JP5547035B2 - Low pressure casting furnace and low pressure casting method using the low pressure casting furnace - Google Patents

Description

  The present invention relates to a low-pressure casting furnace that pressurizes a molten metal surface to raise the molten metal through a filling stalk and fills it into a mold, and a low-pressure casting method using the low-pressure casting furnace.

  In general, it is equipped with a mold installed in the upper part of the pressurizing furnace and stalk (filling stalk) communicating with the mold from the pressurizing chamber, and filling is performed by pressurizing the molten metal surface such as aluminum. A low-pressure casting furnace is used that fills molten metal from the stalk to the mold.

  Further, in other low-pressure casting furnaces, Patent Document 1 discloses that the lower end of the pressurizing chamber and the lower end of the hot water outlet for pressurizing the molten metal in order to reduce the contact area between the molten metal and air to prevent oxidation of the molten metal. And a configuration in which these are connected by a communication pipe.

JP-A-11-138250

  In the low-pressure casting furnace described in Patent Document 1, the hot water outlet and the lower end of the pressurizing chamber are connected to each other by a communication pipe to prevent the molten metal from being oxidized. Since it is touched, the surface of the molten metal in the hot water outlet is in a state where an oxide film is easily generated. Therefore, when the mold is opened after pouring into the mold, the molten metal that has risen inside the hot water outlet falls into the furnace (inside the communication pipe) while entraining air, and oxide is entrained in the molten metal. May be.

  Since the oxide is heavier than the molten metal, it sinks to the bottom of the furnace. However, in the structure of Patent Document 1, since there is a connecting pipe immediately below the bottom of the outlet, the oxide that sinks to the bottom of the connecting pipe There is a possibility that it will be pushed out again into the hot water outlet and caught inside the cavity of the mold, causing casting defects such as strength reduction and crack initiation. Furthermore, the structure of Patent Document 1 has a problem that it is difficult to maintain because the oxide that is caught in the furnace and precipitated at the bottom of the connecting pipe cannot be removed.

  The present invention has been made in consideration of the above-described problems of the prior art, and includes a low-pressure casting furnace capable of preventing foreign matters such as oxides from being taken into the mold, and the low-pressure casting furnace. It aims at providing the low-pressure casting method used.

  The low-pressure casting furnace according to the present invention is a low-pressure casting furnace comprising a holding furnace for holding a molten metal and a pressure furnace that communicates with the holding furnace through an openable and closable molten metal flow port. A pressurizing chamber for storing molten metal; a filling stalk for filling the mold with the molten metal in the pressurizing chamber; and a pressurizing stalk for pressurizing the molten metal in the pressurizing chamber; The lower end and the lower end of the pressurizing stalk are installed so as to be positioned below the surface of the molten metal stored in the pressurizing chamber.

  According to such a configuration, in the low pressure casting furnace, the lower end of the filling stalk is located below the molten metal surface of the molten metal stored in the pressurizing chamber, so that the lower end is immersed in the molten metal. The molten metal near the center of the pressurizing chamber is preferentially introduced into the stalk, and the oxide that has fallen from the filling stalk into the pressurizing chamber after pouring into the mold remains precipitated at the bottom of the pressurizing chamber. Even if it remains or is wound up by pressurization, it remains in the vicinity of the hot water surface, and the oxide is suppressed as much as possible from being sucked into the filling stalk. Therefore, it is possible to prevent the oxide once falling into the pressurizing chamber from being pushed out again from the filling stalk into the mold and causing casting defects such as a decrease in strength and a crack starting point in the obtained cast product. Further, since the oxide is sunk in the pressurizing chamber, for example, the oxide can be easily removed and maintenance in the furnace can be performed simply by removing the lid of the pressurizing chamber. Further, the lower end of the pressurization stalk is also immersed in the molten metal, so that the molten metal can be sufficiently pressurized with the pressurization stalk and pushed more smoothly into the filling stalk.

  If the lower end of the pressurization stalk is disposed below the lower end of the filling stalk, the stroke of the pressurization stalk can be lengthened, so that it is possible to earn a capacity of the molten metal pushed out to the filling stalk. In addition, since the diameter of the stalk for pressurization can be reduced, the area where the molten metal is oxidized can be reduced.

