JP3755172B2 - Metal casting method and casting apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal casting method and a casting apparatus used therefor. More specifically, the present invention relates to an improvement in a metal casting method using a vacuum induction furnace and a casting apparatus used therefor.
[0002]
[Prior art]
Conventionally, in precision casting of metal, as shown in FIG. 6, a mold b having air permeability is held in a mold chamber a, and then the mold gate c is immersed in the molten metal e in the pan d. In this state, a method is adopted in which the inside of the mold chamber f is decompressed and the molten metal e is sucked and poured into the mold cavity f.
[0003]
However, in this method, due to the influence of atmospheric gas entrainment when the molten metal e is sucked and poured into the mold cavity f, many of the resulting castings have many pinhole defects, resulting in poor product yield. There is such a problem. In addition, when casting a cast product having a complicated shape, there is also a problem that the details of the mold cavity f cannot be sufficiently filled.
[0004]
Therefore, the appearance of a casting method and a casting apparatus suitable for the casting method that does not involve atmospheric gas and can ensure a sufficient filling rate of molten metal even in a mold having a complicated shape is eagerly desired.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems of the prior art, and provides a casting method that does not involve atmospheric gas and can ensure a sufficient filling rate even in a mold having a complicated shape, and a casting apparatus used therefor. It is an object.
[0006]
[Means for Solving the Problems]
As a result of diligent research on the problems of the prior art, the present inventors solved the above problem by incorporating the vacuum induction furnace apparatus, which the applicant of the present application separately applied for and obtained a patent, into the reduced pressure casting method. As a result, the present invention has been completed.
[0007]
That is, the metal casting methods of the present invention is a method of casting metal by vacuum injection method, a vacuum atmosphere in the first procedure and the vacuum atmosphere in the same pressure the mold for holding the molten metal under a predetermined vacuum atmosphere A second procedure for holding the mold below, a third procedure for immersing a mold spout of the mold held in the vacuum atmosphere at the same pressure in the molten metal held in the vacuum atmosphere, and the mold in the vacuum And a fourth step of pressing the surface of the molten metal with an inert gas while being placed in an atmosphere.
[0010]
Specifically, the metal casting apparatus according to the present invention includes an apparatus main body having a holding portion for holding molten metal, a first chamber disposed immediately above the apparatus main body, and an immediately above the first chamber. A second chamber provided; a third chamber in which a lower end disposed above and below the second chamber is open; and a mold disposed in the third chamber so as to be movable up and down. Is provided with a fourth chamber, exhaust means, and pressure-reducing means, and a first through hole communicating with the second chamber is provided at a position corresponding to the holding portion of the apparatus main body on the ceiling of the first chamber. An opening and closing means for opening and closing the first through hole is provided in the opening of the first through hole on the second chamber side, and is provided at a position corresponding to the first through hole of the second chamber ceiling. A second through hole is formed, and the third chamber is disposed at a position where the open end communicates with the second through hole when the third chamber is lowered onto the roof of the second chamber; The first chamber, the second chamber, the third chamber, and the fourth chamber can be depressurized to a predetermined vacuum state by the exhaust unit, and the first chamber can be recovered from the vacuum state to a predetermined pressure by the return pressure unit. It is characterized by being made.
[0011]
[Action]
In the present invention, since the time during which the molten metal is placed in a vacuum atmosphere is longer than that in the conventional reduced pressure injection method, degassing of the molten metal proceeds and the cleanliness of the molten metal is improved. In addition, since the residual gas in the mold cavity is extremely small, gas entrainment during molten metal injection is remarkably suppressed. As a result, pinhole defects in the cast product are significantly reduced.
[0012]
At the same time, since the residual gas in the mold cavity is extremely small, the residual gas pressure is extremely low, so that the resistance at the time of molten metal injection due to the residual gas pressure is small, and the filling rate of the molten metal is improved.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on an embodiment with reference to the accompanying drawings, but the present invention is not limited to the embodiment.
