Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1995-05-11
1997-12-16
Lin, Kuang Y.
Metal founding
Process
Shaping liquid metal against a forming surface
164 711, 164480, 164488, 164900, 222593, B22D 1106, B22D 2702, B22D 2708, B22D 3506
Patent
active
056974256
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of producing thin cast sheets (band-shaped) through continuous casting of a semi-solidified metal (alloy) slurry as a raw material for high-quality and low-cost sheets in which the formation of fine grain structure and the fine dispersion are conducted to mitigate the segregation and surface cracking and improve the workability.
BACKGROUND ART
A satisfactory technique of continuously casting semi-solidified metal slurry has not yet established in the art.
The primary reason is due to the fact that the semi-solidified metal slurry is solidified by slight losses of heat.
That is, the temperature of the semi-solidified metal slurry at the production step of the semi-solidified metal slurry is naturally lower than a liquidus line of the metal, so that when heat of the semi-solidified metal slurry is reduced by contacting the slurry with an inner wall surface of a discharging device (e.g. discharge nozzle) during the discharge of the semi-solidified metal slurry, even if the heat loss is slight, there is caused adhesion of high melting point component (e.g. Al.sub.2 O.sub.3 or the like) in the semi-solidified metal slurry to the wall surface of the device, as well as solidification adhesion of the semi-solidified metal slurry itself to the wall surface and the like. Thus, a so-called, solidification shell adheres to the wall surface.
In the discharging device for the semi-solidified metal slurry, therefore, there is a basic problem that it is apt to cause difficulty in controlling the discharge amount, clogging of the nozzle and the like due to the adhesion of the solidification shell. For this end, it is important to solve this problem in order to conduct the continuous casting by supplying the semi-solidified metal slurry into a continuous casting machine through the discharge nozzle.
In general, an immersion nozzle is used to supply molten metal from a tundish into a continuously casting mold.
Regarding the immersion nozzle, in order to avoid precipitation adhesion of the high melting point component to the inner wall surface of the nozzle during the introduction of molten metal or solidification adhesion of molten metal itself to the wall surface based on the loss of heat through the nozzle, or so-called clogging trouble of the nozzle runner due to the adhesion of solidification shell, there are known, for example, a countermeasure wherein an electric heating body is inserted into the nozzle to preheat the nozzle from its inner side as disclosed in JP-A-63-286268 (method of heating tundish nozzle), a countermeasure of preheating the nozzle from its inner side through a burner, a countermeasure wherein the nozzle body is made from an electrically conductive refractory material and a current is directly supplied to heat the nozzle as disclosed in JP-B-63-24788, a countermeasure wherein an induction heating coil is arranged around the outer periphery of the nozzle to heat molten metal passing through the nozzle by induction heating, and the like.
However, it has been confirmed that all of the above countermeasures are unsuitable when the above immersion nozzle for molten metal is used as a discharge nozzle for the semi-solidified metal.
That is, in case of preheating with the electric heating body or the burner, it is practically difficult to raise the preheating temperature up to a temperature exceeding 1000.degree. C. at the inner wall surface of the nozzle and the heating can not be conducted during the passing of the semi-solidified metal through the nozzle. In the actual operation, therefore, the temperature of the inner wall surface of the nozzle specially preheated drops during the discharge of the semi-solidified metal before the completion of the discharge and a part of the semi-solidified metal passing through the nozzle forms a solidification shell and adhered to the wall surface by due to heat loss through the wall surface to thereby cause the clogging of the nozzle.
In the case of directly supplying the current to heat the nozzle, there are pr
Hironaka Kazutoshi
Moriya Takaharu
Muraki Mineo
Murata Yasuyuki
Nanba Akihiko
Lin Kuang Y.
Miller Austin R.
Rheo-Technology Ltd.
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