Semi-solid slurry generator and high pressure die casting method

Abstract

Disclosed are a semi-solid slurry generator and a die casting method which can obtain a dense structure in the entire cross section of a molded product by uniformly dispersing and stirring an inert gas in a slurry compared to a conventional one. The die casting method comprises: a step of immersing a rotating diffuser in a molten metal contained in a ladle to rotate and stir the molten metal while being supplied with an inert gas, or rotating and stirring the molten metal and the inert gas, which are sucked into a pumping impeller, while being ejected through a hole provided on a side surface of the impeller by stirring the same, such that the molten metal is cooled while gas bubbles caused by the inert gas are uniformly dispersed in the molten metal, thereby forming a semi-solid slurry; and a step of pressurizing and injecting the semi-solid slurry into a mold of a molding machine.

Description

TECHNICAL FIELD[0001]The present disclosure relates to improvements of a non-dendritic semi-solid slurry generator and a die casting method or a production technology. More particularly, the present invention relates to an improvement of a semi-solid slurry generator for obtaining a homogeneous semi-solid slurry in which crystals are micronized by performing bubbling and cooling through a diffuser that is immersed in a molten metal contained in a ladle to blow an inert gas and breaking dendritic crystals, and an improvement of a high-pressure die casting method for obtaining a molded product having a dense structure by pouring a semi-solid slurry into a molding machine and pressurizing and solidifying the slurry within the mold.BACKGROUND ART[0002]International Publication WO 2007 / 09223 A2 (inventors: WANNASIN, Jessada et al.) discloses a molding method for obtaining a molded product having a dense structure by immersing a porous graphite diffuser in a molten metal contained in the ...

AI Technical Summary

Benefits of technology

[0036]According to the present invention, it is possible to obtain a dense structure in the entire cross section of a molded product, compared with a conventional molded product by causing an inert gas to be uniformly dispersed, bubbled, and stirred in the slurry.

[0037]Since the metal slurry of aluminum or the like hardly adheres to the ceramic diffuser according to the present invention compared with the conventional graphite diffuser, the ceramic diffuser according to the present invention is much less likely to cause a product defect and the ceramic diffuser according to the present invention has a long lifespan and is easily replaceable.

[0038]In addition, according to the method of the present invention, it is possible to improve quality by stabilizing sticking, scraps and hot zones, and lowering the temperature of the molten metal (suppressing bubbles and cracks due to fusion sticking), and to obtain excellent effects, such as an increase of the life span of a mold (estimated 1.5 times), a decrease of mold surface temperature, a reduction of thermal fatigue, a reduction of thermal shock, a reduction of the melting loss, etc. by lowering the temperature of the molten metal at the time of pouring the molten metal from the ladle to the plunger by 60° C. or more (660° C. (conventional)->590° C. (improvement)).

[0039]According to the present invention, it is possible to obtain a semi-solid slurry having micronized crystals by immersing and rotating a porous impeller diffuser or a pumping impeller diffuser in the molten metal contained in the ladle, blowing an inert gas into the molten metal while rotating the diffuser so as to stir the molten metal vigorously while dispersing and bubbling the inert gas in the molten metal in a small bubble state, and cooling the molten metal and breaking dendritic crystals while bubbling the molten metal.

[0040]Particularly, since the pumping impeller diffuser has a function of rotationally stirring the molten metal and simultaneously ejecting the molten metal through the holes provided in the side surface by stirring the supplied inert gas and the molten metal sucked into the hollow portion through the opened lower portion of the hollow portion, the pumping impeller diffuser is excellent in the effect of uniformly distributing bubbles.

[0041]The semi-solid slurry obtained as described above is introduced into a molding machine and is pressurized and solidified inside the mold, thereby obtaining a molded product having a dense structure.

Problems solved by technology

However, in the prior art as described above, there is a problem in that, since the graphite diffuser 20 bubbles the inert gas in the molten metal 12 at a given pressure while maintaining the static state thereof, the inert gas is present only around the graphite diffuser 20, which makes it impossible to achieve uniform bubbling and micronizing of the entire molten metal 12.

That is, there is a problem in that, since a large amount of inert gas is present in the molten metal 12 around the graphite diffuser 20 and the inert gas bubbling effect does not occur in the molten metal 12 located far from the graphite diffuser 20, crystal grains cannot be properly micronized.

A product made using a semi-solid slurry having such a problem has a problem in that mechanical properties such as strength are not uniform in respective portions.

The graphite diffuser 20 has a short lifetime due to hardening or the like, and has a problem in that a residual molten metal of an Al-alloy or the like adheres to the diffuser to block the pores, which causes the gas to be unevenly supplied to the entire molten metal.

Alternatively, the residual molten metal, which has adhered to the diffuser, is mixed into the molten metal poured into a mold, making it difficult to produce homogeneous products.

When a product is made using such a semi-solid slurry, a defect is generated therein.

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