JP2984753B2 - Casting method and device using vanishing model - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting method using a vanishing model gasified by a molten metal and an apparatus therefor.

[0002]

2. Description of the Related Art In general, a casting method using a fugitive model is, for example, disclosed in Japanese Patent Application Laid-Open No. 60-191637, in which a model formed of an expandable synthetic resin such as expanded polystyrene is used as a mold. It is a casting method in which the casting is formed by replacing the molten metal while gasifying the above model after pouring it into the casting and forming a casting without a burr according to this method. There is an advantage that it can be manufactured.

[0003] One of the factors that determine the quality of a casting is
First, there is a cooling rate during solidification. Generally higher intensity small grain size are known to increase the empirical rule or the like of the Hall-Petch, it is well known equation [delta] = Cv ⁿ for further relationship grain size and cooling rate. Where δ is D
AS2 (Dendrite Arm Space 2nd), v is the average cooling rate in the solidification section, and C is a constant. In the case of an aluminum alloy (JIS AC4C), C = 37 and n = -4. Assuming that the strength of the casting is σ, σ is a function of the above δ, and is expressed as σ = 480δ− ^0.17 . Therefore, in the above aluminum alloy, σ = 480 (37 v ^0.4 ) ^−0.17 = 260 v ^0.068

It is clear from the above equation that the strength increases when the cooling rate is high, and the strength increases about 1.2 times when the cooling rate increases ten times.

[0005]

As described above, a casting can improve mechanical properties such as strength by increasing the cooling rate during solidification.
It is extremely difficult to obtain higher quality than before. The reason is that, in the case of sand molds, the heat conduction is hindered by the holes existing between the molding sands and a heat retention effect occurs.Also, even if forced cooling is attempted by passing another refrigerant through the mold, the mold sand becomes a resistance and the refrigerant Is blocked, and the desired cooling cannot be achieved.

[0006] Therefore, an object of the present invention is to provide a casting method and a casting apparatus that improve the mechanical properties of a casting by increasing the cooling rate of the casting when using a vanishing model.

[0007]

According to the first aspect of the present invention, a vanishing model is buried in a mold, and a concave portion of the model is filled with molding sand having good collapsibility as a core. The casting is formed by replacing the model with molten metal to form a casting, and then discharging the casting sand as the core, and then introducing a cooling gas into a recess of the casting where the casting sand has been discharged. A casting method is provided.

According to the second invention of the present application, the vanishing model is embedded in a mold formed of molding sand having good collapsibility, and the molding sand having good collapsibility is also embedded in the concave portion of the model. Then, the casting is formed by replacing the model with molten metal to form a casting, then discharging the casting sand inside and outside the casting, and then adding the casting sand to the concave portion of the casting where the casting sand has been discharged. A casting method is provided wherein the outer wall surface of the casting is liquid-cooled while pressurizing the casting from the inner wall surface by introducing a pressurized gas.

Further, according to the third invention of the present application, a mold in which a fugitive model is buried, and good collapsible molding sand filled as a core into a concave portion of the model are poured from the inside of the casting after pouring. There is provided a casting apparatus provided with a discharging means and a means for introducing a cooling gas into a concave portion of the casting where the casting sand has been discharged.

Further, according to the fourth invention of the present application, a mold made of cast sand having good collapsibility in which a vanishing model is embedded, and a mold having good collapsibility filled as a core in a concave portion of the model. First casting sand discharging means for discharging sand from the interior of the casting after pouring, and second casting sand discharging means for discharging from the periphery of the casting the casting sand having good collapsibility forming the mold after the pouring. Means, means for sealing the recess of the casting where the foundry sand has been discharged, means for introducing a pressurized gas into the recess of the closed casting, and means for the casting where the foundry sand has been discharged. Means for introducing a cooling liquid to the surroundings.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a casting apparatus applied to a first embodiment of the present invention. A casting mold 1 is an air-permeable self-hardening sand mold containing a usual binder, and has a gate 1a and a runner 1b. The vanishing model 2 buried in the mold 1 is formed of a foamable resin such as expanded polystyrene, for example, and has a cup-shaped main body 2a having the same shape as the cast product as shown in FIG. A gate portion 2b connected to the lower end of the portion 2a and a runner portion 2c inserted halfway into the runner 1b of the mold 1 are integrally provided. A cylindrical insert fitting 3 is fixed to the upper end of the main body 2a of the model 2 coaxially with the main body 2a, and the cavity 4 inside the main body 2a contains no binder and has good collapsible molding sand. (Loose sand) 5 is filled as a core. A duct 7 having one end connected to the casting sand discharge chamber 6 is provided at the upper end of the insert fitting 3.
Is connected, and the cavity 4 inside the model body 2a and the chamber 6 communicate with each other through the inside of the insert fitting 3 and the duct 7. The chamber 6 is connected to a decompression pump 8 for forcibly discharging the casting sand 5 as a core filled in the cavity 4 in the model main body 2a into the chamber 6 after pouring. Further, an air nozzle 10 for introducing cooling air from a compressed air source 9 is provided inside the model main body 2a.
Is inserted.

