JPS5884661A - Method and device for pressure casting - Google Patents

Abstract

PURPOSE:To obtain castings having good casting surfaces and having no blowholes in performing pressure casting by using dies of which the wall surfaces delineating casting cavities are constituted of casting sand, by pouring molten metal after the internal pressure in the casting sand parts attains an equal pressure in a hermetic chamber. CONSTITUTION:A box member 6 and a movable die 11 are retreated leftward together with a movable supporting body 3 by means of a cylinder device 4 to open a hermetic chamber 9. While dies are held open, a sand core 12 is mounted to a stationary die 10 and molten metal for one pouring is poured into a molten metal ladle 15. Thereafter, the member 6 and the die 11 are advanced rightward together with the body 3 by the device 4 and a hermetic sealing member 8 is pressed to a plate member 5 to close the chamber 9. A valve 21 for supplying compressed gas is opened to supply compressed air into the chamber 9 to increase the pressure therein above the atmospheric pressure and when the internal pressure of the core 12 attains an equal pressure in the chamber 9, a shaft 16 is rotated by the cylinder 4 to tilt the ladle 15 to supply the molten metal through a sprue 14 into cavity 13.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure casting method and a casting apparatus used for carrying out the casting method, and in particular to a pressure casting method using a mold in which at least a part of the wall surface constituting a casting cavity is made of anti-sand. Pertains to casting methods and equipment for pressure casting.

In casting methods that use a mold in which at least a portion of the wall defining the casting cavity is made of sandproof material, such as a mold casting method using a sand core or a sand mold casting method, the casting cavity is Compared to the casting method, which uses a mold in which all of the defined walls are made of metal, the solidification time of the metal is longer, more gas is generated, and it is difficult to avoid gas defects such as pinholes. It is difficult to cast reliable, high-quality pressure-resistant products.

In view of the above-mentioned problems with casting methods using sand cores or sand molds, the mold is placed in an airtight chamber, and the pressure in the airtight chamber is raised to above atmospheric pressure to pressurize the melt in the casting cavity together with the mold. , a pressure casting method has been proposed in which the molten metal is solidified in a pressurized atmosphere, and this casting method shortens the solidification time of the metal and eliminates the occurrence of gas defects even if a sand core or sand mold is used. It has the advantage that sand cores and sand molds with low strength will not be damaged even if they are used.

However, conventionally, this pressure casting method increases the air pressure in the airtight chamber after pouring is completed to create a pressurized atmosphere. As a result, a pressure difference occurs between the molten metal in the casting cavity, the sand core, and the inside of the sand mold, causing molten metal to be inserted or ooze out from the solidified surface, resulting in castings with good quality casting surfaces. difficult to obtain. For this reason, conventionally, rough casting surfaces have been prevented by using sand cores, sand molds, or painted molds with low air permeability, but even when these molds are used, it is not possible to obtain castings with very good casting surfaces. Moreover, the effect of uniformly pressurizing the entire molten metal within the casting cavity is reduced, and there is a risk that the original effects of the pressure casting method may not be fully exhibited.

In view of the above-mentioned problems in the conventional pressure casting method, the present invention proposes an improved pressure casting method that can cast high-quality castings with good casting surfaces without impairing the original effects of the pressure casting method. The object of the present invention is to provide a casting method and a casting apparatus used for carrying out the casting method.

According to the present invention, in a casting method in which pressure casting is performed using a mold in which at least a part of the wall surface defining a casting cavity is made of anti-sand, the mold is housed in an airtight chamber, A casting method characterized in that the pressure in the airtight chamber is raised to above atmospheric pressure, and then molten metal is poured into the casting cavity, and an apparatus for carrying out the casting method that accommodates a mold. It is characterized by having an airtight container that can be opened and closed, a compressed gas supply means for supplying compressed gas into the airtight container, and a pouring means for pouring molten metal into a mold housed in the airtight container. This is accomplished using a pressure casting device.

