JPH11221659A - Low pressure casting method and casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low pressure casting method which does not generate a defective product and any trouble in the casting by executing pouring stop at good timing according to the thickness even in the case of being the product having uneven thickness. SOLUTION: In the low pressure casting method which fills up molten metal in a molten metal chamber 16 into the cavity 29 in a metallic mold through molten metal filling passages 30a by pressurizing after storing the molten metal from a molten metal holding furnace 1 into the molten metal chamber 16 arranged between the molten metal holding furnace 1 and the cavity 29 by pressurizing, after filling up the molten metal in the molten metal chamber 16 into the cavity 29 in the metallic mold from the molten metal chamber 16 through plural molten metal filling passages 30a inserted into the molten metal chamber 16 at the lower end parts and before the molten metal at the upper parts of the molten metal filling passages 30a solidifies, inert gas is supplied into the upper parts of the molten metal filling passages 30a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-pressure casting method and a casting apparatus for filling a molten metal into a cavity of a casting mold by pressure.

[0002]

2. Description of the Related Art In a conventional low-pressure casting apparatus, a molten metal holding furnace for holding a molten metal in a molten state is provided, a casting mold is disposed above the molten metal holding furnace, and a lower end portion is located inside the molten metal holding furnace. Is known, in which a stalk inserted into a molten metal is provided, and the upper end of the stalk is communicated with one molten metal filling path (gate) of a cavity of a casting mold. In this low-pressure casting apparatus, by applying pressure to the molten metal surface in the molten metal holding furnace to raise the molten metal in the molten metal holding furnace through the stalk and filling the cavity, the molten metal in the cavity is solidified. The molten metal in the stalk is returned to the molten metal holding furnace by releasing the pressure applied to the molten metal surface of the molten metal holding furnace, and the molten metal is filled in the molten metal filling path.

However, since the cavity is filled with the molten metal from one molten metal filling path, the solidification of the thick part of the product is slow. If the solidification of the molten metal filling path is fast, shrinkage cavities and the like are formed on the product solidified in the cavity. May occur. In addition, since there is only one molten metal filling path, it is difficult to take a timing between solidification of the thick part of the product and solidification of the molten metal filling path,
There is a risk that defects such as shrinkage cavities may occur, or unsolidified portions may occur if the hot water is drained quickly.

As a conventional low-pressure casting apparatus for preventing such defective products from occurring, for example, as shown in FIG.
The casting mold 70 is arranged above a molten metal holding furnace (not shown),
There is known a method in which a molten metal in a molten metal holding furnace is filled into a casting mold 70 with a pressing force (Japanese Patent Laid-Open No. 58-11697).
No. 3).

[0005] The casting mold 70 comprises an upper mold 71 and a lower mold 7.
2 and a cavity 73 is formed between the molds 71 and 72. In addition, the lower mold 72 has a lower portion which is connected to a molten metal holding furnace (not shown) via a stalk through a molten metal guide path 7.
4 and a plurality of molten metal filling paths 7 branching from the upper end of the molten metal guiding path 74 and communicating with the cavity 73.
5 are provided. In the figure, 76 is a mold 71 at both ends.
Core held between 72.

In this casting apparatus, after the molten metal in the molten metal holding furnace is raised to the inside of the stalk to the molten metal guide path 74 by applying pressure to the molten metal surface of the molten metal holding furnace (not shown),
The molten metal is supplied to the cavity 7 through a plurality of molten metal charging paths 75.
3 is filled quickly. In this casting apparatus as well, after the molten metal filled in the cavity 73 is solidified, the pressing force applied to the molten metal surface of the molten metal holding furnace is released, so that the plurality of molten metal charging paths 75, the molten metal guiding paths 74,
The molten metal in the stalk is returned to the molten metal holding furnace by its own weight. At this time, the molten metal filling paths 75 are drained at the same timing. Thereafter, by opening the molds 71 and 72 after the molten metal in the cavity 73 is completely solidified, the product formed between the molds 71 and 72 can be taken out.

