EP1358360B1 - Steel galvanizing method - Google Patents

Steel galvanizing method Download PDF

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EP1358360B1
EP1358360B1 EP01273287A EP01273287A EP1358360B1 EP 1358360 B1 EP1358360 B1 EP 1358360B1 EP 01273287 A EP01273287 A EP 01273287A EP 01273287 A EP01273287 A EP 01273287A EP 1358360 B1 EP1358360 B1 EP 1358360B1
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zone
oxidising
sheet
atmosphere
oxidizing
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German (de)
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EP1358360A1 (en
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Michel Dubois
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ArcelorMittal France SA
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Arcelor France SA
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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

Definitions

  • the present invention relates to a novel method of hot-coating a steel sheet by dipping in a bath of liquid metal, in particular containing molten zinc.
  • the invention relates to the control of the oxidation-reduction of the atmosphere of the input horn in the liquid zinc bath, with respect to iron and liquid zinc, more specifically in the vicinity of the wetting line.
  • US Pat. No. 4,557,953 (corresponding to EP-A-0 172 681) proposes a method in which an atmosphere of inert gases containing 1-8% hydrogen by volume in combination with 300 to 4500 ppm of water vapor.
  • the ratio H 2 / H 2 O must be at least 4.
  • the oxidation-reduction potential recommended in the state of the art for oxidizing the surface of the liquid zinc does not prevent the oxidation of the alloying elements contained in the steel such as the manganese, chromium, silicon, etc. These are commonly used in the production of so-called hard steels high yield strength (HLE).
  • the recommended oxidation-reduction potential also causes excessive oxidation of the surface at the level of the wetting line inside the horn. This results in the formation of large clusters of zinc oxide (ZnO) which always end up detaching, usually unpredictably. This occurs when the viscous driving forces of the surface liquid zinc become greater than those of adhesion and surface tension with respect to the horn.
  • the present invention aims to provide a solution to the problems posed in the state of the art and in particular related to the zinc oxidation process which is recommended.
  • the present invention has the particular object of reducing to a minimum the zone in which the oxidation of liquid zinc and alloying elements of the sheet, with the exception of iron, is achieved, therefore the time corresponding oxidation, before the entry of the strip into the zinc bath.
  • an injection of oxidizing gas for the liquid and non-oxidizing metal for iron is carried out in said second zone of said horn.
  • This gas contains for example a mixture of H 2 O and H 2 , and / or of H 2 O and N 2 , and / or of CO 2 , CO, H 2 O, H 2 and / or O 2 .
  • the difference in oxidizing power, expressed in equivalent P (H 2 ) / P (H 2 O), between said first zone, non-oxidizing, and said second zone, oxidizing is at least a factor 8 , that is to say [P (H 2 ) / P (H 2 O)] oxidant x 8 ⁇ [P (H 2 ) / P (H 2 O)] non-oxidizing .
  • said first zone is reducing vis-à-vis the iron.
  • Figure 1 shows schematically a sectional view of an installation type trompe galvanizing steel, according to the state of the art.
  • Figure 2 schematically shows a sectional view of an installation type steel tubing horn, according to the present invention.
  • the steel strip 1 enters the molten zinc bath 5 at a horn 2 and changes direction, in order to exit the bath again, at the level
  • the atmosphere 7 in the horn 2 above the molten zinc bath 5 is oxidizing at least with respect to zinc, but not iron.
  • Clusters of zinc oxide 4 are formed at the level of the wetting line 6 on the inner surface of the horn 2.
  • Figure 2 shows the schematic galvanizing installation adapted to the features of the present invention.
  • the present invention relates to a device for producing a bell or horn 2 in two distinct sections by means of a separation zone 8, the atmospheres 9,10 respectively corresponding to the two sections, said zone 1 and zone 2, being of nature different.
  • Zone 1 corresponds to a non-oxidizing atmosphere 9
  • zone 2 corresponds to an oxidizing atmosphere 10 vis-a-vis liquid zinc.
  • the zone 2 has an injector 12 of oxidizing gas with typically a ratio H 2 / H 2 O, or equivalent (H 2 + CO) / (CO 2 + H 2 O), from 1 to 70, with an H 2 content ⁇ 1% by volume and a flow rate of between 5 and 50 Nm 3 / h.
  • injector 12 of oxidizing gas typically a ratio H 2 / H 2 O, or equivalent (H 2 + CO) / (CO 2 + H 2 O), from 1 to 70, with an H 2 content ⁇ 1% by volume and a flow rate of between 5 and 50 Nm 3 / h.
  • zone 2 is as short as possible.
  • Zone 2 has a length typically between 10 and 2000 mm and advantageously between 100 and 300 mm, in order to optimize the distribution of oxidizing gas over the width of the zone and to simultaneously minimize the oxidation time of the sheet.
  • the oxidation time of the substrate is typically 0.1 to 0.2 seconds.
  • the present invention thus makes it possible to obtain the oxidation of liquid zinc in zone 2 and at the same time to limit the oxidation time available for the sheet before entering the zinc bath, by the presence of a zone 1 non-oxidizing.
  • the invention consists in reducing to a minimum the zone in which the intentional oxidation of zinc is carried out in order to reduce the undesired available oxidation time for the alloying elements contained in the sheet metal. steel.
  • this reducing material makes it possible to limit as much as possible the adhesion of the boundary layer of the liquid metal to the tube, at the level of the wetting zone, by locally preventing the oxidation of zinc therein.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating With Molten Metal (AREA)

