FR2919876A1 - COMBINED LINE OF ANNEALING AND GALVANIZING AND PROCESS FOR TRANSFORMING A CONTINUOUS ANNEALING LINE INTO SUCH A COMBINED LINE - Google Patents

Abstract

The invention relates to a combined annealing and galvanizing line of a metal strip (1) successively comprising an annealing installation (2) with an annealing section (22), a section (23) for rapid cooling, a section (26) and a second slow-cooling section (25), and a galvanizing plant (4) ending in a quench bath.In accordance with the invention, the galvanizing plant (4) is incorporated in the interior of the annealing plant (2), between the overaging section (26) and the second cooling section (25) and at the outlet of the overaging section (26), the band is guided by means selective guide (80), either to the galvanizing plant (4) and then directly to the outlet device (3) of the line, or directly to the second cooling section (25) and the device (3) output.The invention also covers a process, part It is a simple and economical process for converting an existing continuous annealing line and a combined annealing and / or galvanizing line.

Description

The subject of the invention is a combined annealing and galvanizing line

  of a metal strip and also covers a method of transforming an existing annealing line into such a combined line.

  The cold rolling of a steel strip causes hardening, by hardening, of the metal which causes a fragility making it more difficult and may even prohibit the subsequent use of the rolled strips. In order to restore the ductility of a rolled strip, a so-called recrystallization annealing heat treatment is usually employed. Such treatment can be performed statically in patch-annealing ovens on the coil-wound web. However, for some time, to prevent unwinding and winding of the coils and their transport from one facility to the next, it has been proposed to perform the treatment of these strips in continuous scrolling on specialized lines. FIG. 1 schematically shows, by way of example, the usual arrangement of such a continuous annealing line which comprises successively, in the running direction of the strip: an input device 1 comprising one or two rollers of 11, a shear 12, for example a guillotine, a splicing welder 13 for connecting the tail of a strip from a first unwinder to the head of the next strip from the second unwinder to ensure operation continuous line, and a strip accumulator 14 for, when the unwinding is stopped upstream, to perform the splicing weld, to deliver at its output, a certain length of tape previously accumulated to continue the scrolling continuously of that in equipment downstream. An annealing installation 2 comprising a preheating section 21, a section 22 for heating and holding at the annealing temperature for the necessary time, a rapid cooling section 23, a supercooling section 24 and a second cooling section; slow. - An output device 3 comprising a tape accumulator 31, possibly a skin-pass rolling mill 32, a shear 33 and one or two winders 34 working alternately. The entire annealing installation forms a furnace generally placed under a controlled atmosphere in a closed enclosure, and wherein the strip travels along a zig-zag path defined by a plurality of deflection rollers and which successively provides the heating of the band in section 21, keeping it at the annealing temperature in section 22, a first cooling in section 23, fast enough to avoid oxidation, a supplement of overaging treatment, in English overaging in section 24 which usually comprises several successive units and slow cooling in the section which usually terminates by quenching the strip in a final coolant bath to room temperature. Furthermore, in order to improve the corrosion resistance of the metal sheets used in particular, in certain applications such as the building, the automobile or household appliances, it is common practice to deposit on the surface of these sheets a layer of cladding. zinc or a zinc-based alloy. For this, usually, the tape is passed over a roll immersed in a bath of liquid metal. It is therefore necessary that the band, before entering the bath, be brought to the desired temperature. Inasmuch as, usually, the strip has undergone an annealing treatment, it is possible to produce continuous annealing and galvanizing lines of the type shown schematically in FIG. 2, comprising successively, in the direction of the scrolling of the product: a device input 1 of the type described above, comprising a unrolling machine 1 1, a shear 12, a splicing welder 13 and an accumulator 14, - an annealing plant 2, - a galvanizing plant 4 comprising a bath of liquid metal 41, a dewatering device 42, an output circuit with, for example, an alloying oven 43 and a cooling equipment 44 and a tundish 45, a device 3 for outputting the line comprising, for example, a skin-rolling mill; pass 32, a passivation section 35, an output accumulator 31, a shear 33 and one or two winders 34 working alternately. In such a continuous galvanizing line, the annealing installation 2 successively performs the metallurgical annealing and correct temperature-setting functions of the strip before it enters the metal bath 41. It therefore comprises a preheating section 21, a retention section 22 at the annealing temperature, a rapid cooling section 23 and a section 26 of galvanizing temperature in which can also be carried out an activation of the surface to be galvanized by surface chemical migrations. In general, such lines of continuous processing constitute a heavy equipment with a very high cost and which requires, in order to be profitable, a large production. A modification of the adjustment parameters depending on the grade of the metal to be treated and the qualities to be obtained in fact leads to a stopping of the line with a loss of productivity and the production of waste. The complete annealing lines of the type shown in FIG. 1 are therefore provided, normally, for steel grades which justify a large tonnage and are provided with all the equipment necessary to adapt to a new grade after modification of the adjustment parameters. , including temperatures and times of heat treatments.

