EP0593383B1 - Apparatus for twin roll continuous casting of thin metallic products - Google Patents

Abstract

The apparatus for continuous casting, between rolls, of thin metallic products includes two rolls (1, 2) with parallel axes, which are cooled and driven in rotation, fixed walls (5, 7, 8) made from refractory material interacting with the said rolls in order to define, with them, a casting space (9) for liquid metal (10), and heating inductors (14, 32, 36) placed close to the fixed walls so as to heat, by means of induction, elements (12, 26, 34) made from electrically conductive material which are embedded in the said fixed walls which are made from electrically insulating material. <IMAGE>

Description

The present invention relates to a continuous casting device between cylinders of thin metallic products, in particular steel according to the preamble of claim 1.

Known devices for continuous casting between cylinders comprise two cooled cylinders, with parallel axes, driven in opposite directions, and fixed walls cooperating with the cylinders to define with them a liquid metal casting space.

Such fixed walls are commonly used to laterally seal the casting space towards the front ends of the cylinders, and to seal it; they are commonly called "lateral closing walls" or "small faces".

Certain devices such as that described in document FR-A-2 651 455 also include a kind of fixed riser, of generally rectangular shape, consisting of two longitudinal walls parallel to the axes of the cylinders and in sealed contact with them, and two front walls extending upwards or forming an integral part of the lateral closure walls. This enhancement, also called a "flyweight" in the aforementioned document and in the following description, has the particular function of delimiting the surface of the cylinder on which the solidification of the cast metal takes place, and thus ensuring the regularity of this solidification, whatever the level of the metal in the counterweight. In addition, since the meniscus of liquid metal is no longer in contact with the cylinders, the risk of entrainment of impurities floating on the meniscus is thus considerably reduced.

However, the cast metal is subjected to heat losses on contact with the fixed walls.

In the counterweight, these losses are accentuated at the meniscus, by radiation, and also in the angles, due to the proximity of two walls. In these areas, the cast metal tends to freeze and catch on walls, especially since the agitation of the metal, and therefore its renewal, is less. One solution is to make the counterweight from insulating refractory material. However, the mechanical resistance, in particular to wear, of these materials is low, and it is therefore necessary to be satisfied with a compromise between mechanical resistance and insulating power.

The same problems of freezing and hanging on the fixed walls are encountered at the level of the lateral obturation walls, for which it has also been recommended to use an insulating refractory material. It has also been proposed to compensate for heat losses, or even to reheat the cast metal, near the lateral obturation walls, by using inductors whose magnetic flux crosses the refractory wall and acts on the cast metal by reheating it by the Joule effect produced by the currents induced in said metal (JP-A-62-77156; JP-A-2-155543).

However, the use of such means leads to limiting the thickness of the refractory walls, to the detriment of their mechanical strength. In addition, it is difficult to use such means to act in areas of the casting space that are difficult to access (such as the area close to the neck between the cylinders), or variable (at the meniscus).

The purpose of the present invention is to provide a solution to the problems mentioned above, to avoid freezing and catching of the metal cast on the fixed walls, and thus to facilitate casting and improve the quality of the product obtained.

With these objectives in view, the invention relates to a continuous casting device between cylinders of thin metal products comprising two cylinders with parallel axes, cooled and driven in rotation, fixed walls of refractory material cooperating with said cylinders to define with them a liquid metal pouring space and heating inductors placed near the fixed walls.

According to the invention, the device is characterized in that it comprises elements made of conductive material electricity, embedded in said fixed walls of electrically insulating material and that the inductors are arranged so as to heat said elements by induction.

Thanks to the invention, it is possible to locate the heating in the areas of the fixed walls where said elements are placed, and in particular thanks to the diffusion of heat in these, in wall areas, and therefore of the cast metal. which is nearby, which could not be heated directly by induction. In addition, the inductors can be further from the casting space and the thickness of the walls increased compared to direct inductive heating according to the prior art. The mechanical resistance of the fixed walls is thereby improved, all the more since said elements can be made of a mechanically more resistant material than the refractory component of the walls.

According to a first particular arrangement of the invention, said fixed walls constitute lateral closing walls of the casting space. This arrangement makes it possible in particular to provide heating up to the proximity of the neck between the cylinders, where, due to the size of the inductors, it would be difficult to provide direct inductive heating of the cast metal.

