slurry is drained between the lower outer mold and the lower inner mold. Since the hollow preform is formed, the preform is not formed between the upper outer mold and the upper inner mold. It can be removed very easily without interfering with. Further, at this time, no force is applied to the preform formed between the lower outer mold and the lower inner mold, so that the inner mold and outer mold adjacent portions of the preform are not cracked.

Further, since only the lower outer mold and the lower inner mold are made of a high-strength material having high surface accuracy and high roundness, cracks of the preform can be further reduced. , Economical.

Further, since the lower outer mold and the lower inner mold are divided in the circumferential direction, when removing the lower outer mold and the inner mold from the preform, it is only necessary to remove them in the diametrical direction of the preform. Since it does not slide directly on the outer periphery of the reform, there is no risk of causing excessive stress or damage to the preform. Therefore, although it has a diameter of about 1 μm or less like silicon carbide whiskers and the like and has an excellent effect of improving strength, on the other hand, it is suitable when a reinforced fiber which is easily broken during preform molding is used.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show one embodiment of a mold for producing a hollow preform of a metal-based composite material of the present invention, in which reference numeral 20 is a floor type. This floor mold 20
The outer appearance is substantially disc-shaped, and a cylindrical outer mold 21 is placed in a circular recess formed in the center thereof.

As shown in FIG. 2, the outer die 21 is composed of an upper outer die 22 and a lower outer die 23, which are divided into two substantially at the center in the axial direction, and further, the lower outer die 2 is formed.
3 is divided into two equal parts in the circumferential direction. Here, the length dimensions of the upper outer die 22 and the lower outer die 23 are
When pouring a slurry prepared by mixing water and a binder into the ceramic reinforcing fiber, the upper surface of the preform is below the upper end of the upper outer mold 22, and the height of the preform after drying the water is lower than that of the lower part. It is set so as to be below the upper end of the lower mold 23. An inner mold 24 is arranged inside the outer mold 21.

Like the outer mold 21, the inner mold 24 is composed of an upper inner mold 25 and a lower inner mold 26, which are divided into two at approximately the center in the axial direction, and the lower inner mold 26 further has a circumference. It is divided into two equal parts.
Here, the upper outer die 22 and the lower outer die 23 have their respective length dimensions set similarly to the outer die 21, and the division position thereof is the division position between the upper outer die 22 and the lower outer die 23. It is in the same position. And these floor molds 20,
The outer mold 21 and the inner mold 24 are each made of a porous material, and each hole constitutes a water draining mechanism.

Next, an embodiment of the method for producing a hollow preform of the present invention using the mold for producing a hollow preform having the above construction will be described. First, the lower inner mold 26
The tape 30 is attached from the inside to the divided portion of (1) and the divided portion of the lower inner die 26 and the upper inner die 25 to form the integral inner die 24. Next, the inner mold 24 is placed on the floor mold 20 at the center.

In parallel with this, the upper outer die 22 and the lower outer die 23 are similarly integrated by a tape 31 to form the outer die 21.
Then, the outer mold 21 is placed on the floor mold 20 so as to surround the inner mold 25.

Next, between these outer mold 21 and inner mold 24, a slurry prepared by mixing a silicon carbide whisker with a predetermined binder, water and the like is injected. Then, whiskers of silicon carbide are precipitated in the slurry, and the water containing about 75% at the completion of precipitation is passed through the holes of the outer mold 21 and the inner mold 24 or from the bottom of the outer mold 21,
Further, the slurry is evaporated and discharged from the upper surface of the slurry, and as a result, a hollow preform P is formed between the lower outer mold 23 and the lower inner mold 26.

Therefore, after the hollow preform P is formed, the tapes 30 and 31 are first peeled off and the upper outer mold 2 is removed.
2 and the upper inner mold 25 are removed, and then the lower outer mold 23 and the lower inner mold 26 are separated from the floor mold 20 by peeling off the tapes 30 and 31 attached to the respective divided portions. Thereby, the hollow preform P is obtained.

The hollow preform P thus obtained is preheated and then set in a mold to obtain about 100
A metal matrix such as an aluminum alloy is impregnated inside by a high pressure solidification forging method of 0 kg / mm ² to obtain a desired fiber reinforced metal product.

According to such a method for manufacturing a hollow preform, the outer mold 21 and the inner mold 24 are divided in the axial direction, and the upper and lower outer molds 22, 23 and the upper and lower inner molds 2 are divided.
Therefore, after molding the hollow preform P, the upper outer mold 22 and the upper inner mold 25 having a length less than half that of the conventional one can be very easily removed without interfering with the hollow preform P. it can. At this time, since no force is applied to the preform P formed between the lower outer mold 23 and the lower inner mold 26, the inner mold adjacent part crack and the outer mold adjacent part crack of the preform P may occur. Absent.

In general, in order to reduce preform cracks, the surface precision of the outer and inner molds in contact with the preform is improved to reduce the microscopic stress generated in the preform, or to improve the strength of the preform. It is important to improve the symmetry of the preform shape and reduce the macroscopic stress of the preform by selecting the mold material and using the outer mold and the inner mold having better roundness. However, if an outer mold and an inner mold that satisfy these requirements are manufactured, the cost of the entire mold increases. However, according to the above mold, only the lower outer mold 23 and the lower inner mold 26 need to have good surface accuracy and high roundness made of a high-strength material. As the upper inner mold 25, an inexpensive one having inferior performance can be used, which is economical.

