JP2939663B2 - Low pressure casting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for forming a pressure chamber above a molten metal holding section, and to seal both sides of an upper part of a molten metal holding furnace.
Terminal chambers communicating with the pressure chambers are respectively formed, heaters are inserted into protective tubes extending between the terminal chambers, and lead wires are respectively connected to both ends of the heaters facing the terminal chambers. Is disposed in the molten metal holding furnace such that the stalk communicating with the cavity in the mold disposed at the lower end of the molten metal in the molten metal holding section is pushed into the molten metal holding furnace,
On the inner surface of the side wall of the so-called reverberatory furnace-type low-pressure casting apparatus, and the molten metal holding furnace that is sealed by housing the crucible that stores the molten metal,
A heater disposed in a heating chamber formed between the inner surface of the side wall and the crucible is supported, and a stalk communicating with a cavity in a mold disposed above the molten metal holding furnace enters the molten metal in the crucible at a lower end. The present invention relates to a so-called crucible-type low-pressure casting apparatus which is disposed in a molten metal holding furnace in such a manner as to be made.

[0002]

2. Description of the Related Art Conventionally, in such a low-pressure casting apparatus, molten metal in a molten metal holding section is supplied to a cavity through a stalk by pressurizing the molten metal holding furnace, and after the molten metal in the cavity is solidified, the above-mentioned pressurized state is maintained. After releasing the mold, the mold is opened.In the low pressure casting apparatus of the reverberatory furnace type, pressure is applied from the terminal chamber to the pressure chamber, and when the pressure is released, the pressure is released from the terminal chamber. In the low-pressure casting apparatus, pressure is applied and released from a portion facing the upper open end of the crucible, that is, a lid of the molten metal holding furnace in the molten metal holding furnace.

[0003]

By the way, when performing low-pressure casting with an aluminum alloy, biscuit-like sodium halide such as sodium fluoride or sodium chloride is used as the most excellent processing material for improving the quality of a cast product. It may be added to the molten metal in the form of a solid flux. However, the sodium halide is thermally decomposed in the molten metal, and a halogen gas having a corrosive property to the aluminum alloy such as a fluorine gas and a chlorine gas is generated and diffused into the air in the molten metal holding furnace.

In the above-described conventional reverberatory furnace type low-pressure casting apparatus, air flows from the terminal chamber to the pressure chamber when pressurized, but air flows from the pressure chamber to the terminal chamber when pressure is released. In addition, when the halogen gas contained in the air enters the terminal chamber, corrosion of the heater and lead wires exposed in the terminal chamber occurs. For this reason, the service life of the heater and the lead wire is reduced to about 1/2 to 1/10 as compared with the case where sodium halide is not added to the molten metal. It was rarely used for low pressure casting of alloys or had to be replaced frequently with heaters and leads. In addition, in the crucible type low pressure casting apparatus, the halogen gas existing above the molten metal in the crucible inevitably flows into the heating chamber at the time of pressurization, and the corrosion of the heater in the heating chamber occurs, so that the above-described refractory type low pressure casting apparatus is used. Similar to casting equipment, difficult to apply sodium halide to low pressure casting with aluminum alloy,
In addition, the heater had to be replaced frequently.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a low-pressure casting apparatus capable of avoiding corrosion of a heater and a lead wire by corrosive gas.

[0006]

According to a first aspect of the present invention, a pressure chamber is formed above a molten metal holding part, and a pressure chamber is formed on both sides of an upper part of a molten metal holding furnace. A terminal chamber communicating with the pressure chamber is formed, a heater is inserted into a protective tube extending between the terminal chambers, and lead wires are connected to both ends of the heater facing the terminal chamber, respectively. In a low pressure casting apparatus arranged in a molten metal holding furnace such that a stalk communicating with a cavity in a mold arranged above the molten metal in the molten metal holding section has a lower end, a pressure control device is provided in both terminal chambers. A pressurized air supply source is connected to the pressure chamber via a pressure chamber, and an exhaust valve is connected to an exhaust path provided in the molten metal holding furnace at a position avoiding the terminal chamber and communicating with the pressure chamber.