[0007]

However, FIG.
In the conventional casting apparatus shown in (1), when the molten metal in the cavity is solidified to some extent, the molten metal in the molten metal filling path and the stalk is returned to the molten metal holding furnace by its own weight,
It has not been possible to quickly drain the plurality of molten metal filling paths 75.

In addition, when the thickness of one product varies greatly depending on the location, that is, when the volume in the cavity 73 varies greatly depending on the location, the solidification speed of the molten metal is slower in the large volume portion and faster in the small volume portion. For this reason, in the configuration in which the plurality of molten metal filling paths 75 are drained at the same timing as shown in FIG. 10, when the timing of draining is early, the molten metal is completely removed in a portion where the volume of the cavity 73 is large. A part of the unsolidified molten metal without solidification may be returned to the molten metal holding furnace when the molten metal is drained, and a cavity may be formed in the product. Further, when the timing of draining the metal is late, the molten metal in the molten metal filling path 75 corresponding to the portion where the volume of the cavity 73 is small may be solidified, which may hinder the next casting.

Accordingly, a first object of the present invention is to provide a low-pressure casting method in which a plurality of molten metal filling paths are installed at locations where shrinkage cavities are likely to occur, and a product with few defective products can be manufactured.

Further, a second object of the present invention is that even when the thickness of a product is not uniform, the timing of hot water draining is properly performed in accordance with the thickness of the product, so that defective products are generated or casting is hindered. An object of the present invention is to provide a casting device that does not come.

[0011]

In order to achieve the first object, according to the present invention, a molten metal chamber provided between a molten metal holding furnace and a mold cavity is pressurized by the molten metal holding furnace from the molten metal holding furnace. After the molten metal is stored, in a low-pressure casting method in which the molten metal in the molten metal chamber is filled into the cavity through a molten metal filling path by pressurization, the molten metal in the molten metal chamber is removed from the molten metal chamber into the mold. After filling the cavity with the lower end through the plurality of molten metal filling paths inserted into the molten metal chamber, before the molten metal in the upper part of the molten metal filling path solidifies, an inert gas is supplied to the upper part of the molten metal filling path. It is a low pressure casting method.

According to another aspect of the present invention, there is provided a molten metal holding furnace, a molten metal chamber disposed above the molten metal holding furnace, and a lower end portion of the molten metal of the molten metal holding furnace. A molten metal guide path inserted into the molten metal chamber and guiding the molten metal into the molten metal chamber; molten metal supply means for supplying the molten metal of the molten metal holding furnace into the molten metal chamber via the molten metal guiding path; and an upper part of the molten metal chamber Gas supply means for supplying gas to the melt chamber, a mold cavity disposed above the melt chamber, and a lower end inserted into the melt chamber,
And a plurality of molten metal filling paths for guiding the molten metal in the molten metal chamber to the mold cavity, and a depth from a position of a molten metal surface of the molten metal chamber to a position of a lower end portion of the opening of the molten metal charging path. The casting apparatus has the molten metal filling path arranged in various ways, and has a molten metal filling means for supplying the molten metal in the molten metal chamber to the mold cavity via the molten metal filling path. .

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

<Mechanical Structure of Molten Casting Side> In FIG. 1, 1 is a molten metal holding furnace, 1a is a bottom wall of the molten metal holding furnace 1, 1b
Is a heater arranged at the upper part of the molten metal holding furnace 1, 2 is a molten metal of aluminum, aluminum alloy, magnesium alloy or the like in the molten metal holding furnace 1, and 3 is an upper opening end of the molten metal holding furnace 1 closed. The cover 4 is a partition provided in the molten metal holding furnace 1.

In FIG. 1, the inside of the molten metal holding furnace 1 is divided by a partition wall 4 into a molten metal supply chamber (a molten metal injection chamber) 5 on the right side and a molten metal supply chamber 6 on the left side.
It is divided into and. Moreover, a communication port 1c is provided between the upper end of the partition 4 and the lid 3, and between the partition 4 and the bottom wall 1a of the molten metal holding furnace 1, the molten metal supply chamber 5, the molten metal supply chamber 6, The communication port 7 is formed to communicate with.

