JPH02303669A - Suction casting method with shell mold - Google Patents

Abstract

PURPOSE:To prevent the development of casting defect of underfill, etc., by pouring molten metal into cavity while concentratedly sucking the air and reducing the pressure through high ventilating range formed in a shell mold near the position where misrun is easily developed in the cavity. CONSTITUTION:By working a water sealing type vacuum pump 12 before pouring the molten metal, the air in a venting hole 3a is beforehand sucked. The air in the cavity 4 through a porous filter 17 and the air in a vessel 7 with ventilation in the shell mold 1 are sucked, respectively, and negative pressure condition in the vessel 7 and the cavity 4 is formed. At the time of starting pouring of the molten metal from a sprue cup 8, cellophane tape 9 for shutting off the inner part of the vessel 7 from the air is melted and lost, and the molten metal is caused to flow into the cavity 4. A pump 12 continues to work so that the molten metal equally runs at every corners in the cavity 4. By this method, a casting product without any casting defect can be manufactured.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a suction casting method that can prevent underfilling due to poor hot water circulation that tends to occur in thin-walled parts of cast products in casting using shell molds. It is related to.

[Conventional technology]

Conventionally, we have focused on the advantages of shell mold casting, such as high dimensional accuracy, good ventilation, and excellent mass production. Manufactured by casting.

By the way, in order to reduce the weight of engines, attempts have been made to reduce the wall thickness of the rotor. The molten metal was not sufficiently circulated to the forming part, resulting in the inconvenience of insufficient thickness in such thin parts of the rotor, which was a molded product.

A suction casting method has been proposed as a casting method to solve such inconveniences, for example, in JP-A-61-7476.
Japanese Patent No. 5 proposes a method of injecting molten metal into a cavity while drawing reduced pressure from around an air-permeable sintered mold to improve the flow of the molten metal. According to this method, a negative pressure state is created equally around the entire periphery of the sintering mold, so negative pressure is applied to areas where the metal circulation is good and areas where it is not good in the cavity. .

[Problem to be solved by the invention]

However, with the above conventional method, inefficient casting is performed in which the negative pressure caused by suction is distributed all over the periphery of the mold, and the effect of negative pressure is not sufficiently applied to the areas where improvement in the circulation of the metal is required. Therefore, it is not possible to reliably prevent poor water circulation in such areas. Furthermore, in order to apply sufficient negative pressure to such a region, it becomes necessary to increase the suction force in the negative pressure generating device.

In addition, applying negative pressure uniformly to areas with good hot water circulation and areas with bad water circulation improves hot water circulation in both areas, but it also has the disadvantage that differences in hot water circulation still remain between the two parts. be.

[Means to solve the problem]

In order to solve the above-mentioned problems, the suction casting method using a shell mold according to the present invention has a highly air permeable region formed in the shell mold itself in the vicinity of a portion where poor circulation is likely to occur in the cavity of the shell mold. The feature is that the molten metal is injected into the cavity while intensively suctioning and depressurizing the metal through the cavity.

[For production]

According to the above configuration, suction and pressure reduction is performed intensively in the vicinity of areas where poor water circulation is likely to occur, so negative pressure can be efficiently and sufficiently applied to areas where poor water circulation is likely to occur. .

Due to this concentrated generation of negative pressure, the molten metal is smoothly guided to areas where the hot water circulation is not good. In other words, by improving the areas in the cavity where hot water circulation is not good, the hot water circulation will be uniformly good throughout the cavity, and the hot water will be equally distributed to thin-walled areas within the cavity. .

Moreover, since suction and pressure reduction is performed through the highly air permeable region formed in the shell mold itself, more efficient suction and pressure reduction can be performed on areas where hot water circulation problems are likely to occur.

[Example 1] An example of the present invention will be described below based on FIGS. 1 and 2.