  However, market developments, especially for the automotive industry, are leading to a greater variety of steel grades and their metallurgy as well as a higher demand for galvanized strips. In addition, the tonnages required in each grade are relatively low and require rapid changes of the adjustment parameters, sometimes without stopping the scroll, the tail of a coil at the end of unwinding can be welded to the head of a next coil , of different quality and requiring other treatments.

  As a result, a number of continuous line annealing facilities, planned for large tonnages, no longer become profitable due to market developments and decreasing tonnages demanded. On the other hand, the demand for galvanized sheet is increasing and it is therefore interesting to produce continuous lines that allow the demand to be met flexibly. It is therefore necessary to achieve new combined lines to continuously perform either an annealing treatment alone, or annealing followed by galvanization. EP-A-0254633, for example, describes such a combined line comprising successively, between a reel and a winder, a horizontal type annealing furnace, a temperature control section and a conventional type of galvanizing installation. There is also a coating coating installation. According to the invention, to allow a passage from one treatment to another, without increasing the complexity and the cost of such an installation, the treated metal flow must be at most 7 tons / hour, at a speed of passage at most equal to 12 meters per minute. The production capacity of such an installation, designed some twenty years ago, would have been very limited. It has also been proposed in WO-002/22894 to place a galvanizing plant downstream of an annealing plant between the controlled atmosphere cooling section and a final cooling tank to ambient temperature. The galvanizing installation is therefore added to the annealing installation and increases the bulk of the assembly. The object of the invention is to solve such problems by means of a particular arrangement of the different equipment necessary, on the one hand for annealing and on the other hand for galvanization, making it possible to produce a combined line capable of performing either an annealing alone, ie an annealing followed by galvanization, without unduly increasing the congestion in length of the line. In addition, this particular arrangement of the equipment makes it possible, according to the invention, to quite simply convert an existing continuous annealing installation to add galvanizing means without excessive modification of the existing installation and remaining in the floor area of the floor. it. Thus, the invention makes it possible to continue a profitable exploitation of certain existing continuous annealing installations that are no longer adapted to the requirements of the market, by transforming them into a combined line capable of handling a very wide variety of products. The invention therefore relates to a combined annealing and galvanizing line of a metal strip comprising means for controlling the movement of the strip in a continuous line, between an input device and an output device of the line, successively in a annealing apparatus and a galvanizing plant, the annealing apparatus having a section for heating and holding the band at an annealing temperature, a first annealing section after annealing, an overaging section and a second cooling section up to ambient temperature, and the galvanizing plant having an inlet section of the strip in a galvanizing metal bath, an outlet section of the metal bath of the strip covered on both sides with a layer coating, a cooling section of the coating and a final coolant bath. According to the invention, the galvanizing plant is incorporated inside the annealing plant, between the overaging section and the second cooling section, and at the outlet of the overaging section, the band is directed by selective guiding means, either to the galvanizing plant and then, at the outlet of the final cooling bath, directly to the output device of the line, or directly to the second cooling section and the output device of line. In a preferred embodiment, the overfill section and the second cooling section of the annealing plant are each placed in a sealed enclosure filled with a protective gas and the inlet section in the galvanizing metal bath is placed in a sealed duct having an inlet connected to the outlet of the overflow section and two outlets, respectively a first outlet immersed in the metal bath and a second outlet on which is releasably connected a leaktight trough with the second section cooling and annealing installation, said second outlet being provided with removable sealing means. According to another preferred feature, the combined line according to the invention comprises a plurality of deflection rollers defining two paths of the strip at the exit of the overaging section, respectively a first galvanization path comprising an inlet section in the metal bath. passing through the first outlet of the sealed conduit, an outlet section of the metal bath, a cooling section of the coating prior to entry into the final cooling bath, and an exit section of said cooling bath passing above or below the enclosure in which is placed the second cooling section, so as to connect directly to the output device of the line, and a second annealing path alone, passing through the removable connection channel between the second outlet of the sealed conduit and the enclosure of the second cooling section. Particularly advantageously, the combined line comprises two liquid final cooling baths of the strip, respectively a first bath placed at the outlet of the galvanizing installation, and a second bath placed at the outlet of the second cooling section, the strip being directed towards the outlet device of the line after final cooling carried out, either in the first bath after galvanization, or in the second bath after an annealing treatment alone, without galvanizing. Preferably, the first cooling bath is placed above the metal bath and offset to the inlet side thereof to reduce the bulk of the galvanizing plant. To allow the incorporation of the galvanizing plant into the annealing installation without increasing the length of the line, the over-age section has a reduced length compared to the length usually required in a continuous annealing line. and the running speed of the web is adapted to this reduced length in order to obtain the necessary processing time. The invention also covers a process for converting into a combined annealing and galvanizing line, an existing continuous annealing line of a metal strip comprising successively, in a running direction of the product, an input device in the line, a preheating section, an annealing section, a first rapid cooling section after annealing, a supercooling section, a slow cooling section under a protective atmosphere and a line output device. According to the invention, part of the overaging section is removed leaving the other sections in place and a galvanizing installation is placed inside the annealing line, in the space thus released between the remaining part of the overfill section and the second slow cooling section, and connected to the scroll control means so as to achieve a combined annealing and galvanizing line without increasing the overall length of the annealing line. According to another characteristic of the invention, the running speed of the web between the input device and the output device of the line is adapted either to the annealing process alone or to the galvanizing process.

