FR2728185A1 - METHOD FOR APPLYING TO THE INNER SIDES OF A METALLURGICAL CONTAINER A PROTECTIVE COATING COMPRISING AT LEAST TWO LAYERS - Google Patents

Abstract

The method comprises the following steps: a) spraying on the permanent coating (3) of the container (1) a first protective layer (5) implemented by a wet-phase spraying process, b) heating the layer ( 5) thus obtained to harden it, c) a mold (7) is introduced inside the container (1) creating a molding space (8) between the walls of the mold (7) and the outer surface of the first layer (5), d) is introduced into the molding space (8) a powder material (9) consisting of inorganic particles pre-coated with a hardenable powder binder and / or mixed with a hardenable powder binder, said material being dry or practically dry, After the layer has hardened, said mold (7) is extracted from the container, leaving an outer protective layer (6) in place.

Description

The present invention relates to a method for applying to the faces

  internal parts of a metallurgical vessel for transferring liquid metal a consumable protective coating comprising at least two layers. The invention also relates to the coating obtained by this process and the

composition of this coating.

  French Patent Nos. 2,646,367 and 2,657,549 disclose a number of methods for applying a protective coating to the inner faces of a metallurgical vessel such as a tundish.

having at least two layers.

  Thus, French Patent No. 87757 describes a process for applying a coating comprising two layers to the inner faces of a tundish, this process comprising the following steps: A. A core is introduced into the metallurgical vessel to be protected. creating a molding space between the inner walls of said container and the outer walls of the core, B. is introduced into the molding space thus created a material consisting of inorganic particles resistant to temperature, said particles being precoated with a curable binder and / or mixed with a binder, said material being dry or substantially dry, C. After curing said material on the inner walls of the container, the core is removed from the container leaving on the spot a first outer layer of protection, D. on the first outer protective layer a second inner layer implemented by a process for the wet phase projection of a material consisting of inorganic particles resistant to the temperature of the liquid metal, E. The inner walls of the metallurgical vessel are heated to

  at least perfectly dry the protective coating thus deposited.

  According to this method, the first layer is formed in the space between the mold and the inner wall of the container, while the second layer is projected. The disadvantage of such a method lies in the fact that the second layer

  is projected as aqueous sludge.

  This layer is therefore wet; it is therefore necessary to dry it thoroughly before pouring the liquid metal into the container to avoid any risk of explosion resulting from the formation of hydrogen from the

  decomposition of water due to high temperature.

  On the other hand, because the second layer is wet, this layer can not contain a water-sensitive compound, such as quicklime which has a

  purifying function vis-à-vis the oxides contained in the liquid metal.

  The object of the present invention is to overcome these disadvantages.

  According to the invention, the method for applying to the inner faces of a metallurgical liquid metal transfer vessel, a consumable protective coating comprising at least two layers is characterized by the following steps: a) the permanent coating is sprayed onto the container a first protective layer implemented by a method of wet-spraying a material consisting of inorganic particles resistant to the temperature of the liquid metal and a heat-curable binder, b) heating the layer thus obtained c) is introduced inside the metallurgical vessel a preheated mold or heating creating a molding space between the outer walls of the mold and the outer wall of said first layer, d) is introduced into the molding space thus creating a powder material consisting of inorganic particles resistant to the temperature prevailing during the tr pouring the liquid metal, said particles being pre-coated with a curable powdery binder and / or mixed with a curable powdery binder, said material being dry or substantially dry, e) after curing, under the effect of the heat of the preheated or heating mold of said powdery material on the outer surface of said first layer, the preheated or heated mold is removed from the container, leaving on the spot

  a second outer layer of protection.

  Thus, according to the method according to the invention, only the first layer is wet, while the second layer intended to come into contact with the liquid metal is substantially dry, so that it can contain compounds sensitive to water,

  having purifying properties, such as quicklime.

  According to an advantageous version of the process, before placing the preheated or heated mold, the powdered material is applied to the first hardened layer in the bottom area of the container to form a second base layer and the side portions of the the second layer after

  introducing the preheated or heated mold into the container.

  According to a preferred version of the method, it is used to form the

  second layer of quicklime, a thermosetting binder and a flux.

  The quicklime can thus exert cleansing properties vis-à-vis the

  oxides contained in the liquid metal.

  The thermosetting binder contained in this layer, ensures after curing, under the effect of the heat exerted by the preheated mold or

  heating, the cohesion of the layer.

  The presence of a flux facilitates the sintering of this layer under the effect of the heat exerted by the liquid metal, and thus the maintenance of the cohesion of the

  layer during the residence time of the liquid metal in the container.

  Preferably, the first layer contains magnesia as

principal constituent.

  Also preferably, the particle size and the composition of the inorganic particles of the first layer are chosen so that said layer does not sinter or sintered weakly at the temperature prevailing during the course of the

  transferring the liquid metal into the container.

