JPH0622742B2 - Heat retention device for low-pressure casting machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is designed to supply molten metal in a crucible to a cavity of a mold through stalk by applying pressure of pressurized air to the molten metal surface. In a low-pressure casting machine, the present invention relates to improvement of a hot water pool heat retention device for heating and holding a molten metal in a crucible at a predetermined temperature.

(Prior Art) Generally, as such a water pool heat retaining device, a heating coil is embedded in a side wall of a heat retaining furnace that houses the crucible, and the crucible is heated from the outer periphery by the heat generating action of the heating coil. A well-known type is an indirect heating type that keeps the temperature of the molten metal stored in the crucible.

However, since this one indirectly heats the molten metal in the crucible as described above, it has a drawback that it consumes a large amount of power and is uneconomical.

Therefore, in order to efficiently exert the heat energy required for keeping the temperature of the molten metal of the heating coil, for example, the actual open sho 59
As disclosed in Japanese Patent Laid-Open No. 102251, a protective tube made of a refractory material (for example, ceramic) having a built-in heating coil is projected into the crucible, and the molten metal in the crucible is directly heated to reduce power consumption. A direct heating type has been proposed in which the amount is greatly reduced.

Incidentally, an example of comparing the power consumptions of the above indirect heating type and the direct heating type under the same condition is shown. The indirect heating type has a power consumption of 22 KW / Hr, while the direct heating type has a power consumption of 7 KW / Hr. It becomes Hr, and it is possible to significantly reduce the power consumption.

(Problems to be Solved by the Invention) Incidentally, when casting a cylinder head used for an automobile engine, for example, with an aluminum alloy, it is generally practiced to add sodium metal to the molten metal to make the aluminum structure fine. It is being appreciated. When casting a cylinder head made of such an aluminum alloy by a low pressure casting machine having the above direct heating type heat retaining device,
Since the pressure of pressurized air is applied to the surface of the molten metal to push the molten metal into the mold, the action of this pressure causes the metallic sodium in the molten metal to permeate the protective tube and form the metallic sodium and protective tube. However, there is a problem that cracks are likely to occur in the protective tube due to a difference in thermal expansion coefficient from that of silicon nitride, for example. Further, due to that, the heating coil in the protective tube may be broken.

The present invention has been made in view of the above points, and an object of the present invention is to provide a direct heating type in which a protective tube is projected in the crucible as described above. By increasing the pressure inside the protective tube against the pressure, it is possible to suppress the penetration of metallic sodium in the molten metal into the protective tube, prevent cracks in the protective tube, and prolong the life of the heating means inside the protective tube. It is to plan.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the solution means of the present invention is to stoke the molten metal in the crucible kept at a predetermined temperature by applying pressure of pressurized air to the molten metal surface. A protection tube made of a refractory material protruding into the crucible and having a built-in heating means is provided to the low-pressure casting machine which is designed to be supplied to the cavity of the mold via the. Further, a pressurized fluid supply means for supplying a pressurized fluid is provided in the protective pipe.

(Operation) With the above configuration, in the present invention, when pressurized air is supplied into the crucible, the molten metal in the crucible is heated to a predetermined temperature by the heating means in the protective tube made of a refractory material protruding into the crucible. A pressure acts on the surface of the molten metal by the pressurized air, and the molten metal is supplied to the cavity of the mold through the stoke by the action of this pressure.

At this time, since the heating fluid is supplied to the inside of the protective tube made of the refractory material by the pressurized fluid supply means, the pressure inside the protective tube is increased by the pressurized fluid, and the pressure of the pressurized air on the molten metal surface is increased. Even if pressure is applied, penetration of metallic sodium added to the molten metal into the protective tube is suppressed, and cracks in the protective tube due to the difference in thermal expansion coefficient between metallic sodium and silicon nitride for a long period of time. Is prevented and the life of the protection tube is extended. Further, by preventing the generation of the cracks, the heating means in the protective tube is prevented from being damaged.

(Example) Hereinafter, the Example of this invention is described based on drawing.

