JPH06226423A - Manufacture of thin cast product by permeable mold - Google Patents

Abstract

PURPOSE:To manufacture a thin cast product without casting defect of misrun, blow hole, etc., by making the pressure to be reduced in a cavity at a pressure reducing suction side larger than the pressure to be reduced in a cavity at sprue side. CONSTITUTION:A feed head 9 and/or a run-off part are arranged neat the last filling part of molten metal 3 in a cavity 2 for product in a permeable mold 1. At least one or more of the pressure reducing suction holes 11 are arranged near the feeder head 9 and/or the run-off part in the mold 1. Interval between the pressure reducing suction hole 11 and at least one or more of the feeder head and/or the run-off part and hollow core 8 print is connected with a suction member 10 having the permeability higher than the permeable mold 1. In such a way, the pressure to be reduced in the cavity 2 at the pressure reducing suction side is made larger than the pressure to be reduced in the cavity at the sprue side. By this method, without disturbing the flow of molten metal, the fluidity of molten metal is improved and the generating gas at the time of pouring the molten metal can effectively be removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for producing thin-walled castings, and is particularly suitable for producing cast-iron castings with high productivity such as thin-walled stainless steel castings and heat-resistant cast steel castings that do not suffer from casting defects such as blowholes. Regarding the method.

[0002]

2. Description of the Related Art In a thin casting having a wall thickness of 5 mm or less, solidification proceeds rapidly after the molten metal is poured and comes into contact with a mold. For this reason, the fluidity of the molten metal deteriorates, and non-rotating defects and the like are likely to occur.

Further, in a thin-walled casting having a complicated shape, during casting, air or gas generated from the mold is easily entrained in the molten metal, gas defects such as blowholes are easily generated in the casting after solidification, and casting is sound. It is extremely difficult to do.

As a general method for solving this, there is a lost wax casting method. This lost wax casting method uses a ceramic mold, and the mold is 700 ° C during casting.
By heating to ~ 900 ° C, the cooling rate of the molten metal at the time of filling is slowed and the fluidity of the molten metal is improved. However, since the expensive ceramic mold is used, the manufacturing cost of the casting is considerably high.

In order to improve the fluidity of the molten metal, a pressure reducing casting method "CLAS method" for suction casting the molten metal by depressurizing the cavity in the mold is disclosed in Japanese Examined Patent Publication No. S60-35227.
There is a disclosure in Japanese Patent Laid-Open Publication No. 2003-242242, and it has been recently used as a casting method for a thin casting.

Further, as a reduced pressure casting method in which the inside of a chamber containing a breathable mold is sucked under reduced pressure and molten metal is injected,
There is a disclosure in Japanese Patent Laid-Open No. 61-180642.

Further, in Japanese Patent Laid-Open No. 57-31463, the molten metal is injected into the product cavity while sucking the inside of the product cavity of the mold through a ventilation hole provided at a position farthest from the sprue position in the product cavity. However, there is a disclosure of casting a thin casting by improving the fluidity of the molten metal. In this Japanese Patent Laid-Open No. 57-31463, since the entire inner surface of the product cavity is sucked, the effect of sucking a necessary portion is small,
Further, the molten metal is disturbed in the product cavity, and casting defects due to the inclusion of air, slag, or ladle are likely to occur.

As a measure against this, Japanese Patent Laid-Open No. Sho 60-
In Japanese Patent No. 56439, a refractory material filter having better air permeability than gypsum is provided from the vicinity of the final filling portion of the molten metal in the product cavity to the outer surface of the gypsum mold to enhance the decompression effect of the product cavity and perform suction casting. Due to
There is a disclosure of a gypsum mold for reduced pressure casting that obtains a thin-walled casting that has no non-rotating defects and has no gas defects caused by entrainment of air.

Further, in Japanese Patent Laid-Open No. 4-147760, a suction guide is provided between the required portion of the mold space and the outside of the mold to locally reduce the pressure of the depressurized portion and suck it. There is a disclosure of a sand casting mold for suction casting that enhances the effect and that the gas generated at the time of pouring is naturally exhausted to the outside of the mold without being affected by the suction to cast a thin casting without gas defects. .

[0010]

However, in Japanese Patent Publication No. 60-35227, the structure for holding and immersing the mold for immersing the mold in the molten metal becomes complicated.

Further, according to Japanese Patent Laid-Open No. 61-180642, since the entire mold is sucked, the flow of the molten metal is easily disturbed, blowhole defects and the like are likely to occur, and there is a risk of explosion of the gas generated from the mold.