[0014]
A casting apparatus used in the metal casting method of the present invention is schematically shown in FIG. 1, and this casting apparatus A includes an induction furnace main body 10 and a melting chamber (a first chamber disposed immediately above the induction furnace main body 10). Chamber) 20, an intermediate chamber (second chamber) 30 disposed immediately above the dissolution chamber 20, and a vacuum chamber (third chamber) disposed above and below the central portion of the intermediate chamber 30 so as to be movable up and down. Chamber) 40 and a casting chamber (fourth chamber) 50 disposed in the vacuum chamber 40 so as to be movable up and down are main components.
[0015]
A melting furnace (induction furnace) 11 or a ladle 12 (hereinafter represented by the melting furnace 11) is provided at the center of the induction furnace body 10, and the molten metal filled in the mold cavity in the melting furnace 11 is provided. 13 (hereinafter simply referred to as hot water). The gas dissolved in the hot water 13 is degassed by a vacuum pump (not shown) connected to an exhaust port 21 provided in the melting chamber 20 via an exhaust pipe 22. That is, the hot water 13 is degassed by bringing the melting chamber 20 into a predetermined vacuum state. The melting chamber 20 is also provided with an argon gas supply port 23 for returning the pressure of the melting chamber 20 and pressing the hot water surface of the hot water 13 put in the melting furnace 11.
[0016]
A communication hole (first through hole) 24 communicating with the intermediate chamber 30 having a diameter through which the casting chamber 50 can be inserted is provided on the ceiling of the melting chamber 20 directly above the melting furnace 11. A gate valve 31 for opening and closing the communication hole 24 is mounted on the opening side of the intermediate chamber 30 of 24. An opening / closing mechanism 32 for opening / closing the gate valve 31 is installed in the intermediate chamber 30. The gate valve 31 is closed by the opening / closing mechanism 32 when the hot water 13 is degassed. Further, the peripheral edge of the opening of the intermediate chamber 30 is a water cooling flange 33, and an O-ring 34 is attached to a portion of the water cooling flange 33 that contacts the outer edge of the gate valve 31, and the melting chamber 20 is degassed. Airtightness is supposed to be secured.
[0017]
Specifically, the opening / closing mechanism 32 that opens and closes the gate valve 31 has a support arm 321 whose tip is joined to the outer periphery 31a of the gate valve 31 and a swivel whose tip is joined to the base end of the support arm 321. It comprises a rod 322 and lifting / lowering means 323 for turning and raising / lowering the turning rod 322. As shown in FIG. 1, the lifting / swinging means 323 is configured so that when the intermediate chamber 30 is evacuated, lubricating oil or the like is vaporized from the lifting / swinging means 323 and does not diffuse into the intermediate chamber 30. It is preferably installed on the rooftop 35 of the intermediate chamber 30. Therefore, the ceiling penetrating part of the intermediate chamber 30 of the swivel lock 322 is also appropriately sealed.
[0018]
The intermediate chamber 30 is also provided with an exhaust port 36 for making the inside a predetermined vacuum, and a hole having a diameter through which the casting chamber 50 can be inserted is located above the gate valve 31 of the ceiling portion. A (second through hole) 37 is provided. Here, the peripheral edge portion of the second through hole 37 is usually a flange 38.
[0019]
Above the second through-hole 37, a freely-coverable cylindrical vacuum chamber 40 having an inner diameter identical to the diameter of the second through-hole 37 is disposed. A skirt 41 is formed at the lower end 40 a of the vacuum chamber 40, and an O-ring 42 is interposed between the skirt 41 and the normal flange 38 of the second through hole 37. Thereby, when the vacuum chamber 40 is lowered, the vacuum chamber 40 and the intermediate chamber 30 are joined in an airtight manner. The vacuum chamber 40 is moved up and down, for example, by connecting the tip of the piston rod 431 of the hydraulic cylinder mechanism 43 provided at an appropriate position above the vacuum chamber 40 to an appropriate position of the lid 40b of the vacuum chamber 40, and then the piston rod. This is done by advancing and retracting 431.
