FR3095452A1 - Dual Purpose Metal Strip Continuous Processing Line - Google Patents

Abstract

Double-purpose metal strip continuous processing line, that is, for the production of annealed and dip-coated strips with a metal alloy and the production of uncoated annealed strips, comprising a tower (14) of dual-purpose cooling, that is to say for cooling under a non-oxidizing atmosphere of uncoated annealed strips and for air cooling of annealed and coated strips. Figure for the abstract: Figure 3

Description

Dual Purpose Metal Strip Continuous Processing Line

Technical field of the invention

The invention relates to the field of production lines for coils of dual-use metal strips making it possible to produce either annealed and dip-coated strips, or annealed strips only, that is to say uncoated. The coating can be of any type, based on zinc, aluminum, a mixture of zinc and aluminum, or any other component. More specifically, the invention relates to devices and methods which make it possible to make a line dual-use, with operation in annealing mode only or in annealing then coating mode, with an easy transition from one operating mode to the 'other.

Technical problems to which the invention responds

Market needs for high-strength steel coils are such that steelmakers are looking for flexible means of production, making it possible to produce annealed steels only and annealed and coated steels. Moreover, the new steels do not require the same thermal cycles when they are annealed only and when they are annealed and coated, hence a line configuration with heating and cooling means which must be adapted for a wide variety of thermal cycles which is difficult to achieve in a single line.

For example, for certain types of steel, it is customary, after a rapid cooling section, to maintain the strip at temperature for a certain time before finalizing the heat treatment of the strip and therefore removing it from the treatment furnace. In annealing mode, the steel strip is generally cooled to a temperature below 200°C, typically around 150°C, in a cooling section, before it leaves the furnace, in order to avoid the problems of oxidation of the strip in the open air which would result from leaving the strip at too high a temperature. In the present description, the final cooling section designates, for this mode, the cooling section which has just been described.

In coated mode, it is necessary to bring the strip to a temperature close to that of the coating bath before it is immersed therein. This temperature varies according to the type of coating produced. It is, for example, 460° C. for galvanizing, but it is always much higher than the target temperature of 150° C. at the end of cooling in annealing mode. On leaving the coating bath, the strip is in the open air. It can then undergo a heat treatment modifying the quality of the coating (galvannealing) before an air cooling step followed by water cooling to bring it to a temperature close to that of the ambient temperature. In the present description, the final cooling section means, for this mode, the last cooling section upstream of the coating bath, in the running direction of the strip.

The design of the final cooling section of an annealing line does not allow the strip to be held at temperature for longer before starting the cooling. Thus, the start of cooling of the strip necessarily begins as soon as it enters the final cooling section. The cooling rate of the strip is imposed by the targeted metallurgical structure. It is thus not possible to reduce the cooling capacity so that the cooling of the strip is distributed along the final cooling section. As a result, strip cooling can be completed well before the end of the final cooling section.

When in coating mode, it may then be necessary to maintain the end of the final cooling section at a sufficient temperature before the strip enters the coating bath, for example at 460°C. Indeed, if the strip arrives too cold in the coating bath, the bath will cool down (the power that can be installed on a coating tank being limited) and therefore generate mattes which cause coating quality or management problems. bath temperature. Also, by being held at temperature, the final cooling section increases the hold time. The final cooling section must therefore include heating means allowing this.

It therefore becomes evident that the final cooling section, useful in the annealed mode, generates additional stresses in the coated mode.

The present invention proposes a solution to the problem of using the same equipment, the final cooling section when it is present, in annealed mode and in coated mode. The present invention also minimizes problems caused by the presence of said final cooling section, which is always necessary in annealed mode, but which is not necessary according to certain configurations in coated mode.

