EP0577909A1

EP0577909A1 - Replaceable auxiliary nozzle

Info

Publication number: EP0577909A1
Application number: EP92830368A
Authority: EP
Inventors: Romano Cappelli
Original assignee: FLOCON ITALIANA Srl
Current assignee: FLOCON ITALIANA Srl
Priority date: 1992-07-10
Filing date: 1992-07-10
Publication date: 1994-01-12

Abstract

A replaceable auxiliary nozzle (3) comprises: a refractory material element (4) associated to said nozzle the bottom end of which is a semi-spherical convex or conical surface, a sub-immersor nozzle (6) the top end of which is a convex or conical surface corresponding to the convexity or conical shape of said element (4). A control means (7) controls the position of said sub-immersor nozzle, along with a conter-weight device that serves to keep said sub-immersor nozzle held against the auxiliary nozzle. The coupling between semi-spherical or conical surfaces allows to remove said sub-immersor nozzle, by means of a rotation and further shifts, from the underlying ingot mold without having to raise the above tundish (1).

Description

The present invention concerns improvements on a replaceable auxiliary nozzle. The invention especially concerns improvements to a replaceable auxiliary nozzle suitable for use with a tundish for the continuous casting of steel or other metals. The following description will refer only to steel for sake of simplicity.
A replaceable auxiliary nozzle is noted, subject of patent n^o 1.220.146 filed by FERRIERE NORD S.p.A., used in a tundish for the continuous casting of steel. Said replaceable auxiliary nozzle, henceforward termed, for reasons of simplicity, auxiliary nozzle, is used in association with a fixed nozzle to be found on the bottom of the tundish. Said auxiliary nozzle is positioned on a slide-cursor that slides along the bottom of the tundish and is elastically urged against said fixed nozzle, according to an original system. Said slide-cursor slides along slots that allow the positioning of a second cursor, that carries a second auxiliary nozzle, while the first one is still in a working position, so that, by means of an appropriate positioning system of the second cursor and contemporary expulsion of the first cursor, the replacement of the auxiliary nozzles takes place without having to interrupt the casting cycle. This allows to considerably improve the operation of the casting machinery allowing for a greater number of continuous casting hours.
In seeking an ever increasing quality of manufactured steels, as the market requires, it is always more essential to provide for the protection of the steel jet from possible contamination, as is for example contact with air.
Hence there has been an expansion of adequate protective means, such as ceramic tubes protecting the jet from the ladle to the continuous casting tundish and from here to the underlying ingot-mold.
The noted auxiliary nozzle has the disadvantage of not allowing the use of the protective tube for the steel jet, so that, while falling into the ingot-mold, said jet is exposed to contamination.
The main problem that is solved by the improvements put forward by the present invention is to obviate the above mentioned disadvantage; they comprise, as characterized in the attached claims, a refractory material element, associated to the outlet port of the auxiliary nozzle, that has a semi-spherical convex or conical bottom surface and a hole that is coaxial with the hole in the auxiliary nozzle and comprises, moreover, a jet protection tube, henceforward simply defined sub-immersor nozzle, that has a semi-spherical conical concave shape at its top, which shape corresponds to the above said convex semi-spherical or conical bottom surface of the said element and a hole coaxial to the hole in said element of refractory material; the length of this sub-immersor nozzle is such that its bottom end remains immersed in the steel cast into the ingot mold. A conventional control means checks the position of said sub-immersor nozzle, together with a conventional counter-weight device that serves to keep the sub-immersor nozzle urged against said auxiliary nozzle with liquid steel sealing. The semi-spherical or conical coupling allows for the rotation of the sub-immersor nozzle, without it substantially lowering and then, by means of further shifts it can be removed from the underlying ingot mold without having to raise the above tundish. In particular the association between semi-spherical surfaces allows to perform the rotation, at a given angle, by sliding the sub-immersor nozzle on said refractory material element, followed by further shifts to remove said sub-immersor nozzle. Said control means may be a manipulator programmed to execute all the above operations, or else, only the rotation and a first shift that moves the sub-immersor nozzle away from said element in order to have the total removal performed by a person with the use of suitable tongs. Said refractory material element may be porous, so that it will be blown into, by means of a suitable pipe, with a chemically inert pressurized gas so as to create an over-pressure in the coupling area between the same element and the top of said sub-immersor nozzle to avoid the entry of air into the steel flow.
The main advantage of the improvements that are subject of the present invention is that of avoiding the possible contamination of the liquid steel casting during the passage from the auxiliary nozzle to the underlying ingot-mold without having to raise the tundish.
The present invention is described in further detail with reference to the drawings and in which

FIG. 1 is a first vertical part cross-section, and
FIG. 2 is a second vertical part cross-section.

