JPH0783923B2 - Suction casting method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a suction casting method and apparatus for suction-filling a molten metal into a product cavity by decompressing the inside of the product cavity of a mold partially cooled and made of gold. Regarding

[Conventional technology]

The suction casting method is used when casting a high-quality casting, because it has advantages such as good hot water flow and less inclusion or inclusion of bubbles. Conventionally, for example, a casting apparatus as disclosed in Japanese Patent Publication No. 59-14306 has been used. Fifth
As shown in the figure, in this suction casting apparatus 100, a cooling metal 108 is arranged on the upper surface of a cavity 106 of a gypsum mold 104 whose outer peripheral portion is covered with an iron casting frame 102, and the periphery thereof is covered with a chamber 110. The inside of the chamber 110 is decompressed by the vacuum pump 120. A spring 112 is arranged between the inner surface of the chamber 110 and the chill 108, and the chill 108 and the gypsum mold 10 are provided.
The contact surface 114 with 4 is pressed. At this time, gypsum mold 10
Since the sprue 116 at the lower part of 4 is covered with the Al foil 118, the product cavity 106 is depressurized via the contact surface 114 as the chamber 110 is depressurized. And product cavity 1
After the pressure inside 06 is reduced to a predetermined pressure, the sprue 116 is immersed in the container containing the molten metal. Then, the Al foil 118 covering the gate 116 is melted, and the product cavity 106 is depressurized.
The molten metal is sucked up into the product cavity 106 through the sprue 116 based on the pressure difference between the pressure of the molten metal and the atmospheric pressure applied to the molten metal in the container. The molten metal sucked into the product cavity 106 is
Upon solidification, directional solidification occurs from the portion in contact with the chill 108. After the molten metal is solidified, the mold 104 is separated to complete the casting.

[Problems to be solved by the invention]

According to such a conventional suction casting method, between the chill and the gypsum mold, the chill is only pressed by the spring from the back surface of the chill, so that the pressing force is not constant and the pressure inside the cavity is reduced. The degree was unstable. Therefore, the suction speed of the molten metal sucked from the stalk into the cavity is not constant,
The suction speed varied, and inclusions, bubbles, etc., and defective running of the water sometimes occurred.

Therefore, an object of the first invention is to provide a casting method for producing a cast product having no casting defects by controlling the suction speed within an optimum range. Another object of the second invention is to provide a casting apparatus for realizing the casting method of the first invention.

[Means for solving problems]

Therefore, the suction casting method of the first aspect of the present invention is characterized by controlling the pressing force of the cooling die to the mold according to the degree of pressure reduction in the product cavity.

Specifically, the configuration of the present invention is as follows. For reference, the reference numerals in FIG. 1 are attached.

The first aspect of the present invention is a suction for decompressing the inside of the product cavity (24) of a mold (18) partially cooled and composed of gold (28) to suck and fill the molten metal (12) into the product cavity (24). It is a casting method.

Then, the pressure is reduced mainly through the gap (50) between the contact surfaces between the chill (28) and the mold (18), and the pressure applied between the contact surfaces is controlled according to the degree of pressure reduction to achieve a predetermined casting speed. Is what you get.

On the other hand, the suction casting apparatus according to the second aspect of the present invention is characterized by measuring the back pressure in the pressure reducing means and controlling the pressure applied to the contact surface between the chill and the mold based on the back pressure.

A second aspect of the present invention is a casting apparatus (in which a molten metal (12) is partially cooled from a molten metal storage container (14) and suction-filled into a product cavity (24) of a mold (18) made of gold (28) ( 10).

And a chamber (30) covering the mold (18) and the chill (28), and a decompression means (44) in the chamber (30),
The pressing means (36) for pressing the cold metal (28) to the mold (18) in the chamber (30), the means (42, 48) for detecting the back pressure of the pressure reducing means (44), and the back pressure. Based on the pressing means (3
6) Control means for controlling the pressing force.

[Action]

According to the suction casting method of the first invention described above, the clearance (50) of the contact surface between the chill (28) and the mold (18) is controlled based on the degree of pressure reduction in the product cavity (24). The filling speed of the molten metal (12) into the product cavity (24) can be controlled within an appropriate range corresponding to the degree of pressure reduction.

According to the suction casting apparatus (10) of the present second invention described above, the degree of pressure reduction in the product cavity (24) that is approximately proportional to the back pressure is measured based on the measurement result of the back pressure in the pressure reducing means (44). be able to. By controlling the pressing force of the chill based on this back pressure, the suction speed can be controlled within the optimum range.

