EP1225245A1 - Process for preventing the entrainment of zinc particles on a galvanized sheet - Google Patents

Process for preventing the entrainment of zinc particles on a galvanized sheet Download PDF

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Publication number
EP1225245A1
EP1225245A1 EP01870010A EP01870010A EP1225245A1 EP 1225245 A1 EP1225245 A1 EP 1225245A1 EP 01870010 A EP01870010 A EP 01870010A EP 01870010 A EP01870010 A EP 01870010A EP 1225245 A1 EP1225245 A1 EP 1225245A1
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EP
European Patent Office
Prior art keywords
chute
zinc
plates
carbon
bath
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP01870010A
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German (de)
French (fr)
Inventor
Michel Dubois
Michel Tombu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ArcelorMittal Liege Upstream SA
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Cockerill Sambre SA
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Publication date
Application filed by Cockerill Sambre SA filed Critical Cockerill Sambre SA
Priority to EP01870010A priority Critical patent/EP1225245A1/en
Priority to EP02711660A priority patent/EP1352099B1/en
Priority to PCT/BE2002/000006 priority patent/WO2002057505A1/en
Priority to ES02711660T priority patent/ES2294119T3/en
Priority to AT02711660T priority patent/ATE378437T1/en
Priority to DE60223492T priority patent/DE60223492T2/en
Publication of EP1225245A1 publication Critical patent/EP1225245A1/en
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/003—Apparatus
    • C23C2/0034—Details related to elements immersed in bath
    • C23C2/00348—Fixed work supports or guides

