U.S. patent application number 17/606363 was filed with the patent office on 2022-07-07 for processing line for the continuous processing of metal strips having a dual purpose of producing strips that are annealed and dip-coated or not coated, and corresponding cooling tower and method for switching from one configuration to the other.
The applicant listed for this patent is FIVES STEIN. Invention is credited to Michel CLIN.
Application Number | 20220213574 17/606363 |
Document ID | / |
Family ID | |
Filed Date | 2022-07-07 |
United States Patent
Application |
20220213574 |
Kind Code |
A1 |
CLIN; Michel |
July 7, 2022 |
PROCESSING LINE FOR THE CONTINUOUS PROCESSING OF METAL STRIPS
HAVING A DUAL PURPOSE OF PRODUCING STRIPS THAT ARE ANNEALED AND
DIP-COATED OR NOT COATED, AND CORRESPONDING COOLING TOWER AND
METHOD FOR SWITCHING FROM ONE CONFIGURATION TO THE OTHER
Abstract
Disclosed is a treatment line for the continuous treatment of
metal strips having a dual purpose, i.e. for producing strips that
are annealed and dip-coated with a metal alloy and for producing
strips that are annealed and not coated, comprising a dual-purpose
cooling tower, i.e. for cooling strips that are annealed and not
coated in a non-oxidizing atmosphere and for air-cooling strips
that are annealed and coated.
Inventors: |
CLIN; Michel;
(Maisons-Alfort, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FIVES STEIN |
Maisons-Atfort |
|
FR |
|
|
Appl. No.: |
17/606363 |
Filed: |
April 28, 2020 |
PCT Filed: |
April 28, 2020 |
PCT NO: |
PCT/FR2020/050720 |
371 Date: |
October 25, 2021 |
International
Class: |
C21D 9/573 20060101
C21D009/573; C21D 9/56 20060101 C21D009/56; C21D 1/63 20060101
C21D001/63; C23C 2/28 20060101 C23C002/28 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2019 |
FR |
FR1904505 |
Claims
1. Cooling tower for a continuous treatment line for metal strips
having a dual purpose, which has a configuration for producing
strips that are annealed and dip-coated and a configuration for
producing strips that are annealed and not coated, characterized in
that it is intended to operate in both line configurations and it
comprises blowing means for cooling the strip selectively under a
non-oxidizing atmosphere in the configuration for uncoated annealed
strips and under air in the configuration for annealed and coated
strips.
2. Cooling tower according to claim 1, further comprising cooling
sections connected together to form a sealed cooling tunnel.
3. Cooling tower according to claim 2, wherein the sealed cooling
tunnel is further formed by connecting tunnels interposed between
two cooling sections and/or other elements.
4. Cooling tower according to claim 2, wherein the sealed tunnel
extends only over a rising strand.
5. Cooling tower according to claim 2, wherein the sealed tunnel
extends over a rising strand and a descending strand.
6. Cooling tower according to claim 1, 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 strip upstream of the
blowing means, means for recirculating and cooling said sampled
atmosphere, the blowing means being arranged to blow the sampled,
cooled and recirculated atmosphere.
7. Method for switching from one configuration to another of a
cooling tower according to claim 1, characterized in that it
comprises the following steps: for switching to the configuration
for producing strips that are annealed and not dip-coated with a
metal alloy, connecting the blowing means to a non-oxidizing
atmosphere, for switching to the configuration for producing
annealed and coated strips: connecting the blowing means to
air.
8. Cooling tower for a continuous treatment line for metal strips
having a dual purpose, which has a configuration for producing
strips that are annealed and dip-coated and a configuration for
producing strips that are annealed and not coated, comprising a
cooling tower according to claim 1.
9. Line according to claim 8, comprising, successively in the
direction of travel of the strip, an immersion tunnel, a bath area
provided with equipment in said configuration for producing strips
that are annealed and dip-coated in a metal alloy, wherein the bath
area is removable and can be replaced by a box designed to provide
a sealed fluid connection between the immersion tunnel and the
cooling tower.
10. Line according to claim 8, not comprising a final cooling
section.
