JP2016215257A - Pressure casting apparatus and casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure casting apparatus capable of maintaining cleanliness of a molten metal even when repeatedly performing a casting process, and a casting method.SOLUTION: Inert gas is supplied after solidification of a molten metal infilled into a cavity. Pressure is restored to return the molten metal within a stoke to a holding furnace. The inert gas is introduced into the stoke to prevent oxidation of the molten metal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure casting apparatus and a casting method, and more particularly, to a pressure casting apparatus and a casting method capable of maintaining the cleanliness of a molten metal.

  Conventionally, a suction differential pressure casting method is known as a casting method capable of producing a thin-walled product and suppressing the heating temperature and mold temperature of the molten metal (see, for example, Patent Document 1).

  In such a suction differential pressure casting method, after the molten metal is solidified to form a molded product, the mold cavity and the valve of the suction system leading to a sealed chamber (chamber) that holds the mold in an airtight state are closed, Open the atmosphere release valve to introduce air into the cavity or chamber, and release the pressurized state of the holding furnace to restore pressure. If it does so, air will enter into a mold from a crevice of a mold, a joint of a hot-water supply pipe, etc., will reach a hot water pool through a crevice between a mold and a molded article, etc., and a molten metal in stalk will return to a holding furnace.

JP-A-6-114533

In such a conventional suction differential pressure casting method, when the molten metal is lowered in the stalk, oxygen-containing air is sucked from the gaps in the mold or the connecting portion of the hot water supply pipe. Oxygen) comes into contact with oxygen and an oxide film is formed on the molten metal surface, and the cleanliness is lowered.
The generated oxide film causes casting defects, floats on the molten metal surface, enters the cavity at the next casting (at the time of the next shot), and lowers functions such as strength of the cast product.

Moreover, the inside of stalk will be filled with the air containing oxygen by the above-mentioned air suction when the molten metal descends. Therefore, at the next casting, the new surface of the molten metal that is generated as the molten metal rises and the oxygen-containing air in the stalk come into contact with each other to further oxidize the molten metal and increase the amount of oxide in the molten metal.
The increased oxide floats on the surface of the molten metal and enters the cavity, causing the strength of the cast product to decrease as described above.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a pressure casting apparatus and a casting method capable of maintaining the cleanliness of the molten metal even when the casting process is repeated. Is to provide.

  As a result of intensive studies to achieve the above-mentioned object, the present inventor can achieve the above-mentioned object by supplying an inert gas to the cavity and restoring the pressure when the metal melt filled in the cavity is restored after solidification. As a result, the present invention has been completed.

That is, the pressure casting apparatus of the present invention includes a mold,
A holding furnace for holding molten metal;
Stoke in which the cavity formed in the mold communicates with the inside of the holding furnace, and the lower end is immersed in the molten metal in the holding furnace,
A holding furnace pressure control device for controlling the pressure in the holding furnace and / or a suction device for controlling the pressure of the cavity formed in the mold,
Further, the present invention is characterized in that a metal melt cleanliness maintaining device for supplying an inert gas directly or indirectly to the cavity is provided, and the inert gas is supplied and decompressed before the mold is opened.

  Further, the casting method of the present invention includes a filling step in which the cavity in the mold is decompressed and / or pressurized in the holding furnace, and the molten metal is filled from the holding furnace into the cavity, and the molten metal filled in the cavity is solidified. A solidification step, and after the metal melt has solidified, a pressure reduction step of releasing the pressure of the cavity and / or holding furnace and returning the molten metal to the holding furnace. The pressure reduction step is inert to the cavity. It is characterized by supplying gas and restoring pressure.

  According to the present invention, since the inert gas is supplied to the cavity after the molten metal solidifies and the pressure is restored, air containing oxygen does not enter the stalk, and the molten metal cleanliness can prevent oxidation of the molten metal surface. A pressure casting apparatus provided with a maintenance device can be provided.

It is a figure which shows an example of the casting apparatus of this invention. It is a figure which shows another example of the casting apparatus of this invention. It is a figure which shows another example of the casting apparatus of this invention. It is a figure which shows another example of the casting apparatus of this invention. It is a figure which shows another example of the casting apparatus of this invention. (A) is an enlarged view of the connection part of the casting apparatus shown in FIG. 5, (b) is a principal part top view of a connection surface. It is a figure which shows the state which supplies an inert gas to the lower surface of a casting_mold | template at the time of casting_mold | template opening.

