JPH07290225A - Reduced pressure casting method and device thereof - Google Patents

Abstract

PURPOSE:To reduce the development of gas deffect, such as blow hole, and to cast a sound casting by reducing the pressure in a cavity through a hollow part by a pressure reducing device after pouring a prescribed quantity of molten metal into a tundish, opening a nozzle and casting the molten metal in the tundish into the cavity. CONSTITUTION:A gas permeabile mold 1 is carried to a pouring station with a carrying device and a suction hole 17 from the pressure reducing device 12 is brought into close contact with the hollow part 11 in the gas permeable mold 1. Then, a stopper 13 is brought into close contact with a nozzle 14 and the molten metal is poured into the tundish 15 from the ladle 4. Successively, after killing the molten metal in the tundish 15, the stopper 13 is risen with a stopper rising/lowering means 16 and the nozzle 14 is an opened to execute the casting into the cavity. After solidifying the cast steel in the gas permeable mold 1, the mold is shaken out to obtain e.g. a cylindrical thin casting with a flange. As the result, the pouring speed of the molten metal is fast and the molten metal is difficult to disturb and the entrapment of the air and slag is little and the development of the casting defect is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduced pressure casting method and a reduced pressure casting apparatus for reducing the pressure of an air permeable mold having a sprue, a weir, a cavity, a feeder and / or a spit, and particularly, in a complicated shape. The present invention relates to a reduced pressure casting method and a reduced pressure casting apparatus for soundly producing a cast product such as thin-walled stainless cast steel or heat-resistant cast steel without improper casting, blowholes, or sinking defects.

[0002]

2. Description of the Related Art A thin casting having a wall thickness of 5 mm or less is easily solidified when molten metal is poured and comes into contact with a mold.
Further, even if it does not solidify, the viscosity becomes large and the fluidity deteriorates, and non-rotating defects are likely to occur. It is necessary to install a filter to remove the curd and impurities in the molten metal,
On the contrary, there is a problem that the bathing property deteriorates. Further, when casting a thin-walled casting having a complicated shape, air or a gas generated from a mold is particularly likely to be entrained in the molten metal, and gas defects such as blowholes are likely to occur in the casting after solidification.
Therefore, it has been difficult to soundly cast a thin-walled casting having a complicated shape and partially having a wall thickness of 5 mm or less with a material having poor fluidity of molten metal such as stainless cast steel and heat-resistant cast steel.

As one means for solving the above problems, Japanese Patent Laid-Open No. 61-88940 discloses that a feeder is provided on the side surface above the cavity, and a feeder on the upper surface and a reservoir for communicating with the cavity are provided. In addition, by inserting a stopper between the basin and the feeder, the molten metal can be injected at a high speed, the molten metal in the feeder is replenished in the cavity during solidification, and the molten metal is floated above the basin. There are disclosures that prevent defects. Further, in Japanese Patent Laid-Open No. 3-124363, a sand type nozzle that is in close contact with the molten metal drop nozzle of the weir is provided on the upper part of the mold separately from the weir. The pouring device provided with a stopper abutment seat portion that tightly engages with a stopper inserted through the molten metal drop nozzle of the weir ensures that the contact portion between the stopper and the sand-shaped stopper abutment seat portion is familiar. There is a disclosure in which the adhesion is improved without applying a high load to the stopper and the nozzle is used only once to eliminate the adhesion of molten metal impurities and improve the durability.

Further, Japanese Patent Laid-Open No. 4-147760 discloses a suction casting sand mold provided with a suction guide for forming a suction passage between a required portion of the mold space and the outside of the mold.
Depressurize locally the area where decompression is required to increase the suction effect,
There is also a disclosure that gas generated during pouring is naturally exhausted to the outside of the mold without being affected by suction to eliminate gas defects and cast a thin casting.