[0020]
A casting chamber 50 is held in the vacuum chamber 40 so as to be movable up and down independently of the vacuum chamber 40. A casting mold 60 is held in the casting chamber 50. The posture of the mold 60 in the casting chamber 50 is made by the backup sand 51 accommodated in the chamber 50. Further, a suction part 52 including a suction head 521 and a suction cone 522 is formed at the head of the casting chamber 50. The suction part 52 is connected to a suction pipe 53 that passes through the lid 40 b of the vacuum chamber 40. The suction tube 53 is slidable through the lid 40b penetrating portion of the suction tube 53 while ensuring a desired airtightness. The casting chamber 50 is moved up and down, for example, at an appropriate position of the suction head 521 by penetrating the tip of the piston rod 541 of the hydraulic cylinder mechanism 54 provided at an appropriate position above the vacuum chamber 40 through the lid 40 b of the vacuum chamber 40. It is made by joining and then moving the piston rod 541 forward and backward. Desirable airtightness is also ensured in the lid 40b penetrating portion of the piston rod 541.
[0021]
Next, precision casting by a casting apparatus having such a configuration will be described with reference to FIGS.
[0022]
(1) The gate valve 31 is closed, and the melting chamber 20 is airtight.
[0023]
(2) The valve V ₁ is opened, the valves V ₂ , V ₃ , V ₄ are closed, the vacuum pump P ₁ is operated, and the inside of the melting chamber 20 is evacuated, for example, 10 torr or less.
[0024]
(3) The metal is melted in the melting furnace 11 and the molten state is maintained.
[0025]
(4) The mold 60 is set in the casting chamber 50.
[0026]
(5) The vacuum chamber 40 is lowered to the intermediate chamber 30 and set on the intermediate chamber 30.
[0027]
(6) The intermediate chamber 30 and the casting chamber 50 are evacuated by the vacuum pump P ₁ until the pressure is the same as that of the melting chamber 20.
[0028]
(7) The gate valve 31 is opened when the intermediate chamber 30 and the casting chamber 50 have the same pressure as the melting chamber 20.
[0029]
(8) The casting chamber 50 held in the vacuum chamber 40 is lowered, and the mold gate 60 a is immersed in the hot water 13.
[0030]
(9) After immersing the mold sprue 60a to the hot water 13, closing the valves V _1, V _2, the argon gas was sealed in the melting chamber 20 by opening the valve V _4, pressure was regained the melting chamber 20 to about 550Torr, Hot water 13 in the melting furnace 11 is poured into the mold cavity. At this time, the valve V ₃ is opened.
[0031]
Thus, according to this embodiment, since the hot water 13 put in the melting furnace 11 or the ladle 12 is kept under a vacuum of 10 torr or less longer than before, as a result, the degassing of the hot water 13 is performed. Advances, and the cleanliness of the hot water, that is, the molten metal 13 is improved.
[0032]
In addition, since the casting chamber 50 is held in the vacuum chamber 40 and the casting chamber 50 is in a high vacuum, the amount of gas remaining in the mold cavity is extremely small (about 1/150 compared to the conventional case). It is possible to significantly suppress gas entrainment when the molten metal 13 is injected.
[0033]
Further, since the residual gas pressure in the mold cavity is extremely small, the resistance when the molten metal 13 is injected due to the residual pressure is reduced, and the filling rate of the molten metal 13 is remarkably improved.
[0034]
【Example】
Hereinafter, the present invention will be described more specifically based on examples.
[0035]
Examples and Comparative Examples Cast products were produced by the casting method of the present invention, and the occurrence of pinhole defects in the cast products was investigated. The result is shown in FIG.
[0036]
For comparison, a cast product was produced by a conventional method, and the occurrence of pinhole defects in the cast product was investigated. The results are also shown in FIG.
[0037]
FIG. 5 shows that the product of the example has very few pinhole defects compared to the product of the comparative example.