In the suction casting method using a shell mold according to the present invention,
As shown in FIGS. 1(a) and 1(b), a shell mold 1 for a rotor consists of a main mold 2 and a core 3.
By stacking three molds that can be individually molded, it is possible to obtain six rotors in one casting. shell mold 1
Inside the cylindrical part 1a protruding from the upper part of the main mold 2 and the core 3
・A channel 5 for guiding the molten metal into the cavity 4 formed between the core 3 and the core 3 is formed, and a sprue 6 formed at the tip of the channel 5 is connected to the container. It is formed to match the hole 7b formed in the upper lid 7a of No.7. A sprue cup 8 is disposed on the top lid 7a to match the hole 7b, and a cellophane pad is placed between the sprue cup 8 and the top lid 7a to isolate the inside of the container 7 from the atmosphere before pouring. A tape 9 is interposed. Also, container 7
A gasket 10 is interposed between the main body of the container 7 and the upper lid 7a to seal the inside from the atmosphere.

As shown in FIG. 2, each core 3 consists of a main core and a lower core, and a ventilation hole 3a penetrating vertically is formed approximately in the center of the core 3. The vent hole 3a is connected to a water ring vacuum pump 12 via an intake pipe 11. The suction ports 11a and lla of the intake pipe 11 are formed with positioning claws 16 and 16 that fit into the lower end of the ventilation hole 3a, so positioning claws 16 and 16 are formed in the suction ports 11a and lla of the intake pipe 11, so that positioning claws 16 and 16 that fit into the lower end of the ventilation hole 3a are used for positioning the ventilation hole 3i and the intake pipe 11. The structure eliminates the need for separate bins.

A highly air permeable region is formed by interposing a porous filter 17 between the above-mentioned ventilation hole 3a in each core 3 and a region in the cavity 4 where poor water circulation is likely to occur. As the porous filter 17, for example, 50
Cordierite with a mesh roughness of ~70 mesh is used. Cordierite is Mg0-Aj! z Ox
-3tOz ternary compound, theoretical set 4 is MgO
is 13.7%, A2□0. is 34.9%, Stow is 5
It accounts for 1.4%. In addition, the porosity is 12
．． 5%, compressive strength 20.9kgf 71m”, J
I 5(7)4 PNT 4-point bending strength is 7.50 k
g f /m", Young's modulus is 7.75 x 10'
kg f/lram", thermal expansion coefficient: 1.45
It has a characteristic of 10-'/''C (40 to 600°C).

Further, the container 7 is filled with steel shot 14 having a grain size of about 1 to 5 ffi11, and the shell mold 1 is backed up by the steel shot 14.

The process of suction casting using the shell mold 1 described above will be explained as follows.

Before pouring the molten metal, the water ring type vacuum pump 12 is operated to suck air in the vent hole 3a using the suction pressure car 400-8g. Of course, due to this suction, the air inside the cavity 4 is sucked through the porous filter 17, and the air inside the container 7 is suctioned by the air permeability of the shell mold 1, and the pressure inside the container 7 and the cavity 4 is also reduced. A negative pressure condition will be created. Incidentally, since the inside of the container 7 is isolated from the atmosphere by the packing 10 and the cellophane tape 9, the negative pressure state inside the container 7 is maintained.

After this, the molten metal (in this example, FCD 7
0)). By this injection, the cellophane tape 9 melts and disappears, and the molten metal smoothly flows into the cavity 4 through the groove 5. Even during such injection, and even while the molten metal is circulating inside the cavity 4, the water ring vacuum pump 12 continues to operate and continues to suck the air inside the container 7 and the cavity 4.

Here, the air inside the cavity 4 is filtered through the porous filter 17.
This intensive suction causes a negative pressure state to be created in the vicinity of areas where hot water circulation is likely to occur. In other words, it is possible to apply negative pressure efficiently (and sufficiently) to the area.

By applying such concentrated negative pressure, the molten metal is smoothly guided even to areas where the hot water circulation is not good. In other words, by improving the parts of the cavity 4 where the hot water circulation is not good, the hot water circulation will be improved evenly throughout the cavity 4, so that the hot water will circulate equally to every corner of the cavity 4. become. Thereby, it is possible to reliably prevent casting defects such as underfilling from occurring in the cast product.