  Therefore, at the end of casting, the coating can detach very easily from the wall of the container, which greatly facilitates the cleaning thereof. According to another preferred version of the invention, the second layer is mixed with 5% to 60% by weight of elements capable of generating an exothermic reaction. This exothermic reaction helps to melt the quicklime and burn

  the carbon contained in the second layer.

  Other features and advantages of the invention will become apparent

in the description below.

  In the accompanying drawings, given by way of nonlimiting example: - Figure 1 is a schematic sectional view of a metallurgical vessel and the mold used for carrying out the method according to the invention, showing the projection step the first layer of the coating; FIG. 2 is a view similar to FIG. 1, showing the step of producing the second layer, after introduction of the heating mold into the container; FIG. 3 is a view similar to FIG. 2, showing a variant embodiment of FIG. the second layer; FIG. 4 is a sectional view of a container provided with its two layers and a gas burner for initiating the exothermic reaction in the second layer; FIG. 5 is a view similar to FIG. gas burner

  in the service position inside the container.

  In the embodiment of FIGS. 1 to 5, there is shown a continuous casting distributor 1 comprising an outer metal jacket 2 and a

  interior lining 3 in cement or refractory bricks.

  At the bottom of the distributor 1 is provided a pouring orifice provided with a

casting nozzle 4.

  The method for applying on the inner faces of the tundish 1 a consumable protective coating comprising two layers comprises the following steps: a) the permanent coating 3 of the container 1 is sprayed (see FIG. 1) with a first protective layer 5 by a method of wet-spraying a material consisting of inorganic particles resistant to the temperature of the liquid metal and a heat-curable binder, b) heating the layer thus obtained to harden it, c) a preheated or heated mold 7 is introduced into the metallurgical vessel 7 creating a molding space 8 between the outer walls of the mold 7 and the outer surface of the first layer 5, d) introduced into the molding space thus created a powder material 9 consisting of inorganic particles resistant to the temperature prevailing during the transfer of the liquid metal, the said particles being precoated with a curable powdery binder and / or mixed with a curable powdery binder, said material being dry or substantially dry; e) after curing on the effect of the heat of the preheated or heated mold 7 of said powder material on the outer surface of said first layer 5, the preheated or heated mold is removed from the container leaving

  place a second outer layer of protection 6.

  In the example of FIGS. 1 and 2, the mold 7 is metallic and is heated

  internally using gas burners 10.

  In the version shown in FIG. 3, prior to the introduction of the preheated or heated mold 7, the powdered material is applied to the first hardened layer 5 in the bottom area of the container to form a second base layer 6a and realizes the lateral parts of the second layer 6 after

  introduction of the preheated or heated mold 7 into the tundish 1.

  Preferably, to form the second layer 6 of quicklime, a thermosetting binder and a flux. This quicklime has a purifying function vis-à-vis the present oxides

  in the liquid metal poured into the distributor 1.

  The binder makes it possible, after curing, to ensure the initial cohesion of the layer 6, the fluxing agent facilitates the sintering under the effect of the heat and makes it possible to maintain the cohesion of the layer 6 throughout the stay of the metal

  liquid inside the tundish 1.

  Preferably, the first layer 5 contains magnesia as the main constituent. The proportion of magnesia is for example equal to 75% by weight. Also preferably, the particle size and the composition of the inorganic particles of the first layer 5 are chosen so that said layer does not sinter or sintered weakly at the temperature prevailing during the course of the

  transferring the liquid metal into the distributor 1.

  Thus, this layer 5 in contact with the permanent coating 2 does not adhere to the latter, so that at the end of casting, the coating is easily detached from

  the partition wall, which facilitates cleaning.

  Usually, the mold 7 is preheated or the mold is used

  heating to obtain a temperature between 400 and 800 C.

  This results in a hardening of the layer 6 intended to come into

contact with the liquid metal.

  It can be used to form the second layer 6 of quicklime

  precoated with a binder and / or mixed with an organic binder and / or inorganic.

  Moreover, at the time of introduction of the mold 7 into the metallurgical vessel, the position and / or the dimensions of the mold in the container are adjusted.

  to adjust the thickness of the second layer 6.

  According to an alternative embodiment of the process according to the invention, is mixed with the layer 6 intended to come into contact with the liquid metal and which comprises quicklime, between 5 and 6% by weight of element capable of generating a reaction exothermic. These elements may consist of magnesium and / or calcium supplemented with calcium nitrate and / or barium and / or aluminum as well as by

  example of calcium fluoride and / or magnesium and / or barium.

  After the extraction phase of the mold 7, for example using gas burners 10, the exothermic reaction which will melt the quicklime and

  burn the carbon of the organic binder contained in the second layer 6.