〔Example〕

Next, an embodiment of a suction casting method and apparatus according to the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a vertical cross-sectional view of the suction casting apparatus according to this embodiment, FIG. 2 is a view showing a contact surface between the chill and the mold 18 in FIG. 1, and FIG. 3 is a drawing showing casting speed and exhaust system back pressure. FIG. 4 is a graph showing the relationship, and FIG. 4 is a graph showing the relationship between the pressing force of the chill and the back pressure.

In FIG. 1, reference numeral 10 is a suction casting apparatus used in the suction casting method in this embodiment. This suction casting equipment
In 10, a gypsum mold 18 housed in an iron casting frame 16 is arranged above a molten metal storage container 14 that houses the molten metal 12. A stalk 20 is formed below the mold 18, and the stalk 20 communicates with the product cavity 24 through the spout 22. The product cavity 24 is open at the top, and a chill 28 is placed in the opening 26. Also, the mold 18
Above the above, a chamber 30 is arranged so as to cover the mold 18 and the chill 28, and the flange portion 30a of the chamber 30 is
An O-ring 52 is arranged in contact with the flange portion 16a of the casting frame 16. The support portion 32a of the clamp jig 32 is located at the lower end of the flange portion 16a of the casting frame 16 to support the casting frame. A pressing rod 34 is in contact with the upper surface of the chill 28, and the pressing rod 34 is connected to a hydraulic cylinder 36. Therefore, by operating the hydraulic cylinder 36, a predetermined pressure is applied to the chill 28 to pressurize the contact surface between the chill 28 and the mold 18 to adjust the gap 50. The pressing rod 34 is slidably sealed by an O-ring 38 attached to the chamber 30. Also,
A decompression port 40 is formed in the chamber 30, and the decompression port 40 is connected to a vacuum pump 44 via a flow control valve 42 by a pipe line 46. A pressure gauge 48 is attached to the pipe 46 on the pressure reducing port 40 side of the flow control valve 42.

Next, a suction casting method using this suction casting device 10 will be described.

First, the flow rate control valve 42 is adjusted to a predetermined flow rate. Next, the hydraulic cylinder 36 is operated, and a predetermined pressing force of the cooling plate 28 is applied via the pressing rod 34. In that state, the vacuum pump 44 is driven to drive the vacuum from the pressure reducing port 40 to the chamber 30.
Decompress the inside. As the pressure in the chamber 30 is reduced, the mold 18
The product cavity through the gap 50 on the contact surface between
The inside of 24 is decompressed. At this time, the sprue 22 is open to the atmosphere. Then, when the pressure gauge 48 shows a predetermined value,
The clamp jig 32 is lowered to immerse the sprue 22 of the mold 18 in the molten metal 12. Then, the molten metal 12 is sucked into the product cavity 24 via the spout 22 and the stalk 20 due to the differential pressure between the reduced pressure in the product cavity 24 and the pressure on the atmospheric surface of the molten metal 12 contained in the container 14. Sucked molten metal
The product 12 is filled in the product cavity 24, and the directional solidification occurs from the side of the cooling gold 28 to complete the casting.

The suction speed of the molten metal 12 into the product cavity 24 described above corresponds to the degree of pressure reduction in the product cavity 24. The degree of pressure reduction in the product cavity 24 is determined by the flow rate of air passing through the gap 50 between the chill 28 and the mold 18. That is, assuming that the exhaust capacity of the vacuum pump 44 is constant, when the pressing force of the hydraulic cylinder 36 is large and the gap 50 is small,
The ventilation resistance is large and the flow rate of air passing through the gap 50 is small. On the contrary, the pressing force of the hydraulic cylinder 36 is small and the clearance
When 50 is large, the ventilation resistance is small and the flow rate of air passing through the gap 50 is large. Further, when the area of the gap 50 (shown in FIG. 2) is large, the ventilation resistance is large, and when the area is small, the ventilation resistance is small.

Therefore, in this embodiment, the degree of pressure reduction in the product cavity 24 is determined by controlling the pressing force of the hydraulic cylinder 36 that determines the area of the gap 50 and the size of the gap. Specifically, the minimum contact area of the gap 50 corresponding to the maximum pressing force of the hydraulic cylinder 36 is set, and the gap 50 corresponding to the minimum pressing force of the hydraulic cylinder 36 is set.
Of the chill 28 and the product cavity 24 of the mold 18 so that the chill 28 and the mold 18 contact each other between the maximum and minimum values of these contact areas. The inner diameter d of the opening 26 was determined (shown in FIG. 2). Specifically, D = 110 to 130 mm and d = 60 to 80 mm.