  The molten metal cleanliness maintaining apparatus of the present invention will be described in detail together with a casting apparatus in which the molten metal cleanliness maintaining apparatus is used.

<Pressure casting equipment>
The pressure casting apparatus of the present invention will be described with reference to FIG.
The pressure casting apparatus 100 of the present invention includes a holding furnace 2 that holds a molten metal 1, a mold 3 that is formed by a separable mold that forms a cavity 31 therein, and a molten metal cleanliness maintaining apparatus 8. The cavity 31 and the holding furnace 2 are communicated with each other by a stalk 4. The lower end of the stalk is immersed in the molten metal 1 in the holding furnace 2, and the molten metal is filled in the cavity 31 by the pressure difference between the pressure in the holding furnace 2 and the pressure in the cavity 31.

  The holding furnace 2 is formed airtight, and a holding furnace pressure control device 5 that adjusts the pressure in the holding furnace 2 is provided. The holding furnace pressure control device 5 pumps an inert gas such as carbon dioxide, pressurizing means 51 such as a pump for pressurizing the inside of the holding furnace 2, and a holding furnace pressure release control valve 52 for releasing the pressure in the holding furnace. The holding furnace pressurization control valve 53 is provided.

  The mold 3 may be provided with a core 32 as necessary, and may further be provided with a chamber 6 that covers the entire mold and is airtight.

The mold 3 is connected to a suction device 7 that sucks and decompresses the gas in the cavity 31.
The suction device 7 includes a decompression pump 71, a decompression tank 72, a suction control valve 73, an air introduction control valve 74 and the like, and is connected to the cavity 31 by a suction pipe 75.
As shown in FIG. 2, the suction device 7 preferably sucks the inside of the chamber 6 in addition to the mold 3. The inside of the chamber 6 is also sucked so that the pressure in the cavity 31 and the pressure in the chamber 6 covering the mold 3 are approximately the same, so that gas can be prevented from leaking into the cavity 31 from the gap of the mold 3. .

<Metal melt cleanliness maintenance device>
The molten metal cleanliness maintenance device 8 supplies the inert gas to the cavity 31 after filling the molten metal 1 and before opening the mold, and makes contact between the molten metal 1 and air containing an oxidizing gas such as oxygen. This prevents the molten metal 1 from being oxidized.
The molten metal cleanliness maintaining device 8 includes an inert gas tank 81 for storing an inert gas, a blower 82, an inert gas supply control valve 83, an inert gas supply pipe 84, and the like.

The inert gas is supplied to the cavity 31 after filling the molten metal 1 and before opening the mold. After the molten metal 1 is solidified, the suction control valve 73 is closed and the inert gas supply control valve 83 is opened to supply the inert gas. Then, the air introduction control valve 74 and the holding furnace pressure release control valve 52 are opened, the pressure of the cavity 31 and / or the holding furnace 2 is released and restored, and the molten metal 1 in the stalk 4 is returned to the holding furnace 2. Thus, the inside of the stalk 4 is filled with an inert gas.
That is, by supplying an inert gas to the cavity 31, the inert gas causes a gap between the molded product 3 and the mold 3 generated by volume shrinkage due to solidification of the molten metal 1, a gap between the molds, and the like. As described above, an inert gas is introduced into the stalk 4 as the molten metal surface in the stalk 4 decreases.
Accordingly, contact between the molten metal 1 and air or the like is prevented, and the cleanliness of the molten metal 1 is maintained.
The return pressure is an operation for returning the pressure in the cavity 31 from a reduced pressure state less than the atmospheric pressure at the time of filling the molten metal to substantially the atmospheric pressure, and / or the pressure in the holding furnace 2 is filled with the molten metal. It means an operation of returning to a substantially atmospheric pressure from a pressurized state exceeding the atmospheric pressure of the hour.

The inert gas is supplied to the cavity 31 directly or indirectly through the gap of the mold 3 by supplying the inert gas into the chamber 6 as shown in FIG. Can do.
The inert gas supply pipe 84 of the molten metal cleanliness maintenance device 8 is connected to the suction pipe 75 of the suction device 7 connected to the cavity 31 and / or the chamber 6 as shown in FIGS. Also good. Further, as shown in FIGS. 3 and 4, an inert gas supply pipe 84 may be directly connected to the cavity 31 and / or the chamber 6 as a separate system from the suction pipe 75.

