阅读说明：本技术 用于金属带材的连续处理、具有生产退火且浸涂或未涂覆的带材的双重目的的处理生产线，和对应的冷却塔以及从一种构造切换到另一种构造的方法 (Treatment line for the continuous treatment of metal strips with the dual purpose of producing annealed and dip-coated or uncoated strips, and corresponding cooling tower and method of switching from ) 是由 M·克林 于 2020-04-28 设计创作，主要内容包括：公开了一种具有双重目的、即用于生产退火且用金属合金浸涂的带材和用于生产退火且未涂覆的带材的用于金属带材的连续处理的处理生产线,其包括双重目的冷却塔(14),即用于在非氧化气氛中冷却退火且未涂覆的带材以及用于对退火且涂覆的带材进行空气冷却。(A processing line for the continuous treatment of metal strips with a dual purpose, i.e. for producing annealed and dip-coated strips with a metal alloy and for producing annealed and uncoated strips is disclosed, comprising a dual purpose cooling tower (14), i.e. for cooling the annealed and uncoated strips in a non-oxidizing atmosphere and for air-cooling the annealed and coated strips.)

1. A cooling tower (14) for a continuous processing line of metal strips with a dual purpose, having a configuration for producing annealed and dip-coated strips and a configuration for producing annealed and uncoated strips,

characterized in that the cooling tower is intended to operate in two line configurations and it comprises blowing means for cooling the strip selectively under a non-oxidizing atmosphere in the configuration for uncoated annealed strip and under air in the configuration for annealed and coated strip.

2. The cooling tower (14) according to the preceding claim, further comprising cooling sections (30) connected together to form a sealed cooling channel (37).

3. Cooling tower according to the previous claim, wherein said sealed cooling channel is also formed by a connecting channel (38) interposed between two cooling sections and/or other elements (31, 32, 33, 34, 35, 36).

4. A cooling tower according to claim 2 or 3, wherein the sealing channel (37) extends only over an up-going section.

5. Cooling tower according to one of claims 2 to 4, in which the sealing channel (37) extends over an ascending section and a descending section.

6. Cooling tower according to one of the preceding claims, further comprising: in a configuration for producing an uncoated annealed strip, in the direction of travel of the strip, means for sampling the non-oxidizing atmosphere present at the strip upstream of said blowing means, means for recirculating and cooling said sampled atmosphere, said blowing means being arranged to blow the sampled, cooled and recirculated atmosphere.

7. Method for switching a cooling tower (14) according to one of the preceding claims from one configuration to another, characterized in that it comprises the steps of:

-connecting the blowing device to a non-oxidizing atmosphere for switching to a configuration for producing an annealed and not dip-coated strip with a metal alloy,

-for switching to the configuration for producing the annealed and coated strip: connecting the blowing device to the air.

8. Cooling tower for a continuous processing line of metal strips with a dual purpose, having a configuration for producing annealed and dip-coated strips and a configuration for producing annealed and uncoated strips, comprising a cooling tower (14) according to one of the preceding cooling tower claims.

9. Production line according to the preceding claim, comprising, in succession in the direction of travel of the strip: a dip channel; a bath provided with equipment in the configuration for producing annealed and dip-coated strip in metal alloy, wherein the bath is removable and replaceable by a tank (70) designed to provide a sealed fluid connection between the immersion channel and the cooling tower.

10. Production line according to one of the two preceding claims, which does not comprise a final cooling section (7).

11. Method for switching a processing line for the continuous processing of metal strips with a dual purpose according to one of claims 8 to 10 from one configuration to another, comprising the steps of the method for switching a cooling tower (14) from said configuration to said other configuration according to claim 7, and further comprising the steps of:

switching to a configuration for producing an annealed strip not dip-coated in a metal alloy:

removing equipment from the bath (11, 12a, 13), and

replacing the equipment with a tank (70),

switching to a configuration for producing an annealed strip dip-coated with a metal alloy:

removing the box (70), and

replacing the equipment of the bath (11, 12a, 13).

