FR2693135A1 - Continuous casting installation between moving walls, and casting method using the installation. - Google Patents

Abstract

The continuous casting installation comprises two cooled movable walls (1, 2) driven in scrolling, and fixed walls (8, 9) adjoining said movable walls and defining therewith a casting space (4) of a metal in fusion. At least one of said fixed walls comprises a plate (13) made of fibrous refractory material in contact with the casting space and means (11) for blowing this plate with a gaseous fluid. It is possible, at least before casting, to inject as gaseous fluid a combustible mixture whose combustion effects the heating of the fixed wall, and during casting, to inject a neutral gas to achieve inerting of the casting space.

Description

INSTALLATION OF CONTINUOUS CASTING BETWEEN MOBILE WALLS, AND

  CASTING METHOD USING THE INSTALLATION

  The present invention relates to the continuous casting of thin metal products between moving walls, in particular

between cylinders.

  It relates more particularly to an installation for this type of casting and a casting method using

such an installation.

  Such an installation comprises two cooled mobile walls driven in a scrolling manner, such as two cylinders cooled internally and driven in rotation in opposite directions, which define between them a casting space in which molten metal is poured, this metal solidifying in contact with the cooled walls and being pulled down from the installation during the movement

said movable walls.

  The casting space is further delimited by two fixed lateral closure walls and arranged against the edges of the mobile walls to laterally retain the liquid metal, and possibly by an insulating cover this casting space of the ambient atmosphere. , this cover resting on the side walls and in sliding contact with the movable walls. A problem known for a long time in this type of installation is the tendency of the cast metal to solidify in contact with the fixed side walls, and thus to form a "corner" of early solidified metal that can not be evacuated from below, because of the approach of the movable walls at the neck, that is to say the area where the spacing between said movable walls is

  minimum, and disrupts the proper operation of the installation.

  To avoid these problems, it has already been proposed to preheat and / or heat during casting, the side closure walls, so that the cast metal does not solidify on contact FR 2628993, for example, shows a installation in which said side walls constitute the wall of an oven equipped with Z 2 burners Such an arrangement is however cumbersome, and the hard refractory material plate constituting the side wall is, especially during a preheating before introduction of the molten metal in the casting space, subjected to high expansion stresses

  differential harmful to its durability.

  Another problem appearing in this type of casting is the high heat loss of the cast metal, due to the

  large metal surface exposed to the atmosphere.

  To solve this problem, it has already been proposed for example by the document FR 2654657, to cover the casting space by a cover of refractory material which reflects the heat radiation of the cast metal to the meniscus, thus limiting the risk of freezing of the This reheating effect is not, however,

always enough.

  In addition, it has also proved necessary to avoid pollution of the metal cast by the ambient atmosphere, and thus to minimize the space of

casting.

  The present invention aims to solve the various problems mentioned above, to ensure the heating or preheating of the fixed walls of the casting space, side sealing walls or upper closure wall, to avoid undesirable solidification metal cast on contact or on the surface, and

  also to inert said casting space.

  With these objectives in view, the subject of the invention is a continuous metal casting plant comprising two cooled moving walls driven in scrolling, and fixed walls adjoining said movable walls and defining therewith a casting space of a metal melt, characterized in that at least one of said fixed walls comprises a plate of fibrous refractory material in contact with the casting space and means for insufflation in this plate of a gaseous fluid, to

the casting space.

  The gaseous fluid can be a neutral gas, which ensures

the inerting of the casting space.

  The gaseous fluid may also be a combustible mixture, which diffuses through said plate by the porosity thereof, and the combustion of which occurs at the free surface of the plate, opposite to the surface located on the side comprising said means. The particular advantage resulting from the use of a fibrous material is that the fuel mixture is distributed throughout the plate and combustion therefore occurs over the entire free surface thereof in a manner similar to the combustion obtained. by the use of radiant panels in

  so-called "catalytic" heaters.

  According to a particular embodiment of the invention, said plate is situated above the casting space and constitutes a cover. By the same plate, it is possible, depending on the phase of the process, to inject a neutral gas to ensure the inerting of the casting space, or a combustible mixture

  to prevent cooling of the meniscus.