11. Method for switching from one configuration to another of a
treatment line for the continuous treatment of metal strips having
a dual purpose according to claim 8, comprising the steps of the
method for switching from said configuration to said other
configuration of a cooling tower according to claim 7 and further
comprising the following steps: to switch to the configuration for
producing annealed strips not dip-coated in a metal alloy: removing
equipment from the bath area, and replacing said equipment with the
box, to switch to the configuration for producing annealed strip
dip-coated with a metal alloy: removing the box, and replacing with
the equipment of the bath area.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The invention relates to the field of production lines for
coils of metal strips having a dual purpose of producing either
strips that are annealed and dip-coated or strips that are annealed
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 that make it possible to give a line a dual
purpose, with an operation in annealing-only mode or in annealing,
then coating mode, with easy switching from one operating mode to
the other.
Technical Problems Addressed by the Invention
[0002] The market needs for high-strength steel coils are such that
steelmakers are looking for flexible means of production, allowing
the production of steels that are annealed only and steels that are
both annealed and coated. In addition, the 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 means that must be suitable
for a wide variety of thermal cycles, which is difficult to achieve
in a single line.
[0003] For example, for certain types of steel, it is customary,
after a rapid cooling section, to keep the strip at temperature for
a certain time before finalizing the heat treatment of the strip,
and therefore to take it out of the treatment furnace. In annealing
mode, the steel strip is generally cooled to a temperature below
200.degree. C., typically of approximately 150.degree. 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 that would
result from leaving the strip at too high a temperature. In the
present description, for this mode, the final cooling section
refers to the cooling section that has just been described.
[0004] In the 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.degree. C. for galvanizing, but it
is always much higher than the temperature of 150.degree. C.
targeted 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 a step of air cooling followed by water cooling to bring it
to a temperature close to ambient temperature. In the present
description, 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.
[0005] The design of the final cooling section of an annealing line
does not make it possible to prolong the maintenance of the strip
at temperature before starting the cooling. Thus, the start of
cooling of the strip necessarily begins as soon as the latter
enters the final cooling section. The cooling rate of the strip is
imposed by the concerned metallurgical structure. Thus, it is not
possible to reduce the cooling capacity so that the cooling of the
strip is distributed along the final cooling section. As a result,
the cooling of the strip can be completed long before the end of
the final cooling section.
[0006] When in coating mode, it may then be necessary to keep the
end of the final cooling section at a sufficient temperature before
the strip enters the coating bath, for example at 460.degree. C.
Indeed, if the strip is too cold when it arrives in the coating
bath, the bath will cool (since the power that can be installed on
a coating tank is limited) and will therefore generate mattes that
will cause problems with the coating quality or with the management
of the temperature of the bath. In addition, by being kept at
temperature, the final cooling section increases the hold time. The
final cooling section must therefore comprise heating means
allowing this.
[0007] It therefore becomes obvious that the final cooling section,
which is useful in annealing mode, generates additional stresses in
coated mode.
[0008] The present invention provides a solution to the problem of
using the same equipment, the final cooling section when it is
present, in annealing 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 annealing mode,
but which is not necessary in certain configurations in coated
mode.
[0009] To facilitate the description of the invention, reference
will be made to CAL mode to denote an operation of the line in
annealing mode only, without metallic coating during quenching, and
to CGL mode to denote an operation of the line in annealing and
coating mode during quenching, independent of the nature of the
coating. CAL is the acronym commonly used to denote an annealing
line (for "Continuous Annealing Line"), and CGL is the acronym used
to designate a galvanizing line (for "Continuous Galvanizing
Line").
TECHNICAL BACKGROUND
[0010] Document JP2004346359 is known, which discloses a cooling
tower used in a non-oxidizing atmosphere. The document does not
disclose a cooling section designed to operate with both line
configurations, that is to say, also in air.
[0011] Document EP0072874 is known, which describes an installation
with a dual configuration for manufacturing cold-rolled steel
sheets and hot-coated galvanized steel sheets, which comprises,
arranged successively in series, a heating zone, an equalization
zone, a primary cooling zone, an overaging zone, with the
possibility of controlled cooling, hot-dip galvanizing means,
intermediate cooling means, a secondary cooling zone, hardening
rolling means, and chemical treatment means. In the uncoated
annealed strip production configuration, the strip does not pass
through the cooling tower, which is circumvented by means of a
bypass to directly connect the overaging zone and the secondary
cooling zone.
[0012] EP3181709 describes a solution allowing the switch from a
CGL mode to a CAL mode and vice versa. It mainly consists in having
devices placed at the exit from the furnace, upstream of the
coating bath, to ensure the sealing of the furnace in CAL mode,
when the bath is removed and the bottom roll of the bath is
replaced, instead, by a deflector roll. This solution does not
address the technical problems mentioned above, since the final
cooling section of the furnace must be dimensioned to allow cooling
of the strip to approximately 150.degree. C. in CAL mode.