Further, Japanese Patent Laid-Open No. 60-56439 discloses
Since gypsum is used as the mold, many steps are required to manufacture the gypsum mold, resulting in poor productivity. Further, since the gypsum mold itself has poor air permeability, the pressure (back pressure) in the cavity becomes large during casting, and the flowability of molten metal is poor as a whole.

Japanese Patent Laid-Open No. 4-147760 discloses
It requires a process to provide a suction guide that forms a suction passage in the sand mold, productivity is still insufficient, suction is local, and the air permeability of the suction passage is not so large compared to the sand mold. The effect is small.

It is an object of the present invention to provide a manufacturing method most suitable for manufacturing a thin casting free from casting defects such as non-rotation and blowholes, with high productivity, safety and low cost.

[0015]

In order to achieve the above-mentioned object, a method for producing a thin wall casting according to the present invention comprises a presser and / or a presser near the final filling portion of the melt in a product cavity of a breathable mold having a core. A skein is provided and the feeder and / or
Alternatively, at least one vacuum suction port is provided in the breathable mold in the vicinity of the skein, and the vacuum suction port and at least one of the feeder and / or the spout and the hollow core skirting board are provided. By connecting the spaces with a suction member having a gas permeability higher than that of the gas permeable mold, the pressure reduction inside the vacuum suction port side cavity is made larger than that inside the gate side cavity.

In the present invention, the thin casting is at least 5
It is a casting having a thin portion of not more than mm. Further, in the present invention, the suction member refers to a ceramic filter, a sand mold using sand having a grain size coarser than that of the main mold, and a breathable member such as a vent hole through which molten metal does not penetrate.

[0017]

With the above structure, the decompression in the depressurization suction port side cavity is made larger than that in the sprue side cavity to secure and improve the fluidity of the molten metal without disturbing the flow of the molten metal.
By providing the vacuum suction port in the breathable mold, the ventilation around the vacuum suction port is secured, and the gas generated during pouring is effectively removed.

Further, when the breathable mold is at a predetermined position by a conveying device (not shown), the suction means decompresses and suctions from the decompression suction port which is opened to the outer surface of the breathable mold and connected from the suction member to the decompression device. .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a thin cast product according to the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a vertical cross-sectional view of a breathable mold used in the present invention, and FIG. 2 is an enlarged sketch of an essential part of FIG. 1 and 2, the breathable mold 1 has a hollow core 8 having an outer diameter of 45 mm, a thickness of 2.0 mm, and a length of 200.
mm hollow cylinder cavity 2 and outer diameter 80 at both ends
mm and a thickness of 10 mm, and two bosses having a diameter of 10 mm and a height of 15 mm are formed on the outer peripheral surface of the cavity 2. The breathable mold 1 is a cold box type and uses silica sand No. 7. The sprue 5 is provided near one end of the breathable mold 1, and a filter 6 and a weir portion 7 are provided continuously to the sprue 5 at the bottom of the sprue. A riser 9 is also provided on the opposite side of the sprue 5 as a spout. And
A pressure reducing suction port 11 that opens toward the bottom of the breathable mold 1 is provided near the vase-use dual-purpose feeder 9, and the breathability is provided between the vase-use dual-purpose feeder 9 and the hollow core 8 and the pressure reducing suction port 11. Mold 1
A suction member 10 having a higher air permeability (No. 5 sand layer in this embodiment) is provided. The tip of the flexible tube is brought into close contact with the opening of the vacuum suction port 11 from the vacuum device 12 to perform vacuum suction. In Example 1, the relationship between the pressure (mmHg) of the cavity portion in the mold, the gate side and the suction side and the amount of molten metal injected into the cavity was examined with the passage of time. FIG. 3A shows a constant pressure reduction, and FIG. 3B shows a pressure reduction control. For comparison, the decompression pattern of constant decompression when the core was not hollowed out was also examined and shown in FIG. Table 1 shows the chemical composition of the cast steel.

[0021]

【table 1】 After casting, the breathable mold 1 is carried out on the roller conveyor to the next demolding station by an extrusion device. Then, the breathable mold 1 before casting is carried into the pouring station. The above steps are repeated to cast the required number of thin wall castings.