According to a second feature of the present invention, the inside of a side wall of a furnace for holding a molten metal, which contains a crucible for storing the molten metal and is hermetically sealed, has a heating device formed between the inner surface of the side wall and the crucible. A low-pressure casting is provided in the molten metal holding furnace such that a heater disposed in the chamber is supported, and a stalk communicating with a cavity in a mold disposed above the molten metal holding furnace causes the lower end of the molten metal in the crucible to protrude. In the apparatus, a pressurized air supply source is connected via a pressure control device to an air supply passage provided in the molten metal holding furnace at a position below the upper open end of the crucible, and the molten metal is positioned at a position facing the upper open end of the crucible. An exhaust valve is connected to the holding furnace.

[0008]

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

FIGS. 1 to 4 show a first embodiment in which the present invention is applied to a low pressure casting apparatus of a reverberatory furnace type. FIG. 1 is a longitudinal sectional front view of a low pressure casting apparatus of a reverberatory furnace type. 2
3 is a sectional view taken along line 2-2 of FIG. 1, FIG. 3 is an enlarged view of a part 3 of FIG. 2, and FIG. 4 is a sectional view taken along line 4-4 of FIG.

Referring first to FIGS. 1 and 2, this reverberatory furnace type low pressure casting apparatus has a mold 6 which can be opened and closed above a molten metal holding furnace 5 and a cavity 7 formed in the mold 6.
A ceramic stalk 8 is provided in the molten metal holding furnace 5 to communicate the upper end thereof.

The molten metal holding furnace 5 is formed in a closed box shape in which a lining 9 made of a fireproof and heat insulating material is provided on the inner surface and an upper end of a metal casing 10 having an open upper end is opened and closed by a lid 11. In the molten metal holding furnace 5, a molten metal holding portion 12 for holding the molten metal 1 made of an aluminum alloy or the like and a pressure chamber 13 above the molten metal holding portion 12 are formed.

A mold 6 arranged above the molten metal holding furnace 5
Is composed of a fixed lower mold 14 and an upper mold 15 that can be moved up and down above the lower mold 14. Thus, the lower mold 14 is fixedly arranged at a position above the lid 11 in the molten metal holding furnace 5. A plurality of guide rods 16 are erected on the lid 11, and the guide rods 16
The upper die 15 is fixed to the elevating table 17 which is guided to move up and down. In addition, a cylinder 19 having a vertical axis on the upper surface of the central part of the ceiling plate 18 connecting the upper ends of the guide rods 17
Are fixed and supported, and a piston rod 19 a movably penetrating the ceiling plate 18 is connected to the lift 17.
Therefore, when the cylinder 19 is contracted, the upper die 15 is raised and the mold 6 is opened, and when the cylinder 19 is extended, the upper die 15 is lowered and the mold 6 is closed. The cavity 7 is formed by a lower mold 14 and an upper mold 15 corresponding to the shape of a product to be cast, and a gate 20 communicating with the cavity 7 is provided at a lower central portion of the lower mold 14.

Between the lid 11 and the lower mold 14, there is provided a cylindrical intermediate stalk 8a for communicating the upper end with the gate 20. The stalk 8 is provided such that the upper end communicates with the intermediate stalk 8a. It is fixed to the lid 11 of the holding furnace 5. The stalk 8 is arranged so as to have an axis extending vertically, and the lower end of the stalk 8 is
It is arranged so as to protrude into the molten metal 1 held by the molten metal holding part 12.

Referring to FIG. 3 and FIG. 4, two pairs of terminal chambers 21a are provided on both sides of the upper portion of the casing 10 at positions where the stalk 8 is interposed therebetween along the longitudinal direction of the casing 10. , 21b; projecting portions 10a, 10a; 10b, 10b forming 21a, 21b are provided, respectively, and the terminal chambers 2 adjacent to each other along the longitudinal direction are provided.
1a, 21a and between the terminal chambers 21b, 21b communicate with each other via communication paths 22a, 22b provided in the lining 9, for example. On both sides of the upper part of the lining 9,
Pressure chamber 13 and terminal chambers 21a, 21b; 21a, 21b
, Two pairs of opposed through holes 23a and 23b are provided, for example, three pairs each.
A ceramic protection tube 24 is inserted into each of the terminals a and 23b so that both ends thereof protrude into the terminal chambers 21a and 21b, respectively. Moreover, the outer diameter of each protective tube 24 is set such that a gap for communicating the pressure chamber 13 in the molten metal holding furnace 5 with the terminal chambers 21a and 21b can be formed between the protective tube 24 and the inner surface of each through hole 23. Each terminal chamber 21a, 21b is a pressure chamber 1
3 are always in communication with each other.