[0013] EP1325163 describes a combined steel treatment line with a
bypass installation for the coating zone and the cooling tower
allowing the switch from a CGL mode to a CAL mode and vice versa.
The bypass installation makes it possible to transfer the strip
from the annealing furnace to the water tank placed at the outlet
of the cooling tower without it being exposed to the ambient air.
The bypass installation is placed above the galvanizing pot and the
bath area equipment. This solution is not fully satisfactory, in
particular because it complicates the arrangement of the line and
it does not make it possible to benefit from the air cooling means
of the cooling tower in annealing mode.
[0014] In addition, these solutions do not adequately meet the
needs of steelmakers because, for a target steel quality, it may be
difficult to achieve all of 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.
[0015] The invention makes it possible to address these technical
problems with a dual-use CAL/CGL line that does not significantly
modify the thermal cycle of the steel grade targeted in CAL mode
and in CGL mode, while allowing optimized use of the cooling
equipment. These two aspects are obtained by allowing the cooling
equipment installed in the cooling tower to operate in different
modes, oxidizing or reducing for 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 THE INVENTION
[0016] To this end, there is provided, according to a first aspect
of the invention, a cooling tower for a continuous treatment line
for metal strips having a dual purpose, which has a configuration
for producing strips that are annealed and dip-coated and a
configuration for producing strips that are annealed and not
coated.
[0017] The tower according to the first aspect of the invention is
designed to operate in both line configurations. It comprises
blowing means for cooling the strip selectively under a
non-oxidizing atmosphere in the configuration for uncoated annealed
strips and under air in the configuration for annealed and coated
strips.
[0018] According to the invention, in the configuration for
producing uncoated annealed strips, the strip passes through the
cooling tower. Thus, the same cooling tower is used in each of the
configurations. It is thus possible to pool the cooling means of
the cooling tower.
[0019] Advantageously, the tower according to the first aspect of
the invention can further comprise cooling sections connected
together to form a sealed cooling tunnel. The sealed cooling tunnel
may further 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.
[0020] According to one embodiment, the tower according to the
first aspect of the invention may further comprise, 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 strip upstream of the
blowing means, means for recirculating and cooling said sampled
atmosphere, the blowing means being arranged to blow the sampled,
cooled and recirculated atmosphere.
[0021] According to a second aspect of the invention, there is
provided 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:
[0022] for switching to the configuration for producing strips that
are annealed and not dip-coated with a metal alloy, connecting the
blowing means to a non-oxidizing atmosphere, [0023] for switching
to the configuration for producing annealed and coated strips:
connecting the blowing means to air.
[0024] According to a third aspect of the invention, there is
proposed a continuous treatment line for metal strips having a dual
purpose, which has a configuration for producing strips that are
annealed and dip-coated and a configuration for producing strips
that are annealed and not coated.
[0025] The continuous treatment line according to the third aspect
of the invention comprises a cooling tower according to the first
aspect of the invention, or with one or more of its
improvements.
[0026] Preferably, the line comprises, successively in the
direction of travel of the strip, an immersion tunnel, a bath area
provided with equipment in said configuration for producing strips
that are annealed and dip-coated in a metal alloy, and a cooling
tower having a rising strand and a descending strand.
[0027] Preferably, the bath area is removable and can be replaced
by a box designed to provide a sealed fluid connection between the
immersion tunnel and the cooling tower.
[0028] According to one possibility, the cooling line according to
the third aspect of the invention does not have a final cooling
section.
[0029] According to a fourth aspect of the invention, there is
provided a method for switching from one configuration to another
of a treatment line for the continuous treatment of metal strips
having a dual, according to the third aspect of the invention, or
to 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: [0030] to switch to the
configuration for producing annealed strips not dip-coated in a
metal alloy: [0031] removing equipment from the bath area, and
[0032] replacing said equipment with the box (70), [0033] to switch
to the configuration for producing annealed strip dip-coated with a
metal alloy: [0034] removing the box, and [0035] replacing with the
equipment of the bath area.
