Low-pressure casting apparatus

Abstract

To provide a low-pressure caster capable of stably producing a quality casting by correctly measuring a surface height of melt in a pressurization chamber or melt-feed chamber and appropriately controlling the charge state of melt into a metal-mold cavity.SOLUTION: A low-pressure caster, for introducing a pressurization gas regulated in pressure and flow rate into a hermetically-sealed pressurization chamber, controlling the surface height of melt in the pressurization chamber to raise the surface of melt in a melt-feed chamber communicating with the pressurization chamber and regulating the charge state of melt into a metal-mold cavity, comprises, for the pressurization chamber, a melt-surface sensor that measures a surface height of melt, a pressurization-gas introducing unit for introducing a pressurization gas and a pressurization-gas introducing pipe connecting between the pressurization-gas introducing unit and the pressurization chamber so as to release the pressurization gas into the pressurization chamber. The pressurization-gas introducing pipe comprises an introducing pipe tip for adjusting the release angle of the pressurization gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a low-pressure casting apparatus that introduces pressurized gas with adjusted pressure and flow rate into a sealed pressurized chamber, controls the molten metal surface height in the pressurized chamber, raises the molten metal surface in the hot water supply chamber communicating with the pressurized chamber, and adjusts the filling state of the molten metal into the mold cavity.

Background Art

[0002] Casting apparatuses used for casting and molding molten metal such as aluminum alloy into a mold cavity are classified into horizontal casting apparatuses and vertical casting apparatuses. The horizontal casting apparatus uses a hot water supply robot or the like to supply a predetermined amount of molten metal from a melting furnace to an injection sleeve, and advances the plunger at high speed and high pressure to perform filling and pressurization. The excess molten metal is cooled and solidified in the injection sleeve, cut from the casting product, recovered in the melting furnace, remelted, and reused for casting and molding. It is considered suitable for casting and molding large products and thin-walled products, but it is likely to cause turbulence in the molten metal flow during filling, and it is desirable to take measures against casting defects caused by turbulence in the molten metal flow such as entrainment of air and gas, voids and blisters, molten metal dips, molten metal boundaries, and casting fins.

[0003] On the other hand, in the vertical casting apparatus, the molten metal in the pressurized chamber is pressed, and the pressed molten metal flows through the hot water supply pipe and is filled and pressurized into the mold cavity. The excess molten metal flows through the hot water supply pipe and is recovered in the molten metal holding furnace without being cooled and solidified, mixed with the molten metal in the molten metal holding furnace, and used for the next shot of casting and molding. Therefore, the recovery efficiency of the molten metal is higher than that of the horizontal casting apparatus. In addition, there is less turbulence in the molten metal flow during filling, and casting defects caused by turbulence in the molten metal flow can be suppressed, and it is considered suitable for casting and molding parts that require airtightness and product strength. In addition, a low-pressure casting apparatus that introduces pressurized gas with adjusted pressure and flow rate into a sealed pressurized chamber, controls the molten metal surface height in the pressurized chamber, raises the molten metal surface in the hot water supply chamber communicating with the pressurized chamber, and adjusts the filling state of the molten metal into the mold cavity is widely adopted at the site of casting and molding using a vertical casting apparatus due to advantages such as simplification of the apparatus and the effect of preventing oxidation of the molten metal by sealing. In the present invention, this low-pressure casting apparatus is the target.

[0004] In low-pressure casting equipment, accurately measuring the molten metal level in the pressurizing chamber or molten metal supply chamber is desirable in order to precisely control the state of molten metal filling into the mold cavity. For example, it has been proposed to measure the molten metal level using a cylindrical body equipped with a molten metal level detection means, as shown in Patent Document 1. According to this method, the molten metal level can be accurately measured by removing molten metal oxides floating on the surface. However, the molten metal level detection means shown in Patent Document 1 is a contact-type detection sensor that can detect the molten metal level by contacting it, and can only detect the molten metal level at preset measurement positions and measurement points, such as upper and lower limit molten metal level positions, and cannot measure continuous changes in the molten metal level that are linked to the state of molten metal filling into the mold cavity.

