JPS63132760A - Gas venting method for high-quality die casting - Google Patents

Abstract

PURPOSE:To produce a high-quality die casting having extremely decreased gas inclusions in a vacuum die casting method by adequately changing over the evacuation in a die cavity to a vacuum evacuation system and atm. system. CONSTITUTION:A molten Al alloy M is poured from a pouring port 2 into an injection sleeve 1 and a tip 4 is advanced by a plunger 3 to start injection of the molten metal M. A gas venting part 7 of the die cavity 6 is held communicated with the atm. through a solenoid valve 11 at this time. The atm. system solenoid valve 11 is closed and a vacuum evacuation system solenoid valve 8 is opened to make force evacuation of the die cavity 6 by a limit switch 13 at the point of the time when the tip 4 advances to close the port 2. The valve 11 is opened and the valve 8 is closed to change over the system to the evacuation to the atm. system by the limit switch 13 when the filling of the molten metal into the cavity 6 is completed upon further advancing of the tip. The evacuation in the cavity 6 is thereby satisfactorily executed and the inclusion of the gas into the product part is minimized.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing high-quality mold castings, and in particular, when manufacturing aluminum alloy castings by the high-pressure 7 casting method typified by die casting. This invention relates to a degassing method that can reduce gas entrainment.

(Prior Art and Problems to Be Solved) Die-casting, which is a typical method of high-pressure casting, is known as a highly productive method that can manufacture cast parts in large quantities with high precision. However, especially for aluminum alloy casting,
Since the molten metal is injected into the mold cavity at high speed and under pressure, there is a problem in that the gas in the mold cavity is not sufficiently exhausted and remains compressed inside the product.

In order to deal with such problems, P-F die-casting method, G-F die-casting method, slow filling die-casting method, etc. have been developed, and the quality of 1m products has been significantly improved, but still. Therefore, a vacuum die casting method in which the inside of the mold cavity is forcibly evacuated has been developed and applied. However, even with this method, there is a problem that the exhaust inside the mold cavity is not necessarily sufficient and that the molten metal is sucked into the gas venting part and clogs it.

The present invention has been made in order to solve the problems of the prior art described above, and improves the vacuum die casting method to ensure that the inside of the mold cavity is sufficiently evacuated and the gas is not entrained in the product part. The object of the present invention is to provide a method that can produce high-quality aluminum alloy castings with extremely little amount of gas and without clogging caused by absorption of molten metal into the degassing section.

(Means for solving the problem) In order to achieve the above object, the present inventor investigated that the cause of the problem is that the conventional vacuum die casting method uses only a vacuum exhaust system forcibly exhausting gas. However, as a result of research into countermeasures, it was discovered that this can be achieved by appropriately switching between the vacuum exhaust system and the atmospheric system depending on the pressurized injection process.

In other words, the present invention produces aluminum alloy castings by pressurizing molten metal poured into an injection sleeve with a plunger tip and injecting it into a mold cavity with a small gas vent communicating with an atmospheric system or a vacuum depressurization system. In the degassing method during high-pressure casting, in the first step, molten metal is poured into the sleeve, and the degassing part is communicated with the atmosphere to prevent the exhaust from inside the sleeve until the plunger tip blocks the hot water supply port. In the second step, when the plunger tip blocks the hot water supply port, the gas venting section is communicated with the vacuum decompression system, and the communication between the gas venting section and the atmosphere is cut off to force the exhaust inside the mold cavity. The third step is to cut off the communication between the degassing part and the vacuum depressurization system immediately before or after the completion of filling the mold cavity with the molten metal, and to vent the gas by communicating the degassing part with the atmosphere. The gist of this paper is a method for degassing high-quality mold castings.

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

FIG. 1 shows an example of a die-casting apparatus used to carry out the method of the present invention.

As mentioned above, in the case of normal die casting, there is a pouring process in which molten aluminum is poured into the injection sleeve from the pouring hole,
Casting is performed by an injection process in which molten metal in an injection sleeve is pushed into a mold cavity by the advancement of a tip attached to a plunger, but this method inevitably involves gas entrainment into the product.

Therefore, in vacuum die casting, in order to avoid this, a shut-off valve that communicates with the gas vent is provided, and the vacuum pump and shut-off valve are linked, so that when the pouring port is blocked with a chip, the shut-off valve is opened to communicate with the vacuum evacuation system to forcibly exhaust the inside of the mold cavity, and then, just before the molten metal filling is completed, the shut-off valve is closed to prevent molten metal from entering the shut-off valve section. but.

After pouring the molten metal, the exhaust inside the mold cavity until the chip closes the pouring port, and the exhaust inside the mold cavity from just before the completion of filling the molten metal until the completion of filling the molten metal.

This is not done because the shut-off valve is closed, which causes gas to be drawn in and hot water to stop flowing.

In the present invention, in order to avoid such inconvenience, the first
As shown in the figure, a circuit communicating with the vacuum exhaust system and the atmosphere system is installed in the gas venting part, and a switching valve such as a solenoid valve is installed at the end of each, in short, the mold cavity is forced to open by the vacuum exhaust system. The degassing section is communicated with the atmosphere except when the gas is being exhausted, allowing sufficient degassing even at the end of the pouring process and the injection process.

This will be explained with reference to FIG. In the figure, reference numeral 1 denotes an injection sleeve, which is provided with a spout 2 at its rear end, and a tip 4 at the tip thereof can be slid within the injection sleeve by the operation of a plunger 3.

The front end of the injection sleeve 1 communicates with a mold cavity 6 formed in a mold 5, a gas venting part 7 is connected to the mold cavity 6, and a circuit communicating with an atmospheric system and a vacuum exhaust system is connected to this. It is connected.