According to another arrangement, which can be combined with the first, said fixed walls constitute a counterweight in which the conductive elements can in particular be placed at the level of the level provided for the cast metal, and thus locate the heating in the meniscus area, or in the corners of the counterweight, to compensate for the increase in thermal losses in these areas.

• les éléments conducteurs sont insérés dans des rainures réalisées dans les parois ;
• les parois fixes sont composées de deux plaques réfractaires entre lesquelles sont interposés les éléments conducteurs ;
• les éléments conducteurs sont des cornières placées dans les angles de la masselotte ;
• les éléments conducteurs sont constitués de treillis formant une armature pour le matériau réfractaire des parois ;
• les éléments conducteurs sont métalliques ;
• les éléments conducteurs sont en matériau réfractaire conducteur de l'électricité.

According to other characteristics, which can be combined:

• the conductive elements are inserted into grooves made in the walls;
• the fixed walls are composed of two refractory plates between which the conductive elements are interposed;
• the conductive elements are angles placed in the corners of the counterweight;
• the conductive elements consist of lattice forming a frame for the refractory material of the walls;
• the conductive elements are metallic;
• the conductive elements are made of refractory electrically conductive material.

Other characteristics and advantages will appear in the description which will be given of a continuous casting device between cylinders of thin steel products, in accordance with the invention.

• la figure 1 est une vue schématique en perspective d'un tel dispositif, utilisant une masselotte ;
• la figure 2 est une vue de dessus à échelle agrandie d'un angle de la masselotte ;
• la figure 3 est une vue en plan de la paroi d'obturation latérale ;
• la figure 4 est une vue en coupe selon la ligne IV-IV de la figure 3 ;
• la figure 5 est une vue de dessus d'une variante du dispositif de coulée, et
• la figure 6 est une vue en section selon la ligne VI-VI de la figure 5.

Reference is made to the appended drawings in which:

• Figure 1 is a schematic perspective view of such a device, using a weight;
• Figure 2 is a top view on an enlarged scale of an angle of the counterweight;
• Figure 3 is a plan view of the side closure wall;
• Figure 4 is a sectional view along the line IV-IV of Figure 3;
• FIG. 5 is a top view of a variant of the casting device, and
• Figure 6 is a sectional view along line VI-VI of Figure 5.

• deux cylindres 1, 2 de coulée refroidis, d'axes parallèles et entraînés en rotation de sens contraires selon les flèches 3, 4 ;
• deux parois fixes d'obturation latérale 5, et
• une rehausse, appelée masselotte 6, constituée d'un cadre fixe de forme rectangulaire dont les parois longitudinales 7 sont en contact glissant étanche avec les surfaces cylindriques des cylindres, et les parois transversales 8 surmontent les parois d'obturation latérale 5.

The device shown in Figure 1 includes:

• two cooled rolls 1, 2, of parallel axes and driven in rotation in opposite directions according to the arrows 3, 4;
• two fixed side closure walls 5, and
• an extension, called counterweight 6, consisting of a fixed rectangular frame whose longitudinal walls 7 are in sealed sliding contact with the cylindrical surfaces of the cylinders, and the transverse walls 8 surmount the lateral closure walls 5.

The set of fixed walls 5, 7, 8 defines, with the walls of the cylinders 1, 2, a casting space 9, in which the molten metal 10 is poured during casting, by a casting nozzle of known type and not shown. The metal, solidified in contact with the cylinders, is continuously extracted downwards in the form of a strip 11.

Elements made up of angles 12 of electrically conductive material are embedded in the counterweight 6, at the four corners of the latter and extend vertically above and below the level of the free surface of the liquid metal.

The walls 7, 8 are made of a thermally and electrically insulating refractory material. The angles 12 are made of metal with a high melting point or of an electrically conductive refractory material, such as silicon carbide.

Heating inductors 14 are placed outside the counterweight 6, and arranged so as to heat the angles 12 by induction.

As best seen in Figure 2, these inductors 14 have a "C" shape and are placed at the corners of the counterweight, so that their pole surfaces 16, 18 are respectively opposite the wings 20, 22 of the angles 12 To avoid overloading FIG. 1, a single inductor 14 has been shown there.

Other types of inductors can be used, insofar as they allow inductive heating of the angles 12. The latter are preferably inserted in grooves of corresponding dimensions made in the corners of the counterweight. The angles can also be embedded in the refractory walls during the manufacture of the counterweight by molding.

