JPH03193258A - Method and device for manufacturing casting with cavity - Google Patents

Abstract

PURPOSE: To reduce the consumptions of a raw material, energy, etc., and to improve the productivity by supplying pressure gas having the same as or higher than the pressure acted to a molten material in a vessel in a cavity zone and pushing the molten material into the vessel. CONSTITUTION: The molten material from the vessel 6 is filled up into the cavity 3 in a casting mold 1 through a molten metal guide tube 11 under action of the high pressure in a sealing chamber 5 at the initial stage. The temp. condition in the casting mold is controlled with a microcomputer 13 to control the solidification of the molten material. A signal for opening a valve 7 is transmitted with the computer 13 and the pressed operating gas is come in the cavity 3 through a nozzle 2 after passing the valve 7. This pressure is higher than the pressure in the sealing chamber 5 and this gas pressure is preset through a reducing pressure valve 8. The molten material is pushed out from the cavity 3 under this high pressure operating gas. Thereafter, a signal is transmitted to the computer 13 from a sensor to transmit the command for closing the valve 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a casting having a cavity and an apparatus for manufacturing the same, and particularly to a casting with a special shape used in the foundry industry.

PRIOR ART A method for making hollow products from a silicate melt (1) is known, in which the silicate melt is poured into a prepared collapsible chill mold. The remainder of the melt is
It is poured by reversing a die with an opening at the bottom for a predetermined period of time. °Hollow varieties are made from chilled raw materials with a morphology that duplicates the forming surface of the die used. The wall thickness of the final product is a function of the retention time of the melt in the casting mold.

A disadvantage of this method is that energy has to be expended additionally to rotate the casting mold.

Another disadvantage of this method is the long processing time. Because it should rotate slowly with a smooth start and end with the presence of a large inertial force. On the other hand, the outflow of the melt is suppressed by the countermovement of the air.

Apparatus for casting thin-walled castings with cavities at low pressure are known, in which the melt from a melt container placed in a sealed chamber is cast under pressure higher than atmospheric pressure.
It is introduced through a conduit into a pressure chamber with two conical cavities. These cavities are connected between them and with the conduit. The first conical cavity is connected at its upper end to the casting mold.

The other cavity is connected to the cock by a conduit. This cock has at least four positions. A first position of the cock is connected to a source of pressurized gas. The second is connected to the gas volume of the sealed chamber. the third is connected to the conduit of the second conical cavity of the pressure vessel;
The fourth is connected to the atmosphere (2).

The conical cavities of both pressure chambers have approximately equal volumes and are connected by a passage opening. The cross section of the passage opening is equal to that of the raw material conduit. The volumes of the conical cavities connected to the cocks are such that when the casting mold fills them, the level of the melt in this cavity is close to a predetermined level.

The pressure vessel is within the top of the end of the conduit. This conduit is
It is connected to one of the conical cavities with a cock, which cock is provided in a device that stops the flow of gas in this cavity when the melt in the cavity reaches a predetermined level.

The disadvantage of this device is that it is only possible to cast under low pressure, especially when casting thin-walled hollow workpieces, and therefore it is necessary to additionally provide an intermediate pressure chamber with a cock to monitor the phase of the casting. .

Another disadvantage is that the evacuation of the melt from the cavity area within the casting is done by gravitational pouring with a reverse blow of air, which occupies the volume emitted by the melt. This method of evacuation of the melt is considerably longer in duration, resulting in an even longer casting cycle. And the accuracy in reaching the cavity dimensions is reduced. Moreover, the melt is further oxidized or gasified. Also,
The solidification of the melt requires a considerably longer time than the casting time, and the subsequent removal of the mold reduces the productivity of the device.

Also, counter-pressure casting
A method and apparatus for making castings from metals and alloys are known (3).The disadvantage of this method is that it is not suitable for casting shaped castings with cavities of complex shapes. This is because the melt cannot solidify on the surface placed at the top of the die cavity.

Another disadvantage of this method is that in order to extrude the melt from the die, the pressure must be increased in any sealed chamber in which the casting mold is located, and therefore the high pressure required to render it inert during this process consumption increases.

The disadvantage of this device is that it cannot record the passage of the melt over the free surface. Due to the increase in pressure, this melt leaves the die under the action of gas through the space from the level of the bottom to the conduit of the casting gate. There is therefore an unavoidable risk of this gas escaping through the melt in the crucible due to the pressure increase and of the melt spilling along the walls and covers of the furnace.

Another drawback of this device is that it is not possible to control the solidification process that creates the blank in the die.

[Technical problem to be solved by the invention, means for solving the problem] The object of the present invention is obtained by a method of making a casting having a cavity, in which the molten material is heated under pressure or provided with a container for the molten material. The raw material is passed through a conduit under the effect of a pressure difference between the sealed container and the sealed chamber containing the casting mold. It then fills the casting mold cavity and begins to solidify. The solidification process continues until a cast form is formed. The melt is then forced out of the vessel by supplying gas directly to the region within the cavity of the casting. This gas has a pressure equal to or greater than the pressure above the melt in the vessel.

The object of the invention is achieved with an apparatus for making castings with cavities and with a machine for vacuum casting.

It comprises a nozzle placed in the casting mold, which is connected to a container for compressed air through a first control valve and a pressure reducing valve, while the melt is passed through a second control valve in a sealed chamber. connected to the room. The feed line in the machine is fitted with a melt level sensor.

