JP2010240732A - Casting apparatus and casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a casting apparatus which is excellent in quality, high in safety, small in energy consumption and heat loss and easy in maintenance, and to provide a casting method. <P>SOLUTION: The casting apparatus produces a casting by melting or half-melting a metal or an alloy and pouring it from a furnace to a casting mold. The apparatus includes: (1) a casting mold having a molten metal introducing means for introducing molten metal; (2) a molten metal driving means for introducing the molten metal into the molten metal introducing means with a pressure ≤0.2 MPa; and (3) a U-shaped pipe which is connected at one end to the molten metal introducing means and at the other end to the molten metal driving means and which is immersed in the molten metal in the furnace. In the casting apparatus, the molten metal introducing means is an opening/closing member for opening/closing between the U shaped pipe and the casting mold, or a sleeve having two plunger tips drivable independently, while the molten metal driving means is (a) a plunger and a driving device for the plunger, and a device having an airtight furnace for gas pressurization through the plunger or (b) a device having an airtight furnace capable of pressurization and evacuation. The invention also includes a casting method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a novel casting apparatus and casting method.

  A casting method in which a metal or alloy is melted or semi-molten and poured into a mold to produce a cast product is used for manufacturing various automobile parts, mechanical / electrical parts, and the like. In particular, die casting methods are frequently used for Al alloy and Mg alloy castings, but gravity die casting methods, low pressure casting methods, vacuum suction methods, and the like are also employed (Non-Patent Documents 1 and 2, 3).

  In the die casting method and the gravity mold casting method, a molten alloy or molten metal (hereinafter referred to as “molten metal”) is often supplied to a casting apparatus by a ladle, the surface of the molten metal is oxidized, and an oxide film is caught in the product to cause defects. It becomes. Moreover, since the contact time between the molten metal and the ladle and the atmosphere is long, heat loss due to heat radiation is large. In addition, the die casting method has the advantage of high productivity. However, since the air and gasified lubricant are injected together with the molten metal in the sleeve at high pressure and high speed, they are easily caught and defects are likely to occur, and energy consumption is reduced. Many.

  In the low pressure casting method, the hot metal surface in the holding furnace is pressurized with gas, or an electromagnetic pump is immersed in the molten metal to supply the molten metal to the mold cavity. However, in the gas pressurization of the entire furnace, it is not easy to control the molten metal supply amount, the working environment is bad, and the furnace is difficult to maintain. The use of the electromagnetic pump is good in terms of the work environment, but the efficiency of the electromagnetic pump is low, which is a problem in terms of energy saving. In addition, the vacuum suction method that decompresses the mold cavity and sucks the molten metal using this decompression is the best environmentally and uses less energy, but the degree of decompression is small and control of gas entrainment in the mold However, it is not easy, and if the airtightness is poor, a gas is entrained and defects increase. Furthermore, these methods have a big problem that productivity is poor as compared with the die casting method.

  In order to prevent entrainment of air or the like in the die casting method, Patent Document 1 discloses a method in which two plunger chips in a sleeve are opened from a closed state to create a decompression space between the plunger chips, thereby sucking molten metal. Has proposed. In this method, there is less air in the sleeve as in the conventional die casting method, and only gas (usually air) in the space from the molten metal surface to the plunger tip is caught in the sleeve, and the quality is improved. Therefore, it is necessary to devise a method for controlling the molten metal surface as close to the plunger tip as possible.

  Further, Patent Document 2 proposes a die casting method in which a molten metal is supplied to the sleeve by pressurizing the molten metal surface in the same manner as in low-pressure casting, but it is not easy to supply an appropriate amount of molten metal. Moreover, it is necessary to seal all the furnaces, which is a problem in a large apparatus.

  In contrast, the inventor of the present invention has invented a casting apparatus in which an opening / closing member having an opening is provided on the upper part of the stalk and the plunger in the stalk is driven from the outside of the holding furnace (Patent Document 3). This equipment removes the oxide film on the molten metal surface and can supply only clean molten metal to the mold, and it can pressurize the molten metal, so the quality is better than the low pressure casting method and the productivity is equivalent to the die casting method. There is a risk that the shaft will solidify in the part that passes through the holding furnace, making it difficult to drive.

  As described above, the conventional casting apparatus or casting method has problems in casting quality, productivity, heat loss due to heat radiation, oxidation of the molten metal surface, energy used, safety, and the like, and these solutions are desired.

JP 2000-24767 A Japanese Patent Application No. 2006-343512 Japanese Patent Application No. 2009-11077

Ohnaka Ikuo, Melt Processing, Corona (2004) Raw material, Vol. 44 (2003) 1, 6 Material Center Die Casting Technology Outlook (19988.6) Japan Die Casting Association

  The main object of the present invention is to provide a casting apparatus and a casting method that are of higher quality, higher safety, less energy used and less heat loss, and easier maintenance.

  As a result of intensive studies in view of the problems of the prior art, the present inventor has found that the above object can be achieved by a specific method, and has completed the present invention.