Definitions

  • the present invention relates to a new process to avoid or control the training of solid compounds containing zinc, under form of oxides and / or lumps, floating on the surface of the liquid, when hot coating a steel sheet with soaking in a galvanizing bath.
  • These particles could be, for example, compounds of Fe 2 Al 5 , Al 2 O 3 , ZnO or a mixture of these in combination with metallic zinc.
  • the point defects observed generally have an area of less than 6 mm 2 but they can be arranged in "strings", that is to say form a series of local defects more or less aligned in the direction of travel of the sheet.
  • the present invention aims to provide a chute, which by construction prevents particles from zinc to accumulate at the mooring line.
  • a further aim of the invention is to provide a solution compatible with chutes existing or requiring little change important of these.
  • Another aim of the invention is to provide a simple and inexpensive solution.
  • the present invention relates to a chute for the entry of a steel sheet into a bath zinc-containing liquid metal in a process for hot coating, said chute preferably being under a reducing or mentally non-oxidizing atmosphere for iron, characterized in that said chute is covered or protected, in whole or in part, at the level of the wetting line of the liquid metal, by means making its internal surface non-wettable with respect to said bath.
  • said chute has a section essentially rectangular and said means not wettable are arranged at least at each of the longer sides of the chute, on both sides on the other side of said steel sheet.
  • said chute has a section essentially rectangular and said means not wettable are arranged only at the side of greater length of the chute, on the side of the sheet of steel where the internal surface of said chute forms a essentially acute angle with the wetting surface.
  • said means are carbon or ceramic plates.
  • said means are plates made of a material covered with carbon, ceramic or other material wettable by liquid zinc.
  • said material not wettable by liquid zinc is a molybdenum-tungsten alloy.
  • said carbon-based plates include graphite, sintered carbon, impregnated or not, or reinforced carbon fiber.
  • said plates are fixed mechanically to said chute directly by means of bolts.
  • said plates are fixed mechanically to said chute by means of angles screwed or welded.
  • said ceramic plates consist of a single piece machined in the mass or consist of several assembled parts or nested.
  • Another aspect of the present invention relates to a method for avoiding entrainment of zinc particles on a steel sheet, in a hot-dip galvanizing system, presenting a chute as described above.
  • This process includes a step of penetration of said sheet into a molten zinc bath, in the presence of salt particles or zinc oxides or other metals floating on the line wetting, without adhering to said sheet or to the surface internal of said chute.
  • Figure 1 schematically shows a sectional view of a trunking type installation galvanized steel, according to the state of the art.
  • Figures 2.a and 2.b show schematically the contact angle of a drop of a respectively wetting and non-wetting liquid with a horizontal flat surface.
  • Figure 3.a shows schematically a sectional view of a first embodiment of chute galvanizing steel, according to the invention.
  • Figure 3.b shows schematically a sectional view of a second embodiment of chute of galvanizing steel, according to the invention.
  • Figure 4 shows the detail of a first embodiment of ceramic plates according to the invention.
  • Figure 5 shows the detail of a second embodiment of the ceramic plates according to the invention.
  • Figure 1 shows schematically the configuration of a classic entry 2 chute sheet steel 3 in a galvanizing bath 1. Faults due to entrainment of zinc particles accumulate more particularly on the rear side 4.
  • the part internal of chute 5 above the surface of anchorage 6 is generally in an atmosphere reducing for iron and composed for example of hydrogen mixed with an inert gas such as nitrogen.
  • the chute is always made of metal, for example stainless steel, for cost reasons, of implementation and assembly, as well as to guarantee airtightness.
  • the most commonly used is therefore stainless steel, and in in particular grade 316L, for its known resistance to attack with liquid zinc.
  • This material has nevertheless the disadvantage, like any metal for that matter, of being wetted by liquid zinc.
  • the present invention consists in providing modifications to the construction of the internal part of the chute, located at the mooring line.
  • the principle is to cover or protect, possibly in the form of an interposition between the bath and the chute, the inner submerged part of the chute by elements or plates 7 of non-material wettable with zinc ( Figures 3.a and 3.b). In these conditions, the zinc particles can no longer build up at the mooring line.
  • a wetting liquid as being a liquid whose angle of contact ⁇ of a drop 10 with a horizontal surface given, wetted by this liquid, does not exceed 45 °, in oxidizing and / or reducing quenching conditions for the iron, even after several days of use (Figure 2.a).
  • the contact angle is greater than 45 °, the liquid is considered non-wetting ( Figure 2.b).
  • the angle of contact ⁇ is itself defined as the angle formed, the side of drop 10, by the tangent T to the surface of contact of the drop 10 with said horizontal surface wet ( Figures 2.a and 2.b).
  • the microscopic particles the formation of which is inevitable due to the physico-chemistry of the process, are trained in permanence due to their small size and cannot accumulate.
  • the elements or plates 7 used in the invention are either based on ceramic material, that is to say a combination of oxides and / or carbides, i.e. based on carbon compounds such as graphite and its many variations, such as sintered carbon, impregnated or not, fiber reinforced, etc.
  • Carbon is a particularly material advantageous for a preferred embodiment of the invention, insofar as, in addition to being non wettable for liquid zinc, it advantageously allows to avoid oxidation - or even to favor reduction - liquid metal at the mooring line 6. Besides the fact to possess a reducing power well known to man art, carbon is still anticorrosive to liquid metals.
  • the present invention is not limited to examples of plates described but relate to any material not wettable by zinc which can be used (sulphides, fluorides, special alloys, etc.). So it is good known to those skilled in the art that molybdenum-tungsten alloys are not wettable by zinc.
  • the atmosphere inside the chute is generally required to be oxidizing for the liquid metal (while of course remaining non-oxidizing for the iron), for example in the form of an injected oxidizing gas such as nitrogen. or wet hydrogen, possibly supplemented with oxygen and carbon dioxide, in order to avoid the formation of zinc vapors above the wetting line, which favor the appearance of the aforementioned defects on the sheet.
  • an injected oxidizing gas such as nitrogen. or wet hydrogen, possibly supplemented with oxygen and carbon dioxide, in order to avoid the formation of zinc vapors above the wetting line, which favor the appearance of the aforementioned defects on the sheet.
  • oxidizing agent O 2 or H 2 O or CO 2
  • the gas injected into the chute must have a more oxidizing power than in the absence of these plates, typically for example an H 2 / H 2 O ratio, or equivalent (H 2 + CO) / (H 2 O + CO 2 ), preferably varying from 5 to 25, in order to obtain the oxidation of the liquid metal on the surface itself, as desired, in order to prevent formation vapors described above.
  • Another feature of the invention is to use a mechanical fixing of said plates 7 of ceramic or carbon.
  • This type of attachment thus allows the free expansion of the different materials, one by compared to others. More specifically, said attachment is for example of the screwed or welded angle type 8 ( Figure 3.a) or direct fixing by bolts 9 ( Figure 3.b).
  • Ceramic plates can be made either in one piece with machining in the mass (figure 4), or in several pieces (figure 5). These plates can be fixed against the chute or present a space with the chute, where the liquid zinc can circulate freely. They can still be made up of several layers of different properties, such as a heat reflecting layer on one side of the plate.

Abstract

A spout for inlet of steel sheet into a bath of liquid metal containing zinc in a hot coating process, the spout being under a reducing or non-oxidizing atmosphere, is covered or protected, wholly or partially, at the liquid metal moistening level by ceramic or carbon based plates (7) rendering the inner surface non-wettable with respect to the bath. An Independent claim is included for a method for preventing the entrainment of zinc particles on a steel sheet in a galvanizing installation using this inlet spout.

Description

Objet de l'inventionSubject of the invention

La présente invention se rapporte à un nouveau procédé permettant d'éviter ou de contrôler l'entraínement de composés solides contenant du zinc, sous forme d'oxydes et/ou de mottes, flottant à la surface du liquide, lors du revêtement à chaud d'une tôle d'acier par trempage dans un bain de galvanisation.The present invention relates to a new process to avoid or control the training of solid compounds containing zinc, under form of oxides and / or lumps, floating on the surface of the liquid, when hot coating a steel sheet with soaking in a galvanizing bath.

Etat de la techniqueState of the art

En galvanisation à chaud, l'entraínement de particules contenant du zinc (oxydes, sels, etc.) au sein du revêtement d'une tôle galvanisée lors de son passage dans le bain de zinc et de son essorage est en général assez fréquent.In hot-dip galvanizing, the drive of particles containing zinc (oxides, salts, etc.) within of the coating of a galvanized sheet during its passage in the zinc bath and its spin is usually quite common.

