FR3063738A1 - CONTINUOUS LINE COMPRISING AT LEAST ONE CHAMBER IN WHICH THE BAND LENGTH IS ADJUSTABLE - Google Patents

Abstract

Continuous annealing or galvanizing line of a metal strip (1) comprising a chamber (2) delimited by external walls (3) for separating the atmosphere (4) present inside said chamber from the air located outside, the outer walls (3) being thermally insulated to limit the thermal losses of the chamber, said chamber comprising means (5) for adjusting the length of strip present in the chamber.

Description

(57) Continuous annealing or galvanizing line of a metal strip (1) comprising a chamber (2) delimited by external walls (3) making it possible to separate the atmosphere (4) present inside said chamber the air located outside, the outer walls (3) being thermally insulated to limit the heat losses from the chamber, said chamber comprising means (5) making it possible to adjust the length of strip present in the chamber.

The invention relates to continuous annealing or galvanizing lines for steel strips. By galvanization, we designate here and thereafter all dip coatings, whether they are coatings of zinc, aluminum, zinc alloys and aluminum, or any other type of coating. The invention relates more particularly to at least one chamber of a line having, among other things, means making it possible to adjust the length of strip present in said chamber.

In a continuous line, strips of steel undergo different successive heat treatments by passing through different heating or cooling chambers. Tape accumulators are conventionally placed at the input and output of the line. They make it possible to ensure continuous movement of the strip in the line processing sections in spite of the stops in the movement of the strip necessary at the entry and exit of the line during reel change operations.

For example, the accumulator placed at the line entry makes it possible to ensure a continuous scrolling of the strip in the oven while the strip is stopped for a few seconds in the inlet section to make the connection between two consecutive coils. By oven, we mean all the chambers that allow the strip to be brought to and maintained at the annealing temperature and then cooled in an atmosphere. An oven may, for example, include a preheating chamber, a heating chamber, a holding chamber, a slow cooling chamber, a rapid cooling chamber and an aging chamber. In normal line operation, with an identical tape running speed upstream and downstream of the accumulator, the latter is full, that is to say that it comprises a maximum length of strip. When the running of the strip is stopped at the level of the entry section, the entry accumulator is emptied to maintain a constant running of the strip in the section of the line located downstream of the accumulator.

A tape accumulator on a vertical line consists of a set of idler rollers mounted on a fixed frame and a set of idler rollers mounted on a movable frame. The strip passes successively on a roller placed on the fixed frame then on a roller placed on the movable frame, with a vertical running pass between the two rollers. To fill or empty the accumulator, the mobile chassis is movable so as to vary the length of the vertical scrolling pass between two rollers. Thus, when the accumulator is empty, the mobile chassis is located closest to the fixed chassis and when the accumulator is full, the mobile chassis is located furthest from the fixed chassis. The length of the strip located in the accumulator is thus directly linked to the position of the mobile chassis. During the filling phases of the accumulator, the tape running speed is higher in the input accumulator, and upstream of it, than in the sections placed downstream of the accumulator.

îo The accumulators present on the continuous lines operate in air, the strip being in the open air, and at room temperature.

According to a first aspect of the invention there is provided a chamber arranged to receive a strip of steel running in a continuous annealing or galvanizing line, said chamber being delimited by external walls for separation of an atmosphere present at the inside said chamber of an atmosphere, for example air, present outside said chamber, the external walls being thermally insulated, said chamber comprising adjustment means arranged to modify a length of strip present in the chamber, for example a tape accumulator.

Insulating the outer walls with refractory materials, such as ceramic fiber, helps limit heat loss from the chamber.

The chamber may also include piloting means arranged to pilot the adjustment means so as to modify the length of strip present in the chamber.

According to one embodiment, the chamber can comprise a set of rolls for transporting a steel strip, the vertical position of which in said chamber is adjustable by lifting means.

Advantageously, the chamber may also include means for heating the strip.

Preferably, the chamber may also include sealing means arranged to separate the interior and exterior atmospheres from said chamber.

The room may also include means for controlling the interior atmosphere.

According to a second aspect of the invention, there is provided a continuous annealing or galvanizing line arranged to receive a steel strip, comprising a chamber according to the first aspect of the invention, or one or more of its improvements. .

According to one possibility, the chamber can be arranged at the line entry according to the invention, for example so as to play the function of line entry accumulator.