Thirty cylindrical thin-walled cast steel castings with flanges were cast by the above-described method according to the depressurization pattern of the embodiment shown in FIG. 3 and the depressurization pattern of the comparative example shown in FIG. As a result, FIG. 3 (a) and FIG.
In (b), the decompression value in the decompression suction port side cavity is larger than that in the sprue side cavity, the molten metal injection speed is high, the molten metal is not easily disturbed, and the entrainment of air is small.
There were no casting defects such as non-rotating defects, leak defects, air entrapment, blow holes, etc. On the other hand, FIG.
In comparison, the injection speed of the molten metal was slower than that in FIGS. 3 (a) and 3 (b), and 18 pieces did not rotate.

(Embodiment 2) FIG. 5 is a horizontal sectional view of a breathable mold showing another embodiment of the present invention. In FIG. 5, the breathable mold 1 has a hollow core 8 having an outer diameter of 40 mm and a thickness of 2.
3 mm branched pipe, 10 mm thick flanges on both ends, and 10 mm diameter and 15 height on the outer peripheral surface of the pipe.
5 mm bosses are formed. The breathable mold 1 is a cold box type and uses silica sand No. 6. Sprue 5
Is provided near one end of the breathable mold 1 and is continuous with the sprue 5,
The bottom of the sprue, the filter 6, and the weir are provided. A riser 9 is also provided on the opposite side of the sprue 5 as a spout. A pressure reducing suction port 11 opened toward the bottom of the breathable mold 1 is provided in the vicinity of the vase-use dual-purpose feeder 9, and air permeability is provided between the vase-use dual-purpose feeder 9 and the hollow core 8 and the pressure reducing suction port 11. A suction member 10 having a larger air permeability than the mold 1 (4 in this embodiment)
No. sand layer). The tip of the flexible tube from the decompression device is brought into close contact with the opening of the decompression suction port 11 to perform decompression suction. The depressurization is the same as shown in FIG.
The constant depressurization similar to (a) is performed. Table 2 shows the chemical composition of the cast steel.

[0024]

[Table 2] After casting, the breathable mold 1 is carried out on the roller conveyor to the next demolding station by an extrusion device. Then, the breathable mold 1 before casting is carried into the pouring station. The above steps are repeated to cast the required number of thin wall castings.

When 50 thin-walled cast steel castings of branched pipes were cast by the above-mentioned method, the reduced pressure value in the cavity on the reduced pressure suction port side was larger than that in the cavity on the sprue side, the injection speed of the molten metal was faster, and the molten metal was faster. Was not disturbed, there was little air entrapment, and there were no casting defects such as total defects, non-rotation defects, leak defects, air entrapment, and blowholes.

[0026]

As described above, according to the method for producing a thin cast product by the air-permeable mold of the present invention, the fluidity of the molten metal is improved without disturbing the flow of the molten metal, and the gas generated during pouring is effective. Therefore, it is possible to manufacture a thin-walled cast product without casting defects such as non-rotation and blowholes. Further, since a vacuum suction port is provided in a normal air-permeable mold and mass production can be performed using a carrier device or the like, productivity is improved. In addition, there is no danger of explosion because no box or chamber containing a mold is used.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a method for producing a thin cast product using a breathable mold according to the present invention.

FIG. 2 is an enlarged schematic view of an essential part of FIG.

FIG. 3 is a graph showing the relationship between the change in pressure of each part and the amount of molten metal injected in an embodiment of the method for producing a thin cast product using a breathable mold according to the present invention.

FIG. 4 is a graph showing the relationship between the change in pressure of each part and the amount of poured molten metal in a comparative example.

FIG. 5 is a horizontal cross-sectional view of the breathable mold of another embodiment of the method for producing a thin cast product using the breathable mold of the present invention.

[Explanation of symbols]

1 breathable mold, 2 cavities, 3
Molten metal, 4 ladle, 5 sprue,
6 filters, 7 weirs, 8
Hollow core, 9 feeder, 10 suction member,
11 decompression suction port, 12 decompression device

Claims (1)

[Claims] 1. A method of casting a thin-walled casting having a core by means of a breathable mold, wherein a riser and / or a skein is provided in the product cavity of the breathable mold in the vicinity of the final filling portion of the melt, and the riser and / or Alternatively, at least one vacuum suction port is provided in the breathable mold in the vicinity of the skein,
By connecting the reduced pressure suction port and at least one of the feeder and / or the skein and the hollow core skirting with a suction member having a higher air permeability than the breathable mold, the reduced pressure suction port side A method for producing a thin-walled casting by a gas permeable mold, characterized in that the pressure reduction in the cavity is made larger than that in the gate side cavity.