JPS64144B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a casting, and particularly to a method for producing a casting that is suitable for use in cases where special cores that are difficult to vent gas are used, such as in the case of explosion-proof valves.

In the foundry casting process, blowholes, pinholes, etc. occur due to gases contained in the molten metal, gases generated from the mold, and air engulfed during pouring, resulting in casting defects. (Gas blown defect) is known to occur. When such casting defects occur, the mechanical properties and pressure tightness of the casting deteriorate. Conventionally, in order to eliminate the above-mentioned disadvantages, a large number of gas venting holes are provided on the upper surface of the mold, and the generated gas is allowed to escape to the outside of the mold through these holes.

However, in the case of explosion-proof valves whose inner surfaces are lined with a double layer made of a heat insulating material such as ceramic and a steel plate, the double layer is generated from the heat insulating material because it is used as a core during casting. It is not possible for the gas to escape to the outside through the gas vent hole described above. Therefore, there is a problem in that cavities, which are casting defects, are generated within the thickness of the casting due to the gas being blown away by the gas generated from the heat insulating material.

The present invention was invented in view of the above-mentioned problems, and it is an object of the present invention to provide a method for manufacturing high quality castings free of casting defects. That is, in the present invention, a ring-shaped member having a central through hole is held between the mold and the core in a state where it passes through the casting part formed between the mold and the core in the thickness direction. At the same time, the gas vent hole formed in the mold and the center through hole of the ring-shaped member are in communication with each other, and under this condition, molten metal is poured into the mold to perform casting, and after completion of casting, the The present invention relates to a method for manufacturing a casting, characterized in that a hole-shaped part of the casting corresponding to a ring-shaped member is repaired, and by using this method, the above-mentioned object is achieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the method for producing a casting according to the present invention is applied to the production of an explosion-proof valve will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows a casting apparatus 2 for an explosion-proof valve 1, and this casting apparatus 2 is equipped with an upper mold 3 and a lower mold 4, respectively. The upper mold 3 is provided with a plurality of degassing holes 5 extending in the vertical direction, and ceramic tubes 6 having excellent heat resistance or bundles of glass fibers are housed in these degassing holes 5. ing.

Further, in FIG. 1, reference numerals 7a and 7b are bar-shaped sand baseboards provided to hold the cores in the upper and lower molds 3 and 4. In this embodiment, as clearly shown in FIG. A member consisting of a steel plate 9 is lined on the inner surface of the valve 1 as an explosion-proof member 10,
During casting, this explosion-proof member 10 is used as a core.

Further, in this embodiment, as shown in FIGS. 1 to 3, a ring-shaped member 11 for preventing gas blowing having a central through hole 12 is connected to an upper mold 3 and an explosion-proof member 10 as a core. The upper mold 3 is penetrated in the thickness direction of the casting forming part 18 formed between the
and the heat insulating material layer 8 (core) of the explosion-proof member 10. That is, this ring-shaped member 11
As shown in the figure, it is molded into an annular shape, and its central through hole 12 completely matches the inner diameter of the ceramic tube 6 of the same diameter and communicates with each other, and its upper surface 13 and lower surface 14 are formed into the upper mold. 3 and the heat insulating material layer 8, respectively. The above-mentioned ring-shaped member 11 is made of a material with excellent heat insulation properties such as ceramic, glass fiber, asbestos, etc., and has appropriate elasticity. A certain Ibi wool (trade name) is used.

Further, in FIG. 1, 16 is a sprue, ₁₇ is a runner, and 18 is a casting forming part. That is, the height t is selected to be slightly higher than the wall thickness T ₂ of the bulb 1 (for example, about 3 to 5 mm).

Next, the operation of manufacturing the explosion-proof valve 1 using the casting apparatus 2 as described above will be explained.

First, a plurality of degassing holes 5 are previously provided at appropriate locations on the upper mold 3 by drill cutting or the like, and the ceramic tubes 6 are placed in the holes 5. Then,
The ring-shaped member 11 is adhesively fixed to the upper mold 3 with an adhesive so that its central through-hole 12 matches the inner diameter of the ceramic tube 6 and communicates with each other.

