JPS62114762A - Suction and pressure casting method - Google Patents

Abstract

PURPOSE:To obtain a product having no internal defects such as blowholes and oxide generation without being affected by the pressure reduction speed of a reduced pressure chamber by first maintaining the inside of a pressurized chamber under a high vacuum then starting the pressure reduction of the reduced pressure chamber. CONSTITUTION:The inside of the pressurized chamber 2 in which a crucible 4 for a molten metal is disposed is reduced in pressure, then the pressure in the reduced pressure chamber 1 in which a casting mold 3 is disposed is reduced until the same degree of vacuum is maintained in the pressurized chamber 2 and the reduced pressure chamber 1. The pressure in the pressurized chamber 2 is then gradually opened to the atm. to decrease the degree of the pressure reduction and to provide a differential pressure to the pressurized chamber 2 and the reduced pressure chamber 1. The filling of the molten metal is then started. The inside of the pressurized chamber 2 is opened to the atm. to restore the atmospheric pressure and thereafter the pressure in the pressurized chamber 2 is increased to apply feeding force to the molten metal in the casting mold 3. The product having no defects such as oxide, blowholes and shrinkage cavities is thus obtd.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an improvement in a suction pressure casting method.

(Prior art and its problems) Investmen) Various methods have been adopted as I-casting casting methods, but in recent years, low-pressure casting method, which allows easy adjustment of casting speed, has been widely used in place of gravity casting method. However, recent casting products tend to be thinner and larger in order to reduce weight.
As a countermeasure against poor running of casting metal, methods such as providing gas vent holes in areas with poor running have been carried out through trial and error, but this method relies heavily on experience and has the disadvantage of being complicated. Therefore, the sprue of the mold is inserted into the molten metal, the pressure in the container surrounding the mold is reduced using a vacuum pump, and the molten metal is sucked into the mold.Once the mold is filled with molten metal, the inside of the container is returned to the atmosphere, and the runner It has been proposed to adopt the suction casting method, in which the unsolidified molten metal in the sprue is returned to the melting furnace, but in the darning method, the molten metal is sucked under a high vacuum, so the molten metal does not flow into the mold. The solidified layer that forms at the interface between the molten metal and the mold after pouring causes
There were inherent problems in that the pressure reduction effect was reduced, it was difficult to apply appropriate pressure to replenish the molten metal to each part of the product, and good internal quality could not be obtained. Therefore, in order to solve the above-mentioned problems in applying the suction casting method and to provide an improved method suitable for casting thin-walled and lightweight products, the depressurization effect employed in the conventional suction casting method can be applied without hindering the suction of molten metal. A suction pressure casting method that prevents quality deterioration due to molten metal entering the mold, while increasing the molten metal filling completion pressure to compensate for sufficient pressure to supply molten metal to each part of the product at an appropriate pressure. We have come to propose this.

However, such a suction pressure casting method has the problem that if the pressure reduction rate is faster than the gas discharge rate in the mold, gas will be left behind inside the product, causing so-called blowhole defects and oxides to be generated. However, the decompression speed must be controlled by a program controller.

(Problem of the Invention) An object of the present invention is to eliminate the problem of pressure reduction rate control that remains in such a vacuum vacuum casting method, and to provide a casting method that is less likely to cause internal defects such as oxides, blowholes, and cavities. .

(Summary of the Invention) The present invention is characterized in that a mold is placed in a decompression chamber so that the sprue is inserted into the molten metal located in the pressurization chamber, and the pressurization chamber is first held under high vacuum. After that, the depressurization of Nayanvar is started, and after the decompression chamber reaches the same degree of vacuum as the pressure chamber side, the pressure is adjusted so that a pressure difference is created between the two, and the molten metal is sucked up and filled with molten metal. The gist of this is the suction pressure casting method, which involves applying pressure to the molten metal by pressurizing the pressurizing chamber at an appropriate time.

In the present invention, the degree of vacuum in the pressurized chamber that is first reduced is 100-3, which is used in commonly used suction casting equipment.
00+llmHg or slightly higher 700 mn+
You can choose freely within the range up to HH.

Next, the pressure in the vacuum chamber is reduced to begin discharging the gas within the mold. When the degree of vacuum in the decompression chamber and the degree of vacuum in the pressurization chamber become the same, gas discharge from the mold is completed. From here on, the molten metal is sucked into the mold inside the vacuum chamber and cast using the differential pressure between the vacuum chamber and the pressurization chamber. , (2) The degree of depressurization may be reduced by gradually opening the pressurized chamber to the atmosphere. In addition, 3. When opening both the decompression chamber and the pressurized chamber to the atmosphere, the opening speed on the pressurized chamber side may be increased to provide a differential pressure.

Whichever method is adopted, it is preferable to control the filling rate programmatically because the filling rate becomes constant.

