JPS6039464B2 - Reduced pressure mold casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum mold casting method, in which the heat of sand and castings is actively removed by repeatedly replacing the air in the mold after molten metal is poured and solidified. This is an attempt to speed up the cooling temperature of the casting.

Generally, when casting using a reduced pressure mold, the reduced pressure in the mold is released after the Western-style casting has solidified.

Incidentally, since vacuum molding molds do not contain water and do not use a binder, they have a disadvantage that their cooling capacity is lower than that of green molds, and as a result, the internal structure of the casting becomes coarse.

Furthermore, since it takes a long time for the casting to cool down, there is a considerable disadvantage that the manufacturing efficiency of the casting is poor. This invention was proposed in view of the above-mentioned drawbacks of vacuum mold casting. Even with a vacuum mold, the cooling time of the casting is short, just like a green mold, and the internal structure of the casting is steel-tight. The purpose is to provide a vacuum molding molding method that can be used.
That is, the gist of the present invention is to repeatedly release and re-depressurize the mold after a predetermined period of time has elapsed after pouring the metal into the vacuum mold, thereby forcibly replacing the air inside the mold.

The present invention will be described in more detail below based on the accompanying drawings.

FIG. 1 shows an example of an apparatus used in the vacuum mold casting method of the present invention.

Normally, when making a mold using vacuum molding, sand is poured into the frame, the upper and lower surfaces of the frame are covered with an appropriate shielding material, the frame is sealed, and the inside of the mold is then heated to a specified reduced pressure. Vacuum suction is performed using a pump or the like.

By the way, when casting is performed using such a vacuum mold, as shown in Fig. 1, the upper mold 1 and the lower mold 3 are combined, and Western-style hot water is poured from the sprue provided at a predetermined position of the upper mold 1. Do this.

After pouring, when the solidification of the hot water in the molds 1 and 3 is completed, one end is closed into the upper molds 1 and 3, and the other end is inserted into a predetermined position of the pipe connected to the vacuum pump. valve 7
This valve 7 is closed to stop the vacuum suction inside the mold. In this case, since the sealing properties of the shielding material covering the upper and lower surfaces of the molds 1 and 3 are not perfect, air enters inside the mold, that is, between the sand particles solidified under reduced pressure. Then, the valve 7 is closed and the insides of the molds 1 and 3 are vacuumed again.

Then, the air that has entered the mold and been warmed will be sucked into the vacuum pump and discharged outside the molds 1 and 3.
Then, when the pressure inside the molds 1 and 3 reaches a predetermined set value such as 360 tons as shown in FIG. 2 by re-suctioning, the valve 7 is closed again. This process is then repeated for a predetermined time T. This predetermined time is the cooling acceleration time in the mold. In addition to sucking the warmed air inside the mold with a vacuum pump, we also forcefully send cold air into the mold, and then send out the warmed air from the shielding material side of the mold surface. It is also possible.

However, in this case, there is a problem in that the shielding material portion rises due to the forced air flow, and therefore cannot be adopted. diameter 2 by the following method of this invention and other methods.
A casting with 0 ribs and a length of 400 ribs was prepared, and the cooling rate of the mold and casting was measured, and the results shown in FIG. 3 were obtained.

In other words, in the case of conventional vacuum mold casting (marked with an x), when the molten metal is heated to 130,000 ℃, the casting temperature is approximately 60 ℃.
It takes about 3 minutes to descend to 000.

On the other hand, according to the present invention, (marked 0), after pouring the melt into the melt at 130,000 ℃ and completing solidification, the temperature of the casting decreases rapidly after about 5 minutes as a result of repeating the above-mentioned suction and exhaust. The time required for the temperature to drop to approximately 70,000 after about 1 minute has passed since the time of Western bathing is approximately 20,000 when casting with a green mold (△ mark). It was after a minute had passed. As described above, according to this invention, the cooling rate of the casting is faster than that of conventional vacuum mold casting, so the internal structure of the casting does not become rough, which occurs due to the slow cooling rate of the casting, and it is possible to cast with a green mold. In the same way, castings with a dense internal structure can be manufactured). Furthermore, increasing the casting cooling rate as described above also improves the casting production efficiency in the vacuum mold casting method, which is extremely practical.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an example of a device used in the method for accelerating the cooling rate of a casting in vacuum mold casting of the present invention, and FIG. FIG. 3 is a graph showing the relationship between the progression of time and the reduced pressure state. FIG. 3 is a graph comparing the temperature drop of castings manufactured by the method of the present invention and castings manufactured by other methods. 1...Top mold, 3...Bottom mold, 5...
...Pipe, 7...Valve, T...Cooling acceleration time. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A vacuum mold casting method characterized by releasing and depressurizing a mold that has been poured and solidified a predetermined number of times, thereby discharging the heat accumulated in the mold to the outside of the system.