Reference numeral 8 denotes a degassing device (gas release device) inserted through the lid 3 into the molten metal supply chamber 5, and 9 denotes a molten metal supply provided on the molten metal supply chamber 5 and provided on the lid 3. Mouth, 10
Is a lid for closing the molten metal supply port 9, and 11 is a connection port communicating with the upper space 6a of the molten metal supply chamber 6. The degassing device 8 discharges a gas (mainly hydrogen or the like) in the molten metal 2 injected from the molten metal supply port 9 to the outside (a known structure is adopted in this configuration). .

A mold support plate 12 is provided above the molten metal holding furnace 1, and a mold support 13 is fixed above the plate 12. A container-shaped heat insulating material 13a which is opened upward is fixed, and a cast iron molten metal container 14 which is opened upward is fixed in the heat insulating material 13a.
Are arranged. The surface of the molten metal container 14 is covered with ceramic wool or the like (not shown), and the molten metal 2 ′
And do not react chemically. 12a is an insertion hole provided in the plate 12. Moreover, the molten metal container 14 is formed in a tapered shape such that the bottom wall 14a is lowered downward toward the center.

At the center of the bottom wall 14a, a cylindrical stalk (melt guide pipe) 1 made of ceramic or the like is placed.
The upper end of 5 is fixed. The stalk 15 extends downward through the insertion hole 12 a and penetrates the lid 3 and is inserted into the molten metal 2 in the molten metal supply chamber 6. 15a
Is a molten metal guide path in the Stoke 15.

When the bottom wall 14a of the molten metal container 14 is formed in a tapered shape, when the molten metal 2 'in the molten metal container 14 is pushed down to the molten metal holding furnace 1 side, the molten metal 2 'Can be pushed down without remaining. A molten metal chamber 16 for the molten metal 2 ′ is formed in the molten metal container 14, and a connection port 17 communicating with an upper space 16 a of the molten metal chamber 16 is formed above the molten metal container 14.

On the mold support 13 and the molten metal container 14, the molten metal container 14 is fixed at the upper end of the mold support 13.
A lower mold mounting plate 19 for closing the upper end of the molten metal chamber is provided, and a molten metal level detection sensor 23 projecting into the upper space 16 a of the molten metal chamber 16 is fixed to the lower mold mounting plate 19.

On the lower mold mounting plate 19, a casting mold 25 is provided.
Are arranged. This casting mold 25 is used for the lower mold mounting plate 1.
9 has an upper mold 27 fixed on the lower mold 26 and an upper mold 27 arranged on the lower mold 26. This upper mold 27 is used for supporting member 2.
8 and is fixed to the lower surface (inner surface) of the upper die mounting plate 21. A product-shaped cavity 29 is formed between the dies 26 and 27. The cavity 29 has left and right small volume portions 29a and 29b with small volumes and a large volume portion 29c with a large volume at the center.

Further, molten metal filling pipes 30a, 30b extending vertically and having upper ends communicating with small volume portions 29a, 29b of the cavity 29 are fixed to the lower mold 26, and extend vertically and have upper ends. A molten metal filling pipe 30c communicating with the large volume portion 29c of the cavity 29 is fixed.

The molten metal filling pipes 30 a to 30 c penetrate the lower mold mounting plate 19 and protrude into the molten metal chamber 16. The projecting positions of the molten metal filling pipes 30a and 30b on both sides in the molten metal chamber 16 are set at the central molten metal filling pipe 30.
c is higher than the protruding position into the molten metal chamber 16. 30a ', 30b' and 30c 'are the molten metal filling pipes 3
These are the molten metal filling paths in 0a, 30b, and 30c. The outer peripheral surfaces of the molten metal filling pipes 30a to 30c and the lower mold mounting plate 1
The lower surface of 9 is covered with a protective layer 19a made of cast iron, and the surface of this protective layer 19a is covered with ceramic wool or the like (not shown). The ceramic wool has a heat insulating function that prevents the protective layer 19a from chemically reacting with the molten metal and makes it difficult for the heat in the molten metal chamber 16 to be transmitted to the casting mold 25.