That is, the present invention relates to the following casting apparatus and casting method.
1. A casting apparatus for producing a casting by injecting a molten metal or alloy in a molten or semi-molten state from a furnace into a mold, 1) a mold having a molten metal introduction means for introducing molten metal,
2) a molten metal driving means for introducing the molten metal into the molten metal introducing means at a pressure of 0.2 MPa or less, and 3) one end connected to the molten metal introducing means, the other end connected to the molten metal driving means, and the inside of the furnace U-shaped pipe immersed in molten metal,
1. A casting apparatus characterized by comprising: The molten metal introducing means is installed between the U-shaped pipe and the mold, 1) an opening, and 2) a cavity provided on the U-shaped pipe side to remove a part of the molten metal. 3) A member for opening and closing the U-shaped pipe having an exhaust groove for exhausting gas or air in the trap and the U-shaped pipe on the U-shaped pipe side or the upper part of the trap. 2. The casting apparatus according to 1. The molten metal introducing means is a cylindrical sleeve, and is opened from a state in which 1) an opening to the mold, 2) an opening to the U-shaped pipe, 3) an opening to the U-shaped pipe is closed. Thus, two plunger tips that can be driven independently to create a decompression space in the sleeve, and after the melt flows into the decompression space, move the melt further into the opening to the mold and inject, 3. The casting apparatus according to 1, which has The molten metal driving means includes 1) a plunger provided in the U-shaped pipe, 2) a driving device for driving the plunger, 3) an opening provided on a side surface of the U-shaped pipe near the plunger, 4) U In addition to the molten metal driving means described in the casting apparatus 5.4 according to 1, the apparatus has a gas introduction groove and a pressure means for introducing pressurized gas into the gap between the letter-shaped pipe and the plunger. The molten metal driving means described in the casting apparatus 6.1 according to 1, which is a plunger having a molten metal pressure groove for introducing gas and a gas pressure means, is an airtight furnace capable of pressurization and decompression,
1) Arranged to cover a part of the furnace so as to prevent heat dissipation from the furnace,
2) having a pressurizing port and a depressurizing port for connecting to the pressurizing unit and the depressurizing unit;
3) Consists of a main room and sub-chamber separated by a dam at the bottom,
4) The U-shaped pipe is connected to the main chamber, and the volume of the main chamber is larger than that of the sub chamber,
5) A suction pipe for sucking molten metal in the furnace is connected to the sub chamber,
6) The main chamber stopper according to 7.6, wherein the main chamber stopper has a main chamber stopper that opens and closes the U-shaped pipe in the main chamber, and a sub chamber stopper that opens and closes the suction pipe in the sub chamber. 2. The seal part capable of opening and closing the U-shaped pipe is provided on the outside, the plunger part capable of pressurizing the molten metal in the U-shaped pipe is provided on the inside, and the seal part and the plunger part can be driven independently. Casting device 8. A casting method for producing a cast product by introducing a molten metal in a furnace into a mold through a molten metal introducing means,
1) Immersion of the U-shaped pipe into the furnace and a preparatory process for flowing the molten metal into the hermetic furnace described in 6) 2) A first process of supplying the molten metal to the molten metal introducing means at a low pressure of 0.2 MPa or less 3) The second step of introducing the molten metal into the mold from the molten metal introducing means 4) The third step of flowing the molten metal into the U-shaped pipe 5) The solidified cast product is taken out, the mold is cleaned, and the mold is closed to close the mold A casting method comprising the fourth step, wherein the first step to the fourth step are repeated until the molten metal level in the U-shaped pipe is lowered to a certain limit or more.
As the molten metal driving means described in 9.8, the plunger described in 4 or 5 is used, and as the molten metal introducing means, the opening / closing member described in 2 is used, and in the first step, A trap that is a cavity provided on the side is positioned on the U-shaped pipe, and the molten metal in the trap is removed by moving the opening and closing member when the molten metal flows into the trap. In the first step and the second step or the second step described in the casting method 10.9 according to 8, the opening of the member is positioned on the U-shaped pipe and the process proceeds to the second step. The sleeve and the plunger tip described in 3 are used as the molten metal introducing means described in the casting method 11.8 described in 8, in which the molten metal is introduced into the mold while reducing the pressure and adjusting the speed at which the plunger is pushed down. Casting As the molten metal driving means described in Method 12.8, the airtight furnace described in 6 is used, and in the preparation step, the U-shaped pipe is closed with the main chamber stopper or a seal portion of the main chamber stopper, Open the chamber stopper, depressurize the hermetic furnace and suck the molten metal in the main furnace into the hermetic furnace, then open the main chamber stopper, let the molten metal in the hermetic furnace flow out into the U-shaped pipe, The stopper is opened, and the molten metal overflowing from the dam and returning to the main furnace is returned to the main furnace, and the molten metal is applied at a pressure of 0.2 MPa or less by pressurization in the airtight furnace or driving of the plunger portion of the main chamber stopper. The first step of supplying the molten metal to the molten metal introducing means The second step, the step of introducing the molten metal into the mold by the molten metal introducing means using the opening and closing member according to 2 or the sleeve and the plunger tip according to 3, the second step, pressurizing Stop or be The molten metal introducing means described in the casting method 13.12 according to 8, wherein the step of opening the seal of the U-shaped pipe and causing the molten metal to flow into the U-shaped pipe is the third step, 9. The casting method according to 8, wherein in at least the second step, the inside of the mold is decompressed and the airtight chamber is decompressed, and the molten metal is introduced while adjusting the degree of decompression in the mold.

According to the casting apparatus and the casting method of the present invention, it is possible to manufacture a higher-quality cast product that is easy to maintain and highly safe, uses less energy and heat loss.
More specifically, the following effects (1) to (10) can be obtained.

(1) Since the U-shaped pipe is immersed in the molten metal, there is less energy loss than when it is taken out to the outside, and it is safe.
(2) Since the plunger drive shaft does not penetrate the holding furnace, it is safe.
(3) Since a large amount of air or the like is not involved as in the die casting method, a high-quality casting with few defects can be manufactured. In addition, since the molten metal is not injected at high pressure and high speed, less energy is used.
(4) Unlike the low-pressure casting, it is not necessary to continue to pressurize the molten metal until the product part is solidified, and it is not necessary to heat the molten metal part so that the solidification of the spout part is delayed the most. Go up.
(5) The drive of the plunger is mechanical, and a more accurate volume of molten metal can be supplied with less energy than pressing a wide molten metal surface and supplying the molten metal as in low pressure casting.
(6) Even when using gas pressurization, the pressurization has a smaller area than the furnace, is easier to control, and uses less energy.
(7) Since the molten metal surface position in the hermetic furnace is high, the moving distance from the molten metal surface position to the molten metal introducing means is short and can be supplied in a shorter time.
(8) Since the upper surface of the furnace can be opened, maintenance is easier than the low pressure casting method in which the entire furnace is sealed.
(9) Since the airtight furnace covers the top of the furnace, there is little heat loss and it is safe even if molten metal leaks in the airtight furnace.
(10) Reduce the pressure in both the airtight furnace and the mold, or slow down the plunger moving speed, or reduce the gas pressure at the front of the plunger, so that the molten metal is gently put into the mold while the mold is further depressurized. Therefore, the hot water is good, the entrainment of gas and oxide film is reduced, and the quality is improved.

It is a front view of Example 1. It is a side view of Example 1. It is another example of the plunger used for Example 1. It is sectional drawing of the other example of the trap part used for Example 1. It is sectional drawing of the molten metal drive means used for Example 2. It is another example of the molten metal drive means used in Example 2. It is sectional drawing of the molten metal introduction means used for Example 3. It is a front view of Example 4. It is process drawing of Example 5.

