JPH0233468B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a die casting method in which molten metal is injected and press-fitted into a cavity under reduced pressure.

Conventionally, as a method to eliminate mold cavities, especially air bubbles, from products, there is a vacuum die-casting method in which the inside of the cavity is evacuated and molten metal is press-injected into the cavity.
14515 and Special Publication No. 35-17810). In this method, a vacuum tank is installed in the intake port provided in the ejector box (dice mounting frame) behind the mold (movable die), which communicates with the inside of the cavity (die cavity) through the insertion hole of the extrusion pin (extrusion pin hole). After the connection is made, the air in the cavity is suctioned and removed through the gap between the extrusion pin and the insertion hole through the ejector box to create a vacuum inside the cavity, and molten metal is press-fitted into the cavity. It was made in a similar manner.

However, all the air in the cavity is suctioned and removed through the small gap between the ejector pin and the insertion hole, which is ensured so that the ejector pin can slide back and forth smoothly, and the vacuum inside the cavity is effectively created. It is extremely difficult to achieve a desired effect, and it is also time-consuming, resulting in a longer casting cycle (each cycle) of the die-casting machine, making it impractical.

In addition, in the case of Japanese Patent Publication No. 35-17810, since it is hardly possible to suction and remove air from the gap between the ejector pin and the insertion hole, the air that penetrates from the molten metal sump around the cavity toward the ejector box. A suction hole is separately provided, and a molten metal infiltration prevention pin, which is connected and supported on the ejector pin mounting plate in the same way as the ejector pin, is inserted into the air suction hole, and the air is inserted into the air suction hole to provide a molten metal infiltration prevention pin that is connected and supported by the ejector pin mounting plate, so that the air suction hole is inserted into the air suction hole. The air inside the cavity is effectively sucked out through the wide gap between the molten metal intrusion prevention pin and the air suction, but ensuring a wide gap like this means that the molten metal that has flowed into the molten metal sump will There is a danger that the molten metal will get into the gap and harden, and even more so because the gap generates suction force, there is a great risk that the molten metal will get in and harden. If the product is not extruded out of the mold smoothly and remains in the mold, or if the pins break, this is a major cause of failure.

Therefore, as a die-casting method that replaces the vacuum die-casting method, which has many problems, a gas atmosphere die-casting method has been proposed in which the air in the cavity is replaced with oxygen gas (reactive gas) (Japanese Patent Application Laid-Open No. 1983-1999- (See No. 86021 and Japanese Unexamined Patent Publication No. 8382/1983). In this method, the air inside the cavity is sucked out (vacuumed) using the air vent recess (reservoir) or vacuum passage formed around the cavity, and oxygen gas is sent into the sleeve and cavity from the plunger sleeve side. The molten metal is injected into the cavity in the gas atmosphere.

However, in order to fill the inside of the sleeve and the cavity with oxygen gas to achieve a gas atmosphere in this way by feeding oxygen gas from the plunger sleeve side, a large amount of oxygen gas is required. A large amount of oxygen gas is wasted, which increases the manufacturing cost of the product.

The present invention was made in view of the conventional die casting method, and the technical problem to be solved is the sealing of the mold parting line, etc., which is a problem in effectively creating a depressurized state in the cavity. The gap between the extrusion pin and the insertion hole (sliding part), where it is difficult and impossible to seal with a sealing material, is actually molded using oxygen gas, compared to the parts that can be sealed with a sealing material (compatible surfaces, etc.). The purpose is to provide a die-casting method in which the cavity is filled so as to flow in the direction of the cavity, and the pressure inside the cavity can be effectively and reliably reduced, thereby solving the problems of the conventional die-casting method.

In order to achieve the above-mentioned problems, the present invention has been developed by filling oxygen gas at atmospheric pressure or slightly higher than atmospheric pressure in the ejector box behind the mold in which the extrusion pin insertion hole is provided, and reducing the pressure inside the cavity. In this case, the supplied molten metal is press-fitted into the cavity.

Hereinafter, an example of the present invention will be described based on the drawings. 1 is a movable type, 2 is a fixed type, 3 is a cavity formed between both dies, 4 is a plunger sleeve, 5 is an ejector box, and 6 is a It is an extrusion pin. Further, 7 is a supply pipe for supplying and filling the ejector box 5 with oxygen gas, and 8 is an air vent pipe for evacuating the inside of the cavity 3 to a reduced pressure state.

