JPS6224850A - Method and apparatus for blowing inert gas to low-pressure casting machine - Google Patents

Abstract

PURPOSE:To inexpensively execute uniform blowing with ease of cleaning and inspection and simple construction in low-pressure casting by bottom pouring under pressurization by interposing a sprue plate constituted by assembling a thin vent path in the juncture between a pouring pipe and metallic mold and blowing an inert gas into the sprue. CONSTITUTION:A sprue plate 6 fastened to the sprue 9 of the metallic mold 5 is pressed via a heat-resistant packing to the flange part at the top end of an auxiliary pouring pipe 8 connected onto the pouring pipe 4. The inert gas fed by the pipe 13 is ejected from an annular groove 21 of the plate 6 through the vent path 23 constituted of the many thin grooves into the sprue 9. The mechanism is thereby simplified and the cleaning and inspection are made easy.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a low-pressure casting machine that is applied to casting metals such as aluminum and magnesium, and their alloys, and in particular, the present invention relates to a low-pressure casting machine that is applied to casting metals such as aluminum and magnesium, and alloys thereof, and particularly to The present invention relates to a method and apparatus for injecting an inert gas to replace an active atmosphere in a mold and a hot water supply pipe with an inert gas to prevent formation and oxidative combustion.

[Prior art]

Conventionally, as a method of preventing the generation of oxides and oxidative combustion in the mold and hot water supply pipe in a low-pressure casting machine, there is a method of providing an inert gas reservoir at the bottom of the sprue as shown in FIG.
A gas filtration system as disclosed in Japanese Patent Publication No. 52-113325 is known.

In the method of providing an inert gas reservoir B at the lower part of the sprue A shown in FIG. If there is insufficient pressurization time to obtain a good quality casting before the sprue A part, and if a leak occurs in the inert gas supply piping or the valve E installed there, the inert gas There is a problem in that molten metal enters the pool B and piping, and the function stops after that.

In addition, the method disclosed in Japanese Patent Publication No. 52-113325 requires complicated and expensive equipment, and the pressure difference between the molten metal pressurization pressure and the pressure in the inert gas pressure chamber is delicately controlled. The problem is that it is difficult.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned conventional problems, and it is not necessary to provide an inert gas reservoir or a pressure chamber near the sprue, and sufficient pressurization time can be obtained to obtain good quality castings. The object of the present invention is to provide an inert gas injection method and device for a low-pressure casting machine, which is not affected by leakage of piping, has a simple structure, and has a long service life.

[Structure of the invention]

The inert gas blowing method for a low pressure casting machine according to the first invention is as follows:
By blowing inert gas through a thin air passage that opens between the sprue and the hot water supply pipe, the inert gas is blown from the air passage to prevent the formation of oxides and oxidative combustion, and by making the air passage thin. It is characterized by a simple structure that prevents the intrusion of molten metal without providing an inert gas reservoir or pressure chamber.

Furthermore, the inert gas blowing device for a low-pressure casting machine according to the second aspect of the present invention has a plurality of thin ventilation passages that open at the circumferential surface of the sprue formed in the lower end of the member forming the sprue in the circumferential direction, and communicates with these ventilation passages. This is characterized in that an inert gas source is connected to the inert gas blowing hole so that the required amount of inert gas is uniformly and effectively blown from the point closest to the sprue.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In FIGS. 1 and 3, a crucible 2 containing molten metal 3 is arranged in a sealed container equipped with a heating device, and a hot water supply pipe 4 whose lower part is immersed in the molten metal 3 in the crucible 2 is placed. It penetrates the furnace 1 and projects upward. A mold 5 is arranged above the hot water supply pipe 4, and the lower end of the mold 5 is connected to the upper end of the hot water supply pipe 4 via a sprue plate 6, a heat-resistant packing 7, and an auxiliary hot water supply pipe. The sprue 9 is formed across the lower end of the mold 5 and the sprue plate 6. Compressed air is supplied into the furnace 1 from a pressure control device 10, and the furnace 1 is pressurized to push the molten metal 3 up through the hot water supply pipe 4 into the mold 5. An inert gas blowing hole 11 is formed in the sprue plate 6, and is configured to supply inert gas from an inert gas tank 12 as an inert gas source through an inert gas supply pipe 13. A solenoid valve 14 provided in a pipe 13 is controlled by a blow control device 15.

The inert gas tank 12 includes a CO2 gas cylinder 16 and an SF6 gas cylinder 1, for example, when casting magnesium.
7 is connected, and an N2 gas cylinder is connected during aluminum casting. When casting magnesium, a mixed gas consisting of CC)z gas and SFb gas mixed at a ratio of 50:1 is used.

Between the lower surface of the flange 4a at the upper end of the hot water supply pipe 4 and the upper surface of 1, there is a sprue plate 6 which absorbs thermal expansion and contraction of the auxiliary hot water supply pipe 8.
A bellows mechanism 18 is interposed for sealing between the auxiliary hot water supply pipe 8 and the auxiliary hot water supply pipe 8 via a heat-resistant gasket 7. Further, the mold 5 is installed and fixed on a lower fixed platen 20 by a mold surface plate 19.

