JPS603959A - Casting method - Google Patents

Abstract

PURPOSE:To prevent formation of cavities and roughening of a casting surface and to decrease a fraction defective by maintaining preliminarily the inside of a cavity in an evacuated state and evacuating forcibly the inside until the pouring is completed. CONSTITUTION:An evacuating blower 13 is driven to evacuate the inside of a cavity 3 and when a preset value is attained, the molten metal 18 in a ladle 17 is concentrically poured into a sweeping gate 14. A thin sheet 16 closing hermetically the pouring port is melted by the high temp. of the molten metal and the poured metal is filled through a pouring port 15 into a cavity 3. The evacuation and suction are performed by the blower 13 during the pouring period to discharge forcibly the gas, moisture, etc. generated in the cavity 3. The pouring is ended at the point of the time when the sheets 6, 7 closing hermetically the openings of riser gates 4, 5 are melted by the contact with the molten metal from the inside.

Description

[Detailed description of the invention] [Technical field of invention] This invention relates to a casting method.

[Prior art]

In conventional casting methods, for example, a fugitive model made of foamable resin is used, this fugitive model is buried in foundry sand in a mold flask, molten metal is poured into this, the temperature of the molten metal is raised, and the model is exposed to gas. There is a method of obtaining a cast product by volatilizing the molten metal and replacing it with a model in the cavity.In this method, the metal is poured by free gravity, so-called riser casting, and a large amount of gas generated when the model disappears is exhausted. requires a powerful exhaust system.

In general, in order to obtain a good cast product without cavities or defects on the casting surface, the permeability of the molding sand is important7, and the particle size distribution, relationship with the binder, and hardening strength during molding are important. In addition to managing the gas from inside the molded cavity, not only when a fugitive model is implanted as mentioned above, but also when using a regular wooden mold or metal mold. However, in the case of large castings in particular, if the permeability of the molding sand or forced exhaust is sufficient, the generated gas will remain in the cavity and cause damage to the inside and outside of the casting. This resulted in defects.

[Summary of the invention]

In view of these drawbacks of the conventional method, the present invention has been developed to
When pouring, the inside of the chamber is brought into a reduced pressure state in advance, and forced evacuation is continued until the pouring is completed, thereby making it possible to obtain a cast product with no internal or external defects.

〔Example〕

Hereinafter, one embodiment of the method of this invention will be described in detail with reference to the drawings.

FIG. 1 shows an overview of this embodiment method.

In FIG. 1, a casting mold is formed using molding sand in a mold flask consisting of a lower frame 1 and an upper frame 2 in the same manner as in the past. In other words, you have a cavity 3 in the shape of a product, communicate with the upper part of the cavity 3, have feeder ports 4 and 5 opened on the upper surface, and each opening is connected to a thin aluminum plate 6°7. Ring-shaped weight 8 that holds this down
, 9, and an exhaust port 10 is similarly opened at the upper surface of one side of the cavity 3, and a heat-resistant cup 11 is installed in close contact with the opening. Taber joint 12. An exhaust blower 13 is connected to the exhaust blower 13 via a heat-resistant hose 12b having Similarly, a thin aluminum plate 16 is applied and sealed.

After preparing the casting mold for molding in this way, in this embodiment method, the exhaust blower 13 is first driven to reduce the pressure inside the cavity 3, and when this reaches a preset steady value, the ladle is removed. When the 1T of molten metal 18 is concentratedly poured into the oyster salt 14, the thin &16 sealing the molten metal pouring opening is instantly melted by the high temperature of the molten metal, and the poured molten metal passes through the pouring port 15. The cavity 3 is filled. During the pouring period, the exhaust blower 13 suctions the exhaust gas, so that the gas and moisture generated in the cavity 3 are quickly and forcibly discharged, and the pouring is carried out through the openings of the feeder ports 4 and 5. The process ends when the thin plate 6.7 that seals the metal melts due to contact with the molten metal from the inside. 1 Looking at the cross section, it can be seen that the castings made by the conventional method have cavities as internal defects and cavities as external defects. However, with this method, these surface defects in the cavities 9 were eliminated, and a cast product with a solid internal structure and a smooth casting surface was obtained.

〔Effect of the invention〕

As detailed above, when using the method of the present invention, the openings such as the pouring port and feeder port that communicate with the cavity formed in the foundry sand are sealed and closed with a thin plate that is melted by the heat of the molten metal, and the molten metal is poured into the molding sand. At this time, the inside of this cavity is kept in a reduced pressure state in advance, and the forced exhaust is continued until the pouring is completed, so that the gas generated during casting can be completely removed from the cavity. There is no risk of gas getting into the molten metal and forming cavities inside the casting, or gas remaining on the surface of the molding sand on the inside of the cavity, causing defects on the outside of the casting or roughening of the casting surface. This can be achieved by reducing the defective rate and performing efficient casting.

[Brief explanation of the drawing]

The figure is a sectional view of a casting mold to which an embodiment of the casting method according to the present invention is applied. 1...Lower frame, 2...Upper frame, 3...Cavity, 4, 5...Riser mouth, 6, 7 and 16・φe・
Thin plate such as aluminum, 10, φ order, exhaust port, 11,
...Exhaust cup, No. 13...Exhaust momme blower, No. 15...
...Pouring port, 18...Molten metal. Patent applicant: Ube Industries Co., Ltd. Representative: Masaki Yama (and one other person)

Claims (1)

[Claims] It has a cavity molded in the molding sand in the mold flask, and this cavity has a feeder port and a pouring port communicating with each other, as well as an exhaust port, and each opening has a molding hole that can be melted by the heat of the molten metal. A casting method characterized in that the chamber is sealed and closed using a thin plate, and when pouring the molten metal, the inside of the cavity is maintained in a reduced pressure state through the exhaust port, and at the same time, the forced exhaust of the cavity 10 is continued until the pouring is finished. .