Ce problème induit des défauts rédhibitoires pour le client lorsqu'une très haute qualité de surface est requise, comme c'est par exemple le cas pour les pièces de peau des carrosseries automobiles.This problem leads to unacceptable defects for the customer when a very high surface quality is required, as is the case for parts of skin of automobile bodies.

Des études relatives à la caractérisation de ces particules ont montré qu'il pouvait s'agir par exemple de composés de Fe2Al5, Al2O3, ZnO ou d'un mélange de ceux ci en combinaison avec du zinc métallique. Les défauts ponctuels observés présentent généralement une surface de moins de 6 mm2 mais ils peuvent être disposés en "chapelets", c'est-à-dire former une série de défauts locaux plus ou moins alignés dans le sens de défilement de la tôle.Studies relating to the characterization of these particles have shown that they could be, for example, compounds of Fe 2 Al 5 , Al 2 O 3 , ZnO or a mixture of these in combination with metallic zinc. The point defects observed generally have an area of less than 6 mm 2 but they can be arranged in "strings", that is to say form a series of local defects more or less aligned in the direction of travel of the sheet.

L'examen des conditions de galvanisation a montré que l'apparition des défauts en question résulte de l'entraínement brutal dans le zinc liquide d'amas de particules flottant à la surface du bain, au niveau de la zone de mouillage de la tôle, nettoyée et réduite par les processus amont. Cette zone est appelée par l'homme de l'art "sabot" ou "joint liquide".Examination of the galvanizing conditions has shown that the appearance of the defects in question results from the brutal entrainment in the liquid zinc of mass of particles floating on the surface of the bath, at the level of the sheet wetting area, cleaned and reduced by upstream process. This area is called by human "shoe" or "liquid joint" art.

Ces particules flottantes viennent soit des mattes formées dans le bain et qui remontent à la surface de par leur plus faible densité, soit de l'oxydation de la surface libre du bain de zinc, malgré la présence d'hydrogène dans la goulotte (également appelée trompe).These floating particles come either from mattes formed in the bath and which rise to the surface due to their lower density, i.e. the oxidation of the free surface of the zinc bath, despite the presence hydrogen in the chute (also called a trunk).

L'expérience a permis d'observer les points suivants :

  • les défauts sont plus nombreux sur la face arrière de la tôle, celle-ci étant définie par rapport à un opérateur placé en face du bain de zinc. La face arrière correspond également à l'endroit où l'angle formé par la surface interne de la goulotte et la surface du bain est essentiellement aigu. Cet angle aigu induit des conditions favorables d'entraínement des particules ;
  • les défauts apparaissent généralement par "paquets", lorsqu'en particulier la surface du zinc est agitée. Ce remous se produit par exemple en présence d'une mauvaise planéité de bande, de démattage de la surface à l'air libre ou encore lorsqu'on procède au chargement d'un lingot de zinc ;
  • le remous décrit ci-dessus induit un décollement de particules au niveau de la ligne de mouillage. Celles-ci ne peuvent sortir de la zone confinée de la goulotte que par entraínement sur la tôle ;
  • ce décollement des particules ne présente un défaut, lors des utilisations ultérieures du produit, que si les particules présentes finalement sur la tôle sont de taille suffisante.
The experience made it possible to observe the following points:
  • faults are more numerous on the rear face of the sheet, the latter being defined with respect to an operator placed in front of the zinc bath. The rear face also corresponds to the place where the angle formed by the internal surface of the chute and the surface of the bath is essentially acute. This acute angle induces favorable conditions for particle training;
  • the defects generally appear in "bundles", when in particular the surface of the zinc is agitated. This eddying occurs for example in the presence of a poor flatness of the strip, of dematting of the surface in the open air or even when a zinc ingot is loaded;
  • the swirl described above induces a separation of particles at the level of the wetting line. These can not leave the confined area of the chute only by training on the sheet;
  • this separation of the particles only presents a defect, during subsequent uses of the product, only if the particles finally present on the sheet are of sufficient size.

Dans le but de réduire la surface d'évaporation du zinc, on a proposé l'utilisation d'objets en céramique flottant à la surface du bain de zinc liquide et recouvrant au moins en partie sa surface.In order to reduce the surface of zinc evaporation, we proposed the use of objects ceramic floating on the surface of the liquid zinc bath and at least partially covering its surface.

Certains ont essayé de revêtir la face intérieure de la goulotte par des projections diverses sur celle-ci et entre autres céramiques. Ces traitements sont difficiles à réaliser parfaitement vu l'espace confiné lié à la faible ouverture de la pièce. En outre, ils subissent généralement un écaillage à cause, soit de leur porosité, soit de la forte dilatation différentielle entre le métal support, par exemple de l'inox austénitique, et la matière projetée.Some tried to put on the face inside of the chute by various projections on this and among other ceramics. These treatments are difficult to achieve perfectly given the confined space linked the small opening of the room. In addition, they suffer usually chipping because of either their porosity, either high differential expansion between the metal support, for example austenitic stainless steel, and the material projected.

