JPH0825006B2 - Low pressure casting method using sand mold - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for casting a casting such as an aluminum alloy using a sand mold, and particularly for improving the work efficiency and obtaining a high-quality casting without internal defects. Method.

2. Description of the Related Art As a casting method using a sand mold, the method shown in FIG. 4 is generally known. In the figure, reference numeral 1 denotes a sand mold, and a cavity 2 and a down spool 3 having a predetermined shape are formed inside the sand mold 1, and a molten metal 5 such as an aluminum alloy is formed from a spool cup 4 arranged above the down spool 3. By pouring the molten metal 5 into the down spool 3
Then, it passes through the runner 6 formed on the lower side of the down spool 3 and flows into the cavity 2. Reference numeral 7 is a feeder for replenishing the contraction amount of the molten metal 5 at the time of solidification. The molten metal 5 in the cavity 2 is pressed by static pressure, and the final solidified portion in the cavity 2 is pressed by this pressed metal. Replenishment of molten metal corresponding to the contracted volume from the hot water 7 prevents generation of contraction cavities.

Problems to be Solved by the Invention However, in such a conventional casting method using a sand mold, since the molten metal 5 is poured into the cavity 2 only by the gravity of the molten metal 5, There is a problem in that the molten metal is likely to be insufficiently replenished to a portion of the casting where solidification of the casting is slow, and as a result, internal defects such as shrinkage cavities may occur. Further, especially when the wall thickness difference of the cast product is large, it is difficult to completely replenish the molten metal only by the static pressure of the feeder, and it is possible to avoid the occurrence of internal defects caused by the occurrence of shrinkage cavities and the like. Not on
It has a drawback that the product finishing time becomes long and the work efficiency is lowered.

Therefore, the present invention solves the problems of the conventional casting method using a sand mold, does not cause internal defects such as shrinkage cavities in the cast product, and improves the work efficiency. It is an object of the present invention to provide a casting method that can be performed.

Means for Solving the Problems In order to achieve the above object, the present invention forms a plurality of runners on the lower side of a sand mold in which a cavity of a predetermined shape is formed, and Provide a feeder mold with a plurality of air vent holes on the upper side, and a molten metal channel in contact with the bottom surface of this sand mold to feed the molten metal into the cavity, and connect the air vent holes to a large sized large area exhaust hood. Then, at the same time when the molten metal fed from below the feeder mold into the runner of the feeder mold by the pressure of gas is injected into the cavity via the plurality of runners, the molten metal is blown into the cavity from the air vent hole of the sand mold. A low pressure casting method using a sand mold for forcibly sucking air into an exhaust hood.

Effect According to such a low-pressure casting method, the molten metal fed into the hot water passage of the feeder mold from below the feeder mold arranged in contact with the lower surface of the sand mold is formed on the lower side of the sand mold. The air in the cavity is injected into the cavity through a plurality of runners, and at the same time, the air in the cavity is forcibly sucked into the exhaust hood through a plurality of air vent holes connected to the large-sized and large-area exhaust hood. As a result, the excess gas existing in the cavity is forcibly discharged to the outside through the air vent hole, so that the molten metal easily enters the cavity, and the gas is not caught in the cast product. The effect is that a cast product free of defects is obtained.

Embodiment An embodiment of a low-pressure casting method using a sand mold according to the present invention will be described below with reference to FIGS. Detailed description.

In the configuration shown in FIG. 1, 11 is a holding furnace which has a heat insulating material 11a and a heating source 11b and is held at a high temperature. 12 is an iron crucible having a substantially U-shaped cross section,
The crucible 12 has an upper end 12b supported by the holding furnace 11, and a molten metal 5 made of an aluminum alloy or the like is charged into the crucible 12. Reference numeral 13 is a lid of the crucible 12, a gas flow passage 14 is formed inside the lid 13, and an air supply pipe is provided in the flow passage 14 via a connecting fitting 15.
16 are connected. Therefore, the gas supplied from the air supply pipe 16 is sent into the crucible 12 through the flow passage 14 and pressurizes the molten metal 5.

An opening 17 is formed in a substantially central portion of the lid body 13, and a tubular stalk 19 is inserted into the opening 17.
That is, the lower end portion 19a of the stalk 19 reaches near the bottom surface 12a of the crucible 12, and the collar portion 19b formed at the upper end portion of the stalk 19 on the spacer 18 arranged in the peripheral portion of the opening portion 17. Is supported. A pedestal 20 is arranged on the upper surface of the lid body 13, and a feeder mold 21 having a hot water passage 22 is arranged on the pedestal 20. FIG. 2 is a perspective view showing only the feeder mold 21 taken out.

On the other hand, 1 is a sand mold made of foundry sand, which has been previously molded into a predetermined shape by using a specific binder. A cavity 2 having a predetermined shape is formed inside the sand mold 1, and a plurality of runners 23, 23 communicating with the cavity 2 are formed on the lower side of the sand mold 1. The runways 23, 23 communicate with the runway 22 of the feeder type 21,
The molten metal 5 fed into the cavity 2 is fed into the cavity 2 via the runners 23, 23.