  According to another advantageous characteristic, the galvanizing installation replaces only a part of the over-aging section and the running speed of the band is adjusted, if necessary, so as to carry out a survival treatment in the remaining part of the corresponding section. According to another preferred characteristic, the temperature in the annealing section is maintained at the desired level for annealing, taking into account the nature of the strip and the speed of travel and, between the exit of the overaging section and the inlet in the galvanizing bath, the installation comprises combined means of heating and cooling, for adjusting the temperature of the strip to a level suitable for the galvanizing process. In a preferred embodiment, the galvanizing installation comprises means for controlling the running of the strip between a galvanizing metal bath and a quenching bath, along a continuous scrolling path passing over a plurality of deflection rollers. and having at least four portions, respectively a first connection portion between the quench section and the inlet to the metal bath, a second exit portion of the metal bath with coating thickness control, a third cooling portion coating before entering the quench bath and a fourth quenching bath outlet portion, connecting directly to the exit section of the annealing line, without passing through the slow cooling section. Furthermore, to adapt the overall size of the galvanizing installation to the length of the space released in the annealing line, the quenching bath is placed above the metal bath and shifted towards the inlet side of the the line, so that in the third cooling part, the strip returns to the rear and, in the fourth quenching bath outlet portion, passes over the metal bath and then above or below the slow cooling section to connect directly to the output device of the line.

  Other advantageous features of the invention will appear in the following description of certain particular embodiments, given by way of simple examples with reference to the accompanying drawings.

  Figure 1 shows schematically the conventional arrangement of a continuous annealing line, followed by a finishing section. Figure 2 shows schematically the known arrangement of a continuous line of galvanization after annealing. Fig. 3 is a diagram showing two examples of continuous annealing thermal cycles. Figure 4 shows a typical annealing cycle in a continuous galvanizing line. FIG. 5 schematically shows the arrangement, according to the invention, of a combined annealing and galvanizing line. Figure 6 shows schematically, on an enlarged scale, the arrangement according to the invention of a galvanizing installation. FIG. 7 and FIG. 8 are two diagrams indicating, by way of example, two complete cycles of annealing in a combined line according to the invention. Figure 9 shows schematically the arrangement according to the invention of a galvanizing plant inside a continuous annealing line. Figure 10 shows in a synthetic manner, the functions of continuous annealing and galvanizing and those common to both treatments. As indicated above, FIG. 1 represents, schematically, the conventional arrangement of a continuous annealing line comprising, between an input device 1 and an output device 3, an oven 2 in which the strip circulates following a 30 zig-zag path, between two series of baffle rollers, respectively upper and lower, and consisting of successive sections respectively providing heating of the band M in section 21, its maintenance at the annealing temperature in section 22, a cooling in section 23, a so-called over-aging or over-aging treatment supplement in section 24 comprising several successive units and slow cooling to a moderate temperature, in section 25. FIG. 3 is a diagram showing two examples continuous annealing cycles shown respectively by curve 5 for a direct flame furnace and by the 5 'curve for flameless heating direct me, for example by reverberation. Heating has no particular metallurgical impact up to 600 C and the rate of rise in temperature (51, 51 ') can be more or less rapid depending on the heating technology used. Beyond 600 C and up to the maximum temperature, the heating is continued at a lower speed (52, 52 ') in order to improve the control of the temperature. The annealing temperature (53, 53 ') depends on the metallurgical quality targeted. It is generally between 650 and 700 C for tinplate and 700 to 850 C for a thin strip for galvanizing. The holding time (53, 53 ') generally close to 15 to 30 seconds, makes it possible to stabilize the annealed structure.

