EP0064922A1 - Apparatus for galvanizing metallic strips - Google Patents

Abstract

Installation which comprises: a first fixed deflection roller 18, positioned above the surface of the bath of molten zinc and over which the strip to be galvanized passes 8, on leaving the galvanizing tube a second deflection roller 20 mounted on a movable arm 22 and guiding the strip after galvanizing, towards the wringing means; a coating roller 26 mounted on a movable arm 28 so as to be able to take two positions: a working position in which it plunges into the galvanizing bath to ensure the coating of only one side of the strip and a rest position in which it is removed from the path of the strip and; a roller 30, or bottom roller, supported by a movable arm 32 so as to be able to occupy two positions, a working position in which it is located at the bottom of the tank 12 containing the galvanizing bath, in order to ensure the immersion of the strip in contact with this roller to galvanize the two faces of the strip and, a rest position in which it is spaced from the path of the strip.

Description

The present invention relates to improvements made to installations for galvanizing metal strips.

It is known that in an annealing and galvanizing line, a strip, after having undergone an appropriate annealing cycle, is brought into contact with molten zinc with a view to depositing this metal on one or two faces. In general, a galvanizing installation comprises: a tank containing a bath of molten zinc, one or more deflection rollers ensuring the guiding of the strip to be galvanized along a path which brings it into contact with the metal of the bath and means ensuring the 'wringing and drying of the strip, to bring the thickness of the metal deposited to the desired value.

When the installation is intended to provide galvanization on both sides of the strip, the deflection roller (s) are immersed in the tank and preferably they are positioned at the bottom of this tank so that the strip plunges into the bath. molten zinc.

For certain applications, in particular in automobile construction, it is desirable to produce galvanized sheets on a single face so as to obtain both anticorrosive properties inside the parts, and surfaces which can be welded on the external face. In these applications to one side galvanizing, the deflection rollers are located above the level of the zinc bath and this is brought into contact with the face of the sheet to be coated by various means such as, for example, elevation by effect of the meniscus, by boiling or alternatively by using a coating roller plunging partially into the galvanizing bath and which coats the desired face of the strip which is in contact with it with liquid zinc. For this purpose, reference may be made to French patent n ° 7619870 of June 30, 1976.

Given the industrial needs of galvanized sheets, it is desirable to be able to carry out on the same installation, galvanization on one side or on two sides. To this end, various combinations of mechanical means can be envisaged, however these solutions generally require a shutdown of the installation and a change of equipment, which results in a significant loss in production capacity.

The present invention proposes to provide an installation making it possible to go from galvanizing a metal strip on one side to galvanizing on two sides, and vice versa, without requiring the installation to be stopped and without cutting the strip. . In addition, the installation according to the invention makes it possible to carry out annealing without galvanizing when, for example, the oven connected to the device is used for the sole purpose of annealing.

The installation according to the invention implements the galvanizing process on a known face, according to which a coating roller is used which brings the molten zinc onto the determined face of the strip, stretched horizontally between two deflection rollers.

• a) un premier rouleau de renvoi fixe, positionné au-dessus du niveau du bain de zinc fondu et sur lequel passe la bande à galvaniser, à sa sortie de la trompe de galvanisation,
• b) un second rouleau de renvoi, monté sur un bras mobile et assurant le guidage de la bande après galvanisation, vers les moyens d'essorage,
• c) un rouleau enducteur, monté sur un bras mobile de façon à pouvoir prendre deux positions : une première position dans laquelle il plonge dans le bain de zinc pour assurer l'enduction d'une face déterminée de la bande et une seconde position dans laquelle il est écarté de la trajectoire de la bande et
• d) un rouleau de fond supporté par un bras mobile de façon à pouvoir occuper deux positions : une position de travail dans laquelle il est situé au fond de la cuve afin d'assurer l'immersion de la bande au contact de ce rouleau pour réaliser la galvanisation des deux faces et une position de repos dans laquelle il est écarté de la trajectoire de la bande.

This installation according to the invention is essentially characterized in that it comprises, in a plon- bell giant in the galvanizing bath and connected to a galvanizing tube communicating with an annealing furnace:

• a) a first fixed deflection roller, positioned above the level of the bath of molten zinc and over which the strip to be galvanized passes, on leaving the galvanizing tube,
• b) a second deflection roller, mounted on a movable arm and guiding the strip after galvanization, towards the wringing means,
• c) a coating roller, mounted on a movable arm so as to be able to take two positions: a first position in which it plunges into the zinc bath to ensure the coating of a determined face of the strip and a second position in which it is moved away from the path of the strip and
• d) a bottom roller supported by a movable arm so as to be able to occupy two positions: a working position in which it is located at the bottom of the tank in order to ensure the immersion of the strip in contact with this roller to produce galvanizing the two faces and a rest position in which it is moved away from the path of the strip.

According to a characteristic of this invention, the bottom roller is mounted at the end of a sliding arm in a fixed part of the installation and the arm supporting the coating roller is articulated on an axis provided on said fixed part.