Abstract

Hot coating of a steel sheet (1) is carried out by dipping the sheet in a bath of liquid metal (5) utilizing an inlet tube (5) at least partly under a controlled oxidizing atmosphere. A method for the hot coating of a steel sheet (1) by dipping in a bath of liquid metal (5) utilizing an inlet tube (5) at least partly under a controlled oxidizing atmosphere consists of: (a) passing the sheet through a first zone (9) in which the atmosphere of hydrogen and water vapor is non-oxidizing with respect to iron and such that P(H2)/P(H2O) is greater than 70 and P(H2)) is less than 264 ppm; (b) and passing the sheet through a second zone (10) in which the atmosphere of hydrogen and water vapor is oxidizing with respect to the liquid metal and some alloying elements of the steel and such that the H2 content is less than 1% by volume. An Independent claim is also included for the inlet tube under a controlled atmosphere for putting this method into service and incorporating a means for separating the two zones.

Description

Objet de l'inventionObject of the invention

La présente invention se rapporte à un nouveau procédé de revêtement à chaud d'une tôle d'acier par trempage dans un bain de métal liquide, en particulier contenant du zinc fondu.The present invention relates to a novel method of hot-coating a steel sheet by dipping in a bath of liquid metal, in particular containing molten zinc.

Plus particulièrement, l'invention se rapporte au contrôle de l'oxydoréduction de l'atmosphère de la trompe d'entrée dans le bain de zinc liquide, par rapport au fer et au zinc liquide, plus spécifiquement au voisinage de la ligne de mouillage.More particularly, the invention relates to the control of the oxidation-reduction of the atmosphere of the input horn in the liquid zinc bath, with respect to iron and liquid zinc, more specifically in the vicinity of the wetting line.

Etat de la techniqueState of the art

Il est bien connu de l'homme de l'art en galvanisation à chaud que les vapeurs de zinc s'échappant du bain de zinc fondu produisent de nombreux défauts de surface, par dépôt d'oxydes ou de poussières sur la tôle avant ou pendant son immersion, qui rendent le produit inapte aux applications d'aspect.It is well known to those skilled in the hot-dip galvanizing art that the zinc vapors escaping from the molten zinc bath produce numerous surface defects, by depositing oxides or dusts on the sheet before or during its immersion, which render the product unsuitable for appearance applications.

Ainsi, on a proposé de réguler l'état d'oxydation du gaz d'atmosphère dans la trompe de manière telle qu'il ne soit pas oxydant pour le fer mais oxydant uniquement pour le zinc liquide à la surface du bain et sous forme de vapeur. Cela peut se faire par introduction dans la trompe d'un gaz à pouvoir oxydant contrôlé, tel qu'un mélange d'azote et d'hydrogène humide par exemple, éventuellement en présence de dioxyde de carbone ou d'oxygène. Il en résulte la formation d'un très fin film d'oxyde sur le métal liquide, qui empêche l'évaporation du zinc, de manière analogue à un film d'huile à la surface de l'eau, qui empêche l'évaporation de cette dernière.Thus, it has been proposed to regulate the oxidation state of the atmosphere gas in the tube so that it is not oxidizing for iron but oxidizing only for liquid zinc on the surface of the bath and in the form of steam. This can be done by introducing into the trunk a controlled oxidizing gas, such as a mixture of nitrogen and wet hydrogen for example, optionally in the presence of carbon dioxide or oxygen. This results in the formation of a very thin film of oxide on the liquid metal, which prevents the evaporation of zinc, similar to a film of oil on the surface of the water, which prevents the evaporation of the latter.