DESCRIPTION OF SYMBOLS 1 U-shaped pipe 2 Plunger 3 Pipe opening part 4 Furnace 5 Molten metal 6 Opening / closing member 7 Opening part 8 Mold 9 Pressurizing piston 10 Mold cavity 11 Plunger drive shaft 12 Pipe support member 13 Trap 14 Opening / closing member support member 15 Servo Motor 16 Exhaust groove 17 Gate valve 18 Plunger cavity 19 Molten metal pressurized gas inlet 20 Pressurized gas inlet 21 Molten gas pipe 22 Gas outlet groove 23 Sleeve 24 Main plunger tip 25 Secondary plunger tip 26 Sleeve opening 27 27 'Plunger tip drive shaft 28 Opening 29 to the mold Melt introduction means and mold 30 Airtight furnace 31 Main chamber 32 Sub chamber 33 Dam 34 Suction pipe 35 Main chamber stopper 36 Seal 38 Plunger portion 39 Sub chamber stopper 40 Pressurization Port 41 Pressure reducing port 42 Furnace bottom 43 Heater 44 Coagulated material

1. Casting apparatus The casting apparatus of the present invention is an apparatus for producing a cast product by injecting a molten metal or alloy in a molten or semi-molten state from a furnace into a mold, and 1) a mold having a molten metal introducing means for introducing molten metal. ,
2) a molten metal driving means for introducing the molten metal into the molten metal introducing means at a pressure of 0.2 MPa or less, and 3) one end connected to the molten metal introducing means, the other end connected to the molten metal driving means, and the inside of the furnace U-shaped pipe immersed in molten metal,
It is characterized by including.

  The apparatus of the present invention can be applied to Al alloys, Zn alloys, Mg alloys, Cu alloys, Fe alloys, pure Al, pure Cu, and other various alloys and metals.

  The apparatus of the present invention allows the molten metal in the furnace to flow into a U-shaped pipe immersed in the furnace, and the molten metal in the U-shaped pipe is supplied at a low pressure of 0.2 MPa or less via the molten metal introducing means by the molten metal driving means. It is an apparatus for producing a cast product by introducing it into a mold. The molten metal introducing means includes an opening / closing member capable of opening and closing between the mold and the U-shaped pipe, or a sleeve having two plunger chips that can be driven independently. The molten metal driving means includes a plunger and a plunger. It has a driving device or a device using gas pressurization. However, it is also possible to introduce the molten metal into the mold by reducing the pressure of the mold or the molten metal introducing means. In this case, the molten metal driving means acts as a molten metal introducing control means. The mold may be a mold, a sand mold, or a ceramic mold.

  One end of the U-shaped pipe is connected to the molten metal introducing means, and the other end is connected to the molten metal driving means. Since this U-shaped pipe is not subjected to a high pressure as in the die casting method, ceramics which are inferior in pressure resistance but have little reaction with the molten metal can be used. However, metal-based materials and composite materials can be used if there is no problem with the reaction with the molten metal and durability. Note that the shape of the U-shaped pipe does not need to be strictly U-shaped, and it is sufficient that the vicinity of both ends of the pipe faces upward. Further, the cross-sectional shape of the U-shaped pipe is not circular but may be other shapes such as a rectangle, and the dimensions may not be uniform. The U-shaped pipe is usually positioned at the lower part of the mold, but may be a side surface.

  When the opening / closing member is used as the molten metal introducing means, the opening / closing member has at least a driving means capable of reciprocating with the opening, and the opening / closing member is moved to move the opening to the outlet of the U-shaped pipe. By connecting the mold gap portion and the inside of the U-shaped pipe, and not being positioned at the outlet of the U-shaped pipe, the mold gap portion is sealed. The purpose of sealing the mold cavity is to enable the mold cavity to be depressurized or molten metal pressurized. Further, a trap that is a cavity may be provided on the U-shaped pipe side of the opening / closing member. The molten metal surface is usually covered with an oxide film, but when the molten metal surface portion flows into the trap, the opening / closing member is moved here, and this portion is removed, and only the clean molten metal is cast through the opening. Can be introduced. However, in this case, in order to discharge air or gas in the U-shaped pipe, an exhaust groove is provided on the lower surface of the opening / closing member connected to the trap or on the upper portion of the trap. However, if the airtightness around the opening / closing member is not good, the exhaust groove is unnecessary. The cross-sectional shape of the opening / closing member may be rectangular, circular, or other shapes. In addition to metal materials, ceramics and composite materials may also be used. An electric servomotor is used to drive the opening / closing member, but other methods such as a hydraulic servo may be used.

  If a good product cannot be obtained with the opening / closing member, a sleeve having an opening to the mold and an opening to the U-shaped pipe and two plunger tips that can be driven independently can be used. . In this case, with the plunger tip closed, it is positioned at the connection between the sleeve and the U-shaped pipe, and by opening the plunger tip, a decompression space is created in the sleeve, and at the same time in the U-shaped pipe. The molten metal is pushed up by the molten metal driving means, the molten metal is introduced into the sleeve, and after the molten metal is introduced, the two plunger tips are moved simultaneously, and the sucked molten metal is moved to the opening to the mold, and one plunger -It has an electric servo motor and control device for pressurizing the molten metal with a chip and injecting it into the mold. A hydraulic servo motor or the like may be used instead of the electric servo motor.

  One of the molten metal driving means is a plunger connected to a driving device such as an electric servo motor. That is, a plunger is disposed at one end of the U-shaped pipe, and a pipe opening is provided near the plunger. Therefore, when the tip of the plunger is positioned on the pipe opening, the molten metal flows into the U-shaped pipe. The molten metal can be supplied to the molten metal introducing means at the other end of the U-shaped pipe by pushing down the molten metal with the plunger. The molten metal supply amount is estimated from the movement distance and the cross-sectional area of the plunger, and can be controlled by the movement distance of the plunger. In addition, since the pressure which acts on a molten metal by plunger drive is made small as 0.2 Mpa or less, the output of a plunger drive device is small and the energy used is also small.

Also, by introducing an inert gas into the gap between the U-shaped pipe and the plunger, the frictional resistance between the U-shaped pipe and the plunger is reduced to increase the durability, or after the casting is finished, the molten metal that has entered the gap is removed. Can be removed. For this reason, the plunger may be hollow and provided with slits or pores on the side surfaces, or all or part of the plunger may be made of porous ceramics. As the inert gas, depending on the type of the molten metal, N ₂ gas, Ar gas, or the like can be used for an Al alloy or the like. However, when durability does not become a problem, there is no need for such a system for introducing an inert gas into the plunger gap.

