LU82093A1 - PROCESS FOR IMPROVING THE HOLDING OF CONTINUOUS CASTING METAL NOZZLES AND NOZZLE OBTAINED BY MEANS OF THIS PROCESS - Google Patents

Description

r;! C 2003/8001.

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Ij i j METALLURGICAL RESEARCH CENTER - îij CENTRUM V00R RESEARCH IN DE METALLURGIE,

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'j Non-profit association - vereniging zonder winstoogmerk j | in BRUXELLES, (Belgium).

ij Improving the behavior of the pouring nozzles | metal continuous and nozzle obtained by this process.

: | ] | The present invention relates to a method of *

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j improvement of the resistance of the continuous metal casting nozzles, and especially of the continuous steel casting nozzles.

j ij We know that in continuous casting processes

Ides metals, such as for example steel, the elaborate metal is poured into a suitable container, called a distribution basket, out of which it flows continuously in a mold of ijj pouring, via a special outlet tube known as the nozzle. When the steel is cast in a relatively large format, the steel-air interface is protected! i ί 2.- with a melting powder and, under these conditions, during the entire casting operation, the lower end of this nozzle plunges below the level of the metal contained in the mold.

The nozzle is most often made up of a | I * „combination of refractory materials with a particularly high melting point.

! Such a nozzle must withstand not only! thermal stresses due to the temperature of the metal, cast, but also to any chemical attack which may come from it, to the mechanical effects due to the movements of the metal bath and to erosion by the covering powder generally deposited on the upper surface liquid metal in the ingot.

It must in addition, and this is the object of the present invention, be protected as much as possible against any phej | closure nomene, for example non-metallic inclusions, in particular by alumina or aluminates (in the case of steel steels quenched with aluminum).

In fact, the plugging has the effect of disturbing the smooth running of the casting and of affecting the quality of the steel * cast, since it requires slowing down the extraction speed, ie j <'to burn the inside of the nozzle, either to change the nozzle or basket. At worst, it obliges to definitively stop the casting. To the knowledge of the applicant, no genuinely effective process has, to date, been proposed to reduce the disadvantage indicated above. We only know injections! neutral or inert gas through the nozzle, which has the effect! to delay the blockage.

i | ! The present invention specifically relates to a method for improving the holding of a pouring nozzle and which has the effect of making the plugging of said nozzle much slower and much less important, therefore reducing or eliminating the disadvantages. related to it.

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The process which is the subject of the present invention is essentially characterized in that a layer of very finely divided material intended to prevent the deposition of non-metallic inclusions is deposited on the internal face of the refractory of which the nozzle consists. on said face thus promoting the prolonged passage of the metal, without reduction in section due to the deposit of said inclusions.

In practice, the laying of this layer can be carried out advantageously in several ways, for example by spraying a fluid which either contains the said material in suspension or in solution (possibly colloidal in whole or in part), * or is constituted of a liquid form of this material (for example a salt thereof), these operations are optionally followed by a drying or dehydration operation (with or without decomposition) which makes the desired material appear in the finely divided form desired. The projection can also take place dry (hot or cold), followed by possible cooking.

The impregnation technique can also be advantageously used, in particular under vacuum.

According to an advantageous variant of this process, the material to be deposited on the nozzle is sprayed there in the hot state, or melted, by means of a torch which may be of the plasma type.

According to an advantageous variant of the invention, the material with which the internal wall of the nozzle refractory is covered consists mainly or comprises anti-wetting products, such as ZrO 2 and / or finely divided boron nitride and / or possibly linked to carbon.

In addition, these anti-wetting products will be deposited and treated so as to significantly reduce the roughness of said face, which facilitates the passage of steel and reduces the tendency to catch and therefore clog the steel. This property is obtained by subjecting the anti-wetting products to an operation, preferably in situ, of polishing and / or super baking ...............

Claims (6)

1. A method of improving the resistance of the nozzles * of continuous metal casting, characterized in that the internal face of the refractory of which the nozzle is made up is covered, with a layer of a very finely divided material, intended to prevent the deposition of non-metallic inclusions on said face. 2. Method according to claim 1, characterized in that the laying of said layer is done for example by spraying a fluid which either contains said material in suspension or in solution (possibly colloidal in whole or in part), or is made up of a liquid form of this material (for example a salt thereof), these operations possibly being followed by a drying or dehydration operation (with or without decomposition). 3. Method according to claim 2, characterized in that the spraying is done dry, hot or cold and is optionally followed by a cooking operation. * 4. Method according to claim 1, characterized in that the covering is done by impregnation, advantageously under vacuum. 5. Method according to either of claims 1 and 2, characterized in that the material to be deposited on the nozzle is sprayed there in the hot or molten state, by means of a torch which may be a plasma torch . 1 Method according to either of Claims 1 and 5, characterized in that the material with which the nozzle is covered consists mainly or comprises anti-wetting components 5.- *, such as for example Zr02 and / or Finely divided Cr.jû and / or boron nitride, possibly linked to carbon. 7. Method according to claim 6, characterized in that the said anti-wetting components are subjected to an operation, preferably in situ, of polishing and / or surface baking and / or sintering. i '%