As shown in FIG. 2, a sprue 9 is provided on the lower surface of the sprue plate 6
An annular groove 21 that communicates with the inert gas blowing hole 11 is formed at intervals radially outward from the circumferential surface of the annular groove 21, and a plurality of extremely shallow shallow grooves are formed in the circumferential direction from the annular groove 21 toward the radially inward side. The book is formed. With this sprue plate 6 installed,
A thin air passage 23 is formed in the shallow groove between the lower surface of the sprue plate 6 and the heat insulating packing 7. To give a specific numerical example of the size of this thin ventilation passage 23, the height is approximately 0.1
n+m, and the width is about several mm.

In the above structure, when starting casting, after the mold 5 has been closed, a signal from the blow control device 15 is sent to the solenoid valve 1.
4 is opened, and inert gas is supplied from the inert gas tank 12 to the inert gas blowing hole 11 of the sprue plate 6 via the inert gas supply pipe 13. Then, the inert gas is blown from the entire circumference of the inert gas blowing hole 11, through the annular groove 21, through the thin ventilation path 23, and into the lower end of the sprue 9, thereby increasing the activity inside the hot water supply pipe 4 and the cavity of the mold 5. The atmosphere is replaced with an inert gas. Set the time until the replacement ends using a timer. Next, when compressed air is supplied from the pressurization control device 10 into the furnace 1 to pressurize the inside of the furnace 1, the molten metal 3 begins to rise inside the hot water supply pipe 4. When the molten metal 3 reaches the auxiliary hot water supply pipe 8, the injection of inert gas is stopped. This control is performed by detecting the pressurizing force when the molten metal 3 reaches the auxiliary hot water supply pipe 8 using a pressure gauge. Thereafter, the cavity of the mold 5 is filled with the molten metal 3 by continued pressurization, and the mold is further pressurized for a predetermined period of time to cast a good quality casting. When the pressurization time has elapsed, pressurization is stopped and furnace 1
Return the inside to atmospheric pressure. Then, the molten metal 3 descends inside the hot water supply pipe 4 and returns to the inside of the crucible 2.

By restarting the blowing of the inert gas at the same time as this pressurization is stopped, the inert gas is sucked into the hot water supply pipe 4 when the molten metal descends, thereby facilitating the blowing. In addition, since the inside of the hot water supply pipe 4 is filled with inert gas, negative pressure does not occur inside the hot water supply pipe 4, and the sudden inflow of air into the hot water supply pipe 4 that occurs when the cast product is released from the mold is prevented. , the generation of oxides and oxidative combustion within the hot water supply pipe 4 are significantly reduced.

When casting is performed continuously, the inert gas injection restarted at the same time as pressurization is stopped, continues during chill time and when the mold is opened, closes the mold for the next casting, and then pressurizes and pours the molten metal. This inert gas is blown until the hot water supply pipe 3 reaches the auxiliary hot water supply pipe 8, and thereafter the above operation is repeated.

〔Effect of the invention〕

According to the inert gas injection method for a low-pressure casting machine according to the present invention, the inert gas is injected through the thin air passage that opens between the sprue and the hot water supply pipe, so the inert gas is effectively injected from the air passage near the sprue. It is possible to reliably prevent the formation of oxides and oxidative combustion within the hot water supply pipe and the mold cavity, and the thin ventilation path prevents the effects of leakage from the inert gas supply pipe. To reliably prevent the intrusion of molten metal without causing damage. In addition, there is no need to provide an inert gas reservoir or pressure chamber, and only the open end of the thin ventilation channel faces the vicinity of the sprue, so this area will not solidify first, and sufficient heat can be applied. This has the advantage that it is possible to take more pressing time and to obtain good quality castings.

Furthermore, the inert gas blowing device for the low pressure casting machine according to the present invention includes:
This is because it has a structure in which a plurality of thin ventilation channels are formed in the circumferential direction at the lower end of the member forming the gate, and an inert gas source is connected to the inert gas blowing hole that communicates with these ventilation channels. This provides an inert gas blowing device that is simple in structure, inexpensive, and has a long life, and also has the advantage of being able to uniformly blow in the required amount of inert gas from the location closest to the sprue.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a vertical sectional view of the main part, FIG. 2 is a sectional view of a sprue plate, FIG. 3 is a schematic diagram showing the overall configuration, and FIG. FIG. 4 is a vertical sectional view of the main part of the conventional example. 4 is a hot water supply pipe, 5 is a mold, 6 is a gate plate, 7 is a heat-resistant packing, 8 is an auxiliary hot water supply pipe, 11 is an inert gas blowing hole, 12 is an inert gas tank, and 23 is a thin ventilation path.

Claims (1)

[Scope of Claims] 1. A method for blowing inert gas into a low-pressure casting machine, which comprises blowing inert gas through a thin ventilation path opened between a sprue and a hot water supply pipe. 2. A plurality of thin ventilation passages opening at the circumferential surface of the sprue are formed in the circumferential direction at the lower end of the member forming the sprue, and an inert gas source is connected to the inert gas blowing hole communicating with these ventilation passages. Inert gas blowing device for low pressure casting machine.