[0005] Therefore, it has been proposed to use non-contact sensors such as ultrasonic sensors and laser sensors, as shown in Patent Document 2. This makes it possible to measure the continuous change in the molten metal level in conjunction with the filling state of the molten metal in the mold cavity. Furthermore, it is said that the accuracy of measuring the molten metal level can be improved by floating a reflector on the molten metal surface. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 1-143754 [Patent Document 2] Japanese Patent Application Publication No. 7-75865 [Overview of the project] [Problems that the invention aims to solve]

[0007] In Patent Document 1, since the inside of the cylinder is not completely sealed, oxidation of the molten metal gradually progresses, and it is thought that molten metal oxides float inside the cylinder. Similarly, in Patent Document 2, it is thought that molten metal oxides due to oxidation of the molten metal will also float. As a result, as time passes, the increase in molten metal oxides floating on the surface makes it difficult to accurately measure the height of the molten metal inside the cylinder. In Patent Document 2, it is stated that accurate measurement of the molten metal height can be achieved regardless of the floating of molten metal oxides by using a reflector floating on the surface of the molten metal. However, due to the fluctuation phenomenon of the molten metal surface, the reflector shakes greatly, and as a result, the reflected waves of ultrasonic sensors and laser sensors are disturbed, and the accuracy of measuring the molten metal height is greatly reduced. In other words, in Patent Documents 1 and 2, the accuracy of measuring the molten metal height is unstable, making it difficult to control the state of filling the mold cavity with molten metal, and thus making it difficult to ensure the stable production of high-quality castings.

[0008] Therefore, the present invention aims to provide a low-pressure casting apparatus that accurately measures the molten metal level in the pressurizing chamber or the molten metal supply chamber, appropriately controls the filling state of the molten metal into the mold cavity, and enables stable production of high-quality castings. [Means for solving the problem]

[0009] The low-pressure casting apparatus of the present invention is In a low-pressure casting apparatus that introduces pressurized gas with adjusted pressure and flow rate into a sealed pressurized chamber, controls the height of the molten metal surface in the pressurized chamber, raises the molten metal surface in a molten metal supply chamber connected to the pressurized chamber, and adjusts the state of molten metal filling into the mold cavity, The pressurized chamber includes a water level sensor for measuring the water level, a pressurized gas introduction unit for introducing the pressurized gas, and a pressurized gas introduction pipe connecting the pressurized gas introduction unit and the pressurized chamber and releasing the pressurized gas into the pressurized chamber. The pressurized gas introduction pipe is characterized by having an introduction pipe tip portion that adjusts the discharge angle of the pressurized gas.

[0010] In the low-pressure casting apparatus of the present invention, Preferably, the cross-sectional area of ​​the path through which the pressurized gas passes at the tip of the introduction pipe is equal to or greater than the cross-sectional area of ​​the path through which the pressurized gas passes in the pressurized gas introduction pipe.

[0011] Furthermore, in the low-pressure casting apparatus of the present invention, Preferably, the molten metal level sensor is a laser displacement meter, and the height of the molten metal level is measured from the time difference between the laser irradiation wave irradiated from the laser displacement meter toward the molten metal in the pressurized chamber and the laser reflected wave reflected by the molten metal. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a low-pressure casting apparatus that accurately measures the molten metal level in the pressurizing chamber or the molten metal supply chamber, appropriately controls the filling state of the molten metal into the mold cavity, and enables stable production of high-quality castings. [Brief explanation of the drawing]

[0013] [Figure 1] This is a conceptual diagram showing a low-pressure casting apparatus according to the present invention. [Figure 2] This figure shows an embodiment using the low-pressure casting apparatus shown in Figure 1. [Modes for carrying out the invention]

[0014] Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions of each claim. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solutions of the inventions of each claim. Also, in these embodiments, the scale and dimensions of some components may be exaggerated, or some components may be omitted.

[0015] (Low-pressure casting apparatus) First, the low-pressure casting apparatus according to the present invention will be described with reference to FIG. 1. The low-pressure casting apparatus 100 shown in FIG. 1 includes a molten metal holding furnace 10, a pressurizing chamber 20, a ladle chamber 30, a communication chamber 40, and a casting mold 50.

[0016] The casting mold 50 is disposed above the ladle chamber 30 and includes a fixed mold 52 supported by a fixed plate 51 and a movable mold 54 supported by a movable plate 53. By operating a mold clamping device (not shown) to clamp the fixed mold 52 and the movable mold 54, a mold cavity 55 is formed. Further, the fixed mold 52 is provided with a gate 55G for filling the mold cavity 55 with molten metal. The fixed mold 52 and the movable mold 54 are heated and controlled to an appropriate temperature for the flow and cooling of the molten metal filled in the mold cavity 55 by heating means (not shown) or the like. Further, if necessary, a mold release agent is applied to the mold cavity 55 before filling with the molten metal.