Furthermore, a plurality of air vent holes 24, 2 are provided on the upper side of the sand mold 1.
4 are provided, and these air vent holes 24, 24 communicate with a large-sized large area exhaust hood 25. The exhaust port 25a of the exhaust hood 25 is connected to a vacuum suction device (not shown).

A specific example of the casting method having such a configuration will be described below.

First, the molten metal 5 is put into an iron crucible 12 supported by a holding furnace 11 which is held at a high temperature, and the molten metal 5 is sealed by a lid 13 and a stalk 19, a feeder mold 21, a sand mold 1 and the like are shown in FIG. Set to. Next, from the air source (not shown)
By supplying pressured air to the crucible 12, the pressured air is sent into the crucible 12 through the flow passage 14 to pressurize the molten metal 5 charged in the crucible 12. Therefore, the molten metal 5 is a stalk
The inside of 19 rises as shown by the arrow A, reaches the hot water passage 22 formed in the feeder mold 21, and further, as shown in FIGS. 3 (A) and 3 (B), a plurality of sand molds 1 are formed. It is poured into the cavity 2 via the runners 23, 23. At the same time, the vacuum suction device connected to the exhaust port 25a of the exhaust hood 25 is driven to forcibly suck the air in the cavity 2 from the air vent holes 24, 24 provided on the upper side of the sand mold 1 as shown by arrow B. .

According to the above low-pressure casting method, the molten metal 5 is pressurized and poured into the cavity 2 by the compressed air, and the excess gas existing in the cavity 2 is discharged to the outside from the air vent holes 24, 24. The molten metal 5 easily enters the cavity 2, and the gas is not entrained in the cast product, so that a cast product having no internal defect is obtained. Further, the molded sand mold 1 is set between the feeder mold 21 and the exhaust hood 25, and after the pouring of the molten metal 5 is completed, the sand mold 1 is removed, and the other sand molds are set in the same manner as above to pour the molten metal. Since the casting operation of the casting is performed by repeating the series of steps of performing it, there is an advantage that one casting cycle is shortened.

The number and diameter of the runners 23, 23 can be set freely according to the shape or size of the cast product.

EFFECTS OF THE INVENTION As described in detail above, according to the low-pressure casting method using the sand mold of the present invention, the following operational effects are brought about. That is, when the molten metal is poured into the cavity, pressurized pouring is performed by compressed air, so that there is an advantage that the pouring speed is higher than that of the molten metal which is caused only by gravity. Therefore, it is possible to sufficiently replenish the molten metal in the portion of the cavity in which the solidification of the casting is slow, without using the feeder normally used in the sand mold, and as a result, it is possible to prevent the occurrence of internal defects such as shrinkage cavities. . Further, since the air in the cavity is forcibly sucked from the air vent hole provided in the upper part of the sand mold, the molten metal is more easily introduced into the cavity, and the gas is not caught in the cast product. Even if there is a large difference in wall thickness of the cast product, the molten metal can be completely replenished and the occurrence of shrinkage cavities can be eliminated. In particular, since a sand mold using foundry sand is used in this embodiment, it is possible to produce a thin cast product to some extent, and therefore there is no constraint on the shape or size of the cast product. The effect of being highly adaptable to is obtained. Further, since the pouring time can be shortened, the product finishing time is shortened, the work efficiency is improved, and it is not necessary to use the conventionally used feeder, so that the working process can be simplified. It will be brought.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of a low pressure casting method according to the present invention, FIG. 2 is a perspective view showing an example of a feeder type used in the present invention, and FIG. 3 (A) is FIG. FIG. 3B is a side view showing the enlarged main part of FIG. 3, FIG. 3B is a side view of the same, and FIG. 4 is a cross-sectional view of the main part showing an example of a conventional casting method using a sand mold. 1 ... Sand mold, 2 ... Cavity, 5 ... Molten metal, 11 ... Holding furnace, 12 ... Crucible, 13 ... Lid, 14 ... Flow passage, 16 ...
… Air supply pipe, 19 …… Stoke, 21 …… Feeder type, 22…
… Runners, 23 …… runners, 24 …… air vents, 25 …… exhaust hoods,

Claims (1)

[Claims] 1. A plurality of runners are formed on the lower side of a sand mold having a cavity formed in a predetermined shape, and a plurality of air vent holes are provided on the upper side of the sand mold. A feeder mold in which a molten metal passage is formed in contact with the cavity to feed the molten metal, and the air vent hole is connected to a large-sized exhaust hood, and the feeder mold is pressed from below the feeder mold by gas pressure. The sand mold is characterized in that the molten metal fed into the runner is injected into the cavity through the plurality of runners and at the same time the air in the cavity is forcibly sucked into the exhaust hood from the air vent hole of the sand mold. Low pressure casting method using.