Method for controlling a continuous line

Abstract

Method for operating a continuous line (1) for processing metal strips (2), said processing being intended to cause bands to transition from an initial state when input (3) to the line to a final state when output (5) from the line, each state being defined by a set of properties of the strip, the method comprising a determination by a calculation unit (100) of an optimal thermal cycle to which to subject a strip in order for it to reach its final state according to its initial state, the calculation unit implementing a metallurgical model (160) and an optimization model (170) for optimizing operating parameters of the line, the optimal thermal cycle defining a set of operating parameters of the line, characterized in that it comprises a step of determining tables (111, 112, 113) of alternative thermal cycles for each strip as a function of a key operating parameter of the line, the determination step being carried out before the strip is input into the line, each alternative thermal cycle defining a set of operating parameters of the line, and in that the operation of the line is switched from one optimal thermal cycle to an alternative thermal cycle, or between two alternative thermal cycles, when an event in the operation of the line makes it necessary to change the thermal cycle applied to the strip.

Description

METHOD FOR CONTROLLING A CONTINUOUS LINE Designation of the technical field concerned

[0001] The invention relates to continuous processing lines for metal strips, whether made of carbon steel, stainless steel, silicon steel or any other material. It applies to all types of line, in particular annealing lines, galvanizing lines, passivation and / or painting lines, pickling lines, decarburization lines and mixed lines, for example comprising annealing, galvanizing, pre-lacquering and / or plastic film coating.

[0002] The invention relates more specifically to methods and systems for controlling and piloting continuous metal strip processing lines. Technical problems addressed by the invention

[0003] Continuous metal strip processing lines are large installations that can include several successive heating and cooling chambers and different atmospheres. The strip circulates at high speed in the line, for example at 180 m / min for a galvanizing line and at 400 m / min for an annealing line.

[0004] The operating parameters of the line are adjusted according to the nature of the strip, including its chemical composition, previous treatments and format, as well as its initial state at the line input and the desired final state at the line output. It is also necessary to manage transition phases, for example between two strips of different composition, width or thickness, requiring changes in the operating parameters of the line.

[0005] A computer system ensures the control and management of the line in conjunction with sensors and servo-mechanisms. It may include, in particular, metallurgical, thermal, physical, statistical and optimization models of the line's operating parameters.

[0006] These models are complex. The computer system must have significant computing resources to determine the set points to be applied for each band, in steady-state production and during transitions related to band changes.

[0007] State-of-the-art line control and management systems reach their limits when an unexpected change requires the rapid determination of new line operating instructions. This is the case, for example, when an operator forces a change of an instruction or in the event of equipment failure, when this requires, for example, changing the line speed or the thermal cycle applied to the belt.

[0008] In these circumstances, control and piloting systems with metallurgical, thermal and optimization models of the line's operating parameters require new calculations to be carried out from these models to define the new instructions to be applied.

[0009] The time required to calculate these new instructions is significant. During this time, the strip moving along the line is not processed with optimal parameters, which has the effect of degrading its quality, with potential production losses. Technical background

[0010] Patent EP3652593 describes a method for controlling a continuous annealing line for steel strips. It consists of using a material property model that predicts a set of preliminary process parameters with respect to the current state of the annealing line allowing the production of the steel coil in accordance with target properties expected at the output of the continuous annealing line. These preliminary process parameters are subjected to a dynamic process model which (i) through an iterative process with the material property model allows the obtaining of parameters aiming at the convergence between the predicted properties and the target properties and (ii) determines whether the latter are capable of being achieved by the continuous annealing line before applying them for the production of said coil.

[0011] During production, if an event were to occur (for example, a manual speed change requested by the line operator, a reduction in heating capacity, etc.), some of the parameters produced would no longer be in line with the set of parameters previously calculated, leading to non-conformity of the coil properties. Thus, the material properties model would determine a set of new process parameters allowing the target properties to be obtained with regard to the parameters modified by the event, this through a new iterative process initiated by the dynamic process model.

