JPH1147911A - Differential pressure casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a differential pressure casting method capable of further shortening a charging time and a casting time in the case of charging and casting a molten metal in a die and capable of keeping the produce quality at a constant level. SOLUTION: In a differential pressure casting method, after a molten metal 2 is stored in a molten metal chamber 16 provided below a die 25 from a molten metal holding furnace 1 up to a prescribed level S1 by a differential pressure, a molten metal 2' is charged and cast into a cavity 29 in the die 25 by the differential pressure or suction through a molten metal charging passage 30a whose the lower end is inserted in the molten metal stored in the molten metal chamber 16 and further, the storage quantity of the molten metal 2' in the molten metal chamber 16 is set so that a molten metal level in the molten metal chamber 16 is constantly above the lower end of the molten metal charging passage 30a from the start of charging into the cavity 29 to the end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure casting method in which a molten metal is filled in a cavity by a pressure difference or suction. Here, the differential pressure casting method is, for example, a casting method in which the cavity is depressurized and the molten metal is sucked and filled into the cavity, or a holding furnace and the cavity are pressurized, and then the cavity is depressurized, thereby providing a pressure difference to the molten metal. Into the cavity.

[0002]

2. Description of the Related Art As such a differential pressure casting method, for example,
The technique disclosed in Japanese Patent Application Laid-Open No. 5-123850 (FIG. 1)
0). According to this, the molten metal in the holding furnace is pressurized, or the cavity is depressurized, and the molten metal is directly introduced into the cavity through the stalk inserted into the molten metal in the holding furnace.

[0003]

However, a gas pressure is applied to the surface of the molten metal in the holding furnace to push up the molten metal in the holding furnace into the mold through the stalk, Is reduced, and the molten metal is filled into the cavity by this depressurizing force, so that the cavity is raised and filled at once from the holding furnace to the cavity, so that the capacity of the holding furnace is large. As the surface of the bath changes
The conditions of pressurization or decompression must be changed each time, and it is difficult to provide a product of constant quality, and there has been a problem that it takes time to adjust.

Accordingly, an object of the present invention is to provide a differential pressure casting method capable of accelerating a casting cycle and constantly maintaining a constant product quality without adjusting pressure conditions every time casting is performed. It is in.

[0005]

In order to achieve this object, according to the first aspect of the present invention, a molten metal is stored to a predetermined molten metal level in a molten metal chamber provided below a mold from a molten metal holding furnace by a pressure difference. Thereafter, by a pressure difference or suction, a differential pressure casting method of filling and casting the molten metal into a cavity in the mold through a molten metal filling path having a lower end inserted into a stored molten metal of the molten metal chamber, The amount of molten metal stored in the molten metal chamber is set such that the level of the molten metal in the molten metal chamber is always above the lower end of the molten metal charging path from the start of filling into the cavity to the end of filling. Differential pressure casting method.

According to a second aspect of the present invention, in the first aspect, the storage amount of the molten metal from the lower end of the molten metal filling path of the molten metal chamber to the molten metal surface before the start of suction is a casting space above the molten metal surface. Is suitably 1 to 5 times the volume of
It is a differential pressure casting method characterized in that it is twice as large.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a differential pressure casting method according to the present invention will be described below with reference to the drawings of a casting apparatus for realizing the method.

<Mechanical Configuration 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 a molten metal holding furnace 1 is separated 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 venting device) inserted into the molten metal replenishing chamber 5 through the lid 3, and 9 denotes a molten metal replenishment provided on the molten metal replenishing 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 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 disposed 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 provided.
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.

By forming the bottom wall 14a of the molten metal container 14 into a tapered shape, when the molten metal 2 'in the molten metal container 14 is pushed downward to the molten metal holding furnace 1, 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.

A closed case 18 is provided on the mold support 13 and the molten metal container 14. The sealed case 18 closes the bottom plate 19 that closes the upper ends of the mold support 13 and the molten metal container 14, the peripheral wall member 20 that is air-tightly fixed on the bottom plate 19, and closes the upper end of the peripheral wall member 20. Lid 21
Having.

Reference numeral 22 denotes a mold chamber in the closed case 18.
Moreover, the bottom plate 19 has an upper space 16 of the molten metal chamber 16.
The level detecting sensor 23 protruding into a is fixed, and a connection port 24 for suction is formed at the upper end of the peripheral wall member 20.