According to another characteristic of this invention, the installation further comprises a correcting roller, placed below the surface of the bath of molten zinc, in order to improve the flatness of the strip during spinning, in the case two-sided galvanizing, this correcting roller being mounted on a movable arm.

According to yet another characteristic of this invention, the installation comprises two movable blowing nozzles to ensure the dewatering of the excess zinc deposited during the coating on one or two faces.

• - la figure 1 est une vue en élévation latérale, avec arrachement partiel d'une installation selon l'invention, les rouleaux mobiles étant positionnés en vue de réaliser une galvanisation deux faces ;
• - la figure 2 est une vue similaire à la figure 1 montrant la position des rouleaux mobiles dans le cas d'une galvanisation une face, et
• - la figure 3 est une représentation très schématique montrant la position des différents rouleaux lors d'un fonctionnement en recuit sans galvanisation.

Other characteristics and advantages of this invention will emerge from the description given below with reference to the appended drawings which illustrate an embodiment thereof devoid of any limiting character. On the drawing :

• - Figure 1 is a side elevational view, partially broken away of an installation according to the invention, the movable rollers being positioned in order to achieve a two-sided galvanization;
• FIG. 2 is a view similar to FIG. 1 showing the position of the mobile rollers in the case of one-sided galvanization, and
• - Figure 3 is a very schematic representation showing the position of the different rollers during an annealing operation without galvanizing.

Reference is made to the figures and more particularly to Figures 1 and 2.

It can be seen that the installation according to the invention comprises, as known, a bath of molten zinc 10 contained in a galvanizing tank 12, heated by any appropriate means, a bell 14 plunging into the galvanizing bath 10 and a galvanizing tube 16 connected to the bell 14 and communicating with an annealing furnace not shown.

According to the invention the metal strip B, to be galvanized on one or two sides, first passes over a fixed deflection roller 18, mounted in the bell 14, above the molten zinc bath 10 and at the outlet of the horn 16 in the bell. The installation comprises a second deflection roller 20, which pivots at the end of an articulated arm 22 canted at 24 on the walls of the bell so as to be able to occupy two positions: a rest position (Figure 1) in which it is kept away from the path of the strip B and a working position, in which the strip B comes to rest on this roller (FIGS. 2 and 3) in order to be stretched horizontally between the return rollers 18 and 22.

The coating roller 26 spins at the end of an articulated arm 28. It can therefore occupy two positions: a rest position, in which it is released from the path of the strip B (FIGS. 1 and 3), and a working position (Figure 2), in which it ensures, as will be seen below, the coating of the face of the strip which is supported on it.

The installation also includes a fourth roller, called the bottom roller 30 which spins at the end of a movable arm 32. In the embodiment shown in the drawing, the arm 32 slides inside an element fixed 34 secured to the bell 14 and the arm 28 receiving the coating roller 26 is articulated at 36 on the fixed element 34.

The bottom roller 30 can therefore occupy two positions: a working position (Figure 1) in which it plunges into the galvanizing bath 10 while supporting the strip and a rest position (Figures 2 and 3) in which it is moved away from the trajectory of this strip.

The installation further comprises a correcting roller 38 mounted at the end of a movable arm 40. The roller is placed below the surface of the galvanizing bath 10 in order to improve the flatness of the strip in the spin in the case of galvanization on two sides. Finally, the assembly is provided as known draining means to bring _'the thickness of the deposited metal to the desired value. These means here consist of blowing nozzles 42, 42 'mounted at the end of articulated arms 44, 44' for changing the orientation of the gas jet distributed by each nozzle. Each of the nozzles and its articulated arm are mounted on a tube 46, 46 ', respectively, which can be moved vertically by means of a rack system 48, 48' respectively.

The movement control systems of the various movable rollers are located outside and they are produced in a conventional manner. For this reason they will not be described here.

• 1 - Galvanisation deux faces (figure 1) Le rouleau d'enduction 26 et le rouleau mobile de renvoi 20 sont tous deux en position de repos et le rouleau du fond 30 est en position de travail, c'est-à-dire au fond de la cuve de galvanisation 12. La bande B passe donc sur le premier rouleau fixe de renvoi 18, plonge dans le bain de zinc fondu 10, s'enroule sur le rouleau de fond 30-et ressort du bain en s'appuyant sur le rouleau correcteur 38 afin de passer entre les deux buses de soufflage 42, 42' positionnées en regard l'une de l'autre, les buses éliminant l'excès de zinc entraîné par la bande sortant du bain 10.
• 2 - Galvanisation une face (figure 2) Le rouleau de fond 30 est en position de repos, au-dessus de la surface du bain 10, à l'écart de la trajectoire de la bande. Les rouleaux d'enduction 26 et de renvoi 20 sont en position de travail et le rouleau correcteur 38 est retiré. La bande B s'enroule donc sur le premier rouleau de renvoi 18, passe sur le rouleau d'enduction 26 qui plonge partiellement dans le bain 10 et s'enroule sur le second rouleau de renvoi 20 en étant tendue horizontalement entre les deux rouleaux de renvoi 2D et 18. le deuxième rouleau enducteur 26 dépose comme connu, une couche de zinc liquide sur la face inférieure de la bande. Après s'être enroulée sur le rouleau 20, la bande passe devant la buse de soufflage 42 qui élimine l'excès de zinc déposé sur la face inférieure de la bande au cours de l'enduction par le rouleau 26. La seconde buse 42' ne fonctionne pas.
• 3 - Recuit sans galvanisation (figure 3) Pour ce mode de fonctionnement schématisé à la figure 3 par la position des différents rouleaux, les rouleaux de renvoi 18 et 20 sont en position de travail et les rouleaux d'enduction 26 et de fond 30 sont en position de repos, à l'écart de la trajectoire de la bande. Il n'y a pas de contact entre le zinc fondu du bain 10 et la bande B, et l'essorage ne fonctionne pas.