Ainsi, le brevet US-A-4 557 953 (correspondant à EP-A-0 172 681) propose un procédé où on maintient dans la trompe une atmosphère de gaz inertes, contenant 1-8% d'hydrogène en volume en combinaison avec 300 à 4500 ppm de vapeur d'eau. Le rapport H2/H2O doit au moins être égal à 4.Thus, US Pat. No. 4,557,953 (corresponding to EP-A-0 172 681) proposes a method in which an atmosphere of inert gases containing 1-8% hydrogen by volume in combination with 300 to 4500 ppm of water vapor. The ratio H 2 / H 2 O must be at least 4.

Une façon similaire de procéder, à titre d'exemple parmi de nombreuses autres, est décrite dans le document JP-A-063 30 271.A similar way of proceeding, by way of example among many others, is described in JP-A-063 30 271.

S'il est admis que ces inventions apportent une solution au problème en question, des problèmes annexes sont à leur tour induits de par l'état d'oxydation généré par ce fait même, notamment en certains endroits du joint liquide.If it is accepted that these inventions provide a solution to the problem in question, in turn problems are induced by the oxidation state generated by this very fact, in particular in some places of the liquid seal.

Dans le document JP-A-071 80 014, on propose alternativement de supprimer les vapeurs de zinc en refroidissant la surface du bain à une température de l'ordre de 400°C, par soufflage d'azote ayant une température pouvant aller jusqu'à 200°C. Ce procédé est toutefois très pointu et difficile à réaliser industriellement, tout en nécessitant des installations complémentaires complexes.In the document JP-A-071 80 014, it is alternatively proposed to suppress the zinc vapors by cooling the surface of the bath to a temperature of about 400 ° C., by blowing nitrogen having a temperature which can reach up to at 200 ° C. This process is however very sharp and difficult to produce industrially, while requiring complex complementary facilities.

Pour ce qui concerne les atmosphères oxydantes en particulier, on observe les deux problèmes suivants. D'une part, le potentiel d'oxydoréduction préconisé dans l'état de la technique en vue d'oxyder la surface du zinc liquide ne permet pas d'éviter l'oxydation des éléments d'alliage contenus dans l'acier tels que le manganèse, le chrome, le silicium, etc. Ceux-ci sont couramment utilisés dans la réalisation d'aciers durs dits à haute limite d'élasticité (HLE). D'autre part, le potentiel d'oxydoréduction préconisé provoque également une oxydation excessive de la surface au niveau de la ligne de mouillage à l'intérieur de la trompe. Il en résulte la formation de gros amas d'oxyde de zinc (ZnO) qui finissent toujours par se détacher, généralement de façon imprévisible. Cela se produit lorsque les forces d'entraînement visqueuses du zinc liquide en surface deviennent supérieures à celles d'adhérence et de tension superficielle vis-à-vis de la trompe.With regard to the oxidizing atmospheres in particular, the following two problems are observed. On the one hand, the oxidation-reduction potential recommended in the state of the art for oxidizing the surface of the liquid zinc does not prevent the oxidation of the alloying elements contained in the steel such as the manganese, chromium, silicon, etc. These are commonly used in the production of so-called hard steels high yield strength (HLE). On the other hand, the recommended oxidation-reduction potential also causes excessive oxidation of the surface at the level of the wetting line inside the horn. This results in the formation of large clusters of zinc oxide (ZnO) which always end up detaching, usually unpredictably. This occurs when the viscous driving forces of the surface liquid zinc become greater than those of adhesion and surface tension with respect to the horn.