A casting mold 25 is provided in the mold chamber 22. The casting mold 25 has a lower mold 26 fixed on the bottom plate 19 and an upper mold 27 arranged on the lower mold 26. The upper mold 27 is fixed to a lower surface (inner surface) of the lid 21 via a support member 28. This mold 2
A product-shaped cavity 29 is formed between 6 and 27. Further, the lower mold 26 has a plurality of molten metal filling pipes 30 extending vertically and having upper ends communicating with the cavities 29.
Has been fixed. The molten metal filling pipe 30 is connected to the bottom plate 19.
And protrudes into the molten metal chamber 16. 30a
Is a molten metal filling path in the molten metal filling pipe 30. The outer peripheral surface of the molten metal filling pipe 30 and the lower surface of the bottom plate 19 are covered with a protective layer 19a made of cast iron, and the surface of the protective layer 19a is covered with ceramic wool (not shown) or the like. 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.

The lid 21 is a hydraulic cylinder (not shown).
1, the hydraulic cylinder is driven and controlled by a hydraulic circuit 31.
In addition, the mold support 13, the bottom plate 19, and the peripheral wall member 20 can be formed integrally. In addition, the mold support 13 and the peripheral wall member 20 are integrally formed, and the peripheral wall member 2
0, an inner flange is protruded from the lower end of the casting mold 2 and the bottom plate 19 is detachably attached to the inner flange.
Even if the number and position of the molten metal filling pipes 30 change due to a change in the specification of the product to be cast in Step 5, it can be dealt with only by changing the bottom plate 19.

Here, the amount of the molten metal 2 'stored in the molten metal chamber 16 where the molten metal 2' is preliminarily raised to near the casting mold 25 before performing suction casting will be described. The predetermined level S1 detected by the level detecting sensor 23 is at the lower end of the molten metal filling pipe 30, that is, at the molten metal filling path 3
0a is above the lower end. When the cavity 29 is filled with suction, the molten metal surface S1 of the molten metal chamber 16 temporarily drops, but since the pressure P1 in the molten metal holding furnace upper space 6a is maintained, the molten metal 2 in the molten metal supply chamber 6 is maintained. Is automatically supplied through the molten metal guide path 15a, so that the molten metal surface S1 is maintained. Note that P1 is pressure-corrected every several shots as the molten metal level S2 decreases.

When the molten metal surface S1 of the molten metal chamber 16 is temporarily lowered by suction filling into the cavity 29, the inert gas does not enter the cavity 29 from the molten metal filling passage 30a below the lower end of the molten metal filling passage 30a. A large amount of molten metal is required. That is, the storage amount of the molten metal 2 ′ in the molten metal chamber 16 is set such that the molten metal surface S 1 of the molten metal chamber 16 is always above the lower end of the molten metal charging path 30 a from the start of filling the cavity 29 to the end of filling. ing. Note that the inert gas is for preventing oxidation of the molten metal.

The amount of molten metal stored in the molten metal chamber 16 before the start of suction is suitably 1 to 5 times the volume of the casting space including the cavity 29 above the lower end of the molten metal filling path 30a.
Under this condition, the lower end of the molten metal filling path 30a is
And does not come above, the melt 2 in the melt chamber 16
The water temperature of 'does not drop too much. Furthermore, this molten metal 2
The storage amount of 'is preferably 1 to 2 times. This is preferable for lowering the casting cycle and saving energy because the molten metal 2 in the molten metal supply chamber 6 is supplied through the stalk 15 if the molten metal surface S1 lowers even slightly.

<Molten metal pressurizing system> As described above, the molten metal holding furnace 1
Has a connection port 11 communicating with the upper space 6a of the molten metal supply chamber 6.
Is provided, and a connection port 17 communicating with the upper space 16 a is provided in the molten metal chamber 16.

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

Further, a pipe 17a for supplying an inert 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 discharge side of an inert gas supply pressure control valve 37 is connected to the second port 36b, and an inert gas supply source 38 is connected to the inflow side of the pressure control valve 37. In the present embodiment, the third port 36c of the exhaust valve 36 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. Reference numeral 36c 'denotes a displacement control valve for controlling the discharge speed.

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 compressor air, and the inert gas supply source 38 is filled with an inert gas such as argon gas or nitrogen gas. The pressure signals from the pressure sensors 39 and 40 are input to an arithmetic and control circuit (control means) 41, and the arithmetic and control circuit 41 converts the exhaust signals to the exhaust valves 33 and 36 and the pressure control valve 3.
4, 37 are operated.

