Dispensing – Molten metal dispensing – With subjacent flow guide
Patent
1994-11-10
1997-01-07
Kastler, Scott
Dispensing
Molten metal dispensing
With subjacent flow guide
222594, B22D 4150
Patent
active
055913717
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Technical Field of the Invention
This invention relates to continuous casting nozzles, and more particularly to submerged entry nozzles for use with narrowly rectangular plan section continuous casting moulds for use in producing thin slabs or direct cast strip, together with arrangements for liquid metal delivery utilising such nozzles.
Brief Description of the Prior Art
The continuous casting of such slabs of relatively large aspect ratio of width to thickness is carried out by pouring (teeming) molten metal from a tundish down into (in plan view) an elongate rectangular cavity or mould, the long walls of which are defined by a pair of driven rolls one on either side of the cavity or mould by means of which the pool of solidifying steel is commenced in its downward solidification path of travel, and the end walls of which are defined by, for example, appropriately shaped plates abutting the ends of the rolls.
Passage of the molten metal from the tundish to the casting mould is usually via a nozzle attached at its inlet end to the base of the tundish, and having its outlet end submerged within the pool of molten metal within the cavity or mould.
In such continuous casting apparatus the design of the input nozzle to the mould is of great importance. Thus, with commonly used circular section nozzles, often mounted at their upper end on metal flow control valves external to the tundish, and with such an elongate mould configuration, serious difficulties can arise from metal travelling into the mould from the nozzle with different velocities at different dispositions so that whereas at some locations vigorous stirring of the incoming metal within the mould occurs, at others far less stirring occurs leading to what are in effect dead spots. Such variation can easily result in uneven solidification of the thin slab leading to surface defects of the product. Again, the nozzle design can result in the metal emerging from the nozzle into the mould with a high velocity which, if the stream of the metal is directed at newly solidified steel on the surface of the mould wall, increases the risk of uneven solidification and product surface imperfection.
Yet again, and somewhat conversely, problems arise if stirring within the mould is such that stirring velocity close to the upper liquid surface of the pool is inadequate, whereby surface freezing becomes likely, which must be avoided since a frozen "skull" on the pool surface can be pulled into the driving rolls, possibly dragging the nozzle with it. A further potential problem is that if molten steel is delivered unevenly to the entry of the rolls it is possible that the resulting product will contain surface wrinkles running along its length.
It is an object of the present invention to overcome or at least substantially reduce the above mentioned problems.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided an entry nozzle for transporting liquid metal from a tundish to a mould for the continuous casting of thin slab disposed therebelow, wherein the nozzle has a hollow channel therethrough, and at least at its lower outlet end, is, in plan section, of large aspect ratio of width to thickness, and is hollow substantially across its width, the entry nozzle being provided at positions at its lower outlet end arranged in operation to be submerged within the casting mould, with at least one exit port from the hollow channel disposed on each elongate side of the nozzle, and, with the nozzle in its operational disposition, so shaped as to direct, metal into the mould from the nozzle transverse to its vertical disposition.
The entry nozzle may be of narrow thickness and elongate width substantially throughout its length, as may the elongate channel therethrough, and the nozzle may (and the channel may) be tapered down its length. Both nozzle and channel may be generally rectangular in plan section.
A plurality of outlet ports may be provided along each side of the lower outlet end of the nozzle.
To ensure that t
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Barnes John S.
Breugelmans Adrianus C. M.
Jones Timothy
Thompson Graham L.
British Steel PLC
Kastler Scott
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