  This holding phase (53, 53 ') is followed by a controlled cooling (54, 54') at a slow speed, generally less than 10 C / s to a temperature of 600 to 700 C approximately, in order to ensure the precipitation of Fe3C carbides. Then, in the section 23 of the furnace, cooling is carried out to a temperature of about 350 ° C. to 450 ° C., which is rapidly conducted (55, 55 '), the cooling rate being greater than 100 C / s and able to reach 200 C / s to keep the carbon in solution. The treatment is then continued, in section 24, by maintaining the temperature for a period of one to several minutes (56, 56 '), in order to produce the precipitation of the interstitial carbon in a so-called overaging or over aging phase. The cycle is terminated by cooling (57, 57) to a moderate temperature, for example about 60 ° C., possibly to room temperature. FIG. 4 is a diagram showing a typical annealing cycle in a galvanizing line of the type shown in FIG. 2. Curve 5a, which shows the evolution of the temperature as a function of time, is analogous to the curves 5, 5 'previously described. and therefore includes the same temperature raising portions (51a, 52a), maintaining (53a) at the annealing temperature, (54a) controlled cooling at low speed, and then (55a) rapid cooling.

  As indicated above, the galvanizing line of the type shown in FIG. 2 also comprises a thermal regulation section 26 making it possible, first of all, to over-stress (56a) and then, by cooling (57a) or, optionally, heating, to bring the strip to the temperature (58a) desirable for entry into the galvanizing metal bath. The thermal cycle 5a in the galvanizing line is therefore similar to the cycle 5 in an annealing line of the type shown in FIG. 1, the differences coming essentially from the speed of movement imposed by the galvanizing process which must not exceed, normally , 200 m / min in order to be able to control the thickness of the coating deposited at the outlet of the metal bath while the usual speeds of the continuous annealing lines for thin sheets are of the order of 300 to 500 m / min.

  Such speeds are necessary to obtain the desired productivity in a conventional continuous annealing line which must be capable of treating steels of different types for which the heat treatment, in particular of over-aging, can be more or less complex and requires the use several successive processing units. The invention is based on the idea that, even for conventional and relatively complex annealing treatments, it should be possible to reduce the length of the overaging section, as compared to the usual length, and that the removal of certain chambers of over-aging would provide a space in which a galvanizing plant could be incorporated, without increasing the overall size of the annealing line, to achieve a combined line to perform either an annealing treatment alone or a treatment galvanization preceded by annealing. For example, if one-third of the passes in the overfill section of a continuous thin-film annealing furnace whose equipment is dimensioned are removed, for a given product format, to allow a speed of the order of 300 m / min, it is enough to reduce the running speed to 200 m / min to achieve the same treatment on a reduced section of a third, while maintaining the same temperature maintenance time. However, this speed of 200 m / min is close to the scroll speed usually imposed for the galvanizing process and is therefore suitable for a combined line. An installation of the type shown diagrammatically in FIG. 5 is thus carried out comprising, as in the case of FIG. 2, an input device 1, an annealing furnace 2, a galvanizing installation 4 and an outlet device 3, but in which the galvanizing temperature-setting section 26 corresponds to only a part 24 'of the over-annealing section 24 of the annealing furnace 2 shown in FIG. 1. The galvanizing installation 4' is therefore incorporated inside. of the annealing line since it is placed between the reduced overaging section 26 and the slow cooling section under a controlled atmosphere. In addition, the output of the overaging section opens into a selective guiding device 80 for directing the band M, either directly to the slow cooling section 25, for an annealing treatment alone, or to the input Ti of the In this case, at the outlet of the final cooling bath 45, the strip is directed directly towards the outlet device 3 of the line, by short-circuiting the cooling section 25.