According to one possibility, the means for heating the strip can be means for preheating the strip.

The chamber can be arranged in the line according to the invention so as to be a chamber for maintaining the temperature of the strip.

According to one embodiment, the line according to the invention can comprise two ovens, and the chamber can be arranged so as to receive the strip downstream from the first oven and to present said strip upstream from the second oven.

According to a third aspect of the invention, a method is proposed comprising a running of a steel strip in a chamber of a continuous annealing or galvanizing line, said chamber being delimited by external walls for separating an atmosphere present inside said chamber of an atmosphere present outside said chamber, the outer walls being thermally insulated, said chamber comprising adjustment means arranged to modify a length of strip present in the chamber.

Advantageously, the method according to the invention may include a modification of the length of strip present in the chamber according to the nature of the strip being treated in the line and / or according to changes in strip formats or thermal cycles during transition phases.

The process chamber according to the invention can perform the function of line entry accumulator and / or the strip preheating function.

According to one possibility, the method comprises a step of heating or maintaining the temperature of the strip in the chamber and a step of controlling the atmosphere of said chamber.

According to one embodiment, the method according to the invention may also comprise a step of piloting the means for adjusting the chamber so as to modify the length of strip present in the chamber.

According to yet another aspect of the invention, there is provided a computer program product, downloadable from a communication network and / or stored on a medium readable by computer and / or executable by a microprocessor, and loadable in an internal memory a calculation unit, comprising program code instructions which, when executed by the calculation unit, implement the steps of the method according to the third aspect of the invention, or one or more of his improvements.

îo The present invention thus provides the production of a chamber which may comprise an accumulator which can operate in a sealed manner under a controlled atmosphere and at a controlled temperature. Thus, this chamber can be integrated in different places in a continuous annealing or galvanizing line to provide a new solution to different needs.

A metal strip running in a continuous annealing or galvanizing line follows a thermal cycle intended to give it the desired mechanical properties. For example, after rising to an annealing temperature, the strip is maintained at this temperature for a few seconds before being cooled. After cooling, the strip can be reheated and maintained at a tempering or aging temperature (“overaging”).

The duration of temperature maintenance may be different depending on the steel grades and / or the mechanical properties sought. The holding time can be taken into account for the dimensioning of the corresponding chamber from the reference strip format (i.e. reference width; reference thickness) and the maximum speed of movement of the strip in the oven. For larger strip formats (ie width / thickness pair leading to a larger section), the line speed may be reduced, since the thermal capacity of the oven may not be sufficient to maintain the same temperature level . This results in an increased temperature holding time, which is not recommended for certain qualities of steel.

With a chamber according to the invention, the strip length present in the chamber can be adjusted for each strip format so that the residence time in the chamber is that desired for all the strip formats, or the majority of them. them. Thus, it is possible to have an identical holding time, regardless of the speed of movement of the tape or the format of the tape.

In the accumulator present at the input of a continuous annealing or galvanizing line, a non-negligible length of strip is present while this is not used for the heat treatment of the strip. Advantageously, a chamber according to the invention can be placed at the input of the line, replacing the usual accumulator, to preheat the strip. Indeed, the accumulator then being sealed, under a controlled atmosphere, and being able to work at high temperature, it is possible to be able to preheat the strip in the input accumulator. This heating can in particular be achieved by convection by injecting hot atmosphere, for example heated thanks to the recovery of energy contained in the combustion fumes of burners located in the oven, or by radiation via the addition of radiant tubes.

By using the input accumulator to preheat the strip, the total length of the line is reduced.

To produce new steels with high mechanical and metallurgical properties, it may be advantageous to equip an annealing or galvanizing line with two successive annealing ovens. A chamber according to the invention can be integrated in several places on this type of line, and in particular between the two ovens. Placed between the two ovens, a chamber according to the invention can make it possible to manage transitions between the two ovens during changes in strip formats or changes in the thermal conditions of the upstream and / or downstream chamber. It allows you to control the line with greater flexibility.

Thus, the invention may consist of a continuous annealing or galvanizing line of a metal strip comprising a chamber delimited by external walls making it possible to separate the atmosphere present inside said chamber from the air located at l exterior, the exterior walls being thermally insulated to limit heat loss from the chamber, said chamber comprising means making it possible to adjust the length of strip present in the chamber.

