JPS6046860A - Production of casting consisting of fiber reinforced composite metal - Google Patents

Abstract

PURPOSE:To produce a casting which is reinforced with fibers to provide lighter weight and higher strength and to improve the quality thereof in the stage of producing the casting having an intricately shaped part in continuation to a base part by fixing a long fiber molding to the reinforcing part in the base part of a casting mold and disposing an expendable core in the intricately shaped part then performing high-pressure casting. CONSTITUTION:Long fibers are arranged in accordance with the stress distribution in a base part 22 to manufacture a sheet. The sheets are superposed and are bound by a binder to form a long-fiber molding 29. The molding 29 is fixed by means of a screw shaft 30 and nuts 31, 32 to the space position in the part for reinforcing the base part 23 of a casting mold 27. An expendable core 34 is assembled and disposed in the space position of an intricately shaped part 23. The mold 27 is then clamped and the entire part of the mold 27 is preheated and at the same time the inside of the mold 27 is evacuated to remove the binder by vaporizing. A molten metal 26 is then poured into the mold 27 and is pressurized by a plunger 28 by which the molten metal is cast. A casting 21 is taken out and the nut 31 is removed. The casting is dipped in a concd. nitric acid until the core 34 is collapsed. The casting is neutralized by a neutralizing liquid and is dried. The remaining screw bar 30 and the nut 32 are thereafter removed by machining.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention is a method for manufacturing cast products with complex shapes and requiring high strength, such as the impeller of a small centrifugal compressor, using fiber-reinforced composite metals. The present invention relates to a manufacturing method for.

(Prior Art) Generally, special mechanical properties are often required in some parts of mechanical parts. For example, in the impeller of a gas turbine centrifugal compressor, the boss part has high rigidity,
This applies to cases where high toughness is required. As a means of partially adding such high rigidity and high @ property, it is conceivable to fiber-reinforce only that part.

Incidentally, since the impeller of the centrifugal compressor has a large number of blades with complicated shapes, it is generally cast by a lost wax method. In this lost wax method, as shown in Fig. 1 (A), brazing material A is injected into a female mold 11 consisting of a split mold, and a male mold 12 made of wax is molded. As shown in FIG. 1(C), the male mold 12 made of wax was used to make the female mold 13, which is an integral type made by Nanamik.
After heating the female mold 13 to eliminate the male mold 12, as shown in FIG. 1(D), molten stainless steel 14 is poured into the female mold 13 for casting. Break it and take out the internal casting 15.

Here, for weight reduction, the above H? A product (impeller) 15
f: In order to make up for the lack of strength when using aluminum, it is conceivable to partially strengthen it with fibers as described above. It is conceivable to make a cast product 15 made of fiber-reinforced composite metal (hereinafter referred to as "FRM") whose base material is aluminum.

Therefore, in order to obtain a cast product made of FRM by the above-mentioned lost wax method, first, a long fiber molded body 16 made of long fibers hardened with a binder is placed in the female mold 11 shown in FIG. 1(A), In FIG. 1(B), the male mold 12 containing the long fiber molded body 16 is formed, and in FIG. 1(C), the male mold 12 is removed to leave the long fiber molded body 16. ), the molten metal 14 is poured into the female mold 13 to perform casting. In this way, the long fiber molded body 16 was put into the female mold 11 in the first step, the step shown in FIG. 1(A), just before pouring the molten metal 14 in the step shown in FIG. 1(D). Even if you try to put the long fiber molded body 16 into the female mold 13,
This is not possible because the female mold 13 is of one piece. However, although a high pressure is required to sufficiently impregnate the inside of the long fiber molded body 16 with the molten metal, the above-mentioned lost wax method uses atmospheric casting, so the impregnation becomes insufficient and the desired high strength cannot be achieved. is not obtained. Furthermore, when the male mold 12 is eliminated in the process shown in FIG. 1(C), there is no longer anything to support the long fiber molded body 16, so there is a problem that the long fiber molded body 16 may be misaligned.