  The material of the plunger may be a metal material or a composite material whose surface is protected by ceramics, in addition to the material similar to the U-shaped pipe, but it is desirable to make it hollow with a material difficult to get wet with molten metal to reduce the heat capacity. . You may coat | cover with molten metal and BN which is hard to get wet. It is also possible to increase the durability by sending cooling air from the outside to the plunger portion and cooling it. However, care must be taken not to cause solidification. The larger the gap between the plunger and the U-shaped pipe and the shorter the plunger length, the better the durability. However, since the molten metal easily flows out of the gap, the pressure acting on the molten metal decreases. Therefore, an appropriate gap and length are determined in consideration of a necessary molten metal pressure and durability.

  The plunger may be a melt driving means added with a melt pressurizing gas introduction port and a pressurizing means for sending an inert gas in front of the plunger. In this case, the plunger is mainly used as a stopper for the pipe opening, and after closing the pipe opening, an inert gas is introduced into the front of the plunger from the molten gas pressurized gas inlet, and the molten metal is melted at this pressure. Introduce to the introduction means. In addition, after supplying the molten metal to the mold, the pressurized gas is recovered and the gas pressure is lowered to minimize the consumption amount of the inert gas. As the inert gas, the aforementioned gas can be used.

  In the above, the molten metal in the U-shaped pipe can be sucked by reducing the pressure of the mold or the molten metal introducing means. At this time, the introduction of the molten metal into the mold can be controlled by controlling the pressure of the introduced gas. That is, the smaller the introduced gas pressure and the greater the molten metal flow resistance between the plunger and the U-shaped pipe, the more molten metal can be introduced at a lower flow rate even if the degree of decompression in the mold is increased. Can reduce the amount of entrainment and improve the quality.

  In the case of the molten metal driving by the plunger described above, if it takes too much time for durability or the introduction of the molten metal, as the molten metal driving means, pressurization / decompression or an airtight furnace using the depressurization and the plunger is used. The airtight furnace is installed in the upper part of the furnace to prevent heat dissipation from the furnace and to prevent heat dissipation from the lower part of the airtight furnace, and it is composed of a main chamber with a large volume and a sub chamber with a small volume, and is partitioned by a dam. ing. The U-shaped pipe is connected to the main chamber, the suction pipe for sucking the molten metal in the furnace is connected to the sub chamber, and the U-shaped pipe connected to the main chamber is connected to the sub chamber. Each pipe has a main chamber stopper and a sub chamber stopper. The main chamber stopper is a stopper that can simply airtightly close the end of the U-shaped pipe, or a seal that can airtightly close the end of the U-shaped pipe, and the molten metal in the U-shaped pipe. It is good also as a thing which can have a plunger part which can pressurize inside, and can drive a seal part and a plunger part independently. The hermetic furnace further has a pressurizing port and a depressurizing port connected to a cylinder, a compressor, a vacuum pump, or the like for pressurizing and depressurizing the inside of the hermetic furnace.

  The role of the main chamber stopper and sub chamber stopper is to close the U-shaped pipe and suction pipe, respectively, to enable pressurization and depressurization in the hermetic furnace, and to control the molten metal in the hermetic furnace to flow out There are things to do. Moreover, the dam between the main chamber and the sub chamber is for setting the initial hot water surface height in the airtight furnace to be constant. In order to allow the molten metal in the furnace to flow into the hermetic furnace, first, the U-shaped pipe is closed with a main chamber stopper, the pressure in the hermetic furnace is reduced, the molten metal in the furnace is sucked, and the molten metal is stored in the hermetic furnace. Next, the suction pipe is closed with the sub chamber stopper, the main chamber stopper is opened, and the molten metal is supplied into the U-shaped pipe by gravity. Further, when the sub chamber stopper is opened, the molten metal above the dam installed between the main chamber and the sub chamber flows out into the furnace through the suction pipe. Therefore, the hot water surface position of the hermetic furnace is the uppermost position of the dam. In addition, since the airtight furnace is located on the furnace, the molten metal surface position in the U-shaped pipe is very close to the molten metal introducing means. In order to introduce the molten metal into the molten metal introducing means, the molten metal is supplied to the molten metal introducing means by pressurizing the gas in the airtight furnace or driving the plunger portion of the main chamber stopper. When the molten metal is mechanically driven using the plunger portion, it is easy to control the amount of molten metal supplied, but the durability of the plunger may be a problem. Further, when the molten metal is driven by gas pressurization, there are few problems with durability, but it is not easy to control the amount of molten metal supplied. In any case, it is desirable to install a hot water level sensor in order to detect the hot water surface position in the hermetic furnace with the hot water level sensor and control the molten metal supply amount in consideration of the information.

  The dimensions of the hermetic furnace vary depending on the volume of the mold cavity, the casting cycle, the volume of the U-shaped pipe, etc., but the molten metal surface cross-sectional area is as large as possible, and the molten metal surface changes by several mm or less with one supply. It is desirable to do so. This is because the accuracy of the supply volume decreases as the molten metal surface level changes. Also, if the airtight chamber, especially the main chamber, is not large compared to the volume of the U-shaped pipe, the position of the molten metal after the first drawn molten metal flows into the U-shaped pipe will be lower than the height of the dam. Disappears. Furthermore, when the molten metal stays in the hermetic furnace for a long time, a heater for heating the molten metal in the hermetic furnace may be necessary.

  The suction pipe may be made of the same material as that of the U-shaped pipe, or may be made of another material as long as it has little reaction with the molten metal and is durable.

2. Casting method The casting method of the present invention is a casting method for producing a cast product by introducing a molten metal in a U-shaped pipe immersed in a furnace into a mold through a molten metal introducing means,
1) Installation process of U-shaped pipe in furnace and preparation process for flowing molten metal into said airtight furnace 2) First process of supplying molten metal to molten metal introducing means at a low pressure of 0.2 MPa or less 3) From molten metal introducing means The second step of introducing the molten metal into the mold 4) The third step of flowing the molten metal into the U-shaped pipe 5) The fourth step of taking out the solidified cast product, cleaning the mold, painting, etc., and closing the mold The first step to the fourth step are repeated until the hot water level in the U-shaped pipe is lowered beyond a certain limit.

