JPH01215433A - Manufacture of core for high pressure casting - Google Patents

Abstract

PURPOSE:To obtain a core having excellent pressure proof property with simple process by forming facing film on inner face of cavity in a pattern, packing sand for packing, reducing the pressure in the cavity with suction and hardening by high frequency heating. CONSTITUTION:The facing agent 3 is flowed into the cavity 2 in the pattern 1, and after uniformly sticking the facing agent 3 on the inner face in the cavity 2, the excess facing agent 3 is discharged, to form mica facing film 4. Successively, the packing sand 5 is packed and the pressure reduction and absorption is executed from opening 2a of the cavity 2. The mica facing film 4 is stuck with the packing sand 5 at high sticking density and at the same time, the flaking micas to each other are mutually and firmly stuck, to form close laminated layers. After that, the pattern 1 is charged into the high frequency heating furnace 8 and the packing sand 5 and mica facing film 4 are heated and hardened, to obtain the base core 9. After molding, the base core 9 is taken out from the pattern 1. By this method, the core having excellent pressure proof can be obtd. with simple process.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a core used in a high pressure casting method such as a die casting method.

(°Prior art) As a method for producing a casting core, for example, a method is known in which a cavity of a model is filled with filler sand, and then the sand is hardened by high-frequency heating (Japanese Patent Laid-Open No. 57-156860 and Japanese Patent Application Laid-open No. 61-71152), these molding methods involve spraying a liquid coating agent such as water glass in a mist onto the inner surface of the cavity of the model to form a coating film, and then Fluid filling sand is filled into the cavity in which the coating has been formed. Then, the filling sand in the cavity is irradiated with high frequency waves to heat and harden the filling sand, thereby molding the core.

According to this method, since fluidized sand is used as the filling sand and an inorganic binder is used as the mold coating agent, it is possible to produce a casting with a smooth casting surface. However, this method is not intended for manufacturing cores used for high-pressure casting such as die casting, so if the core obtained by this method is used for high-pressure casting, the
There is a problem in that the molten metal permeates into the mold coating layer on the surface of the core with a pressure of about 0 kg/d.

On the other hand, methods for manufacturing cores for high-pressure casting include, for example, JP-A-56-139256 and JP-A-58-12.
One disclosed in Japanese Patent No. 8245 and the like is known. In this method, a sand core is molded using an organic binder, a slurry consisting of an alkaline aqueous solution mixed with refractory powder and a water-soluble thermosetting resin is applied to the surface of the sand core, and this is dried. In this method, a first coating layer is formed, a solution containing synthetic mica is further applied to the surface of the first coating layer, and the solution is dried to form a second coating layer.

According to this method, a core with excellent pressure resistance is obtained, and since the surface of the core is coated with a solution containing synthetic mica, cranks or holes are not formed on the surface of the core. is prevented.

(Problem A to be Solved by the Invention) However, since this method requires two coating operations, there is a problem that the process becomes complicated and the manufacturing cost increases.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a method for manufacturing a core for high-pressure casting, which allows a core with excellent pressure resistance to be manufactured in a simple process.

(Means for Solving the Problems) In order to achieve the above object, according to the method for manufacturing a high-pressure casting core of the present invention, a water-soluble coating containing a mica-based substance or a scale-like substance is applied to the inner surface of the cavity of the model. a step of applying a molding agent to form a coating film, a step of filling the cavity with filler sand, and arranging an air-permeable substance that does not allow the filler sand to pass through the opening of the cavity, Consisting of a step of suctioning the inside of the cavity under reduced pressure, and a step of forming a coating layer of a mica-based substance or a scaly substance on the surface of the cured body of the filling sand by hardening the filling sand and the coating film by high-frequency heating. This is what I did.

(Function) After filling the cavity with filler sand, the inside of the cavity is vacuum-suctioned through the cavity opening, thereby improving the boundary adhesion strength between the filler sand and the coating layer of the mold coating agent. Furthermore, the mica or scaly substances contained in the mold coating agent adhere to each other, forming a coating layer in which these substances are densely laminated.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIGS. 1(a) to 1(f) show each manufacturing process of a core for high-pressure casting. First, the mold coating 3 is poured into the cavity 2 of the model 1 molded from a resin material such as silicone rubber with excellent heat resistance (Fig. 1(a)). 100 parts of natural mica below mesh,
This is a water-soluble coating agent obtained by adding 40 parts of 1% CMC (carboxymethylcellulose) and 1 part of water glass and thoroughly stirring the mixture.

After the mold coating agent 3 is uniformly adhered to the inner surface of the cavity 2, the excess mold coating agent 3 is discharged. As a result, a mica coating film 4 is formed (Fig. 1).

Subsequently, the cavity 2 in which the mica coating film 4 has been formed is densely filled with filling sand 5 (FIG. 1(C)).
100 parts of silica sand, 3 parts of water glass, 0.3 parts of water, 0 blowing agent
．． It is prepared by adding 3 parts of 0.03 parts and mixing and foaming with a mixer, and has fluidity.