[0017] The molten metal holding furnace 10 stores a molten metal M in which a metal material such as an aluminum alloy, which is appropriately selected according to the use of the cast product or the like and adjusted to a predetermined composition, is melted and held at a predetermined temperature. Therefore, it includes temperature adjusting means 13 such as an electric heater. Further, the opening and closing valve 11 is operated by an opening and closing control unit 12, and a predetermined amount of the molten metal M is periodically supplied from the molten metal holding furnace 10 to the communication chamber 40. Further, means for producing the molten metal M such as a melting furnace may be provided separately, and the molten metal M may be periodically replenished to the molten metal holding furnace 10. Further, by closing the lid 14, the inside of the molten metal holding furnace 10 becomes airtight, and it is preferable to fill the inside of the molten metal holding furnace 10 with an inert gas such as argon or nitrogen using an inert gas supply device (not shown) to prevent oxidation of the molten metal M in the molten metal holding furnace 10.

[0018] The communication chamber 40 stores the molten metal M supplied from the molten metal holding furnace 10. The molten metal M in the communication chamber 40 is held at a predetermined temperature by temperature adjusting means 41 such as an electric heater. Further, the molten metal M in the communication chamber 40 is connected to the pressurizing chamber 20 and the ladle chamber 30.

[0019] The molten metal supply chamber 30 is located below the casting mold 50 and stores molten metal M connected to the communication chamber 40 inside. The molten metal supply chamber 30 is equipped with temperature control means (not shown), and the molten metal M in the molten metal supply chamber 30 is heated and maintained at a predetermined temperature, similar to the communication chamber 40. The molten metal supply chamber 30 and the gate 55G of the casting mold 50 are connected by a molten metal supply pipe 31, and the molten metal M in the molten metal supply chamber 30 is filled into the mold cavity 55 via the molten metal supply pipe 31. For this purpose, the molten metal supply pipe 31 is made of a ceramic material that has heat insulation properties and low wettability with the molten metal M. Furthermore, it is preferable that the molten metal supply pipe 31 and the gate 55G are heated and maintained at a predetermined temperature using temperature control means (not shown) to stabilize the temperature of the molten metal M flowing through the molten metal supply pipe 31.

[0020] The pressurized chamber 20 is located in a different position from the hot water supply chamber 30 and stores molten metal M connected to the communication chamber 40 inside. The pressurized chamber 20 is equipped with temperature control means (not shown), and the molten metal M in the pressurized chamber 20 is heated and maintained at a predetermined temperature, similar to the communication chamber 40 and the hot water supply chamber 30. By closing the top of the pressurized chamber 20 with an airtight member 27, a sealed space 21 is formed between the molten metal M and the airtight member 27. The airtight member 27 is also equipped with a pressurized gas introduction pipe 22, and pressurized gas with adjusted pressure and flow rate is introduced into the space 21 from the pressurized gas introduction section 23 via the pressurized gas introduction pipe 22. As a result, the pressure in the space 21 rises, and the molten metal M in the pressurized chamber 20 is compressed, causing the molten metal level to drop. The compressed molten metal M in the pressurized chamber 20 flows into the hot water supply chamber 30 via the communication chamber 40, causing the molten metal level in the hot water supply chamber 30 to rise. As a result, the molten metal M in the hot water supply chamber 30 is filled into the mold cavity 55 via the hot water supply pipe 31 and gate 55G, and pressurized. This series of operations carries out the casting process.

[0021] Here, the degree of change in the molten metal level M in the pressure chamber 20 is related to the control of the filling state of the molten metal M in the mold cavity 55. Therefore, it is preferable to provide a molten metal level sensor that accurately measures the change in the molten metal level M in the pressure chamber 20. Using this molten metal level sensor, the introduction control of the pressurized gas by the pressurized gas introduction section 23 is accurately performed. Since the pressure chamber 20 has a sealed structure, it is preferable to arrange the molten metal level sensor outside the pressure chamber 20. Further, since the molten metal M in the pressure chamber 20 is in a relatively high temperature state, it is preferable to arrange the molten metal level sensor at a position away from the pressure chamber 20 from the viewpoint of protection against heat. Therefore, in the present invention, a laser displacement meter 24 is used as the molten metal level sensor that can accurately measure the change in the molten metal level from a remote position. The laser irradiation wave emitted from the laser displacement meter 24 passes through the transparent measurement window 26 provided in the airtight member 27 and reaches the molten metal level MH of the molten metal M in the pressure chamber 20. The laser irradiation wave is reflected by the molten metal level MH and becomes a laser reflected wave. This laser reflected wave passes through the measurement window 26 and is received by the laser displacement meter 24. The measurement unit 25 connected to the laser displacement meter 24 calculates the time difference between the laser irradiation wave and the laser reflected wave and measures it as the molten metal level of the molten metal M. Specifically, it will be described using FIG. 2.