  However, if it is desired not to increase the overall length of the annealing line, the space evolved by the removal of a portion of the overaging section must have a relatively small length, less than the normal extent of an annealing line. classical galvanizing installation.

  It is therefore interesting to realize a particularly compact galvanizing installation. For this, one of the ideas of the invention consists in modifying the usual architecture of the continuous galvanizing lines by organizing in a new way the unwinding of the strip at the outlet of the zinc bath, as shown diagrammatically in the figure 5 and in more detail in Fig. 6. At the exit from the over-age section 26, the strip was brought to the desired temperature for galvanizing, as shown in the diagram of Fig. 4. The strip emerging from the section 26 passes over a deflector roll Dl which directs it to the galvanizing metal bath 41 formed in a tank and in which is immersed a deflector roll D2. The band M therefore follows a downward path Ti between the output roller D1 and the immersed roll D2 on which it bears on its upper face A. The band M then leaves the bath 41 along an upward path T2 to a top roll D3, passing in front of a wiper device 42 of known type for controlling the thickness of the coating.

  All these arrangements are conventional and correspond to those shown diagrammatically in FIG. 2. In the invention, however, the band M bears on the upper roll D3 by the same side A passing over the immersed roll D2 and, therefore, instead of being directed towards the outside of the tank containing the metal bath 41, the band M returns back towards the entrance side in the tank, that is to say the left side in FIGS. In the case of FIG. 5, the strip returns to an upper roll D'3 and descends, by a descending path T3, to a deflector roll D4 immersed in the quenching bath 45. The band then comes out of this bath 45 along a rising path T4 to a pair of upper deflector rollers D5, 5 spaced apart from each other, so as to pass over the whole of the galvanizing installation 41 and the slow cooling section 25, then descends, by a downward path T5, until to a lower roll D6 to be directed to the accumulator 31 of the output device 3. As a result of this arrangement of the path of the strip, the quench bath 45 can be placed above the tank containing the metal bath Thus, the footprint of the galvanizing installation 4 is reduced compared to the conventional arrangement of FIG. 2 since it covers substantially the same length as the galvanizing bath 41. Admittedly, this provision requires the construction, above the metal bath 41, a floor to support the tank tempering 45 but this increase in height of the installation is not a real drawback, especially for the transformation of an existing installation. On the other hand, the return towards the rear of the strip from the upper roller D3 makes it possible to incorporate the entire galvanizing installation into the existing reduced space between the remaining part of the overaging section. and the slow cooling section 25. In known manner, it is possible to perform a so-called alloy heat treatment which ensures the diffusion of iron from the band to the zinc coating to create a real iron / zinc alloy. For this purpose, it is possible to place an alloy oven 43 above the wiper device 42. This alloying oven can be followed by cooling cells 44a, 44b which can be placed not only on the upward path T2, upstream of the upper roller D3, but also on the downward path T3, before entering the quench bath 45. To achieve sufficient cooling of the strip before quenching, without unduly increasing the height of the installation, it is also possible to carry out the arrangement shown diagrammatically in FIG. 6 in which, after passing over the upper roll D3, the strip descends to a lower roll D6, then goes back to an upper roller D'6 so to go down in the quenching tank 45 by passing on the immersed roll D4. Such an arrangement is also particularly compact since, at each change of direction, the band passes on a single roll returning, as before, to the rear.

  This arrangement also makes it possible to distribute cooling means 44, 44 'not only along the upward path T2 but also along the downward path T3 so as to provide sufficient cooling of the coating. It should be noted that, thanks to this arrangement, the face A 'of the strip opposite the face A passing on the immersed roll D2, comes into contact with the lower roll D6 after the upward path T2 and the descending path T3 and, thus, not likely to be deteriorated before curing the coating. Such an arrangement is particularly advantageous in applications where an outer face of the sheet, said exposed face, must have excellent surface quality, for example for the automobile body. As shown in FIG. 6, the cooling cells and, where applicable, the alloying oven 43, can advantageously be staggered on the ascending strand T2 and the descending arm T3 which, in the case of FIG. are separated by only one deflector roll D3, which further reduces the footprint of the assembly. In addition, such an arrangement makes it possible to distribute the cooling cells 44a, 44b over a greater length of strip and thus to have a less violent blowing, which reduces the risks of vibration of the strip which may have an impact on the quality. coating, in particular the regulation of its thickness.