<Molten metal pressurizing system> The molten metal holding furnace 1 is provided with a connection port 11 communicating with the upper space 6a of the molten metal supply chamber 6, and the molten metal chamber 16 is provided with a connection port 17 communicating with the upper space 16a. ing.

A pipe 32 for supplying a gas such as an inert gas or compressor air is connected to the connection port 11, and an exhaust valve (a three-way electromagnetic switching valve) 33 is connected to the pipe 32.
The first port 33a of the exhaust valve 33 is connected to the second port 33a.
The discharge side of a gas supply (for gas supply) pressure control valve 34 is connected to the port 33b, and a gas supply source (gas supply source) 35 such as an inert gas or compressor air is provided on the inflow side of the pressure control valve 34. It is connected. In this embodiment, the third port 33c of the exhaust valve 33 is open to the atmosphere. However, by connecting the third port 33c to a gas (gas) recovery device,
The inert gas discharged from the port 33c may be reused.

A pipe 17a for supplying inert gas (for supplying gas) is connected to the connection port 17, and a first port 36a of an exhaust valve (three-way electromagnetic switching valve) 36 is connected to the pipe 17a. The second port 36b of the exhaust valve 36
Is connected to a discharge side of a pressure control valve 37 for supplying an inert gas (for supplying a gas), and an inflow side of the pressure control valve 37 is connected to an inert gas supply source (a gas supply source).
38 are connected. In this embodiment, the exhaust valve 36
The third port 36c is open to the atmosphere. However, the third port 36c may be connected to a gas recovery device to reuse the inert gas discharged from the third port 36c.

The pressure sensors 39, 40 are attached to the pipes 32, 17a. The gas supply source 3
5 is filled with an inert gas such as argon gas or nitrogen gas or a gas such as compressor air, and an inert gas supply source (gas supply source) 38 contains an inert gas (gas) such as argon gas or nitrogen gas. Is filled. The pressure signals from the pressure sensors 39 and 40 are input to an arithmetic control circuit (control means) 41, and the arithmetic control circuit 41
The operation of the pressure control valve 36 and the pressure control valves 34 and 37 is controlled.

<Operation> Next, a casting process involving a control operation by the arithmetic and control circuit 41 having such a configuration will be described with reference to FIGS. 2 and 3 schematically show the entire casting process. Therefore, the minimum reference numerals required for the description among the reference numerals shown in FIG. 4 to 9.

In FIG. 2, (a) shows the pressure in the upper space 16a of the molten metal chamber 16 (the pressure inside the molten metal chamber).
(b) shows the pressure in the upper space 6a of the molten metal holding furnace 1 (pressure inside the molten metal holding furnace).

The pressure characteristic curve 50 in (a) shows that the molten metal 2 is pushed up to a predetermined height in the molten metal chamber 16 and the molten metal surface S 1 of the molten metal 2 ′ in the molten metal chamber 16 is detected by the molten metal level detecting sensor 23. At the time of detection,
When the pressure in the upper space 16a in the melt chamber 16 is made equal to the atmospheric pressure, the pressure in the upper space 16a is set to "0".
It is illustrated as The pressure characteristic curve 52 of FIG.
When the pressure is not applied to the molten metal surface S2 in the molten metal supply chamber 6, that is, when the pressure in the upper space 6a of the molten metal supply chamber 6 is set to the atmospheric pressure, the pressure in the upper space 6a is set to "0". It is illustrated as

(I) Start t1 in FIG. 2 corresponds to the start in (1) in FIG. 3, that is, the start of casting. In this start position, the molten metal supply chamber 6
Is "0" as shown in FIG. 2 (b). In this state, by the end of the previous casting process,
Melt guide path 15a, melt chamber 16, melt filling path 30
a and the like are filled with an inert gas. In the drawing, the inert gas is represented by a set of small points.

Then, the arithmetic and control circuit 41 controls the casting mold 2
At time t1 before the mold clamping of No. 5, the ports 36a and 36b of the exhaust valve 36 are communicated, and the pressure control valve 37 is operated so that the inert gas from the inert gas supply source 38 is melted through the pipe 17a. The supply into the chamber 16 is started.