  The distance from the bottom surface of the pressurizing chamber to the lower end of the filling stalk may be longer than the distance from the bottom surface to the lower end of the pressurizing stalk.

  A pressure reducing device that decompresses the pressure chamber is provided on the upper surface of the pressure furnace, and the top surface of the pressure chamber is inclined upward toward the pressure reducing device side. Since air can be efficiently and completely sucked out by the decompression device, the pressurized chamber can be easily filled with the molten metal.

  Moreover, it is preferable that the said pressure reduction apparatus is provided in the position spaced apart from the said filling stalk. If this happens, the collapsed sand core falls into the filling stalk during casting, and even if it is caught in the pressurizing chamber at the time of mold release, it floats upward in the pressurizing chamber and propagates most from the filling stalk along the inclination of the top surface. Since they gather in the away direction, this floating substance can be prevented from being introduced again into the filling stalk.

  Further, during the casting process in the low pressure casting furnace, the pressurizing chamber is filled with the molten metal up to a position where it comes into contact with the top surface. It is possible to more reliably prevent the molten metal in the vicinity of the center of the chamber from being introduced more reliably and the oxide that has settled at the bottom to be introduced into the filling stalk.

  The low-pressure casting method according to the present invention is a low-pressure casting method using a low-pressure casting furnace comprising a holding furnace for holding a molten metal, and a pressure furnace connected to the holding furnace by a molten metal circulation port that can be opened and closed. In a state where the molten metal is stored inside the pressurizing chamber of the pressurizing furnace, by introducing a pressurizing gas from a pressurization stalk whose lower end is positioned below the molten metal surface of the molten metal in the pressurizing chamber, The molten metal is pushed up into a filling stalk whose lower end is positioned below the surface of the molten metal in the pressurizing chamber, and the molten metal is filled into the mold from the filling stalk.

  According to such a method, in low pressure casting, the molten metal near the center of the pressurizing chamber is given priority to the filling stalk by immersing it in the molten metal with the lower end of the filling stalk below the surface of the molten metal. The oxide once introduced into the pressurizing chamber is once pushed out again from the filling stalk into the mold, and the resulting cast product is prevented from causing casting defects such as strength reduction and crack initiation. Can do. Further, by immersing the lower end of the pressurization stalk in the molten metal, the molten metal can be sufficiently pressurized with the pressurization stalk and pushed more smoothly into the filling stalk.

  Further, when the molten metal is filled in the mold in a state where the inside of the pressurizing chamber is filled up to the top surface with the molten metal, the oxide once dropped in the pressurizing chamber is again discharged from the filling stalk. Extrusion into the mold can be further suppressed.

  According to the present invention, in the low-pressure casting furnace, the lower end of the filling stalk is positioned below the surface of the molten metal stored in the pressurizing chamber, so that the lower end of the filling stalk is immersed in the molten metal. The molten metal near the center of the pressurization chamber is preferentially introduced, and the oxide once dropped into the pressurization chamber is pushed out again from the filling stalk into the mold, and the resulting cast product has reduced strength and cracks. It is possible to prevent casting defects such as a starting point. Further, since the oxide is sunk in the pressurizing chamber, for example, the oxide can be easily removed and maintenance in the furnace can be performed simply by removing the lid of the pressurizing chamber. Further, the lower end of the pressurization stalk is also immersed in the molten metal, so that the molten metal can be sufficiently pressurized with the pressurization stalk and pushed more smoothly into the filling stalk.

It is sectional drawing of the low pressure casting furnace which concerns on one Embodiment of this invention. FIG. 2A is a cross-sectional view showing a state in which the pressurization chamber is pressurized with pressurization stalk, and FIG. 2B is a cross-sectional view showing a state in which the pressurization with the pressurization stalk is stopped and the mold is opened. . FIG. 3A is a cross-sectional view showing a state in which the pressurization stalk is opened and pressure reduction control is performed in the pressurization chamber, and FIG. 3B is a cross-sectional view showing a state in which molten metal is replenished from the holding chamber to the pressurization chamber.