Next, a casting method using the casting apparatus of FIG. 1 will be described with reference to FIG. First, for example, a molten metal (JIS AC2A aluminum alloy) having a temperature of 720 ° C. is injected from the gate 1a. By this pouring, each part of the fugitive model 2 in the mold 1 is gasified by the molten metal and replaced with the molten metal. Then, after the pouring is completed, when the solidification of the molten metal progresses a little and the molten metal has a self-standing shape retention property, the pressure reducing pump 8 is operated to quickly discharge the molding sand 5 in the casting product portion 11 into the chamber 6. . The discharge of the casting sand 5 releases the internal cavity 12 of the casting product part 11 to the atmosphere. However, since the cooling effect is small as it is, the compressed air is blown out from the air nozzle 10 to force the inner wall surface 11a of the casting product part 11. This state is maintained until the solidification of the cast product part 11 is completed, and the casting is completed.

As described above, in this embodiment, the casting product 1
By cooling only one side (the inner wall surface 11a in the present embodiment) strongly, a temperature gradient is generated inside the solidified metal (directional solidification) in addition to the usual quenching effect, so that nests or internal voids are formed. This has the effect of suppressing the generation of defects, thereby significantly improving the mechanical properties of the casting.

FIG. 4 shows a casting apparatus applied to a second embodiment of the present invention. A casting mold 21 is provided on a pedestal 23 which can be moved up and down by a cylinder 22. The mold 21 is composed of a permeable self-hardening sand mold 24 containing a binder, and the sand mold 24.
Filled in a cavity 25 formed vertically through,
It is formed of a good-disintegrating molding sand 26 containing no binder. A hole 23a having a shape substantially matching the cross-sectional shape of the cavity 25 is formed in a pedestal portion below the cavity 25 of the sand mold 24 filled with the casting sand 26, and a detachable bottom cover is formed in the hole 23a. 27 is fitted from below to receive the casting sand 26. The sand mold 24 is provided with only a gate 24a and a runner 24b.

The vanishing model 2 is the same as that used in the first embodiment and has an insert fitting 3 as shown in FIG. 2, but in this embodiment, the insert fitting 3 is not used. Fixed to the device. The model 2 is buried in the casting sand 26, and the tip of the runner portion 2 c of the model 2 is
4b. The cavity 4 inside the main body 2a of the model 2 is filled with molding sand 5 (the same material as the molding sand 26) having good collapsibility as in the first embodiment. A shutter 28 for opening and closing the upper end of the insert 3 is attached to the upper end of the insert 3 so that when the shutter 28 is closed, the opening at the upper end of the insert 3 is hermetically sealed. It has become.

Inside the model body 2a, a compressed air source 2 is provided.
An air nozzle 30 for introducing pressurized air from 9 is inserted. The air nozzle 30 serves to discharge the casting sand 5 in the casting 11 and pressurize the inside of the casting 11, and is mounted so that the tip of the air nozzle 30 is close to the bottom of the model body 2a. ing. The bottom cover 27 of the pedestal 23 is connected to the bottom cover attaching / detaching mechanism 31. When the bottom cover 27 is removed, the attaching / detaching mechanism 31 once moves the bottom cover 27 downward, and then turns to the position shown in FIG. It works. Although not shown, a duct 7 and a chamber 6 for discharging the casting sand 5 inside the casting product portion 11 are provided.
Are provided in the same manner as in the first embodiment.