<Decompression System> Further, as described above, the connection port 24 for suction is formed at the upper end of the peripheral wall member 20 of the sealed case 18. The connection port 24 is connected to a pipe 42 for suction (for pressure reduction), and the pipe 42 is connected to a first port 43 a of an atmosphere release valve, that is, an atmosphere introduction valve (three-way electromagnetic switching valve) 43. A vacuum pump 46 is connected to the second port 43 b of the 43 via a pressure reducing control valve 44 as a pressure reducing means.
The third port 43c of the atmosphere introduction valve 43 is open to the atmosphere. However, the third port 43c may be connected to a gas recovery device to reuse the inert gas discharged from the third port 43c.

Further, a vacuum sensor 45 is mounted in the middle of the pipe 42. The output signal from the vacuum sensor (pressure reduction sensor) 45
The operation of the atmospheric introduction valve 43 and the pressure reduction control valve 44 is controlled by the arithmetic and control circuit 41. Note that the level detection signal from the level detection sensor 23 is also input to the arithmetic and control circuit 41.

<Operation> Next, a casting process involving a control operation of 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 (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), and (c) shows the suction pressure acting on the casting mold 25. And the pressure characteristic curve 5 of (a)
The pressure characteristic curves 51 of 0 and (c) indicate that the molten metal 2 is pushed up to a predetermined height in the molten metal chamber 16 and the molten metal surface S1 of the molten metal 2 ′ in the molten metal chamber 16 is
At the time of detection by the
When the pressure in the upper space 16a in the inside is equal to the atmospheric pressure,
The pressure in the upper space 16a is shown as "0". Further, the pressure characteristic curve 52 of (b) indicates that when no pressure is 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 shown as "0".

(I) Start t1 in FIG. 2 corresponds to the start in (1) in FIG. 3, ie, 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 operation control circuit 41 controls the operation of the hydraulic circuit 31 at time t2 after the start of the supply of the inert gas to operate the hydraulic cylinder (not shown), and the lid 21 is moved to the position shown in FIG. 4 is lowered from the position shown in FIG. 4 to contact the upper end of the peripheral wall member 20 as shown in FIGS. 3 (2) and 5, and the upper opening end of the mold chamber 22 is closed and hermetically closed. At this time, the upper mold 27 is also lowered and brought into contact with the lower mold 26 to perform mold clamping.

At this point, the arithmetic control circuit 41
By connecting the ports 43a and 43c of the air introduction valve 43,
The pipe 42 is open to the atmosphere. Moreover, in this case,
The inert gas from the inert gas supply source 38 is supplied to the pipe 17a.
The inert gas is supplied into the molten metal chamber 16 via the molten metal filling path 30a.
Is supplied (filled) into the cavity 29 and leaks into the mold chamber 22 from a gap between the mating portions of the molds 26 and 27.

(Iii) Detection of the molten metal level The arithmetic and control circuit 41 stops the operation of the pressure control valve 37 at time t3 immediately after the closing of the casting mold 25, and stops the supply of the inert gas to the molten metal chamber 16. Stop.

On the other hand, the arithmetic and control circuit 41 connects the ports 33a and 33b of the exhaust valve 33 at time t3,
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.

The molten metal may be supplied by using an electromagnetic pump.

When the molten metal 2 is pushed up and the molten metal surface S1 in the molten metal chamber 16 contacts the molten metal surface detecting sensor 23 at time t4 as shown in FIGS. 3 (3) and 6, the molten metal surface S1 is detected. Is detected by the sensor 23,
3 outputs a molten metal level detection signal and inputs it to the arithmetic and control circuit 41.

When the arithmetic and control circuit 41 receives the molten metal level detection signal, it controls the operation of the pressure control valve 34 to maintain the pressure P1 in the upper space 6a. In this state, the lower end of the molten metal filling pipe 30 is inserted into the molten metal 2 ′ in the molten metal chamber 16.

(Iv) Filling of the molten metal (decompression of the mold chamber 22) On the other hand, when the arithmetic control circuit 41 receives the level detection signal from the level detection sensor 23,
In 4, the ports 43 a and 43 b of the air introduction valve 43 are communicated, and the pressure reduction control valve 44 is operated, so that the mold chamber 2
Start pressure reduction of 2. At this time, the pressure is detected by the vacuum sensor 45, and a detection signal from the vacuum sensor 45 is input to the arithmetic and control circuit 41.

At this time, the depressurizing force in the cavity 29 of the casting mold 25 is changed from 0 to −P6 between time t4 and time t5.
(Kg / cm2) and then from time t5 to t
-P6 (Kg / cm2) to -P7 (Kg / c
m2) (-P6> -P7). And
The molten metal 2 ′ in the molten metal chamber 16 is sucked into the cavity 29 of the casting mold 25 through the molten metal filling path 30 a, and FIG.
And filling as shown in FIG. This filling is performed until time t5.