On a encore proposé des méthodes pour l'extraction des impuretés de surface du bain utilisant des dispositifs tels que des pompes.We have also proposed methods for the extraction of impurities from the surface of the bath using devices such as pumps.

Buts de l'inventionAims of the invention

La présente invention vise à fournir une goulotte, qui par construction, empêche les particules de zinc de s'accumuler à la ligne de mouillage.The present invention aims to provide a chute, which by construction prevents particles from zinc to accumulate at the mooring line.

Un but complémentaire de l'invention est de fournir une solution compatible avec les goulottes existantes ou ne demandant que des modifications peu importantes de celles-ci.A further aim of the invention is to provide a solution compatible with chutes existing or requiring little change important of these.

Un but encore complémentaire de l'invention est de fournir une solution simple et peu onéreuse. Another aim of the invention is to provide a simple and inexpensive solution.

Principaux éléments caractéristiques de l'inventionMain characteristic features of the invention

La présente invention se rapporte à une goulotte pour l'entrée d'une tôle d'acier dans un bain de métal liquide contenant du zinc, dans un procédé de revêtement à chaud, ladite goulotte étant de préférence sous atmosphère réductrice ou franchement non-oxydante pour le fer, caractérisée en ce que ladite goulotte est recouverte ou protégée, en tout ou en partie, au niveau de la ligne de mouillage du métal liquide, par des moyens rendant sa surface interne non mouillable vis-à-vis dudit bain.The present invention relates to a chute for the entry of a steel sheet into a bath zinc-containing liquid metal in a process for hot coating, said chute preferably being under a reducing or frankly non-oxidizing atmosphere for iron, characterized in that said chute is covered or protected, in whole or in part, at the level of the wetting line of the liquid metal, by means making its internal surface non-wettable with respect to said bath.

Selon une première forme d'exécution préférentielle, ladite goulotte présente une section essentiellement rectangulaire et lesdits moyens non mouillables sont disposés au moins au niveau de chacun des côtés de plus grande longueur de la goulotte, de part et d'autre de ladite tôle d'acier.According to a first embodiment preferential, said chute has a section essentially rectangular and said means not wettable are arranged at least at each of the longer sides of the chute, on both sides on the other side of said steel sheet.

Selon une deuxième forme d'exécution préférentielle, ladite goulotte présente une section essentiellement rectangulaire et lesdits moyens non mouillables sont disposés uniquement au niveau du côté de plus grande longueur de la goulotte, du côté de la tôle d'acier où la surface interne de ladite goulotte forme un angle essentiellement aigu avec la surface de mouillage.According to a second embodiment preferential, said chute has a section essentially rectangular and said means not wettable are arranged only at the side of greater length of the chute, on the side of the sheet of steel where the internal surface of said chute forms a essentially acute angle with the wetting surface.

Avantageusement, lesdits moyens sont des plaques à base de carbone ou de céramique.Advantageously, said means are carbon or ceramic plates.

De manière particulièrement avantageuse, lesdits moyens sont des plaques constituées d'une matière recouverte de carbone, de céramique ou d'un matériau non mouillable par le zinc liquide.Particularly advantageously, said means are plates made of a material covered with carbon, ceramic or other material wettable by liquid zinc.

Toujours avantageusement, ledit matériau non mouillable par le zinc liquide est un alliage de molybdène-tungstène. Still advantageously, said material not wettable by liquid zinc is a molybdenum-tungsten alloy.

De manière particulièrement avantageuse, lesdites plaques à base de carbone comprennent du graphite, du carbone fritté, imprégné ou non, ou du carbone renforcé de fibres.Particularly advantageously, said carbon-based plates include graphite, sintered carbon, impregnated or not, or reinforced carbon fiber.

Selon une réalisation préférentielle du dispositif de l'invention, lesdites plaques sont fixées mécaniquement à ladite goulotte directement au moyen de boulons.According to a preferred embodiment of the device of the invention, said plates are fixed mechanically to said chute directly by means of bolts.

Selon une autre réalisation préférentielle du dispositif de l'invention, lesdites plaques sont fixées mécaniquement à ladite goulotte au moyen de cornières vissées ou soudées.According to another preferred embodiment of the device of the invention, said plates are fixed mechanically to said chute by means of angles screwed or welded.

De préférence, lesdites plaques en céramique sont constituées d'une seule pièce usinée dans la masse ou sont constituées de plusieurs pièces assemblées ou emboítées.Preferably, said ceramic plates consist of a single piece machined in the mass or consist of several assembled parts or nested.