  Hereinafter, preferred embodiments of the low-pressure casting furnace according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a low-pressure casting furnace 10 according to an embodiment of the present invention. This low-pressure casting furnace 10 (hereinafter, also simply referred to as “casting furnace 10”) uses a pressurization stalk 16 to apply the molten stalk 18 stored in the pressurization chamber 14 inside the pressurization furnace 12 to the filling stalk 18. It is the apparatus which fills in the cavity 20a of the metal mold | die 20 through, and shape | molds a desired cast product. The molten metal M is, for example, aluminum or an alloy thereof, and the cast product (molded product) is, for example, a cylinder head of an internal combustion engine.

  As shown in FIG. 1, the casting furnace 10 includes a holding furnace 24 having a holding chamber 22 for holding a molten metal M, a pressurizing furnace 12 having a pressurizing chamber 14 in the holding furnace 24, and a pressurizing furnace 12. And a mold 20 installed on the upper surface of the pressure furnace 12. The holding chamber 22 and the pressurizing chamber 14 are communicated with each other through a molten metal circulation port 28 that can be opened and closed by an on-off valve 26.

  The holding furnace 24 includes a holding chamber 22 whose upper portion is closed by the holding chamber lid 30, a molten metal supply port 32 that obliquely penetrates the holding chamber lid 30, and whose lower end opens in the holding chamber 22, and the holding chamber lid 30. A pressurizing gas supply port 34 that penetrates and opens near the top surface of the holding chamber 22 is provided. The holding chamber 22 can hold the molten metal M within a desired temperature range by temperature control by the heater 36 installed slightly above the bottom.

  The molten metal supply port 32 is a conduit for injecting molten metal into the holding chamber 22. The pressurization gas supply port 34 opens the open / close valve 26 and holds a predetermined pressurization gas (for example, dehydrated air or inert gas) when the molten metal M flows from the holding chamber 22 to the pressurizing chamber 14. The hot water surface is pressurized and the molten metal M is pushed out from the molten metal distribution port 28 to the pressurizing chamber 14 side. The pressurization gas supply port 34 may be connected to an open / close valve, a compression pump, or the like (not shown).

  The pressurizing furnace 12 includes a pressurizing chamber 14 whose upper portion is closed by a pressurizing chamber lid 38, and a pressurizing stalk 16 and a filling stalk 18 that are arranged side by side through the pressurizing chamber lid 38. The pressurization stalk 16 and the filling stalk 18 have lower ends (lower openings) 16 a and 18 a that open in the pressurization chamber 14. That is, as can be understood from FIG. 1, the lower ends 16 a and 18 a of the pressurizing stalk 16 and the filling stalk 18 are positioned below the hot water surface when the molten metal M is stored in the pressurizing chamber 14. It is installed as follows. The pressurizing chamber 14 can hold the molten metal M within a desired temperature range by temperature control by the heater 40 installed slightly above the bottom.

  A die base 42 is fixed on the upper surface of the pressurizing chamber lid 38, and the mold 20 is fixed on the die base 42. That is, the filling stalk 18 passes through the pressurizing chamber lid 38 and the die base 42, and thereby connects the cavity 20 a and the pressurizing chamber 14 through the gate 20 b of the mold 20.

  The pressurization stalk 16 supplies and pressurizes a predetermined pressurization gas, for example, dehydrated air or inert gas, into the pressurization chamber 14, and raises the molten metal M in the chamber to the filling stalk 18 to the mold 20. The lower end 16a is opened at a position below the top surface 14b in the pressurizing chamber 14, and an open / close valve, a compression pump, etc. (not shown) are connected to the upper end.

  The filling stalk 18 is a cylindrical member for introducing the molten metal M in the pressurizing chamber 14 pressurized by the pressurizing stalk 16 into the cavity 20 a of the mold 20, and the lower end 18 a is the pressurizing chamber 14. It opens at a position below the top surface 14b.

  As can be seen from FIG. 1, in the casting furnace 10, the lower end 18a of the filling stalk 18 is disposed above the lower end 16a of the pressurizing stalk 16, that is, from the bottom surface 14a to the lower end 18a of the pressurizing chamber 14. The distance h1 is set longer than the distance h2 from the bottom surface 14a to the lower end 16a.