Ce problème d'amas de ZnO s'explique par le fait que dans la partie du liquide extrêmement voisine de la partie métallique de la trompe, appelée sabot, la vitesse de déplacement du zinc est quasi-nulle à la ligne de mouillage. Il en résulte que les oxydes formés croissent au fil du temps jusqu'à atteindre une taille critique qui induit alors leur mise en mouvement vers la bande. Finalement, ces amas sont entraînés par la bande et y génèrent des défauts rédhibitoires pour les applications d'aspect des tôles galvanisées. C'est essentiellement la face en contact avec le rouleau de fond, dite face arrière, qui est affectée par ces défauts, selon un mécanisme non entièrement élucidé à ce jour.This problem of ZnO cluster is explained by the fact that in the part of the liquid extremely close to the metal part of the horn, called the shoe, the speed of displacement of the zinc is almost zero at the wetting line. As a result, the formed oxides grow over time until they reach a critical size which then causes them to move towards the band. Finally, these clusters are driven by the web and generate unacceptable defects for the appearance applications of galvanized sheets. It is essentially the face in contact with the bottom roller, called back face, which is affected by these defects, according to a mechanism not fully elucidated to date.

Buts de l'inventionGoals of the invention

La présente invention vise à fournir une solution aux problèmes posés dans l'état de la technique et notamment liés au procédé d'oxydation du zinc qui y est préconisé.The present invention aims to provide a solution to the problems posed in the state of the art and in particular related to the zinc oxidation process which is recommended.

La présente invention a comme but particulier de réduire au strict minimum la zone dans laquelle l'oxydation du zinc liquide et des éléments d'alliage de la tôle, à l'exception du fer, est réalisée, donc le temps d'oxydation correspondant, avant l'entrée de la bande dans le bain de zinc.The present invention has the particular object of reducing to a minimum the zone in which the oxidation of liquid zinc and alloying elements of the sheet, with the exception of iron, is achieved, therefore the time corresponding oxidation, before the entry of the strip into the zinc bath.

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

La présente invention se rapporte à un nouveau procédé de revêtement à chaud d'une tôle d'acier par trempage dans un bain de métal liquide, de préférence contenant du zinc à plus de 10%, utilisant une trompe d'entrée au moins en partie sous atmosphère oxydante contrôlée, caractérisé en ce qu'il comprend les étapes successives suivantes :

  • la tôle passe dans la trompe au niveau d'une première zone dont l'atmosphère, comprenant au moins de l'hydrogène et de la vapeur d'eau, est franchement non oxydante vis-à-vis du fer, la première zone présentant une pression partielle de vapeur d'eau P(H2O) < 264 ppm et un rapport de pressions partielles P(H2)/P(H2O) > 70; cette atmosphère peut éventuellement être faiblement oxydante vis-à-vis du métal liquide et des éléments d'alliage de l'acier constituant la tôle ;
  • la tôle passe dans la trompe au niveau d'une deuxième zone dont l'atmosphère, comprenant au moins de l'hydrogène et de la vapeur d'eau, et éventuellement CO2 et CO, est beaucoup plus oxydante que l'atmosphère de la première zone, vis-à-vis du métal liquide et des éléments d'alliage de l'acier constituant ladite tôle, tout en ne l'étant pas vis-à-vis du fer, la deuxième zone présentant une teneur en H2 inférieure à 1 % en volume, le pouvoir oxydant du gaz présent dans la deuxième zone étant équivalent à la pression partielle d'oxygène qui correspond à 1 < P (H2) /P (H2O) ou P(H2+CO)/P(H2O+CO2) <70.
The present invention relates to a novel process for hot-coating steel sheet by dipping in a bath of liquid metal, preferably containing more than 10% zinc, using an inlet horn at least in part in a controlled oxidizing atmosphere, characterized in that it comprises the following successive stages:
  • the sheet passes into the trunk at a first zone whose atmosphere, comprising at least hydrogen and water vapor, is frankly non-oxidizing with respect to iron, the first zone having a partial pressure of water vapor P (H 2 O) <264 ppm and a ratio of partial pressures P (H 2 ) / P (H 2 O)>70; this atmosphere may possibly be weakly oxidizing vis-à-vis the liquid metal and alloying elements of the steel constituting the sheet;
  • the sheet passes into the trunk at a second zone whose atmosphere, including at least hydrogen and water vapor, and optionally CO 2 and CO, is much more oxidizing than the atmosphere of the first zone, vis-à-vis the liquid metal and alloying elements of the steel constituting said sheet, while not being vis-à-vis the iron, the second zone having a lower H 2 content at 1% by volume, the oxidizing power of the gas present in the second zone being equivalent to the partial pressure of oxygen corresponding to 1 <P (H 2) / P (H 2 O) or P (H 2 + CO) / P (H 2 O + CO 2 ) <70.