Advantageously, the means making it possible to adjust the length of strip present in the chamber according to the invention may comprise a set of strip transport rollers whose vertical position in the chamber is adjusted by a lifting means.

According to an exemplary embodiment, the chamber according to the invention may have means allowing it to perform the function of line entry accumulator and means of heating the strip allowing the chamber to also perform the function of a preheating section.

According to another exemplary embodiment, the chamber according to the invention can be a chamber for maintaining the temperature of the strip, for example to ensure its aging, equipped with means making it possible to seal the chamber for operation under a controlled atmosphere and heating means enabling the strip to be heated or maintained at temperature.

According to another exemplary embodiment, the chamber according to the invention can be equipped with means making it possible to seal the chamber for operation in a controlled atmosphere, said chamber being able to be placed between two successive annealing ovens.

The invention also provides a system for controlling and optimizing the production of a continuous annealing or galvanizing line for metal strips comprising at least one chamber according to the invention, comprising means for adjusting the length of strip present. in a chamber according to the nature of the strip being treated and / or according to the changes in strip formats or thermal cycles during the transition phases.

A continuous line can comprise several chambers according to the invention, for example a line entry chamber, replacing the entry accumulator and the preheating chamber, an aging chamber and a transition chamber between two ovens.

The invention consists, apart from the arrangements set out above, of a certain number of other arrangements which will be more explicitly discussed below in connection with exemplary embodiments described with reference to the appended drawings, but which are not in no way limiting. In these drawings:

- Fig. 1 is a schematic longitudinal view of a continuous galvanizing line according to the state of the art,

- Fig. 2 is a schematic longitudinal view of a chamber according to an exemplary embodiment of the invention of a continuous line,

- Fig. 3 is a schematic transverse view of the chamber of FIG. 2,

- Fig. 4 is a schematic longitudinal view of a continuous galvanizing line comprising a chamber, according to an exemplary embodiment of the invention, at the line inlet, and,

- Fig. 5 is a schematic longitudinal view of a continuous galvanizing line according to another embodiment of the invention, comprising a chamber according to the invention between two annealing ovens.

Since these embodiments are in no way limitative, it will be possible in particular to produce variants of the invention comprising only a selection of characteristics described below, as described or generalized, 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 art.

Referring to the diagram of Figure 1 of the accompanying drawings, we can see schematically shown, in longitudinal view, a galvanizing line in a vertical oven according to the state of the art in which circulates a strip 1 supported by rollers 12, 13 , transport, guidance and tension. It comprises, successively and in the direction of travel of the strip 1, an inlet section 100 equipped with two reel unwinders, a shear and a welder, a line entry accumulator 101, a preheating chamber 102, a heating chamber 103, holding chamber 104, slow cooling chamber 105, rapid cooling chamber 106, aging chamber 107, oven outlet section 108, dip galvanizing section 109, tower cooling 110, a post-processing section 111, a line output accumulator 112 and a line output section 113 comprising in particular a shear and two reel winders. In this figure, the line input accumulator 101 is represented “empty”, that is to say with a minimum band capacity and the line output accumulator 112 is represented “full”, that is to say - say with maximum tape capacity.

Referring to the diagram of Figure 2 of the accompanying drawings, we can see schematically shown, in longitudinal view, a chamber 2 of a continuous line in a vertical oven, for example an aging chamber. The strip 1 enters this chamber from the left side of the figure and leaves it from the right side by passing through airlocks 6 for separating atmospheres. The strip is transported by rollers 12, 13. The position of the set of seven rollers 12 placed at the bottom of the chamber 2 is fixed relative to the chamber. The six rollers 13, placed above the set of rollers 12, move vertically in order to adjust the length of strip present in the chamber. The rollers 13 are mounted on a movable frame connected to a lifting device, not shown in this figure. Chamber 2 is maintained under a protective atmosphere composed of a mixture of nitrogen and hydrogen, for example 5% hydrogen. The atmosphere is injected into the chamber through injection points 10 and escapes from the chamber through vents 11. The walls 3 of the chamber are sealed and thermally insulated. Heating means 7, for example electric radiant tubes, make it possible to bring or maintain the strip at the desired temperature.