(Ii) Mold clamping The arithmetic control circuit 41 controls the operation of the hydraulic circuit 31 at the same time as the start of the supply of the inert gas to operate the hydraulic cylinder (not shown), and moves the upper mold mounting plate 21 to the position shown in FIG. Then, as shown in FIG. 3 (2) and FIG. 5, the upper mold 27 is brought into contact with the lower mold 26, and the mold is clamped.
This mold clamping is completed at time t2.

At this point, the inert gas supply source 38
Is supplied into the melt chamber 16 through the pipe 17a, so that the inert gas is supplied (filled) into the cavity 29 of the casting mold 25 through the melt filling path 30a. Leaks from the gap between the mating portions of the molds 26 and 27.

(Iii) Melt rise Further, the arithmetic and control circuit 41 stops the operation of the pressure control valve 37 at the time t2 immediately after the closing of the casting mold 25 and stops the supply of the inert gas to the melt chamber 16. Let it.

On the other hand, the arithmetic and control circuit 41 connects the ports 33a and 33b of the exhaust valve 33 at time t2,
By operating the pressure control valve 34, a gas such as an inert gas or a compressor air from the gas supply source 35 is pressurized and supplied to the upper space 6a of the molten metal supply chamber 6 through the exhaust valve 33 and the pipe 32. The pressure in 6a is P
Increase to 1. As the pressure in the upper space 6a rises, the molten metal 2 in the molten metal supply chamber 6 becomes molten metal guide path 15a.
Through the molten metal chamber 16.

As the molten metal 2 is pushed up, the molten metal surface S1 in the molten metal chamber 16 is moved for a time t as shown in FIGS.
It rises by three. In this state, the molten metal filling pipes 30a-
The lower end of 30 c is inserted into the molten metal 2 ′ in the molten metal chamber 16.

(Iv) Filling of the molten metal At this time, the arithmetic and control circuit 41 further controls the operation of the pressure control valve 34 and the gas supply source 35 at the time t3, so that the inert gas or the compressor air or the like from the gas supply source 35 is supplied. The gas is further pressurized and supplied to the upper space 6a of the molten metal supply chamber 6 through the exhaust valve 33 and the pipe 32 to increase the pressure in the upper space 6a to P2. This upper space 6
a, the molten metal 2 in the molten metal supply chamber 6
Is further pushed up into the melt chamber 16 via the melt guide path 15a.

On the other hand, the arithmetic and control circuit 41 includes the upper space 6a
As the internal pressure increases, the pressure control valve 37 and the inert gas supply source 38 are operated and controlled based on the detection signal from the molten metal level detection sensor 23, and the inert gas from the inert gas supply source 38 is supplied to the pipe 17a. Through the melt chamber 1
6, the pressure in the upper space 16a of the molten metal chamber 16 is increased to P2 'so that the molten metal level S1 is maintained at the height detected by the molten metal level detection sensor 23.

With such an operation control, the molten metal chamber 1
The molten metal in the molten metal chamber 16 is filled into the cavity 29 through the molten metal filling pipes 30 a to 30 c while the molten metal in the molten metal holding furnace 1 is refilled into the molten metal 6. The filling of the molten metal starts at time t3 and ends at t4.

(Filling and draining) By this filling, solidification is started in the cavity 29 and the molten metal filled in the cavity 29 is shrunk, so that the quality of the cast product (product) is stabilized. Then, hot water is supplied to the cavity 29.

That is, the arithmetic and control circuit 41 operates the pressure control valve 34 at the time t4 to supply the gas such as the inert gas of the gas supply source 35 or the compressor air through the exhaust valve 33 and the pipe 32 to the molten metal supply chamber. Further, pressure is supplied to the upper space 6a of 6 to increase the pressure in the upper space 6a from P2 to P3 in a period from time t4 to time t5. The pressure P3 is maintained until time t7 by the arithmetic and control circuit 41 controlling the pressure control valve 37 based on the detection signal of the pressure sensor 39.