[0022] Note that inexpensive compressed air may be used as the pressurized gas introduced into the space portion 21, but from the viewpoint of stabilizing the quality by preventing oxidation of the molten metal M in the pressure chamber 20, it is preferable to use an inert gas such as argon or nitrogen. In that case, it is preferable to maintain the pressure chamber 20 in a state filled with the inert gas. Also, in the case of nitrogen gas, a nitrogen gas generator that separates and collects only nitrogen gas from the air using a separation membrane, an adsorption membrane, etc. may be used for the pressurized gas introduction section 23. Similarly, it is more preferable to fill the hot water supply chamber 30 and the hot water supply pipe 31 with an inert gas such as argon or nitrogen to prevent oxidation of the molten metal M. Further, by reducing the pressure of the pressurized gas introduced into the pressure chamber 20, the molten metal level of the molten metal M in the hot water supply chamber 30 drops, and the molten metal M remaining in the hot water supply pipe 31 can be recovered into the hot water supply chamber 30.

[0023] (Measurement of molten metal level) Next, an embodiment for measuring the molten metal level in the pressurized chamber 20 using the low-pressure casting apparatus 100 shown in Figure 1 will be described with reference to Figure 2. Figure 2(a) shows the prior art, and Figures 2(b) to (d) show embodiments according to the present invention. In Figures 2(a) to (d), the pressurized gas introduction pipe 22 attached to the airtight member 27 is positioned from the upper surface of the pressurized chamber 20 toward the molten metal M below. Also, in all figures, the molten metal level in the pressurized chamber 20 is measured from a laser displacement meter 24 placed at a distance via a measurement window 26. Other parts are omitted from the diagram.

[0024] First, in the conventional technology shown in Figure 2(a), the pressurized gas introduced towards the space 21 is forcefully discharged from the pressurized gas introduction pipe 22 and collides with the molten metal surface MH of the molten metal M, causing the molten metal surface MH to undergo a large oscillation phenomenon. As a result, the laser irradiation wave RS emitted from the laser displacement meter 24 is greatly disturbed by the oscillating molten metal surface MH, making it impossible to accurately measure the molten metal height. Let Q1 be the cross-sectional area through which the pressurized gas passes in the pressurized gas introduction pipe 22, and G1 be the discharge velocity of the pressurized gas from the outlet of the pressurized gas introduction pipe 22 at this time.

[0025] Next, as shown in Figure 2(b), the tip 221 of the inlet pipe, which adjusts the release angle of the pressurized gas, is positioned at the tip of the pressurized gas inlet pipe 22. This allows the direction of the pressurized gas released into the space 21 to be changed, preventing the released pressurized gas from directly colliding with the molten metal surface MH of the molten metal M, and suppressing the oscillation phenomenon of the molten metal surface MH. As a result, the molten metal surface MH in the pressurized chamber 21 can be kept smooth, and accurate measurement of the molten metal surface height of the molten metal M can be ensured without disturbance of the laser reflected wave RH from the molten metal surface MH. In Figure 2(b), the release angle of the pressurized gas is set horizontally with respect to the molten metal surface MH, and there are four pressurized gas outlets. However, this is not limited to this, and for example, the gas may be released upward away from the molten metal surface MH, or released away from the laser irradiation wave RS and the laser reflected wave RH. Also, the number of outlets may be fewer than four, or more than four.

[0026] Here, in Figure 2(b), the cross-sectional area Q2 through which the pressurized gas released from the tip 221 of the inlet pipe passes is equal to or greater than the cross-sectional area Q1 (Q2≧Q1). This reduces the release rate G2 of the pressurized gas released from the tip 221 of the inlet pipe (G2≦G1), ensuring a calming effect on the oscillating phenomenon of the molten metal surface MH.

