GB2198376A

GB2198376A - Immersion tube for continuous casting

Info

Publication number: GB2198376A
Application number: GB08724134A
Authority: GB
Inventors: Thomas Robertson; Kevin John Thompson
Original assignee: British Steel Corp
Current assignee: British Steel Corp
Priority date: 1986-10-15
Filing date: 1987-10-14
Publication date: 1988-06-15
Also published as: GB8724134D0; GB8624738D0; EP0264809A1

Description

2198376 REFRACTORY POURING TUBE This invention relates to refractory

tubes, commonly called pouring tubes or submerged entry nozzles, through which molten metal, e.g. steel, is poured into a continuoug casting mould from a tundish or other melt- containing vessel.

In continuous casting moulds of small cross-sectional area e.g. for casting billets or blooms, the submerged entry nozzles employed are often simple plain vertical tubes but, at least in cases where argon injection is not employed, these suffer from the disadvantage of creating a flow pattern which, whilst quiescent near the mould surface, allow inclusions to be carried deep into the molten metal 'sump' where entrapment is likely with the consequent impairment of strand quality.

in order to alter the pattern of flow in the mould it is necessary to direct the flow out through the side walls of the submerged entry nozzle, but in moulds of small cross section this normally results in high velocity jets impinging on the thin solidifying shell of steel, a highly undesirable state of affairs which can lead to surface quality problems or even breakouts.

It is an object of this invention to provide an improved refractory pouring tube.

From one aspect the present invention provides a refractory tube through which molten metal is poured into a continuous casting mould, the tube having its lower end sealed and a plurality of channels extending laterally through the tube adjacent said end, the channels defining arcuate paths whereby to introduce a swirling motion to the metal issuing therefrom.

1 J 1 ( -) _11 In accordance with this invention then the flow pattern promoted is tangential to the mould walls. Thus, bearing in mind the common provision of electromagnetic stirring to generate this pattern this technique may be used to reduce or even eliminate the need for electromagnetic stirring systems; this is a major financial saving.

In order that the invention may be fully understood, one embodiment thereof will now be described with reference to the accompanying drawings in which:- Figure 1 is an axial section of a refractory pouring tube according to this invention; Figure 2 is a cross-section on A - A in Figure 1; Figure 3 is a 'segmental ' axial section on B - B in Figure 2; and Figures 4 (a) and 4 (b) illustrate the tangential flow patterns at the channel exits.

Referring now to Figures 1 to 3 the tube comprises an elongated body section 1 having a high integrity insert 2 at its upper end and a nozzle section 3 at its lower end. This nozzle, which. in this example is made as a separate part, has a closed bottom but incorporates three channels 4 which extend laterally through the wall of this nozzle and define arcuate paths. This is seen more clearly in Figure 2 which is a section through the nozzle.

2 I) Typically, with a tube of say 100Omm length, 10Omm diameter, and 55mm bore the nozzle may have an external diameter of 140mm, the channel walls being say 18mm thick, the 'port' or channel height being 35mm and wi dth 15mm.

Figures 4 (a) and 4 (b) show the tangential flow pattern produced.

Typically, with a casting speed of say 0.45m/min, a mould diameter of 40Omm and the pouring tube immersed to a depth of 120mm the angular velocity of the molten steel within the mould is of the order of 0.70 rads/sec giving a mean velocity at the wall of about 13 cms/sec. This compares favourably with say, 15 to 30 cms/sec obtained with electromagnetic stirring bearing in mind the potential for increasing the tangential velocity with this development by reducing the port apertures.

Similar velocities may readily be achieved with square moulds.

Although this invention has been described with reference to the particular embodiment illustrated it is to be understood that various modifications may readily be made without departing from the scope of this invention. For example more than three arcuate channels may be provided and they -may be at the same or different levels with all or some directed upwardly or downwardly; the shape and dimensions of same may also be modified to secure the most efficient flow patterns.

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Claims

We Claim:-

A refractory tube through which molten metal is poured into a continuous casting mould, the tube having its lower end sealed and a plurality of channels extending laterally through the tube adjacent said end, the channels defining arcuate paths whereby to induce a swirling motion to the molten metal issuing therefrom.
2. A tube according to claim 1, comprising three channels adjacent said end, equidistantly spaced circumferentially and lying in a common plane normal to the axis of the tube.
3. A tube according to claim I or claim 2, in which the outer side of each channel is defined by a protruding wall such that the plane of the orifice of each channel lies substantially radially of the tube, whereby the molten metal issuing therefrom follows an unobstructed path tangential to said wal 1 s.
4. A tube according to any one of claims 1 to 3, in which the channels extend from a circular section bore of substantially constant diameter throughout its length.
5. A tube according to any one of claims 1 to 4, in which at least that part of the tube defining the channels is made as a separate section of said tube.
6. A refractory tube substantially as herein described with reference to accompanying drawings.

4 Published 1988 at The Patent Office, State House. 66,71 High Holborn, London WC111 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Maxy Cray, Orpington, Kent BR5 3RD Printed by Multiplex techniques ltd. St Mary Cray, Kent. Con. 1/87.

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