Metal treatment – Process of modifying or maintaining internal physical... – With casting or solidifying from melt
Reexamination Certificate
2000-09-18
2003-05-13
Wyszomierski, George (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
With casting or solidifying from melt
C148S695000, C164S120000, C164S900000
Reexamination Certificate
active
06562155
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for producing an aluminum alloy semi-molten billet for use as a transportation unit.
Thixocasting using a semi-molten billet is an art having recently attracted considerable attention because of its advantages in which less segregation and fewer defects of casting as well as a longer service life of a mold are available when compared with conventional die-casting. There are several different processes for producing the billet. One of them is system “A” known as the Pechiney Alumax System in which a melt is electromagnetically and mechanically agitated at a semi-melting temperature in order to provide spheroidized primary crystals &agr; (Al) at a billet-producing stage. Another process is system “B” in which a compound of Al—Ti—B is added to a melt during casting in amounts greater than when usually added, and then the melt is heated up to a semi-melting temperature range, thereby yielding spheroidized primary crystals &agr; (Al).
A further process is system “C” in which strain is introduced into a melt by means of extrusion/rolling, and the melt is thereafter heated up to a semi-melting temperature range so as to provide spheroidized primary crystals &agr; (Al) as practiced in the above system “B.”
Such conventional processes for producing the semi-molten billet suffer from various problems. For example, system “A” results in a very complicated process of manufacture, and adds to manufacturing cost. System “B” involves addition of a large quantity of Al—Ti—B, and then TiB
2
settles down in a melting furnace, with consequential instability of casting quality. In system “C”, for strain to be introduced into the melt by means of rolling, uniform strain is difficult to provide. For strain to be introduced into the melt by means of extrusion, such extrusion usually involves a complicated manufacturing process, and further encounters a difficulty of introducing even strain into the melt. Moreover, these two methods for introducing the strain into the melt in system “C” require machining a worked product. This requirement hinders mass production and is a cost drawback.
SUMMARY OF THE INVENTION
In view of the above, an object of the present invention is to provide a process for producing an aluminum alloy semi-molten billet for use as a transportation unit, whereby a simpler manufacturing process and lower cost are realized, with the result that products of uniform quality are available. The above object is achievable by the foregoing process according to the present invention, the process including the steps of: producing an aluminum alloy having a composition consisting essentially of, in weight %, 0.5 or less Cu, 5.0 to 10.0 Si, 0.2 to 0.7 Mg, 0.35 or less Zn, 0.55 or less Fe, 0.5 or less Mn, 0.005 to 0.5 Ti, and the balance aluminum, introducing working strain into a melt of the aluminum alloy by means of molding flask-assisted cold forging at a strain percentage of 10 to 40%, at a working introduction velocity of 10 mm or less per second, and at a temperature of 200° C. or lower; and, thereafter retaining such strain introduced melt at temperatures in a range of 576 to 585° C.
REFERENCES:
patent: 4415374 (1983-11-01), Young et al.
patent: 5133811 (1992-07-01), Kirkwood et al.
patent: 5536337 (1996-07-01), Wei
Iwashita Tsunaki
Kamio Akihiko
Mikubo Shigeru
Mizouti Masafumi
Murayama Yasuyuki
Combs Morillo Janelle
Jordan and Hamburg LLP
Kyusyu Mitsui, Aluminum Co., Ltd.
Wyszomierski George
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