The different operating modes of the installation thus described are as follows:

• 1 - Two-sided galvanization (Figure 1) The coating roller 26 and the movable deflection roller 20 are both in the rest position and the bottom roller 30 is in the working position, that is to say at the bottom of the galvanizing tank 12. The strip B therefore passes over the first fixed return roller 18, plunges into the bath of molten zinc 10, is wound up on the bottom roller 30 and comes out of the bath by pressing on the correction roller 38 in order to pass between the two blowing nozzles 42, 42 ′ positioned opposite one another, the nozzles removing the excess zinc entrained by the strip leaving the bath 10.
• 2 - Galvanization on one side (Figure 2) The bottom roller 30 is in the rest position, above the surface of the bath 10, away from the path of the strip. The coating rollers 26 and return 20 are in the working position and the correcting roller 38 is removed. The strip B is therefore wound on the first return roller 18, passes over the coating roller 26 which partially plunges into the bath 10 and is wound on the second return roller 20 while being stretched horizontally between the two rollers. reference 2D and 18. the second coating roller 26 deposits as known, a layer of liquid zinc on the underside of the strip. After being wound on the roller 20, the strip passes in front of the blowing nozzle 42 which removes the excess zinc deposited on the underside of the strip during the coating by the roller 26. The second nozzle 42 ' does not work.
• 3 - Annealing without galvanizing (Figure 3) For this operating mode shown diagrammatically in Figure 3 by the position of the different rollers, the return rollers 18 and 20 are in the working position and the coating rollers 26 and bottom 30 are in the rest position, away from the path of the strip. There is no contact between the molten zinc in bath 10 and strip B, and the spin does not work.

In all operating modes the atmosphere under the bell 14 is composed of a nitrogen / hydrogen mixture preferably comprising from 2 to 5% of hydrogen. The pressure in the bell is kept positive with respect to the ambient conditions by a leakage through a slot 50 at the passage of the strip, possibly supplemented by a sealing device located at the place where the strip exits in the air ambient.

It appears from the above description that the invention provides an installation which, by simply positioning the different rollers on which the strip rests and without stopping the installation or cutting the strip, makes it possible to obtain three modes separate operation which is not possible with existing facilities at present.

It remains to be understood that this invention is not limited to the embodiment described and shown, but that it encompasses all variants thereof.

Claims (4)

1. Installation for galvanizing metal strips of the type comprising a tank containing a bath of molten zinc, one or more deflection rollers guiding the strip to be galvanized along a path which brings it into contact with the metal of the bath and means ensuring wringing and drying of the strip, characterized in that said installation comprises, in a bell (14) plunging into the galvanizing bath (10) and connected to a galvanizing tube (6) communicating with a annealed: - a first fixed deflection roller (18), positioned above the surface of the bath of molten zinc and over which the galvanizing strip passes (B), at its exit from the tube this galvanization, a second deflection roller (20) mounted on a movable arm (22) and guiding the strip after galvanization, towards the wringing means, - a coating roller (26), mounted on a movable arm (28) so as to be able to take two positions: a working position in which it plunges into the galvanizing bath to ensure the coating of only one side of the bange and a rest position in which it is moved away from the trajectory of the strip and, - a roller (30), or bottom roller, supported by a movable arm (32) so as to be able to occupy two positions, a working position in which it is located at the bottom of the tank (12) containing the bath this galvanization , in order to ensure the immersion of the strip in contact with this roller in order to galvanize these two strip faces and, a rest position in which it is moved away from the trajectory of the strip. 2. Installation according to claim 1, characterized in that the bottom roller (30) is mounted at the end of a arm (32) sliding in a fixed part (34) of the installation and the arm (28) supporting the coating roller (26) is articulated on an axis (36) fixed on this fixed part. 3. Installation according to one of claims 1 or 2, characterized in that it comprises a correcting roller (38) placed below the surface of the bath of molten zinc, in order to ensure the flatness of the strip during wringing, in the case of two-sided galvanization, this correcting roller being mounted on a movable arm (40). 4. Installation according to any one of the preceding claims, characterized in that it comprises two mobile blowing nozzles (42-42 ') to ensure the dewatering of the excess zinc deposited during the coating of a or two sides.

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