Depending on its format, the strip circulates more or less quickly in chamber 2. If it is an aging chamber, it is necessary that the time required to maintain the aging temperature, for example at 400 ° C., or at least equal to a minimum duration, for example 120 seconds, whatever the tape format. According to the invention, the residence time of the strip in the chamber 2 is kept constant by adjusting the position of the rollers 13 according to the format of the strip and its running speed. The rollers 13 will be placed at a level A, in the lower part of the chamber, for the minimum speed of movement of the strip, and they will be positioned at a level B, in the upper part of the chamber, for the maximum speed of movement. Between these two extreme low and high positions, the rollers 13 will take intermediate positions according to the speed of travel of the strip.

Referring to the diagram of Figure 3 of the accompanying drawings, we can see schematically shown, in transverse view, the chamber 2 shown in Figure 2. The rollers 12, whose position is fixed in the chamber 2, are rotated by motors 16. The rollers 13, whose position in the chamber is adjustable, are not motorized in this embodiment, the traction exerted by the strip sufficient to drive them in rotation. For other line configurations, in particular depending on the nature of the chamber, the formats of the strips and the maximum speed of travel of the strip, the rollers 13 will also be motorized. These rollers move vertically from a level A, in the lower part of the chamber, to a level B, in the upper part of the chamber, by means of a lifting device 18, comprising for example two electric winches not shown, placed on either side of the chamber 2. Slots in the walls of the chamber allow the passage of the shafts of the rollers 13. îo They are equipped with means not shown making it possible to limit the flow of gas between the interior of the chamber and the volume where the lifting device 18 is located, for example brushes. The lifting device is maintained under the same atmosphere as the chamber 2 by an injection of gas at the injection points 14, 15, in a volume delimited by watertight walls 17. The combination of the watertight walls 3, 17 and airlocks 6 separation of atmospheres makes it possible to maintain the chamber under a protective atmosphere, non-oxidizing for the strip.

Referring to the diagram of Figure 4 of the accompanying drawings, we can see schematically shown, a galvanizing line according to an embodiment of the invention, similar to that shown in Figure 1 but whose accumulator 101 input of line and the preheater 102 have been replaced by a chamber 2 according to the invention. It is equipped with an entry airlock 6 allowing it to be kept in an atmosphere other than the surrounding air. The outlet 19 of the chamber 2 is connected to the inlet of the heating chamber 103. The latter being, in this embodiment, maintained in the same atmosphere as the chamber 2, there is no separation device atmosphere between chambers 2 and 103. This chamber 2 performs both the functions of line entry accumulator, with a tape buffer volume, and that of chamber 102, with preheating of the tape. The strip is preheated by heating means located in the chamber, not shown in this figure, for example by convection with hot atmosphere, for example heated via energy recovery in the combustion fumes of the burners located in the heating sections, or by radiation via the addition of radiant tubes.

Referring to the diagram of Figure 5 of the accompanying drawings, we can see schematically shown, a galvanizing line according to another embodiment of the invention, comprising a chamber 2 placed between two successive ovens 103, 104, 105, 106 annealing. In this example, an airlock 6 for separating atmospheres is placed at the inlet and at the outlet of the chamber 2. These airlocks are only necessary if the atmospheres present in the chambers situated upstream or downstream of the chamber 2 have atmospheres different from that of chamber 2. Thus, if the atmospheres of chambers 2 and 103 are the same, it is not necessary to place an airlock 6 at the outlet of chamber 2.

On a line of this type with two consecutive ovens, it is particularly important to be able to modify the speed of travel of the strip before or during the transition between two coils in order to optimize the transition time and improve the productivity of the line. . Conventionally, level 2 control optimization systems in an oven control the advance speed in advance of the arrival of the new strip, or while the transition takes place in the oven. In the case of two consecutive ovens, the objectives of belt speed changes to optimize the transition may be contradictory between the first and second furnaces. At the same time, since it is possible to have several coils of steel in these two ovens, because of the total length of the line, the management of the running speed and of the traction of the strip can be particularly difficult. The establishment between the two ovens of a chamber 2 according to the invention, typically between the outlet of the cooling chamber 106 of the first oven and the inlet of the heating chamber 103 of the second oven, makes it possible to resolve this difficulty. . This chamber 2 makes it possible to completely separate the two consecutive ovens in terms of speed and traction management of the strip. The line control / command system ensures the management of the length of strip present in the chamber 2 according to the changes in strip formats, or thermal cycles, expected. Thus, a large strip length is accumulated in the chamber 2 if a lower speed is provided in the first oven than in the second during the next transition, and, conversely, a small strip length is accumulated in the chamber 2 if a higher speed is provided in the first oven than in the second during the next transition. It is thus possible to reduce or increase the running speed in the first oven without modifying the running speed in the second oven. Maintaining a stable running speed in the second oven is particularly important in the case of galvanizing lines, as a stable running speed is required, as much as possible, for the passage of the strip in the galvanizing bath which is directly at the outlet of the second oven.

