JP3349237B2 - Model coated with coating agent for vanishing model casting and its coating agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a model coated with a coating agent used for vanishing model casting, and a coating agent for the model.

[0002]

2. Description of the Related Art A coating material is used for discharging gas generated from a disappearing model and improving the surface roughness of a casting surface.

Conventionally, aggregates having a large particle size have been used when it is desired to improve the permeability of generated gas, and aggregates having a small particle size have been used when emphasizing surface roughness.

[0004] However, when the grain size of the aggregate is increased, the surface roughness of the casting surface is deteriorated. Therefore, there is a contradiction between the gas permeability and the improvement of the surface roughness.

[0005] For this reason, a conventional coating material obtained by mixing approximately equal amounts of aggregates of various sizes is used as a half of the above two functions.

[0006]

SUMMARY OF THE INVENTION The present invention focuses on the point that the gas permeability can be improved even when aggregate having a small particle size is used. This is a completely different idea from the conventional idea of making an effort to prevent cracks from occurring after application. The purpose is to obtain a model and a coating agent for the model.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks and is characterized by a model for vanishing model casting, wherein the coating agent applied to the surface of the model is formed by applying the coating agent.
The difference in the particle size of the constituent aggregates is
Have been made to alter the distribution, when drying the coating material, smooth the small particles as well as implement the degassing from the crack site without such fine cracks in the coating agent in an appropriate amount generated A model coated with an application agent for vanishing model casting, which has a structure that makes the casting surface finer by protecting it with natural skin.

[0008]

According to the present invention, fine cracks are generated by providing a difference in the particle size of the aggregate constituting the coating agent and changing the distribution of water in the coating agent. In other words, when the coating material is dried, the necessary amount of water penetrates from the vicinity of the small-grain aggregate having a large amount of moisture and the wrinkles and cracks do not occur in the vicinity of the large-grain aggregate dried first. I do.

On the other hand, cracks occur in the vicinity of the aggregate having a small particle size, which is later dried, because the water is not replenished with an appropriate amount of the evaporating water and the water rapidly shrinks. This crack is a small crack because it is near the aggregate having a small particle size.

The crack serves as a gas passage during pouring, and the gas permeability is greatly improved.
In addition, the surface roughness of the casting surface is dramatically improved by the protection of the small particles by the smooth skin.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described with reference to FIGS.
FIG. 1 is a partial sectional view showing a use state in which a molten metal 2 is poured using a model 1 coated with a coating material 3 of the present invention.
In FIG. 1, a coating material 3 is applied to the surface of a foamed model 4 and then dried. The molten metal 2 is poured from a gate (not shown) and proceeds while the model 4 is gasified. It is discharged through fine cracks 6 generated in the coating material 3.

FIG. 2 is a partially enlarged view schematically showing part A shown in FIG. The coating material 3 is obtained by adding an additive and a solvent to a binder such as clay in addition to the aggregate and kneading the same, and a number of cracks are scattered on the dried surface as shown in FIG. I understand. Since the amount of water adhering to the surface of each aggregate is different due to the difference in particle size when the coating material is dried, the distribution of water occupying the surface area of the coating material 3 is not uniform, and the vicinity of the aggregate 8 having a large particle size is small. A state where the water content is low occurs. For this reason, a difference occurs in the drying time, and a number of fine cracks 6 are generated near the aggregate 7 having a large amount of water and a small particle size to be dried later. The maximum length of the crack was about 500 μm.

FIG. 3 is a table comparing the particle size distributions of the coating material 3 according to the present invention and the conventional product, wherein the aggregate having the smallest particle size of 280 mesh or less has 69.5% (weight percent). You can see it occupies.

FIG. 4 is a graph comparing the air permeability when the above two types of coating agents are used. The air permeability is inversely proportional to the film thickness of the coating agent in the case of the conventional product, but the coating agent 3 according to the present invention is around 100, which is the most frequently used coating agent.
When the film thickness was 2 to 0.5 mm, the air permeability was about twice that of the conventional product.

When the strength of the coating agent is required, the coating is applied twice in order to increase the thickness of the coating agent. However, the rate of decrease in air permeability is extremely small as compared with the conventional product.

As a material of the aggregate, SiO ₂ is usually used in a large amount, but in order to further improve the surface roughness of the casting surface,
It is desirable to use a mixture of Zr sand or Al ₂ O ₃ having high seizure resistance.

[0017]

According to the above-mentioned structure, a model coated with a coating agent having improved surface roughness of the casting surface and improved gas permeability can be obtained. Gas defects that enter the product can be eliminated.

Further, since the proportion of aggregate having a small particle size is large, the workability of applying to the model is improved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a use state of a model coated with a coating agent according to the present invention.

FIG. 2 is a partially enlarged view schematically showing a portion A in FIG. 1;

FIG. 3 is a table comparing the particle size distribution of aggregates between the coating composition according to the present invention and a conventional product.

FIG. 4 is a graph comparing the air permeability of a coating agent according to the present invention with a conventional product.

[Explanation of symbols]

 1 ... Model coated with coating agent 3 ... Application agent 4 ... Model 6 ... crack

Claims (2)

(57) [Claims] 1. A model for casting a vanishing model, wherein the coating material applied to the surface of the model has a particle size of an aggregate constituting the coating material.
To change the distribution of water in the coating agent.
Have been made to, when drying the coating material, in form as fine cracks in the coating agent in an appropriate amount generated protection smooth skin small particles with implementing the degassing from the crack site A model coated with an application agent for vanishing model casting, which has a structure that makes the casting surface fine. 2. A method for applying a coating on the surface of a model used for vanishing model casting.
A that the coating agent, the particle size distribution of the coating agent, the entire 10
When the weight is 0% by weight, 3 to 8% by weight of 100 mesh or more, 12 to 37% by weight of 100 to 280 mesh, 6% of 280 mesh or less.
Coating agent for a vanishing model casting model constituted in a ratio of 0 to 80% by weight.