According to the present invention, melting is performed after the pressure inside the casting sand section becomes equal to the pressure in the airtight chamber, so a pressure difference is generated between the molten metal injected into the casting cavity and the casting sand section. This avoids the occurrence of molten metal insertion, molten metal seepage from the solidified surface, etc., and it is possible to obtain a high quality cast product with a good casting surface and no gas defects.

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

The attached figure is a longitudinal sectional view showing one embodiment of the pressure casting apparatus according to the present invention. In the figure, 1 indicates a pedestal, on which a fixed support 2 and a movable support 3 are provided facing each other. The fixed support 2 is fixed to the pedestal 1, and the movable support 3 is attached to the guide rail 1 provided on the pedestal 1.
It is provided so as to be movable in the left and right directions as shown in the figure, guided by a.

A plate member 5 is attached to the fixed support 2, and a box member 6 which is open on the side of the fixed support 2 is attached to the movable support 3, and a metal bellows 7 and a metal bellows 7 are attached to the opening edge of the box member 6. An airtight seal member 8 is attached. The box member 6 abuts and engages the plate member 5 with its airtight seal member 8, thereby cooperating with the plate member 5 to form an airtight chamber 9 inside thereof.

The movable support 3 is reciprocated by a cylinder device 4 between a forward position as shown in the figure and a backward position moved leftward in the figure from the forward position.

5- A fixed mold 1o is fixed to the air chamber 9 side of the plate member 5, and a movable mold 11 is fixed to the airtight chamber 9 side of the box member 6. The fixed mold 10 and the movable mold 11 are clamped when the airtight seal member 8 engages with the plate member 5 and the box member 6 forms the airtight chamber 9 together with the plate portion 15, as shown in the figure. A casting cavity 13 is defined together with the sand core 12, and a sprue 14 is formed in the upper part of the casting cavity 13.

A molten metal ladle 15 is provided in the upper part of the airtight chamber 9.

This molten metal ladle 15 is rotatably supported by the plate member 5 by a shaft 16, and the shaft 16 is connected to a cylinder device 18 by an arm 17, and is rotationally driven by the cylinder device. Further, the plate member 5 is provided with a compressed gas inlet/outlet 19, and this inlet/outlet 19 is connected to the conduit 20.
．． A compressed gas supply valve 21 is connected to a compressed gas supply device 23 such as a compressor via a conduit 22, and a conduit 20 and a conduit 2
7 and is connected to an exhaust valve 28. The conduit 20 is also provided with a pressure gauge 29 . The compressed gas used in this casting method may be air in the case of casting ferrous metals6, but in the case of casting active metals such as aluminum, it may be an inert gas to obtain the effect of reducing inclusions. preferable.

The movable mold 10 is also provided with an extrusion bottle 24, which is connected to an extrusion plate 25, and the extrusion plate 25 is connected to a cylinder device 26 and driven by the cylinder device. ing.

Next, a description will be given of how the casting method according to the present invention is carried out using the pressure casting apparatus configured as described above.

First, the box member 6 and the movable mold 11 are moved back to the left in the figure along with the movable support 3 by the cylinder device 4, and the airtight chamber 9 is closed.
Open the mold 1o and fix the sand core 12 in the opened state.
Attach it to the molten metal and remove it again! At 1415, pour the molten eel necessary for one casting. After the preparation work as described above is completed, the box member 6 is moved together with the movable support 3 by the cylinder device 4.
Then, the movable mold 11 is moved forward to the right in the figure, and the airtight seal member 8 is pressed against the plate member 5 to close the airtight chamber 9. This 7
At one time, the movable mold 11 engages with the fixed mold 10, and so-called mold clamping is completed. Next, the compressed gas supply valve 21 is opened to supply compressed gas into the airtight chamber 9 from the compressed gas supply valve [23, and the pressure in the airtight chamber 9 is raised to a predetermined value above atmospheric pressure, for example, about 5 to 10 atm. let After a period of time necessary for the pressure inside the sand core 12 to become equal to the pressure inside the airtight chamber 9, the shaft 16 is rotated by the cylinder device 18 while maintaining this pressure state, and the molten metal ladle 15 is tilted. Then, the molten metal previously poured into the ladle 15 is poured into the casting cavity 13 from the sprue 14. As a result, molten metal is supplied to the casting cavity 13.