To facilitate the description of the invention, we will speak of CAL mode to designate operation of the line in annealing mode only, without metal dip coating, and of CGL mode to designate operation of the line in annealing mode and dip coating , whatever the nature of the coating. CAL is the acronym commonly used to designate a annealing line (for English Continuous Annealing Line ) and CGL is the one used to designate a line of galvanization (for English Continuous Galvanizing Line ).

Technical background

EP3181709 describes a solution allowing the transition from a CGL mode to a CAL mode and vice versa. It mainly consists of having devices placed at the outlet of the oven, upstream of the coating bath, to ensure the tightness of the oven in CAL mode, when the bath is removed and the bottom roller of the bath replaced, instead of , by a deflector roller. This solution does not solve the technical problems stated above since the final cooling section of the oven must be dimensioned to allow cooling of the strip to approximately 150° C. in CAL mode.

EP1325163 describes a combined steel treatment line with a bypass installation of the coating zone and the cooling tower allowing the transition from a CGL mode to a CAL mode and vice versa. The bypass installation allows the strip to be transferred from the furnace for annealing to the water tank placed at the outlet of the cooling tower without it being exposed to the ambient air. The bypass installation is arranged above the galvanizing pot and the equipment in the bathing area. This solution is not fully satisfactory, in particular because it complicates the layout of the line and it does not allow the benefit of the air cooling means of the cooling tower in annealing mode.

Moreover, these solutions do not satisfactorily meet the needs of steelmakers because, for a targeted quality of steel, it may be difficult to carry out all the desired thermal cycles in CAL and CGL modes due to the routing constraints of the strip in successive sections and the cooling means available therein.

The invention makes it possible to respond to these technical problems with a CAL/CGL dual-use line which does not significantly modify the thermal cycle of the steel grade in question in CAL mode and in CGL mode while allowing optimized use of the equipment. of colds. These two aspects are achieved by allowing the cooling equipment installed in the cooling tower to operate in different modes, oxidizing or reducing for the strip depending on the cooling fluid used, allowing the capacity of the final cooling section in the furnace to be reduced. , see for removing it.

To this end, it is proposed, according to a first aspect of the invention, a cooling tower for a continuous treatment line for dual-use metal strips having a production configuration for annealed and dip-coated strips and a production configuration uncoated annealed strips.

The tower according to the first aspect of the invention comprises blowing means for cooling the strip selectively under a non-oxidizing atmosphere in the configuration of uncoated annealed strips and under air in the configuration of annealed and coated strips.

Advantageously, the tower according to the first aspect of the invention may further comprise cooling sections connected together to form a sealed cooling tunnel. The sealed cooling tunnel can also be formed by connecting tunnels interposed between two cooling sections and/or other elements. The sealed tunnel can extend only on the rising strand, or on the rising strand and on the descending strand.

According to one embodiment, the tower according to the first aspect of the invention may further comprise , depending on the running direction of the strip, in the configuration for producing uncoated annealed strips, means for sampling an uncoated atmosphere. present at the level of the strip upstream of the means for blowing, means for recirculating and cooling said withdrawn atmosphere, the blowing means being arranged to blow the withdrawn, cooled and recirculated atmosphere.

According to a second aspect of the invention, there is proposed a method for switching from one configuration to another of a cooling tower according to the first aspect of the invention, or one or more of its improvements, comprising the following steps:

• for the transition to the configuration for the production of annealed and uncoated strips with a metal alloy, connection of the blowing means to a non-oxidizing atmosphere,
• for the transition to the production configuration of annealed and coated strips: connection of the blowing means to air.

According to a third aspect of the invention, there is provided a continuous treatment line for dual-use metal strips having a configuration for producing annealed and dip-coated strips and a configuration for producing uncoated annealed strips, said line comprising , successively in the running direction of the strip, a bell drop, a bath area equipped with equipment in said configuration for the production of strips annealed and dip-coated with a metal alloy, and a cooling tower having a strand up and a bit down.

