Method and equipment for the integral casting of metal strip clo

Details Method and equipment for the integral casting of metal strip clo Method and equipment for the integral casting of metal strip clo

1996-07-24

1999-06-29

Batten, Jr., J. Reed

Metal founding

Process

Shaping liquid metal against a forming surface

164429, 164437, 164489, 222595, 266239, B22D 1106, B22D 1110

Patent

active

059154594

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a method of integrally casting metal strip close to its final dimensions on a strip-casting apparatus provided with a melt-holding vessel and a conveyor belt. A metal melt, in particular of steel, flows out via a casting nozzle from a closable pouring chamber which can be put under vacuum and is connected via a siphon to a main chamber which can be put under pressure.
2. Description of the Prior Art
During the integral casting of a strip-casting apparatus for producing metal strip close to its final dimensions, air inclusions in the casting nozzle lead to considerable impediments in the casting operation.
EP 0 534 174 discloses methods and the equipment required therefor, which are intended to expel the air from the casting nozzle and the region located upstream. Here, it is first of all proposed to initially set in the melt distributor a filling level which corresponds at most to the conveyor-belt plane and to set during the integral casting such a filling level which expels the melt from a casting nozzle which is curved in a U-shape. It has been found in practice that air collects in the center upper region of the casting nozzle which is curved downward in a U-shape. This essentially leads to the occurrence of an uncontrollable starting surge which can prevent feeding of the strand.
It is therefore also proposed in the EP 0 534 174 to provide a pouring chamber between the melt distributor and the casting nozzle and, during the integral casting--when the inlet of the casting nozzle arranged downstream of a siphon is closed relative to the metal melt--to build up a vacuum in the pouring chamber and to expel the air upward in the casting nozzle.
Even during this procedure, impediments during the integral casting cannot be avoided, since the air bubbles rise in opposite direction to the flow of the metal melt. During the process, uncontrollable constrictions in parts of the casting nozzle occur, which in turn result in an unwanted effect on the spreading of the metal melt on the conveyor belt.


SUMMARY OF THE INVENTION

With knowledge of the known difficulties, it is an object of the present invention to provide a method and the equipment required therefor, by which reliable expulsion of the air during the starting phase is ensured.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a method for integrally casting metal strip close to its final dimensions with a strip-casting apparatus having a melt-holding vessel which defines a closeable pouring chamber which can be put under vacuum and a main chamber which can be put under pressure and is connected to the pouring chamber by a siphon. A conveyor belt is provided and a casting nozzle is connected to the pouring chamber and has an orifice facing the conveyor belt. The method includes closing the orifice of the casting nozzle before casting begins, filling the main chamber and the pouring chamber with a liquid metal so that melt levels .DELTA. h.sub.A (initial level before casting) and .DELTA. h.sub.G (level during casting) are set at a value of .alpha. h.sub.A .DELTA. h.sub.G >5 in the main chamber relative to a liquid metal level present in a stationary operating state on the conveyor belt. Next, the casting nozzle is opened in a slit-shaped manner on a side of the nozzle inclined toward the main vessel to begin casting so that a liquid metal velocity directed downward is greater than an uplift velocity of gas bubbles penetrating the liquid metal. The differential melt level .DELTA. h.sub.G in the main chamber is lowered, while simultaneously continuously maintaining the casting nozzle open until the orifice area is completely cleared, to a value slightly above the liquid level on the conveyor belt, so as to permit siphoning.
The inventive apparatus for strip casting metal strip close to final dimensions includes a conveyor belt, and a melt holding vessel including a main chamber and a pouring chamber. The

REFERENCES:
patent: 1180728 (1916-04-01), Klocke
patent: 3412899 (1968-11-01), Sutter
patent: 5063989 (1991-11-01), Powell et al.
patent: 5170839 (1992-12-01), Feuerstacke et al.
patent: 5538071 (1996-07-01), Johansson et al.
patent: 5547014 (1996-08-01), Bruckner et al.

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