The ejector box 5 is fixedly interposed behind the movable mold 1 in which the insertion hole 9 for the extrusion pin 6 is provided, and extends between the movable mold 1 and the movable platen 10, and has a surface portion that is compatible with the movable mold 1. and movable plate 10
Sealing materials 11 and 12 are interposed between the surfaces that are compatible with the fixation, respectively, and the oxygen gas is supplied into the ejector box 5 through the supply pipe 7, which is at atmospheric pressure or slightly higher than atmospheric pressure ( Approximately 1.1
The mold cavity is filled with oxygen gas to a pressure of about 100 psi (atmospheric pressure) so that the oxygen gas fills the gap between the extrusion pin 6 and the insertion hole 9 and flows in the direction of the mold cavity.

In the figure, 13 is a sealing material attached to the movable mold 1 and interposed in the mold parting lines of both the movable and fixed molds 1 and 2, and 14 is a casting sleeve that connects the plunger sleeve 4 to the cavity 3. 1
5 and a sealing material interposed between the fitting surfaces of the fitting holes 16 provided in the fixed mold 2.

In the die casting method of the present invention, the space between the ejector pin 6 and the insertion hole 9 is reduced by filling the ejector box 5 behind the movable mold 1 with oxygen gas at atmospheric pressure or slightly higher than atmospheric pressure in advance. The molten metal is filled with oxygen gas so that it flows in the direction of the mold cavity, and then the movable mold 1 and the fixed mold 2 are brought into close contact with each other and the molds are clamped in the same way as in the normal vacuum die casting method, and the molten metal is poured into the plunger sleeve 4. When the plunger piston 17 injects and advances to the position where it closes the hot water supply port 18, the air inside the cavity 3 is suctioned and expelled through the air bleed pipe 8 connected to a vacuum pump (not shown). The internal pressure is reduced and the molten metal in the plunger sleeve 4 is injected and press-fitted by the continuously advancing plunger piston 17.

Therefore, when the air inside the cavity 3 is suctioned and expelled to create a depressurized state inside the cavity 3, contact with the molten metal from the gap between the ejector pin 6 and the insertion hole 9 will not cause any harm and will not cause any chemical reaction with the molten metal. Since the oxygen gas that is consumed during the process is emitted, it is possible to manufacture products with fewer internal defects such as cavities.

As mentioned above, in the die casting method of the present invention, the ejector box, which is in communication with the inside of the cavity through the insertion hole of the ejector pin, is filled in advance with oxygen gas at atmospheric pressure or slightly higher than atmospheric pressure. Fill the gap with the insertion hole (the sliding part of the extrusion pin) with oxygen gas so that it flows in the direction of the mold cavity.
Since the pressure inside the cavity is reduced and the supplied molten metal is press-fitted into the cavity, when the air inside the cavity is suctioned out and the pressure inside the cavity is reduced, there will be no leakage from the gap between the ejector pin and the insertion hole. It is possible to manufacture products with few internal defects such as castings by pressurizing the molten metal into a cavity which is not harmful even if it comes into contact with the molten metal, and which causes a chemical reaction with the molten metal and generates consumed oxygen gas.

Therefore, according to the die-casting method of the present invention, the molten metal may enter the gap between the extrusion pin and the insertion hole and harden, leading to failure, or the oxygen gas per shot may be forcibly injected into the cavity and plunger sleeve. This solves the problem of the conventional method of wasting a lot of gas, effectively and reliably brings the inside of the cavity into a reduced pressure state, and makes it possible to manufacture products with fewer internal defects such as blowholes.

Thus, we were able to achieve our intended purpose.

[Brief explanation of drawings]

The drawing is a schematic cross-sectional view showing an embodiment of a die-casting apparatus according to the present invention. In the figure 1...movable type, 2...fixed type, 3...cavity, 4...plunger sleeve, 5...ejector box, 6...extrusion pin, 7...supply pipe, 8...air vent pipe, 9...insertion hole, 15... Plunger piston, 16...Hot water inlet.

Claims (1)

[Claims] 1 Fill the ejector box behind the mold with the insertion hole for the extrusion pin with oxygen gas at atmospheric pressure or slightly higher than atmospheric pressure, and reduce the pressure inside the cavity to allow the supplied molten metal to enter the cavity. A die-casting method characterized by press-fitting.