The advantage of this method is that it creates conditions for improving the cast structure by all structures. That is, the method is achieved by a controllable and directional solidification of the melt along with an optimal compensation of volume loss from the liquid phase filling up to the area of the casting cavity.

Another advantage is that when the use of single cores is avoided, reductions in raw materials, energy, and labor for manufacturing cores and removing them from castings can be realized. Furthermore, the work of the casting machine operator can be simplified. Furthermore, by reducing the number of core setting operations, productivity is improved. Since the destruction and collapse of the core of the foundry sand and the dangers caused by the released gas can be avoided, the conditions for producing rejected products can be eliminated.

The advantages of the method and device of the invention can be realized based on the existence of a machine for vacuum casting.

Another advantage of this device is that it regulates the temperature conditions of the die, in which the solidification of the casting is controlled, and the formation of cavities therein is monitored by a microcomputer.

[Example] FIG. 1 shows a specific example of an apparatus for realizing a method for manufacturing a casting having a cavity. This device is a diagram of a device with a machine for vacuum casting.

The apparatus shown in FIG. 1 includes a nozzle 2 in a casting mold 1,
This nozzle is connected in one end with the area of the cavity 3 in the casting, and in the other end with the sealed chamber 5 through a control valve 4 . In this sealed chamber 5 a container 6 of melt is placed. Further, the nozzle 2 is connected to a pressure gas container 9 through a first control valve 7 and a pressure reducing valve 8, and a manometer 10 is attached to this container. The raw material conduit 11 is provided with a sensor 12 for the melt level, which sensor
It is connected to a microcomputer-13. The microcomputer is connected to a control valve 14, to which a movable metal core 15 and a cooler 16 are connected through conduits for cooling liquid. A switch 17 is connected to the computer 13, which controls the electric heating element 18;3. . A thermocouple is inserted into the casting mold 1 corresponding to this element.

The pressure gas container 9 is connected to both the sealed chambers 5, 24 of the machine through valves 21, 22 and 23. on the other hand,
The sealed chambers 5.24 are connected to each other through valves 25. A discharge valve 26 is attached to the sealed chamber 24.

The method of operating the device is as follows. Valve 21.22
．． When 23 and 25 are opened and valve 7 is closed, both sealed chambers 5 and 24 are filled with pressurized gas from container 9. When both sealed chambers reach the same predetermined operating pressure, valve 22
．． 23. and close 25. If the valve 26 is now opened and the working gas is released from the sealed chamber 24 to the atmosphere, the pressure therein will decrease until it reaches a predetermined value. Then, the valve 26 is closed. Under the influence of the initial high pressure existing in the sealed chamber 5, the melt from the container 6 passes through the raw material conduit 11 and completely fills the cavity 3 of the casting mold 1.

According to a preset program and according to the information from the thermocouple 19 which records the temperature of the melt in the vessel 6 and furthermore the thermocouple 2 which records the temperature in the separation area of the casting mold.
Based on the information from the system 0, the microcomputer
13 turns on and off the supply of cooling liquid to the movable metal core 15 and to the cooler 16 through the valve 14. Meanwhile, the electric heating element 18 is turned on and off through the switch 17. Therefore, the microcomputer-13 is
Control the temperature conditions in the casting mold and also control the solidification of the melt. Thus, after a predetermined period of time, the melt takes the form of a casting. After that, microcomputer-13
sends a signal to open valve 7. Pressurized operating gas enters through the valve 7 via the nozzle 2 into the region of the casting cavity 3 . This gas pressure is higher than the pressure inside the sealed chamber 5, and the gas pressure is preset via the pressure reducing valve 8. Under this high pressure operating gas, the melt from the casting cavity 3 is forced out of it. When the free surface of the melt reaches the level sensor 12, the sensor sends a signal to the microcomputer 13, which issues a command to close the valve 7.

The flow of operating gas under pressure is therefore interrupted and a command is given to open the second control valve 4.

In this way, the pressure on the free surface of the melt in the raw material conduit is equal to the pressure in the sealed chamber 5. The melt thus continues to return to the container 6, but only by the effect of its own weight. Therefore, it is possible to prevent the melt from flowing out.

References 1.8G17065 2, FR2,147,827 3,8G, 48717

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention and is an explanatory diagram of an apparatus equipped with a vacuum casting machine.

Claims (1)

[Claims] 1. A method for manufacturing a casting having a cavity, which involves the action of pressure or the action of a pressure difference between a sealed chamber with a container for the melt and a sealed chamber with a casting mold. However,
A process in which the melt passes through a raw material conduit to fill the cavity of a casting mold and is allowed to solidify, using a gas at a pressure equal to or greater than the pressure exerted on the melt in the container after it has taken the form of the casting. A method as described above, characterized in that the melt is extruded into the container by feeding directly into the zone of the cavity of the casting. 2. An apparatus for manufacturing a casting having a cavity according to claim 1, which is attached to a vacuum casting machine, and includes a nozzle (2) in the casting mold (1), which nozzle is connected to the first control valve (7). ) and through a pressure-reducing valve (8) to a container for pressure gas (9), and this nozzle is connected through a second control valve (4) to a sealed chamber (5) with a container for the melt. and furthermore a level sensor (12) is attached to the raw material conduit (11) of this vacuum casting machine.