Technical Field

The present invention relates to the field of production lines for coils of metal strip, with the dual purpose of producing annealed and dip-coated strips or strips which are only annealed (that is to say uncoated). The coating may be of any type based on zinc, aluminum, a mixture of zinc and aluminum, or any other composition. More specifically, the invention relates to an apparatus and a method that enable a production line to have a dual purpose, with operation in an annealing only mode or in an annealing followed by coating mode, and with easy switching from one operating mode to another.

Technical problem to be solved by the invention

The market demand for high strength steel coils is such that steel manufacturers are seeking flexible ways of production, allowing the production of only annealed steels as well as both annealed and coated steels. Furthermore, new steels do not require the same thermal cycles when they are annealed only and when they are annealed and coated; this results in a line configuration with heating and cooling devices that must be adapted to a wide variety of thermal cycles, which is difficult to achieve in a single line.

For example, for certain types of steel, after the rapid cooling section, the strip is generally kept at a certain temperature for a certain time, and then the heat treatment of the strip is completed and thus taken out of the treatment furnace. In the annealing mode, the steel strip is usually cooled in the cooling section to a temperature below 200 ℃ (typically about 150 ℃), and then it leaves the furnace to avoid oxidation problems of the strip in open air, which can occur when leaving the strip at too high a temperature. In this specification, for this mode, the final cooling section refers to the cooling section just described.

In the coating mode, the temperature of the strip must be brought close to the temperature of the coating bath before the strip is immersed in the coating bath. The temperature varies depending on the type of coating produced. For example 460 ℃ for galvanization, but it is always much higher than the target temperature of 150 ℃ at the end of cooling in annealing mode. Upon exiting the coating bath, the strip was in open air. It may then undergo a thermal treatment (galvanizing) modifying the quality of the coating, and then a step of air cooling followed by water cooling to bring its temperature close to ambient temperature. In this specification, for this mode, the final cooling section refers to the last cooling section upstream of the coating bath in the direction of travel of the strip.

The design of the final cooling section of the annealing line does not allow for prolonged temperature maintenance of the strip before cooling is initiated. Therefore, the start of strip cooling must start immediately after the strip enters the final cooling section. The cooling rate of the strip is imparted by the metallographic structure involved. Thus, the cooling capacity cannot be reduced so that the cooling of the strip is distributed along the final cooling section. Thus, the cooling of the strip may be completed well before the end of the final cooling section.

When in coating mode, it may be necessary at this point to maintain the end of the final cooling section at a sufficient temperature (e.g., 460 ℃) before the strip enters the coating bath. In fact, if the strip is too cold when it reaches the coating bath, the bath will be cold (because of the limited power that can be installed on the coating bath), thus creating issues that will lead to coating quality problems or bath temperature management problems. Further, the final cooling section increases the hold time by being held at a certain temperature. Therefore, the final cooling section must include heating means that allow this.

It is therefore clear that the final cooling section useful in the annealing mode generates additional pressure in the coating mode.

The present invention provides a solution to the problem of using the same equipment (final cooling section, when present) in the annealing mode and in the coating mode. The present invention also minimizes the problems caused by the presence of the final cooling section, which is always necessary in the annealing mode, but not in certain configurations in the coating mode.

For the purpose of illustrating the invention, reference will be made to the CAL mode for the operation of the production line only in the annealing mode (no metal coating during quenching), and to the CGL mode for the operation of the production line in the coating mode during annealing and quenching (regardless of the nature of the coating). CAL is an acronym commonly used to designate an annealing line ("continuous annealing line"), while CGL is an acronym used to designate a galvanizing line ("continuous galvanizing line").

Background

Document JP2004346359 is known, which discloses a cooling tower used in a non-oxidizing atmosphere. This document does not disclose a cooling section designed to operate in two line configurations, that is to say also in air.

Document EP0072874 is known, which describes a plant with a double construction for manufacturing cold rolled steel sheets and hot-coated zinc steel sheets, comprising, in succession, a heating zone, an equalization zone, a primary cooling zone, an overaging zone (which has the possibility of controlled cooling), a hot-dip galvanizing installation, an intermediate cooling installation, a secondary cooling zone, a hardening-rolling installation and a chemical treatment installation. In the production configuration of the uncoated annealed strip, the strip does not pass through a cooling tower, which is circumvented by directly connecting the overaging zone and the secondary cooling zone by means of a bypass.

