JPH09239516A - Reduced pressure suction casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of casting defect by using a ceramic mold, making the gas permeability at a cavity sides of a mold larger than that of the proximity of a runner and gate parts, controlling pressure reducing degree as necessary and executing low speed introduction and high speed filling-up of molten metal, at the time of executing suction casting for a precision casting. SOLUTION: In executing the suction casting by arranging the mold 1 into a mold incorporating chamber 5 communicated with a pressure reducing device 16, the product cavity 14 sides of the mold 1 are made of a ceramic mold 9 and the gas permeability thereof is larger than that of the neighborhoods of the runner 11 and the gates 12. Further, if needed, the pressure reducing device 16 is used and the molten metal 4 from a holding furnace 3 is introduced to the proximity of a molten metal introducing part 8 or the proximity of the runner 11 at the low speed. Successively, the pressure reducing degree in the mold housing chamber 5 is controlled so as to be filled up at the high speed to the product cavities 14 from the above part. Then, the adjustment of the gas permeability of the mold 1 can by achieved by applying refractory coating agent 10 all over the part from the runner 11 to the product cavities 14.

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 for producing castings, and more particularly to a vacuum suction casting apparatus for accurately producing precision castings using a ceramic mold.

[0002]

2. Description of the Related Art Conventionally, as a vacuum suction casting apparatus of this type, as shown in FIG. 8, a plurality of gate portions 12 are provided in a mold storage chamber 5 connected to a pressure reducing apparatus (not shown). A product cavity 14 is formed at the end of the mold, and the mold 1 is provided in which each gate portion 12 communicates with the runner 11 located in the longitudinal direction at the center thereof. A molten metal introducing portion 8 is projected from the bottom 6 of the mold housing chamber 5 from the runner 11.
When the depressurizing device is operated while the molten metal introduction part is immersed in the holding furnace 3 which is located below the mold storage chamber 5 and heats and keeps the molten metal 4, the molten metal 4 passes through the molten metal introduction part 8 and the product cavity 14 of the mold 1. Filled inside. Then, when the mold storage chamber 5 is raised, the molten metal 4 in the mold 1 starts to solidify from the outside, the molten metal 4 in the product cavity 14 solidifies, and then the solidification of the gate portion 12 starts. When the pressure reduction is stopped when the gate portion 12 is half solidified and the pressure is returned to the atmospheric pressure, the runner 11
The molten metal 4 drops into the holding furnace 3 and the runner 11 becomes hollow. Then, the casting mold 1 is taken out from the casting mold storage chamber 5, sand is removed, and the gate portion 12 is removed to obtain a casting product.

In Japanese Utility Model Publication No. 3-7066,
As shown in FIG. 9, each gate portion 12 branched into a plurality of locations
There is disclosed a suction casting mold structure that facilitates separation of castings at 12 gate parts and 14 product cavities by providing a connecting path 15 that communicates each gate part 12 with each other, thereby eliminating finishing work.

In Japanese Patent Publication No. 6-85990,
By filling the molten metal with the degree of pressure reduction at the upper end of the runner higher than that in the mold storage chamber, the possibility of damage to the mold and penetration of the melt into the mold wall is reduced, resulting in excellent finishing and dimensional accuracy. There is a disclosure of a vacuum suction casting device for casting.

[0005]

For precision casting of a complex and thin casting such as the core for a dot printer shown in FIG. 7, for example, a ceramic mold is used as a mold, but the cast steel has a poor flowability of molten metal and is often used as a product. The molten metal is not filled up to the end of the cavity, and as a result, casting defects such as improper turning and molten metal boundary may occur.

Also in the conventional vacuum suction casting apparatus disclosed in Japanese Utility Model Publication No. 3-7066 or Japanese Patent Publication No. 6-85990, the mold air permeability is different between the runner or its vicinity and the product cavity. None, the runner and product cavity have similar suction forces. Therefore, there is no directivity of the suction force between the runner and the product cavity, and improper rotation may occur in a fine portion of the product cavity. Further, in the above-mentioned conventional Japanese Utility Model Publication No. 3-7066 or Japanese Patent Publication No. 6-85990, there is no disclosure of controlling the degree of pressure reduction as the molten metal is filled, and the above-mentioned non-rotation If vacuum suction is performed rapidly in an attempt to eliminate the boundary between the molten metal and the molten metal, the molten metal may be disturbed and gas may be entrained, resulting in the occurrence of casting defects such as pinholes in the casting.