With this filling, the surface S1 of the molten metal 2 'in the molten metal chamber 16 tends to drop, but the molten metal supply chamber 6
The pressure in the upper space 6a of P
Is maintained so that the molten metal in the molten metal holding furnace 1 is replenished into the molten metal chamber 16 by the pressure P1, and the molten metal surface S1 is to be maintained substantially constant.

When the filling of the molten metal into the cavity 29 is completed, the heat of the molten metal in the cavity 29 is transferred to the mold 26,
After being absorbed by 27, heat is released and solidification has already started.

(Feeding water) Since the molten metal filled in the cavity 29 is contracted by the start of the solidification, the molten metal filled in the cavity 29 is pushed into the cavity 29 in order to stabilize the quality of the cast product (product).

That is, before the molten metal 2 ′ in the molten metal chamber 16 descends below the lower end of the molten metal filling pipe 30, the arithmetic and control circuit 41 determines that the degree of decompression (vacuum degree) in the mold chamber 22 is a predetermined value ( -P6) is detected at time t5 based on the detection signal from the vacuum sensor 45 at this time t5, the pressure control valve 34 is operated at this time t5, such as the inert gas of the gas supply source 35 or the compressor air or the like. Gas is supplied to the molten metal supply chamber 6 through the exhaust valve 33 and the pipe 32.
Is further supplied to the upper space 6a, and the pressure in the upper space 6a is increased from P1 to P2 in a period from time t5 to time t6.

On the other hand, the arithmetic and control circuit 41 controls the operation of the pressure control valve 37 almost simultaneously with the start of the pressure increase in the upper space 6a of the molten metal holding furnace 1, and the communication between the inert gas supply source 38 and the exhaust valve 36. Break the state. Thereby, when the pressure in the molten metal holding furnace 1 rises, the pressure in the upper space 16a of the molten metal chamber 16 is increased, and the upper space 16a is increased.
The pressure in a is increased to P3 in the time from time t5 to time t6. In addition, the inert gas supply source 3
Since the communication between the exhaust gas 8 and the exhaust valve 36 is shut off, the pressure P3 in the upper space 16a of the molten metal chamber 16 becomes the same as the pressure P2 applied to the upper space 6a of the molten metal supply chamber 6.

The pressure P2 (= P3) acts on the cavity 2 of the casting mold 25 through the molten metal 2 'in the molten metal chamber 16 and the plurality of molten metal filling paths 30a, and the volume is reduced by cooling. Replenish the molten metal. As a result, a so-called feeder effect is provided.

The pressure P3 is maintained until time t9 by the operation control circuit 41 controlling the pressure control valve 37 based on the detection signal of the pressure sensor 40, and the pressure P2 is calculated based on the detection signal of the pressure sensor 39. Control circuit 4
1 is maintained until time t10 by controlling the pressure control valve 34.

(Decompression stop) The arithmetic control circuit 41
After detecting at time t6 that the pressure signals from the pressure sensors 39 and 40 have reached P2 and P3, at time t7 the operation of the pressure reducing control valve 44 is controlled to close the middle of the passage in the pressure reducing control valve 44 and to release the air. Inlet valve 43
The ports 43a and 43c are communicated with each other, and the pipe 42 is communicated with the atmosphere. As a result, the pressure in the mold chamber 22 rises to atmospheric pressure (here, “0”). When the pressure reduction control valve 44 is stopped, the cavity 29
The filling of the molten metal into the interior has been completed.

(V) Hot Water Draining and Returning When a predetermined time t9 elapses after the filling of the molten metal 2 ″ into the cavity 29, the molten metal 2
Although the heat of ″ is absorbed by the dies 26 and 27 and is radiated and solidified, the molten metal in the molten metal filling path 30a is in a state of not being solidified.

At this time t9, the arithmetic control circuit 41
The inert gas is supplied from the inert gas supply source 38 by the pressure control valve 37 to the upper space 1 of the molten metal chamber 16.
6a to supply pressure to the upper space 16 of the molten metal chamber 16.
The pressure in a is increased from P3 to P4, and the molten metal in the molten metal chamber 16 is lowered to the lower end of the molten metal chamber 16 below the lower end of the molten metal filling pipe 30 as shown in FIGS.

As a result, the molten gas in the molten metal filling pipe 30 is cut off at the lower end of the cavity 29 by the inert gas rising in the molten metal filling pipe 30, and flows downward by its own weight. The molten gas is flowed down to the molten metal supply chamber 6 by the inert gas supplied therein, so that the molten metal is cut off.