EP3181709 describes a solution that allows switching from CGL mode to CAL mode and vice versa. It essentially consists of placing some equipment at the outlet of the furnace (upstream of the coating bath) to ensure the tightness of the furnace in CAL mode (when the bath is removed and the bottom roller of the bath is replaced by a deflection roller). This solution does not solve the above mentioned technical problem, since the final cooling section of the furnace must be dimensioned to allow cooling of the strip to about 150 ℃ in CAL mode.

EP1325163 describes a combined steel treatment line with a bypass facility for the coating zone and the cooling tower, which allows switching from CGL mode to CAL mode and vice versa. The bypass facility enables the strip to be transferred from the annealing furnace to a water bath placed at the outlet of the cooling tower without exposing it to ambient air. The bypass facility is placed above the galvanizing pot and bath facility. This solution is not entirely satisfactory, in particular because it complicates the layout of the production line and it does not make it possible to benefit from the air cooling means of the cooling tower in the annealing mode.

Furthermore, these solutions do not adequately meet the needs of steel manufacturers, since it may be difficult to achieve all the desired thermal cycles in CAL and CGL modes for the target steel quality, due to the path restrictions in the continuous sections and cooling devices available in the strip.

The present invention enables solving these technical problems with a dual-purpose CAL/CGL line that does not significantly modify the thermal cycle of the steel grade targeted for CAL mode and CGL mode, while allowing to optimize the use of cooling equipment. These two aspects are achieved by: allowing the cooling equipment installed in the cooling tower to operate in different modes, oxidizing or reducing the strip depending on the coolant used, allowing the capacity of the final cooling section in the furnace to be reduced, or even allowing it to be eliminated.

Disclosure of Invention

To this end, according to a first aspect of the present invention, a cooling tower for a continuous processing line of metal strips is provided with a dual purpose, having a configuration for producing an annealed and dip-coated strip and a configuration for producing an annealed and uncoated strip.

The tower according to the first aspect of the invention is designed to operate in two line configurations. It comprises an air blowing device for selectively cooling the strip under a non-oxidizing atmosphere in the configuration for uncoated annealed strips and under air in the configuration for annealed and coated strips.

According to the invention, in a configuration for producing an uncoated annealed strip, the strip is passed through a cooling tower. Thus, the same cooling tower is used in each of the configurations. Therefore, the cooling device of the (pool) cooling tower can be intensively used.

Advantageously, the tower according to the first aspect of the invention may further comprise cooling sections connected together to form a sealed cooling channel. The sealed cooling channel may also be formed by a connecting channel interposed between two cooling sections and/or other elements. The sealing channel can only extend over the upstream section or over the upstream section and over the downstream section.

According to an embodiment, the tower according to the first aspect of the invention may further comprise: in a configuration for producing an uncoated annealed strip, in the direction of travel of the strip, means for sampling a non-oxidizing atmosphere present at the strip upstream of blowing means, means for recirculating and cooling said sampled atmosphere, the blowing means being arranged to blow the sampled, cooled and recirculated atmosphere.

According to a second aspect of the present invention there is provided a method for switching one or more of the cooling tower according to the first aspect of the present invention or a modification thereof from one configuration to another, the method comprising the steps of:

for switching to the configuration for producing annealed strip not dip-coated with metal alloy, connecting the blowing device to a non-oxidizing atmosphere,

for switching to the configuration for producing the annealed and coated strip: the blowing device is connected to the air.

According to a third aspect of the present invention, a continuous processing line for metal strips with a dual purpose is proposed, having a configuration for producing an annealed and dip-coated strip and a configuration for producing an annealed and uncoated strip.

The continuous processing line according to the third aspect of the invention comprises one or more of the cooling towers according to the first aspect of the invention or with modifications thereof.