In order to help manage the traction of the strip in the transient phase, a tensioning block 20 is placed between the two ovens. It works by creating a traction jump, increasing or decreasing traction, at the appropriate moment of transition passage to allow controlling the optimum level of traction when each of the two ovens passes. Advantageously, the tensioning unit also operates during the stabilized production phases to adjust the good levels of traction in the second oven relative to the first oven, which also makes it possible to use less, or even no longer use, slight variations in traction on oven deflector rollers, technically more difficult and sensitive to control.

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

Claims (15)

1. Chamber (2) arranged to receive a strip of steel running in a continuous annealing or galvanizing line, said chamber being 5 delimited by external walls (3) for separating an atmosphere (4) present inside said chamber from an atmosphere present outside said chamber, the external walls (3) being thermally insulated, said chamber comprising adjustment means (5) arranged to modify a length of strip present in the chamber. 2. Chamber according to the preceding claim, further comprising control means arranged to control the adjustment means so as to modify the length of strip present in the chamber. 15 3. Chamber according to any one of the preceding claims, the adjustment means (5) comprising a set (13) of steel strip transport rollers whose vertical position in said chamber is adjustable by a lifting means ( 18). 20 4. Chamber according to any one of the preceding claims, further comprising heating means (7) of the strip. 5. Chamber according to any one of the preceding claims, further comprising sealing means (3, 6; 17) arranged for 25 separating the interior and exterior atmospheres of said chamber. 6. Chamber according to the preceding claim, comprising means (10, 11) for controlling the interior atmosphere. 30 7. Continuous annealing or galvanizing line arranged to receive a steel strip, comprising at least one chamber according to any one of the preceding claims. 8. Line according to the preceding claim, wherein the at least one chamber is arranged at the line entry. 9. Line according to the preceding claim, and when the room is according to 5 claim 4, wherein the strip heating means are strip preheating means. 10. Line according to any one of claims 7 to 9, and when the at least one chamber is according to claims 4 and 6, wherein îo said at least one chamber is a temperature holding chamber of the strip. 11. Line according to any one of claims 7 to 10, comprising two ovens (103, 104, 105, 106), when the at least one chamber is according to the 15 claim 6, said at least one chamber being arranged so as to receive the strip downstream of the first oven and to present said strip upstream of the second oven. 12. A method comprising scrolling a strip of steel in a 20 chamber of a continuous annealing or galvanizing line, said chamber being delimited by external walls (3) for separating an atmosphere (4) present inside said chamber from an atmosphere present outside of said chamber, the outer walls (3) being thermally insulated, said chamber comprising 25 adjustment means (5) arranged to modify a length of strip present in the chamber. 13. Method according to the preceding claim, comprising a modification of the length of strip present in the chamber according to the nature of the 30 strip being processed in the line and / or according to changes in strip formats or thermal cycles during transition phases. 14. The method of claim 12 or 13, wherein the chamber performs the function of accumulator (101) of line entry and the preheating function (102) of the strip. 15. The method of claim 12 or 13, further comprising a step of heating or maintaining the temperature of the strip in the chamber and a step of controlling the atmosphere of said chamber. 16. Method according to any one of claims 12 to 14, further comprising a step of piloting the means for adjusting the chamber so as to modify the length of strip present in the chamber. 17. Computer program product, downloadable from a communication network and / or stored on a computer-readable medium and / or 15 executable by a microprocessor, and loadable in an internal memory of a calculation unit, characterized in that it includes program code instructions which, when executed by the calculation unit, implement the steps of the method according to the preceding claim. 1/5 '8 zzzzzzzj zzzzzzzzo zzzzzzzzo o ² Ύ / 2/5