[0027] Next, as shown in Figure 2(c), an introduction tube tip 222 for adjusting the release angle of pressurized gas is placed at the tip of the pressurized gas introduction tube 22. This allows the direction of the pressurized gas released into the space 21 to be changed, preventing the released pressurized gas from directly colliding with the molten metal surface MH of the molten metal M, and suppressing the oscillation phenomenon of the molten metal surface MH. Furthermore, the cross-sectional area Q3 through which the pressurized gas released from the introduction tube tip 222 passes is set to be equal to or greater than the cross-sectional area Q1 (Q3≧Q1). This reliably reduces the release velocity G3 of the pressurized gas released from the introduction tube tip 222 (G3≦G1), ensuring the stabilization of the molten metal surface MH. As a result, the laser reflected wave RH from the molten metal surface MH is not disturbed, enabling highly accurate measurement of the molten metal surface height.

[0028] In Figure 2(c), the release angle of the pressurized gas is set to be horizontal to the molten surface MH and in a different direction from the laser irradiation wave RS and the laser reflected wave RH. However, the method is not limited to this, and for example, the pressurized gas may be released in the direction of the laser irradiation wave RS and the laser reflected wave RH. In this case, it is expected that foreign matter floating on the surface of the molten surface MH can be moved away from the measurement position for the molten surface height without causing the molten surface MH to oscillate, thereby avoiding measurement errors in the molten surface height caused by floating matter. Furthermore, by directing the release angle of the tip of the introduction pipe 222 toward the measurement window 26, it is possible to prevent foreign matter from adhering to the measurement window 26, and it is expected that accurate measurement of the molten surface height can be maintained by ensuring the transmission of the laser irradiation wave RS and the laser reflected wave RH through the measurement window 26.

[0029] Next, adjacent to the pressurized gas introduction pipe 22 shown in Fig. 2(a), as shown in Fig. 2(d), a tip portion 223 of the introduction pipe for adjusting the discharge angle of the pressurized gas is separately arranged. The pressurized gas discharged from the pressurized gas introduction pipe 22 has its discharge angle greatly changed by the tip portion 223 of the introduction pipe, avoiding collision with the molten metal surface MH and suppressing the swaying phenomenon of the molten metal surface MH. At this time, the cross-sectional area Q4 surrounded by the tip portion 223 of the introduction pipe and the pressurized gas introduction pipe 22 is set to be equal to or larger than the cross-sectional area Q1 (Q4≥Q1). Thereby, the discharge velocity G4 of the pressurized gas discharged from the tip portion 223 of the introduction pipe is reduced (G4≤G1), ensuring the calming of the molten metal surface MH, enabling accurate measurement of the molten metal surface height by the laser displacement meter 24, and enabling precise control of the filling state of the molten metal M into the mold cavity 55.

[0030] Also, the tip portion 223 of the introduction pipe is set to discharge a slight amount of pressurized gas G5 (G5 < G4) toward the molten metal surface MH. By discharging this slight amount of pressurized gas G5, while suppressing the swaying of the molten metal surface MH, foreign substances floating on the molten metal surface MH can be completely removed. Thereby, the measurement error of the molten metal surface height due to floating substances can be reliably suppressed.

[0031] Note that the tip portions (221 to 223) of the introduction pipe shown in Figs. 2(b) to 2(d) are arranged at the tip of the pressurized gas introduction pipe 22, but the pressurized gas introduction pipe 22 may be set like the tip portions (221 to 223) of the introduction pipe. Also, although the pressurized gas introduction pipe 22 is one, a plurality of arrangements may be used, or a plurality of tip portions (221 to 223) of the introduction pipe may be arranged in combination.

[0032] (Effect) In this low-pressure casting apparatus 100, which adjusts the filling state of molten metal into the mold cavity 55 by introducing pressurized gas from a pressurized gas introduction pipe 22 into a sealed pressurized chamber 20 to control the height of the molten metal surface in the pressurized chamber 20, thereby raising the height of the molten metal surface in the molten metal supply chamber 30 which is connected to the pressurized chamber 20, the introduction pipe tip (221~223) has an increased cross-sectional area through which the pressurized gas passes, and a laser displacement meter 24 is provided that irradiates a laser irradiation wave RS toward the molten metal surface MH and measures the height of the molten metal surface from the time difference between the laser reflected wave RH reflected from the molten metal surface MH. This suppresses and calms the fluctuation phenomenon of the molten metal surface MH, allows for accurate measurement of fluctuations in the height of the molten metal surface in the pressurized chamber 20, and enables precise control of the rise of the molten metal surface in the molten metal supply chamber 30, thereby properly controlling the filling state of molten metal into the mold cavity 55. As a result, stable production of high-quality castings becomes possible.

