JPS5831263B2 - Sand mold painting method and its equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to a sand mold coating method and an apparatus therefor.

Conventional sand molds for casting are made by filling green sand or self-hardening sand between the model and the frame or core metal, and after removing the model after pressure molding or hardening of the sand mold, the surface of the sand mold in contact with the model has a fire-resistant black or white color. This was then dried and integrated.

However, when the paint was applied, the average thickness caused unevenness, resulting in a sand mold with a dimensional error of several cylinders.

Also, defects such as deformation and cracking occurred during the drying stage.

There were also problems such as a large number of work steps and low thermal efficiency during drying.

For example, in Japanese Patent Publication No. 46-34779, a thermosetting resin and a curing catalyst as a good electrical conductor are mixed with casting sand, and the mixture is placed in a wooden mold, and electricity is generated between electrodes previously installed in the wooden mold. A method has been proposed in which a mold is rapidly hardened and molded by electrical resistance heating by applying electricity, but the problems caused by fire-resistant paint have not been solved at all.

The present invention is characterized by forming a heat-resistant paint layer on the conductive model, filling the space between the frame and the core metal with molding sand, and then electrically heating the model to transfer the paint film to the sand mold and integrate it. This method produces a hardened coating layer and a solidified sand mold that are faithful to the model dimensions.

Although the present invention uses a conductive model made of cast iron, for example,
In order to prevent adhesion due to reaction between the model material and the heat-resistant paint, it is recommended to use a mold release agent.

Furthermore, in the present invention, induction heating using commercial low-frequency or high-frequency current is used to dry and solidify the coating mold installed inside the conductive model, but induction heating of a sand mold is also possible. The effective proportion of heat required for drying is conventional radiation,
It is significantly more expensive than the convection drying method, saves a lot of labor for drying, and is preferable in terms of working environment and safety.

In addition, when performing repeated work, it is extremely important to control the temperature of the model before application to a constant level, but it is extremely suitable and useful for practical work to use a cooling method that can spray cooling water from a coil ring in conjunction with an induction heating method. It is.

The present invention will be explained below with reference to the drawings.

In the present invention, the core metal 12 is installed inside the model 10 according to the design,
The model 10 is made of a conductive material, for example cast iron.

A heat-resistant paint layer 11 is provided on the model 10. If the paint is black, the paint is made of carbonaceous material such as graphite mixed with an inorganic or organic binder and a solvent, and if the paint is white, alumina is used instead of the carbonaceous material. Magnesia, zirconia, etc. are used.

Its thickness is about 0.3 to 3X. As the mold release material, a much thinner extract, silicone, or resin film is used.

Depending on the shape and dimensions of the casting, the sand mold may be of any type as long as it can withstand one mocha of molten metal and maintain its exact dimensions until it solidifies.As a caking material, clay, water lath, cement, or organic caking material may be used. There is no problem in adding a third substance such as a curing agent.

These are determined by considering the environment, pollution, economy, workability, etc.

The molding sand 13 selected in consideration of the above points is filled between the core metal 12 and the model 10.

In the present invention, the outer periphery of the conductive model 10 is connected to the induction coil 16.
A heating device is provided which is surrounded by a heating device.

The induction coil 16 may be energized by a commercial low frequency or high frequency current, and is not particularly limited.

FIG. 2 shows an enlarged view of the main parts of the device of the present invention. A cooling water spray ring 14 surrounding the conductive model 10 is provided, and a slit 15 is carved in the ring (on the outer wall of the mold 10). Make it oriented.

This cooling device is preferably used in the same framework as the heating device of the conductive model described in 1) above.

In the seventh invention, a heat-resistant paint is sprayed, brushed or mechanically applied on the model, then filled with molding sand, and after the paint is brought into close contact with the model, the model such as a mold is heated by electric induction to rapidly raise the temperature. The paint is heated, the heat transfer dries and solidifies the paint, and it becomes integrated with the sand mold...), and when the model is removed, a sand mold can be created with a solidified coating layer faithful to the model dimensions.

Therefore, you can start casting work in a short time and find high quality castings.

Furthermore, since the above-mentioned model cooling mechanism is provided, the temperature of the model before paint application can be set constant during repeated fitting operations, and the heating rate and temperature by induction heating can be easily controlled.

Examples will be described below.

Example: Apply about 1 micron of mold release oil to the inner surface of the cast iron model shown in Figure 1, and then apply about 1% thick alcoholic paint containing 5 to 10% phenol resin and 95 to 90 graphite. Then, foundry sand containing 1.5% furfuryl resin and 0.3% sulfonic acid was filled between the core metal and the core metal.

When a current of 50 KW and 1000 Hz was applied to the coil, the temperature of the model reached 270°C in 3 minutes, and after being held for 10 minutes, the fireproof paint and sand mold solidified and became one body, and was cooled to room temperature in 2 minutes by spraying water.

When pulled out from the model, an extremely high quality core mold with almost no dimensional errors was obtained with a beautiful skin.

The time required has been cut in half.

This is placed in a separately made outer sand mold and 1350°C hot metal is cast to obtain a smooth casting.The dimensional accuracy is ±2% of the internal diameter of the conventional method where the sand mold is coated and dried. ±1%
As a result, the product value has increased significantly.

Experiments were also conducted with other binders, and similar accuracy was obtained in a short time.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the present invention, and FIG. 2 is an enlarged view of the main parts of the cooling device. 10: Conductive model, 11: Coating mold, 12 Two-core metal, 13: Foundry sand, 14: Cooling water spray ring, 15 Nislit,
16: Electric induction coil.

Claims (1)

[Scope of Claims] 1. After forming a heat-resistant paint layer on a conductive model and filling the space between it and the core metal with molding sand, the model is heated by electric induction to solidify the heat-resistant paint at an elevated temperature. A sand mold painting method that is characterized by being integrated. 2 A conductive model having a hot metal inside, an electric induction coil surrounding the outer periphery of the conductive model, and a cooling water spray ring, and a slit directed toward the model is carved in the cooling water spray ring. A sand mold painting device characterized by being equipped with a heating and cooling mechanism for conductive models.