Next, a casting method using the casting apparatus of FIG. 4 will be described with reference to FIGS. First, for example, a molten metal (J at a temperature of 720 ° C.)
IS AC2A aluminum alloy). By this pouring, the vanishing model 2 in the runner 24b and the casting sand 26 is gasified by the molten metal and replaced with the molten metal. Then, when the pouring is completed and the solidification of the molten metal progresses a little and the self-sustaining shape of the molten metal is maintained, the bottom cover 27 is opened as shown in FIG.
The casting sand 26 around the casting product 11 is dropped downward. At the same time, the casting sand 5 in the casting product part 11 is discharged through the same duct as in FIG. 3, and air blowing is performed from the air nozzle 30 to completely remove the casting sand 5 in the casting product part 11, and then the shutter 28 is opened. Operate the casting part 1
One internal cavity 12 is sealed. Next, the sand mold 24 is placed in the water tank 32.
As shown in FIG. 6, the entire sand mold 24 is submerged to rapidly cool the outer wall surface 11 b of the product part 11, and compressed air is supplied through the air nozzle 30 to the casting product part 11.
And the casting product part 11 is pressurized at a pressure of about 10 atm from the inner wall surface 11a side. In addition, the pressurization prevents water from entering the cavity 12. In the case of this embodiment, pouring takes 5 seconds,
Since the initial pressurization is started after 2 seconds and the predetermined pressure is reached after 7 seconds, the casting apparatus can be moved quickly to accomplish this process.

As described above, in this embodiment, since the casting product part 11 during solidification is immersed in water, the cooling rate is at most one.
Since the pressurization is performed by compressed air from the inside of the casting 11 at the same time as the directional solidification reaching 00 ° C./sec, the structure of the casting 11 is remarkably refined and defects are suppressed at the same time. Is obtained.

In this embodiment, the effect of solidification cracking is also exhibited by combining liquid cooling and pressurization. That is, when quenching reaches a maximum of 100 ° C./sec, many castings crack during solidification. However, the combination of quenching and pressurization as in the present embodiment allows the so-called pushing to be sufficiently performed. This prevents cracks from occurring.

[0021]

According to the present invention, a directional solidification of a casting can be effectively performed, and a casting having excellent mechanical properties can be obtained. Further, by combining the cooling with the liquid and the pressurization with the gas, the quality of the product can be further improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a casting apparatus applied to a first embodiment of the present invention.

FIG. 2 is a sectional view of a vanishing model used in the casting apparatus of FIG.

FIG. 3 is a sectional view for explaining the operation of the casting apparatus of FIG. 1;

FIG. 4 is a sectional view of a casting apparatus applied to a second embodiment of the present invention.

FIG. 5 is a sectional view for explaining the operation of the casting apparatus in FIG. 4;

FIG. 6 is a sectional view for explaining the operation of the casting apparatus of FIG. 4;

[Description of Signs] 1, 21 Mold 2 Elimination model 3 Insert fitting 5, 26 Casting sand with good collapsibility 6 Casting sand discharge chamber 7 Duct 8 Pressure reducing pump 10, 30 Air nozzle 11 Casting product part 22 Elevating cylinder 23 Pedestal 24 Sand mold 27 Bottom lid 28 Shutter 31 Bottom lid attaching / detaching mechanism 32 Water tank

Claims (4)

(57) [Claims] 1. A decayable model gasified by a molten metal is buried in a mold, and a concave portion of the model is filled with molding sand having good collapsibility as a core. Forming a casting by substituting the molten metal, and then discharging the casting sand as the core, and then introducing a cooling gas into the recess of the casting where the casting sand has been discharged, characterized by vanishing properties. Casting method using a model. 2. A decayable model gasified by a molten metal is buried in a mold made of molding sand having good collapsibility, and a recess of the model is filled with molding sand having good collapsibility as a core. Then, pouring is performed, and the casting is formed by replacing the model with a molten metal to form a casting.Next, after the casting sand inside and outside the casting is discharged, pressurized gas is injected into the recess of the casting where the casting sand has been discharged. A casting method using a vanishing model, wherein the casting is pressurized from its inner wall surface and the outer wall surface of the casting is liquid cooled. 3. A mold in which a dissipative model gasified by a molten metal is buried, and means for discharging from the inside of the casting after pouring good collapsible molding sand filled as a core into a concave portion of the model. Means for introducing a cooling gas into a concave portion of the casting where traces of the foundry sand have been discharged. 4. A mold made of molding sand having good collapsibility, in which a vanishing model gasified by a molten metal is embedded, and a molding sand having good collapsibility, which is filled as a core into a concave portion of the model. First casting sand discharging means for discharging from the interior of the casting after hot water;
Second casting sand discharging means for discharging the casting sand having good collapsibility forming the mold from the periphery of the casting after pouring, and means for sealing the recess of the casting where the casting sand has been discharged, A casting apparatus comprising: means for introducing a pressurized gas into a recess of a closed casting; and means for introducing a cooling liquid around a casting where traces of said casting sand have been discharged.