Further, Japanese Patent Application Laid-Open No. 57-177872 comprises a gas chamber for accommodating a mold, a container for accommodating a tundish for performing one casting operation upward, a gas chamber and a container opening / closing device. , There is a disclosure of a casting apparatus for casting a thin casting while protecting it from oxidation due to gravity and the differential pressure between the gas chamber and the container.

[0006]

However, the above-mentioned JP-A-61-88940 and JP-A-3-1243.
In the case of the No. 63 publication, pressure (back pressure) is generated in the cavity during casting, so the molten metal injection speed is insufficient, and improper rotation, wrinkles, and gas defects are likely to occur. Further, the molten metal settling time for lowering the molten metal temperature is insufficient, and a defect due to lapping easily occurs.

Japanese Unexamined Patent Publication (Kokai) No. 4-147760 requires a step of providing a suction guide in a sand mold, which results in poor productivity.
Since the air permeability of the suction passage is not so large as that of the sand mold, the suction effect is small, so it is difficult to cast a complicated and thin casting without imbalance.

Further, in Japanese Patent Laid-Open No. 57-177872, it is necessary to prepare a gas chamber for accommodating a mold and a container for accommodating a tundish for each casting, resulting in poor productivity.
Further, since the inside of the mold container is depressurized or pressurized, the suction effect up to the cavity is small.

Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art and to improve the fluidity of the molten metal even in thin cast stainless steel or heat-resistant cast steel having a complicated shape and partially having a thickness of 5 mm or less to prevent non-rotating defects. Etc., do not inject the melt and impurities in the molten metal into the cavity, reduce the entrainment of air or gas generated from the mold into the molten metal, and prevent gas defects such as blow holes in the cast metal after solidification. It is an object of the present invention to provide a vacuum casting method that can produce a sound casting with less generation. Further, another object of the present invention is to provide a vacuum casting apparatus capable of carrying out such a vacuum casting method.

[0010]

As a result of earnest research in view of the above object, the inventors of the present invention provided a feeder or skein at a position distant from the weir of the breathable mold. A tundish having a nozzle at the bottom and a nozzle at the bottom is formed integrally with the breathable mold by engaging the nozzle and the sprue, and the pressure reducing device depressurizes the inside of the cavity and the stopper. By opening and pouring the molten metal in the tundish into the cavity, even in castings such as complex and thin-walled stainless cast steel and heat-resistant cast steel, non-rotating defects can be prevented and the melt and impurities in the melt can be introduced into the cavity. The present invention was conceived based on the knowledge that a sound casting can be obtained without injecting the gas and without involving air or gas generated from the mold.

That is, the vacuum casting method of the present invention is a vacuum casting method in which a breathable mold having a sprue, a weir, a cavity, a riser and / or a skein is depressurized and cast. The feeder and / or spill is provided at a position distant from the weir, and a hole communicating with the outside is provided in the vicinity of the feeder and / or the spill, and a vacuum pump and a reduced pressure control are provided in the hole. The suction port of the decompression device having means is connected, and further, a tundish having a nozzle for sealing and opening at the bottom is formed integrally with the breathable mold by engaging the spout and the nozzle, After injecting a predetermined amount of the molten metal into the tundish, the decompression device decompresses the inside of the cavity through a hole portion and opens the nozzle to cast the molten metal in the tundish into the cavity. .

Then, a suction member having a higher air permeability than the air-permeable mold is provided between the hole portion, the cavity of the molten metal final filling portion, the feeder and / or the skein, to reduce the pressure of the hole portion. Casting is performed at a degree higher than the pressure reduction degree of the sprue.

Next, the reduced pressure casting apparatus of the present invention is a reduced pressure casting apparatus having an air permeable mold having a sprue, a weir, a cavity, a feeder and / or a skein, and a reduced pressure apparatus.
The breathable mold has a hole near the feeder and / or the skein that communicates with the outside, and the decompression device has a suction port that contacts the hole, and a seal and an opening are provided at the bottom. A tundish having a nozzle for performing the above-mentioned spout and the nozzle are formed integrally with the breathable mold, and the inside of the cavity is decompressed by the suction port brought into contact with the hole portion and the nozzle. Is opened and the molten metal in the tundish is cast into the cavity.