The cooling tower of the treatment line according to the third aspect of the invention is in accordance with the first aspect of the invention, or one or more of its improvements, and the bath zone is removable and is replaceable by a box arranged to ensure a sealed fluidic connection between the bell descent and the cooling tower.

According to one possibility, the cooling line according to the third aspect of the invention does not include a final cooling section.

According to a fourth aspect of the invention, there is proposed a method for switching from one configuration to another of a continuous processing line for double metal strips, according to the third aspect of the invention, or the one or more of its improvements, comprising the steps of the method for switching from said configuration to said other configuration of a cooling tower according to the second aspect of the invention, or one or more of its improvements, and further comprising the following steps:

• for the transition to the production configuration of annealed strips not dipped coated with a metal alloy:
  • removal of equipment from the bathing area, and
  • replacement of said equipment by the box (70),
• for the transition to the production configuration of annealed strips dipped coated with a metal alloy:
  • removal of the box, and
  • replacement by the equipment of the bathing area.

Brief description of figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

is a schematic view of a dual-use CAL and CGL line, in CGL mode, according to the state of the art,

is a schematic view of the end of a dual-use CAL and CGL line, in CGL mode according to an exemplary embodiment of the invention,

is a schematic view of the end of the CAL and CGL dual-use line in Figure 2, but in CAL mode,

is a schematic view of the end of a dual-use CAL and CGL line, in CGL mode according to a second embodiment of the invention,

is a schematic view of the end of the CAL and CGL dual-use line in Figure 4, but in CAL mode,

is a schematic view of the end of a dual-use CAL and CGL line, in CGL mode according to another exemplary embodiment of the invention,

is a schematic view of a cooling section, seen from above, according to another embodiment of the invention,

is a schematic view of the end of a dual-use CAL and CGL line, in CGL mode according to another exemplary embodiment of the invention.

Detailed description of the invention

The embodiments described below being in no way limiting, variants of the invention may in particular be considered comprising only a selection of characteristics described, subsequently isolated from the other characteristics described, if this selection of characteristics is sufficient. to confer a technical advantage or to differentiate the invention from the state of the prior art. This selection includes at least one feature, preferably functional without structural details, or with only part of the structural details if only this part is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art .

In the remainder of the description, elements having an identical structure or analogous functions will be designated by the same references.

Figure 1 schematically represents a portion of an annealing and galvanizing line according to the state of the art. It is represented in CGL mode, the equipment allowing the switch to CAL mode not being represented. Similarly, for the sake of simplification, the mechanical equipment located at the line input, such as unwinders, welders, accumulators, etc., and those placed at the line output, such as accumulators, shears, rewinders, etc., are not neither described nor shown in the drawings. Similarly, neither described nor shown in the drawings are the installation equipment not useful for understanding the invention, such as surface preparation equipment (stripping, degreasing, rinsing, etc.) placed upstream of the furnace, or a phosphating section placed at the exit of the furnace. The heating, holding and cooling sections are represented very schematically in the drawings by rectangles. They may comprise several chambers, each of which may have different heating or cooling means, for example with heating by direct flames, by radiation or by induction and cooling by blowing a cooling gas, by spraying a liquid oxidizing or not, or by using a mixture of gas and liquid. Finally, most of the equipment necessary for the path of the strip is also not described or shown, such as deflector rollers, strip traction rollers, strip guide rollers, etc.

The portion of line represented in Figure 1 comprises, in the direction of travel of the strip:

• an airlock 1 at the entrance of strip B into the furnace to prevent air from entering the furnace and to limit the escape of protective gas present in the furnace (typically a mixture of nitrogen and hydrogen),
• a strip heating section 2, which may include a first heating chamber with direct flames and a second heating chamber with radiant tubes,
• a section 3 for maintaining the temperature of the strip,
• a section 4 for slow strip cooling,
• a rapid strip cooling section 5,
• a section 6 of over-aging (overaging) of the strip,
• a section 7 for final cooling of the strip,
• a section 8 for heating the strip by induction,
• a section 9 for belt deflection and belt traction adjustment,
• a bell lowering 10 equipped with a sealing system 10a, for example with shutters, not shown in this figure,
• a bell shoe 11 placed at the outlet of the bell descent and immersed in a bath 12 of molten coating, said bath 12 of hot coating serving to coat the strip, itself equipped with a bottom roller 12a making it possible to change the path of the tape,
• a strip wiping system 13 with gas blades, whether or not equipped with a strip stabilization system,
• a cooling tower 14 equipped with:
  • a galvannealing section 15, comprising equipment 15a for heating the strip by induction and a chamber 15b for maintaining the temperature of the strip, said section 15 being able to be moved to be placed offline when it is not in use ,
  • a strip cooling section 16 on the rising strand comprising 4 cooling units 16a, 16b, 16c and 16d,
  • two rollers 17 located at the top of the cooling tower to ensure the deflection of the strip,
  • a strip cooling section 18 on the descending strand comprising 3 cooling units 18a, 18b and 18c,
  • a set 19 of tension rollers with two rollers,
  • a section 20 for additional cooling by spraying water, comprising a water tank 20a, a wiping section 20b and a dryer 20c.

An exemplary embodiment of the invention is shown schematically in Figure 2, the line being in CGL mode. In this figure, compared to Figure 1, only the end of the line is shown. The capacity of this line is identical to that of the line represented in FIG. 1, in particular in terms of maximum tape running speed and reference format for the tape. Section 6 of over-ageing is similar to that of Figure 1, that is to say that it allows, for a given tape format, the same residence time of the tape at the same holding temperature. Conversely, the final cooling section 7 is greatly reduced compared to the state of the art, only one tape pass being retained. By "tape pass" the present description designates a vertical path of the tape, here from bottom to top.

In another embodiment of the invention, depending on the strip formats and the thermal cycles to be carried out, the final cooling section 7 may be absent, the cooling of the strip being carried out only in the cooling tower, and, if necessary, downstream of it.

The cooling tower 14 comprises, on the rising strand, means for cooling the rising strand.

Each of the cooling means can be a cooling section 30, as shown in Figure 2. The four cooling sections 30 can be connected in a sealed manner to each other so as to obtain a sealed cooling tunnel 31.

Alternatively, the cooling means may include other cooling means. For example, the cooling sections 30 can be arranged on the lower part of the riser, the other cooling means being on the upper part.

Alternatively or additionally, the cooling sections 30 can be connected in a leaktight manner to each other via connecting tunnels 38 (not shown) interposed between two cooling sections. The connecting tunnels interposed between two cooling sections also constitute the sealed cooling tunnel 31 .

A plenum 40 supplies gas to the cooling sections 30. A fan 41 is arranged on the connecting duct between the plenum 40 and a cooling section 30 so as to adjust the cooling capacity of the cooling section separately by compared to other cooling sections. As a variant, another flow adjustment device, such as a valve, can be installed on this connecting duct in addition to or in substitution for the fan 41. By thus equipping several cooling sections, it is possible to adjust the curve strip cooling along the cooling tower. A fan 43 and a heat exchanger 44 are arranged at the intake of the plenum 40, the latter being in the open air. The heat exchanger keeps the cooling gas at the desired temperature at the inlet of the cooling sections by means of a heat transfer fluid, for example water. As we will see later, this exchanger 43 is particularly useful when the line is operating in CAL mode.

In CGL mode, the cooling fluid which circulates in the plenum 40, the cooling sections 30 and the sealed cooling tunnel 31 is air. Since the tape is coated, there is no problem of oxidation of the tape.

A sealing lock 13 is connected, directly or indirectly via a connecting tunnel, in a sealed manner to the last cooling section 30 in the running direction of the strip. This airlock finding its usefulness in CAL operation, it will be described later. It can be held open in CGL mode.