The drawings show a low-pressure casting machine equipped with a hot water pool heat insulating device according to an embodiment of the present invention, wherein 1 is an adiabatic heat insulating furnace installed on a floor surface 2 through a support frame member 3, and 4 is a heat insulating furnace inside the heat insulating furnace 1. The crucible 4 is fitted and stored, and a molten metal A made of an aluminum alloy is stored in the crucible 4. The heat insulating furnace 1 has a case 5 as an outer wall thereof, a first heat insulating material layer 6 which is housed in the case 5 so as to cover the inner wall surface thereof, and is made of a heat insulating material such as ceramic fiber, and the first heat insulating material. Timber layer 6
Is provided inside and is formed in a triple structure with the second heat insulating material layer 7 made of a heat insulating material such as castable refractory, and is configured to suppress the heat dissipation of the molten metal A stored in the crucible 4. ing. Reference numeral 8 denotes a two-layer heat insulating material layer that covers the upper surface openings of the heat retaining furnace 1 and the crucible 4 (the heat retaining furnace 1
The upper wall member made of the same material as the heat insulating material layers 6 and 7), 9 is a top plate provided on the upper surface thereof, and the upper wall member 8 and the top plate 9 have substantially central portions opened.

Further, 10 is a furnace lid placed on the top plate 9,
A through hole 11 penetrating in the vertical direction is formed in the center of the furnace lid 10 corresponding to the openings of the upper wall member 8 and the top plate 9, and the lower portion of the through hole 11 is located inside the crucible 4. A vertically facing cylindrical stalk 12 is supported by engaging the engaging flange portion 12a at the upper end thereof with the engaging recessed portion 11a of the peripheral edge of the through hole 11. A mold 19 is detachably installed on the upper surface of the furnace lid 10, and a cavity 20 in the mold 19 is communicated with the crucible 4 through the stalk 12. Then, holes 13 and 14 reaching the inner surface of the through hole 11 from the outer surface are respectively provided in the furnace lid 10 in the radial direction so as to substantially face each other, and one (the right side in the drawing) of the hole 13 is a valve. While being connected to a pressurized air supply device (not shown) through a supply pipe 15 having a hole 18, the hole portion 14 on the other side (the left side in the drawing) is connected to an exhaust pipe 16 having a valve 17, The valve 18 on the supply pipe 15 side is opened with the valve 17 on the 16 side closed, and the pressurized air supply device is operated to operate the crucible 4 via the supply pipe 15.
By supplying pressurized air into the crucible 4, the pressure of the pressurized air is applied to the surface of the molten metal A in the crucible 4, and the molten metal A is applied to the mold 1.
It is adapted to supply and fill the inside of the cavity 20 of 9.

Further, 21 penetrates the side wall of the heat insulation furnace 1 and the crucible 4
A protection tube 21 made of a refractory material such as ceramic that horizontally projects from the outside of the crucible 4 is provided.
The tapered portion projecting inward is closed to form a bottomed tubular shape, and the opening opening outside the heat insulating furnace 1 is sealed by the case 5 side wall of the heat insulating furnace 1 and the fixing plate 25 so as to surround the opening. It communicates with the formed closed chamber 26. A plurality of insulators 2 are provided on the side of the protective tube 21 corresponding to the inside of the crucible 4.
, 23 are attached, and a heating coil 24 made of nichrome wire or the like as a heating means is stretched around each insulator 23. The heating coil 24 is connected to the outside of the protective tube 21 via a core material 22 for power supply. Connected to the connection terminal 33 of. Also,
A heat resistant and breathable material 27 made of glass wool or the like is filled in the base side of the protective tube 21. Similarly, the heat resistant and air permeable material 27 is also filled in the closed chamber 26 formed by the fixed plate 25 and the side wall of the heat insulating furnace 1 (case 5).