Preferably, the production line comprises, in succession in the direction of travel of the strip: a dip channel; a bath provided with equipment in the configuration for producing an annealed and dip-coated strip in a metal alloy; and a cooling tower having an up leg and a down leg.

Preferably, the bath is removable and can be replaced by a tank designed to provide a sealed fluid connection between the immersion channel and the cooling tower.

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

According to a fourth aspect of the present invention, there is provided a method for switching a process line for the continuous treatment of metal strip having a dual purpose according to the third aspect of the present invention or one or more of its improvements from one configuration to another configuration, the method comprising the steps of the method for switching a cooling tower from said configuration to said other configuration according to the second aspect of the present invention or one or more of its improvements, and further comprising the steps of:

switching to a configuration for producing an annealed strip that is not dip coated in a metal alloy:

-removing the equipment from the bath, and

-replacing the equipment with a box (70),

switching to the configuration for producing an annealed strip dip-coated with a metal alloy:

-removing the box, an

-replacing with equipment of the bath area.

Drawings

Other features and advantages of the present invention will become apparent from the following detailed description, to which reference is made for an understanding of the accompanying drawings, in which:

figure 1 is a schematic diagram of a dual purpose CAL and CGL production line in CGL mode according to the prior art,

figure 2 is a schematic diagram of the end of a dual purpose CAL and CGL production line in CGL mode according to one embodiment of the present invention,

FIG. 3 is a schematic view of the end of the dual-purpose CAL and CGL production line of FIG. 2 but in CAL mode,

figure 4 is a schematic diagram of the end of a dual purpose CAL and CGL production line in CGL mode according to a second embodiment of the present invention,

FIG. 5 is a schematic view of the end of the dual-purpose CAL and CGL production line of FIG. 4 but in CAL mode,

figure 6 is a schematic diagram of the end of a dual-purpose CAL and CGL production line in CGL mode according to another embodiment of the present invention,

figure 7 is a schematic top view of a cooling section according to another embodiment of the invention,

FIG. 8 is a schematic diagram of the end of a dual purpose CAL and CGL production line in CGL mode, according to another embodiment of the present invention.

Detailed Description

Since the embodiments described below are not limiting in nature, in particular, variants of the invention can be considered which comprise only a selection of the features described, provided that the selection of the features is sufficient to confer technical advantages or to distinguish the invention from the prior art. This option includes at least one preferred functional feature without structural details or with only some structural details if they are sufficient to confer technical advantages or to distinguish the invention from the prior art.

In the rest of the description, elements having the same structure or similar function will be denoted by the same reference numerals.

Figure 1 schematically shows a part of an annealing and galvanising line according to the prior art. It is shown in CGL mode and the devices that are allowed to switch to CAL mode are not shown. Also, for the sake of simplicity, the mechanical equipment located at the inlet of the production line (such as unwinders, welders, accumulators, etc.) and placed at the outlet of the production line (such as accumulators, guillotines, rewinders, etc.) are neither described nor shown in the drawings. Also, the installation equipment not helpful to understand the invention, such as the surface preparation equipment (stripping), degreasing, rinsing, etc.) placed upstream of the furnace, or the phosphating section placed at the outlet of the furnace, is neither described nor shown in the drawings. The heating, maintenance and cooling sections are very schematically indicated by rectangles in the figure. They may comprise several chambers, each of which may have different heating or cooling means, for example heating by direct flame, by radiation or by induction, and cooling by blowing a cooling gas, by spraying a liquid which may or may not be oxidising, or by using a mixture of gas and liquid. Finally, most of the equipment necessary to convey the strip (such as deflection rolls, strip pulling rolls, strip guiding rolls, etc.) is neither described nor shown.

