JPH07121446B2 - Method for manufacturing cast ceramic body - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a cast ceramic body.

(Prior Art) When a wear-resistant adiabatic casting is manufactured by casting ceramics with a metal such as an aluminum alloy or cast iron, the ceramics may be damaged by thermal shock when a high-temperature molten metal comes into contact with the ceramics. . Further, since the coefficient of thermal expansion of ceramics is significantly smaller than that of metals, the ceramics may be damaged by the internal compressive stress generated when the molten metal cools and solidifies and contracts.

In order to solve such a problem, an intermediate layer having heat insulation and flexibility, such as kneading foundry sand, is provided around the periphery of the ceramic cast-in portion to reduce the thermal shock generated when pouring the molten metal, and There has been proposed a method of absorbing internal compressive stress generated during cooling (for example, Japanese Patent Laid-Open No. 53-83).
No. 26 bulletin).

(Problems to be Solved by the Invention) However, in the above method, since the gap between the sand grains of the foundry sand is small, the molten metal does not penetrate into the intermediate layer during the casting process, and the ceramic substrate and the cast metal are joined together. There was a problem that the strength became weak.

The present invention has been made in view of the above circumstances, when the ceramic is cast with an aluminum alloy or cast iron, the ceramic is not damaged by thermal shock or cooling shrinkage of the molten metal, and It is an object of the present invention to provide a method for producing a cast ceramic body that is firmly bonded to a stuffed metal.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention forms a cast body by mounting ceramic beads (small particles) in layers around a ceramic substrate, and thereafter, performing the cast casting. It is characterized by pouring molten metal around the body and surrounding it.

Hereinafter, the present invention will be described in detail based on examples.

(First Embodiment) FIGS. 1 to 5 show a manufacturing process in an embodiment of the present invention. FIG. 1 is a vertical sectional view of a cast body, FIG. 2 is a sectional view of the same, and FIG. FIG. 4 is a cross-sectional view showing a state in which the cast body is set in a mold, FIG. 4 is a vertical cross-sectional view of the cast ceramic body, and FIG.

In the figure, first, on the outer peripheral surface of a cylindrical ceramic substrate (1) made of dense alumina (99.5%) having a height of 70 mm, an outer diameter of 40 mm, and a wall thickness of 3 mm, alumina beads (9
2% high-alumina sintered body (2) is attached in a layer (single layer) through a heat-resistant inorganic adhesive (Nissan Chemical's Bond X) (3). The interval between the alumina beads (2) is 0.4 ± 0.2 mm or more. Next, a sheet-shaped polystyrene member (4) having a thickness of 20 mm is wound around the outer peripheral portion of the alumina bead (2) layer, and the outer peripheral surface of the polystyrene member (4) is coated with a mold (5) to be cast. Body (6)
(See FIG. 1). After that, the cast body (6)
After attaching the polystyrene runner (7) to this,
Set in the flask (8). The casting frame (8) has a ventilation structure and an inner box (9) having an open upper end, and a side surface and a bottom of the inner box (9) are surrounded to reduce pressure between the inner box (9). It consists of an outer box (12) that constitutes the room (11),
The outer box (12) is provided with a conduit (13) having one end communicating with the decompression chamber (11) and the other end connected to a vacuum pump (not shown).

The inner box (9) of such a flask (8) is filled with silica sand for foundry sand (AFS grain size -100 equivalent) (14), and fluidity is imparted to the silica sand (14) by vibrating means (not shown). Meanwhile, the upper end of the sprue (7) of the cast body (6) is an inner box (9).
It is set in the inner box (9) so that it appears on the upper surface of the. Next, the upper surface of the flask (8) excluding the upper end of the gate (7) is sealed with an airtight sheet (15) of vinyl acetate copolymer, polyethylene or the like.

Then, a vacuum pump (not shown) is operated to exhaust the air in the inner box (9) through the pipe line (13) and the decompression chamber (11), and thereby the pressure in the inner box (9) is changed to the atmospheric pressure. From 200 to 500
Make it as low as mmHg. As a result, the silica sand (14) will become the inner box (9).
Inside the object to be cast (6) is solidified while it is built in to form a mold (see FIG. 3). In this state, cast iron at 1380 ℃ (1
When the molten metal of 6) is poured from the upper end of the melt spout (7), the polystyrene member (4) and the adhesive (3) in the cast body (6)
Are vaporized by combustion, and the cavities and gaps generated thereby are filled with the molten metal in a substitutional manner, and the cast ceramic body (17) is molded. After a lapse of a predetermined time, when the vacuum pump is stopped and the depressurized state in the inner box (9) is released, silica sand (14)
Since the movement of each particle becomes free and the mold collapses, the product inside can be easily taken out. When the cast ceramic body (17) thus obtained was cut and its structure was examined, as shown in FIG. 4, the inner alumina ceramic layer (1), the outer cast iron layer (16) and both It was formed from three layers of a composite layer of alumina beads (2) and cast iron (16) which were present in the middle, and no presence of break cracks was observed in any of the layers.