Moreover, in CGL mode, the equipment in the bathing area is in place. This equipment includes in particular the tank containing the coating bath 12, the bath mechanics (in particular a bottom roller 12a), and the machine 13 for wringing the strip out of the bath. A galvannealing section 15 comprising a heating zone 15a followed by a holding zone 15b, is placed downstream of the spin-drying machine and upstream of the cooling sections 30. This galvannealing section is removable to be placed offline. when not needed.

The shoe 11 at the end of the bell descent 10 plunges into the bath and provides a hydraulic seal, preventing the atmosphere of the furnace from escaping. When the bathing equipment is evacuated to switch to CAL mode, the submerged part of the sculpin is "soiled" by bath residues. It is thus advantageous to have a removable shoe so that it can be removed when switching to CAL mode to be connected to the bell descent.

Figure 3 illustrates the line shown in Figure 2 after it has been modified for CAL mode operation. The amenities in the bathing area have been removed. A box 70 provides a sealed connection and fluid continuity between the lower bell 10 and the first cooling section 30 of the rising strand of the cooling tower 14, or the galvannealing section 15 if the latter is present because it is not removable. In this case, the galvannealing section must be sealed. The sealing system 10a of the bell companionway is kept open. The box 70 includes a deflector roller 71 arranged substantially in place of the bottom roller 12a of the bath mechanism.

The airlock 13 is kept closed in order to limit the gas leak rate, thereby reducing the operating cost of the line. The sealed box 70 and the cooling sections 30 are thus maintained under a protective atmosphere, non-oxidizing for the strip, as in the oven. The suction of the fan 43 is connected to the box 70 by means of a duct 45. Thus, the gas blown onto the strip via the cooling sections 30 is non-oxidizing gas for the strip. This protective gas is thus recirculated by being sucked at the level of the box 70, led to the plenum 40 via the conduit 45. The heat exchanger 44 placed at the inlet of the plenum 40 makes it possible to evacuate the calories taken from the band. The recirculated gas is thus brought back to an adequate temperature before being projected onto the strip again.

Furthermore, the installation includes devices, not shown, allowing the equipment to be purged quickly when switching from a CAL to CGL operating mode and vice versa. Purging makes it possible to replace the air with a non-oxidizing atmosphere, and vice versa, in particular in the bell descent, the box 70, the cooling sections 30, the tunnel 31, the plenum 40 and the connecting ducts.

Description of the main steps for switching the line from CGL mode to CAL mode

The band is stopped. The airlock 10a of the bell descent is closed so as to limit the escape of the atmosphere from the furnace during line conversion operations. The shoe 11 of the bell descent is removed, the spin-drying machine 13, the bath mechanics and its bottom roller 12a, the bath 12 are removed. The galvannealing section 15 is placed offline. The tape is cut. The watertight box 70 and the deflector roller 71 are installed in place of the bathing equipment. The two ends of the strip are welded together. The sealed connections between the box 70 and the bell descent 10 on the one hand, and the first cooling section 30 on the other hand, are made. The connecting duct 45 is connected to the casing 70 and to the suction of the fan 43. The airlock 13 located at the outlet of the rising strand of the strip in the cooling tower is closed and put into operation. The box 70, the tunnel 31, the plenum 40 and the connecting ducts are purged with cooling gas until the oxygen content in these equipment drops to the target value. The airlock 10a of the bell descent is open. The tape is re-energized and moving.

Description of the main steps for the passage of the line from CAL mode to CGL mode

The band is stopped. The airlock 10a of the bell descent is closed. The airlock 13 located at the outlet of the rising strand of the strip in the cooling tower is open. The coolant gas used in CAL mode is purged with air. The strip is cut and each end of the strip is taken out of the casing 70. The connecting conduit 45 between the casing 70 and the plenum 40 is disconnected. The sealed box 70 and the deflector roller 71 are moved. The shoe 11 of the bell descent, the bath 12, the bath mechanics, the wringing machine 13 are installed. Section 15 of galvannealing is placed in line. The two ends of the strip are welded together. The sabot 11 is immersed in the bath 12, the airlock 10a is opened, the strip is put under tension and then scrolled. It should be noted that the chronology of start-up operations in production is the same as that used when changing baths and equipping the bath.