After filling the cavity 2 with the filling sand 5 in this way,
The inside of the cavity 2 is vacuum-suctioned from the opening 2a of the cavity 2 (FIG. 1(d)). That is, the vacuum suction device 6 is connected to the upper part of the cavity 2, and the vacuum suction device 6 is connected to the upper part of the cavity 2.
A breathable material, specifically a wire mesh filter 7 of approximately 200 mesh, is attached to the opening 2a of the opening 2a to prevent the filling sand 5 from passing through during vacuum suction. Through this process, the inside of the cavity 2 is suctioned under reduced pressure without the filling sand 5 being discharged to the outside, and the mica coating film 4 is closely attached to the filling sand 5 with high adhesion strength. At the same time, flaky mica pieces in the mica coating film 4 also adhere firmly to each other, forming a dense laminate. Therefore, in this step, it is necessary to determine the vacuum suction conditions so that both the adhesion strength between the mica coating film 4 and the filling sand 5 and the density of the mica coating film 4 are improved.

Afterwards, the model 1 is placed in the high-frequency heating furnace 8 and heated to 2K.
The filling sand 5 and the mica coating film 4 are heated and cured by irradiating the high frequency of W for 4 minutes (Fig. 1(e)). This high frequency heating step is carried out while performing the vacuum suction described above. Good too.

In this way, the base core 9 as shown in FIG. 1(f) is molded. After the molding, the base core 9 is taken out from the mold base 1.

A mica coating film 4 formed on the inner surface of the cavity 2, that is, a coating layer IO made of a mica-based material is formed on the surface of the base core 9. As shown in an enlarged view in FIG. 2, it was confirmed that the filling sand 5 penetrated into the coating layer 10 and was integrated into the coating layer 10, and had an extremely high boundary adhesion strength.

The high-pressure casting core manufactured by the above process was set in a mold, and the pressing force was 500 kg/cd and the sprue speed was 0 and 1.
Pressure casting was carried out under conditions where m/see S molten metal temperature was 700°C. As a result, there was no breakage of the core, and since the surface of the core was smooth due to the coating layer of the mica-based material, 100% of the sand was removed by vibration alone.

In the above examples, the mica substances contained in the coating agent include muscovite, phlogopite, biotite, synthetic mica, etc., but are not limited to mica substances, and include, for example, metal flakes, etc. A coating agent containing a scaly substance may be used.
Furthermore, for example, 50 parts of natural mica, 50 parts of synthetic mica, 4 parts of water
It is also possible to use a coating agent having a composition of 0 parts of sodium sulfosuccinate, 10 parts of sodium sulfosuccinate and a few drops of antifoaming agent.

In addition, the filling sand is not limited to those having the above composition,
For example, 100 parts of flattery silica sand and 3 parts of water glass are mixed into 5 parts.
It is also possible to use kneaded sand that has been kneaded for a minute and then dried with hot air at 50'C, and then irradiated with a high frequency wave of 4 KW for one minute.

(Effects of the Invention) As explained above, according to the method for producing a high-pressure casting core of the present invention, a water-soluble mold coating agent containing a mica-based substance or a scale-like substance is applied to the inner surface of the cavity of the model. a step of forming a coating film, a step of filling the cavity with filler sand, and arranging an air-permeable substance that does not allow the filler sand to pass through the opening of the cavity, and sucking the inside of the cavity under reduced pressure through the opening. and a step of forming a coating layer of a mica-based substance or a scale-like substance on the surface of the filling sand by hardening the filling sand and the coating film by high-frequency heating, so the process is simple. Excellent pressure resistance,
It is possible to manufacture a core that prevents molten metal from penetrating the surface of the core due to the pressure applied during casting, and it is possible to use this core to manufacture cast products with a smooth casting surface. becomes.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram showing one embodiment of the method for producing a high-pressure casting core of the present invention, and FIG. 2 is an enlarged view of the surface of the obtained core. 1... Model, 2... Cavity, 3... Coating agent,
4... Coating film, 5... Filling sand, 6... Decompression suction device, 7... Filter (breathable material), 8... High frequency heating furnace, 9... Base core, 10 ...Coating layer. Applicant Mitsubishi Motors Corporation Agent Patent Attorney Kanji Nagato Figure 1 (Q) (b) (C) 2
figure

Claims (1)

[Claims] A step of applying a water-soluble coating agent containing a mica-based substance or a scale-like substance to the inner surface of the cavity of the model to form a coating film, a step of filling the cavity with filler sand, and a step of filling the opening of the cavity with breathability that does not allow the filling sand to pass through;
A mica-based substance or a scale-like substance is formed on the surface of the cured body of the filling sand by arranging the substance and vacuum suctioning the inside of the cavity through the opening, and hardening the filling sand and the coating film by high-frequency heating. A method for producing a core for high-pressure casting, comprising the step of forming a coating layer.