System and method for guiding a strip traveling in a continuous line

Abstract

A system (1) for guiding a strip (2) traveling in a continuous processing line (3) for the continuous processing of the strip, comprising a plurality of guiding units (116, 131, 141, 171, 193, 202) and a plurality of detectors (114, 117, 132, 142, 151, 172, 194, 203) which detect the position of the strip and are arranged along the line, characterized in that it comprises a dynamic computer-assisted control model (300) that can take account of the position of the strip relative to the center of the line at several points along the line for the joint control of the plurality of guiding units.

Description

SYSTEM AND METHOD FOR GUIDING A STRIP MOVING IN A CONTINUOUS LINE Designation of the technical field concerned

[0001] The invention relates to continuous lines for annealing or galvanizing metal strips. It relates more particularly to guidance systems for keeping the strip in the axis of the line during its movement. Technical problems addressed by the invention

[0002] Continuous annealing or galvanizing lines for metal strips are composed in series of different sections, from an inlet section, followed by a treatment furnace composed of hot and cold sections, then an outlet section, in which a strip to be treated passes at high speeds, up to several hundred m / min, on strip drive and guide rollers.

[0003] In the furnace, the strip undergoes heat treatment which may include heating, temperature maintenance and cooling phases for the annealing and galvanizing lines, to which is added a metallic coating step for the galvanizing lines.

[0004] Galvanizing refers to all coatings, whether zinc, aluminum, zinc and aluminum alloys, or any other type of coating.

[0005] From the line's inlet to its outlet, the belt is driven on rotating rollers by a traction force. The position of the longitudinal axis of some of these rollers can move in order to exert a guiding action on the belt and prevent it from drifting from the center of the line.

[0006] Several phenomena can cause a strip to move laterally. For example, misalignment of transport rollers, a strip with surface defects created upstream of the processing line, for example during rolling, deformation of the strip in the furnace during heating or cooling, or a problem with strip traction or roller rotation, can cause strip guidance defects. This requires correction in order to limit strip offsets that could cause it to hit non-moving parts such as the furnace walls, or even cause a strip break.

[0007] The web guiding function is dedicated to guiding units installed at several points along the line. They consist of a single roller or two rollers whose axes are not fixed. The strip centering effect is achieved by a movement of the rollers around the line axis.

[0008] Depending on the type of line and its production capacity, three to seven guide units are usually installed to achieve correction and realignment of the strip path.

[0009] State-of-the-art web guidance solutions do not always provide satisfactory results, especially for high-speed lines and those equipped with rapid heating and cooling sections.

[0010] The invention provides a solution to these problems by ensuring good guidance of the strip along the entire length of the line, from the unwinders at the line entry to the rewinders at the line exit, whatever the characteristics of the line. Technical background

[0011] A web guiding unit comprises a frame consisting of a moving part on which one or two guide rollers are placed and a fixed part linked to the structure of the line, the moving part of the frame being actuated by electric or hydraulic cylinders, a web position detector and a control system which controls the position of the moving roller(s) according to the need for correction of the web position. The guiding units are for example controlled via PID type control loops.

[0012] To simplify the description, we will consider from now on that the guide units only include one roller.

[0013] The strip position detector is generally of the capacitive or inductive type and is usually arranged downstream of the guided roller, after the correction obtained by a movement of the roller.

[0014] According to the state of the art, each guidance unit operates autonomously, independently of the other guidance units present on the line.

[0015] Thus, at the unit level, the control system adjusts the positioning of the strip by modifying the position of the guide roller according to the information delivered by its position detector, without taking into account the state of the other guide units present on the line, nor other information than that delivered by the position detector. Thus, the guide unit reacts according to a localized strip deviation, without taking into account other parameters.

[0016] The position of the strip is adjusted by the guiding unit according to the information delivered by its position detector, without anticipation of the evolution of the need for centering of the strip at the entrance to the guiding unit which would result from parameters affecting the position of the strip, for example the state of the other guiding units, geometric defects of the strip or taking into account the thermal deformation of the strip.

[0017] If the belt skew detected by the position sensor is too large to be corrected by the guidance unit, an operator must intervene manually. He reduces the belt speed to facilitate recentering and limit the risk of excessive skew, which could lead to the belt colliding with a fixed part of the line or causing it to break. This reduction in running speed leads to a drop in line production.

[0018] Since the effect of a guidance unit is localized where it is positioned, it is necessary to place several guidance units along the line, resulting in a significant investment and maintenance cost for the belt guidance function.

[0019] According to a first aspect of the invention, there is proposed a system for guiding a strip moving in a continuous processing line of said strip comprising a plurality of guiding units and a plurality of detectors of the position of the strip arranged along the line, characterized in that it comprises a computer-assisted dynamic control model capable of taking into account the position of the strip relative to the center of the line at several points along the line for shared control of the plurality of guiding units.

[0020] The position of the belt at a point on the line is determined from a position detector. This position detector can be that of a guidance unit. It can also be a stand-alone detector, unconnected to a guidance unit and remote from the guidance units.

[0021] The position of the strip at a point on the line can also be determined by calculation, by extrapolation from the information provided by one or more position detectors placed upstream and / or downstream of this point.

[0022] The number of strip position detectors and their position on the line is determined according to the configuration of the line, in particular the length of the pass line between the unwinder at the line entry and the rewinder at the line exit, the length of the strip strands, the diameter of the deflector rollers, the nature of the heating and cooling sections, according to the strip formats, in particular the maximum width and the minimum thickness, the thermal cycles carried out and in particular the maximum temperatures reached and the heating and cooling speeds, and according to the maximum speed of the line and the tension of the strip in the different sections.

[0023] There may be the same number of position detectors on the line as there are guidance units, or a different number, especially a higher one.

[0024] Advantageously, position detectors are placed at strategic points along the line where significant strip decentering may occur. It can also be positioned at locations where a strip offset relative to the line axis may occur so as to anticipate this as early as possible and make corrections to prevent the decentering from becoming more severe. Knowledge of possible strip decentering at these points, and the extent of this, is useful for improving the guidance of the strip along the line. These strategic points may be different depending on the nature of the line and its characteristics. For example, they may be located at the outlet of a rapid induction heating section or at the outlet of a rapid cooling section, for example by spraying a liquid onto the strip.

[0025] Taking into account the position of the belt at several points on the line, and therefore the extent of any possible decentering of the belt at these points, allows the implementation of a global belt centering strategy. It is thus possible to make a correction at the level of a guidance unit by anticipating the impact of this correction on all the points on the line, then to verify it where a detection of the position of the belt is carried out.

[0026] Thus, advantageously according to the invention, the guide units are shared so as to control a guide unit by taking into account the correction made by other guide units arranged upstream and / or downstream in the direction of travel of the strip. This sharing makes it possible to improve overall strip centering by reducing the total correction that needs to be made.

[0027] According to an exemplary embodiment of the invention, the computer-assisted dynamic control model comprises a predictive model for anticipating a deviation of the strip along the line. The predictive model takes into account a database supplied by the history of the behavior of strips on the line, in particular according to the initial state of the strip at the entrance to the line, the operating conditions of the line, the thermal cycles carried out in the furnace and the geometric characteristics of the strip. The database is also enriched with data collected on other continuous lines and the predictive model takes into account the resulting lessons.

[0028] Based on the acquired experience available in the database, the predictive model anticipates the behavior of the strip according to its characteristics and the operating conditions of the line to improve the control of the guidance system according to the invention.

[0029] Advantageously according to the invention, the predictive model comprises artificial intelligence. This takes advantage of “deep learning” from the information present in the database of the history of the behavior of belts on the line and data collected on other lines to anticipate and predict the behavior of the belt and propose the best possible strategy for controlling the guidance system according to the invention.

[0030] The predictive model may request an off-centering of the strip at a point to anticipate, and thus avoid or mitigate, a shift that would occur downstream of this point without this off-centering.

[0031] Similarly, to prevent a guidance unit from reaching the end of its maximum correction position, the predictive model can act on the other guidance units to further share corrections with other guidance units.

[0032] The predictive model may request adjustment of belt pull per line section based on expected belt offset to improve belt alignment.

[0033] The predictive model can also request an adjustment of the tape speed based on an expected tape offset in order to improve tape alignment.

[0034] The guidance system according to the invention may comprise at least one device for measuring spatial inhomogeneities in the strip. It comprises, for example, a laser profilometer coupled to a camera. The device for measuring spatial inhomogeneities in the strip also acts as a strip position detector.

[0035] This can be placed before the strip enters the furnace so that, knowing the geometry of the strip before it enters the furnace, the model anticipates the behavior of the strip as it moves through the line.

[0036] Knowing the spatial inhomogeneities in the strip at the line entrance, it is possible to determine the mechanical and thermal deformations of the strip that will result as it passes through the different sections of the furnace, heating and cooling, by means of thermomechanical and metallurgical models. Thus, for example, if the strip has thicker edges, if it has a long center or long edges, if it has buckling or undulations, these initial characteristics, and the anticipation of their evolution along the line, are taken into account by the computer-assisted dynamic control model to predict a strip offset and optimize its centering.

[0037] Another device for measuring spatial inhomogeneities in the strip can also be placed at another location on the line, for example at the outlet of a cooling section due to the strip deformations which can occur there due to rapid cooling slopes and the difficulty of obtaining homogeneous cooling across the width of the strip.

[0038] A device for measuring spatial inhomogeneities in the strip can also be placed at the furnace outlet in order to loop back and improve the thermomechanical and metallurgical models for predicting the mechanical and thermal deformations of the strip as it passes through the furnace.

[0039] The guidance system according to the invention may comprise at least one device for measuring the temperature profile across the width of the strip. This comprises, for example, a scanner or a set of pyrometers. The device for measuring the temperature profile may also act as strip position detectors when the measured temperature profile extends beyond the width of the strip, the position of the latter being determined by a sudden variation in temperature beyond the edges of the strip.

[0040] The transverse temperature profile of the strip can modify its geometric profile, for example with long edges if they are hotter than the center of the strip. This information can be taken into account by the predictive model to improve the strip alignment.

[0041] The belt tension varies along the line, in particular due to the expansion of the belt in the heating sections and its contraction in the cooling sections. Transport rollers are, for example, equipped with strain gauges to measure the belt tension along the line. The computer-aided dynamic control model according to the invention takes into account the belt tension measurements to adjust the belt centering. The predictive model makes it possible to anticipate belt offsets that could occur due to variations in belt tension and thus improve guidance.

[0042] The number, type (single or double roller) and position of the guiding units on the line can be determined by modeling when designing a new line or during a study prior to modifying an existing line. Similarly, the number and position of the position detectors can be determined by modeling. This allows the position of the equipment to be optimized for maximum belt guidance efficiency. It also allows the number of equipment to be limited to that which is necessary in order to limit investment and operating costs.

[0043] The profiles of the transport rollers can also be determined by modeling when designing a new line or during a study prior to modifying an existing line.

[0044] Advantageously, the modeling tools can include a digital twin of the line. This makes it possible to simulate the quality of the alignment of the strip along the line, and therefore to optimize, in particular, the number, nature and location of the guidance units, position detectors, spatial inhomogeneity detectors of the strip, devices for measuring the temperature profile over the width of the strip and the profile of the rollers, according to the operating parameters of the line, the thermal cycles carried out and the strip formats.

[0045] The improvement brought by the invention to the guidance of the strip along the line can allow a single-roller guiding unit to be placed where a two-roller unit would be necessary according to the prior art. In addition to the lower cost of a single-roller unit, this above all allows for two additional strip strands to be available. This results in a shorter furnace, therefore with a smaller footprint, and a lower investment cost.

[0046] According to a second aspect of the invention, a method is proposed for controlling a system for guiding a strip moving in a continuous line, characterized in that it ensures dynamic control of a guidance system according to the invention by taking into account the position of the strip at a plurality of points along the line for controlling a guidance unit.

[0047] Advantageously according to the invention, the strip can be deliberately offset by a guide unit in order to improve the overall guidance of the strip along the line. Causing a shift of the strip can in fact prevent a more significant shift from occurring at another point along the line, without this deliberate shift.

[0048] According to an exemplary embodiment, the method according to the invention controls a guidance unit by taking into account spatial inhomogeneities in the strip. It is thus possible to anticipate and avoid strip deviations which would result from these spatial inhomogeneities.

[0049] According to an exemplary embodiment, the method according to the invention controls a guidance unit by taking into account the temperature profile over the width of the strip. It is thus possible to anticipate and avoid strip deviations which would result from a significant temperature gradient over the width of the strip.

[0050] The invention thus allows:

[0051] . To optimize the total guidance capacity of the guidance units present on the line;

[0052] . To optimize the design of the line and in particular of the oven;

[0053] . To reduce the cost, footprint and environmental impact of the line;

[0054] . To anticipate a deviation of the band;

[0055] A gain in line productivity through an increase in line speed permitted by better guidance;

[0056] A gain in productivity and line operating costs by reducing line stoppages resulting from a belt breakage following a guidance problem;

[0057] . To limit the intervention of operators for the control and maintenance of the line, hence a reduction in the risk of accidents during interventions following a belt break.

[0058] For example, the implementation of the invention on a galvanizing line with a capacity of 300,000 tonnes / year can allow an annual gain in productivity equivalent to a gain of one million euros by increasing the speed of the line and 1.7 million euros due to a limited number of days of shutdown due to strip breakage. Brief description of the figures

[0059] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which one will refer to the attached drawing in which:

[0060] is a schematic and partially represented view of a galvanizing line according to an exemplary embodiment of the invention.