Therefore, as a means of obtaining complex-shaped FRM cast products by high-pressure casting, a long fiber molded product 16 is placed in a female mold divided into many parts.
It is conceivable to cast the mold using a molten metal forging method, but this has the disadvantage that the bath flows out through the divided gaps in the female mold, impairing quality and increasing the cost of the mold.

Note that a manufacturing method for obtaining a fiber-reinforced cast product by atmospheric casting similar to the lost wax method is described in JP-A-55-103924.

(Objective of the Invention) This invention was made in view of the above-mentioned problems, and it is possible to obtain a cast product with a complex shape that is light in construction, has surface strength, and has excellent quality by reinforcing fibers, while reducing mold costs. Also cheap FRM
The purpose of this invention is to provide a method for manufacturing cast products.

(↑Configuration of the Invention) In order to achieve the above object, the present invention has a complex-shaped part continuous to the base, like the impeller of a centrifugal compressor, which has a large number of complicated blades on the outer periphery of the yjf space part. In order to manufacture a cast product, a long fiber molded body made of long fibers hardened with a binder is fixed in a spatial position corresponding to the part of the base to be strengthened in the mold, and the complex structure in the mold is fixed. High-pressure casting is achieved by placing a vanishing core in a spatial position corresponding to the shaped part, injecting molten metal into the mold, performing molten metal forging under high pressure, and melting and removing the vanishing core after casting. FRMg castings are obtained.

Here, the long fibers constituting the long fiber molded article refer to fibers having a diameter of several μm to several μm and a length of several tens of micrometers or more. Common materials include carbon, alumina, glass, silicon carbide, and poron.The long fibers of these materials are aligned in the desired direction and hardened with a binder to form a sheet, which is stacked in large numbers to form long fibers. It is preferable to use it as a molded body.

The above-mentioned vanishing core is easily melted with a solvent, has sufficient heat resistance strength, excellent surface roughness, and resistance to deformation during high-pressure casting, and has the following properties:
It is best to use a material with low hardness that will not damage the casting. Examples of such materials include sintered bodies of copper, copper alloy, or iron, or sintered bodies whose surfaces are plated with nickel or chrome.

Molten metal forging is generally well known, and in this invention,
It is preferable to carry out the reaction at a pressure of about 100 to 1,000 atmospheres.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Figure 2 shows the impeller 20 of a centrifugal compressor for a small gas turbine.
This impeller 20 is a cast product 21 cast by the manufacturing method of the present invention.

This cast product 21 has a complex-shaped part 23, which is a wing, continuous to the outer periphery of a base part 22, which is a bone.

Since the base portion 22 bears a large load based on centrifugal force, particularly high rigidity and high toughness are required.

FIG. 3 schematically shows the molten metal forging method used in the present invention to manufacture the cast product 21. In the same figure, storage tank 2
5, a molten metal 26 is poured into a metal mold 27, and a hydraulic plunger 28 is pushed in to perform pressure casting. Figure 4 shows the details.

In FIG. 4, first, a long fiber molded body 29 molded into a predetermined shape is separately produced. The manufacturing procedure is as follows: fiber diameter 8μ
Base part 22 obtained by stress analysis of alumina long fibers of m
The sheets are arranged based on the stress distribution map, and the sheets are stacked one on top of the other, and an organic binder such as acryloid is interposed, and the sheets are press-molded and fixed. When stacking the sheets, the sheets are stacked as closely as possible so that the fiber content (volume ratio) becomes 50% when impregnated with molten metal poured later, and then pressed.

The long fiber molded body 29 thus obtained is placed in the mold 27 at a spatial position corresponding to the portion where the base 220 is to be reinforced, and fixed to the mold 27 with the threaded rod 30 and the nuts 31 and 32. The mold 27 includes a pair of left and right upper molds 27A and 27B.
The long fiber molded body 29 is fixed to the upper molds 27A and 27B by inserting a tapered nut 31 between the upper molds 27A and 27B.