FIG. 1 shows part of the bottom end of a tundish 1 with a nozzle 2 that bears an auxiliary nozzle 3 under its outlet port, the latter in turn bears on its bottom end, fixed with a liquid steel proof seal, a porous refractory material element 4 the bottom end of which is a convex semi-spherical surface and a hole 5 coaxial to the hole in the nozzle 3. Said semi-spherical surface is suitable for receiving a corresponding concave semi-spherical surface at the upper end of a sub-immersor nozzle 6. A conventional manipulator 7 is fixed to a ring 8 that holds the upper end of the sub-immersor nozzle 6 and is associated with an arm B that bears a counter-weight 9 at its free end, said arm B is hinged to C, so that said counter-weight keeps the sub-immersor nozzle 6 urged against element 4 with liquid steel sealing. During the removal stage of the sub-immersor nozzle 6, said manipulator provides a rotation to the same sub-immersor nozzle, said rotation has its centre coinciding with the centre of said semi-spherical surfaces and this separates and disconnects said sub-immersor nozzle from said element 4 by means of a first shift, then, by means of further shifts it removes said sub-immersor nozzle from the underlying ingot-mold, not shown in the Figure, without having to raise the above tundish.
Moreover, the figure shows a source of pressurized inert gas 10 and a pipe 11 that penetrates the element 4 so as to blow-into it inert gas in order to create an over-pressure in the contact area between element 4 and the top of sub-immersor nozzle 6 that will avoid the entry of air into the steel flow.
FIG. 2 shows an auxiliary nozzle 12, of a non visible tundish, that under its outlet port carries a refractory material element 13 that has a conical convex bottom surface with a hole 14 that is coaxial to the hole in the auxiliary nozzle 12. Said conical surface is suitable for receiving a corresponding concave conical surface of the top end of a sub-immersor nozzle 15. Said sub-immersor nozzle 15 is held by a ring 16 fixed to the end of an arm 17 hinged at C and carrying at the other end a counter-weight 18. The action of said counter-weight keeps the sub-immersor nozzle urged against said element 13 at liquid steel sealing pressure. During the removal stage of said sub-immersor nozzle, arm 17 is disconnected from the counter-weight 18 thus allowing the sub-immersor nozzle 13 to rotate downwards; at this point an operator, by means of suitable tongs extracts she sub-immersor nozzle from the underlying ingot mold, not visible in the figure, without having to raise the above tundish. The geometry of the above-mentioned concave and convex conical parts is such that the rotation of the sub-immersor nozzle 15 takes place without interfering with element 13.
It is clearly understood that the solution described in figure 2 involves operations, described above, that can be realized partly or totally by a conventional manipulator.

Claims

Improvements to a replaceable auxiliary nozzle (3) set under the nozzle (2) of a tundish (1) for the continuous casting of liquid steel into an underlying ingot mold characterized in that under the outlet port of the auxiliary nozzle (3) an element (4) of refractory material, is fixed, at liquid steel sealing pressure, bearing a hole (5) coaxial to the hole in the nozzle and that under said element a refractory material sub-immersor nozzle (6), of a length such that it may protect the jet of liquid steel directed into said ingot mold from contamination, is held by a conventional control means (7) at liquid steel sealing, that the contact surfaces between said element (4) and said sub-immersor nozzle (6) have a semi-spherical shape in order to allow the removal of said sub-immersor nozzle (6) from the underlying ingot mold without having to raise the above tundish (1), by means of rotation at a given angle imparted to the same sub-immersor nozzle, so that it will slide on said element (4) without lowering and with further shifting movements.
Improvements according to the Claim 1 characterized in that said refractory material element (14) has the bottom end surface that is conical convex in order to receive a corresponding conical concave surface of the upper end of the sub-immersor nozzle made of refractory material (15).
Improvements according to claims 1 and 2 characterized in that said refractory material element (4, 14) is porous so that it can be blown into by means of a tube (11) with a chemically inert pressurized gas so as to create an over-pressure in the coupling area between the same element (4, 14) and the upper end of said sub-immersor nozzle (6, 15) and thus avoid the entry of air into the steel flow.