  In each wall surface constituting the pressurizing chamber 14, the bottom surface 14a is inclined downward from both sides toward the center and has a deepest structure in the center. The shape of the bottom surface 14a may be a structure in which two floor surfaces incline with a predetermined angle from both sides in FIG. 1 and cross each other. The structure etc. which the edge | side inclined in the shape of a mortar toward the center may be sufficient. On the other hand, the top surface 14b formed on the back surface of the pressurizing chamber lid 38 is an inclined surface inclined upward from the left side portion to the right side portion in FIG. 1, that is, the side on which the filling stalk 18 is installed. The inclined surface rises toward the side where the pressurizing stalk 16 is installed.

  A pressure reducing device 43 that passes through the pressure chamber lid 38 and opens to the top surface 14b and can be opened and closed by a pressure reducing valve 43a is provided on the side of the pressure stalk 16 that is upward in the inclination direction of the top surface 14b. ing. The decompression device 43 is a device capable of decompressing the inside of the pressurizing chamber 14, and is configured by, for example, a vacuum pump, a pipe for opening to the atmosphere, or the like.

  The molten metal flow port 28 that communicates between the holding furnace 24 and the pressurizing furnace 12 communicates from a substantially middle position side portion of the holding chamber 22 to a slightly widened bottom surface 14a of the pressurizing chamber 14 to a slightly upper side portion. The flow path can be opened and closed by the on-off valve 26. The on-off valve 26 can advance and retreat through the holding chamber lid 30 in an airtight state, and the molten metal flow can be achieved by landing and separating the lower end (tip) hemisphere on the valve seat 44 fixed to the molten metal flow port 28. The mouth 28 is opened and closed.

  Next, an example of a low pressure casting method using the low pressure casting furnace 10 configured as described above will be described.

  First, as shown in FIG. 1, for the pressurizing furnace 12, the mold 20 is clamped, the pressurizing stalk 16 is closed, and for the holding furnace 24, the pressurizing gas supply port 34 is closed. Further, the on-off valve 26 is also closed at the valve seat 44 and the molten metal flow port 28 is closed. In this state, the molten metal M is set as an initial amount during the casting process of the casting furnace 10. That is, the insides of the filling stalk 18 and the pressurizing stalk 16 are set to the liquid level La1 and Lb1, respectively, and the pressurizing chamber 14 is completely filled with the molten metal M up to the top surface 14b. 22 is set to the upper limit liquid level Lc1. As a result, the lower ends 16 a and 18 a of the pressurizing stalk 16 and the filling stalk 18 are positioned below the surface of the molten metal M stored in the pressurizing chamber 14.

  Subsequently, as shown in FIG. 2A, the stalk 16 for pressurization is opened, and the molten metal M is pressurized by introducing the pressurization gas into the pressurization chamber 14, thereby pushing up the hot water surface in the stalk 18 for filling, The molten metal M is filled into the cavity 20a of the mold 20 through the gate 20b. This filled state (pressurized state) is preferably maintained for a predetermined time until the molten metal M filled in the cavity 20a is solidified. After the melt M is completely solidified in the cavity 20a, the introduction of the pressurizing gas from the pressurizing stalk 16 is stopped and the mold 20 is opened as shown in FIG. 2B.

  After the mold 20 is opened, as shown in FIG. 3A, the pressurization stalk 16 is opened, and pressure reduction control is performed to lower the pressure chamber 14 to about atmospheric pressure. Thereby, in the pressurizing chamber 14, since the amount of the molten metal M is reduced by the amount used for casting in the cavity 20a, the molten metal level in the filling stalk 18 is lower than the initial level liquid level La1. The liquid level in the stalk 16 for pressurization rises to a liquid level Lb2 that is higher than the hot water level during pressurization (see FIGS. 2A and 2B) and lower than the initial liquid level Lb1.

  Next, as shown in FIG. 3B, the cast product (molded product) W after casting is taken out and conveyed to the next process. At the same time, in a state where the filling stalk 18 and the pressurization stalk 16 are opened and opened to the atmosphere, the on-off valve 26 is raised to open the molten metal flow port 28, and a predetermined pressurization from the pressurization gas supply port 34 of the holding furnace 24. A gas is introduced into the holding chamber 22. As a result, the surface of the molten metal M held in the holding chamber 22 is pressurized, and the molten metal M is supplied to the pressurized chamber 14 side through the molten metal flow port 28. Accordingly, in the pressurizing chamber 14, the molten metal M replenished from the holding chamber 22 restores the molten metal surfaces of the filling stalk 18 and the pressurizing stalk 16 to the liquid level La1, Lb1, and in the holding chamber 22, an initial amount of liquid is obtained. The liquid level Lc2 is lower than the surface level Lc1.