[0038]
【The invention's effect】
As described above in detail, according to the present invention, the hot water put in the melting furnace or ladle is kept under a vacuum of 10 torr or less longer than before, and as a result, degassing of the hot water proceeds. In addition to improving the cleanliness of the molten metal, the casting chamber is held in a vacuum chamber, and the inside of the chamber is set to a high vacuum, so that there is very little gas remaining in the mold cavity (about 1/150), and the entrainment of gas at the time of pouring molten metal can be greatly suppressed, so the pinhole defects of castings can be remarkably reduced and the product quality can be improved. It is done.
[0039]
Further, since the gas remaining in the mold cavity is extremely small, the resistance at the time of molten metal injection due to the residual pressure is reduced, and an excellent effect that the filling rate of the molten metal is remarkably improved can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view of an embodiment of a casting apparatus used in the metal casting method of the present invention.
FIG. 2 is an explanatory view of a casting procedure by the casting apparatus, showing a state in which a gate valve is closed and a melting chamber is in an airtight state.
FIG. 3 is an explanatory view of a casting procedure by the casting apparatus, showing a state in which a melting chamber, an intermediate chamber, a vacuum chamber, and a casting chamber are in a predetermined vacuum.
FIG. 4 is an explanatory view of a casting procedure by the casting apparatus, showing a state in which a mold gate is immersed in hot water.
FIG. 5 is a graph of pinhole defect scores in examples and comparative examples.
FIG. 6 is an explanatory view of a conventional vacuum casting method.
[Explanation of symbols]
10 Induction furnace body 11 Melting furnace (induction furnace)
12 Ladle 13 Molten metal (hot water)
20 Dissolving chamber (first chamber)
21 Exhaust port 22 Exhaust pipe 23 Argon gas supply port 24 Communication hole (first through hole)
30 Intermediate room (2nd room)
31 Gate valve 32 Opening / closing mechanism 33 Water cooling flange 34 O-ring 35 Roof top 36 Exhaust port 37 Second through hole 38 Normal flange 40 Vacuum chamber (third chamber)
40b Lid 41 Skirt 42 O-ring 43 Hydraulic cylinder mechanism 50 Casting chamber (fourth chamber)
51 Backup Sand 52 Suction Part 53 Suction Pipe 54 Hydraulic Cylinder Mechanism 60 Mold 60a Mold Gate A Casting Equipment P ₁ Vacuum Pump V Valve

Claims (2)

A method of casting metal by vacuum injection method, a first procedure for holding the molten metal under a predetermined vacuum atmosphere, and a second procedure for holding the mold in a vacuum atmosphere of the vacuum atmosphere and the same pressure, the same A third step of immersing a mold spout of the mold held in a vacuum atmosphere at a pressure in the molten metal held in the vacuum atmosphere, and a surface of the molten metal while placing the mold in the vacuum atmosphere And a fourth step of pressing the substrate with an inert gas. An apparatus main body having a holding portion for holding molten metal, a first chamber disposed immediately above the apparatus main body, a second chamber disposed immediately above the first chamber, and an upper side of the second chamber A third chamber in which a lower end disposed in a freely movable manner is an open end, a fourth chamber in which a mold disposed in the third chamber in a freely movable manner is accommodated, an exhaust means, Pressure means,
A first through hole communicating with the second chamber is formed at a position corresponding to the holding portion of the device body on the ceiling of the first chamber,
The opening portion on the second chamber side of the first through hole is provided with an opening / closing means for opening and closing the first through hole,
A second through hole is formed at a position corresponding to the first through hole on the ceiling of the second chamber;
When the third chamber descends to the roof of the second chamber, the open end and the second through hole are disposed at a position where they communicate with each other,
The first chamber, the second chamber, the third chamber, and the fourth chamber can be depressurized to a predetermined vacuum state by the exhaust means,
The metal casting apparatus, wherein the return chamber allows the first chamber to recover from the vacuum state to a predetermined pressure.

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