Un autre aspect de la présente invention concerne un procédé pour éviter l'entraínement de particules de zinc sur une tôle d'acier, dans une installation de galvanisation d'acier à chaud, présentant une goulotte telle que décrite ci-dessus. Ce procédé comprend une étape de pénétration de ladite tôle dans un bain de zinc fondu, en présence de particules de sels ou d'oxydes de zinc ou d'autres métaux qui flottent à la ligne de mouillage, sans adhérer ni à ladite tôle ni à la surface interne de ladite goulotte.Another aspect of the present invention relates to a method for avoiding entrainment of zinc particles on a steel sheet, in a hot-dip galvanizing system, presenting a chute as described above. This process includes a step of penetration of said sheet into a molten zinc bath, in the presence of salt particles or zinc oxides or other metals floating on the line wetting, without adhering to said sheet or to the surface internal of said chute.

Brève description des figuresBrief description of the figures

La figure 1 représente schématiquement une vue en coupe d'une installation de type goulotte de galvanisation d'acier, selon l'état de la technique.Figure 1 schematically shows a sectional view of a trunking type installation galvanized steel, according to the state of the art.

Les figures 2.a et 2.b représentent schématiquement l'angle de contact d'une goutte d'un liquide respectivement mouillant et non mouillant avec une surface plane horizontale.Figures 2.a and 2.b show schematically the contact angle of a drop of a respectively wetting and non-wetting liquid with a horizontal flat surface.

La figure 3.a représente schématiquement une vue en coupe d'un première forme d'exécution de goulotte de galvanisation d'acier, selon l'invention.Figure 3.a shows schematically a sectional view of a first embodiment of chute galvanizing steel, according to the invention.

La figure 3.b représente schématiquement une vue en coupe d'une deuxième forme d'exécution de goulotte de galvanisation d'acier, selon l'invention.Figure 3.b shows schematically a sectional view of a second embodiment of chute of galvanizing steel, according to the invention.

La figure 4 représente le détail d'une première forme d'exécution des plaques en céramique selon l'invention.Figure 4 shows the detail of a first embodiment of ceramic plates according to the invention.

La figure 5 représente le détail d'une deuxième forme d'exécution des plaques en céramique selon l'invention.Figure 5 shows the detail of a second embodiment of the ceramic plates according to the invention.

Description d'une forme d'exécution préférée de l'inventionDescription of a preferred embodiment of the invention

La figure 1 montre schématiquement la configuration d'une goulotte classique 2 d'entrée d'une tôle d'acier 3 dans un bain de galvanisation 1. Les défauts dus à l'entraínement des particules de zinc s'accumulent plus particulièrement sur la face arrière 4. La partie interne de la goulotte 5 au-dessus de la surface de mouillage 6 se trouve sous atmosphère généralement réductrice pour le fer et composée par exemple d'hydrogène mélangé à un gaz inerte tel que l'azote.Figure 1 shows schematically the configuration of a classic entry 2 chute sheet steel 3 in a galvanizing bath 1. Faults due to entrainment of zinc particles accumulate more particularly on the rear side 4. The part internal of chute 5 above the surface of anchorage 6 is generally in an atmosphere reducing for iron and composed for example of hydrogen mixed with an inert gas such as nitrogen.

La goulotte est toujours construite en métal, par exemple en acier inoxydable, pour des raisons de coûts, de mise en oeuvre et d'assemblage, ainsi que pour garantir l'étanchéité à l'air ambiant. La matière la plus communément utilisée est donc l'acier inoxydable, et en particulier la nuance 316L, pour sa résistance connue à l'attaque par le zinc liquide. Cette matière a néanmoins l'inconvénient, comme tout métal d'ailleurs, d'être mouillée par le zinc liquide. The chute is always made of metal, for example stainless steel, for cost reasons, of implementation and assembly, as well as to guarantee airtightness. The most commonly used is therefore stainless steel, and in in particular grade 316L, for its known resistance to attack with liquid zinc. This material has nevertheless the disadvantage, like any metal for that matter, of being wetted by liquid zinc.

La présente invention consiste à apporter des modifications à la construction de la partie interne de la goulotte, se trouvant au niveau de la ligne de mouillage.The present invention consists in providing modifications to the construction of the internal part of the chute, located at the mooring line.

Le principe est de recouvrir ou protéger, éventuellement sous forme d'une interposition entre le bain et la goulotte, la partie immergée intérieure de la goulotte par des éléments ou plaques 7 en matière non mouillable par le zinc (figures 3.a et 3.b). Dans ces conditions, les particules de zinc ne peuvent plus s'accumuler à la ligne de mouillage.The principle is to cover or protect, possibly in the form of an interposition between the bath and the chute, the inner submerged part of the chute by elements or plates 7 of non-material wettable with zinc (Figures 3.a and 3.b). In these conditions, the zinc particles can no longer build up at the mooring line.