Further, in order to use the explosion-proof member 10 consisting of the heat insulating layer 8 and the steel plate 9 as a core, both ends thereof are fitted into a pair of baseboards 7a and 7b fixed to the lower mold 4 and fixedly supported. Note that the cavity of the explosion-proof member 10 may be filled with sand. After that, upper mold 3
The frame is aligned with the lower mold 4 and set as one mold. At this time, the ring-shaped member 11 adhered to the upper mold 3 is pressed against the heat insulating material layer 8 as a core by the weight of the upper mold 3. Note that this ring-shaped member 1
The thickness of the ring-shaped member 11 is slightly thicker than the thickness of the cast molded part 18, and the heat insulating layer 8 has appropriate elasticity, so even if the outer surface of the heat insulating layer 8 is slightly curved, the ring-shaped member 11 and the heat insulating material layer 8 are directly joined in close contact with each other.

A sprue 16 is placed in the mold set in this way.
A casting process is performed by injecting molten metal 19. At this time, due to the interposition of the ring-shaped member 11, not only the gas contained in the molten metal 19, the gas generated from the mold, the air drawn in during pouring, but also the gas generated from the heat insulating material layer 8 as the core. The gas is passed through the center through hole 12 of the ring-shaped member 11 and the gas vent hole 5.
It is discharged to the outside of the mold through the ceramic tube 6 inside. Therefore, it is possible to reliably release all of the generated gases that may cause casting defects, so that a casting without defects such as cavities can be obtained.

Next, after the casting is completed, the casting is taken out of the mold, and the hole-shaped portion caused by the presence of the ring-shaped member 11 is repaired by, for example, welding or the like to close it.

Through the above series of operations, the explosion-proof valve 1 can be obtained. Since this valve 1 is insulated by the heat insulating material layer 8, it can be used for both heat resistance and cold resistance.

The above embodiment shows an example of the method of the present invention, and the present invention is not limited to this embodiment, and various changes can be made based on the technical idea of the present invention.

For example, in this embodiment, the heat insulating material layer 8 and the steel plate 9
Although the explosion-proof member 10 made of the above is used as the core, the present invention is also applicable to cases where a special core made of other materials from which gas is difficult to vent is used. It goes without saying that the present invention is applicable not only to explosion-proof valves but also to methods of manufacturing various types of castings.

As described above, according to the method of the present invention, the ring-shaped member for preventing gas blowing is passed through the casting part formed between the mold and the core in the thickness direction. Even if a core that is difficult to vent gas is used, the gas generated from the core can be passed through the center through hole of the ring-shaped member and the gas vent hole, respectively. This makes it possible to reliably release the liquid to the outside of the mold.
Therefore, the occurrence of cavities, which are casting defects (gas blowing defects), can be effectively prevented, and high-quality castings can be reliably obtained.

[Brief explanation of drawings]

The drawings show an embodiment of the method for producing a casting according to the present invention, in which Fig. 1 is a longitudinal sectional view showing the internal structure of the mold during casting, and Fig. 2 shows the arrangement of a ring-shaped member for preventing blowout. FIG. 3 is an enlarged longitudinal sectional view of the main part showing the state, and a plan view of the ring-shaped member for preventing blowing. 1...Explosion-proof valve, 2...Casting device, 3...
Upper mold, 4... Lower mold, 5... Gas venting hole, 8
...Insulating material layer, 9... Steel plate, 10... Explosion-proof member, 11... Ring-shaped member for preventing gas blowing, 12
. . . Center through hole of ring-shaped member, 18 . . . Casting forming part, 19 . . . Molten metal.

Claims (1)

[Claims] 1. A ring-shaped member having a central through hole is held between the mold and the core in a state where it passes through the casting part formed between the mold and the core in the thickness direction, and the ring-shaped member is held between the mold and the core. The formed gas vent hole and the center through hole of the ring-shaped member are brought into communication, and under this condition, molten metal is poured into the mold to perform casting, and after the casting is completed, the ring-shaped member is formed. A method for manufacturing a casting, characterized in that holes in the casting are repaired.