[0033] Furthermore, a high-precision low-pressure casting apparatus 100 can be provided with a simple and inexpensive modification that only requires adding the tip sections (221-223) of the introduction pipes, without requiring any major modifications to the existing low-pressure casting apparatus 100.

[0034] Although preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the embodiments described above. Various modifications or improvements can be made to the above embodiments. [Explanation of symbols]

[0035] 100 Low-pressure casting apparatus 10 Molten metal holding furnace 11. Shut-off valves 12 Opening / Closing Control Unit 13, 41 Temperature adjustment means 14 Lid 20 Pressurized chamber 21 Space section 22 Pressurized gas introduction pipe 221-223 Tip of the inlet pipe 23 Pressurized gas introduction section 24 Laser displacement meter 25 Measurement section 26 Measurement window 27 Airtight components 30 Kitchenette 31 Hot water pipe 40 Communication room 50 Casting molds 51 Fixed plate 52 Fixed molds 53 Movable plate 54. Movable mold 55 Mold Cavity 55G Gate M molten metal MH hot water surface RS laser irradiation wave RH laser reflected waves Q1~Q4 Passage cross section G1~G5 release rate

Claims

1. In a low-pressure casting apparatus that introduces pressurized gas with adjusted pressure and flow rate into a sealed pressurized chamber, controls the height of the molten metal surface in the pressurized chamber, raises the molten metal surface in a molten metal supply chamber connected to the pressurized chamber, and adjusts the state of molten metal filling into the mold cavity, A water level sensor for measuring the water level height, A pressurized gas introduction unit for introducing the pressurized gas into the pressurized chamber, A pressurized gas introduction pipe connects the pressurized gas introduction section and the pressurized chamber, and releases the pressurized gas into the pressurized chamber in a discharge direction such that the pressurized gas directly collides with the surface of the molten metal in the pressurized chamber. An introduction pipe tip portion attached to the tip of the pressurized gas introduction pipe so as to cover the tip, wherein the forward portion of the pressurized gas from the pressurized gas introduction pipe in the discharge direction is closed, and the introduction pipe tip portion has a discharge port for discharging the pressurized gas in a direction different from the discharge direction and in a direction that does not directly collide with the surface of the molten metal in the pressurized chamber, A low-pressure casting apparatus characterized by being equipped with the following features.

2. The discharge port is formed on the side wall of the tip of the inlet pipe. The low-pressure casting apparatus according to claim 1.

3. In a low-pressure casting apparatus that introduces pressurized gas with adjusted pressure and flow rate into a sealed pressurized chamber, controls the height of the molten metal surface in the pressurized chamber, raises the molten metal surface in a molten metal supply chamber connected to the pressurized chamber, and adjusts the state of molten metal filling into the mold cavity, A water level sensor for measuring the water level height, A pressurized gas introduction unit for introducing the pressurized gas into the pressurized chamber, A pressurized gas introduction pipe connects the pressurized gas introduction section and the pressurized chamber, and releases the pressurized gas into the pressurized chamber in a discharge direction such that the pressurized gas directly collides with the surface of the molten metal in the pressurized chamber. The tip of the pressurized gas inlet pipe has a first discharge port for discharging the pressurized gas in a direction different from the discharge direction of the pressurized gas from the pressurized gas inlet pipe and in a direction that does not directly collide with the surface of the molten metal in the pressurized chamber, the tip of the pressurized gas inlet pipe has a shielding wall in the forward portion in the discharge direction, and the shielding wall has a second discharge port at a position offset from the discharge direction, A low-pressure casting apparatus characterized by being equipped with the following features.

4. The low-pressure casting apparatus according to any one of claims 1 to 3, wherein the cross-sectional area of ​​the path through which the pressurized gas passes at the tip of the introduction pipe is equal to or greater than the cross-sectional area of ​​the path through which the pressurized gas passes in the pressurized gas introduction pipe.

5. The low-pressure casting apparatus according to any one of claims 1 to 3, wherein the molten metal level sensor is a laser displacement meter, and the height of the molten metal level is measured from the time difference between a laser irradiation wave irradiated from the laser displacement meter toward the molten metal in the pressurized chamber and a laser reflected wave reflected by the molten metal.

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