  According to another arrangement, each side closure wall comprises such a plate In this case, in addition to the heating or inerting functions mentioned above, the injection of the gaseous fluid and its distribution on the surface of the plate make it possible to create a against the pressure which opposes the ferrostatic pressure that the metal exerts on the lateral closing walls, and thus limits the friction of said metal on said wall For example the plate can be used in radiant panel, by injection of a mixture fuel, to ensure preheating before the start of the casting, or at the beginning of it, and then when the casting is in steady state, by replacing the fuel mixture

  by a neutral gas, ensure the counterpressure indicated below.

  above, and participate in the inerting of the casting space.

  According to other particular provisions of the installation according to the invention: said fixed wall comprises a tub-shaped sealed envelope whose edges are in contact with said plate, and which defines with the latter a cavity for distributing the fluid gaseous, the bowl comprising a conduit for supplying said gaseous fluid. the fibrous material consists of silico-aluminous fibers; the aluminosilicone fibers comprise from 40 to 60% of A 1203; the open porosity of the fibrous material is about 80%; the density of the fibrous material in a given area of the plate is a function of the location of this zone; the thickness of the plate in a given area of

  this is a function of the location of this area.

  The invention also relates to a method of continuous casting of a thin metal product between moving walls using an installation according to the invention, characterized in that at least before the beginning of the casting, is injected

  as a gaseous fluid a combustible mixture.

  The invention also relates to a method of continuous casting of a thin metal product between moving wall, using an installation according to the invention, characterized in that during the casting is injected as gaseous fluid

a neutral gas.

  According to particular provisions of the invention: the fuel mixture consists of natural gas and air or oxygen; the inert gaseous fluid is argon or nitrogen. Other features and advantages of the invention

  will appear in the description that will be made of a

  installation, according to the invention, continuous casting

  between rolls of thin steel products.

  Reference is made to the accompanying drawings in which Figure 1 is a partial sectional view of the casting installation between rolls; Figure 2 is a front view of a side closure wall of this installation; FIG. 3 is a sectional view along the line

III-III of Figure 2.

  The installation shown in FIG. 1 comprises two cylinders 1, 2 whose wall is internally cooled, driven in counter-rotation according to the arrows 3, and defining between them a casting space 4 in which, during the casting, the molten steel 5 is discharged by a nozzle 6, the solidified steel in contact with the cylinders being extracted downwards under

form of a thin product 7.

  Two fixed side closure walls 8 are arranged at each end of the casting space to hold the liquid metal 5, and kept in contact with each other.

  sliding with the edges of the cylinders.

  Another fixed wall forming a cover 9 for the casting space 4 is placed above the latter, in substantially sealed contact with the walls on the one hand

  lateral sealing and on the other hand the cylinders.

  The cover 9 comprises a bowl-shaped envelope 11 whose edges 12 enclose a plate 13 of fibrous refractory material. A hole 14 is formed in the bowl 11 and the plate 13, for the passage, substantially sealed, of the nozzle 6. 13 and the bowl it determines between them a cavity 20 connected by a conduit 15, on the one hand to a source of neutral gas 16, on the other hand to a source of a combustible gas mixture 17, which

  can be isolated by valves 18, 19.

  The refractory fibrous material consists of non-oriented aluminosilicone fibers, containing 40 to 90% alumina, and has a high open porosity of the order of 80%. This material is thermally insulating and has a high (greater than 90%) power of reflection

infrared radiation.

  FIG. 2 represents the lateral closing wall 8, which comprises a metal casing 21. The edges 22 of this casing are shaped so as to match the curvature of the rolls. A plate 23 made of fibrous refractory material is maintained, in a manner known per se, for example by gluing, between said edges 22, so as to provide a distribution cavity 30 between the plate 23 and the bottom of the envelope 21, which comprises a

  conduit 25 for supplying a gaseous fluid.