The inventors of the present invention have been able to positively direct the molten metal into the product cavity by controlling the air permeability of each part of the mold, even if the material has poor molten metal flowability such as cast steel, and further suck the molten metal. By controlling the degree of pressure reduction from the holding furnace to the molten metal introduction part or near the runway and from the molten metal introduction part or near the runway until the product cavity is filled with molten metal It was found that even in the case of castings, the turbulent flow of the molten metal can be reduced to prevent pinhole defects due to gas entrainment, and the temperature drop of the molten metal can be reduced to fill the product cavity to prevent melt boundaries and non-rotating defects. The present invention was conceived.

[0008]

[Means for Solving the Problems] That is, 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 passage accommodated in the mold storage chamber, and a melt passage is provided in the molten metal introducing portion. Connected, a plurality of gates radially branched from this runner, consisting of a mold to connect to the product cavity from this gate, and a decompression device for controlling the decompression of the mold storage chamber, controlling the degree of decompression of the decompression device. Is a vacuum suction casting apparatus for introducing molten metal in a holding furnace into the product cavity from the molten metal introducing section, wherein the vacuum suction casting apparatus of the first invention has an air permeability of the mold on the product cavity side,
It is characterized in that it is made larger than the vicinity of the runner and the gate.

Further, in the vacuum suction casting apparatus of the second invention, the vacuum apparatus introduces the molten metal from the holding furnace at a low speed to the molten metal introducing portion or the vicinity of the runway, and then the molten metal is introduced from the molten metal introducing port or the vicinity of the runway. It is characterized in that the degree of pressure reduction is set so as to fill the melt up to the cavity at a higher speed to the melt introduction part or the vicinity of the runner.

Further, in the vacuum suction casting apparatus of the third invention, the mold air permeability is made larger on the product cavity side than in the vicinity of the runner and the gate section, and the vacuum apparatus is
The molten metal is slowly introduced from the holding furnace to the molten metal introduction part or the vicinity of the runway, and then the molten metal is filled at a higher speed from the molten metal introduction port or the vicinity of the runway to the product cavity, or to the molten metal introduction part or the vicinity of the runway. As described above, it is set so as to control the degree of pressure reduction.

[0011]

FIG. 1 is a block diagram showing an embodiment of the present invention.
It will be described with reference to FIG. FIG. 1 is a cross-sectional view of a vacuum suction casting apparatus showing one of the embodiments of the present invention, and FIGS. 2 to 5 show a runner, a gate portion, extracted as (A) in FIG.
FIG. 6 is a cross-sectional view of main parts of the product cavity, and FIG. 6 is a decompression control diagram showing the relationship between time and set decompression degree. First, referring to FIG. 1, the mold storage chamber 5 has an opening 1 at the bottom 6.
7 is provided, and a molten metal introducing portion 8 is provided at the opening 17 so as to project. The mold storage chamber 5 stores the mold 1 which contains ceramics and is preheated to about 1000 ° C. and then stored. A runner 11 of the casting mold 1 is connected to the molten metal introducing part 8, a plurality of gate parts 12 are radially branched from the runner 11, and the gate parts 12 are connected to the product cavity 14. Further, a decompression device 16 for decompression control is connected to the mold storage chamber 5 via a decompression port 7. This decompression device 1
6, the molten metal 4 in the holding furnace 3 is introduced into the product cavity 14 from the molten metal introduction part 8. In the present invention, the mold 1 has a greater air permeability on the product cavity 14 side than in the vicinity of the runner 11 and the gate portion 12. For example, the fireproof coating mold 1 is provided on the outer wall of the runner 11 shown in FIG.
It can be achieved by applying 0.

When the air permeability of the mold 1 is increased by increasing the pressure on the product cavity 14 side from the vicinity of the runner 11 and the gate 12, the pressure reduction degree is reduced from the inside of the runner 11 and the gate 12 to the inside of the pressure reducing container 5. The space 2 becomes larger, and the sucked molten metal 4 is directionally filled in the product cavity 14 having a high air permeability. In order to increase the air permeability of the mold 1 from the vicinity of the runner 11 and the gate portion 12 to the product cavity 14 side, in addition to the above-described FIG. Even if the fireproof coating mold 10 is applied to a part of the product cavity 14, or if the fireproof coating mold 10 is applied to the inner wall of the runner 11 in FIG.
This can also be achieved by forming a refractory sleeve 10a having an opening formed in the inner wall of the runner 11 shown in FIG.