Once the molten metal has been filled into the mold, the molten metal is pressurized at an appropriate time to apply pushing force to prevent the formation of internal picket holes. It is sufficient that the pressure is sufficient to compensate for the molten metal pressure required for this, and it is usually used in the range of 0.1 to IK+ (/c+ meter), but higher pressures can also be applied.

As described above, the mold side is maintained at a reduced pressure equal to or greater than the molten metal filling completion pressure, while the molten metal side is maintained at a predetermined feeder pressure until solidification of the molten metal, and casting is completed.

Hereinafter, the present invention will be described in detail based on the accompanying drawings showing specific examples thereof.

(Example) FIG. 1 is a schematic diagram of equipment for carrying out the method according to the present invention, and FIG. 2 is a process diagram showing the sequence of depressurization and pressurization in the method of the present invention.

In Figure 1, (1) is a reduced pressure chamber, and (1) is a pressurized chamber (
2) A sprue 31, which is disposed above and has a suction casting mold (3) hanging from the bottom of the decompression chamber (1), is inserted into the crucible (4) in the pressurization chamber (2). It is arranged so that

The vacuum chamber (1) is provided with suction control means (5). That is, the regulating valve 51 is installed in the pressure reducing Nayanbar (1).
, a suction vibrator 53 is connected to a vacuum pump 56 via a receiver tank 52, and a pressure detector (55
), and a program controller 54 that controls the regulating valve 51 based on the pressure in the reduced pressure chamber (1) detected through the pressure reducing chamber (1).

A pressurizing pipe (7) from a pressurizing device (not shown) for low-pressure casting is connected to the pressurizing chamber (2), and a pressurizing control means (6) is installed, that is, a solenoid valve. The depressurizing vibro 3 is connected to a vacuum pump 62 via a pressure sensor 61, and a program feed roller 66 is provided to control a leak valve 65 based on the pressure inside the pressurized chamber detected via a pressure detector 64.

(Example 1) AC4CH alloy was made using a computer mold (approximately 10 kg).
℃, using the apparatus shown in FIG. 1, casting was performed in the order shown in FIGS. 2 (I) to (V).

That is, (I) the pressurized chamber in which the molten metal crucible is placed is depressurized.

(II) Next, the pressure in the reduced pressure chamber in which the mold is placed is reduced to equalize the degree of vacuum in the pressurized chamber and the reduced pressure chamber.

(III) The pressurized chamber is gradually opened to the atmosphere, the degree of pressure reduction is reduced, a pressure difference is applied between the pressurized chamber and the reduced pressure chamber, and filling of the molten metal is started. (IV) After opening the pressurizing chamber to the atmosphere and setting it at atmospheric pressure, the pressure in the pressurizing chamber is increased (~°) and a feeder force is applied to the molten metal in the mold.

As a result, there are no defects in the cast products, and the X ra
No internal defects such as oxides, blowholes, or cavities were found in the Y inspection.

(Examples 2 to 4 and Comparative Examples 1 to 3) Casting was performed in the same manner as in Example 1 except that 9J was used under the conditions shown in the table below. The results are shown in the right column of the table.

Ikekata, conventional low pressure casting method (comparative example 1), conventional suction casting method (
Comparative Example 2) and suction pressure casting method (Comparative Example 3) were used to compare the results with the method of the present invention.

The results are shown in the table.

[Margins below] (Operations and Effects of the Invention) As is clear from the above explanation, according to the present invention, the pressurized chamber is first held under high vacuum and then the depressurization of the decompression chamber is started. Not only can you obtain products without internal defects such as blowholes and oxide generation without being affected by the decompression speed of the decompression chamber, but you can also pressurize the molten metal after suction and filling the molten metal to apply the molten metal to each part of the product at an appropriate pressure. The problem of the conventional suction casting method is solved, and it is possible to obtain a product with good water circulation and no cavities.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of equipment for carrying out the method according to the present invention, and FIG. 2 is an explanatory diagram showing the casting process in the method of the present invention. (1)...decompression chamber, (2)...pressurization chamber,
(3)...Mold, (4) Crucible, (5)...
Suction control device, (6)... pressure reduction control device. Patent applicant: Kobe Steel, Ltd. Agent
Two patent attorneys (I) (If) (2) (IV)

Claims (1)

[Claims] (1) Place the mold in a decompression chamber so that the sprue hangs down and is inserted into the molten metal located in the pressurized chamber,
First, the pressurized chamber is held under high vacuum, then the depressurization of the depressurized chamber is started, and after the decompressed chamber reaches the same degree of vacuum as the pressurized chamber side, the pressure is adjusted so that a differential pressure is created between the two. A suction pressure casting method characterized by sucking up the molten metal and applying pressure to the molten metal by pressurizing a pressurizing chamber at an appropriate time after filling the molten metal.