Another embodiment of the invention is shown schematically in Figure 4, the line being in CGL mode. The configuration of the cooling tower 14 is similar to that of Figure 1. In this embodiment, the fan 44 and the heat exchanger 43 which were placed at the entrance to the plenum 40 in the previous example are replaced by fans 41 and heat exchangers 42 placed on the connecting ducts between the plenum 40 and the cooling sections 30. As in the previous example, the suction of the plenum 40 is in the open air in CGL mode, the valve 63 being open. A second plenum 50 is placed at the outlet of the cooling sections 30. Each cooling section is connected to the second plenum 50 by a conduit comprising an exhauster 51. A conduit 60 comprising a valve 62 connects the two plenums 40 and 50. The exhaust of the plenum 50 is in the open air in CGL mode, the valve 61 being open and the valve 62 being closed so that there is no flow in the conduit 60. The second plenum 50 collects the gas from cooling after exchange with the tape. This finds all its interest in CAL mode as we will see below.

In Figure 5, the line shown in Figure 4 has been configured in CAL mode. The equipment in the bathing area has been removed and replaced by box 70 and its deflector roller 71. Valve 63 at the intake of plenum 40 is closed as well as valve 61 at the exhaust of plenum 50. Box 70 and the tunnel 31 are maintained under a non-oxidizing atmosphere. Valve 62 on line 60 is opened so that cooling gas is recirculated. Figure 7 schematically illustrates another embodiment of the invention comprising a recirculation loop 49 per cooling section 30. In CAL mode, a non-oxidizing gas is recirculated in the circuit 49 by means of a fan 41, the two valves 46 being open and the two valves 47, 48 being closed, the exchanger 42 making it possible to evacuate the calories extracted from the strip with a heat transfer fluid. In CGL mode, the recirculation circuit is closed by means of the two valves 46, the two valves 47 and 48 venting the circuit to air are open. Strip B is thus cooled with non-recirculated air.

In the case where the horizontal strand does not include cooling sections 30, as shown in FIG. 6, a tunnel 36 provides a sealed connection between the cooling sections 30 of the descending strand and those of the rising strand.

According to another exemplary embodiment shown in Figure 8, one or more cooling sections 30 connected in a sealed manner to each other so as to obtain a sealed cooling tunnel 32 are placed on the horizontal connecting strand between the rising strand and the descending strand of the cooling tower. A link tunnel 33 connects these cooling sections 30 with those of the riser.

According to the exemplary embodiment of the invention shown in Figure 8, the descending strand also comprises a set of cooling sections 30 connected in a sealed manner to each other so as to obtain a sealed cooling tunnel 34 . All of the means for cooling the descending strand of the tower can be cooling sections 30. If not all of them are, the cooling sections 30 are arranged on the upper part of the descending strand, the other units being on the lower part. low. In the upper part of the tower, a tunnel 35 provides a sealed connection between the cooling sections 30 of the descending strand and those of the horizontal strand connecting the rising strand and the descending strand.

Connected end to end in a sealed manner, the cooling sections 30 and the connecting tunnel(s) 31, 32, 33, 34, 35, 36 form a sealed cooling tunnel 37 . This can extend:

. on the rising strand only by being made up of the tunnel 31,

. on the rising strand and the horizontal strand, consisting of tunnels 31, 32 and 33,

. on the rising strand, the horizontal strand, and the descending strand, consisting of tunnels 31, 32, 33, 34 and 35 or tunnels 31, 34 and 36.