Further, a communication passage 28 that communicates the inside of the crucible 4 and the inside of the closed chamber 26 is formed in a portion from the upper wall member 8 to the first heat insulating material layer 6 of the heat insulating furnace 1. By the closed chamber 26 and the pressurized air supply device, pressurized air as a pressurized fluid is supplied into the protection tube 21 to supply the crucible 4
A pressurized fluid supply means 31 is configured so that a pressure equivalent to that applied to the molten metal surface inside the molten metal A also acts on the inside of the protective pipe 21.

In addition, 29 and 30 are holding members made of a refractory material for stably holding the protection tube 21, and 32 is a discharging mechanism for discharging the molten metal A in the crucible 4.

Therefore, in the above embodiment, the crucible 4 and the heat insulation furnace 1 are
When pressurized air is supplied from the pressurized air supply device into the crucible 4 in a state where the mold is sealed and the mold 19 is set,
The pressurized air increases the pressure in the crucible 4 and presses the molten metal surface of the molten metal A in the crucible 4, and the molten metal A is stalk 1
It is pushed up through the cavity 20 into the cavity 20 of the mold 19 and filled therein, whereby the casting product is low-pressure cast.

At this time, the protection pipe 21 in the crucible 4 is connected to the communication passage 2
Since the compressed air supplied into the crucible 4 through the supply pipe 15 pressurizes the molten metal surface of the molten metal A stored in the crucible 4, the communication passage 2
It is also supplied to the inside of the protective pipe 21 via 8 to pressurize the inner wall of the protective pipe 21 with the same pressure as the molten metal surface. From this fact, the pressure difference acting on the inner wall and the outer wall of the protection tube 21 becomes almost zero, which is the case where metallic sodium is added to the molten metal A in order to refine the aluminum structure of the casting. However, the protective tube 21 for sodium metal
Penetration into the protective tube 21 is suppressed, and it is possible to prevent the clad from occurring in the protective tube 21 for a long period of time, and thus the life of the protective tube 21 can be extended. In addition, the protection tube 21
Since cracks do not occur in the heating coil, it is possible to effectively prevent disconnection of the heating coil 24 due to this.

In the above embodiment, the internal pressure of the protection tube 21 is increased by communicating the inside of the crucible 4 and the inside of the protection tube 21 with the communication passage 28. However, the present invention is not limited to this, and a pressurized fluid supply device may be used, for example. It is also possible to separately install and supply the pressurized fluid into the protective tube 21 from the outside.

Further, in the above embodiment, the pressurized air is used to increase the internal pressure of the protection tube 21, but the present invention is not limited to this, and another gas may be used as long as it does not impair the heating function. When the pressurized fluid supply device is separately provided as described above, it is also possible to employ a liquid as the pressurized fluid.

Further, although the direct heating type is shown in the above embodiment, the indirect heating type may be used in combination with this.

(Effect of the Invention) As described above, according to the present invention, the pressurized fluid is supplied by the pressurized fluid supply means into the protective tube made of the refractory material that projects into the crucible and has the heating means built therein.
By minimizing the difference between the pressure acting on the molten metal of the pressurized air and the pressure acting on the inner wall of the protective tube of the pressurized fluid, the metallic sodium added for refining the cast structure in the molten metal is Penetration into the protective tube can be suppressed, and thus the life of the protective tube and the heating means can be extended.

[Brief description of drawings]

The drawing is a vertical cross-sectional view of a low-pressure casting machine including a hot water pool heat retaining device according to an embodiment of the present invention. 4 ... crucible, 12 ... stalk, 15 ... supply pipe, 1
9 ... Mold, 20 ... Cavity, 21 ... Protective tube, 2
4 ... Heating coil, 26 ... Closed chamber, 28 ... Communication passage,
31 ... Pressurized fluid supply means, A ... Molten metal

Claims (1)

[Claims] 1. A low pressure casting machine in which a molten metal in a crucible kept at a predetermined temperature is supplied to a cavity of a mold through a stalk by applying pressure of pressurized air to the molten metal surface. 1. A hot water pool heat retaining device for a low-pressure casting machine, comprising: a protection tube made of a refractory material protruding into the interior thereof and made of a refractory material; and a pressurized fluid supply means for supplying a pressurized fluid into the protection tube.