JPH07164102A - Sand mold for casting and its manufacture - Google Patents

Abstract

PURPOSE:To provide a sand mold for casting having excellent pressure resistance and high temp. resistance and enabling correspondence to complicate shape by impregnating pulverized refractory into gaps between molding sands and binders in the sand mold for casting. CONSTITUTION:In the sand core, the gaps 22 exist between the molding sands 20 and the binders 21 composed of thermosetting resin for bonding the molding sands 20. This sand core is arranged in a furnace to press-fill impregnant 2 into the gaps 22. This impregnant 2 is composed of a mixed material of the pulverized refractory of mullite fine powder, silica fine powder, etc., and inorganic series liquid material of water glass, etc. By this method, the deformation caused by molten metal pressure at the time of casting under the high pressure is little and this core mold can resist the high temp. and can be applied even to the core in a low pressure casting and a gravity casting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting sand mold suitable for high pressure casting such as die casting and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a technique for preventing deformation of a core used in a die casting method in which a light alloy melt is filled in a cavity at high speed and high pressure, due to the melt pressure,
The following three methods are known.

(1) Two or three coat type layers are provided on the surface of the core (see Japanese Patent Laid-Open No. 63-309350).

(2) The core material is changed to a metal material such as iron particles and steel particles, and accordingly, the core manufacturing method is changed from the shell mold method to the pressure molding method.

(3) The binder that binds the foundry sand of the sand core is changed.

In the methods (1) and (3), the sand core, which is widely used at present, is improved to ensure pressure resistance and prevent "insertion" of molten metal. The method 2) is to mold the core using a material that is completely different from the conventional one.

[0007]

However, even when the above methods (1) and (3) are adopted, a binder, which is generally composed of a thermosetting synthetic resin, which binds the aggregate of the core, is used. Since the caking force is lost at a high temperature, the strength of the portion of the core that has come into contact with the high-temperature molten metal is reduced, which causes the dimensional accuracy of the cast product to be remarkably deteriorated.

Further, the above method (2) is not only expensive but also has a problem in that it cannot cope with a complicated shape as compared with sand in terms of quality.

In view of such circumstances, the present invention provides a sand mold for casting, which has excellent pressure resistance and high temperature resistance, can cope with complicated shapes, and can be manufactured at low cost, and a method for manufacturing the same. The purpose is to

[0010]

The sand mold for casting according to the present invention is characterized in that voids existing between the foundry sand and the binder of the foundry sand are impregnated with a fine powder refractory material. It is what

The fine powder refractory is made of, for example, mullite fine powder, silica fine powder, etc., and ceramic fine powder may be mixed therein.

Further, in the method for manufacturing a sand mold for casting according to the present invention, a sand core formed by molding sand and a binder of the molding sand is placed in a closed furnace, and the furnace is vacuumed. After that, the furnace is filled with an impregnating agent containing fine powder refractory, and then the inside of the furnace is pressurized to add the impregnating agent to the voids existing between the molding sand and the binder. It is characterized by being impregnated.

[0013]

The operation and effect of the present invention is such that the sand mold for casting according to the present invention is a high-pressure cast because the voids existing between the foundry sand and the binder of the foundry sand are impregnated with fine powder refractory. There is little deformation due to molten metal pressure at the time, and it can withstand high temperatures, and it is effective not only in the field of high pressure casting but also in cores in low pressure casting and gravity casting.

By mixing the fine ceramic powder with the fine powder refractory, there is no possibility that the disintegration property of the core will be deteriorated.

Further, according to the method for producing a sand mold for casting according to the present invention, it is possible to easily impregnate the voids existing between the foundry sand and the binder of the foundry sand with the fine powder refractory material. it can.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic view of an impregnating apparatus applied for carrying out the method for manufacturing a sand mold for casting according to the present invention. In the figure, reference numeral 1 is a closed impregnation furnace, and a conduit 4 communicating with an impregnating agent container 3 containing an impregnating agent 2 is provided in the impregnating furnace 1.
, A conduit 6 communicating with the vacuum pump 5 and a conduit 8 communicating with the compressed air source 7 are connected. Each conduit 4, 6, 8
Valves 9, 10 and 11 are provided in each.

The impregnating agent 2 is composed of a mixture of a fine powder refractory material such as mullite fine powder and silica fine powder and an inorganic liquid material such as water glass. Also this impregnating agent 2
In addition, fine ceramic powder such as alumina may be mixed.

Next, a method of impregnating a sand core using this impregnating apparatus will be described.

First, the sand cores 12 and 13 to be impregnated are placed in the furnace 1 with the valves 9 to 11 all closed. The sand cores 12 and 13 before the impregnation treatment are shown in FIG.
As shown in (a), a void 22 is present between the molding sand 20 and a binder 21 made of a thermosetting resin that binds the molding sand 20. The inside of the furnace 1 is controlled to a temperature at which the binder of the sand cores 12 and 13 is not sufficiently cured (about 100 to 120 ° C.), whereby the impregnating agent 2
Liquidity is also secured.

After the valve 10 is opened to evacuate the furnace 1 and the valve 10 is closed again, the valve 9 is opened to fill the furnace 1 with the impregnating agent 2. Then, after the valve 9 is closed and the valve 11 is opened to pressurize the furnace 1 to a pressure of about 3 to 4 kgf / cm ² , as shown in FIG.
The impregnating agent 2 is filled in the voids 2 and 13.

By filling the space 22 with the impregnating agent 2, the sand cores 12 and 13 have a structure which is less likely to be deformed by the molten metal pressure during high pressure casting and can withstand high temperatures.

[Brief description of drawings]

FIG. 1 is a schematic view of an impregnating apparatus applied for carrying out a method for manufacturing a sand mold for casting according to the present invention.

FIG. 2 is an explanatory view showing the structure of the sand core before and after the impregnation treatment.

[Explanation of symbols]

 1 Impregnation furnace 2 Impregnating agent 3 Impregnating agent container 4, 6, 8 Conduit 5 Vacuum pump 7 Compressed air source 9, 10, 11 Valve 12, 13 Sand core 20 Cast sand 21 Caking agent 22 Void

Claims (3)

[Claims] 1. A sand mold for casting, characterized in that a fine powdery refractory material is impregnated into the voids existing between the molding sand and the binder of the molding sand. 2. A sand mold for casting according to claim 1, wherein ceramic fine powder is mixed into the fine powder refractory material. 3. A sand core formed by molding sand and a binder for the molding sand is placed in a closed furnace, the inside of the furnace is evacuated, and then a fine powder refractory material is placed in the furnace. It is characterized in that it is filled with an impregnating agent containing, and then the inside of the furnace is pressurized to impregnate the impregnating agent into the voids existing between the casting sand of the sand mold and the binder. A method for manufacturing a sand mold for casting.