Immersion nozzle for continuous casting and continuous casting method using the immersion nozzle

Abstract

An immersion nozzle for continuous casting which enables improvement in quality of a slab surface and increase in the efficiency of casting by suppressing the self-excited oscillation of a flow in a mold without using a complicated mechanism such as a swirl flow generating immersion nozzle is to be provided. A first immersion nozzle for continuous casting is a nozzle comprising a cylindrical body and a pair of outlet ports formed to face each other in a side wall in the vicinity of a bottom part of the cylindrical body, wherein a ridge-shaped projection extending parallel with the discharge direction projected on a cross section of the nozzle is formed on an inner surface of the bottom part, which is formed in a waterfall basin-like recessed shape having a maximum depth of 5 mm to 50 mm. A second immersion nozzle for continuous casting is a nozzle comprising a cylindrical body and a pair of outlet ports formed to face each other in a side wall in the vicinity of a bottom part of the cylindrical body, wherein each sectional area of the outlet ports vertical to a discharge direction projected on a cross section or longitudinal section of the nozzle is decreased toward an exit.

Description

TECHNICAL FIELD [0001] The present invention relates to an immersion nozzle for continuous casting of a molten metal such as molten steel or the like and a continuous casting method using the same. BACKGROUND ART [0002] In a continuous casting, such as a wide slab casting, which provides a molten metal into a mold with the use of an immersion nozzle having a pair of outlet ports facing each other, a fluid in the mold causes fluctuation of a certain period, that is, the self-excited oscillation, so that a flow velocity fluctuation or bath level oscillation of the molten metal in the mold is likely to occur. As a result, a slab surface causes trouble in quality due to a non-metal inclusion, bubble, mold powder or the like caught in a solidified shell in the mold. In the case that a flow rate of the molten metal from the outlet ports is high such as a high speed casting, these problems are noticeable. Thus, it has been necessary to decrease a casting speed. [0003] Conventionally, in or...

AI Technical Summary

Benefits of technology

[0012] According to the immersion nozzle for continuous casting of the present invention, the molten metal can be stably discharged from the immersion nozzle without using a complex mechanism such as the swirl flow generating immersion nozzle. Hence, the self-excited oscillation of a flow in a mold is suppressed, as a result, improvement in quality of a slab surface, and increase in the efficiency of a long-time casting are possible. The immersion nozzle for continuous casting and the continuous casting method using the same of the present invention are particularly suitable for the slab casting. A slab having less surface defect and inner defect can be produced.

Problems solved by technology

As a result, a slab surface causes trouble in quality due to a non-metal inclusion, bubble, mold powder or the like caught in a solidified shell in the mold.

In the case that a flow rate of the molten metal from the outlet ports is high such as a high speed casting, these problems are noticeable.

However, since a design cost of the method using the electromagnetic force is high, a merit which matches the high investment often cannot be obtained.

Also, since it is difficult to sense a molten metal flow which is an object to be controlled, the control is performed but the condition of the object to be controlled often remains unclear.

Hence, it is difficult to exhibit sufficient effect technically.

However, in the case of casting a molten metal having a low cleaning level containing a lot of non-metal inclusions, there is a problem that casting of vast amount of molten metal cannot be performed continuously since the non-metal inclusion is likely to be attached to the swirl blade inside of the nozzle.

However, since the effect is small, further improvement is still required.

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