Selon une caractéristique de l'invention, une injection de gaz oxydant pour le métal liquide et non oxydant pour le fer est réalisée dans ladite deuxième zone de ladite trompe. Ce gaz contient par exemple un mélange de H2O et H2, et/ou de H2O et N2, et/ou de CO2, CO, H2O, H2 et/ou O2.According to one characteristic of the invention, an injection of oxidizing gas for the liquid and non-oxidizing metal for iron is carried out in said second zone of said horn. This gas contains for example a mixture of H 2 O and H 2 , and / or of H 2 O and N 2 , and / or of CO 2 , CO, H 2 O, H 2 and / or O 2 .

De manière particulièrement avantageuse, la différence de pouvoir oxydant, exprimé en équivalent P(H2)/P(H2O), entre ladite première zone, non oxydante, et ladite seconde zone, oxydante, est d'au moins un facteur 8, c'est-à-dire

        [P(H2)/P(H2O)]oxydant x 8 < [P(H2)/P(H2O)]non-oxydant.

In a particularly advantageous manner, the difference in oxidizing power, expressed in equivalent P (H 2 ) / P (H 2 O), between said first zone, non-oxidizing, and said second zone, oxidizing, is at least a factor 8 , that is to say

[P (H 2 ) / P (H 2 O)] oxidant x 8 <[P (H 2 ) / P (H 2 O)] non-oxidizing .

Tout aussi avantageusement, on a la relation suivante entre les pressions partielles de ladite première zone, non oxydante, et ladite seconde zone, oxydante :

        [P(H2+CO)/P(H2O+CO2)]oxydant x 8 < [P(H2+CO)/P(H2O+CO2)]non-oxydant

Equally advantageously, there is the following relationship between the partial pressures of said first zone, non-oxidizing, and said second oxidizing zone:

[P (H 2 + CO) / P (H 2 O + CO 2 )] oxidant x 8 <[P (H 2 + CO) / P (H 2 O + CO 2 )] non-oxidizing

De préférence, ladite première zone est réductrice vis-à-vis du fer.Preferably, said first zone is reducing vis-à-vis the iron.

Brève description des figuresBrief description of the figures

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

La figure 2 représente schématiquement une vue en coupe d'une installation de type trompe de galvanisation d'acier, selon la présente invention.Figure 2 schematically shows a sectional view of an installation type steel tubing horn, according to the present invention.

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

Une description très schématique d'une trompe classique de galvanisation d'acier est présentée à la figure 1.A very schematic description of a conventional steel galvanizing tube is shown in Figure 1.

La bande d'acier 1 pénètre dans le bain de zinc fondu 5 au niveau d'une trompe 2 et change de direction, en vue de sortir à nouveau du bain, au niveau d'un cylindre de fond 3. L'atmosphère 7 dans la trompe 2 au-dessus du bain de zinc fondu 5 est oxydante au moins vis-à-vis du zinc, mais non du fer. Des amas d'oxyde de zinc 4 se forment au niveau de la ligne de mouillage 6 sur la surface intérieure de la trompe 2.The steel strip 1 enters the molten zinc bath 5 at a horn 2 and changes direction, in order to exit the bath again, at the level The atmosphere 7 in the horn 2 above the molten zinc bath 5 is oxidizing at least with respect to zinc, but not iron. Clusters of zinc oxide 4 are formed at the level of the wetting line 6 on the inner surface of the horn 2.

La figure 2 représente l'installation de galvanisation schématisée adaptée aux caractéristiques de la présente invention.Figure 2 shows the schematic galvanizing installation adapted to the features of the present invention.

La présente invention concerne un dispositif en vue de réaliser une cloche ou trompe 2 en deux sections distinctes au moyen d'une zone de séparation 8, les atmosphères 9,10 correspondant respectivement aux deux sections, dites zone 1 et zone 2, étant de nature différente. La zone 1 correspond à une atmosphère non oxydante 9 et la zone 2 correspond à une atmosphère oxydante 10 vis-à-vis du zinc liquide.The present invention relates to a device for producing a bell or horn 2 in two distinct sections by means of a separation zone 8, the atmospheres 9,10 respectively corresponding to the two sections, said zone 1 and zone 2, being of nature different. Zone 1 corresponds to a non-oxidizing atmosphere 9 and zone 2 corresponds to an oxidizing atmosphere 10 vis-a-vis liquid zinc.