On the other hand, the arithmetic and control circuit 41 includes the upper space 6a
As the internal pressure increases, the pressure control valve 37 and the inert gas supply source 38 are operated and controlled based on the detection signal from the molten metal level detection sensor 23, and the inert gas from the inert gas supply source 38 is supplied to the pipe 17a. Through the melt chamber 1
6, the pressure in the upper space 16a of the melt chamber 16 is increased to P2 'between time t4 and time t5 so that the molten metal level S1 is maintained at the level detected by the molten metal level detection sensor 23.
To P4. The pressure P4 is maintained until time t6 by the arithmetic and control circuit 41 controlling the pressure control valve 34 based on the detection signal of the pressure sensor 40.

Further, at time t6, the arithmetic and control circuit 41 controls the operation of the pressure control valve 37 and the inert gas supply source 38, and sends the inert gas from the inert gas supply source 38 via the pipe 17a. The molten metal is further supplied into the molten metal chamber 16, and the pressure in the upper space 16a of the molten metal chamber 16 is increased from P4 to P5 from time t6 to time t6 ′, thereby performing the first draining.

Incidentally, since the pressure in the upper space 6a of the molten metal holding furnace 1 is gradually reduced from the time t7, the hot water is fed into the cavity 29 between the time t5 and the time t7.
When the molten metal filled in the cavity 29 contracts due to solidification, the molten metal is replenished into the cavity 29 by the amount of the contraction, and the quality of the casting (product) is stabilized.

When a predetermined time t7 elapses after the filling of the molten metal 2 '' into the cavity 29, the cavity 2
The heat of the molten metal 2 ″ in 9 is absorbed by the molds 26 and 27, dissipated and solidified. At this time, the solidification of the molten metal in the cavity 29 is performed earlier in the small-volume portions 29a and 29b than in the large-volume portion 29c. Therefore, the molten metal filling path 30
The solidification of the openings of a ′, 30b ′ into the cavity 29
This is performed earlier than the solidification of the opening of the molten metal filling passage 30c 'into the cavity 29. In addition, the molten metal filling paths 30a ', 30
At the time when the opening of the opening b into the cavity 29 is solidified, the molten metal in the molten metal filling paths 30a 'and 30b' is not solidified, and the molten metal filling path 30c 'is opened to the cavity 29. At the time when the portion is solidified, the molten metal in the molten metal filling path 30c 'is not solidified.

The arithmetic and control circuit 41 controls the exhaust valve 33
Is controlled to operate the first port 33a of the exhaust valve 33 and the second port 33a.
The communication with the port 33b is shut off, and the exhaust valve 33
Of the first port 33a to the third port 33c,
The upper space 6a of the molten metal holding furnace 1 is opened to the atmosphere. Thereby, the pressure in the upper space 6a of the molten metal holding furnace 1 is gradually reduced from the time t7 to the time t9, and becomes “0” at the time t9.

On the other hand, the arithmetic control circuit 41 pressurizes and supplies the inert gas from the inert gas supply source 38 to the upper space 16a of the molten metal chamber 16 by the pressure control valve 37 from time t6 to time t8. The second hot water draining is performed while maintaining the pressure in the upper space 16a at P6. Then, at time t8, the arithmetic and control circuit 41 cuts off the communication between the first port 36a and the second port 36b of the exhaust valve 36 and makes the first port 36a and the third port 36c of the exhaust valve 36 communicate with each other. Then, the upper space 16a of the molten metal chamber 16 is opened to the atmosphere. Thereby, the pressure in the upper space 16a of the molten metal chamber 16 is gradually reduced from time t8 to time t9, and becomes “0” at time t9.

As a result, the molten metal in the molten metal chamber 16
At time t7, first, the upper space 6a of the molten metal holding furnace 1
Due to the pressure decrease and the pressure P6 in the upper space 16a of the molten metal chamber 16, the molten metal is returned into the molten metal holding furnace 1 through the stalk 15.