  After the casting process for one shot is completed in this way, the pressurization gas supply port 34 of the holding furnace 24 is closed again, the on-off valve 26 is lowered to close the molten metal flow port 28, and the mold 20 By performing the mold clamping, the initial state immediately before casting shown in FIG. 1 is obtained, and the same casting process can be subsequently repeated. At this time, when the amount of the molten metal M in the holding chamber 22 is less than an appropriate amount, the molten metal M may be replenished via the molten metal supply port 32.

  By the way, in the case of such a low-pressure casting furnace 10, after the molten metal M is poured into the mold 20 through the filling stalk 18, and then the mold is opened, the molten metal that has risen in the filling stalk 18. There is a possibility that M falls into the pressurizing chamber 14 while entraining air, and an oxide is entrained in the molten metal M in the pressurizing chamber 14.

  Therefore, in the casting furnace 10 according to the present embodiment, the pressurizing furnace 12 includes a pressurizing chamber 14 that stores the molten metal M, a filling stalk 18 that fills the mold 20 with the molten metal M in the pressurizing chamber 14, A pressurizing stalk 16 for pressurizing the molten metal M in the pressurizing chamber 14, and the lower end 18 a of the filling stalk 18 and the lower end 16 a of the pressurizing stalk 16 are hot surfaces of the melt M stored in the pressurizing chamber 14. It is installed so that it may be located below. It should be noted that the lower ends 16a and 18a are positioned below the surface of the molten metal M stored in the pressurizing chamber 14 when a normal amount of the casting furnace 10 is used (in this embodiment, the ceiling The pressure stalk 16 and the filling stalk 18 seem to be installed so that the lower ends 16a and 18a are immersed in the molten metal M in a state where the molten metal M of the amount filled up to the surface 14b is stored in the pressurized chamber 14. Refers to the structure.

  As described above, the lower end 18 a of the filling stalk 18 is positioned below the surface of the molten metal M stored in the pressurizing chamber 14, so that the filling stalk 18 has a portion near the center of the pressurizing chamber 14. Molten metal M is preferentially introduced, and the oxide remains precipitated at the bottom of the pressurizing chamber 14 or stays in the vicinity of the molten metal surface even when it is wound up by pressurization. Inhalation into the stalk 18 is suppressed as much as possible. Therefore, the oxide once dropped into the pressurizing chamber 14 is pushed out again into the filling stalk 18 and is caught in the cavity 20a, resulting in a casting defect such as a decrease in strength and a crack starting point. Can be prevented. Further, since the oxide is submerged in the pressurizing chamber 14, for example, the oxide can be easily removed and maintenance in the furnace can be performed simply by removing the pressurizing chamber lid 38. Moreover, the lower end 16a of the pressurizing stalk 16 is also immersed in the molten metal M, so that the molten metal M can be sufficiently pressurized by the pressurizing stalk 16 and pushed into the filling stalk 18 more smoothly.

  In the casting furnace 10, during the casting process, the inside of the pressurizing chamber 14 is filled with the molten metal M up to a position where it contacts the top surface 14b. As a result, the molten metal M near the center of the pressurizing chamber 14 is more smoothly introduced into the filling stalk 18 whose lower end 18a is opened in the pressurizing chamber 14, and the oxide that sinks to the bottom is filled with the stalk 18 for filling. It can prevent more reliably that it is introduced into the inside. In addition, when the pressurizing chamber 14 is filled with the molten metal M, oxidation of the molten metal M in the pressurizing chamber 14 can be prevented.