A suction member having an air permeability higher than that of the gas permeable mold is provided between the hole portion, the cavity of the molten metal final filling portion, the feeder and / or the skein, and the degree of pressure reduction of the hole portion is set. Is greater than the pressure reduction degree of the sprue. The suction member is a ceramic filter,
An air-permeable member that does not allow the molten metal to penetrate is used, such as a sand mold or a vent hole that uses sand with a grain size coarser than that of the air-permeable mold.

[0015]

[Function] When the pressure in the hole is reduced, the pressure of the feeder is raised or discharged, and the degree of pressure reduction of the cavity is reduced more than that of the gate, and the molten metal injected from the gate is sucked from the weir in the direction of the cavity, the feeder or the sink. Even if the cavity has a complicated shape and a thin wall portion, the cavity rotates. The molten metal poured into the tundish by a predetermined amount is allowed to settle, and the ladle and impurities are floated on the upper surface of the molten metal, and the molten metal is removed to clean the molten metal into the cavity. Since the cavity is decompressed from the holes near the feeder or the vase, the gas in the air rarely enters the cavity, and the gas generated from the mold during casting is sucked out when decompressing, so it is Little to get involved. When the pressure in the cavity is reduced by the pressure reducing device and the molten metal in the tundish is injected into the cavity by opening the nozzle and injecting the molten metal into the cavity, the breathable mold is closed and reduced in pressure, so there is little fluctuation in the reduced pressure value, and The decompression action works effectively. The suction member, which has a higher air permeability than the air-permeable mold, allows the pressure reduction from the holes to act on the riser, discharge, and cavity to prevent molten metal from entering the holes and control the degree of pressure reduction of the cavity. .
The riser or vase replenishes the molten metal with respect to the solidification contraction of the poured molten metal, collects the melt and the gas caught in the melt, and prevents the melt and the gas from entering the casting. Furthermore, by integrating the tundish with the breathable mold, the tundish can be molded simultaneously with the breathable mold. Further, the molten metal does not leak from the tundish nozzle and the sprue of the mold, and the degree of pressure reduction is small.

[0016]

The present invention will be described in detail below with reference to the drawings. (Embodiment 1) FIG. 1 is a vertical sectional view showing a vacuum casting apparatus according to an embodiment of the present invention. The vacuum casting equipment is a breathable mold 1,
It consists of a decompression device 12 and a tundish 15. The breathable mold 1 has a core 8 and an outer diameter of 45 mm and a thickness of 2.5.
mm with a length of 200 mm and an outer diameter of 8 at both ends
0 mm, 10 mm thick flange, and outer diameter 1
A thin cavity 2 having a cylindrical shape with a flange having two boss portions of 0 mm and a height of 15 mm is formed. The breathable mold 1 is a cold box type and uses silica sand No. 7. The sprue 5 is provided near one end of the breathable mold 1, and a filter 6 and a weir 7 are provided on the spout bottom continuous with the sprue 5. In the vicinity of the flange portion on the opposite side of the sprue 5, a riser 9 which is also used as a spout is installed. And, the skein and combined use hot water 9
A hole portion 11 opened toward the bottom surface of the breathable mold 1 is provided in the vicinity of A large suction member 10 (No. 5 sand layer) is provided.

The depressurizing device 12 has a vacuum pump, a depressurizing control means, and a suction port 17 which is brought into close contact with the hole portion 11 of the breathable mold 1 from a flexible pipe to perform depressurized suction. The tundish 15 is provided with a nozzle 14 at the bottom and a stopper 13 for opening and closing the nozzle 14 by a stopper elevating means 16, and the nozzle 14 is formed integrally with the spout of the breathable mold 1 in accordance with the nozzle.

