Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1980-10-14
1984-05-08
Lin, Kuang Y.
Metal founding
Process
Shaping liquid metal against a forming surface
B22D 1802
Patent
active
044469071
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a die-casting method and, more particularly, to a die-casting method in which a molten metal is injected through a runner into a die cavity for casting an article and the molten metal in the die cavity is squeezed also through a squeeze passage by means of a squeeze plunger, the squeeze passage being communicated with the die cavity at a portion other than the portion where the runner is communicated with the die cavity.
BACKGROUND ART
Japanese Laid-open Patent Publication No. 51-129817 discloses a die-casting method in which the molten metal in a squeeze passage communicated with a die cavity at a portion other than the portion through which a runner is communicated with the die cavity is forcibly displaced by a squeeze plunger back into the die cavity. In the apparatus disclosed in Japanese Laid-open Patent Publication No. 51-129817, however, the squeeze passage has a shape as shown in FIG. 1 and the molten metal .alpha. in the squeeze passage displaced by the squeeze plunger 36 is restricted by a communication passage having a cross-sectional area smaller than that of the squeeze passage and, thereafter, is displaced back into the die cavity 30.
The present inventors conducted experiments with respect to this squeezing method. The test result showed that the force required for advancing the squeeze plunger was fluctuated over a wide range with a resultant difficulty to obtain a stably constant squeezing pressure. The present inventors considered that the fluctuation of the squeezing pressure encountered in the use of such an apparatus as shown in FIG. 1 was for the following reason. Namely, the moment at which the forward movement of the squeeze plunger 36 is started is inevitably delayed from the filling up of the squeeze passage 17 by a predetermined time period during which the surface of the molten metal .alpha. is solidified. Therefore, when the squeeze plunger 36 is advanced, the squeeze plunger 36 is required to displace also a solidified layer .beta. of the metal. It is considered that the solidified layer .beta. in the squeeze passage 17 is blocked by the communication passage 17a during the forward movement of the squeeze plunger 36 and is shorn in a quite complicated manner.
It is considered that the difficulty in obtaining a constant squeezing pressure acting on the molten metal .alpha. in the squeeze passage 17 is attributable to the fact that the resistance due to the shearing of the solidified layer .beta. during the forward movement of the squeeze plunger 36 is largely fluctuated.
DISCLOSURE OF THE INVENTION
On the basis of the above consideration, the present inventors have discovered a die-casting method in which the squeezing is effected in such a manner that the molten metal is displaced into the die cavity from a squeeze passage communicated with the die cavity at a portion other than the portion of the die cavity which is in communication with the runner while the displaced molten metal forms a diverging flow. More specifically, an apparatus in used in which the portion of the die cavity at which the latter is communicated with the squeeze passage has a cross-sectional area greater than that of the squeeze passage over the entire region in the direction of movement of the squeeze plunger, so that the molten metal displaced out of the squeeze passage into the die cavity forms a diverging flow. The squeeze is effected by such a diverging flow of molten metal.
The inventors have conducted experimental die-casting operations by the method in which the molten metal displaced from the squeeze passage flows divergently into the die cavity, with a result that the molten metal could be forced into the squeeze passage at a stable pressure.
However, it was found that surface defects and segregations are apt to be formed at the portion of the die cavity where the molten metal displaced from the squeeze passage flows divergently into the die cavity. Thus, it was confirmed that the die-cast articles produced by this method have inferior str
REFERENCES:
patent: 3106002 (1963-10-01), Bauer
Hashimoto Shigeyoshi
Suzuki Haruo
Lin Kuang Y.
Nippondenso Co. Ltd.
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