  This variant of the process according to the invention is illustrated by FIGS. 4 and 5. By way of nonlimiting example, the composition for making the coating coming into contact with the liquid metal to protect the inside of a liquid metal transfer vessel comprises the following compounds in the weight proportions indicated below: Mg et ou Ca / or Ca and / or AL 0 to 60% SiO2 0 to 3.5%

A1203 where4%

  CaO high O at 95% MgO and / or chromium Magnesia O at 50% Fe203 0 at 5% Na2O at 2.5% Loss on ignition at 1000 C 0 to 5%

P 0 to 7%

H 0 to 0.5%

B203 0 to 3%

K20 0 to 4%

H20 0 to 3%

C Total 0 to 6% Na 0 to 2.5%

K 0 to 1.80%

  H20 crystallization O at 3% Ca (NO3) 2 0 at 10% (No3) 2Ba O at 10% MgF2 O at 8% CaF2 O at 8% BaF2 0 at 8%%

Claims (13)

  A method for applying to the inner faces of a metallurgical metallurgical vessel (1) for transferring liquid metal a consumable protective coating comprising at least two layers (5, 6), characterized by the following steps: a. a first protective layer (5) is applied to the permanent coating (3) of the container (1) by means of a wet-phase projection process of a material consisting of inorganic particles resistant to the temperature of the liquid metal and a heat-curable binder, b. the layer (5) thus obtained is heated to harden, c. introducing into the metallurgical vessel a preheated or heated mold (7) creating a molding gap (81) between the outer walls of the mold (7), and the outer surface of said first layer (5), d. a powder material (9) consisting of inorganic particles resistant to the temperature prevailing during the transfer of the liquid metal is introduced into the molding space thus created, the said particles being precoated with a curable powdery binder and / or mixed with a curable powdery binder, said material being dry or substantially dry, e. after hardening, under the effect of the heat of the preheated or heated mold (7), said powdery material on the outer surface of said first layer, is extracted from the container, the preheated or heated mold leaving on   place a second outer layer of protection (6).   2. Method according to claim 1, characterized in that before the introduction of the preheated mold, or heating (7), is applied to the first hardened layer (5) in the bottom area of the container, said powder material to form a second base layer (6a) and the side portions of the second layer (6) are formed after introduction of the preheated or heated mold (7) into the container.   3. Method according to one of claims 1 or 2, characterized in that   used to form the second layer (6) of quicklime, a binder   thermosetting and possibly a flux.   4. Method according to one of claims I to 3, characterized in that   the first layer (5) contains magnesia as a constituent main.   5. Method according to one of claims 1 to 4, characterized in that   that the particle size and the composition of the inorganic particles of the first layer (5) are chosen so that said layer does not sinter or sintered only slightly at the temperature prevailing during the transfer of the liquid metal into the container (1).   6. Process according to one of claims 1 to 5, characterized in that   that the mold (7) is preheated or a heating mold is used to obtain a   temperature between 400 C and 800 C.   7. Process according to one of Claims 1 to 6, characterized in that   used to form the second layer (6) of quicklime pre-coated with a   binder and / or mixed with an organic binder and / or inorganic.   Process according to one of Claims 1 to 7, characterized in that   when the mold (7) is introduced into the metallurgical vessel, the position and / or the dimensions of the mold are adjusted in the container to regulate   the thickness of said second layer (6).   9. Process according to one of Claims 3 to 8, characterized in that   mixed with the second layer (6) elements that can generate an exothermic reaction. 10. Process according to claim 9, characterized in that said elements consist of magnesium and / or calcium and / or aluminum supplemented with calcium nitrate and / or barium, calcium fluoride and / or magnesium and / or barium and in that after the "e" extraction phase of the mold (7), the exothermic reaction is caused to sinter the lime and burn the   carbon of the organic binder contained in said second layer.   11. Coating for protecting the interior of a liquid metal transfer vessel, characterized in that it is obtained by means of the method according to   any of claims 1 to 9.   12. The coating according to claim 10, characterized in that it is applied inside a metallurgical container comprising a lining. permanent in refractory material.   13. Composition for making a coating coming into contact with the liquid metal to protect the inside of a liquid metal transfer vessel, according to claim 10, characterized in that it comprises the following compounds in the weight proportions indicated ci after: Mg and / or Ca and / or Al 0 to 60% SiO 2 0 to 3.5% A1203 where4%   95% MgO and / or chromium Magnesium 0% O2 Fe203 0 to 5% Na2 O2 2.5% Loss on ignition at 1000 C 0 to 5% P7% H 0.5 to 0.5% B203 0 to 3% I0 K20 O4% H20 0 to 3% C Total 0 to 6% Na 0 to 2.5% K O 1.80%   H20 crystallization O at 3% Ca (NO3) 2 0 at 10% (No3) 2Ba O at 10% MgF2 0 at 8% CaF2 0 at 8% BaF2 0 at 8%