A rod-shaped heater 25 made of silicon carbide is inserted into each of the protection tubes 24.
Lead wires 26 are respectively connected to both ends of each heater 25 in a and 21b, and these lead wires 26 are connected to a power supply device (not shown) via a common terminal rod 27. An insulating material 28 having heat resistance is interposed between both ends of each protection tube 24 and the heater 25.

Pressurized air conduits 29a and 29b are connected to one of the mutually communicating terminal chambers 21a and 21a and one of the mutually communicated terminal chambers 21b and 21b, respectively. 29 a and 29 b are connected to a pressurized air supply source 31 via a common pressure control device 30.

On the side wall of the molten metal holding furnace 5, there is provided an exhaust passage 32 communicating with the pressure chamber 13 at a position avoiding the terminal chambers 21a and 21b, and an exhaust pipe 33 connected to the exhaust passage 32. The exhaust valve 34 is provided at the end of the. Moreover, the pressure taken out in the middle of the exhaust pipe 33 is
The pressure control device 30 controls the pressure in the pressure chamber 13 while detecting the pressure in the exhaust pipe 33, that is, the pressure in the pressure chamber 13 when the pressure in the pressure chamber 13 is pressurized.

The exhaust valve 34 is configured to switch between closing and opening of a valve chamber 35 communicating with the pressure chamber 13 through, for example, an exhaust pipe 33 and an exhaust path 32 by driving a valve body 36 with a cylinder 37. .

Next, the operation of the first embodiment will be described. The pressurized air from the pressurized air supply source 31 is supplied to the terminal chambers 21a and 21 by the pressure controller 30 with the mold 6 closed.
b, the terminal chambers 21a and 21b communicate with the pressure chamber 13, so that the pressure in the pressure chamber 13 increases, and the molten metal held in the molten metal holding section 12 is pushed up in the stalk 8 and the cavity 7 is filled. Thus the cavity 7
The molten metal in the cavity begins to solidify from its upper position,
When the solidification of the molten metal in the inside is completed, the exhaust valve 34 is opened to release the pressure in the pressure chamber 13 and the pressure control device 30
, The supply of the pressurized air from the pressurized air supply source 31 is stopped.

As a result, the molten metal in the stalk 8 falls, and when the mold 6 is opened and the cast product is taken out, the stalk 8
The molten metal level inside the metal falls to the same level as the molten metal level of the molten metal 1 in the molten metal holding section 12.

In this manner, a series of low pressure casting steps is completed. By adding sodium halide to the molten metal as an improving agent, the quality of the cast product can be improved. That is, when sodium halide is added to the low-pressure casting of an intake manifold for an automobile engine, the total rate of occurrence of pressure leakage failure and external surface shrinkage defect is reduced from 7.5% to 0.6% as compared with a case where sodium halide is not added. , And the mechanical properties of the test specimens obtained from the castings were greatly improved as shown in Table 1. This Table 1
Where each numerical value indicates a value when the case where no sodium halide is added is set to 100, and the shock absorption value indicates a result of a Charpy test.

[0022]

[Table 1]

By the way, in the above-mentioned series of casting steps, air does not flow from the pressure chamber 13 to the terminal chambers 21a and 21b. That is, when the pressure in the pressure chamber 13 increases, the pressurized air from the pressurized air supply source 31 flows into the pressure chamber 13 from the terminal chambers 21a and 21b via the gap between the protective tube 24 and the through holes 23a and 23b. It is. While the pressure in the pressure chamber 13 is kept constant, the pressure in the pressure chamber 13 and the pressure in each of the terminal chambers 21a and 21b should be equal. (Not shown) due to embrittlement or distortion due to high temperature.
It is unavoidable that the gas in the pressure chamber 13 is slightly lower than the pressure in the terminal chambers 21a and 21b.
Air does not flow to the 21b side. Therefore, even if a corrosive gas is generated from the molten metal 1 in the molten metal holding furnace 5, the corrosive gas is prevented from flowing into the terminal chambers 21a and 21b, and the heater 25, the lead wire 26, and the terminal rod by the corrosive gas are avoided. 27, avoid corrosion of them, 25, 26, 27
Can be improved in durability. That is, terminal room 2
1a, 21b, the pressure chamber 13 is relieved in pressure. For example, the life of the lead wire 26 and the terminal rod 27 is about three months on average when sodium halide is not added, While the average was about 1 to 2 weeks when sodium halide was added, according to the present invention, even when sodium halide was added, the life could be extended to 4 months or more. .