According to another embodiment of the invention, not shown, the cooling sections 30 are supplied by at least two plenums 40 and the cooling gas is collected by at least two plenums 50 after blowing onto the strip. For example, a plenum 40a serves the cooling sections of the rising strand and a second plenum 40b serves the cooling sections of the descending strand, any cooling sections of the horizontal strand being connected to the first or to the second plenum. In the same way, a plenum 50a collects the cooling gas coming from the cooling sections of the rising strand and a second plenum 50b collects that coming from the cooling sections of the descending strand, any cooling sections of the horizontal strand being connected to the first or in the second plenum.

As a variant embodiment, the fluid used in the cooling sections 30 can be a mixture of a gas and a sprayed liquid, for example water in CGL mode and a non-oxidizing liquid for the strip in CAL mode.

Of course, the invention is not limited to the examples which have just been described and many adjustments can be made to these examples without departing from the scope of the invention. In addition, the different features, forms, variants and embodiments of the invention may be associated with each other in various combinations insofar as they are not incompatible or exclusive of each other.

Claims (10)

Cooling tower (14) for a continuous processing line for dual-use metal strips having a production configuration for annealed and dip-coated strips and a configuration for producing uncoated annealed strips,
characterized in that it comprises blowing means for cooling the strip selectively under a non-oxidizing atmosphere in the configuration of uncoated annealed strips and under air in the configuration of annealed and coated strips. Cooling tower (14) according to the preceding claim, further comprising cooling sections (30) interconnected to form a sealed cooling tunnel (37). Cooling tower according to the preceding claim, in which the sealed cooling tunnel is further formed by connecting tunnels (38) interposed between two cooling sections and/or other elements (31, 32, 33, 34, 35, 36). Cooling tower according to claim 2 or 3, in which the sealed tunnel (37) extends only on a rising strand. Cooling tower according to any one of Claims 2 to 4, in which the sealed tunnel (37) extends over an ascending strand and a descending strand. Cooling tower according to any one of the preceding claims, further comprising, in the direction of travel of the strip, in the configuration for producing uncoated annealed strips, means for sampling a non-oxidizing atmosphere present at the level of the band upstream of the blowing means, the means for recirculating and cooling said withdrawn atmosphere, the blowing means being arranged to blow the withdrawn, cooled and recirculated atmosphere. Method for switching from one configuration to another of a cooling tower (14) according to any one of the preceding claims, characterized in that it comprises the following steps:

• for the transition to the configuration for the production of annealed and uncoated strips with a metal alloy, connection of the blowing means to a non-oxidizing atmosphere,
• for the transition to the production configuration of annealed and coated strips: connection of the blowing means to air.

Line for the continuous processing of dual-use metal strips having a configuration for the production of annealed and dip-coated strips and a configuration for the production of uncoated annealed strips, said line comprising, successively in the running direction of the strip, a descent of bell, a bath zone provided with equipment in said configuration for the production of strips annealed and dip-coated with a metal alloy, and a cooling tower (14) having a rising strand and a falling strand,
characterized in that the cooling tower is in accordance with any one of the preceding cooling tower claims and in that the bath zone is removable and can be replaced by a box (70) arranged to ensure a sealed fluidic connection between the bell descent and the cooling tower. Line according to the preceding claim, comprising no final cooling section (7). Method for changing from one configuration to another of a continuous treatment line for dual-use metal strips according to one of Claims 8 or 9, comprising the steps of the method for changing from said configuration to said other configuration of a cooling tower (14) according to claim 7 and further comprising the steps of:

• for the transition to the production configuration of annealed strips not dipped coated with a metal alloy:
  • removal of amenities from the bathing area (11, 12, 12a, 13), and
  • replacement of said equipment by the box (70),
• for the transition to the production configuration of annealed strips dipped coated with a metal alloy:
  • removal of the casing (70), and
  • replacement by the equipment of the bathing area (11, 12, 12a, 13).