Furthermore, as shown in FIG. 5, it is preferable to supply an inert gas around the connection portion 9 between the mold 3 and the stalk 4 for supplying molten metal to the mold.
By supplying an inert gas around the connecting portion 9, the inflow of the inert gas from the mold 3 side to the stalk 4 is not sufficient with respect to the speed at which the molten metal 1 descends in the stalk 4, and the stalk Even when the pressure in 4 decreases and gas flows into the stalk from the connecting portion 9, no air flows into the stalk 4.

  The inert gas is supplied to the connecting portion 9 by using an inert gas supply pipe 84 to supply the inert gas around the connecting portion 9 and to replace the air around the connecting portion with the inert gas. By doing so, an inert gas can be supplied. Specifically, an inert gas may be blown onto the seal member 91 that seals the connection portion 9 between the mold 3 and the stalk 4, but as shown in FIG. 6, a sealed space surrounding the seal member 91 is formed. It is preferable to provide and supply an inert gas to the sealed space 92.

  The supply pressure of the inert gas supplied to the sealed space 92 is preferably higher than the pressure in the stalk 4. By setting the pressure higher than the pressure in the stalk 4, gas does not leak from the stalk 4 into the sealed space 92 until the molten metal 1 rises to a height higher than the connecting portion 9.

The pressure of the inert gas supplied to the sealed space 92 is preferably equal to or lower than the molten metal pressure corresponding to the height of the cavity lower end surface 33 from the connection surface 93 between the mold 3 and the stalk 4.
By being below the molten metal pressure, after the molten metal 1 flows into the cavity 31, the pressure applied from the inside of the stalk 4 to the connecting portion 9 becomes higher than the pressure of the sealed space 92, and the stalk 4 from the connecting portion 9 is increased. It is possible to prevent the inert gas from leaking into the inside, and the occurrence of gas defects is prevented.
Here, in the present invention, the molten metal pressure refers to a pressure necessary to support a molten metal column having a predetermined height. The connection surface refers to the surface on which the sealing member 91 that seals between the stalk 4 and the mold 3 is installed, and the cavity lower end surface refers to the upper end surface of the gate through which the molten metal flows into the cavity.

Moreover, it is preferable to supply the inert gas to the circumference | surroundings of the said connection part 9 through the whole casting process. By supplying the inert gas through the entire casting process, the concentration of the oxidizing gas such as oxygen does not increase around the connection portion 9 and the invasion of the oxidizing gas into the stalk 4 can be prevented.
The whole casting process refers to all processes of a series of casting cycles from closing the mold 3 to casting a molded product, opening the mold 3 to take out the molded product, and closing the mold 3 again.

  Furthermore, it is preferable to supply an inert gas to the lower surface of the mold 3 that has been opened. Since the inert gas in the stalk expands due to the heat of the molten metal 1, it rises as the mold is opened and may be replaced with air. When the mold is opened and the molded product is taken out, the inert gas is supplied to the lower surface of the mold 3 so that even if the inert gas existing in the stalk 4 rises before the mold is opened, the molten metal 1 is heated. Since no new inert gas enters the stalk 4, contact between the molten metal 1 and the air is prevented.

  As shown in FIG. 7, the inert gas is supplied to the lower surface of the mold 3 by inserting an inert gas supply pipe 84 into the mold, and the blower 82 connected to an inert gas tank (not shown). An inert gas may be supplied to the lower surface of the substrate, or may be supplied by connecting an inert gas supply pipe 84 near the lower surface in the mold.

The inert gas can be used as long as it does not oxidize the molten metal 1, and examples thereof include noble gas, nitrogen gas, carbon dioxide, etc., but carbon dioxide having an average molecular weight larger than that of air. Etc.
By using an inert gas having a molecular weight larger than the average molecular weight of air, when the mold 3 is opened and the molded product is taken out, it is difficult for the inert gas that has entered the stalk 4 to be replaced with air. Cleanliness is maintained.

<Suction casting method>
Next, the casting method of the present invention will be described.
The casting method of the present invention includes a filling step, a solidification step, and a decompression step.
First, if necessary, the core 32 is placed in the mold 3 to close the mold 3, and the process proceeds to a filling process to fill the cavity 31 with the molten metal 1.

  The filling step is a step of filling the molten metal 1 from the holding furnace 2 to the cavity 31 through the stalk 4 by reducing the pressure of the cavity 31 in the mold 3 and / or pressurizing the holding furnace 2.