Further, in the conventional apparatus in which the pressure in the pressure chamber 13 is released through the terminal chambers 21a and 21b, relatively high-temperature air flows from the pressure chamber 13 into the terminal chambers 21a and 21b when the pressure is released. In contrast, according to the present invention,
When the pressure is increased, air at room temperature is supplied from the pressurized air supply source 31 to the terminal chambers 12a and 12 to prevent the high-temperature air from flowing into the terminal chambers 21a and 21b when the pressure is maintained and the pressure is released. , The terminal chambers 21a and 21b do not become relatively high in temperature, and the lead wires 26
The life can be improved.

As a second embodiment of the present invention, as shown in FIG. 5, a flow control valve 38 is connected in the middle of an exhaust pipe 33, and the exhaust valve 34 is closed to control the flow rate in a state where the pressure in the pressure chamber 13 is maintained. A small amount whose flow rate is controlled by the valve 38, for example, 1 per second
Up to about 2 liters of gas may be positively discharged. Instead of the flow control valve 38, a throttle for discharging a small amount of gas when the exhaust valve 34 is closed may be provided. A restrictor or the like for positively discharging a limited amount of gas may be provided at a molten metal supply port (not shown) of the furnace 5 or the like.

FIG. 6 shows a third embodiment of the present invention, and portions corresponding to the above embodiments are given the same reference numerals.

This low-pressure casting apparatus is of a so-called crucible type. The molten metal holding furnace 5 'is provided with an inner lining 9 made of a fire-resistant and heat-insulating material on the inner surface and an upper end of a metal casing 10 having an open upper end. Is formed in a closed box shape which can be opened and closed by a lid 11, and a crucible 40 for storing a molten metal 1 made of an aluminum alloy or the like is accommodated in the molten metal holding furnace 5 ', and an inner surface of a side wall of the molten metal holding furnace 5' A ribbon-shaped heater 42 is disposed in a heating chamber 41 formed between the furnace and the crucible 40 so as to be supported by the inner surface of the side wall of the molten metal holding furnace 5 ′. A stoke 8 whose upper end is connected to a gate 20 communicating with the cavity 7 of the mold 6 is provided on the lid 11 of the molten metal holding furnace 5 '.
Is fixed, and the lower end of the stalk 8 is arranged so as to protrude into the molten metal 1 stored in the crucible 40. Further, the lid 11 supports a temperature detector 44 for detecting the temperature of the molten metal 1.

Air supply passages 43, which communicate with the heating chamber 41, are provided below the upper open end of the crucible 40, for example, on both side walls of the molten metal holding furnace 5 ′ at positions corresponding to the upper end side walls of the crucible 40.
43 is provided, and both air supply paths 43, 43 are connected to the pressurized air supply source 31 via the pressure control device 30. Further, an exhaust pipe 33 is connected to a position facing the upper open end of the crucible 40 in the molten metal holding furnace 5 ', that is, to the lid 11, and an exhaust valve 34 is provided at a terminal of the exhaust pipe 33.
In addition, the pressure taken out of the exhaust pipe 33 is input to the pressure control device 30.

According to the third embodiment, when the pressurized air from the pressurized air supply source 31 is supplied from the pressurized air supply source 31 to the heating chamber 41 from the air supply passages 43, 43 with the mold 6 closed, The pressure in the heating chamber 41 increases, and the molten metal 1 stored in the crucible 40 is pushed up in the stalk 8 and filled in the cavity 7. When the melt solidification in the cavity 7 is completed, the exhaust valve 34 is opened to release the pressure in the heating chamber 41, and the pressure control device 30 supplies the pressurized air from the pressurized air supply source 31. Is stopped, the molten metal in the stalk 8 falls, and when the mold 6 is opened and the cast product is taken out, the molten metal surface in the stalk 8 falls to the same level as the molten metal 1 in the crucible 40. .