At this time, the molten metal surface S1 in the molten metal chamber 16 is lowered, and first, the molten metal filling pipes 30a, 30b
The inert gas moves to below the lower end of the
0a ', 30b' and the molten metal filling path 30
The molten metal in the molten metal a ', 30b' is forcibly lowered by the inert gas, and then the molten metal surface S1 in the molten metal chamber 16 is further lowered to move below the lower end of the molten metal filling pipe 30c to be inert. The gas is caused to flow into the molten metal charging path 30c ', and the molten metal in the molten metal charging path 30c' is forcibly lowered by the inert gas. In this way, the molten gas in the molten metal filling pipe 30 is filled with an inert gas.
By ascending inside 0, the cavity 29 is cut off at the lower end. Such hot water removal is performed between time t6 'and time t8.

Thereafter, the molten metal in the molten metal chamber 16 is returned to the molten metal holding furnace 1 during a period from time t6 'to time t9.

In this manner, the edge of the molten metal filling paths 30a 'to 30c' to the opening to the cavity 29 is separated at a time difference, so that the molten metal can be filled at a preferable timing according to the size of the volume of each part of the cavity 29. Roads 30a'-30
The c 'hot water can be drained. Next, FIGS. 8A and 8B will be described.

At the time when the openings of the molten metal filling paths 30a 'and 30b' into the cavity 29 are solidified, the molten metal in the molten metal filling paths 30a 'and 30b' is not solidified. The molten metal surface S1 in the chamber 16 is moved to below the lower ends of the molten metal filling pipes 30a and 30b by applying the pressure of P5, and the inert gas is supplied to the molten metal filling path 30.
By flowing the molten metal into the molten metal filling paths 30a 'and 30b', the opening of the molten metal in the molten metal filling paths 30a 'and 30b' to the cavity 29 is first drained. While the hot water is drained, the portion 2 having a large volume in the cavity 29 is removed.
The molten metal 9c is solidified and the opening of the molten metal filling path 30c 'to the cavity 29 is solidified. At the time when the solidification is performed, the molten metal in the molten metal filling path 30c 'is not solidified. In this state, the molten metal filling pipe 30 is pressed by the molten metal surface S1 of the molten metal chamber 16 by the pressure of P6.
c, the molten metal in the molten metal filling path 30c 'is forcibly lowered by the inert gas, and the second molten metal is drained.

(V) Product take-out Then, the arithmetic control circuit 41 sets the upper spaces 16a and 6a
After the internal pressure becomes substantially “0” at time t9, the time t10
Waiting for solidification, the hydraulic circuit 31 is operated and the upper mold 27 is raised integrally with the upper mold mounting plate 21 by a hydraulic cylinder (not shown), and the upper mold 27 is shown in FIGS. 3 (6) and 9. It is separated from the lower mold 26 as described above.

Thereafter, the product receiver (not shown) is moved below the upper mold 27 to release the product held by the upper mold 27, thereby the cast product (product) held by the upper mold 27.
After the product receiver 60 receives the product receiver 60, the product receiver 60 is taken out from below the upper mold 27, so that the cast product 60 is taken out.

[0056]

As described above, according to the first aspect of the present invention, the molten metal is stored in the molten metal chamber provided between the molten metal holding furnace and the mold cavity by pressurizing the molten metal from the molten metal holding furnace. In a low pressure casting method for filling a molten metal in a chamber into a cavity via a molten metal filling path by pressurizing, a lower end of the molten metal in the molten metal chamber is inserted into the mold cavity from the molten metal chamber to the mold cavity. After being filled through the plurality of molten metal filling paths inserted therein, before the molten metal above the molten metal filling path solidifies,
Since the low-pressure casting method of supplying an inert gas to the upper part of the molten metal filling path is adopted, a plurality of molten metal filling paths are installed at the place where shrinkage cavities are generated, and a product with less defective products can be manufactured. Moreover, since the cavity is filled with the molten metal from a plurality of molten metal filling paths,
Even when the solidification of the thick part of the product is slow and the solidification of the molten metal filling path is fast, it is possible to prevent defects such as shrinkage cavities from occurring in the molten metal solidified in the cavity.