The section of the production line shown in fig. 1 comprises, in the direction of travel of the strip:

an inlet air lock 1 for the strip B in the furnace, for preventing the entry of air into the furnace and limiting the leakage of protective gas (generally a mixture of nitrogen and hydrogen) present in the furnace,

a strip heating section 2, which may comprise a first direct flame heating chamber and a second radiant tube heating chamber,

a section 3 for maintaining the temperature of the strip,

a slow cooling section 4 of the strip,

a section 5 of rapid cooling of the strip,

an overaging section 6 of the strip,

a section 7 for the final cooling of the strip,

for heating the section 8 of strip by induction,

a section 9 for deflection of the strip and for adjusting the traction of the strip,

an immersion channel 10 equipped with a sealing system 10a (for example with shutters, not shown in the figures),

a tunnel shoe 11 placed at the exit of the immersion tunnel and immersed in a bath 12 of molten coating, said bath 12 of hot coating being used to coat the strip, itself equipped with a bottom roller 12a allowing to modify the path of the strip,

a system 13 for pressing (squeezing) the strip with a knife, whether or not equipped with a system for stabilizing the strip,

a cooling tower 14 equipped with:

a galvanised 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 movable to be taken offline when not in use,

a section 16 for cooling the strip on the up run, comprising four 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 section 18 for cooling the strip on the rundown section, comprising three cooling units 18a, 18b and 18c,

a set of tensioning rollers 19 with two rollers,

a section 20 for additional cooling by spraying water, comprising a water tank 20a, a pressing section 20b and a dryer 20 c.

One embodiment of the present invention is schematically illustrated in fig. 2, the production line being in CGL mode. In this figure, only the end of the production line is shown, compared to fig. 1. The capacity of this line is the same as that of the line shown in figure 1, in particular in terms of the maximum running speed of the strip and the reference specifications for the strip. The overaging section 6 is similar to that of fig. 1, that is, it allows the same dwell time of the strip at the same maintenance temperature for a given strip gauge. In contrast, the final cooling section 7 is considerably shortened compared to the prior art, leaving only one strip pass (strip pass). By "strip pass" the present description refers to the vertical path (here from bottom to top) of the strip.

In another embodiment of the invention, depending on the strip gauge and the thermal cycle to be performed, the final cooling section 7 may not be present, the cooling of the strip being performed only in the cooling tower and, if necessary, downstream thereof.

The cooling tower 14 includes means on the up section for cooling the up section.

Each of the cooling devices may be a cooling section 30, as shown in fig. 2. The four cooling sections 30 may be sealingly connected to each other to obtain a sealed cooling channel 31.

Alternatively, the cooling device may comprise other cooling devices. For example, the cooling section 30 may be arranged at a lower portion of the ascending section, and the other cooling device may be arranged at an upper portion of the ascending section.

Alternatively or in a complementary manner, the cooling sections 30 can be connected to one another in a sealed manner by means of a connecting channel 38 (not shown) interposed between the two cooling sections. The connecting channel interposed between the two cooling sections also constitutes the sealed cooling channel 31.

A plenum (plenum)40 supplies gas to the cooling section 30. A fan 41 is arranged on the connecting pipe between the plenum 40 and the cooling section 30 in order to adjust the cooling capacity of this cooling section separately from the other cooling sections. As a variant, in addition to the fan 41 or instead of the fan 41, another flow regulator (such as a valve) may be mounted on the connection pipe. By equipping several cooling sections in this way, the cooling curve of the strip along the cooling tower can be adjusted. The fan 43 and the heat exchanger 44 are arranged at the air inlet of the plenum 40, the latter (heat exchanger 44) being in open air. The heat exchanger makes it possible to maintain the cooling gas at a desired temperature at the inlet of the cooling section by means of a heat transfer fluid, for example water. This exchanger 43 is particularly useful when the production line is operating in CAL mode, as we will see below.

In the CGL mode, the coolant circulating in the plenum 40, the cooling section 30, and the seal cooling channel 31 is air. Since the strip is coated, there is no problem of oxidation of the strip.

The sealing damper 13 is connected in a sealing manner directly or indirectly via a connecting channel to the last cooling section 30 in the running direction of the strip. Since the damper is useful in CAL operation, it will be described below. It may remain on in CGL mode.

In addition, in CGL mode, the equipment for the bath area is in place. The plant comprises in particular a tank containing a coating bath 12, bath mechanisms (in particular bottom rollers 12a) and a machine 13 for pressing the strip at the outlet of the bath. The galvanising section 15 of the heating zone 15a, including the heel holding zone 15b, is placed downstream of the extrusion machine and upstream of the cooling section 30. The galvanized section is removable to be placed offline when not in use.

