JP2005046856A - Full mold casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a full mold casting method capable of reliably preventing dry cracks on a coating. <P>SOLUTION: In the full mold casting method, a coating agent containing refractory aggregate consisting of molten silica, graphite and clay, water and silica sol of the grain size of 10-30 nm is coated on a lost foam pattern 11 to form coating 13, the lost foam pattern 11 with the coating 13 thereon is embedded in casting sand 16, molten metal 17 is poured into the lost foam pattern 11, and the lost foam pattern 11 is lost to manufacture a casting. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a full mold casting method, and more particularly, to a full mold casting method for preventing dry cracks from occurring in a coating mold.
[0002]
[Prior art]
The full mold casting method performs casting using a disappearing model and is used for casting of a press die or the like.
[0003]
FIG. 2 shows a cross-sectional view of a mold when casting is performed by a conventional full mold casting method.
[0004]
As shown in FIG. 2, in the conventional full mold casting method, a vanishing model 21 made of a heat-dissipating material such as expanded polystyrene is manufactured, and a coating for improving the casting surface on the outer surface of the vanishing model 21 is produced. The mold 23 is formed, the disappearance model 21 having the coating mold 23 is embedded in the foundry sand 26, the molten metal 27 is poured from the spout 28 installed in the foundry sand 26, and the disappeared model 31 is melted and pyrolyzed. It is made to disappear and manufactures a casting, and even a complicated shape can be obtained with high accuracy (see, for example, Patent Document 1).
[0005]
[Patent Document 1]
JP 2000-140994 A [Problems to be solved by the invention]
As described above, the conventional full mold casting method uses the disappearance model 21 and can manufacture a highly accurate product even with a complicated shape. However, dry cracks are formed on the coating mold formed on the outer surface of the disappearance model 21. There is a problem that defective products may occur.
[0006]
The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a full mold casting method that reliably prevents dry cracks from occurring in a coating mold.
[0007]
[Means for Solving the Problems]
The full mold casting method of the present invention includes forming a coating mold with a coating agent containing a refractory aggregate composed of fused silica, graphite, and clay, water, and silica sol having an average particle diameter of 10 to 30 nm. did.
[0008]
The silica sol is included in an amount of 4 to 10%.
[0009]
Further, the coating agent contains a mixture of silica sol having an average particle diameter of 10 to 30 nm and silica sol having an average particle diameter of 50 to 500 nm.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0011]
FIG. 1 shows a cross-sectional view of a mold when casting is performed by the full mold casting method of the embodiment of the present invention, and FIG. 1 (a) is a coating used in the full mold casting method of the embodiment of the present invention. A partially enlarged sectional view of the mold is shown.
[0012]
As shown in FIG. 1, the mold 10 includes a casting frame 14, casting sand 16 accommodated inside the casting frame 14, and a vanishing model 11 embedded in the casting sand 16. The disappearance model 11 is manufactured from a synthetic resin foam material such as expanded polystyrene (EPS), polymethyl methacrylate (PMMA), and a copolymer of the both by an NC processing machine (not shown), and a coating mold 13 is formed on the outer surface. Is formed. The casting sand 16 is provided with a gate 18 and a water passage 19 communicating with the disappearance model 11. The coating mold 13 is formed by applying a coating agent to the outer surface of the disappearance model 11 and drying it.
[0013]
The coating agent used in the present invention, which is applied to the disappearance model 11 to form the coating mold 13, contains refractory aggregate, water, and silica sol. Therefore, as shown in FIG. 1 (a), the coating mold 13 formed by this coating agent has a fine silica sol particle between the relatively large refractory aggregate particles 12a and the refractory aggregate particles. 12b is mixed. The refractory aggregate is made of fused silica particles, graphite particles, and clay, and fused silica particles and graphite particles having an average particle diameter of 1 to 40 μm are used. Silica sol having an average particle size of 10 to 30 nm is used, and the amount is 4 to 10 parts with respect to 100 parts of the refractory aggregate. Since water becomes difficult to apply to the outer surface of the disappearance model 11 if the viscosity of the coating agent is too high or too low, the amount of water is 30 to 50 parts. It is difficult to obtain particles used for the refractory aggregate having an average particle size of 0.1 μm or less, but silica sols having an average particle size of 100 nm (0.1 μm) or less can also be obtained. The coating mold 13 formed with this coating agent can prevent dry cracks and prevent generation of defective products.
