Method Of And Molten Metal Feeder For Continuous Casting

Abstract

The invention provides a feeder for delivery of molten metal into a mold formed between confronting casting surfaces of a continuous casting machine. The feeder comprises a projecting nozzle tip having at least a lower wall provided with a molten metal-contacting inner surface, a generally flat outer surface and an end surface at an outer extremity of the tip extending between the inner and outer surface. The inner surface is generally flat and preferably slopes towards the outer surface considered in a direction moving towards the extremity of the tip at an angle of slope of no more than 8 degrees. The end surface is generally flat and extends from the inner surface to the outer surface at an acute angle of less than 88°, e.g. in the range of 15 to 80 degrees, relative to the inner surface in a direction away from the extremity of the tip. The feeder casts a metal sheet article having reduced surface defects caused by rupture of the metal oxide during casting.

Description

TECHNICAL FIELD [0001] This invention relates to the continuous casting of molten metals, preferably aluminum and aluminum alloys. More particularly, the invention relates to a method of introducing the molten metal into the casting cavity of a continuous caster and the design of a metal feeder used for this purpose. BACKGROUND ART [0002] Continuous casting of metals has been carried out for many years, e.g. by using a twin belt caster, twin roll caster or rotating block caster. Continuous casters of this kind usually have a horizontal, or slightly downwardly-sloping, casting cavity formed between two confronting and continuously rotating casting surfaces. The molten metal is introduced into one end of the casting cavity and it is cooled and solidified as it is drawn through the casting cavity by the rotating casting surfaces. A cast ingot, slab or strip of solidified metal emerges from the casting cavity at the opposite end. [0003] Molten metal is introduced into the casting cavity...

AI Technical Summary

Benefits of technology

The present invention aims to improve the continuous casting of molten metal, particularly aluminum and its alloys, by reducing surface defects and oxide incorporation. This is achieved by improving the design and placement of the nozzle used for injecting molten metal onto the casting surface. The nozzle has a projecting tip with a wall that interconnects at a line and forms an included angle of less than 88 degrees with the line. The inner surface of the nozzle has a molten metal-contacting inner surface, an outer surface, and an end surface at the outermost edge of the tip. The end surface is positioned at a small gap from the casting surface. By using this design, the frequency of oscillation of the meniscus (the layer of metal between the nozzle and the casting surface) is increased, resulting in a more uniform appearance of the cast product. The invention also addresses the issue of oxide whisker formation and interference with the oscillations of the meniscus, which can be minimized or eliminated by improving the design of the nozzle.

Problems solved by technology

However, in continuous strip casting, scalping may not be practical or economical and it is desirable to provide an article at the outset having a minimum of surface defects.

Such defects arise from the inevitable surface oxides that form on the meniscus surface of the molten metal where it exits the metal feeder to contact the moving casting surface.

As the meniscus is dragged along by the moving casting surface, the oxide film becomes strained and breaks, causing relatively large and visible surface defects of an irregular nature.

This not only affects the appearance of the cast article, but also can introduce structural weaknesses that cause rollability problems.

The defects are particularly critical in surface critical applications such as foil stock, can stock and automotive sheet, and can limit the speed of casting.

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