BRIEF DESCRIPTION OF THE FIGURES
[0036] Other features and advantages of the invention will become
apparent from the detailed description that follows, for the
understanding of which reference is made to the appended drawings,
in which:
[0037] FIG. 1 is a schematic view of a dual-use CAL and CGL line,
in CGL mode, according to the state of the art,
[0038] FIG. 2 is a schematic view of the end of a dual-use CAL and
CGL line, in CGL mode according to one embodiment of the
invention,
[0039] FIG. 3 is a schematic view of the end of the dual-use CAL
and CGL line of FIG. 2, but in CAL mode,
[0040] FIG. 4 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,
[0041] FIG. 5 is a schematic view of the end of the dual-use CAL
and CGL line of FIG. 4, but in CAL mode,
[0042] FIG. 6 is a schematic view of the end of a dual-use CAL and
CGL line, in CGL mode according to another embodiment of the
invention,
[0043] FIG. 7 is a schematic view of a cooling section, in top
view, according to another embodiment of the invention,
[0044] FIG. 8 is a schematic view of the end of a dual-use CAL and
CGL line, in CGL mode according to another embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0045] Since the embodiments described hereinafter are not limiting
in nature, it is possible in particular to consider variants of the
invention that comprise only a selection of the features that are
described, provided that this selection of features is sufficient
to confer a technical advantage or to differentiate the invention
from the prior art. This selection comprises at least one
preferably functional feature without structural details, or with
only a portion of the structural details if this portion alone is
sufficient to confer a technical advantage or to differentiate the
invention from the prior art.
[0046] In the remainder of the description, elements having an
identical structure or similar functions will be designated by the
same references.
[0047] FIG. 1 schematically shows a portion of an annealing and
galvanizing line according to the state of the art. It is shown in
CGL mode, the devices that allow switching to CAL mode not being
shown. Likewise, for the sake of simplification, mechanical
equipment located at the line inlet, such as unwinders, welder,
accumulator, etc., and that placed at the line outlet, such as
accumulator, shears, rewinders, etc., are neither described nor
shown in the drawings. Likewise, installation equipment that is not
useful for understanding the invention is neither described nor
shown in the drawings, such as surface preparation equipment
(stripping, degreasing, rinsing, etc.) placed upstream of the
furnace, or a phosphating section placed at the exit from the
furnace. The heating, maintaining 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 that may or may not be oxidizing,
or by using a mixture of gas and liquid. Finally, most of the
equipment necessary for conveying the strip is neither described
nor shown, such as deflector rollers, strip traction rollers, strip
guide rollers, etc.
[0048] The line portion shown in FIG. 1 comprises, in the direction
of travel of the strip: [0049] an inlet airlock 1 for the strip B
in the furnace to prevent air from entering the furnace and to
limit the leakage of the protective gas present in the furnace
(typically a mixture of nitrogen and hydrogen), [0050] a strip
heating section 2, which may comprise a first direct flame heating
chamber and a second radiant tube heating chamber, [0051] a section
3 for maintaining the temperature of the strip, [0052] a slow
cooling section 4 of the strip, [0053] a rapid cooling section 5 of
the strip, [0054] an overaging section 6 of the strip, [0055] a
section 7 for final cooling of the strip, [0056] a section 8 for
heating the strip by induction, [0057] a section 9 for deflection
of the strip and for adjusting the traction of the strip, [0058] an
immersion tunnel 10 equipped with a sealing system 10a, for example
with shutters, not shown in this figure, [0059] a tunnel shoe 11
placed at the outlet 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 roll 12a allowing the
path of the strip to be modified, [0060] a system 13 for squeezing
the strip with gas blades, independent of whether it is equipped
with a system for stabilizing the strip, [0061] a cooling tower 14
equipped with: [0062] 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
movable to be placed offline when not in use, [0063] a section 16
for cooling the strip on the rising strand comprising four cooling
units 16a, 16b, 16c and 16d, [0064] two rollers 17 located at the
top of the cooling tower to ensure the deflection of the strip,
[0065] a section 18 for cooling the strip on the descending strand
comprising three cooling units 18a, 18b and 18c, [0066] a set 19 of
tension rollers with two rollers, [0067] a section 20 for
additional cooling by spraying water, comprising a water tank 20a,
a squeezing section 20b and a dryer 20c.
[0068] One embodiment of the invention is shown schematically in
FIG. 2, the line being in CGL mode. In this figure, compared to
FIG. 1, only the end of the line is shown. The capacity of this
line is identical to that of the line shown in FIG. 1, in
particular in terms of the maximum running speed of the strip and
of the reference format for the strip. The overaging section 6 is
similar to that of FIG. 1, that is to say, for a given strip
format, it allows the same residence time of the strip at the same
maintenance temperature. Conversely, the final cooling section 7 is
greatly reduced compared to the state of the art, only one strip
pass being retained. By "strip pass," the present description
refers to a vertical path of the strip, here from the bottom to the
top.
