JPS5832564A - Vacuum casting method - Google Patents

Abstract

PURPOSE:To prevent misrun and blowholes by suspending a down tube into the molten metal in a crucible, connecting the down tube and the sprue of dies airtightly and evacuating the inside of the dies. CONSTITUTION:Molten metal which is a light alloy is put in a crucible 10, which is placed in a heat insulating furnace 9. A down tube 14 is suspended through the hole of a cover 13 into the molten metal, and is butted and fixed concentrically with a nozzle 15 and a sprue 17 by means of a lift 8, whereby these are held mutually airtightly. A bottom part 16 and a top part 18 are pressed to each other by a sliding ram 4 which is moved downward by the pressure of a downward forcing cylinder 6. At this same instant, a vacuum chamber 19 descends as well and abuts on a bottom surface 20 airtightly. The air in the chamber 19 is sucked to reduce the pressure in the dies 16, 18 down below the atmospheric pressure and to release the pressure in the chamber 9 to the atmosphere. The molten metal is passed through the tube 14 and the nozzle 15 and is forced into the engraved cavities in the dies 16, 18 by the differential pressure between the vacuum and the atmospheric pressure, whereby the molten metal is cast.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to low-pressure differential casting in metal lid casting of light alloys such as aluminum alloys.

In the conventional low-pressure casting method, the pressure inside the crucible is reduced to atmospheric pressure or 0.
The molten metal is pushed up under a high pressure of 5 to 0.9 kl/an, and then poured into the mold for casting.The flow of the molten metal at this time removes the air vibrations in the metal lid and the generated gas through the gas vent hole in the mold. When extruding the molten metal from the molten metal to the outside of the metal part, the exhaust resistance may obstruct the flow of the molten metal depending on the air volume inside the metal lid and the inflow speed of the molten metal. This invention has been made to solve this problem, and provides a low-pressure casting method using a differential pressure between DK vacuum low pressure and atmospheric pressure instead of low pressure pressurization.Hereinafter, the present invention will be explained. The details will be explained with vague reference to the drawings.

The figure shows an outline of the structure of the equipment for carrying out the method of the present invention. In a fist training session, a pedestal holder 2 is installed, a platen 3, a slide ram 4 and a head plate 5 are installed.
are assembled. A lower pressure cylinder 6 is provided on the head plate 5, and its piston lower door is connected to the slide ram 4. PayPl and platen 3
A heat-retaining furnace 9 is placed between the two via a lift 8.

The heat-retaining furnace 9 has a crucible 1o placed thereon via a heat-insulating material 11, and a heat-retaining heater 12 is provided around the crucible 10.0. The upper part of the heat insulating furnace 9 is covered with a nozzle 1113], and a nozzle 14 is suspended in the center of the furnace 9 into the molten metal of the crucible 100.
Bottom on platen 3 through 5! ! It is brought into contact with the sprue 17 of 116.

The upper surface of the lower ml 6O and the lower surface of the upper portion 18 are engraved with a pattern of the mold workpiece. A vacuum m19 is provided around the upper part 18, and the lower wall surface 20 forming the vacuum chamber 19 is in airtight contact with the lower part W16. The vacuum chamber 19 is provided with a vacuum pump 21 connected to a vacuum pump (not shown).In addition, an air supply pipe 22 is opened in the lid 13 of the heat-retaining furnace 9.

In the apparatus configured as described above, the method of the present invention is carried out as follows. That is, after placing the molten metal in the crucible 10 and placing it in the insulating furnace 9, the munch -214 is set by hanging into the molten metal through the hole in the lid 13, and the nozzle 15 is made concentric with the sprue 17 of the lower mold 16. In this manner, the heat insulating furnace 9 is lifted upward by the lift 8 and fixed by abutting against each other.

In this case, the downch -114, the nozzle 15 and the sprue 17 are kept airtight from each other.

The lower die 16 and the shed 18 are pressed against each other by the lowering of the slide ram 4 by the pressure of the lower cylinder/6, and the vacuum chamber 19 is simultaneously lowered and brought into airtight contact with the lower surface 20. In this case, heat-resistant /4
．． It is recommended to use King etc.