(Second Embodiment) FIG. 6 is a front view in vertical section of a cast body in another embodiment of the present invention, FIG. 7 is a side view in the same section (in AA line in FIG. 6), and FIG. FIG. 9 is a vertical sectional front view of the cast ceramic body, and FIG. 9 is a vertical sectional side view (in the line BB in FIG. 8).

In the figure, the alumina beads (2) having an average particle size of 4 mm are mutually attached on the surface of a ceramic substrate (1) made of dense alumina of 70 mm × 45 mm × 30 mm having irregularities formed on the surface, as in the case of the first embodiment. With a distance of 0.4 ± 0.2 mm or more, and they were mounted in a layer (single layer) through a heat-resistant inorganic adhesive (not shown).

Next, a polystyrene member (4) molded in the same shape as the cast iron to be joined is mounted on the upper surface of the alumina bead (2) layer, and a coating mold (not shown) is attached to the surface of the polystyrene member (4). Then, the cast body (6) as shown in FIG. 6 is formed. Then, the cast-in body (6) is set in the same casting frame as in the case of the first embodiment, and cast iron (1
The molten metal of 6) was poured to obtain a cast ceramic body (17) as shown in FIG. This is also composed of three layers, the alumina ceramic layer (1), the cast iron layer (16) and the composite layer of the alumina beads (2) and the cast iron (16) as in the first embodiment, and any of the layers is damaged. The presence of cracks was not recognized.

(Operation and Effect) According to the present invention as described above, the molten cast iron (16) injected into the mold first vaporizes and vaporizes the polystyrene member (4) constituting the outer shell of the cast-in target (6). The cast iron layer (16) is formed by substituting the resulting space into the cast iron layer (16). At this time, the alumina beads (2) coating the outer peripheral portion of the ceramic substrate (1) in a layered form have a heat insulating effect. And the thermal shock to the ceramic substrate (1) is alleviated. Further, the molten metal is substituted and filled in the gap while burning and vaporizing the heat-resistant inorganic adhesive (3) filled in the gap between the alumina beads (2), whereby the alumina beads (2) A composite layer with cast iron (16) is formed. The molten metal is then cooled and solidified and contracted, and internal compressive stress is generated at this time, but the thermal expansion coefficient of the composite layer of the cast iron (16) and the ceramic beads (2) is larger than that of the ceramic substrate (1). Since it is large and smaller than that of the cast iron (16), the internal compressive stress of the hot molten metal is relieved by the composite layer, and damage to the ceramic base (1) is prevented.

On the other hand, a part of the molten metal filled in the gap between the alumina beads (2) is in contact with the surface of the ceramic base (1), and together with the internal compressive stress during solidification shrinkage, It works and tightens it. This tightening force remains even after the cast iron (16) is completely solidified and cooled, so that the ceramic substrate (1) and the cast-in-turn cast iron (16) are firmly joined.

In the examples, cast iron was used as the cast metal, and alumina beads were mounted around the ceramic substrate, but the former may be made of heat-resistant or corrosion-resistant metal such as aluminum alloy or stainless alloy, and the latter may be used at the melt temperature. Any ceramic beads that can withstand will do.

In the examples, the average particle size of the alumina beads was 4 mm, and the gap between the particles was 0.4 ± 0.2 mm or more, but this is the set value in the case of gravity casting, and in the case of pressure casting the particle size and The particle spacing may be smaller.

Further, although the alumina beads are mounted in a single layer around the ceramic substrate, they may be mounted in multiple layers. In this case, the particle size of the alumina beads is made smaller, for example, as they are closer to the ceramic substrate, and vice versa. By increasing the size to control the composite layer of alumina beads and metal, stronger cast-gurgle bonding becomes possible.

In addition, it is necessary to sufficiently examine the mold plan, the melt pressure, the melt temperature, etc. so that the metal melt uniformly contacts the alumina beads during the pouring and sufficiently penetrates into the gaps between the alumina beads.

Further, in the embodiment, the cast ceramic body was manufactured by the full molding method, but it may be manufactured by a green casting method or another casting method.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an object to be cast in one embodiment of the present invention, FIG. 2 is a sectional view of the same, FIG. 3 is a sectional view showing a state where the object to be cast is set in a mold, and FIG. FIG. 5 is a vertical sectional view of the toy body, FIG. 5 is a sectional view of the same body, and FIG. 6 is a vertical sectional front view of a cast-in body according to another embodiment of the present invention.
FIG. 8 is a vertical sectional side view, FIG. 8 is a vertical sectional front view of a ceramics cast body, and FIG. 9 is a vertical sectional side view. (1): Ceramics substrate, (2): Alumina beads (3): Adhesive, (4): Polystyrene member (6): Cast object, (8): Cast frame (16): Cast iron, (17): Ceramic cast body

Claims (1)

[Claims] A ceramic bead (2) is mounted in layers around a ceramic substrate (1) to form a cast body (6), and then a molten metal is poured around the cast body (6). A method for producing a ceramic cast-in body, which is characterized in that the cast-in-roll body is formed by.