Further, the invention of claim 2 provides a molten metal holding furnace,
A molten metal chamber disposed above the molten metal holding furnace, a molten metal guide path having a lower end inserted into the molten metal of the molten metal holding furnace and guiding the molten metal into the molten metal chamber, and a molten metal of the molten metal holding furnace. Molten metal supply means for supplying the molten metal into the molten metal chamber through the molten metal guide path, gas supply means for supplying a gas to the upper part of the molten metal chamber, a mold cavity disposed above the molten metal chamber, and a lower end Parts are inserted into the melt chamber, and have a plurality of melt filling paths for guiding the melt in the melt chamber to the mold cavity, and a lower end of the opening of the melt filling path from a position of the melt surface of the melt chamber. The molten metal filling path arranged at various depths to reach the position of the molten metal, and supplying the molten metal in the molten metal chamber to the mold cavity via the molten metal filling path. Since the configuration provided with means,
Even when the thickness of the product is not uniform, it is possible to prevent the occurrence of a defective product or a hindrance to casting by performing the timing of hot water removal with good timing according to the thickness.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a differential pressure casting device according to the present invention.

FIG. 2 is a pressure characteristic curve diagram showing a temporal relationship such as a pressure on a casting mold of the differential pressure casting apparatus shown in FIG.

FIG. 3 is controlled according to the pressure characteristic curve diagram of FIG. 2;
It is explanatory drawing of the casting process by the differential pressure casting apparatus.

FIG. 4 is an enlarged explanatory view of (1) of FIG. 3;

FIG. 5 is an enlarged explanatory view of (2) in FIG. 3;

FIG. 6 is an enlarged explanatory view of (3) in FIG. 3;

FIG. 7 is an enlarged explanatory view of (4) in FIG. 3;

8A is an enlarged explanatory view of (5a) of FIG. 3, and FIG. 8B is an enlarged explanatory view of (5b) of FIG.

FIG. 9 is an enlarged explanatory view of (6) in FIG. 3;

FIG. 10 is an explanatory view showing an example of a conventional differential pressure casting apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Molten holding furnace 2 ... Molten 6 ... Molten supply chamber 6a ... Upper space 15 ... Stoke (melt guide pipe) 15a ... Molten guide path 16 ... Molten chamber 16a ... Upper space 25 ... Casting mold 26 ... Lower mold 27 ... Upper mold 29 ... Cavity (Mold cavity) 30 ... Molten filling pipe 30a ... Molten filling path 34 ... Pressure control valve (Molten metal supply means) 35 ... Gas supply source (Inert gas supply means) 37 ... Pressure control valve (Molten metal) Filling means) 38: inert gas supply source 41: arithmetic control circuit (control means)

Claims (2)

[Claims] 1. A molten metal chamber is provided between a molten metal holding furnace and a mold cavity. After the molten metal is stored by pressure from the molten metal holding furnace, the molten metal in the molten metal chamber is filled with a molten metal by a pressure. In the low-pressure casting method of filling the cavity via the molten metal, filling the molten metal in the molten metal chamber from the molten metal chamber into the mold cavity through the plurality of molten metal filling paths whose lower ends are inserted into the molten metal chamber. After letting
A low-pressure casting method, wherein an inert gas is supplied to the upper portion of the molten metal filling path before the molten metal in the upper part of the molten metal filling path is solidified. 2. A molten metal holding furnace, a molten metal chamber disposed above the molten metal holding furnace, and a molten metal guide having a lower end inserted into the molten metal of the molten metal holding furnace and guiding the molten metal into the molten metal chamber. A path, a molten metal supply means for supplying the molten metal of the molten metal holding furnace into the molten metal chamber via the molten metal guide path, a gas supply means for supplying gas to an upper portion of the molten metal chamber, and The disposed mold cavity and the lower end are inserted into the melt chamber,
And a plurality of molten metal filling paths for guiding the molten metal in the molten metal chamber to the mold cavity, and a depth from a position of a molten metal surface of the molten metal chamber to a position of a lower end portion of the opening of the molten metal charging path. A casting apparatus comprising: a molten metal filling path arranged in various ways; and a molten metal filling means for supplying the molten metal in the molten metal chamber to the mold cavity via the molten metal filling path.