Selon une modalité de réalisation préférée de l'invention, la zone 2 présente un injecteur 12 de gaz oxydant avec typiquement un rapport H2/H2O, ou équivalent (H2+CO)/(CO2+H2O), de 1 à 70, avec une teneur en H2 < 1% en volume et un débit compris entre 5 et 50 Nm3/h.According to a preferred embodiment of the invention, the zone 2 has an injector 12 of oxidizing gas with typically a ratio H 2 / H 2 O, or equivalent (H 2 + CO) / (CO 2 + H 2 O), from 1 to 70, with an H 2 content <1% by volume and a flow rate of between 5 and 50 Nm 3 / h.

Toujours selon l'invention, la zone 2 est aussi courte que possible. La zone 2 a une longueur comprise typiquement entre 10 et 2000 mm et avantageusement entre 100 et 300 mm, afin d'optimiser la distribution de gaz oxydant sur la largeur de la zone et minimiser simultanément le temps d'oxydation de la tôle. Lorsque la ligne tourne à une vitesse de 1 m/s par exemple, le temps d'oxydation du substrat est ainsi typiquement de 0,1 à 0,2 secondes.Still according to the invention, zone 2 is as short as possible. Zone 2 has a length typically between 10 and 2000 mm and advantageously between 100 and 300 mm, in order to optimize the distribution of oxidizing gas over the width of the zone and to simultaneously minimize the oxidation time of the sheet. When the line rotates at a speed of 1 m / s for example, the oxidation time of the substrate is typically 0.1 to 0.2 seconds.

La présente invention permet donc d'obtenir l'oxydation du zinc liquide dans la zone 2 et en même temps de limiter le temps d'oxydation disponible pour la tôle avant son entrée dans le bain de zinc, par la présence d'une zone 1 non oxydante. En d'autres termes, l'invention consiste à réduire au strict minimum la zone dans laquelle l'oxydation intentionnelle du zinc est réalisée afin de réduire le temps d'oxydation disponible non désiré pour les éléments d'alliage contenus dans la tôle d'acier.The present invention thus makes it possible to obtain the oxidation of liquid zinc in zone 2 and at the same time to limit the oxidation time available for the sheet before entering the zinc bath, by the presence of a zone 1 non-oxidizing. In other words, the invention consists in reducing to a minimum the zone in which the intentional oxidation of zinc is carried out in order to reduce the undesired available oxidation time for the alloying elements contained in the sheet metal. steel.

De plus, on pourra prévenir la formation d'amas d'oxyde au niveau de la trompe à la ligne de mouillage en protégeant la partie interne de la trompe à cet endroit au moyen d'un matériau réducteur, comme le carbone par exemple. Ainsi, cette matière réductrice permet de limiter au maximum l'adhérence de la couche limite du métal liquide à la trompe, au niveau de la zone de mouillage, en y empêchant localement l'oxydation du zinc.In addition, it will be possible to prevent the formation of oxide clusters at the level of the horn at the wetting line by protecting the inner part of the horn at this point by means of a reducing material, such as carbon for example. Thus, this reducing material makes it possible to limit as much as possible the adhesion of the boundary layer of the liquid metal to the tube, at the level of the wetting zone, by locally preventing the oxidation of zinc therein.

Claims (6)

  1. Method for hot-coating a steel sheet (1) by quenching in a bath of liquid metal (5), preferably comprising over 10% zinc, using an intake pump (2) at least partially under controlled oxidising atmosphere, characterised in that it comprises the following successive stages:
    - the sheet (1) passes in the pump (2) at the level of a first zone (9) whose atmosphere, comprising at least hydrogen and water steam, is definitely non-oxidising with regard to iron, the first zone (9) having a partial pressure of water steam P(H2O) < 264 ppm and a ratio of partial pressures P(H2)/P(H2O) > 70;
    - the sheet (1) passes in the pump (2) at the level of a second zone (10) whose atmosphere, comprising at least hydrogen and water steam and possibly CO2 and CO, is oxidising with regard to the liquid metal and to the alloy elements of the steel making up said sheet, the second zone (10) having an H2 level lower than 1% by volume, the oxidising power of the gas present in the second zone (10) being equivalent to the partial pressure of oxygen which corresponds to 1 < P(H2)/P(H2O) or P(H2+CO)/P(H2O+CO2) < 70.
  2. Method according to Claim 1, characterised in that an injection (12) of gas that is oxidising with regard to the liquid metal and non-oxidising with regard to iron occurs in said second zone (10) of said pump (2).
  3. Method according to Claim 2, characterised in that said oxidising gas comprises a mixture of H2O and H2, and/or H2O and N2, and/or CO2, CO, H2O, H2, and/or O2.
  4. Method according to any one of Claims 1 to 3, characterised in that the difference in oxidising power, expressed in equivalent P(H2)/P(H2O), between said non-oxidising first zone (9) and said oxidising second zone (10) is at least a factor of 8, i.e.:

            [P(H2)/P(H2O)] oxidising x 8 < [P(H2)/P(H2O)]non-oxidising.

  5. Method according to any one of Claims 1 to 3, characterised in that the following relationship exists between the partial pressures of said non-oxidising first zone (9) and said oxidising second zone (10):

            [P(H2+CO) / P (H2O+CO2)] oxidising x8< [ P (H2+CO) /P(H2O+CO2)]non-oxidising.

  6. Method according to any one of the preceding claims, characterised in that said first zone (9) is reducing with regard to iron.
EP01273287A 2001-01-17 2001-11-16 Steel galvanizing method Expired - Lifetime EP1358360B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP01273287A EP1358360B1 (en) 2001-01-17 2001-11-16 Steel galvanizing method

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP01870009A EP1225244A1 (en) 2001-01-17 2001-01-17 Process for galvanisation of steel
EP01870009 2001-01-17
PCT/BE2001/000199 WO2002057504A1 (en) 2001-01-17 2001-11-16 Steel galvanizing method
EP01273287A EP1358360B1 (en) 2001-01-17 2001-11-16 Steel galvanizing method

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EP1358360A1 EP1358360A1 (en) 2003-11-05
EP1358360B1 true EP1358360B1 (en) 2007-03-21

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EP01870009A Withdrawn EP1225244A1 (en) 2001-01-17 2001-01-17 Process for galvanisation of steel
EP01273287A Expired - Lifetime EP1358360B1 (en) 2001-01-17 2001-11-16 Steel galvanizing method

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EP01870009A Withdrawn EP1225244A1 (en) 2001-01-17 2001-01-17 Process for galvanisation of steel

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AT (1) ATE357541T1 (en)
DE (1) DE60127456T2 (en)
ES (1) ES2283377T3 (en)
WO (1) WO2002057504A1 (en)

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4557953A (en) * 1984-07-30 1985-12-10 Armco Inc. Process for controlling snout zinc vapor in a hot dip zinc based coating on a ferrous base metal strip
DE3933244C1 (en) * 1989-10-05 1990-06-13 Hoesch Stahl Ag, 4600 Dortmund, De Continuous zinc coating appts. for coating metal strip - comprises melt alloy bath covered with hood having hydrogen, steam and inert gas atmos. and control system
JPH0649610A (en) * 1992-07-29 1994-02-22 Kawasaki Steel Corp Continuous plating method and device for molten metal
JPH06330271A (en) * 1993-05-26 1994-11-29 Nippon Steel Corp Production of galvanized steel sheet
JPH07145465A (en) * 1993-11-24 1995-06-06 Nippon Steel Corp Hot dip metal coating method and device
JP3437731B2 (en) * 1996-11-27 2003-08-18 新日本製鐵株式会社 Apparatus for preventing foreign matter generated in snout from adhering to steel sheet in hot dip plating
FR2782326B1 (en) * 1998-08-13 2000-09-15 Air Liquide METHOD FOR GALVANIZING A METAL STRIP
JP2000290761A (en) * 1999-04-06 2000-10-17 Nkk Corp Continuous hot-dipping metal coating facility and using method thereof

Also Published As

Publication number Publication date
EP1225244A1 (en) 2002-07-24
DE60127456T2 (en) 2007-12-06
EP1358360A1 (en) 2003-11-05
WO2002057504A1 (en) 2002-07-25
DE60127456D1 (en) 2007-05-03
ES2283377T3 (en) 2007-11-01
ATE357541T1 (en) 2007-04-15

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