  In the casting furnace 10, the lower end 16 a of the pressurizing stalk 16 is opened below the lower end 18 a of the filling stalk 18 in the pressurizing chamber 14, and as shown in FIG. 1, the bottom surface 14 a of the pressurizing chamber 14. A distance h1 from the bottom surface 14a to the lower end 18a of the filling stalk 18 is set to be longer than a distance h2 from the bottom surface 14a to the lower end 16a of the pressing stalk 16. Therefore, since the pressurization stalk 16 can be made as long as possible, the capacity of the molten metal M pushed out to the filling stalk 18 can be gained, and further, the pressurization stalk 16 can be reduced in diameter. Since it is possible, the area which the molten metal M oxidizes can be reduced.

  The casting furnace 10 is provided with a decompression device 43 capable of decompressing the inside of the pressurization chamber 14 on the upper surface of the pressurization furnace 12, and the top surface 14b of the pressurization chamber 14 is inclined upward toward the decompression device 43 side. . Thereby, the air in the pressurizing chamber 14 can be efficiently and completely sucked out by the decompression device 43, and the pressurizing chamber 14 can be easily filled with the molten metal M.

  As shown in FIG. 1, the decompression device 43 is provided at a position separated from the filling stalk 18. In the low-pressure casting, a sand core (not shown) is usually used, but the sand core is lighter than the molten metal M and floats on the molten metal surface. At this time, in the casting furnace 10, even if the collapsed sand core falls into the filling stalk 18 and is caught in the pressurizing chamber 14 at the time of mold release, it floats upward in the pressurizing chamber 14, and Since it gathers in the direction farthest from the filling stalk 18 along the inclination, it is possible to prevent this floating substance from being introduced into the filling stalk 18 again.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10 ... Low pressure casting furnace 12 ... Pressurizing furnace 14 ... Pressurizing chamber 14a ... Bottom 14b ... Top surface 16 ... Pressurization stalk 16a, 18a ... Lower end 18 ... Filling stalk 20 ... Mold 22 ... Holding chamber 24 ... Holding furnace 28 ... Melt distribution port 43 ... Pressure reducing device

Claims (8)

A low pressure casting furnace comprising a holding furnace for holding a molten metal, and a pressure furnace communicating with the holding furnace through an openable and closable molten metal flow port,
The pressurizing furnace has a pressurizing chamber for storing the molten metal, a filling stalk for filling the mold with the molten metal in the pressurizing chamber, and a pressurizing stalk for pressurizing the molten metal in the pressurizing chamber. And
A low-pressure casting furnace, wherein a lower end of the filling stalk and a lower end of the pressurizing stalk are disposed so as to be positioned below a molten metal surface stored in the pressurizing chamber. The low pressure casting furnace according to claim 1,
A low-pressure casting furnace, wherein a lower end of the pressurizing stalk is disposed below a lower end of the filling stalk. In the low pressure casting furnace according to claim 1 or 2,
The low pressure casting furnace characterized in that a distance from the bottom surface of the pressurizing chamber to the lower end of the filling stalk is longer than a distance from the bottom surface to the lower end of the pressurizing stalk. In the low pressure casting furnace according to any one of claims 1 to 3,
A pressure reducing device for reducing the pressure in the pressure chamber is provided on the upper surface of the pressure furnace,
The top surface of the pressurizing chamber is inclined upward toward the decompression device side. The low pressure casting furnace according to claim 4,
The low-pressure casting furnace, wherein the decompression device is provided at a position separated from the filling stalk. In the low-pressure casting furnace according to any one of claims 1 to 5,
The low pressure casting furnace, wherein the pressurizing chamber is filled with the molten metal up to a position in contact with the top surface during a casting process in the low pressure casting furnace. A low pressure casting method using a low pressure casting furnace comprising a holding furnace for holding a molten metal and a pressure furnace connected to the holding furnace by a molten metal circulation port that can be opened and closed,
In a state where the molten metal is stored inside the pressurizing chamber of the pressurizing furnace, by introducing a pressurizing gas from a pressurization stalk whose lower end is positioned below the molten metal surface of the molten metal in the pressurizing chamber, A low pressure characterized in that the molten metal is pushed up into a filling stalk whose lower end is positioned below the surface of the molten metal in the pressurizing chamber, and the molten metal is filled into the mold from the filling stalk. Casting method. The low pressure casting method according to claim 7,
The low pressure casting method, wherein the molten metal is filled into the mold in a state where the inside of the pressurizing chamber is filled up to the top surface with the molten metal.

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