A shoe 11 at the end of the immersion channel 10 is inserted into the bath and provides a hydraulic seal to prevent the furnace atmosphere from escaping. When the bath equipment is removed to switch to CAL mode, the submerged portion of the shoe can be "fouled" by residue in the bath. It is therefore advantageous to have a removable shoe to remove it when switching to CAL mode, in order to connect to the immersion channel.

FIG. 3 shows the production line shown in FIG. 2 after modification for operation in CAL mode. The equipment in the bath zone has been removed. The tank 70 provides a sealed connection and fluid continuity between the immersion channel 10 and the first cooling section 30 or the galvanising section 15 of the ascending section of the cooling tower 14, if the latter is present because it is not removable. In this case, the galvanized section must be impermeable. The sealing system 10a of the immersion channel remains open. The box 70 comprises a deflection roller 71 arranged substantially in the position of the bottom roller 12a of the bath mechanism.

The damper 13 remains closed to limit the gas leakage rate and correspondingly reduce the operating costs of the production line. The sealed box 70 and the cooling section 30 are therefore maintained under a protective atmosphere which does not oxidize the strip as in a furnace. The air inlet of the fan 43 is connected to the case 70 by means of a duct 45. Thus, the gas blown onto the strip through the cooling section 30 is a non-oxidizing gas of the strip. The shielding gas is thus recirculated by being drawn in at the box 70, being directed to the plenum 40 via the duct 45. A heat exchanger 44 placed at the inlet of the plenum 40 makes it possible to reject the calories extracted from the strip. The recirculated gas is thus brought back to the appropriate temperature before being sprayed again on the strip.

Furthermore, the facility includes equipment, not shown, so that it can quickly purge equipment when switching from CAL to CGL mode of operation, and vice versa. The purging makes it possible to replace air (and vice versa) with a non-oxidizing atmosphere, in particular air immersed in the channels, the tank 70, the cooling section 30, the channels 31, the plenum 40 and the connecting pipes.

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

The strip is stopped. The chamber 10a of the immersion channel is closed to limit leakage of atmosphere from the furnace during the line change operation. The shoe 11 of the immersion channel is removed and the press machine 13, bath mechanism and its bottom roll 12a and bath 12 are removed. The galvanized section 15 is placed off-line. And cutting the strip. A waterproof case 70 and a deflecting roller 71 are installed instead of the bath equipment. The two ends of the strip are welded together. A sealing connection is made between the tank 70 and the immersion channel 10 on the one hand and between the tank 70 and the first cooling section 30 on the other hand. The connection pipe 45 is connected to the case 70 and the air inlet of the fan 43. The air lock 13 at the exit of the up run of the strip in the cooling tower is closed and placed on line. The tank 70, channels 31, plenum 40 and connecting tubes are purged with cooling gas until the oxygen content in the equipment drops to a target value. The air lock 10a of the immersion channel is opened. The strip is re-energized and brought into motion again.

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

The strip is stopped. The air lock 10a of the immersion channel is closed. The air lock 13 at the exit of the ascending section of the strip in the cooling tower is opened. The cooling gas used in the CAL mode is purged with air. The strip is cut and each end of the strip is removed from the magazine 70. The connecting pipe 45 between the tank 70 and the pressurizing chamber 40 is disconnected. Moving the sealing box 70 and the deflection roller 71. A shoe 11, a bath 12, bath mechanism and a press machine 13 are installed in the immersion channel. The galvanized section 15 is placed on-line. The two ends of the strip are welded together. The shoe 11 is immersed in the bath 12, the damper 10a is opened, the strip is energised and then caused to run. It should be noted that the time sequence of the operation for starting the production is the same as the time sequence used when changing the bath and bath equipment.