  As indicated above, even if its length is reduced compared with the usual arrangement of the annealing furnaces shown in FIG. 1, the exit section 26 of the oven 2 makes it possible, by regulating the speed of scrolling to a moderate level, for example 200 m / min, to carry out a survival treatment adapted to the nature of the metal, then to ensure the proper temperature setting of the strip before entering the zinc bath 41. It should be noted, in particular, that the current evolution of the market leads to making steels for which the aging, after annealing, is carried out at a relatively low temperature. FIG. 7, for example, shows a complete annealing cycle for a TRIP type steel which requires, after annealing, an isothermal retention in the Baitite transformation zone, that is to say around 290 C. In this case, the exit section 26 of the furnace must raise the temperature of the strip to a level compatible with the temperature of the zinc bath, for example 470 C. Figure 8, on the other hand, corresponds to the case of a common steel requiring over-aging, for example at 560 C. In this case, the temperature must be lowered to the temperature of the zinc bath. The temperature control section 26 will therefore be equipped with heating means, preferably by induction and cooling, preferably by neutral gas jet. It should be noted, on the other hand, that the galvanizing installation 4 placed, according to the invention, between the outlet section 26 of the oven 2 and the slow cooling section 25, is provided, at its output, with a quenching bath 45 at the output of which the strip is at a temperature close to ambient. Therefore, it is not necessary to pass the band in the slow cooling section 25, the quenching bath 45 being connected directly to the output accumulator 31. A combined line has thus been realized to ensure Depending on the case, the continuous annealing line functions in the furnace 2 and the final cooling section 25 and the continuous galvanizing line in the furnace 2 and the galvanizing plant 4 which ends with the quenching bath 45 Figure 9 shows schematically the arrangement of an installation for easily switching from one mode of operation to another. Since the annealing must be carried out in a controlled atmosphere, the annealing furnace 2, with the overaging section 26, is placed in a closed enclosure 8 provided at its base with a duct 80 which forms a branch with two outlets, respectively a first outlet 81 which plunges inside the metal bath 41 to seal, and a second outlet 82 which can be removably closed by a door 83. On the other hand, the section of slow cooling 25, also placed under a controlled atmosphere, is arranged in a sealed enclosure 8 'whose inlet 81' can be connected to the second outlet 82 of the duct 80, by a connecting chute 84 which can be moved, for example by pivoting, between the position shown in Figure 9 for which the chute 84 is connected in leaktight manner to the second outlet 82 of the conduit 80 and a spaced position allowing the passage of the next M band the path T2, at the outlet of the metal bath 41. This mobile chute 84 thus forms a bypass tunnel allowing, when it is put in place and the door 83 open, 25 to ensure the passage of the band M between the deflector roll Dl placed at the outlet of the oven and the cooling section 25, sealing between the two closed enclosures 8 and 8 'in which a neutral atmosphere is formed, for example a mixture of nitrogen and hydrogen . Fig. 10 is a block diagram of the operation of such a combined line. In order to carry out a galvanization after annealing, the strip M successively passes through the various sections of the annealing furnace 2 and, after being put into temperature in the outlet section 26, passes through the first outlet 81 of the duct 80 to open into the bath of annealing. zinc 41. As shown in FIG. 9, at the outlet of the quenching bath 45, the band M guided by the deflecting rollers D5, D'5, D7, passes below or, optionally, above the slow cooling 25 to be directed directly to the device 3 output of the line. To perform annealing alone, the connecting trough 84 is put in place and the door 83 is opened. From the deflector roll Dl, the band M passes into the connecting chute 84, then into the slow cooling section 25 which preferably terminates in a quenching tank 27, and is then directed by the drive rollers D8 to the output device 3 of the line. The installation is provided, on the other hand, with means not shown in FIG. 9, making it possible to cut the strip, either at a point 85, at the entrance into the connecting chute 84, or at a point 86, at the outlet of the cooling zone 25, upstream of the driving rollers D8. At the end of a continuous annealing campaign, the strip is cut at these two points 85 and 86, the mobile tunnel 84 is raised vertically and held against the front wall of the enclosure 8 'containing the cooling section 25. A band portion remains engaged in the tunnel 84 and the section 25. It will serve as a draw tape to put the line in annealing configuration in another campaign. Similarly, at the end of a galvanizing campaign, the strip is cut at two points, respectively 87 at the exit of the zinc bath 41 and 88 after the exit of the quenching bath 45. The hanging strands of the strip are attached to the frame members carrying the galvanizing plant 4 '. A portion of band remains engaged in this area and will serve as a draw tape to put the line in galvanizing configuration, in another campaign. To pass from one configuration to another, it suffices to weld or staple the relevant portion of the pull strip at the end of the new strip, at the level of the deflection roll D1, in the outlet pipe 80 of the zone overaging 26, then to advance this pulling strip to the shears 33, at the exit of the line, to eliminate it. The invention thus makes it possible to carry out either an annealing alone or a galvanization after annealing, in a combined line of the type shown in FIG. 5, whose overall size, in length, is of the same order as that of a line conventional continuous annealing system, insofar as the galvanizing plant, particularly if it is made in the particularly compact manner described above, can be incorporated inside the annealing line, between the overaging section and the section slow cooling. Therefore, the invention will find a particularly interesting application for the transformation of existing continuous annealing lines whose profitability is no longer assured due to the variety of qualities of sheet required and the resulting tonnage decline. Indeed, because the tonnages requested are lower, It will be possible to reduce the speed of scrolling and remove some units of the overaging section, the remaining portion of this section being sufficient to achieve the heat treatments necessary for most steel qualities currently required, the space thus cleared to accommodate a compact type galvanizing installation as described above.