Further, in the present embodiment, the optimum range of the amount of the clearance 50 adjusted by the hydraulic cylinder 36 is determined by measuring the back pressure on the pressure reducing port 40 side of the flow control valve 42 of the pipeline 46 with the pressure gauge 48. There is. This is because there is an appropriate range (a in the figure) for the suction speed of the molten metal 12 sucked into the product cavity 24, and the vacuum pump 44 corresponding to the proper range a of the suction speed is The exhaust system back pressure also has an optimum range (Fig. B). The exhaust system back pressure and the hydraulic cylinder 36 have a relationship as shown in FIG. 4, and the hydraulic cylinder 36 has a back pressure range b corresponding to an appropriate pressing force range (FIG. C). An appropriate molten metal suction speed can be obtained by controlling the pressing force of. Note that the relationship shown in FIG. 3 is obtained by conducting an experiment using the above-mentioned casting apparatus in which the height from the sprue 22 to the chill 28 is 100 mm and using an AC4C equivalent aluminum melt in JIS standard. Is.

In FIG. 3, when the back pressure is greater than -300 mmHg, the suction speed increases and inclusions and bubbles are entrained. Also, if the back pressure is less than -500 mmHg, the suction speed will be low, and problems such as poor bathing will occur. Therefore, −300 to −5
It can be seen that the back pressure in the range of 00 mmHg is appropriate. In addition,
As the vacuum pump 44 in this embodiment, a pump having a capacity larger than the maximum value of the appropriate back pressure, −300 mmHg, is used.

In the embodiment described above, in the exhaust system outside the chamber 30, the back pressure of the vacuum pump 44 is measured by the pressure gauge 48, and the hydraulic cylinder 36 is operated so that the back pressure falls within the appropriate range. Since the pressing force of the gap 50 between the molds 18 is adjusted, suction casting is carried out at an appropriate casting speed, and entrainment of bubbles and casting defects such as defective molten metal rotation do not occur.

Although the specific embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various embodiments are included within the scope of the claims. .

In the above-described embodiment, the back pressure of the exhaust system is measured, and the pressing force of the hydraulic cylinder 36 is adjusted so that the back pressure falls within the proper range, but it corresponds to the median value of the proper back pressure range in advance. Set the hydraulic cylinder 36 so that it will have a pressing force,
If the measurement result of the pressure gauge 48 indicates that the back pressure is in the proper range, the casting may be started as it is, and if it is outside the proper range, the casting may be stopped. In this case, there is an advantage that the control circuit of the hydraulic cylinder 36 is simplified.

〔The invention's effect〕

As described above, according to the suction casting method of the first aspect of the present invention, the suction speed is controlled within the optimum range by controlling the contact surface between the chill and the mold, and a good cast product without casting defects can be manufactured. it can.

Further, according to the suction casting apparatus of the second invention, by providing the means for measuring the back pressure in the depressurizing means, the suction casting method of the first invention can be realized without complicating the process. it can.

[Brief description of drawings]

1 to 4 are drawings for explaining an embodiment of a suction casting method and apparatus according to the present invention. FIG. 1 is a vertical sectional view of the suction casting apparatus in this embodiment. FIG. 2 is a view showing a contact surface between the chill plate and the mold 18 in FIG. FIG. 3 is a graph showing the relationship between the casting speed and the exhaust system back pressure. FIG. 4 is a graph showing the relationship between the pressing force of the chill and the back pressure. FIG. 5 is a drawing for explaining a conventional technique and is a cross-sectional view showing a part of a casting device. 10 …… Suction casting equipment 12 …… Molten metal 14 …… Molten storage container 18 …… Mold 24 …… Product cavity 28 …… Cold money 30 …… Chamber 36 …… Pressing means (hydraulic cylinder) 42 …… Back pressure Detecting means (flow control valve) 44 …… Decompression means (vacuum pump) 48 …… Back pressure detecting means (pressure gauge)

Claims (2)

[Claims] 1. A suction casting method for depressurizing the inside of a product cavity of a mold, which is partially made of chill, to suck and fill molten metal into the product cavity, which mainly comprises a contact surface between the chill and the mold. A suction casting method characterized in that a predetermined casting speed is obtained by performing pressure reduction through a gap and controlling the pressure applied between the contact surfaces according to the degree of pressure reduction. 2. A casting apparatus for sucking and filling a molten metal from a molten metal storage container into a product cavity of a mold, a part of which is cooled, and a chamber for covering the mold and the chill, and decompression in the chamber. Means, pressing means for pressing the chill in the chamber against the mold, means for detecting the back pressure of the pressure reducing means, and control means for controlling the pressing force of the pressing means based on the back pressure. Characteristic suction casting equipment.