A vacuum link 9 is connected to the vacuum exhaust system circuit via a solenoid valve 8.
A vacuum pump 10 is provided, and a solenoid valve 1 is provided in the atmospheric system circuit.
1 is provided. Each solenoid valve 8.11 is actuated by a limit switch 13 which can engage a limit bar 12 mounted on the plunger 3.

Next, the operation of the die casting apparatus will be explained.

First, the tip 4 of the plunger 3 is moved backward, and the molten aluminum alloy M is poured into the injection sleeve 1 from the molten spout 2. After pouring, the tip 4 is moved forward to start injecting the molten metal, but since the solenoid valve 11 for the atmosphere system is normally open and the solenoid valve 8 for the vacuum exhaust system is closed, the gas venting section 7 is closed to the atmosphere. The mold cavity 6 is evacuated through communication with the mold cavity 6.

This is the first stage of degassing.

When the tip 4 moves forward and blocks the pouring port 2, the limit switch 13 closes the solenoid valve 11 in the atmosphere system to cut off the communication between the gas venting section 7 and the atmosphere, and at the same time closes the solenoid valve 11 in the vacuum exhaust system. 8 is opened to communicate the gas venting section 7 with the vacuum exhaust system, and the mold cavity 6 is forcibly evacuated. This is the second stage of evacuation.

Immediately before or after the tip 4 advances further and the filling of the molten metal into the mold cavity 6 is completed, the limit switch 13 is activated.
The solenoid valve 11 of the atmosphere system is opened to communicate the gas venting part 7 to the atmosphere, and at the same time, the solenoid valve 8 of the vacuum exhaust system is left open to cut off the communication between the gas venting part 7 and the vacuum exhaust system, and the gas venting part 7 is opened. Part 7 is evacuated until the molten metal filling is completed. This is the third stage of degassing. In this case, the gas venting section 7 is communicated with the atmosphere and gas is vented just before or after the completion of filling the molten metal.
There will be no gas entrainment or hot water leakage into the product.

FIGS. 2 and 3 show another modification of the die-casting apparatus shown in FIG. 1, in which the degassing section 7 branches off and the circuit communicates with the atmospheric system and the vacuum exhaust system. A shutoff valve 14 is provided at each point.

When the shut-off valve 14 is advanced by the pneumatic cylinder 15, it allows the gas vent section 7 to communicate only with the vacuum exhaust system, and when it moves backward, it allows the gas vent section 7 to communicate only with the atmospheric system. - The switch 13 operates in synchronization with the operation of the solenoid valves 8 and 11.

When the shut-off valve 14 is provided in this way, it is linked to the exhaust of the vacuum exhaust system, so that molten metal flows from the degassing section 7 into the piping of the vacuum exhaust system from just before the completion of filling the molten metal until the completion of filling the molten metal. can be reliably prevented from entering.

This point is different from the function of conventional shut-off valves.

(Example) Using the die-casting apparatus shown in FIG. 1, a molten metal of ADC12 alloy (12 types of aluminum alloy die-casting) was cast by high-pressure casting according to the above three-step degassing procedure to manufacture an aluminum alloy cylinder block. .

For comparison, cylinder blocks were manufactured by casting the above molten metal by conventional ordinary die casting method and vacuum die casting method.

After casting, each cast product was subjected to T6 treatment and quality investigation (appearance, pressure test, product gas amount) was conducted. The result is the first
Shown in the table.

As is clear from Table 1, the vacuum die-casting method improves the appearance and pressure resistance after heat treatment compared to the ordinary die-casting method, and in particular reduces the amount of product gas. Since gas entrainment can be significantly reduced compared to the method, the amount of gas in the product can be further reduced without the generation of blisters, and the appearance after heat treatment can also be improved. It was also confirmed after casting that no molten metal had entered the vacuum exhaust system piping during injection.

(Effects of the Invention) As described in detail above, according to the present invention, degassing in the high-pressure casting method is performed by appropriately switching between the atmospheric system and the vacuum exhaust system that communicate with the degassing section, so the pouring process Furthermore, sufficient degassing can be carried out even at the end of the injection process, and high-quality aluminum alloy castings with extremely low gas entrainment can be produced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a die-casting device used for carrying out the method of the present invention, FIG. 2 is an explanatory diagram showing a modification of the above die-casting device, and FIG. 3 is an enlarged detailed view of section A in FIG. 2. be. DESCRIPTION OF SYMBOLS 1...Injection sleeve, 2...Pouring port, 3...Plunger, 4...Tip, 5...Mold, 6...
Mold cavity, 7... Gas venting section, 8... Solenoid valve (vacuum exhaust system), 9... Vacuum tank, 10... Vacuum pump, 11... Solenoid valve (atmospheric system), 12 ...Limit bar, 13...Limit switch, 14...
・Shut-off valve, 15...Pneumatic cylinder, M...
・Molten metal. Patent applicant Hisashi Nakamura, patent attorney representing Kobe Steel, Ltd. Figure 3

Claims (1)

[Claims] The molten metal poured into the injection sleeve is pressurized by a plunger tip, and then injected into a mold cavity equipped with a gas vent that communicates with the atmospheric system or vacuum depressurization system. In the venting method, as a first step, molten metal is poured into the sleeve, and until the plunger tip blocks the hot water supply port, the gas venting part is communicated with the atmosphere to exhaust the inside of the sleeve, and as a second step, When the plunger tip closes the hot water supply port, the gas venting section is communicated with the vacuum decompression system, and the communication between the gas venting section and the atmosphere is cut off to forcefully exhaust the inside of the mold cavity, and the third A high-quality mold casting characterized in that, as a step, immediately before or immediately after the completion of filling the mold cavity with molten metal, communication between the gas venting section and the vacuum decompression system is cut off, and the gas venting section is communicated with the atmosphere to perform exhaust. How to release gas.