The depressurization of the cavity 31 and the pressurization in the holding furnace 2 may be performed independently or in parallel, but the inside of the holding furnace 2 is pressurized to raise the molten metal 1 to the gate. After that, it is preferable to start the pressure reduction of the cavity 31 and fill the molten metal 1 into the cavity 31 by combining the pressure in the holding furnace 2 and the pressure reduction in the cavity 31.
By performing the pressurization in the holding furnace 2 and the decompression of the cavity 31 together, the hot water supply property is improved and the occurrence of casting defects is prevented.

  When the metal melt 1 is filled in the cavity 31, the holding furnace pressurization control valve 53 and / or the suction control valve 73 is closed and the solidification process is started, and the metal melt 1 is maintained while maintaining the pressure of the cavity 31 and / or the holding furnace 2. To solidify.

When the molten metal 1 is solidified, the inert gas supply control valve 83 is opened to supply the inert gas to the cavity 31, the pressure of the cavity 31 and / or the holding furnace 2 is released, and the molten metal 1 in the stalk 4 is removed. Return to holding furnace 2.
Specifically, the suction system is closed by the suction control valve 73 provided in the suction pipe 75 connected to the cavity 31 and / or the chamber 6, and the inert gas supply control valve 83 of the inert gas supply pipe 84 is disabled. The active gas supply system is opened to supply the inert gas to the cavity 31 and / or the chamber 6.

  Thereafter, the holding furnace pressure release control valve 52 and / or the air introduction control valve 74 is opened, and the pressure of the cavity 31 and / or the holding furnace 2 is released to restore the pressure. By releasing the pressure after supplying the inert gas, it is possible to prevent the air other than the inert gas from leaking into the stalk 4.

  Thereafter, the mold 3 is opened, the molded product is taken out, and the next casting process (next shot) is started.

DESCRIPTION OF SYMBOLS 1 Molten metal 2 Holding furnace 3 Mold 31 Cavity 32 Core 33 Lower end surface 4 Stoke 5 Holding furnace pressure control device 51 Pressurizing means 52 Holding furnace pressure release control valve 53 Holding furnace pressurization control valve 6 Chamber 7 Suction device 71 Decompression pump 72 Depressurization tank 73 Suction control valve 74 Air introduction control valve 75 Suction pipe 8 Molten metal cleanliness maintenance device 81 Inert gas tank 82 Blower 83 Inert gas supply control valve 84 Inert gas supply pipe 9 Connection portion 91 Seal member 92 Sealed space 93 Connection surface 100 Pressure casting apparatus

Claims (6)

A pressure casting apparatus that fills and molds a molten metal into a cavity formed in a mold,
A mold,
A holding furnace for holding molten metal;
Stoke in which the cavity formed in the mold communicates with the inside of the holding furnace, and the lower end is immersed in the molten metal in the holding furnace,
A holding furnace pressure control device for controlling the pressure in the holding furnace and / or a suction device for controlling the pressure of the cavity formed in the mold,
Further, a pressure casting apparatus comprising a molten metal cleanliness maintaining device for supplying an inert gas directly or indirectly to the cavity after filling the molten metal and before opening the mold.   2. The pressure casting apparatus according to claim 1, wherein the molten metal cleanliness maintaining device supplies an inert gas into a chamber covering the mold.   3. The molten metal cleanliness maintaining device further supplies an inert gas around a connection portion between the mold and a stalk that supplies the molten metal to the mold. The pressure casting apparatus described.   The molten metal cleanliness maintaining device includes a sealed space around a connection portion between the mold and stalk that supplies the molten metal to the mold, and the supply pressure of the inert gas supplied to the sealed space is within the stalk. 4. The pressure casting apparatus according to claim 3, wherein the pressure casting apparatus is higher than the pressure and not more than a molten metal pressure corresponding to a height of a cavity lower end surface from a connection surface between the mold and the stalk.   The pressure casting apparatus according to claim 4, wherein the molten metal cleanliness maintaining apparatus supplies the inert gas to the sealed space through the entire casting process. A filling step of decompressing the cavity in the mold and / or pressurizing the inside of the holding furnace to fill the cavity with the molten metal from the holding furnace;
A solidification step of solidifying the molten metal filled in the cavity;
After the metal melt has solidified, it has a pressure-reducing step of releasing the pressure of the cavity and / or holding furnace and returning the molten metal to the holding furnace,
A pressure casting method, wherein the pressure-recovery step supplies an inert gas to the cavity to recover the pressure.

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