To store the mold 1 in the mold storage chamber 5, first, the molten metal introducing portion 8 is attached to the opening 17 of the bottom portion 6 via an airtight member. Next, the shell mold 9 is placed on the molten metal introducing part 8. Then, the mold housing chamber 5 is covered, and the mold 1 and the molten metal introduction part 8 are pressed against the bottom part 6 from the top by a pressurizing means (not shown) by air pressure to ensure the airtightness of the mold housing chamber 5.

After the above preparations are completed, the mold storage chamber 5 is lowered and the molten metal introducing section 8 is inserted into the holding furnace 3.
At the same time, the depressurizing device 16 is operated to perform depressurization sufficient to fill the runner 11 of the mold 1 and the product cavity 14 with the molten metal through the depressurizing port 7. This pressure reduction control is based on the time-pressure reduction degree pressure control diagram shown in FIG. That is, in FIGS. 6A and 6B, the molten metal 4 is transferred from the holding furnace 3 to the molten metal introduction part 8
It is a section introduced to the vicinity of the runway 11 and is introduced at a low speed by controlling the degree of pressure reduction of the pressure reducing device 16. Next, (b) to (c) are sections in which the molten metal 4 is filled in the product cavity 14 from the vicinity of the molten metal introducing portion 8 or the runner 11.
By controlling the degree of pressure reduction of the pressure reducing device, the molten metal is filled at a higher speed than in (a) and (b).

The molten metal 4 sucked by the reduced pressure passes through the inner cylinder of the shell mold 9 and the gate portion 12 and flows into the product cavity 14. At that time, the mold 1 is the product cavity 1
Since the air permeability is higher on the 4 side than around the runner 11 and the gate portion 12, a strong suction force is applied to the product cavity 14
Act with directivity to. Therefore, product cavity 1
The molten metal is filled up to the small part of 4. Product cavity 1
4 and the gate 12 are kept under reduced pressure until the molten metal is cooled, and then the reduced pressure is released to return the molten metal 4 in the central portion of the runner 11 where solidification has not progressed to the holding furnace 3. After the casting is completed, the mold storage chamber 5 is raised, the mold storage chamber 5 is moved to another place, and the mold 1 having the casting therein is collapsed. By repeating the above steps, a complex thin-walled precision casting can be obtained with high quality.

[0016]

EXAMPLE A dot printer core 20 shown in FIG. 7 is cast by the vacuum suction casting apparatus shown in FIG. The dot printer core 20 obtained by casting has C: 0.03% or less by weight% and Si: 2.70 to 3.20 as main components.
%, The balance consisting essentially of Fe and unavoidable impurities, outer diameter 33 mm, inner diameter 15 mm, height 12 mm, thickness (t1
) 2 mm, thickness (t2) 3.5 mm, thickness (t3) 1
mm. First, mold 1 obtained by 45 castings in one casting
As a core for dot printer including ceramics
The product cavity 14, the runner 11, and the gate portion 12 are held, and the mold 10 is formed around the runner 11 and the gate portion 12.
Preheat to about 00 ° C. Fig. 11 shows an outline drawing of the mold 1.
Shown in In the mold 1 shown in FIG. 11, 11 is a runner, 12 is a gate portion, and 14 is a product cavity. This mold 1
After being placed on the molten metal introducing part 8 protruding to the bottom part 6, the mold housing chamber 5 is covered and the airtightness is secured. Next, the mold storage chamber 5 is lowered, immersed in the molten metal 3 held at 1650 ° C. in the holding furnace 4, and depressurized by the depressurizing device.

The degree of pressure reduction is, as shown in FIG.
During 1 sec of (b), the set pressure reduction degree is 0 to -400 mm.
Introduce the molten metal at low speed for 4 seconds until Hg is reached,
Next, during the 1.5 seconds of (b) to (c), the degree of pressure reduction is set so as to fill the molten metal at high speed with 2 seconds until the set degree of pressure reduction reaches 0 to -400 mmHg. The dot printer core 20 after casting does not have pinhole defects due to gas entrainment, nor does it have a hot water boundary or non-rotating defects.