As will have already been understood, the angles heated by induction are brought to high temperature and, by conduction, heat the cast metal located in the corners of the casting space, or at least limit the heat losses.

• d'une première plaque 28 du côté de l'espace de coulée, plaquée contre les bords des cylindres, en matériau réfractaire dur résistant au frottement et au contact de l'acier ;
• d'une seconde plaque 30 en matériau réfractaire isolant thermique et électrique, parallèle à la première plaque 28, et
• de la plaque 26 en matériau conducteur insérée entre les deux plaques 28 et 30.

Other elements in the form of plates 24 of electrically conductive material are embedded in the lateral closure walls 5, and heated by inductors 26 (not shown in Figure 1 for the sake of clarity of this figure). The lateral closure wall 5 is represented in FIGS. 3 and 4, and composed:

• a first plate 28 on the side of the casting space, pressed against the edges of the cylinders, made of hard refractory material resistant to friction and to contact with steel;
• a second plate 30 of refractory thermal and electrical insulating material, parallel to the first plate 28, and
• of the plate 26 of conductive material inserted between the two plates 28 and 30.

An inductor 32 of the "pancake" type, that is to say wound in a flat spiral, is placed opposite the plate 30 to heat by induction the conductive plate 26, which will heat by conduction through the plate 28, the cast metal .

The hard refractory plate 28 is intended to avoid direct contact of the cast metal with the conductive plate 26.

The insulating refractory plate 30 is intended to prevent heat transfers from the cast metal and from the conductive plate 26 to the outside, and also to avoid excessive heating of the inductor 32.

In FIGS. 5 and 6, a variant of the invention is shown, for heating the cast metal at its free surface, over the entire periphery of the casting space.

In this variant, the counterweight 6 comprises, embedded in its walls, a metal belt 34 extending over the entire periphery of the counterweight. This belt 34 is formed of a wire mesh embedded in the refractory of the counterweight during its manufacture by molding and serving as a reinforcement reinforcing its mechanical resistance. The belt 34 is heated by induction by an inductor 36, for example wound in several turns surrounding the weight at the height of the belt 34.

• utilisation d'éléments conducteurs sous formes de treillis dans les parois d'obturation latérale ;
• utilisation d'éléments conducteurs sous forme de plaques dans les parois de la masselotte ;
• utilisation combinée de plaques et/ou treillis et de cornières ou autres profilés dans les parois d'obturation latérale ou les parois de la masselotte.

The invention is not limited to the two variants described above, and covers any combination of characteristics mentioned individually above, such as for example:

• use of conductive elements in the form of a trellis in the lateral closure walls;
• use of conductive elements in the form of plates in the walls of the counterweight;
• combined use of plates and / or trellis and angles or other profiles in the lateral obturation walls or the walls of the counterweight.

Claims (10)

1. Device for the twin-roll continuous casting of thin metal products, comprising two rolls (1, 2) having parallel axes, the rolls being cooled and rotationally driven, fixed walls (5, 7, 8) made of refractory material which interact with the said rolls in order to define with them a casting space (9) for liquid metal (10), and heating inductors (14, 32, 36) placed in proximity to the fixed walls, characterized in that it comprises elements (12, 26, 34) made of an electrically conducting material which are embedded in the said fixed walls made of electrically insulating material and in that the inductors are arranged so as to heat the said elements by induction.
2. Device according to Claim 1, characterized in that the said fixed walls form side closure walls (5) of the casting space.
3. Device according to Claim 1, characterized in that the said fixed walls form the walls (7, 8) of a feeder head (6).
4. Device according to Claim 3, characterized in that the conductive elements (34) are placed at the height of the level provided for the cast metal (10).
5. Device according to Claim 3, characterized in that the conductive elements (12) are placed in the corners of the feeder head (6).
6. Device according to Claim 5, characterized in that the conductive elements are angle sections (12) placed in the corners of the feeder head.
7. Device according to Claim 1, characterized in that the conductive elements (12) are inserted into grooves made in the fixed walls.
8. Device according to Claim 1, characterized in that the fixed walls are composed of two refractory plates (28, 30) between which the conductive elements (26) are interposed.
9. Device according to Claim 1, characterized in that the conductive elements consist of a lattice (34) forming a reinforcement for the refractory material of the walls (7, 8).
10. Device according to Claim 1, characterized in that the conductive elements (12, 26, 34) are metallic or made of an electrically conductive refractory material.

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