Aluminum-based alloy cast product and process for producing the

Details Aluminum-based alloy cast product and process for producing the Aluminum-based alloy cast product and process for producing the

1993-11-08

1995-03-07

Lin, Kuang Y.

Metal founding

Process

Shaping liquid metal against a forming surface

164900, B22D 1700, B22D 2300

Patent

active

053949315

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a process for an aluminum-based alloy cast product and a process for producing the same, and particularly, to a process for producing an aluminum-based alloy cast product by preparing a casting material having solid and liquid phases coexisting therein and then subjecting the casting material to a casting under pressure, and to an aluminum-based alloy cast product.
The term "casting material" used herein means a semi-solidified material prepared by cooling a molten metal having an aluminum-based hypo-eutectic alloy composition, or a semi-solidified material prepared by heating a solid material having an aluminum-based hypo-eutectic alloy composition, an aluminum-based eutectic alloy composition or an aluminum-based hyper-eutectic alloy composition. Such a process has been developed for the purpose of improving the cast quality of a cast product.


PRIOR ART

There is a conventionally known casting process using a semi-solidified material of the above-described type, which is disclosed in Japanese Patent Application Laid-open No. 152358/85.
The present inventors have made various studies about a casting process of such type using a casting material having an aluminum-based hypo-eutectic alloy composition. And as a result, they have found that a cast quality and mechanical properties of the cast product as well as the control of casting conditions are influenced by a nature of the casting material during passage through a gate, a pressurizing force on the casting material filled in a cavity, the average temperature drop rate of the molten metal in preparation of a semi-solidified material as a casting material, an area rate of initial crystals .alpha.-Al having a shape factor F equal to or more than 0.1 in a solid material used for preparation of a semi-molten material. Further, the inventors have found that the pressurizing force may become a factor for an operational problem such as the generation of a flash and the like, and that in order to improve the productivity without deterioration of the cast quality and mechanical properties of the cast product, it is necessary to appropriately set the speed of the casting material during passage through the gate.
If the solid phases of the semi-molten material are spherical and uniformly dispersed in liquid phases, the semi-molten material has an excellent thioxotropy (deformability). Therefore, it is possible to produce a cast product having a dense metallographic structure from such semi-molten material by utilization of casting process under pressure.
From this viewpoint, a casting process using a casting material by strongly stirring a molten metal while cooling the latter to achieve a spheroidization of the solid phase, i.e., a thixocasting process has been developed.
In this casting process, however, a molten metal strongly-stirring step is required as an essential step, resulting in a troublesome operation. Thus, an improvement in this respect has been desired.
Thereupon, a process for producing a high strength structural member has been proposed which comprises the steps of: subjecting a casting material resulting from a usual casting process to a hot extrusion to comminute coarse grains and dendrites to prepare a primary solid material having a granular crystalline structure with a directional property and; subjecting the primary solid material to a straining treatment such as a stretching to prepare a secondary solid material having a granular crystalline structure with the directional property moderated; heating the secondary solid material to prepare a semi-molten material; and subjecting the semi-molten material to a forming under pressure (see Japanese Patent Application Laid-open No. 149751/85).
The above prior art process aims at spherically shaping the solid phases in the semi-molten material by subjecting the primary solid material having the granular crystalline structure with the directional property to the straining treatment. However, this prior art process suffers from a problem that

REFERENCES:
patent: 4771818 (1988-09-01), Kenney
patent: 5186236 (1993-02-01), Gabathuler et al.
Patent Abstract of JP 4033761 Feb. 1992.
Patent Abstract of JP 60152358 Aug. 1985.
Japan Casting Society "Rev. 4 Casting Handbook" (Jan. 20, 1986) Maruzen-author (Text in Japanese).

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