In addition, since suction and pressure reduction is performed through the ventilation holes 3a formed in the shell mold 1 itself and the highly air permeable area formed by the porous filter 17, extremely efficient suction and pressure reduction can be applied to areas that are prone to poor water circulation. It can be performed.

[Embodiment 2] Another embodiment of the present invention will be described below with reference to FIG. Note that members having the same functions as those used in the above embodiments will be given the same reference numerals and their explanations will be omitted.

As shown in FIGS. 3(a) and 3(b), the main mold 2 has three cassette shell plates 18 facing the cavity 4 so as to surround each core 3. It is detachably attached to the Then, a cassette shell plate 18 located near a portion of the cavity 4 where poor water circulation is likely to occur.
a is also arranged facing the space inside the container 7, and a highly air permeable region is formed by this cassette shell plate 18a. That is, the main mold 20 body part and the cassette shell plate 18b
- While the cassette shell plate 18b is formed with a roughness of, for example, 100 to 120 meshes, the cassette shell plate 18a is formed with a roughness of, for example, 50 to 60 meshes, and the air permeability is increased by the coarseness. There is.

The shell mold 1 is backed up with steel shot 14 filled in the container 7, and the water ring vacuum pump 12 is communicated with the container 7 via an intake pipe 11, and the air inside the container 7 is It is designed to attract.

By operating the vacuum pump 12 in the same manner as described above using such casting means, the air in the portions of the cavity 4 where poor water circulation tends to occur is removed from the cassette shell plates 18a and 18a.
It is possible to efficiently apply negative pressure to areas in the cavity 4 where hot water circulation is likely to occur, improve hot water circulation in such areas, and prevent underfilling in cast products. can.

Note that, like the shell mold 1 used in this example, the main mold 2
The cassette shell plate 18 is removably attached to the main body of the cassette shell plate 18.
By providing the . . . , the setting of the core 3 can be easily performed.

It is also possible to perform such a suction casting method in a shell mold 1 that does not use a cassette shell plate, for example,
By applying a coating that slightly reduces air permeability while leaving the outer circumferential surface of the main mold 2 corresponding to areas where poor water circulation tends to occur, the shell mold itself can be coated with high heat in areas where poor water circulation tends to occur. A breathable region can be formed, and suction and depressurization can be performed intensively through such a highly breathable region.

〔Effect of the invention〕

As described above, the suction casting method using a shell mold according to the present invention concentrates the concentration by passing through the highly air permeable region formed in the shell mold itself in the vicinity of the part where poor circulation is likely to occur in the cavity of the shell mold. The structure is such that the molten metal is injected into the cavity while being vacuumed and depressurized.

This has the effect of reliably preventing underfilling due to poor hot water circulation that tends to occur in thin-walled parts of cast products.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention. FIG. 1(a) is a longitudinal cross-sectional view showing a casting means for implementing the suction casting method, and FIG. 1(b) is a cross-sectional view thereof. FIG. 2 is an enlarged longitudinal sectional view of the main parts of the core. FIG. 3 shows another embodiment of the present invention, in which FIG. 3(a) is a longitudinal cross-sectional view showing a casting means for carrying out the suction casting method, and FIG. 3(b) is a cross-sectional view of the same. It is. 1 is a shell mold, 2 is a main mold, 3 is a core, 3a is a ventilation hole,
4 is a cavity, 7 is a container, 11 is an intake pipe, 12 is a water ring vacuum pump, 14 is a steel shigot, 16 is a positioning claw, 17 is a porous filter (highly air permeable area), 18
a is a cassette shell plate (highly air permeable area). Patent applicant Mazda Co., Ltd. 2m! 1 1A Figure 3(b)

Claims (1)

[Claims] 1. Injecting the molten metal into the cavity while intensively suctioning and depressurizing it through a highly air permeable area formed in the shell mold itself in the vicinity of the part of the shell mold that is prone to poor circulation. A suction casting method using a shell mold characterized by: