JPH09300061A - Reduced pressure suction casting device and cast parts using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reduced pressure suction casting device which can soundly mass-produce cast parts without miss-run even in the case of a cast parts having thin thickness and bad castability of a cast stainless steel, etc., by adopting a mold structure capable of effectively applying the reduced pressure up to a product cavity part, and to obtain the cast parts using this. SOLUTION: The reduced pressure suction casting device 1 composed of a mold storage chamber 2 having an opening part 3 at the bottom part, a molten metal introducing part 5 projecting to the opening part 3, a stacked mold part stored in the mold storage chamber 2, having a runner connected to the molten metal introducing part 5 and plural gate parts branching radially from this runner and stacking the molds having the product cavities connected to these gate parts and a pressure reducing device 11 for controlling to reduce pressure in the mold storage chamber 2. The mold is formed with a thermosetting shell by reducing the mold thickness on the back surface of the product cavity and forming gap between the stacked molds. The cast parts is composed of the cast stainless steel cast by using the reduced pressure suction casting device 1 and is a pipe joint having at least a part of <=2.5mm thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum suction casting apparatus and cast parts using the same, and more particularly, to a thin cast stainless steel or the like by using a mold structure that effectively works even when the vacuum is applied to the product cavity. TECHNICAL FIELD The present invention relates to a vacuum suction casting device that enables sound mass production of cast parts having poor castability, and cast parts using the same.

[0002]

2. Description of the Related Art Generally, in the casting of a thin casting having a thin portion such as 5 mm or less, the molten metal poured into the mold is cooled and solidified by contact with the casting mold as compared with a casting having a certain thickness. It is further promoted, the fluidity of the molten metal deteriorates, and casting defects such as defective molten metal rotation easily occur. In the case of a material having poor castability such as stainless cast steel, casting defects such as defective hot rolling are more likely to occur.

The lost wax casting method is known as a technique for producing a thin casting. In this lost wax casting method, a ceramic mold is heated to 700 to 900 ° C.,
A thin wall casting is cast by slowing the cooling rate of the molten metal after pouring to improve the fluidity of the molten metal. But,
This lost wax casting method uses expensive ceramic molds, which is costly and significantly expensive to manufacture.

Further, as a casting technique for thin-walled castings, Japanese Patent Publication No. 6-85990 discloses a product cavity as a vacuum suction casting apparatus for depressurizing a mold chamber and filling molten metal into a mold cavity antigravityally. There is a disclosure to improve productivity by using a ceramic shell mold arranged in a tree shape or a low temperature bonding sand mold in which horizontal sections are integrated.

Further, in Japanese Unexamined Patent Publication No. 7-256430, casting efficiency is improved by vacuum suction casting of a breathable sand mold using a laminated sand mold in which a plurality of stages are stacked vertically to form a product cavit. However, there is a disclosure to reduce the mold cost.

[0006]

However, the ceramic shell mold disclosed in the above Japanese Patent Publication No. 6-85990 has good air permeability, but the mold cost is high. On the other hand, the low-temperature bonded sand mold in which a plurality of horizontal sections are integrated has poor air permeability, so that it is difficult to effectively reduce the pressure inside the product cavity, and defective running around the hot water tends to occur. Also, Japanese Patent Laid-Open No. 7-2
According to Japanese Patent No. 56430, when the lowermost sand mold is immersed in a molten metal and decompressed, air is entrained, and gas defects are likely to occur in a cast product after casting. Furthermore, depressurization does not work effectively around the product cavity of the mold, and it is difficult to obtain a thin casting.

According to the present invention, by using a mold having a structure in which the depressurization works effectively up to the product cavity, even a cast part having a thin wall and poor castability such as stainless cast steel can be mass-produced soundly without casting defects such as non-rotation. A first problem is to obtain a suction casting device, and a second problem is to obtain a cast part that can be cast using the suction casting device.

[0008]

In order to solve the above-mentioned problems, a vacuum suction casting apparatus according to the first aspect of the present invention comprises a mold storage chamber having an opening at the bottom, and a molten metal introducing portion provided so as to project from the opening. A laminated mold that is stored in the mold storage chamber, connects a runner to the molten metal introduction part, radially branches a plurality of gate parts from the runner, and stacks a mold having a product cavity part connected to the gate part, A vacuum suction casting device comprising a pressure reducing device for controlling the pressure of the mold storage chamber, wherein the mold is formed by thermosetting shell by reducing the thickness of the mold on the back surface of the product cavity and forming voids between the laminated parts. Therefore, the feature is that the decompression is effectively applied to the product cavity.