  It should be noted, moreover, that a number of the equipment used in the deleted part of the over-aging section, in particular the gas jet cooling cells and the auxiliary members may be used in the galvanizing plant.

  The invention has further advantages and is not limited to the details of the embodiments which have been described as mere examples. For example, after sufficient cooling by the cells 44a, 44b placed in the path of the strip at the exit of the galvanizing bath 41, the band could pass over the cooling section 25 to descend directly into the quench bath 27 placed at the exit of this one. However, the use, according to the preferred embodiment of FIG. 9, of two separate quench tanks, respectively 45 at the outlet of the galvanizing plant 4 and 27 at the outlet of the cooling zone 25, makes it possible to to avoid pollution by zinc dust from the cooling tank 27 through which the uncoated annealed strips pass, in case of annealing operation alone.

Claims (4)

  1. Combined annealing and galvanizing line of a metal strip (1) comprising means for controlling the movement of the strip in a continuous line, between an input device (1) and an output device (3) of the line, successively in an annealing plant (2) and a galvanizing plant (4), the annealing plant (2) having a heating section (21), a section (22) for holding the band (M) at an annealing temperature, a first annealing section (23) after annealing, a section (24) for overaging and a second section (25) of slow cooling, and the galvanizing plant (4) having a section (Ti) ) inlet of the strip in a galvanic bath (41), a section (T2) of the metal bath of the strip covered on both sides with a coating, a section (T3) cooling the coating and a final cooling liquid bath (45) characterized by the fact that the galvanizing plant (4) is incorporated inside the annealing plant between the overaging section (24, 26) and the second cooling section (25) and that at the outlet of the overfill section (24, 26), the strip is directed by selective guide means (80) either to the galvanizing plant (4) and then, at the outlet of the final cooling bath (45), directly to the output device (3) of the line, either directly to the second cooling section (25) and the output device (3) of the line.   Combined line according to Claim 1, characterized in that the overflow section (26) and the second cooling section (25) of the annealing plant (2) are each placed in a sealed chamber (8, 8 '). ) filled with a protective gas and that the inlet section in the galvanic bath (41) is placed in a sealed conduit (80) forming a branch with an input connected to the output of the enclosure (6) of the overflow section (26) and two discharges, respectively a first outlet (81) immersed in the metal bath (41) and a second outlet (82) on which is releasably connected a channel (84) sealing connection with the enclosure (81) of the second cooling section (25) of the annealing plant, said second outlet (82) being provided with removable sealing means (83).   3. Combined line according to claim 2, characterized in that it comprises a plurality of baffle rollers defining two paths of the strip at the exit of the overaging section (16), respectively a first galvanization path having a section of inlet (Ti) in the metal bath passing through the first outlet (81) of the sealed duct (80), a section (T2) of the outlet of the metal bath (41), a section (T3) of cooling the coating before entering the the final cooling bath (45) and an outlet section (T4, T5) of said cooling bath (45) passing above or below the enclosure (8 ') in which the second cooling section is located (25), so as to connect directly to the output device (3) of the line, and a second annealing path only, passing through the trough (84) of removable connection between the second outlet (82) of the sealed conduit ( 80) and the enclosure (81) of the second cooling section (25). final cooling of the strip, respectively a first bath (45) placed at the outlet of the galvanizing installation (4), and a second bath (27) placed at the outlet of the second cooling section (25), the strip (M) being directed towards the outlet device (3) of the line after final cooling carried out, either in the first bath (45) after galvanization, or in the second bath (27) after an annealing treatment alone, without galvanization . 