  We will now describe a way of using

  this installation Before the start of the pouring, that is,

  say before introducing the molten metal in the casting space, is fed to the closure walls 8 and the hood 9 in fuel gas, for example natural gas, optionally mixed with air This gas mixture is distributed in the cavities 20, 30 and infiltrates into the porosities of the fibrous material. The combustion of this gaseous mixture is initiated, which continues in the direct vicinity of the surface of the plates 13, 23 on the opposite side to the cavities 20, 30 '. then a heating of the material, located on the surface, whose temperature can rise to more than 1000 C By its high power of reflection of the infrared radiation and its low thermal conductivity, the

  fibrous material heats up essentially at the surface.

  At the beginning of the casting, the fixed surfaces of the lateral closing walls with which the molten metal will come into contact, are therefore already at a high temperature.

  and the tendency of the metal to solidify is therefore limited.

  After the start-up period, when the casting regime stabilizes, it can continue to inject into the fuel gas hood, the plate 13 continuing to operate in radiant panel and avoiding the solidification of the cast metal meniscus However, we replace the injection into the lateral closing walls of the fuel gas, by a neutral gas, for example argon, which creates, at the interface between said closure walls and the cast metal, a counterpressure opposing the pressure

ferrostatic of said metal.

  Advantageously, the fibrous material will be adapted to counterbalance as much as possible said ferrostatic pressure. To this end, the thickness of the plate 23 may be adapted, or its porosity may be adapted locally so as to promote the flow of gases in certain parts. of the plate, especially here in its lower part where the ferrostatic pressure is the largest. It will be noted that this adaptation of the thickness or porosity in certain zones of the plates as a function of the location of these zones may also be carried out so as to promote localized heating Whatever the effect sought, preferential localized heating or counterpressure it will be based on the fact that the gaseous flow at the free surface of the plate will be less in the areas thereof having a lower porosity or a greater thickness than in the areas having a porosity

  stronger or a lower thickness.

  It will also be noted that the invention also applies in the case where the casting installation does not comprise a hood, only the lateral closing walls being then

  made and used in accordance with the invention.

Claims (11)

  1) Continuous casting plant of metals comprising two scrollable moving scroll walls (1, 2) and fixed walls (8, 9) adjoining said movable walls and defining therewith a casting space (4) of a molten metal, characterized in that at least one of said fixed walls comprises a plate (13, 23) of fibrous refractory material in contact with the casting space and means (11, 21) of insufflation   in this plate a gaseous fluid.   2) Installation according to claim 1,   characterized in that said plate (13) is located   above the casting space and constitutes a hood.   3) Installation according to claim 1, characterized in that the fixed wall comprising a plate of fibrous refractory material is a closure wall lateral of the casting space.   4) Installation according to claim 1, characterized in that said fixed wall comprises a casing (11, 21) sealed bowl-shaped whose edges (12, 22) are in contact with said plate, and which defines with the latter a cavity (20, 30) for distributing the gaseous fluid, the bowl comprising a   conduit (15, 25) for supplying said gaseous fluid.   Installation according to claim 1, characterized in that the fibrous material consists of aluminous silico fibers.   6) Installation according to claim 1, characterized in that the aluminous silico fibers comprise from 40 to 90% of A 1203.   7) Installation according to claim 1, characterized in that the open porosity of the material fibrous is about 80%.   8) Installation according to claim 1, characterized in that the density of the fibrous material in a given area of the plate is a function of the location of this area.   9) Installation according to claim 1, characterized in that the thickness of the plate in a given zone thereof is a function of the location of this zone.   10) Process for continuous casting of a thin metal product between moving wall, using a   installation according to one of the preceding claims,   characterized in that during casting one injects as gaseous fluid a neutral gas.   11) Process according to claim 10, characterized in that the inert gaseous fluid is argon or nitrogen. 12) Process for continuous casting of a thin metal product between moving wall, using a   Installation according to one of the preceding claims, characterized in that, at least before casting, a combustible mixture is injected as a gaseous fluid.   13) Process according to claim 10, characterized in that the fuel mixture consists of gas naturale and air or oxygen.