JP2560356B2 - Vacuum suction precision casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an improvement of a vacuum suction precision casting method known as one of precision casting methods.

[Prior Art] The vacuum suction precision casting method was developed by Hitchiner Co., Ltd., a major American lost wax maker, as disclosed in Japanese Patent Publication No. 52-38924. First, the vacuum suction precision casting method will be briefly described with reference to FIGS. 3a to 3d. In FIG. 3a, reference numeral 100 is a molten metal tank, 101 is a chamber supported above the metal molten metal tank, and 103 is a mold made by firing foundry sand. The mold 103 has a molten metal suction pipe 104 integrally formed at one end thereof, and an expanded diameter portion 105 is formed at the base of the molten metal suction pipe 104. In this case, the tip of the suction pipe 104 beyond the bulging portion 105 is projected downward from the bottom opening 106 of the chamber 101 and set inside the chamber 101. Then, as shown in FIG. 3b, the chamber 101 is lowered to immerse the tip of the suction pipe 104 in the molten metal, while the suction port 107 is connected to the vacuum pump, thereby
Decompress the inside. Then, since the mold 103 is made into a breathable hollow shell shape, the inside is depressurized and the molten metal is sucked from the suction pipe 104 to fill the inside of the mold with the molten metal. So 3c
As shown in the figure, the chamber 101 is raised to release the depressurized state when the molten metal in the product portion is solidified, so that only the unsolidified molten metal in the runner of the mold is made to flow out to make the molten metal portion hollow. If this mold 103 is taken out and sanded, the product 108 can be taken out as shown in FIG. 3d.

However, in this vacuum suction precision casting method, the molten metal that has entered the runner is returned to the hot water tank and sucked into the next mold after the molten metal is directly sucked in the mold under reduced pressure, so the casting yield is 70% or more. It is expected that the yield will be significantly improved compared to around 25 to 35% of the top pouring method that uses a normal ladle, and that the molten metal is directly sucked under reduced pressure by the mold, so that the molten metal is well circulated and complicated shapes and There are various advantages such as that ultra-thin products can be integrally cast, and the quality of the molten metal is improved without contamination.

[Problems of the Prior Art] However, the conventional vacuum suction precision casting method was suitable for casting small articles, but was unsuitable for casting large products for the following reasons. That is, if the volume of the product molding portion of the mold is large, there is a problem that it takes time for the molten metal filled in the product molding portion to solidify and productivity is deteriorated.

[Means for Solving Problems] Therefore, the present invention intends to improve the above-mentioned vacuum suction precision casting method to improve its technical superiority even for a large casting. In order to achieve the object, the vacuum suction precision casting method of the present invention, a breathable mold is set in the chamber,
The molten metal suction tube formed in the mold is projected downward from the bottom opening of the chamber, and the tip of the molten metal suction tube is immersed in the molten metal to depressurize the inside of the chamber to suck the molten metal. In the vacuum suction precision casting method that sucks up from the upper pipe to the product molding part in the mold through the runner,
A riser portion is formed above the product forming portion of the mold, the runner connected to the molten metal suction pipe and the upper portion of the riser portion are connected through a gate, and the product forming portion is formed by depressurizing the chamber. And the feeder is filled with the molten metal, and immediately after that, the depressurized state of the chamber is released.

[Operation] Even if the depressurized state is immediately released, the molten metal filled in the feeder part, that is, the molten metal supply action of the feeder prevents the formation of cavities in the molded part of the product.

[Embodiment] Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2a to 2c. FIG. 1 is a longitudinal sectional view showing an example of a breathable mold used in this casting method. In the figure,
1 is a hollow cylindrical runner, 2 is a molten metal suction pipe extending downward through a bulging portion 3, 4 is a runner 1 extending upward and a large diameter portion 5 for preventing slippage at the upper end It is a robot gripping part formed. Reference numeral 6 denotes a product molding portion, on which a cylindrical feeder portion 7 is formed. Then, the upper part of the feeder part 7 and the runner 1 are connected by a gate 8 having a slightly smaller diameter. This mold was formed by applying a binder and a molding sand alternately in layers on the surface of a wax mold, heating it to melt the wax, and then baking it to form air permeability. To be done. However, this mold is placed in a chamber 9 as shown in FIG. 2a, the molten metal suction tube 2 is hung down from the bottom opening 10 of the mold, and its tip is immersed in the molten metal, and the inside of the chamber 9 is decompressed. , The molten metal is sucked up into the product molding portion 6 through the suction pipe 2 and the runner 1. Then, when the molten metal has filled the product molding portion 6 and the feeder portion 7, the decompressed state of the chamber 9 is released. Then, as shown in FIG. 2b, the molten metal in the runner 1 flows out by its own weight, and the molten metal remains in the product molding portion 6 and the feeder portion 7 in an unsolidified state. The molten metal in the feeder part 7 compensates for the molten metal shortage due to the solidification shrinkage of the molten metal in the product molded part 6 during the process of cooling and solidifying the molten metal in the product molded part 6 as shown in Fig. 2c. Since the whole is solidified in such a form, the product molding portion 6 does not have a cavity defect. The product weight is
Conventionally, for a large cast product weighing 500 grams or more, the depressurization holding time was conventionally required for about 60 to 240 seconds, but according to this method, it was sufficient to hold the chamber under depressurization for about 10 seconds. That is, in the conventional method, in the case of a large-sized product, it takes a long time to solidify, so that it was necessary to take a long time for holding the reduced pressure after casting. Since it is eliminated, the required time is greatly reduced and the productivity is improved. Also, because the depressurized state can be released early and the molten metal in the runner can be returned to the bath before it almost solidifies, the yield of the molten metal is further improved and the work of collecting the metal in the runner part after casting is reduced. is there.

[Effects of the Invention] As described in the above embodiments, the precision casting method of the present invention can produce a precision casting product without a cavitation defect by simply holding the pressure reduced for a short time, improving product quality, improving yield, and It has a remarkable effect in improving operating efficiency and saving labor.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a mold according to the present invention, FIGS. 2a to 2c are vertical sectional views showing the steps of the casting method of the present invention in order, and FIGS. 3a to 3d. FIG. 4 is a vertical cross-sectional view showing in sequence the steps of a conventional vacuum suction precision casting method. 1 ... runner, 2 ... molten metal suction tube, 6 ... product molding part,
7: riser part, 8 ... gate, 9 ... chanba, 10 ...
… Bottom opening.

Claims (1)

(57) [Claims] 1. A breathable mold is set in a chamber, a molten metal suction pipe formed in the mold is projected downward from a bottom opening of the chamber, and a tip of the molten metal suction pipe is immersed in the molten metal. A vacuum depressurization precision casting method in which the molten metal is sucked up from the molten metal suction tube through a runner into the product forming portion in the mold by dipping and depressurizing the inside of the chamber, A riser portion is formed in the upper part of the molten metal suction pipe, the runner connected to the molten metal suction pipe is connected to the upper part of the riser portion through a gate, and the melt is depressurized to the product forming portion and the riser portion by depressurizing the chamber. A reduced-pressure suction precision casting method, characterized in that the filled state is filled and immediately after that, the reduced-pressure state of the chamber is released.