  The method of the present invention can be applied to the various alloys and metals listed above.

Preparation Step The preparation step differs depending on whether the plunger described in 4 or 5 of “Means for Solving Problems” is used as the molten metal drive means and the airtight furnace described in 6 is used. When a plunger is used, the U-shaped pipe is immersed in the molten metal, and the plunger tip is positioned on the opening provided on the side surface of the U-shaped pipe. In this step, the molten metal is supplied to the furnace so that the surface of the molten metal in the pipe is positioned appropriately.

  When using the hermetic furnace as the molten metal driving means, first, the U-shaped pipe is closed with the main chamber stopper, the sub chamber stopper is opened, and the inside of the hermetic furnace is depressurized by exhausting from the decompression port of the hermetic furnace. Aspirate the molten metal into an airtight furnace. At this time, the molten metal is sucked up from above the dam, but if the airtight furnace is filled with molten metal, the molten metal is sucked into the decompression port or the like, which causes a problem. Next, the main chamber stopper is opened, and the molten metal in the airtight furnace is caused to flow into the U-shaped pipe. Thereby, although the molten metal surface position in an airtight furnace falls, it is designed so that it may become higher than the height of a dam. Furthermore, when the sub chamber stopper is opened, the molten metal overflowing from the dam into the sub chamber flows out into the furnace due to gravity, and the position of the hot water surface in the main chamber, and therefore the position of the hot water surface in the U-shaped pipe, is high. It becomes.

First step In this step, the molten metal is introduced into the molten metal introducing means at a low pressure of 0.2 MPa or less.

  When the plunger is used as the molten metal driving means, the plunger is pushed down by a driving device such as an electric servo motor or a hydraulic servo motor, and the molten metal in the U-shaped pipe is introduced into the molten metal introducing means at a low pressure of 0.2 MPa or less. Alternatively, the pressurized gas can be sent in front of the plunger to pressurize the molten metal.

  When the opening / closing member described in 2 of “Means for Solving Problems” is used as the molten metal introducing means, there are two methods in the first step. One is a method of introducing the molten metal by positioning the opening of the opening / closing member on the U-shaped pipe. In this case, the air or gas in the U-shaped pipe flows out into the mold cavity. Another method is to prevent the molten metal surface covered with the oxide film in the U-shaped pipe from being introduced into the mold, by placing a trap provided under the opening / closing member on the U-shaped pipe. In this method, molten metal is introduced. In this case, air or gas in the U-shaped pipe is discharged from an exhaust groove provided in the lower part of the opening / closing member or an exhaust groove provided in the upper part of the trap. When the airtightness is poor, air or gas flows out from the periphery of the opening / closing member and is not necessary. Further, when the molten metal flows into the trap, the opening / closing member is moved to remove the molten metal at this portion, the opening is moved to the upper part of the U-shaped pipe, and the molten metal in the U-shaped pipe is moved to the mold gap. The second step to be introduced is entered.

  When the airtight furnace is used as the molten metal driving means, the inside of the airtight furnace is pressurized by feeding gas from the pressure port, and the molten metal is supplied to the molten metal introducing means. The supply amount is calculated from the hot water surface position by the hot water surface position sensor and the amount supplied to the mold. When the accuracy of the molten metal supply amount by this gas pressurization is insufficient, the molten metal is supplied by driving the plunger portion of the main chamber stopper. The supply amount is obtained from the moving distance of the plunger and the cross-sectional area of the moving part.

  In these first steps, it is possible to suck the molten metal in the U-shaped pipe by depressurizing the molten metal introducing means and, if necessary, the mold, without using the molten metal pressurizing by the plunger or gas. Alternatively, the molten metal can be introduced by using the suction and the molten metal pressurization by a plunger or gas.

Second Step In this step, the molten metal is introduced from the molten metal introducing means into the mold.

  When the opening / closing member is used, the molten metal is introduced into the mold by plunger or gas pressurization with the opening positioned on the U-shaped pipe. The inside of the mold can be decompressed to suck the molten metal. In this case, the molten metal drive means acts as a molten metal introduction control device. That is, by decreasing the plunger moving speed or reducing the pressure in the airtight furnace, the molten metal can be gently introduced into the mold cavity even if the degree of decompression of the mold cavity is increased, and the oxide film and gas entrainment are reduced. The surroundings will be better. Moreover, when sending gas to the plunger tip, the molten metal introduction speed can be controlled by controlling the gas pressure with the plunger stopped and controlling the degree of pressure reduction in the mold cavity. In addition, after the mold cavity is filled with the molten metal in the second step, the molten metal is pressurized with a pressure piston installed on the mold before the third step or in parallel with the third step, if necessary. May be prevented.

  When the sleeve having the two plunger tips is used as the molten metal introducing means, the two plunger tips are simultaneously moved under the mold opening, and then one of the two die tips as in the conventional die casting method. With the plunger tip, the molten metal in the sleeve is injected into the mold cavity.

Third Step In this step, the plunger portion is pulled up or pressurization in the airtight furnace is stopped, and the molten metal is caused to flow into the U-shaped pipe from the opening of the U-shaped pipe. In the second step, when the molten metal is introduced using the reduced pressure of the mold, the airtightness is good. Therefore, by introducing outside air or inert gas into the U-shaped pipe, the molten metal in the U-shaped pipe is reduced. Make it easy. It is desirable to introduce an inert gas that has little reaction with the molten metal because it can prevent oxidation of the molten metal surface. As the inert gas, N ₂ gas is inexpensive for Al alloy molten metal, but other gases such as Ar gas may be used. When the gas is sent in front of the plunger and the molten metal is driven, the gas is collected on the air feeding side so that the gas does not flow out from the pipe opening. For this reason, it is desired to prevent the gas from flowing out from the pipe opening into the furnace with the plunger tip as a concave surface.

Fourth step: The solidified cast product is taken out, and the mold is closed by performing mold cleaning, coating, and the like. This process is the same as the conventional casting method.