[0014]
When casting is performed, the molten metal 17 is poured from the gate 18, and the molten molten metal 17 passes through the runner 19 and enters the inside of the disappearance model 11 from the bottom, melts the disappearance model 11, and performs thermal decomposition. The generated liquid material, gas, and the like are discharged into the molding sand 16 through the coating mold 13 because the coating mold 13 has air permeability, and a casting is manufactured where the disappearance model 11 is embedded. The casting in the foundry sand 16 is removed by removing the cast frame 14 and then shot blasted over the entire surface to remove the adhering mold 13 and foundry sand 16.
[0015]
A coating mold under various conditions was prototyped with the coating agent used in the present invention, and the presence or absence of dry cracks was confirmed with a loupe.
[0016]
No dry cracking was observed in the trial coating using a coating agent in which silica sol having an average particle diameter of 10 nm was made 4 parts and 10 parts with respect to 100 parts of the refractory aggregate. In addition, dry cracking was not observed even in a trial coating mold using a coating agent in which silica sol having an average particle diameter of 30 nm was made 4 parts and 10 parts with respect to 100 parts of refractory aggregate.
[0017]
When using a silica sol having an average particle diameter of 5 nm and 35 nm and 4 parts and 10 parts of a silica sol with respect to 100 parts of the refractory aggregate, a silica sol having an average particle diameter of 10 nm and 30 nm is used as the refractory aggregate. Dry cracks were observed when the coating agent was 2 parts and 15 parts per 100 parts.
[0018]
Therefore, when the coating agent has an average particle size of silica sol in the range of 10 to 30 nm and 4 to 10 parts with respect to 100 parts of the refractory aggregate, it should reliably prevent dry cracking of the coating mold 13. Can do.
[0019]
The coating agent was prepared by mixing silica sol having an average particle diameter of 10 to 30 nm and silica sol having an average particle diameter of 50 to 500 nm to make 4 to 10 parts with respect to 100 parts of the refractory aggregate. Dry cracks can also be prevented, and in this case as well, the presence or absence of dry cracks as described above was confirmed.
[0020]
As described above, the full mold casting method according to the embodiment of the present invention can reliably prevent dry cracks in the coating mold 13 to be used.
[0021]
Note that the coating agent used in the full mold casting method of the embodiment of the present invention is not limited to a full mold mold, and can be used to form a coating mold on the surface of a sand mold to obtain the same effect. be able to.
[0022]
【The invention's effect】
The full mold casting method of the present invention includes forming a coating mold with a coating agent containing a refractory aggregate composed of fused silica, graphite, and clay, water, and silica sol having an average particle diameter of 10 to 30 nm. Therefore, dry cracking of the coating mold can be surely prevented, and defective products can be reduced.
[0023]
Further, since the silica sol is contained in an amount of 4 to 10%, it is possible to prevent the occurrence of dry cracks in the coating mold more reliably.
[0024]
Furthermore, since the coating agent contains a mixture of silica sol having an average particle diameter of 10 to 30 nm and silica sol having an average particle diameter of 50 to 500 nm, it can reliably prevent dry cracking of the coating mold. It is possible to reduce defective products.
[Brief description of the drawings]
FIG. 1 shows a cross-sectional view of a mold when casting is performed by a full mold casting method according to an embodiment of the present invention, and FIG. 1 (a) is a coating used in the full mold casting method according to an embodiment of the present invention. A partially enlarged sectional view of the mold is shown.
FIG. 2 is a sectional view of a mold when casting is performed by a conventional full mold casting method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Mold 11 Disappearance model 13 Coating mold 14 Cast frame 16 Foundry sand 17 Molten metal 18 Spout 19 Runway

Claims (3)

A full mold casting method comprising forming a coating mold with a coating agent comprising a refractory aggregate composed of fused silica, graphite and clay, water, and silica sol having an average particle diameter of 10 to 30 nm. The full mold casting method according to claim 1, wherein the silica sol contains 4 to 10%. The full mold casting method according to claim 1, wherein the coating agent contains a mixture of silica sol having an average particle diameter of 10 to 30 nm and silica sol having an average particle diameter of 50 to 500 nm.

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