In this way, a series of low-pressure casting steps are completed. However, if sodium halide is added to the molten metal as an improving agent, corrosive gas is generated from the molten metal 1 in the crucible 40. However, when the pressure is increased, the pressurized air from the pressurized air supply source 31 flows into the upper part of the heating chamber 41 from both the air supply passages 43, 43, and from above the crucible 40 toward the lower part of the heating chamber 41. Air circulation can be avoided as much as possible. When the pressure is released, the air is discharged from above the crucible 40, so that the flow direction of the air in the heating chamber 41 is upward. Therefore, even if a corrosive gas is generated from the molten metal 1 in the crucible 40, the corrosive gas is prevented from flowing to the portion of the heating chamber 41 where the heater 42 is disposed, and the corrosion of the heater 42 by the corrosive gas is avoided. As a result, the durability can be improved.

[0031]

As described above, according to the first aspect of the present invention, a pressurized air supply source is connected to both terminal chambers via a pressure control device, and the pressure is provided at a position avoiding the terminal chambers. Since an exhaust valve is connected to an exhaust path provided in the molten metal holding furnace in communication with the chamber, it is possible to prevent air from flowing from the pressure chamber to the terminal chamber in the low pressure casting apparatus of the reflection furnace type. When the casting quality is improved by adding sodium halide, it is possible to prevent the heater and the lead wire from being corroded by corrosive gas, and to improve the durability of the heater and the lead wire. .

According to a second feature of the present invention, a pressurized air supply source is connected via a pressure control device to an air supply passage provided in the molten metal holding furnace at a position below the upper open end of the crucible. The exhaust valve is connected to the molten metal holding furnace at a position facing the upper open end of the crucible, so in a crucible type low pressure casting device,
The heater is corroded by corrosive gas when the flow of air from the upper position of the crucible is avoided as much as possible in the heater arrangement portion of the heating chamber and the casting quality is improved by adding sodium halide. Can be prevented, and the durability of the heater can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view of a reverberatory furnace type low pressure casting apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is an enlarged view of a part of FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is a longitudinal sectional front view corresponding to FIG. 1 of a second embodiment of the present invention.

FIG. 6 is a longitudinal sectional front view of a crucible type low pressure casting apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molten metal 5,5 'Molten holding furnace 6 Mold 7 Cavity 8 Stoke 12 Molten holding part 13 Pressure chamber 21a, 21b Terminal chamber 24 Protective tube 25,42 Heater 26 Lead wire 30 Pressure controller 31 Pressurized air supply source 32 Exhaust Path 34 Exhaust valve 40 Crucible 41 Heating chamber 43 Air supply path

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B22D 18/04 B22D 45/00

Claims (2)

(57) [Claims] A pressure chamber (1) is provided above a molten metal holding section (12).
Terminal chambers (21a, 2) communicating with the pressure chamber (13) are provided on both sides of the upper part of the molten metal holding furnace (5) which forms and is sealed.
1b) are formed respectively, and both terminal chambers (21a, 21a) are formed.
b) a heater (25) is inserted into a protective tube (24) installed between them, and a terminal chamber (21) of the heater (25) is inserted.
a, 21b) are respectively connected to lead wires (26) at both ends thereof, and a stalk (8) leading to a cavity (7) in a mold (6) arranged above the molten metal holding furnace (5) is formed of molten metal. In a low-pressure casting apparatus arranged in a molten metal holding furnace (5) such that a lower end of the molten metal (1) of the holding part (12) is inserted into the molten metal (1), a pressure control device (30) is provided in both terminal chambers (21a, 21b). ), A pressurized air supply source (31) is connected to the pressure chamber (13) at a position avoiding the terminal chambers (21a, 21b), and an exhaust path provided in the molten metal holding furnace (5). (32) The low pressure casting apparatus, wherein an exhaust valve (34) is connected. 2. An inner surface of a side wall of a molten metal holding furnace (5 ') which accommodates a crucible (40) for storing the molten metal (1) and is hermetically sealed,
A heater (42) arranged in a heating chamber (41) formed between the inner surface of the side wall and the crucible (40) is supported, and a mold (6) arranged above the molten metal holding furnace (5 '). The stalk (8) leading to the cavity (7) in the crucible (40)
In the low-pressure casting apparatus arranged in the molten metal holding furnace (5 ') such that the lower end thereof protrudes into the molten metal (1), the molten metal holding furnace (5') is located at a position lower than the upper open end of the crucible (40). ) Is connected to a pressurized air supply source (31) via a pressure control device (30) to an air supply passage (43) provided therein.
An exhaust valve (34) is connected to the molten metal holding furnace (5 ') at a position facing the upper open end of the crucible (40).