[0069] 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 thereof.
[0070] The cooling tower 14 comprises means on the rising strand
for cooling the rising strand.
[0071] Each of the cooling means may be a cooling section 30, as
shown in FIG. 2. The four cooling sections 30 can be sealingly
connected to one another so as to obtain a sealed cooling tunnel
31.
[0072] Alternatively, the cooling means can comprise other cooling
means. For example, the cooling sections 30 can be arranged on the
lower part of the rising strand, the other cooling means being on
the upper part.
[0073] Alternatively or in a complementary manner, the cooling
sections 30 can be connected to one another in a sealed manner by
means of connecting tunnels 38 (not shown) interposed between two
cooling sections. The connecting tunnels interposed between two
cooling sections also make up the sealed cooling tunnel 31.
[0074] A plenum 40 supplies gas to the cooling sections 30. A fan
41 is arranged on the connecting pipe between the plenum 40 and a
cooling section 30 so as to adjust the cooling capacity of the
cooling section separately from the other cooling sections. As a
variant, another flow rate regulator, such as a valve, can be
installed on this connecting pipe in addition to or as a
replacement for the fan 41. By equipping several cooling sections
in this way, it is possible to adjust the cooling curve of the
strip 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 makes it possible to keep 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 below, this exchanger 43 is particularly useful when the line
is operating in CAL mode.
[0075] In CGL mode, the coolant that circulates in the plenum 40,
the cooling sections 30 and the sealed cooling tunnel 31 is air.
Since the strip is coated, there is no problem of oxidation of the
strip.
[0076] A sealing airlock 13 is connected, directly or indirectly
via a connecting tunnel, in a sealed manner to the last cooling
section 30 in the direction of travel of the strip. Since this
airlock is useful in CAL operation, it will be described below. It
can be kept open in CGL mode.
[0077] In addition, in CGL mode, the equipment for the bath area is
in place. This equipment in particular comprises the tank
containing the coating bath 12, the bath mechanics (in particular a
bottom roll 12a), and the machine 13 for squeezing the strip at the
outlet of the bath. A galvannealing section 15 comprising a heating
zone 15a followed by a holding zone 15b is placed downstream of the
squeezing machine and upstream of the cooling sections 30. This
galvannealing section is removable to be taken offline when not in
use.
[0078] The shoe 11 at the end of the immersion tunnel 10 plunges
into the bath and provides a hydraulic seal, preventing the
atmosphere of the furnace from escaping. When the bath equipment is
removed to switch to CAL mode, the submerged part of the shoe is
"soiled" by residues from the bath. It is thus advantageous to have
a removable shoe so as to remove it when switching to CAL mode in
order to be connected to the immersion tunnel.
[0079] FIG. 3 illustrates the line shown in FIG. 2 after it has
been modified for operation in CAL mode. The equipment in the bath
area has been removed. A box 70 provides a sealed connection and
fluid continuity between the immersion tunnel 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
impermeable. The sealing system 10a of the immersion tunnel is kept
open. The box 70 comprises a deflector roll 71 arranged
substantially in place of the bottom roll 12a of the bath
mechanics.
[0080] The airlock 13 is kept closed in order to limit the gas
leakage rate, correspondingly reducing the operating cost of the
line. The sealed box 70 and the cooling sections 30 are thus
maintained under a protective atmosphere, which does not oxidize
the strip, as in the furnace. The intake of the fan 43 is connected
to the box 70 by means of a pipe 45. Thus, the gas blown onto the
strip through the cooling sections 30 is non-oxidizing gas for the
strip. This protective gas is thus recirculated by being sucked in
at the box 70, led to the plenum 40 via the pipe 45. The heat
exchanger 44 placed at the inlet of the plenum 40 makes it possible
to discharge the calories taken from the strip. The recirculated
gas is thus brought back to a suitable temperature before again
being projected onto the strip.
[0081] Furthermore, the installation comprises devices, not shown,
making it possible to quickly purge the equipment when switching
from a CAL to a 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 immersion tunnel, the box 70, the
cooling sections 30, the tunnel 31, the plenum 40 and the
connecting pipes.