A casting part of the second invention is a casting part manufactured by using the vacuum suction casting apparatus of the first invention, which is made of stainless cast steel and at least a part of which has a wall thickness of 2.5 m.
It is characterized by having a site of m or less. Further, the casting part is a pipe joint.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1 of the Invention) FIG. 1 is a sectional view of an essential part showing an example of an embodiment of a vacuum suction casting apparatus. This vacuum suction casting apparatus 1 includes a mold storage chamber 2 having an opening 3 at the bottom.
And a molten metal introducing portion 8 provided so as to project into the opening 3, and the molten metal introducing portion 8 which is housed in the mold storage chamber 2 and has a runner 6
, A plurality of gate parts are radially branched from the runner 6, and the mold 4 having the product cavity 7 connected to the gate parts and the mold storage chamber 2 are vacuum-sucked from above in a direction indicated by a white arrow. A force is applied to suck the molten metal 15 from the opening 8 of the runner at the lower end of the mold.

Specifically, the vacuum suction casting apparatus 1 has a mold storage chamber (for example, an iron container having an inner diameter of 600 mm and a height of 800 mm) 2 and an opening 3 at the bottom of the mold storage chamber 2. It is provided. A lid member 2a is engaged with the upper portion of the mold storage chamber 2 in a sealed state, and a flexible pipe 9 is attached to an upper end portion of the lid member 2a. The flexible pipe 9 is connected to a decompression device 11 such as a vacuum pump via a decompression control means 10.

The mold 4 is formed by filling a heated mold with silica sand for casting coated with a thermosetting resin to form a shell sand mold element, and stacking the mold elements with their cut-out surfaces aligned (see FIG. 1). There are 10 mold elements in total, which are arranged in the mold storage chamber 2. Here, the shell sand mold has a mold thickness of 4a depending on the mold temperature and firing time during molding.
Is adjusted so that the voids 12 are formed after the mold elements are laminated. The mold 4 is provided with a large number of product cavities 7, and each of the product cavities 7 communicates with the runner 6.

The inner surface of the product cavity 7 is coated with 0.01 to 0.4 mm to improve the casting surface after casting. This coating type is preferably applied to a thickness of 0.15 mm, for example. Packing 23 is arranged between the mold storage chamber 2, the lid member 2a, and the mold 4,
This prevents a decrease in the sealed state of the mold storage chamber 2 and a decrease in the degree of pressure reduction of the cavity 7 of the mold 4.

A melt level sensor 13 for detecting that the vacuum suction casting apparatus 1 is immersed in the melt 15 in the melt holding furnace 14 is attached to the outer surface of the mold storage chamber 2.
It is sensed that the molten metal introduction part of No. 2 was immersed in the molten metal 15 in the molten metal holding furnace 14. Then, when the immersion is sensed, the lowering of the mold storage chamber 2 is stopped, and at the same time, the depressurization device 11 is operated to start depressurization, and the depressurization acts on the product cavity 7 from the gap. Therefore, the molten metal injected into the runner 6 is rapidly filled into the product cavity 7.

The filled molten metal is retained in the product cavity 7 for a predetermined time by a depressurizing force, the solidification is gradually progressed from the surface in the product cavity 7, and the depressurization is released when the predetermined solidification rate, that is, the solid phase rate is reached. Then, the parts other than the product cavity 7 are returned from the mold to the molten metal holding furnace. When the mold 4 is taken out from the mold storage chamber 2 after casting and the mold is removed,
The cast parts in the product cavity 7 are not connected to the runner and are disjointed, so that the sprue folding and the runner folding are unnecessary.
Further, since the molten metal in the runway 6 returns to the molten metal holding furnace 14 by the action of gravity, the injection yield (cast product weight / injection weight) is significantly improved.