The pressurized atmosphere in the airtight chamber 9 is maintained until the molten metal is completely solidified, and the molten metal is allowed to solidify under the pressurized atmosphere. The time required for the pressure inside the sand core 12 to become equal to the pressure inside the airtight chamber 9 depends on the thickness of the sand core, etc., but in many cases, the pressure indication on the pressure gauge 29 is the required pressure. It takes about 10 seconds after the instruction is given.

After the molten metal in the casting cavity 13 has completely solidified 8-, the compressed gas supply valve 21 is closed and the exhaust valve 29 is opened to evacuate the airtight chamber 9 to reduce the pressure inside the airtight chamber to atmospheric pressure. The box member 6 and the movable mold 11 are moved back to the left in the figure along with the movable support 3 by the device 4,
The airtight chamber 9 is opened and the mold is opened. Also, the cylinder device 26 advances the pusher bottle 24 to the left in the figure.
The completed casting is removed from the casting cavity.

As described above, according to the present invention, since the pouring is performed after the pressure inside the sand core 12 becomes equal to the pressure inside the airtight chamber 9, the molten metal poured into the casting cavity and the sand core 12 are poured.
There is no differential pressure between the molten metal and the solidified surface, and there are no casting surface defects due to molten metal insertion or molten metal seeping from the solidified surface, resulting in high quality casting with a good casting surface and no gas defects. It will be understood that you can obtain a product.

In the above-mentioned embodiment, the molten metal is poured by tilting the molten metal tapping steel provided separately from the mold, but this pouring is carried out by tilting the molten metal in a part of the mold. This may be done by providing a pool equivalent to a ladle and tilting the entire mold in an airtight chamber, or by tilting the mold together with a container that constitutes an airtight chamber. Gas entrainment in the process is reduced.

Further, the casting method according to the present invention is not limited to casting using a mold composed of a metal mold and a sand core, but can of course be applied to #a construction using a sand mold.

[Brief explanation of drawings]

The attached figure is a longitudinal sectional view showing one embodiment of the pressure casting apparatus according to the present invention. 1... Pedestal, 2... Fixed support, 3... Movable support. 4... Cylinder device, 5... Plate part, 6... Box member, 7... Metal bellows, 8... Airtight seal member,
9... Airtight chamber, 10... Fixed mold, 11... Movable mold, 12... Sand core, 13... Casting cavity,
14... Sprue, 15... Molten metal ladle, 16... Shaft,
17... Arm, 18... Cylinder device, 19...
- Compressed gas inlet/outlet, 20... conduit. 21... Compressed gas supply valve, 22... Conduit, 23...
・Compressed gas supply device, 24... Extrusion bottle, 25...
- Extrusion 10- plate, 26... cylinder device, 27... conduit,
28...Exhaust valve, 29...Pressure gauge Patent applicant: Toyota Motor Corporation representative
Patent Attorney Takeshi Akishi 11-

Claims (2)

[Claims] (1) In a casting method in which pressure casting is performed using a mold in which at least a portion of the wall surface defining the casting cavity is made of sand-proof material, the mold is placed in an airtight chamber, and the air pressure in the airtight chamber is increased. A casting method characterized by raising the pressure above atmospheric pressure and then pouring the metal into the casting cavity. (2) It has an airtight container that can be opened and closed to accommodate a mold, a compressed gas supply means for supplying compressed gas into the airtight container, and a pouring means for pouring molten metal into the mold housed in the airtight container. Pressure casting equipment characterized by: