Abstract
Continuous annealing or galvanizing line for metal strips with at least two consecutive annealing furnaces, a tensioning unit with at least two rollers located between the two annealing furnaces, and a production control and optimization system for said line.
Claims
1. A continuous annealing or galvanizing line for metal strips arranged to handle a running strip which includes at least two consecutive annealing furnaces, and a tensioning unit comprising at least two rollers arranged between the two annealing furnaces after a cooling section of the first annealing furnace and before a heating section of the second annealing furnace, in the running direction of the strip.
2. The line according to claim 1, comprising means to control the tensioning unit to manage tension applied on the strip by said tensioning unit.
3. The line according to claim 1, where the tensioning unit is placed within an atmosphere separation buffer volume of said line, said volume placed between the upstream furnace and downstream furnace.
4. The line according to claim 1, also including an accumulator for a length of strip, said accumulator placed between the two annealing furnaces.
5. The line according to claim 4, where the accumulator is placed in a chamber with exterior walls separating the atmosphere within said chamber from the atmosphere outside, the exterior walls also being thermally insulated, said chamber also including the means to heat or maintain the temperature of the strip.
6. An annealing or galvanizing process for metal strips on a line arranged to handle a running strip which includes at least two consecutive annealing furnaces, and a tensioning unit comprising at least two rollers placed between the two furnaces, after a cooling section of the first annealing furnace and before a heating section of the second annealing furnace, in the running direction of the strip.
7. The process according to claim 6, including applying differentiated parameters to the line for the strip running speed and its tension in the two furnaces, particularly to optimize management of thermal and strip format change transitions between the two furnaces, preferably using management of the tensioning unit to control tension on the strip applied by said tensioning unit.
8. A computer program product, downloadable from a communication network and/or stored on media that can be read by a computer and/or executed by a microprocessor, and loadable to the internal memory of a calculating unit, characterized by the fact that it contains programming code instructions which, when executed by the calculating unit, initiate the stages of the process according to claim 7.
Description
[0042] The invention consists, besides the arrangements described above, of a certain number of other arrangements which will be more explicitly addressed hereafter, with reference to assembly examples described in relation to the attached drawings, but which are in no way limiting. On these drawings:
[0043] FIG. 1 is a schematic view of a continuous line with two annealing furnaces in the state of the art,
[0044] FIG. 2 is a schematic view of a continuous line with two annealing furnaces as per a first arrangement of the invention,
[0045] FIG. 3 is a schematic view of a continuous line with two annealing furnaces as per a second arrangement of the invention,
[0046] FIG. 4 is a longitudinal schematic view of an example assembly of an accumulation chamber placed between two annealing furnaces on a continuous line, and,
[0047] FIG. 5 is a transverse schematic view of the example assembly of an accumulation chamber placed between two annealing furnaces from FIG. 4.
[0048] These assembly methods being in no way limiting, there may in particular be variations of the invention that only include a selection of the characteristics described below, as described or generalized, or 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.
[0049] The diagram in FIG. 1 of the attached drawing provides a schematic representation of the processing sections of a continuous galvanizing line with two annealing furnaces 30, 40, in the state of the art. The sections of the line located up and downstream are not shown in this diagram. The strip 1, transported by rollers 2, first enters a preheating section 3, where it is for example direct-fire heated to 500 C. for example. It then moves into the heating section 4, where annealing takes place at a temperature for example of 800 C. The strip then passes into a cooling section 5 where it is cooled, for example down to 250 C. It then enters a second heating section 6 where a second annealing takes place at a temperature for example of 700 C. The strip then passes into a second cooling section 7 where it is cooled, for instance down to 460 C. It then passes through a tensioning unit 9 before entering a coating section 8 where it is dipped in a zinc bath 10. The configuration of the line is simplified here to help in the description of the invention. A real line would include a wider diversity of sections, with for example chambers for heating, soaking, slow cooling, rapid cooling, overaging, and so on.
[0050] The diagram in FIG. 2 of the attached drawings provides a schematic representation of the processing sections of a continuous galvanizing line with two annealing furnaces as per a first assembly example of the invention. This figure again shows the process sections from FIG. 1, as already described. With the aim of separating or combining the management and control of tension in the two furnaces 30,40, a two-roller tensioning unit 11 is placed after the cooling section 5 of the first furnace and before the heating section 6 of the second furnace. The tensioning unit 11 is placed in a buffer volume 12 that manages atmosphere separation between the two furnaces.
[0051] The diagram in FIG. 3 of the attached drawings provides a schematic representation of the processing sections of a continuous galvanizing line with two annealing furnaces as per a second assembly example of the invention. This figure again shows the process sections already described. A strip accumulation section 14 between the two furnaces is located downstream, in terms of the strip running direction, of the cooling section 5 and upstream of the tensioning unit placed at the entry to the heating section 6 of the second furnace. As we have seen, this line configuration enables the accumulation of a certain length of strip in the accumulation section during stable operation phases, so that strip running speed in the first furnace can be reduced without change to strip running speed in the second furnace. It therefore enables the complete separation of the two consecutive furnaces in terms of strip running speed and tension management.
[0052] The diagram in FIG. 4 of the attached drawings provides a longitudinal schematic representation of a strip accumulation section 14 between the two annealing furnaces, as per one assembly example of the invention. This section includes a chamber 15 into which a strip 1 enters from the left of the figure and exits to the right, passing through atmosphere separation seals 16. The strip is transported by rollers 17, 18. The position of the set of seven rollers 17 in the bottom of the chamber 15 is fixed within the chamber. The six rollers 18, located above the set of rollers 17, move vertically between a lower position A and a higher position B so as to adjust the length of strip present in the chamber. The rollers 18 are mounted on a mobile frame linked to an elevating device, not shown in the diagram. The chamber 15 is kept under a protective atmosphere of a mixture of nitrogen and hydrogen, for example at 5% hydrogen. The atmosphere is, for example, injected into the chamber from injection points 19 and leaves the chamber through vents 20. The walls 21 of the chamber are gas-tight and thermally insulated with refractory materials, for example ceramic fiber, to limit the chamber's thermal losses. Heating device 22, for example electric radiant tubes, can bring the strip to or hold it at the desired temperature.
[0053] The diagram in FIG. 5 of the attached drawings provides a transverse schematic representation of the chamber 15 shown in FIG. 4. The rollers 17, with their position fixed in the chamber 15, are rotated by motors 23. The rollers 18, with their position adjustable in the chamber, are not motorized in this assembly example. They are rotated by the tension applied by the strip. The rollers 18 move vertically from a level A, in the lower part of the chamber, to a level B in the upper part of the chamber, through the action of a lifting device 24, comprising for instance two electric hoists (not shown) placed on each side of the chamber 15. Slots in the chamber walls allow the movement of the shafts of the rollers 18. These are equipped with means (not shown) to limit the flow of gas between the interior of the chamber and the volume housing the lifting device 24, for example brushes. The lifting device is kept under the same atmosphere as the chamber 15 with gas injection at injection points 25 and 26, in a volume created by gas-tight walls 27. The combination of gas-tight walls 21, 27 and atmosphere separation seals 16 help maintain the chamber under a protective atmosphere that is non-oxidant for the strip.
[0054] The production control and optimization system for a continuous annealing or galvanizing line for metal strips with two annealing furnaces, as per the invention, enables differentiated control of the strip running speed and level of tension in the two furnaces, by acting on the tensioning unit 11 and, when present, the accumulation section 14.
[0055] Of course, the invention is not limited to the examples described above and numerous adjustments can be made to these examples without moving outside the frame of the invention. Moreover, the invention's various characteristics, forms, variants and assembly methods can be linked to one another in different combinations to the extent that they remain compatible and do not exclude one another.
