FR2696960A1 - Continuous casting device between cylinders 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.

Description

CONTINUOUS CASTING DEVICE BETWEEN CYLINDERS OF PRODUCTS

THIN METALS

  The present invention relates to a continuous casting device between cylinders of thin metallic products,

especially steel.

  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 pouring 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 obturation walls" or

"little 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 of two front walls extending upwards or forming an integral part of the lateral closure walls This extension, also called a "flyweight" in the document

  above and in the following description, in particular for

  function of delimiting the cylinder surface 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, the meniscus of liquid metal being more in contact with the cylinders, the risk of entrainment of floating impurities

  on the meniscus is thus considerably reduced.

  But the cast metal is subjected to heat losses

in contact with the fixed walls.

  In the counterweight, these losses are accentuated at the level of 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 cling to the walls, d '' more so than the agitation of the metal, and therefore its renewal, is less there One solution is to produce the counterweight in insulating refractory material But the mechanical resistance, in particular to wear, of these materials is low, settle for a compromise between

  mechanical resistance and insulating power.

  The same problems of freezing and catching 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 the heat losses, or even reheating the cast metal, near the lateral obturation walls, using inductors whose magnetic flux crosses the refractory wall and acts on the cast metal by reheating it through 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. Furthermore, it is difficult to use such means to act in areas of the casting space that are difficult to access (such as the area near the pass

  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 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 electrically conductive material, 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 zones of the fixed walls where said elements are placed, and in particular thanks to the diffusion of heat in these, in wall zones, 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 Mechanical resistance fixed walls are improved, especially since said elements can be made of a mechanically stronger material than the refractory

composing the walls.

  According to a first particular arrangement of the invention, said fixed walls constitute lateral closure 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, o, due to the size of the inductors, it would be difficult to ensure

  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

  increased heat losses in these areas.

  According to other characteristics, which can be combined: the conductive elements are inserted in 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 material

conductor of electricity.

  Other characteristics and advantages will appear

  in the description which will be made of a device for

  continuous casting between cylinders of thin steel products,

according to the invention.

  Reference will be made to the appended drawings in which: FIG. 1 is a schematic perspective view of such a device, using a counterweight; 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.

  The device represented in FIG. 1 comprises: two cylinders 1, 2 of cooled casting, of parallel axes and driven in rotation in opposite directions according to the arrows 3, 4; two fixed side shutter 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 overcome the shutter walls

lateral 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 it 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 a refractory material which conducts electricity, such as carbide

of silicon.

  Heating inductors 14 are placed outside of the counterweight 6, and arranged so as to

  induction heating the angles 12.

  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 Figure 1, a single inductor

14 was represented 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 walls refractory at the time of

  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 losses.

thermal.

  Other elements in the form of plates 24 of electrically conductive material are embedded in the lateral obturation walls 5, and heated by inductors 26 (not shown in FIG. 1 for the sake of clarity of this figure) The obturation wall 5 is shown in FIGS. 3 and 4, and is composed of: 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 the conductive plate 26 by induction, 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 avoid thermal transfers of the cast metal and the conductive plate 26 to the outside, and also to avoid a

  excess temperature 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 strength The belt 34 is heated by induction by an inductor 36, for example wound in several turns surrounding the

  belt weight at the waist 34.

  The invention is not limited to the two variants described above, and covers any combination of the 7 characteristics mentioned individually above, such as for example: use of conductive elements in the form of lattices in the lateral obturation walls; use of conductive elements in the form of plates in the walls of the counterweight; combined use of plates and / or mesh and angles or other profiles in the obturation walls

  side or the walls of the counterweight.

Claims (7)

  1) device for continuous casting between cylinders of thin metallic products comprising two cylinders (1, 2) of parallel axes, cooled and driven in rotation, fixed walls (5, 7, 8) of refractory material cooperating with said cylinders to define with them a pouring space (9) of liquid metal (10) and heating inductors (14, 32, 36) placed near the fixed walls, characterized in that it comprises elements (12, 26, 34) of electrically conductive material, embedded in said fixed walls of electrically insulating material and the inductors are arranged so as to heat said elements by induction. 2) Device according to claim 1, characterized in that said fixed walls constitute walls   lateral closure (5) of the casting space.   3) Device according to claim 1, characterized in that said fixed walls constitute the walls (7, 8) a flyweight (6).   4) Device according to claim 3, characterized in that the conductive elements (34) are placed at the height of the   level provided for cast metal (10).   ) Device according to claim 3, characterized in that the conductive elements (12) are placed in the angles of the counterweight (6).   6) Device according to claim 5, characterized in that the conductive elements are angles (12)   placed in the corners of the counterweight.   7) Device according to claim 1, characterized in that the conductive elements (12) are inserted in   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 are interposed conductive elements (26).   9) Device according to claim 1 characterized in that the conductive elements consist of lattice (34) forming a frame for the refractory material of walls (7, 8).   ) Device according to claim 1 characterized in that the conductive elements (12, 26, 34) are metallic   or in an electrically conductive refractory material.