After doing this, the pressure inside the gold W 16° 18 is brought to below atmospheric pressure by suctioning the air inside the vacuum chamber 19 with a vacuum pump, and the pressure inside the insulating furnace 9 is kept open to the atmosphere. Due to the pressure difference between the vacuum pressure and the atmospheric pressure, the molten metal is forced upward through the downch, through the pipe 14 and the nozzle 15, and into the engraving space in the metal 16, 18 to form a hook shape.

When the molten metal fills 1 g of gold III and is cooled and solidified, the vacuum pressure is released to atmospheric pressure, and the top wi
If g is increased, the molten metal is less than 17 parts of the sprue is 10 parts of the crucible.
descend inward. The hooks are then demoulded and deposited.

In the mold of the method of the present invention, the pressure for pushing up the molten metal is atmospheric pressure and is based on a vacuum differential pressure, so the downchip m21
4, the nozzle 1s, and the sprue 17, the pressure of the rising bath water and the outside air pressure are the same or smaller, so there is no risk of molten metal leaking (and stable operation is guaranteed). .

In addition, when pouring molten metal, the gas generated by contact with the mold release agent in the molten metal is suctioned and discharged using a vacuum to prevent the formation of cavities and blowholes that are likely to occur in the casting. It is possible to prevent this and obtain good quality castings.

Secondly, unlike conventional low-pressure casting methods, there is no need to repeatedly supply and exhaust the air pressure inside the heat-retaining furnace, so there is less heat loss in the crucible, the heat-retaining capacity is small, and there is also less loss due to oxidation of the molten metal. It has a large energy saving effect.

As a different invention from the above, it is also possible to prevent oxidation of the molten metal by introducing an inert gas to replace the air in the space inside the heat retention furnace, and it is possible to form molds using good unmolten metal. In this case, it is sufficient to simply replace the inside of the heat-retaining furnace 9 with inert gas and air, and it is a feature of the present invention that the amount of inert gas used can be extremely small.

Furthermore, in order to suppress the release of hydrogen gas from the molten metal, it is also possible to bubble Freon gas or the like into the molten metal.

In the present invention, since the internal pressure of the heat retention furnace 9 is open to atmospheric pressure, it is possible to replenish the molten metal without stopping the 4 casting operations, and it is possible to replenish the molten metal even during the hook-shaped operation, thereby increasing the operation rate. .

As described above, the casting method of the present invention can be applied to conventional low-pressure casting equipment by simply adding a vacuum chamber and a vacuum pump, resulting in improved casting quality, increased operation rate, and energy saving effects. This is an extremely effective method.

[Brief explanation of the drawing]

The figure is a sectional view of a casting apparatus used to carry out the method of the invention. 100. Be, do, 2...tyroadpar-13...f
Latin, 4...Slide comb, 5...To, Dog rate, 6...Lower pressure cylinder, 7...Piston rod, C, 8...Su7)%9...Insulating furnace, 10 ···crucible,
11... Heat insulation material, 12... Heat retention heater, 13...
Lid, 14... Close poop, -bu, 15... Nozzle, 1
6...Lower mold, 17...Gate, 18...Upper plate, 19
...Vacuum plug, 20...Bottom surface, 21...Vacuum no e(
7', 22...Air supply pipe.

Claims (3)

[Claims] (1) In the metal lid casting method for light alloys, it is important to use a crucible! A vacuum casting method characterized in that Kunchi, -1 is suspended into the molten metal in a crucible, the down P&-1 and a metal lid sprue are airtightly connected, and the metal is evacuated. (2) In the gold layer casting method for light alloys, the upper part of the crucible is covered with a lid, and the poop is poured into the molten metal through the lid. lunch. - A vacuum casting method characterized by airtightly connecting #1 and a safe sprue, maintaining an inert gas in the internal space of the crucible at a pressure close to atmospheric pressure, and evacuating the metal lid. (3) The vacuum according to claim 2, characterized in that when filling the internal space of the crucible with an inert gas, the inert gas is pulsated into the molten metal and replaced with the air in the crucible. Casting method.