Next, a vacuum casting method for producing a cast steel casting by the above apparatus will be described. The breathable mold 1 is carried into the pouring station (not shown) by a carrier device. Next, the suction port 17 from the decompression device 12 is brought into close contact with the hole 11 of the breathable mold 1. Then, the stopper 13 is brought into close contact with the nozzle 14, and 20 kg of molten metal required for one casting is poured into the tundish 15 from the ladle 4.
The temperature of the molten metal in the tundish 15 is 1500 ° C to 16 ° C.
The range is 00 ° C. Next, the reduced pressure value in the hole portion 11 is
Before pouring, the pressure is set to be in the range of -150 to -20 mmHg, and the degree of pressure reduction in the holes is larger than that in the sprue. After the molten metal has been calmed in the tundish 15 for 3 to 20 seconds, the stopper 13 is moved by the stopper elevating means 16.
Is raised to open the nozzle 14, and casting is performed in the cavity. Table 1 shows the chemical composition of the cast steel.

(Table 1) Chemical composition (% by weight) of cast cast steel C Si Mn P S Cr Fe 0.19 0.8 0.6 0.01 0.01 17.8 Remainder

After the cast steel casting is solidified in the breathable mold 1, it is carried out to the next demolding station (not shown) by the carrying device. Then, another breathable mold 1 before casting is carried into the pouring station. The above steps are repeated to cast the required number of thin cast steel castings. Fifty cylindrical thin cast steel castings with flanges were cast and the quality of the castings was investigated. As a result, the molten metal was injected at a high speed, the molten metal was not disturbed easily, the air and the ladle were not entangled, and there were no casting defects such as the total number, non-rotation, blowholes and ladle, and it was sound.

(Embodiment 2) FIG. 2 is a plan sectional view showing a vacuum casting apparatus according to another embodiment of the present invention. The breathable mold 1 has a hollow core 8 having a branched pipe having an outer diameter of 40 mm and a thickness of 2.3 mm, a flange portion having a thickness of 10 mm at both ends thereof, and a diameter of 10 mm and a height of 15 mm on the outer peripheral surface of the pipe. 5
A cavity 2 of a branched pipe having individual boss portions is formed. Breathable mold 1 is cold box type silica sand 6
Issue. The sprue 5 is provided near one end of the breathable mold 1, and the sprue 5 is provided with a filter 6 and a weir (not shown) at the bottom of the sprue. In the vicinity of the flange portion on the opposite side of the sprue 5, a riser 9 which is also used as a spout is installed. A hole portion 11 that opens toward the bottom surface of the air-permeable mold 1 is provided near the skein / combined riser 9 so that the air permeability is provided between the skein / combined riser 9 and the hollow core 8 and the cavity 11. A suction member 10 (No. 4 sand layer) having a higher air permeability than the mold 1 is provided. Hole 1
1, the suction port at the tip of the flexible tube is brought into close contact with the decompression device to perform decompression suction. The degree of pressure reduction in the hole portion 11 is set to be in the range of -180 to -30 mmHg before pouring, and the degree of pressure reduction in the hole portion is made larger than that of the sprue. The nozzle 14 of the tundish 15 is connected to the sprue 5 of the breathable mold 1.
25 kg of molten metal is injected into the tundish 15 by sealing the nozzle 14 with the stopper 13 and forming it integrally with the breathable mold 1 with a step showing the injection amount. After the pouring, the molten metal is calmed in the range of 3 to 20 seconds, and the stopper elevating means raises the stopper 13 to 150
The molten metal at 0 ° C. to 1600 ° C. is vacuum-cast in the cavity of the breathable mold 1. Table 2 shows the chemical composition of the cast steel.

(Table 2) Chemical composition of cast steel (% by weight) C Si Mn P S Cr Fe 0.11 1.0 0.6 0.01 0.01 18.3 Remainder

After the cast steel casting is solidified in the breathable mold 1, it is carried out to the next demolding station (not shown) by the carrying device. Then, another breathable mold 1 before casting is carried into the pouring station. The above steps are repeated to cast the required number of thin cast steel castings. 60 thin cast steel castings of branched pipes were cast and the quality of the castings was investigated. As a result, the molten metal was injected at a high speed, the molten metal was not disturbed easily, the air and the ladle were not entangled, and there were no casting defects such as the total number, non-rotation, blowholes and ladle, and it was sound.