Dans le cadre de l'invention, on définit un liquide mouillant comme étant un liquide dont l'angle de contact  d'une goutte 10 avec une surface horizontale donnée, mouillée par ce liquide, n'excède pas 45°, dans des conditions de trempe oxydantes et/ou réductrices pour le fer, même après plusieurs jours d'utilisation (figure 2.a). Lorsque l'angle de contact est supérieur à 45°, le liquide est considéré comme non-mouillant (figure 2.b). L'angle de contact  est lui-même défini comme étant l'angle formé, du côté de la goutte 10, par la tangente T à la surface de contact de la goutte 10 avec ladite surface horizontale mouillée (figures 2.a et 2.b).In the context of the invention, a wetting liquid as being a liquid whose angle of contact  of a drop 10 with a horizontal surface given, wetted by this liquid, does not exceed 45 °, in oxidizing and / or reducing quenching conditions for the iron, even after several days of use (Figure 2.a). When the contact angle is greater than 45 °, the liquid is considered non-wetting (Figure 2.b). The angle of contact  is itself defined as the angle formed, the side of drop 10, by the tangent T to the surface of contact of the drop 10 with said horizontal surface wet (Figures 2.a and 2.b).

Ainsi, lors du défilement de la tôle, les particules microscopiques, dont la formation est inévitable de par la physico-chimie du procédé, sont entraínées en permanence de par leur petite taille et ne peuvent s'accumuler.Thus, when the sheet scrolls, the microscopic particles, the formation of which is inevitable due to the physico-chemistry of the process, are trained in permanence due to their small size and cannot accumulate.

Les éléments ou plaques 7 utilisés dans l'invention sont soit à base de matière céramique, c'est-à-dire une combinaison d'oxydes et/ou de carbures, soit à base de composés en carbone tels que le graphite et ses nombreuses variantes, telles que carbone fritté, imprégné ou non, renforcé de fibres, etc. The elements or plates 7 used in the invention are either based on ceramic material, that is to say a combination of oxides and / or carbides, i.e. based on carbon compounds such as graphite and its many variations, such as sintered carbon, impregnated or not, fiber reinforced, etc.

Le carbone est un matériau particulièrement avantageux pour un exemple de réalisation préférée de l'invention, dans la mesure où, en plus d'être non mouillable pour le zinc liquide, il permet avantageusement d'éviter l'oxydation -ou encore de favoriser la réduction- du métal liquide à la ligne de mouillage 6. Outre le fait de posséder un pouvoir réducteur bien connu de l'homme de l'art, le carbone est encore anticorrosif vis-à-vis des métaux liquides.Carbon is a particularly material advantageous for a preferred embodiment of the invention, insofar as, in addition to being non wettable for liquid zinc, it advantageously allows to avoid oxidation - or even to favor reduction - liquid metal at the mooring line 6. Besides the fact to possess a reducing power well known to man art, carbon is still anticorrosive to liquid metals.

La présente invention ne se limite pas aux exemples de plaques décrits mais concerne toute matière non mouillable par le zinc pouvant être utilisée (sulfures, fluorures, alliages spéciaux, etc.). Ainsi, il est bien connu de l'homme de l'art que les alliages molybdène-tungstène sont non mouillables par le zinc.The present invention is not limited to examples of plates described but relate to any material not wettable by zinc which can be used (sulphides, fluorides, special alloys, etc.). So it is good known to those skilled in the art that molybdenum-tungsten alloys are not wettable by zinc.

On impose généralement à l'atmosphère à l'intérieur de la goulotte d'être oxydante pour le métal liquide (tout en restant bien sûr non-oxydante pour le fer), par exemple sous la forme d'un gaz oxydant injecté tel que azote ou hydrogène humide, complété éventuellement d'oxygène et de dioxyde de carbone, afin d'éviter la formation de vapeurs de zinc au-dessus de la ligne de mouillage, qui favorisent l'apparition des défauts précités sur la tôle. Vu le caractère réducteur des plaques de carbone utilisées dans l'invention, on observe une plus grande consommation en agent oxydant (O2 ou H2O ou CO2) par rapport au cas classique dans l'état de la technique où ces éléments sont absents.The atmosphere inside the chute is generally required to be oxidizing for the liquid metal (while of course remaining non-oxidizing for the iron), for example in the form of an injected oxidizing gas such as nitrogen. or wet hydrogen, possibly supplemented with oxygen and carbon dioxide, in order to avoid the formation of zinc vapors above the wetting line, which favor the appearance of the aforementioned defects on the sheet. Given the reducing nature of the carbon plates used in the invention, there is a greater consumption of oxidizing agent (O 2 or H 2 O or CO 2 ) compared to the conventional case in the state of the art where these elements are absent.

Ainsi une production de CO est observée, conduisant à un redépôt de carbone et qui n'a d'ailleurs aucun effet néfaste sur le produit aux teneurs mesurées, à savoir entre 10 et 300 ppm, pour lesquelles la carburation des tôles d'acier ne peut se produire de manière significative. So a production of CO is observed, leading to a carbon redeposition and which has no harmful effect on the product at the measured contents, at know between 10 and 300 ppm, for which the carburetion steel sheets cannot occur so significant.