Another embodiment of the invention is schematically illustrated in fig. 4, the production line being in CGL mode. The configuration of the cooling tower 14 is similar to that of fig. 1. In this variant embodiment, the fan 44 and the heat exchanger 43 placed at the inlet of the plenum 40 in the previous example are replaced by the fan 41 and the heat exchanger 42 placed on the connecting duct between the plenum 40 and the cooling section 30. As in the previous example, the inlet of the plenum 40 is in open air in the CGL mode, and the valve 63 is open. A second plenum 50 is placed at the outlet of the cooling section 30. Each cooling section is connected to the second plenum 50 by a duct that includes an exhaust 51. A tube 60 including a valve 62 connects the two plenums 40 and 50. In CGL mode, the vents of the plenum 50 are in open air, valve 61 is open and valve 62 is closed so that there is no flow in the tube 60. The second plenum 50 collects the cooling gas after exchange with the strip. This has great significance in the CAL mode, as we will see below.

In FIG. 5, the manufacturing line shown in FIG. 4 has been configured in CAL mode. The equipment of the bath zone has been removed and replaced by the box 70 and its deflection rollers 71. The valve 63 at the inlet of the plenum 40 and the valve 61 at the vent of the plenum 50 are closed. The housing 70 and the channel 31 are maintained in a non-oxidizing atmosphere. The valve 62 on the pipe 60 is opened so that the cooling gas is recirculated. FIG. 7 schematically illustrates another embodiment of the invention, wherein each cooling section 30 includes a recirculation loop 49. In CAL mode, the non-oxidizing gas is recirculated in the circuit 49 by means of the fan 41, the two valves 46 are open and the two valves 47, 48 are closed, the exchanger 42 making it possible to discharge the calories extracted from the strip by the heat transfer fluid. In CGL mode, the recirculation circuit is closed by means of two valves 46; two valves 47 and 48 for venting the circuit are opened. Thus, the strip B is cooled by non-recirculating air.

In the case where the horizontal segment does not include a cooling section 30, as shown in FIG. 6, the channels 36 provide a sealed connection between the cooling sections 30 of the downstream segment and those of the upstream segment.

According to another embodiment shown in fig. 8, one or more cooling sections 30, which are sealingly connected to each other to obtain a sealed cooling channel 32, are placed on the horizontal connecting section between the ascending section and the descending section of the cooling tower. Connecting channels 33 connect the cooling sections 30 with those of the upstream section.

According to the embodiment of the invention shown in fig. 8, the downstream section further comprises a set of cooling sections 30 sealingly connected to each other to obtain a sealed cooling channel 34. All cooling means of the down section of the tower may be cooling sections 30. If not all cooling sections 30, the cooling sections 30 are arranged in the upper part of the down section and the other units are arranged in the lower part of the down section. In the upper part of the tower, the channels 35 provide a sealed connection between the cooling sections 30 of the descending section and those of the horizontal connecting sections between the ascending and descending sections.

The cooling section 30 and the connecting channels 31, 32, 33, 34, 35, 36 sealingly connected end-to-end constitute a sealed cooling channel 37. The seal cooling channel 37 may:

by being constituted by the channel 31 and extending only over the ascending section,

consists of channels 31, 32 and 33 extending over the up-going and horizontal sections,

consists of channels 31, 32, 33, 34 and 35 or channels 31, 34 and 36 extending over the up, horizontal and down sections.

According to another embodiment of the invention, not shown, the cooling section 30 is supplied by at least two plenums 40 and the cooling gas is collected by at least two plenums 50 after being blown onto the strip. For example, one plenum 40a serves as a cooling section for the up leg and a second plenum 40b serves as a cooling section for the down leg, with any cooling section of the horizontal leg connected to either the first or second plenum. Likewise, one plenum 50a collects cooling gas from the cooling section of the up leg, a second plenum 50b collects cooling gas from the cooling section of the down leg, and any cooling section of the horizontal leg is connected to either the first or second plenum.

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

As will be readily appreciated, the present invention is not limited to the embodiments just described, and many modifications may be made to these examples without departing from the scope of the present invention. Furthermore, the various features, forms, variations and embodiments of the invention may be grouped together in various combinations as long as they are not mutually compatible or mutually exclusive.