Further, when the outer mold and the inner mold are integrated, when the preform is taken out after the completion of drying,
There is no other way than fixing the preform and moving the outer mold in the axial direction to remove it from the preform. However, in this method, in addition to applying an unnatural external force to the preform, it is unavoidable that the parallelism of the axes of the preform and the mold are different from each other in actual work of removal, and as a result, stress is applied to the preform. Is added and it is easily damaged.
In this respect, in the above mold, since the lower outer mold 23 and the lower inner mold 26 are circumferentially divided into two, when the lower outer mold 23 and the lower inner mold 26 are removed from the preform P,
Since it is only removed in the diametrical direction of the preform P, it does not slide directly on the outer periphery of the preform P. Therefore, there is no possibility that the preform P is overstressed or damaged. Therefore, although it has a diameter of about 1 μm or less like silicon carbide whiskers and the like and has an excellent effect of improving strength, on the other hand, it is suitable when a reinforced fiber which is easily broken during preform molding is used.

[0025]

Experimental Example Silicon carbide (SiC) whiskers (diameter: 0.5 μm, length: 30 μm) were used as reinforcing fibers, and a predetermined binder and water were mixed into the whiskers to obtain a slurry. Next, as an embodiment of the present invention, a mold having an acrylic outer mold and an inner mold divided in the axial direction and the circumferential direction as shown in FIG. 2 is combined to form a cavity between the outer mold and the inner mold, The above slurry was poured. Then, when the precipitation of whiskers was completed, the upper outer mold and the upper inner mold were removed, and after the drying was completed, the lower outer mold and the lower inner mold were removed in this order to obtain a hollow preform.

As a comparative example, the outer die and the inner die are 1
A mold having a body shape and a mold obtained by dividing the outer mold and the inner mold only in the axial direction were prepared, and the slurry was poured in the same manner as in the examples of the present invention. Then, after drying the slurry, the outer mold and the inner mold were removed to obtain a preform. The results of these tests are shown in Table 1.

As is clear from this table, in the comparative example,
Although cracks were found in the preform, there was no crack in the preform using the mold according to the example of the present invention.

[0028] ◯: No crack in preform ×: Crack in preform, XX: Large crack in preform

[0029]

As described above, the outer die and the inner die are axially divided into the upper and lower outer die and the upper and lower inner die, and the lower outer die and the lower inner die are circumferentially divided. Therefore, when removing the outer mold and the inner mold from the hollow preform, first, the upper outer mold and the upper inner mold having a length less than half of the conventional one can be extremely easily removed without interfering with the hollow preform. When the lower outer mold and the inner mold are removed, they are only removed in the diametrical direction of the preform, so that they do not slide directly on the outer periphery of the preform. Therefore, especially about 1 such as silicon carbide whiskers
Although it has a diameter of less than μm and has an excellent effect of improving strength, on the other hand, even when using reinforced fibers that are easily damaged during preform molding, excessive stress is generated in the preform or scratches may occur. There is no danger of

Further, since only the lower outer mold and the lower inner mold are made of a high-strength material which is expensive and has excellent surface accuracy and high roundness, preform cracking can be further reduced. It also has the advantages of being economical.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an outer die of a mold for producing a hollow preform of the present invention.

FIG. 2 is a vertical cross-sectional view showing one embodiment of the mold for producing a hollow preform of the present invention.

FIG. 3 is a vertical sectional view showing a conventional mold for producing a preform.

[Explanation of symbols]

 20 floor type 21 outer type 22 upper outer type 23 lower outer type 24 inner type 25 upper inner type 26 lower inner type

Claims (3)

[Claims] 1. A tubular outer die and an inner die having a water draining mechanism are divided in the axial direction into an upper outer die, a lower outer die, an upper inner die and a lower inner die. The lower outer mold and the lower inner mold are respectively divided in the circumferential direction, and then the upper and lower outer molds and the upper and lower inner molds are respectively assembled into an outer mold and an inner mold, and then these are placed on a floor mold, Then, a slurry containing water and ceramic reinforcing fibers is injected between the upper and lower outer molds and the upper and lower inner molds, and then water in the slurry is drained to form a hollow between the lower outer mold and the lower inner mold. A hollow preform is obtained by forming a preform and then removing the upper outer mold and the upper inner mold, and then dividing the lower outer mold and the lower inner mold from the respective divided parts and removing them from the floor mold. Metal-based composite characterized by Method of manufacturing hollow preform of material. 2. The method for producing a hollow preform of a metal-based composite material according to claim 1, wherein the ceramic reinforcing fibers are silicon carbide whiskers or alumina short fibers. 3. A floor mold, a cylindrical outer mold placed on the floor mold, and a water disposed between the floor mold and the outer mold. And a cylindrical inner mold into which a slurry containing a ceramic reinforcing fiber is injected, wherein the outer mold and the inner mold are composed of an upper and lower outer mold and an upper and lower inner mold, which are respectively divided in the axial direction, and A mold for producing a hollow preform of a metal matrix composite material, wherein the divided lower outer mold and lower divided inner mold are divided in the circumferential direction.