5. Combined line according to one of the preceding claims, characterized in that the cooling bath   4. Combined line according to one of claims 1, 2, 3, characterized in that it comprises two definal liquid baths (45) of the galvanizing plant (4), is placed above the metal bath ( 41) and shifted to the inlet side thereof to reduce the overall size of the galvanizing plant (4). 6. Combined line according to one of the preceding claims, characterized in that the overaging section (26) has a reduced length relative to the length usually required in a continuous annealing line and that the speed of travel of the strip is adapted to this reduced length in order to obtain the necessary heat treatment time. 7. A method of transforming a continuous annealing line of a metal strip into a combined annealing and galvanizing line, said annealing line (2) comprising means for continuously controlling the movement of the strip, successively, in an inlet device (1), a preheating section (21), an annealing section (22) holding the temperature at the desired level depending on the nature of the strip, a first section (23) of rapid cooling after annealing, a section (24) for overaging, a second section (25) for slow cooling in a protective atmosphere and an output device (3), characterized in that a part of the overaging section (24) is removed leaving the other sections in place and a galvanizing plant (4) is arranged inside the annealing line (2) in the space thus freed between the remaining part (26) of the over-aging section (4) and the second section (25) of slow cooling, and connected to the control means of the scroll so as to achieve a combined annealing and galvanizing line without increasing the overall length of the annealing line (2). Process according to Claim 7 for converting an annealing line into a combined annealing and galvanizing line, characterized in that the speed of movement of the strip between the input device (1) and the device ( 3) outlet of the band is suitable for the galvanizing process. Method according to Claim 8, characterized in that the galvanizing installation (4) replaces only a part (26) of the overflow section (24) and the running speed of the strip (M) is adjusted, in if necessary, so as to carry out a survival treatment in the remaining part (26) of the corresponding section (24). 10. Process according to claim 7, characterized in that the temperature in the annealing section is maintained at the desired level for the annealing, taking into account the nature of the strip and the speed of movement and that, between the exit of the quick-cooling section (21) and the entry into the galvanizing bath (41), the remaining portion (26) of the over-aging section (24) has combined heating and cooling means for adjusting the temperature of the band at a level suitable for the galvanizing process. 11. Method according to one of claims 7 to 10 for converting a continuous annealing line (1, 2, 3) into a combined annealing and galvanizing line, characterized in that the galvanizing installation (4 ) comprises means for controlling the running of the strip between a galvanizing metal bath (41) and a quenching bath (45), along a continuous scrolling path defined by a plurality of deflection rollers (D1D6) and having at least four parts, respectively a first portion (Ti) of connection between the quench section (23) and the entry into the metal bath (41), a second part (T2) of the exit of the metal bath (41) with coating thickness control, a third part (T3) for cooling the coating before entering the quenching bath (45) and a fourth part (T4, T5) for leaving the quenching bath (45), connecting directly to the exit section of the receipting line t, without passing through the slow cooling section (25). 12. A method according to claim 11, characterized in that, to adapt the overall size of the galvanizing installation (4) to the length of the space released in the line of discontinuit (2), the quenching bath (45) is placed above the metal bath (41) and shifted to the input side of the line, so that in the third cooling part (T3), the band (M) returns to the in the fourth portion (T4) of the quenching bath (45), passes above or below the metal bath (41) and then the cooling section (25) slow, to connect directly to the device (3) output of the line.