FIG. 2 shows a conventional CO ₂ gas mixture obtained by stacking high temperature bonded shell sand mold elements according to an embodiment of the present invention and using a vacuum suction casting device with a mold cavity having a void 12 on the back surface of a product cavity. FIG. 6 is a diagram showing a comparison between the relationship between the depressurization pattern and the filling rate in the mold in which the low-temperature bonded sand mold elements cured in Step 2 are laminated. The depressurization pattern was measured by a pressure sensor installed in the mold housing chamber 2, and the filling rate was measured by a load cell installed in the mold housing chamber. In the high temperature bonded shell sand mold of the embodiment of the present invention, the formation of the voids 12 dramatically improves the air permeability and effectively reduces the pressure. Compared with the case of the conventional low-temperature bonded sand mold in which the voids 12 do not exist, the decompression rate is high, the molten metal is rapidly filled in the product cavity, and casting defects such as non-rotation do not easily occur.

(Second Embodiment of the Invention) First Embodiment
(JIS) S shown in FIG.
A stainless cast steel pipe joint 20 having a CS13 composition was cast. The pipe joint that is a casting part is T-shaped, the width of the straight pipe portion 20a is 88 mm, the dimension is 44 mm from the center of the end of the branch pipe portion 20b,
The minimum wall pressure portion 20c is 2.2 mm, the maximum wall pressure portion 20d is 6
mm. In casting, the molten metal 15 in the molten metal holding furnace 14 is maintained at a temperature of 1570 ° C., the molten metal inlet 8 is immersed and then depressurized, the molten metal 15 is filled up to the product cavity 7, and the depressurized state is released after 20 s. Then, 7 parts of the product cavity were solidified, and the runner part was returned to the molten metal holding furnace 14. The pipe joint 20 after solidification was sound with no turning. Also,
It was possible to cast a large number of pipe joints 20 at the same time.

[0018]

As described above in detail, in the vacuum suction casting apparatus of the first invention, the mold is formed by stacking thermosetting shell molds, and a void is provided between the stacks to form a product cavity portion. The depressurization to (2) effectively works, and even a material having poor castability, such as stainless cast steel, has no casting defects such as non-rotation, and a sound casting part can be obtained. Further, by using the vacuum suction casting apparatus of the first invention, a large number of thin casting parts made of the stainless cast steel of the second invention and having at least a part having a wall thickness of 2.5 mm or less can be simultaneously obtained at low cost. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a vacuum suction casting device showing an example of an embodiment of the present invention.

FIG. 2 is a vacuum suction casting apparatus in a mold in which high temperature bonded shell sand mold elements of an example of an embodiment of the present invention are laminated and having a cavity 12 on the back surface of a product cavity, and a conventional CO ₂ gas cured low temperature. It is a figure which compares and shows the relationship of a pressure reduction pattern and the filling rate in the mold which laminated | stacked the combined sand mold element.

FIG. 3 is a plan view of a stainless steel pipe joint showing an example of an embodiment of a cast part of the present invention.

[Explanation of symbols]

1 vacuum suction casting device, 2 mold storage chamber, 2
a lid member, 3 openings, 4 mold,
4a mold thickness, 5 molten metal introduction part,
6 runners, 7 cavities, 8 runner openings, 9 flexible pipes, 10 decompression control means, 11 decompression devices, 12 voids,
13 melt level sensor, 14 melt holding,
15 Molten metal, 17 Mold chamber, 18
Decompression chamber, 20 pipe fittings, 23
Airtight member.

Claims (3)

[Claims] 1. A mold storage chamber having an opening at the bottom, a molten metal introducing portion provided so as to project from the opening, and a mold storage chamber which is stored in the mold storing chamber and is connected to the molten metal introducing portion by a runner. A reduced pressure suction casting device comprising a plurality of radially branched gate parts, a laminated mold for laminating a mold having a product cavity part connected to the gate parts, and a decompression device for controlling the decompression of the mold storage chamber, Reduced pressure characterized by reducing the thickness of the mold on the back of the product cavity and forming voids between the laminated parts and molding with a thermosetting shell, so that the product cavity can be effectively reduced in pressure. Suction casting equipment. 2. A casting part using the vacuum suction casting apparatus according to claim 1, which is made of stainless cast steel and at least a part of which has a portion having a wall thickness of 2.5 mm or less. 3. The casting part according to claim 2, wherein the casting part is a pipe joint.