[0061] Referring to the diagram of the, one can see schematically and partially represented, in longitudinal view, a vertical furnace galvanizing line 3 according to an exemplary embodiment of the invention. It comprises, successively and in the direction of travel of the strip 2, an input section comprising an unwinder 111, a welder 112, a two-roller tensioning block 113, a device 114 for measuring spatial inhomogeneities in the strip, an accumulator 115, a one-roller strip guiding unit 116, a strip position detector 117 and a second two-roller tensioning block 118, a direct-fire preheating section 120, a heating section 130 comprising a two-roller strip guiding unit 131 and a strip position detector 132, a holding section 140 comprising a one-roller strip guiding unit 141 and a strip position detector 142,a slow cooling section 150, a fast cooling section 160, an aging section 170 comprising a two-roller web guiding unit 171 and a web position detecting detector 172, an output and coating section 180 comprising a 3-roller tensioning block 181 and a dip coating tank 182, a final cooling section 190 after coating comprising a two-roller tensioning block 191, a water tank 192, a two-roller web guiding unit 193 and a web position detecting detector 194 and an output section 200 comprising an accumulator 201, a one-roller guiding unit 202, a web position detecting detector 203, a two-roller tensioning block 204, a shear 205 and a winder 206.,

[0062] In the exemplary embodiment of the, a strip position detector 132 is positioned upstream of the guide unit 131 located in the heating section 130. It is positioned on the strip strand located just upstream of the guide unit. For another line configuration or other operating characteristics thereof, it could for example be placed on a strip strand closer to the inlet of the heating section or, conversely, be placed in a strip strand located downstream of the guide unit 131.

[0063] Similarly, a web position detector 142 is positioned downstream of the guide unit 141 located in the holding section 140. It is here placed three strands downstream of the guide unit but it could be placed on another strand or upstream of the guide unit for another line configuration or other operating characteristics thereof.

[0064] Still for this exemplary embodiment of the, a strip position detector 172 is positioned downstream of the guide unit 171 located in the aging section 170. It is here placed five strands downstream of the guide unit but it could be placed on another strand or upstream of the guide unit for another line configuration or other operating characteristics thereof.

[0065] A strip position detector 194 is also positioned downstream of the guide unit 193 located in the final cooling section 190. Here it is placed just downstream of the guide unit, which corresponds to the usual position of position detectors according to the state of the art.

[0066] A guide unit 116, 202 and a strip position detector 117, 203 are also placed in each accumulator.

[0067] In this embodiment shown in, a pyrometer 151 is arranged at the outlet of the slow cooling section 150. The temperature profile over the width of the strip measured by this pyrometer can be taken into account for controlling the guidance of the strip.

[0068] The line control and monitoring system includes a computer-aided dynamic control model 300 to control the guide units according to the belt positions detected along the line by the position detectors, taking into account the line operating process information. The model 300 also takes into account transients, for example during a belt format change, to adjust the control of the guide units and maintain good belt centering.

[0069] The model 300 includes a predictive model 301 for anticipating a deviation of the belt along the line, the latter including an artificial intelligence 302.

Claims

System (1) for guiding a strip (2) moving in a line (3) for continuous processing of said strip comprising a plurality of guide units (116, 131, 141, 171, 193, 202) and a plurality of detectors (114, 117, 132, 142, 151, 172, 194, 203) of the position of the strip arranged along the line, characterized in that it comprises a computer-assisted dynamic control model (300) capable of taking into account the position of the strip relative to the center of the line at several points along the line for shared control of the plurality of guide units. System according to claim 1, characterized in that the dynamic control model (300) comprises a predictive model (301) making it possible to anticipate a deviation of the strip at a point along the line. System according to claim 2, characterized in that the predictive model (301) comprises an artificial intelligence (302). System according to claim 1, characterized in that it comprises a device (114) for measuring spatial inhomogeneities in the strip. System according to claim 1, characterized in that it comprises a device (151) for measuring the temperature profile over the width of the strip. Line (3) for continuous processing of a metal strip (2), characterized in that it comprises a system (1) for guiding the strip according to one of claims 1 to 5. Method for controlling a system (1) for guiding a strip (2) running in a continuous line (3), characterized in that it ensures dynamic control of the guidance system according to one of claims 1 to 5 by taking into account the position of the strip at a plurality of points along the line for controlling a guidance unit (116, 131, 141, 171, 193, 202). Method according to claim 7, characterized in that it controls a guidance unit (116, 131, 141, 171, 193, 202) taking into account spatial inhomogeneities in the strip. Method according to claim 7, characterized in that it controls a guidance unit (116, 131, 141, 171, 193, 202) taking into account the temperature profile over the width of the strip. Method according to claim 7, characterized in that the alignment of the strip is deliberately offset by a guide unit (116, 131, 141, 171, 193, 202) in order to improve the overall guidance of the strip along the line.

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