For comparison, the decompression degree is set to 2 seconds until the set decompression degree becomes 0 to -400 mmHg during 0.5 seconds as shown by the dotted line in FIG. Introduced, and then 2.5d of (d) to (e)
Between c, the degree of pressure reduction was set so that the molten metal was filled at a low speed for 4 seconds until the degree of pressure reduction was set to 0 to −400 mmHg. As a result, in the dot printer core 20 after casting, pinhole defects, which are considered to be caused by gas entrainment, were partially generated, and hot water boundaries and non-rotating defects were also partially generated.

[0019]

As described above in detail, in the vacuum suction casting apparatus of the present invention, the air permeability of the mold is made larger on the product cavity side than in the vicinity of the runner and the gate part, and if necessary, the molten metal is spun at a low speed. Since the degree of pressure reduction is controlled so that the molten metal is charged at high speed, even in complex and thin precision castings, turbulent flow of the molten metal is reduced to prevent pinhole defects due to gas entrainment, and By reducing the temperature drop and filling the product cavity, it is possible to prevent hot water flow and imperfections.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a vacuum suction casting device showing one of the embodiments of the present invention.

FIG. 2 is a cross-sectional view of an essential part of an embodiment of the gate portion and the product cavity extracted as (A) in FIG.

FIG. 3 is a cross-sectional view of essential parts of another embodiment of the gate portion and the product cavity extracted as (A) in FIG.

FIG. 4 is a cross-sectional view of a main part of still another embodiment of the gate portion and the product cavity extracted as (A) in FIG.

5 is a cross-sectional view of a main part of still another embodiment of the gate portion and the product cavity extracted as (A) in FIG.

FIG. 6 is a decompression control diagram showing the relationship between time and set decompression degree.

FIG. 7 is a sketch showing a dot printer core as an example of a precision cast product.

FIG. 8 is a sectional view of a conventional vacuum suction casting device.

FIG. 9 is a cross-sectional view of another conventional vacuum suction casting device.

[Explanation of symbols]

1: template, 2: depressurized space, 3:
Holding furnace, 4: molten metal, 5: mold storage chamber,
6: bottom part, 7: decompression port, 8: molten metal introduction part, 9: ceramic mold, 10: coating mold,
11: runner, 12: gate, 14:
Product cavity, 15: connecting path, 16: pressure reducing device, 20: dot printer core.

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. More radially split the gate part, consisting of a mold that connects to the product cavity from the gate part, and a decompression device that controls the decompression of the mold storage chamber, and controls the degree of decompression of the decompression device to hold the molten metal in the holding furnace. A reduced pressure suction casting device for introducing the molten metal into the product cavity,
The vacuum suction casting apparatus is characterized in that the mold has an air permeability greater on the product cavity side than on the runner and near the gate. 2. 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 accommodated in the mold storing chamber and is connected to the molten metal introducing portion. More radially split the gate part, consisting of a mold that connects to the product cavity from the gate part, and a decompression device that controls the decompression of the mold storage chamber, and controls the degree of decompression of the decompression device to hold the molten metal in the holding furnace. A reduced pressure suction casting device for introducing the molten metal into the product cavity,
The depressurizing device introduces the molten metal from the holding furnace at a low speed to the molten metal introducing part or the vicinity of the runner, and then the molten metal is faster from the molten metal introducing port or the vicinity of the runner to the product cavity, or to the molten metal introducing part or the vicinity of the runner A reduced pressure suction casting apparatus, which is set so as to control the degree of pressure reduction so that the molten metal is filled in. 3. 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. More radially split the gate part, consisting of a mold that connects to the product cavity from the gate part, and a decompression device that controls the decompression of the mold storage chamber, and controls the degree of decompression of the decompression device to hold the molten metal in the holding furnace. A reduced pressure suction casting device for introducing the molten metal into the product cavity,
The air permeability of the mold is such that the product cavity portion side is larger than the runner and the vicinity of the gate portion, and the decompression device introduces the melt at a low speed from the holding furnace to the melt introducing portion or the vicinity of the runner, and then the melt. The decompression suction is set so that the degree of decompression is controlled so that the molten metal is filled at a higher speed from the molten metal introduction port or near the runway to the product cavity, and from the molten metal introduction part or near the runway at higher speed. Casting equipment.