The features of the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to the examples.
<Example 1>

  FIG. 1 shows a front view of a casting apparatus in Example 1, and FIG. 2 shows a side view. The U-shaped pipe 1 is immersed in the molten metal 5 and supported by a support member 12. A plunger 2 which is a part of the molten metal driving means is provided at one end, and an opening / closing member 6 as a molten metal introducing means is provided at the other end. The mold 8 is connected through. Near the plunger 2 is a pipe opening 3. In some cases, a plunger 2 having an opening as shown in FIG. 3 may be used. In this case, the pipe opening 3 is not necessarily provided in the U-shaped pipe 1. The molten metal flows into the U-shaped pipe 1 from these openings and fills the U-shaped pipe 1. In the first embodiment shown in FIG. 1, the shape of the opening 3 is a slit having a width of 10 mm that spreads in the horizontal direction, but may be other shapes such as a circle or a plurality of shapes. A filter may be installed in the opening 3. If the position of the opening 3 is too close to the surface of the molten metal, an oxide film or the like is involved, and it is necessary to frequently supply the molten metal to the furnace 4. To do. When the plunger 2 is moved downward and the pipe opening 3 is closed, thereafter, the volume multiplied by the movement distance of the plunger 2 and the cross-sectional area of the U-shaped pipe 1 is transported upward from the initial hot water surface position. Is done. Therefore, it is necessary to set the movement distance of the plunger 2 so that this volume becomes larger than the total volume of the mold gap 10 and the volume from the initial molten metal surface position to the mold gap. Since the molten metal surface position decreases with each casting, it is desirable to detect the molten metal surface position with a sensor and determine the amount of movement of the plunger 2 based on that information. Alternatively, when the pressure rises when the molten metal introducing means is filled with molten metal, it is possible to measure the force acting on the plunger 2 and control the movement of the plunger 2 from the change. Thereafter, at an appropriate time, the plunger 2 is pulled up above the pipe opening 3. Then, again, the U-shaped pipe 1 is filled with the molten metal 5. By repeating this operation, casting can be repeated.

  In this apparatus, casting can be performed by reducing the pressure of the mold cavity 10 and controlling the suction force and the molten metal pressurization by the plunger 2. In this case, gas is entrained unless the airtightness between the opening / closing member 6 and the U-shaped pipe 1 and the mold 8 is improved. As the molten metal flow resistance in the gap between the plunger 2 and the U-shaped pipe is larger, the molten metal inflow rate into the mold cavity 10 is increased even if the degree of decompression of the mold cavity 10 is increased. Therefore, the molten metal can be introduced quietly, so that oxidation on the surface of the molten metal can be prevented, the surroundings of the molten metal can be prevented, and the entrapment of the gasified coating agent can be prevented, and a high-quality cast product can be obtained. In addition, by putting the mold in a vacuum box, it can be used for a ceramic shell mold and a sand mold.

  The plunger 2 is driven by an electric servo motor, but may be other means such as a hydraulic servo motor or a linear motor. In addition, other methods such as a ball screw other gear may be used to change the rotational motion into a linear motion.

  The shape of the U-shaped pipe 1 is not limited to the shape of the present embodiment, for example, if the mold 5 and the plunger 2 are at the top, and a considerable portion of the pipe connecting between them is immersed in the molten metal. The shape may be rectangular or triangular. The cross-sectional shape is circular, but other shapes may be used. Also, the inner diameters need not be the same. However, in this embodiment, the inner diameter of the plunger 2 is larger than that of the lower pipe portion of the opening / closing member 6 so that the molten metal can quickly flow into the mold cavity 10 by the movement of the short plunger 2. The difference between the outer diameter of the plunger 2 and the inner diameter of the U-shaped pipe (plunger gap dimension) is set to about 0.01 to 0.5 mm. As the plunger gap size is smaller, a larger molten metal pressure is obtained, but durability is a problem. Above the pipe opening 3, even if the gap is large, it does not affect the molten metal supply, and the narrower the gap, the more difficult the durability is due to sliding. There is no. If the friction between the plunger 2 and the U-shaped pipe 1 is large and there is a problem in durability, all or part of the plunger is porous, or a slit is provided in part, and an inert gas is ejected. The frictional resistance may be reduced. Since the length of the U-shaped pipe 1 is short and the position of the hot water surface is preferably close to the opening / closing member 6, the furnace bottom where the U-shaped pipe 1 is installed is raised. It may be horizontal. Moreover, when the fall of molten metal temperature becomes a problem, you may insert a heater in a furnace.

  In the present embodiment, the trap 13 of the opening / closing member 6 is positioned above the U-shaped pipe 1, and the molten metal covered with the oxide film is removed to introduce the molten metal into the mold. In order to allow the molten metal to flow into the trap 13, it is necessary to cause the gas in the U-shaped pipe 1 to flow out. In this embodiment, the molten metal flows out from the gap around the opening / closing member 6. Moreover, it is pushed into the trap 13 by the molten metal pressure. However, when airtightness around the opening / closing member is important, such as when the inside of the mold is decompressed, it is necessary to devise exhaust such as a structure as shown in FIG. 4 or an exhaust groove provided below the opening / closing member 6. .

  In FIG. 4, when the gate valve 17 is opened, the gas in the U-shaped pipe 1 flows out through the exhaust groove 16. In some cases, the pressure may be reduced from the exhaust groove 16. When the molten metal flows into the trap 13 to some extent, the gate valve 17 is closed. The closing timing may be determined empirically, or may be controlled by installing a temperature sensor, a hot water surface sensor, or the like in or near the trap 13. Alternatively, the gate valve 17 may not be used, and the driving may be stopped when the molten metal flows into the trap 13. However, in this case, there is a risk that the molten metal flows into the exhaust structure 16 and is difficult to remove. Further, instead of providing the gate valve 17, the upper portion of the trap 13 may be made of a porous material.

<Example 2>
FIG. 5 is a cross-sectional view of the plunger 2 and the upper part of the U-shaped pipe 1 used in the second embodiment. In this case, the plunger 2 has a plunger cavity 18 with the plunger tip open, and after closing the pipe opening 3 with the plunger 2, the inert gas is sent from the molten metal pressurized gas inlet 19 to form a U-shape. The molten metal in the pipe 1 is pressurized and the molten metal is introduced into the molten metal introducing means. When the introduction of the molten metal into the mold is completed, the gas is discharged and recovered. Although it is good also as a solid plunger instead of such a hollow plunger, there exists a fault which gas tends to flow out from the pipe opening part 3. FIG. Further, it has a pressurized gas introduction port 20 and a gas outflow groove 22 for ejecting gas in the gap between the plunger 2 and the U-shaped pipe 1 to reduce friction between the plunger 2 and the U-shaped pipe 1, After the casting, the molten metal can be prevented from leaving in this gap. As the gas, various inert gases as described above can be used. In addition, for gas outflow, all or part of the plunger may be made porous, or pores or slits may be provided. However, it is desirable to independently control the gas for pressurizing the molten metal and the gas introduction pressure into the plunger gap. In addition, as shown in FIG. 6, instead of introducing pressurized gas from the molten metal pressurized gas inlet, a molten metal pressurized gas pipe 21 provided in the U-shaped pipe 1 may be used.