The operation control circuit 41 controls the operation of the pressure control valve 33 at time t10 to open the upper space 6a of the molten metal holding furnace 1 to the atmosphere, and then controls the operation of the pressure control valve 36 at time t11. Then, the upper space 16a of the molten metal chamber 16 is opened to the atmosphere, and the molten metal guide path 1 is opened.
The molten metal in 5 a is returned to the molten metal supply chamber 6. As a result, the pressure in the upper spaces 6a and 16a drops and the time t
At the time of 12, it is set to approximately “0”.

(Vi) Product take-out Then, the arithmetic and control circuit 41 controls the upper spaces 16a and 6a
Immediately after the internal pressure becomes substantially "0" at time t12, the hydraulic circuit 31 is operated and the lid 21 is raised by a hydraulic cylinder (not shown) to be separated upward from the peripheral wall member 20, and The mold 27 is raised integrally with the lid 21, and the upper mold 27 is separated from the lower mold 26 as shown in FIGS. Thereafter, a product receiver (not shown) is moved below the upper mold 27 to release the product held by the upper mold 27, so that the cast product (product) 60 held by the upper mold 27 is transferred to the product receiver. After receiving the product, the cast 60 is taken out by taking out the product from below the upper mold 27.

[0053]

As described above, according to the first aspect of the present invention, after a molten metal is stored from a molten metal holding furnace to a molten metal chamber provided below a mold to a predetermined molten metal level by a pressure difference, the pressure difference or suction is performed. Thereby, the cavity in the mold is filled with the molten metal through a molten metal filling path in which a lower end is inserted into the molten metal stored in the molten metal chamber, and the molten metal is cast.The storage amount of the molten metal in the molten metal chamber is further reduced. From the start of filling to the cavity to the end of filling, the molten metal chamber is set so that the surface of the molten metal is always above the lower end of the molten metal filling path.
The distance between the cavity and the surface of the molten metal chamber is always constant, and the filling distance is short because the suction distance of the molten metal is short. In addition, pressure adjustment is not required for each casting, the casting cycle is fast, and products of constant quality are obtained. And a differential pressure casting method capable of casting with even smaller energy can be provided. Furthermore, the lower end of the molten metal filling path does not come above the level of the molten metal,
Good casting quality can be achieved without gas entrainment, such as gas such as inert gas entering the cavity together with the molten metal, and without risk of being taken into the product.

According to a second aspect of the present invention, in the first aspect, the storage amount of the molten metal from the lower end of the molten metal filling path to the molten metal surface of the molten metal chamber before the start of suction is determined by the volume of the casting space above the molten metal surface. 1 to 5 times is appropriate, and preferably 1 to 2 times, so in addition to the effect of claim 1, the preferred is 1 to 2 times, but if it is within 5 times, the mold is The molten metal can be replenished within the tightening cycle. In addition, since the temperature of the molten metal in the molten metal chamber is not excessively lowered, good casting quality can be obtained. Further, if the predetermined level of the molten metal lowers even slightly, the level of the molten metal is raised, so that the temperature of the molten metal supply chamber is reduced. Since the molten metal is supplied through the stalk, it is possible to provide a differential pressure casting method that is preferable for shortening the casting cycle and saving energy.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a differential pressure casting apparatus used for a differential pressure casting method according to the present invention.

FIG. 2 is a pressure characteristic curve diagram showing a temporal relationship such as a suction pressure to 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;

FIG. 8 is an enlarged explanatory view of (5) in FIG. 3;

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 30 ... Molten filling pipe 30a ... Molten filling path 35 ... Gas supply source 38 ... Inert gas supply source 46 ... Vacuum pump (decompression means)

Claims (2)

[Claims] After a molten metal is stored in a molten metal chamber provided below a mold from a molten metal holding furnace to a predetermined molten metal level by a pressure difference, the molten metal is stored in a cavity in the mold by a pressure difference or suction. A casting method in which the molten metal is filled and cast through a molten metal filling path having a lower end inserted into the stored molten metal, wherein the amount of the molten metal stored in the molten metal chamber is filled from the start of filling into the cavity. 2. The differential pressure casting method according to claim 1, wherein the molten metal chamber is set so that the surface of the molten metal is always above the lower end of the molten metal filling path until the end of the process. 2. The molten metal storage amount from the lower end of the molten metal filling path to the molten metal surface of the molten metal chamber before the start of suction according to claim 1, wherein the volume of the molten metal is 1 to 5 times the volume of the casting space above the molten metal surface.
A differential pressure casting method characterized in that the ratio is suitably double, preferably 1-2 times.