[0024]

As described in detail above, a riser or skein is provided at a position distant from the weir of the breathable mold, a hole is provided in the vicinity of the riser or skein, and a nozzle is provided at the bottom. Since the tundish with is formed integrally with the breathable mold by engaging the nozzle and the sprue of the breathable mold, decompressing the inside of the cavity and opening the stopper to pour the molten metal in the tundish into the cavity. Produce the effect of. (1) A non-rotating defect is prevented by constantly increasing the pouring speed. (2) The melt-in and the impurities in the molten metal are not injected into the cavity to prevent the melt-in defect. (3) Blowholes are not generated without involving air or gas generated from the mold. (4) Since the tundish and breathable mold are integrated,
No molten metal leaks from the nozzle and sprue, and the degree of pressure reduction is minimal. Therefore, castings such as stainless cast steel or heat-resistant cast steel having a complicated shape and thin wall can be produced soundly.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a vacuum casting apparatus according to an embodiment of the present invention.

FIG. 2 is a plan sectional view showing a vacuum casting apparatus according to another embodiment of the present invention.

[Explanation of symbols]

1: breathable mold, 2: cavity, 3:
Molten metal, 4: ladle, 5: sprue,
6: filter, 7: weir, 8: core, 9: riser, 10: suction member,
11: hole part, 12: decompression device, 13: stopper, 14: nozzle, 15: tundish, 16: stopper lifting means, 17: suction port.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B22D 45/00 A 7511-4E

Claims (6)

[Claims] 1. A sprue, a weir, a cavity, a riser and / or
Alternatively, it is a reduced pressure casting method for reducing the pressure of an air-permeable mold having a skein and casting, wherein the feeder and / or the skein is provided at a position apart from the weir portion of the air-permeable mold, and the feeder and / or A hole communicating with the outside is provided in the vicinity of the skein, a vacuum pump and a suction port of a pressure reducing device having a pressure reducing degree control means are connected to the hole, and a nozzle for sealing and opening is further provided at the bottom. The tundish having is formed integrally with the breathable mold by engaging the gate and the nozzle, and after pouring a predetermined amount of the molten metal into the tundish, the decompression device decompresses the inside of the cavity through the holes. In addition, the nozzle is opened and the molten metal in the tundish is cast into the cavity. 2. The reduced pressure casting method according to claim 1,
A reduced pressure casting method, characterized in that a suction member having a higher air permeability than the air permeable mold is provided between the void portion, the cavity of the molten metal final filling portion, the feeder and / or the spout. 3. The reduced pressure casting method according to claim 1 or 2, wherein the degree of reduced pressure of the holes is larger than the degree of reduced pressure of the gate. 4. A sprue, weir, cavity, riser and / or
Alternatively, a reduced pressure casting apparatus having a breathable mold having a skein and a pressure reducing device, wherein the breathable mold has a hole portion communicating with the outside near the feeder and / or the skein, The device has a suction port in contact with the hole portion, a tundish having a nozzle for sealing and opening at the bottom, is formed integrally with the breathable mold by engaging the gate and the nozzle, A reduced pressure casting apparatus, characterized in that the inside of the cavity is decompressed by the suction port brought into contact with the hole portion, and the nozzle is opened to cast the molten metal in the tundish into the cavity. 5. The reduced pressure casting apparatus according to claim 4,
A vacuum casting apparatus, wherein a suction member having a higher air permeability than the air permeable mold is provided between the hole portion, the cavity of the molten metal final filling portion, the feeder and / or the spout. 6. The reduced pressure casting apparatus according to claim 4 or 5, wherein the reduced pressure degree of the holes is greater than the reduced pressure degree of the gate.