<Example 3>
FIG. 7 shows the molten metal introduction means used in Example 3. That is, the sleeve 23 is connected to one end of the U-shaped pipe 1 through the sleeve opening 26. Plunger tips 24 and 25 are provided in the sleeve 23, and plunger drive shafts 27 and 27 'are connected thereto, respectively. The molten metal in the U-shaped pipe 1 moves the sub-plunger tip 25 or the main plunger tip 24 to create a decompression space by expanding the space, and the molten metal 5 is moved into the sleeve 23 by the molten metal driving means at the other end. To introduce. After the molten metal is introduced, both plunger tips 24 and 25 are moved simultaneously, positioned below the opening 28 to the mold, and the main plunger chip 24 is moved to supply the molten metal to the mold. As a molten metal drive means, plunger drive like Example 1 may be utilized and an airtight furnace like Example 4 mentioned later may be utilized.

<Example 4>
FIG. 8 shows an embodiment in which an airtight furnace 30 using pressurization, decompression or plunger drive is used as the molten metal drive means. The U-shaped pipe 1 is the same as that described in Example 1, and is immersed in the furnace 4 and supported by the support member 12. The airtight furnace 30 covers a part of the upper part of the furnace 4 to prevent heat dissipation and also prevent heat dissipation from the lower part of the airtight furnace 30. The airtight furnace 30 includes a main chamber 31 and a sub chamber 32 and is partitioned by a dam 33. However, the main chamber 31 and the sub chamber 32 are integrated in the upper part of the dam 33, and are not separated completely. The pressurizing port 39 for pressurizing the whole airtight furnace 30 and the depressurized pressure for depressurizing. It has a mouth 40. A pressurizing source such as a cylinder or a compressor is connected to the pressurizing port 39, and a vacuum pump or the like is connected to the depressurizing port 40 via an electromagnetic valve or the like. Further, a U-shaped pipe 1 is connected to the main chamber 31, a suction pipe 34 is connected to the sub chamber 32, a main chamber stopper 35 is installed in the main chamber 31, and a sub chamber stopper 38 is installed in the sub chamber 32. The chamber stopper 35 includes a seal portion 36 and a plunger portion 37, and both have a structure that can be driven independently. However, when it is not necessary to drive the molten metal with the plunger, a stopper having only a sealing function may be used.

  The suction pipe 34 is installed in a deep part of the furnace 4 and a heater 42 is installed in the vicinity of the furnace bottom 41. However, the heater 41 may be installed as necessary, for example, when a drop in hot water temperature becomes a problem. , Not always necessary. Also, the shape of the furnace need not be as shown in FIG. However, in the case of such a shape, the dimension of the U-shaped pipe 1 or the dimension of the support member 12 can be reduced. In addition, by installing the heater 42 near the furnace bottom 41, the molten metal whose density is reduced by heating rises and circulates, and the molten metal temperature in the furnace 4 is kept uniform, but it is not necessarily installed near the furnace bottom 41. It is not necessary. The end of the suction pipe 34 is preferably located at a position slightly away from the furnace bottom 41. This is because, depending on the molten metal, the concentration of harmful substances such as non-metallic inclusions and intermetallic compounds having a high density is increased near the furnace bottom 41, so that supply of such molten metal is prevented.

  In the present embodiment, the molten metal is supplied by first closing the U-shaped pipe 1 with the main chamber stopper 35, opening the sub chamber stopper 38, depressurizing the entire airtight furnace 30 through the decompression port 40, and Then, the molten metal in the furnace 4 is sucked into the main chamber 31 and the sub chamber 32, and the sub chamber stopper 38 is closed. At this time, the molten metal is sucked gently so as not to flow into the decompression port 40 or the like. For this reason, it is desired to measure and control the position of the hot water surface in the airtight furnace 30 with a hot water surface sensor or the like. When the molten metal is sucked into the airtight furnace 30, the main chamber stopper 35 is opened, and the molten metal is caused to flow into the U-shaped pipe 1 by gravity. Next, the sub chamber stopper 38 is opened, and the molten metal existing in the sub chamber 32 is caused to flow out into the furnace 4 by gravity. Further, the sub chamber stopper 38 is closed again. Now that the preparation for supplying the molten metal to the molten metal introducing means 29 is completed, the pressurized gas is introduced from the pressure port 40 to pressurize the airtight furnace 30, and the molten metal is supplied to the molten metal introducing means 29. However, the relationship between the applied pressure and the molten metal volume to be supplied is more complicated than when the plunger is used, and complete airtightness is difficult, so the control is not easy and the control accuracy of the molten metal supply amount is not very good. However, there are few problems regarding the durability of the sliding portion such as the plunger. That is, when high molten metal supply accuracy is required or when airtightness is a problem, the plunger portion 37 of the main chamber stopper 35 is driven to supply the molten metal. The method in this case is the same as that in the first embodiment.

<Example 5>
FIG. 9 shows the process of the fifth embodiment. (A) shows the time when the preparation process is completed or the time when the fourth process is completed. The plunger 2 is located on the pipe opening 3, and the molten metal surface in the U-shaped pipe 1 is the furnace 4. It is the same height as the hot water inside. From this state, the plunger 2 is pushed down and the molten metal is introduced into the trap 13 provided in the opening / closing member 6 (first step (b)). The gas in the U-shaped pipe 1 is exhausted through the exhaust groove 18. When the molten metal flows into the trap 13, the opening / closing member 6 is moved, the opening 7 is moved onto the U-shaped pipe 1, and the molten metal is introduced into the mold cavity 10 (second step (c)). Thereby, the dirty hot water surface in the U-shaped pipe 1 is removed at the same time. When the mold cavity 10 is filled with the molten metal, the opening / closing member 6 is moved again, the mold cavity 10 is closed, and the molten metal is pressurized with a pressure piston. At the same time, the plunger 2 is pulled up to lower the molten metal level in the U-shaped pipe 1 (third step (d)). Further, the solidified material 40 remaining in the trap 13 and the opening 7 is removed, the mold is opened, the casting is taken out, the mold gap is cleaned, and the mold is prepared for the next casting.