Il résulte de cette consommation, en présence de plaques réductrices 7, que le gaz injecté dans la goulotte doit avoir un pouvoir plus oxydant qu'en l'absence de ces plaques, typiquement par exemple un rapport H2/H2O, ou équivalent (H2+CO) / (H2O+CO2), variant de préférence de 5 à 25, afin d'obtenir l'oxydation du métal liquide à la surface même, tel que désiré, dans le but de prévenir la formation des vapeurs décrites précédemment.It follows from this consumption, in the presence of reducing plates 7, that the gas injected into the chute must have a more oxidizing power than in the absence of these plates, typically for example an H 2 / H 2 O ratio, or equivalent (H 2 + CO) / (H 2 O + CO 2 ), preferably varying from 5 to 25, in order to obtain the oxidation of the liquid metal on the surface itself, as desired, in order to prevent formation vapors described above.

Une autre caractéristique de l'invention est d'utiliser une fixation mécanique desdites plaques 7 de céramique ou carbone. Ce type de fixation permet ainsi la libre dilatation des différents matériaux les uns par rapport aux autres. Plus précisément, ladite fixation est par exemple de type à cornières vissées ou soudées 8 (figure 3.a) ou encore une fixation directe par boulons 9 (figure 3.b).Another feature of the invention is to use a mechanical fixing of said plates 7 of ceramic or carbon. This type of attachment thus allows the free expansion of the different materials, one by compared to others. More specifically, said attachment is for example of the screwed or welded angle type 8 (Figure 3.a) or direct fixing by bolts 9 (Figure 3.b).

Par ailleurs, les plaques de céramique peuvent être réalisées soit d'une seule pièce avec usinage dans la masse (figure 4), soit en plusieurs pièces (figure 5). Ces plaques peuvent être fixées contre la goulotte ou présenter un espace avec la goulotte, où le zinc liquide peut circuler librement. Elles peuvent encore être constituées de plusieurs couches de propriétés différentes, comme par exemple une couche réfléchissant la chaleur sur une face de la plaque.Furthermore, ceramic plates can be made either in one piece with machining in the mass (figure 4), or in several pieces (figure 5). These plates can be fixed against the chute or present a space with the chute, where the liquid zinc can circulate freely. They can still be made up of several layers of different properties, such as a heat reflecting layer on one side of the plate.

Claims (11)