[0082] Description of the Main Steps for Switching the Line from
CGL Mode to CAL Mode
[0083] The strip is stopped. The chamber 10a of the immersion
tunnel is closed so as to limit the leakage of the atmosphere from
the furnace during line conversion operations. The shoe 11 of the
immersion tunnel is removed, and the squeezing machine 13, the bath
mechanics and its bottom roll 12a and the bath 12 are removed. The
galvannealing section 15 is taken offline. The strip is cut. The
waterproof box 70 and the deflector roll 71 are installed in place
of the bath equipment. The two ends of the strip are welded
together. The sealed connections between the box 70 and the
immersion tunnel 10 on the one hand, and the first cooling section
30 on the other hand, are made. The connecting pipe 45 is connected
to the box 70 and to the intake 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 brought online. The box 70, the tunnel
31, the plenum 40 and the connecting pipes are purged with cooling
gas until the oxygen content in this equipment drops to the target
value. The airlock 10a of the immersion tunnel is open. The strip
is re-energized and set in motion again.
[0084] Description of the Main Steps for Switching the Line from
CAL Mode to CGL Mode
[0085] The strip is stopped. The airlock 10a of the immersion
tunnel is closed. The airlock 13 located at the outlet of the
rising strand of the strip in the cooling tower is open. The
cooling gas used in CAL mode is purged with air. The strip is cut
and each end of the strip is removed from the box 70. The
connecting pipe 45 between the box 70 and the plenum 40 is
disconnected. The sealed box 70 and the deflector roll 71 are
moved. The shoe 11 of the immersion tunnel, the bath 12, the bath
mechanics and the squeezing machine 13 are installed. The
galvannealing section 15 is brought online. The two ends of the
strip are welded together. The shoe 11 is immersed in the bath 12,
the airlock 10a is open, the strip is energized and then running.
Note that the chronology of operations to start production is the
same as that used when changing baths and bath equipment.
[0086] Another embodiment of the invention is shown schematically
in FIG. 4, the 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 that were placed
at the inlet of the plenum 40 in the previous example are replaced
by fans 41 and heat exchangers 42 placed on the connecting pipes
between the plenum 40 and the cooling sections 30. Like in the
previous example, the intake 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 pipe comprising an exhauster
51. A pipe 60 comprising a valve 62 connects the two plenums 40 and
50. The vent hole 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 pipe 60. The second plenum 50 collects the
cooling gas after exchange with the strip. This is of great
interest in CAL mode, as we will see below.
[0087] In FIG. 5, the line shown in FIG. 4 has been configured in
CAL mode. The equipment of the bath area has been removed and
replaced by the box 70 and its deflector roll 71. The valve 63 at
the intake of the plenum 40 is closed as well as the valve 61 at
the vent hole of the plenum 50. The box 70 and the tunnel 31 are
maintained in a non-oxidizing atmosphere. The valve 62 on the pipe
60 is opened so that cooling gas is recirculated. FIG. 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
discharge the calories extracted from the strip by 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 for venting the circuit
are open. The strip B is thus cooled with non-recirculated air.
[0088] In the case where the horizontal strand does not comprise
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.
[0089] According to another embodiment shown in FIG. 8, one or more
cooling sections 30 sealingly connected to one another 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 connecting tunnel 33 connects these
cooling sections 30 with those of the rising strand.
[0090] According to the embodiment of the invention shown in FIG.
8, the descending strand also comprises a set of cooling sections
30 sealingly connected to one another so as to obtain a sealed
cooling tunnel 34. All of the cooling means of 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. 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 connecting strand between the rising strand and
the descending strand.
[0091] Sealingly connected end to end, the cooling sections 30 and
the connecting tunnel(s) 31, 32, 33, 34, 35, 36 constitute a sealed
cooling tunnel 37. This can extend: [0092] on the rising strand
only by being made up of the tunnel 31, [0093] on the rising strand
and the horizontal strand consisting of tunnels 31, 32 and 33,
[0094] on the rising strand, the horizontal strand, and the
descending strand consisting of the tunnels 31, 32, 33, 34 and 35
or the tunnels 31, 34 and 36.
[0095] According to another embodiment of the invention that is 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 on the strip. For example, one 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. Likewise, one 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 to the second plenum.
[0096] 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.
[0097] As will be readily understood, the invention is not limited
to the examples that have just been described, and numerous
modifications can be made to these examples without departing from
the scope of the invention. In addition, the various features,
forms, variants, and embodiments of the invention can be grouped
together in various combinations as long as they are not
incompatible or mutually exclusive.
* * * * *