In this embodiment, the plunger 2 may be moved while the mold cavity 10 is decompressed. In this case, as the moving speed of the plunger 2 is slower, the degree of pressure reduction in the mold cavity 10 can be increased, and oxidation of the molten metal surface and gas entrainment in the mold cavity 10 are reduced, and a high quality casting can be obtained. However, if the airtightness of the connection part and the contact surface between the opening / closing member 6 and the mold 8 or the U-shaped pipe 1 is not improved, the surrounding air is sucked and entrained. . In addition, when the airtightness is improved, an external air introduction groove for introducing external air into the U-shaped pipe 1 is provided in the third step when the molten metal surface is lowered.

Claims (13)

A casting apparatus for producing a cast product by injecting a molten or semi-molten metal or alloy (hereinafter referred to as “molten metal”) into a mold from a furnace, and 1) a mold having a molten metal introduction means for introducing molten metal. ,
2) a molten metal driving means for introducing the molten metal into the molten metal introducing means at a pressure of 0.2 MPa or less; and 3) one end connected to the molten metal introducing means, the other end connected to the molten metal driving means, and the inside of the furnace U-shaped pipe immersed in molten metal,
A casting apparatus characterized by having The molten metal introducing means is installed between the U-shaped pipe and the mold, 1) an opening, and 2) a cavity provided on the U-shaped pipe side to remove a part of the molten metal. 3) For opening and closing a U-shaped pipe having an exhaust groove for exhausting gas or air in the trap and the U-shaped pipe on the U-shaped pipe side or the upper part of the trap. The casting apparatus according to claim 1, which is a member. The molten metal introducing means is a cylindrical sleeve, and is opened from a state in which 1) an opening to the mold, 2) an opening to the U-shaped pipe, 3) an opening to the U-shaped pipe is closed. Thus, two plunger tips that can be driven independently to create a decompression space in the sleeve, and after the melt flows into the decompression space, move the melt further into the opening to the mold and inject, The casting apparatus according to claim 1, wherein The molten metal driving means includes 1) a plunger provided in the U-shaped pipe, 2) a driving device for driving the plunger, 3) an opening provided on a side surface of the U-shaped pipe near the plunger, 4) U The casting apparatus according to claim 1, wherein the apparatus has a gas introduction groove and a pressurizing means for introducing a pressurized gas into a gap between the letter-shaped pipe and the plunger. The casting apparatus according to claim 1, wherein in addition to the molten metal drive means according to claim 4, the plunger has a molten metal pressure groove and a pressure means for introducing gas in front of the plunger. The melt driving means according to claim 1 is an airtight furnace capable of pressurization and decompression,
1) Arranged to cover a part of the furnace so as to prevent heat dissipation from the furnace,
2) having a pressurizing port and a depressurizing port for connecting to the pressurizing unit and the depressurizing unit;
3) Consists of a main room and sub-chamber separated by a dam at the bottom,
4) The U-shaped pipe is connected to the main chamber, and the volume of the main chamber is larger than that of the sub chamber,
5) A suction pipe for sucking molten metal in the furnace is connected to the sub chamber,
6) The casting apparatus according to claim 1, wherein the main chamber has a main chamber stopper for opening and closing the U-shaped pipe and a sub chamber stopper for opening and closing the suction pipe in the sub chamber. The main chamber stopper according to claim 6 has a seal portion that can open and close the U-shaped pipe on the outside, and a plunger portion that can pressurize the molten metal in the U-shaped pipe on the inside, and the seal portion and the plunger portion. The casting apparatus according to claim 1, wherein the casting apparatus can be driven independently. A casting method for producing a cast product by introducing a molten metal in a furnace into a mold through a molten metal introducing means,
1) Preparatory step of immersing the U-shaped pipe in the furnace and flowing the molten metal into the hermetic furnace according to claim 6 2) First step of supplying the molten metal to the molten metal introducing means at a low pressure of 0.2 MPa or less 3) Second step of introducing the molten metal into the mold from the molten metal introducing means 4) Third step of introducing the molten metal into the U-shaped pipe 5) Taking out the solidified casting, cleaning the mold, coating the mold, etc. The fourth step of closing
The casting method is characterized in that the first step to the fourth step are repeated until the hot water level in the U-shaped pipe is lowered to a certain limit or more. Using the plunger according to claim 4 or 5 as the molten metal drive means according to claim 8, and using the opening and closing member according to claim 2 as the molten metal introducing means, in the first step, A trap, which is a cavity provided below the opening / closing member, is positioned on the U-shaped pipe, and the molten metal in the trap is moved by moving the opening / closing member when the molten metal flows into the trap. The casting method according to claim 8, wherein the casting is removed, and at the same time, the opening of the opening / closing member is positioned on the U-shaped pipe and the process proceeds to the second step. The molten metal is introduced into the mold while reducing the pressure in the mold and adjusting the speed at which the plunger is pushed down in the first and second processes, or the second process. Casting method A casting method using the sleeve and plunger tip according to claim 3 as the molten metal introducing means according to claim 8. The molten metal driving means according to claim 8, the airtight furnace according to claim 6, wherein the preparing step includes closing the U-shaped pipe with the main chamber stopper or a seal portion of the main chamber stopper, and Open the stopper, depressurize the hermetic furnace and suck the molten metal in the main furnace into the hermetic furnace, then open the main chamber stopper, let the molten metal in the hermetic furnace flow out into the U-shaped pipe, And the molten metal overflowing from the dam and returning to the main chamber is returned to the main furnace, and the molten metal is melted at a pressure of 0.2 MPa or less by pressurizing the airtight furnace or driving the plunger portion of the main chamber stopper. A first step of supplying to the introducing means, a step of introducing the molten metal into the mold by the molten metal introducing means using the opening / closing member according to claim 2 or the sleeve and the plunger tip according to claim 3, a second step; Stop pressurization , Or a method of casting according to claim 8, opening the seal of the U-shaped pipe, and the third step a step of flowing molten metal into the U-shaped pipe The molten metal introducing means according to claim 12 is used as the opening / closing member according to claim 2, and at least in the second step, the inside of the mold is decompressed and the airtight chamber is decompressed to adjust the degree of decompression in the mold. The casting method according to claim 8, wherein the molten metal is introduced while being introduced.

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