Goulotte (2) pour l'entrée d'une tôle d'acier (3) dans un bain de métal liquide contenant du zinc (1), dans un procédé de revêtement à chaud, ladite goulotte (2) étant de préférence sous atmosphère réductrice ou franchement non-oxydante pour le fer, caractérisée en ce que ladite goulotte (2) est recouverte ou protégée, en tout ou en partie, au niveau de la ligne de mouillage du métal liquide (6), par des moyens (7) rendant sa surface interne non mouillable vis-à-vis dudit bain.Trough (2) for the entry of a steel sheet (3) into a bath of liquid metal containing zinc (1), in a hot coating process, said trough (2) preferably being in a reducing atmosphere or frankly non-oxidizing for iron, characterized in that said chute (2) is covered or protected, in whole or in part, at the level of the wetting line of the liquid metal (6), by means (7) making its internal surface which cannot be wetted with respect to said bath. Goulotte selon la revendication 1, caractérisée en ce qu'elle présente une section essentiellement rectangulaire et que lesdits moyens non mouillables (7) sont disposés au moins au niveau de chacun des côtés de plus grande longueur de la goulotte (2), de part et d'autre de ladite tôle d'acier (3).A chute according to claim 1, characterized in that it has an essentially rectangular section and that said non-wettable means (7) are arranged at least at each of the sides of the longer length of the chute (2), on both sides and on the other of said steel sheet (3). Goulotte selon la revendication 1, caractérisée en ce qu'elle présente une section essentiellement rectangulaire et que lesdits moyens non mouillables (7) sont disposés uniquement au niveau du côté de plus grande longueur de la goulotte (2), du côté (4) de la tôle d'acier où la surface interne de ladite goulotte (2) forme un angle essentiellement aigu avec la surface de mouillage (6).A chute according to claim 1, characterized in that it has an essentially rectangular section and that said non-wettable means (7) are arranged only at the side of the longer length of the chute (2), on the side (4) of the steel sheet where the internal surface of said chute (2) forms an essentially acute angle with the wetting surface (6). Goulotte selon l'une quelconque des revendications 1 à 3, caractérisé en ce que lesdits moyens (7) sont des plaques à base de carbone ou de céramique.A chute according to any one of claims 1 to 3, characterized in that said means (7) are plates based on carbon or ceramic. Goulotte selon l'une quelconque des revendications 1 à 3, caractérisée en ce que lesdits moyens (7) sont des plaques constituées d'une matière recouverte de carbone, de céramique ou d'un matériau non mouillable par le zinc liquide. A chute according to any one of claims 1 to 3, characterized in that said means (7) are plates made of a material covered with carbon, ceramic or a material not wettable by liquid zinc. Goulotte selon la revendication 5, caractérisée en ce que ledit matériau non mouillable par le zinc liquide est un alliage de molybdène-tungstène.A chute according to claim 5, characterized in that said material not wettable by liquid zinc is a molybdenum-tungsten alloy. Goulotte selon la revendication 4, caractérisée en ce que lesdites plaques à base de carbone (7) comprennent du graphite, du carbone fritté, imprégné ou non, ou du carbone renforcé de fibres.A chute according to claim 4, characterized in that said carbon-based plates (7) comprise graphite, sintered carbon, impregnated or not, or carbon reinforced with fibers. Goulotte selon l'une quelconque des revendications 4 à 7, caractérisée en ce que lesdites plaques (7) sont fixées mécaniquement à ladite goulotte directement au moyen de boulons (9).Trunking according to any one of Claims 4 to 7, characterized in that the said plates (7) are mechanically fixed to the said trunking directly by means of bolts (9). Goulotte selon l'une quelconque des revendications 4 à 7, caractérisée en ce que lesdites plaques sont fixées mécaniquement à ladite goulotte au moyen de cornières vissées ou soudées (8).Trunking according to any one of Claims 4 to 7, characterized in that the said plates are mechanically fixed to the said trough by means of screwed or welded angles (8). Goulotte selon l'une quelconque des revendications 4 à 7, caractérisée en ce que lesdites plaques en céramique (7) sont constituées d'une seule pièce usinée dans la masse ou sont constituées de plusieurs pièces assemblées ou emboítées.A chute according to any one of claims 4 to 7, characterized in that said ceramic plates (7) consist of a single piece machined in the mass or consist of several pieces assembled or fitted. Procédé pour éviter l'entraínement de particules de zinc sur une tôle d'acier (3), dans une installation de galvanisation d'acier à chaud, présentant une goulotte (2) selon l'une quelconque des revendications précédentes, caractérisé en ce qu'il comprend une étape de pénétration de ladite tôle (3) dans un bain de zinc fondu (1), en présence de particules de sels ou d'oxydes de zinc ou d'autres métaux qui flottent à la ligne de mouillage (6) sans adhérer ni à ladite tôle ni à la surface interne de ladite goulotte.Method for preventing entrainment of zinc particles on a steel sheet (3), in a hot-dip galvanizing installation, having a chute (2) according to any one of the preceding claims, characterized in that '' it comprises a step of penetration of said sheet (3) into a bath of molten zinc (1), in the presence of particles of salts or oxides of zinc or other metals which float at the wetting line (6) without adhering either to said sheet or to the internal surface of said chute.
EP01870010A 2001-01-17 2001-01-17 Process for preventing the entrainment of zinc particles on a galvanized sheet Withdrawn EP1225245A1 (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
EP01870010A EP1225245A1 (en) 2001-01-17 2001-01-17 Process for preventing the entrainment of zinc particles on a galvanized sheet
EP02711660A EP1352099B1 (en) 2001-01-17 2002-01-16 Method for avoiding drag-in of zinc particles on galvanized sheet metal
PCT/BE2002/000006 WO2002057505A1 (en) 2001-01-17 2002-01-16 Method for avoiding drag-in of zinc particles on galvanized sheet metal
ES02711660T ES2294119T3 (en) 2001-01-17 2002-01-16 PROCEDURE TO AVOID DRAG OF ZINC PARTICLES ON A GALVANIZED SHEET.
AT02711660T ATE378437T1 (en) 2001-01-17 2002-01-16 METHOD FOR AVOIDING ZINC PARTICLE LOADING ON A GALVANIZED SHEET
DE60223492T DE60223492T2 (en) 2001-01-17 2002-01-16 METHOD FOR AVOIDING ZINC PARTICLE LOADING ON A GALVANIZED PLATE

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP01870010A EP1225245A1 (en) 2001-01-17 2001-01-17 Process for preventing the entrainment of zinc particles on a galvanized sheet

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EP1225245A1 true EP1225245A1 (en) 2002-07-24

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EP02711660A Expired - Lifetime EP1352099B1 (en) 2001-01-17 2002-01-16 Method for avoiding drag-in of zinc particles on galvanized sheet metal

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EP02711660A Expired - Lifetime EP1352099B1 (en) 2001-01-17 2002-01-16 Method for avoiding drag-in of zinc particles on galvanized sheet metal

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EP (2) EP1225245A1 (en)
AT (1) ATE378437T1 (en)
DE (1) DE60223492T2 (en)
ES (1) ES2294119T3 (en)
WO (1) WO2002057505A1 (en)

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JPS6386852A (en) * 1986-09-30 1988-04-18 Sumitomo Metal Ind Ltd Continuous hot dip metal coating device
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JPH0762512A (en) * 1993-08-19 1995-03-07 Daido Steel Co Ltd Method for decreasing amount of zinc vapor in snout for zinc-aluminum alloy plating
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JPS6386852A (en) * 1986-09-30 1988-04-18 Sumitomo Metal Ind Ltd Continuous hot dip metal coating device
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Also Published As

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ATE378437T1 (en) 2007-11-15
WO2002057505A1 (en) 2002-07-25
ES2294119T3 (en) 2008-04-01
DE60223492T2 (en) 2008-11-27
DE60223492D1 (en) 2007-12-27
EP1352099B1 (en) 2007-11-14
EP1352099A1 (en) 2003-10-15

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