Next, the spatial position sandwiched between the wings 33, that is, the mold 27
At a spatial position corresponding to the complex-shaped portion 23 within the
The vanishing cores 34 divided according to the number of wings 33 are assembled and arranged. In this example, the vanishing core 34 is placed in the lower mold 27C.
It is listed on. The vanishing core 34 is made of copper alloy (Cu-
It is made of a sintered body of 10% Sn alloy).

l In this state, the mold 27 is clamped, and the mold 27
The entire body is preheated to 250 to 500°C to prevent the molten metal from solidifying too quickly during pouring, and the pressure inside the mold 27 is reduced to gasify the acryloid in the long fiber molded body 29. make it disappear

Next, Al-8i-Cu alloy (JIs symbol AC4D
) is injected into a mold 27 and pressurized to approximately 700 to 1,000 atmospheres with a plunger 28 for casting.

In this way, the long fiber molded body 29 and the disappearing core 34 are cast together.

After solidification, the cast product 21 is taken out from the mold 27, the nut 31 is removed, and the cast product 21 is immersed in concentrated nitric acid, and the immersion is continued until the dissipation core 34 partially dissipates and breaks apart.

It is then neutralized with a neutralizing liquid such as soda carbonate and dried. After drying, the other part of the broken vanishing core 34 is removed manually.

In this state, the threaded rod 30 and nut 32 remain inside the cast product 21. Next, the shaft hole is machined and puffed to complete the impeller 20 having the shape shown in FIG. The remaining threaded rod 30 and nut 32 shown in FIG. 3 are also removed by the machining described above.

According to the above manufacturing method, the high pressure sufficiently impregnates the molten metal 26 into the long fiber molded body 29, so that the impeller 20 shown in FIG. 2, which is reinforced with long fibers and has high strength, is obtained. Actually, when this impeller 20 was attached to a high-speed rotation test machine and rotated in a vacuum, and a cold spin tenuto was performed in which only centrifugal force was applied without applying air compression force, the circumferential speed at which a burst occurred was determined. It was about 65 Q Sokuden.

In contrast, in the conventional stainless steel impeller manufactured by the lost wax method shown in Fig. 1, the circumferential speed at which bursting occurs is approximately 550 l, indicating that the impeller 20 according to the present invention has high strength. There is. Finally, in this invention, the material of the impeller 20 is made of aluminum to reduce weight, but the conventional heavy impeller made of stainless steel has even higher strength. It has extremely great significance in that it can simultaneously achieve strength.

Furthermore, since the mold 27 shown in Fig. 3 is not a mold divided into many parts, there is no problem such as the molten metal 26 flowing out from the gaps between the molds, which would impair quality, and the mold cost is also low. Become.

(Effects of the Invention) As described above, according to the present invention, a complex-shaped cast product can be made lighter and stronger by fiber reinforcement, and its quality is improved. Furthermore, the cost of casting is also low.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing an example of a conventional casting method, Fig. 2 is a longitudinal sectional view showing an example of a cast product made by the manufacturing method of the present invention, and Fig. 3 is a process diagram showing an example of a cast product manufactured by the manufacturing method of the present invention. FIG. 4 is a longitudinal sectional view showing the main parts of FIG. 3. DESCRIPTION OF SYMBOLS 21... Cast product, 22... Base, 23... Complicated shape part, 26... Molten metal, 27... Mold, 29... Long fiber molded object, 34... Vanishing core.

Claims (1)

[Claims] (υ A method for manufacturing a cast product with a complex-shaped part continuous to the base, in which long fibers are hardened with a binder and placed in the mold at a spatial position corresponding to the part of the base to be strengthened.) The molded body is fixed, a vanishing core is placed in the spatial position corresponding to the complex-shaped part in the mold, molten metal is injected into the mold, molten metal is cast under high pressure, and the vanishing core is disposed of after casting. A method for producing a cast product made of fiber-reinforced composite metal by melting and removing the core.