[0012] This solution is not fully satisfactory due to the calculation and re-looping time required during the production of the steel coil in question, these processes not being instantaneous. As a result, some of the coil produced during the calculation and re-looping time interval may not comply with the target properties and may be downgraded.

[0013] The invention makes it possible to overcome these problems by allowing very rapid switching to an operating mode adapted to an unexpected change occurring on the line.

[0014] According to a first aspect of the invention, there is proposed a method for operating a continuous line for processing metal strips, said processing being intended to cause strips to pass from an initial state at the line input to a final state at the line output, each state being defined by a set of properties of the strip, the method comprising the use of a calculation unit implementing a metallurgical model and a model for optimizing operating parameters of the line to define an optimal thermal cycle to be subjected to a strip to reach its final state, the optimal thermal cycle defining a set of operating parameters of the line, characterized in that it comprises a step of determining alternative thermal cycle tables for each strip as a function of a key operating parameter of the line, the determining step being carried out before the strip enters the line,each alternating thermal cycle defining a set of operating parameters of the line, and in that the operation of the line is switched from an optimal thermal cycle to an alternating thermal cycle, or between two alternating thermal cycles, when an event in the operation of the line makes it necessary to change the thermal cycle applied to the strip.,

[0015] The event in the operation of the line is, for example, a change of an instruction by an operator or the breakdown of equipment.

[0016] The properties used to define the strip condition include mechanical, metallurgical, magnetic, geometric and surface condition properties of the strip. For the surface condition of the strip, the properties taken into account include, for example, the geometry or shape of the strip, its roughness profile, its oiling (quantity of oil and its distribution), and residual stresses.

[0017] The key operating parameter of the line is, for example, the strip speed or the annealing temperature.

[0018] By calculation unit, we mean a computer program product capable of determining a thermal cycle to be applied to the strip and the instructions to be assigned to different equipment on the line to obtain this thermal cycle.

[0019] The calculation unit is also capable of determining other operating parameters of line equipment, for example to obtain a desired coating thickness on a galvanizing line, or a decarburization rate on a silicon steel annealing and oxidation line.

[0020] A computer program means any type of computer program or calculation software, whether implemented on a desktop computer or a computer embedded in an electrical cabinet, a PLC, an electronic calculator or any other control and command system of an industrial installation. Memory means all types of "machine-readable storage medium / media". "Machine-readable storage medium / media" or "computer-readable storage medium / media" means, but is not limited to, portable or non-portable storage devices, optical storage devices and various other media capable of storing, containing or supporting instructions and / or data, and any medium that participates in the provision of instructions to a processor for their execution.A machine-readable medium may include a non-transitory medium in which data may be stored and which does not include carrier waves and / or transient electronic signals propagating wirelessly or over wired connections. Non-volatile media include, for example, optical disks, magnetic disks, or read-only memories. Volatile media include dynamic memory, including cache memory. Transmission media include coaxial cables, copper wires, and optical fibers.Common forms of computer-readable media include, for example, but are not limited to, a floppy disk, a floppy disk, a hard disk, a magnetic tape, any other magnetic media, a CD-ROM, a DVD, any other optical media, punched cards, other physical media with patterns of holes, RAM, PROM and EPROM, FLASH-EPROM, any other memory chip or cartridge, a carrier wave, or any other medium from which a computer can read. Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution.

[0021] A computer program product may include machine-executable code and / or instructions that may represent a procedure, function, subroutine, program, routine, subprogram, module, software, class, or any combination of instructions, data structures, or program instructions. A code segment may be coupled to another code segment or hardware circuit by transmitting and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc., may be transmitted, passed, or conveyed by any suitable means, including memory sharing, message passing, token passing, network transmission, etc.

[0022] The initial state of the strip at the line entrance is taken into account for the determination by the calculation unit of the thermal cycle to be applied to it to reach the target state aimed for at the line exit.

[0023] To establish this initial state, we can consider in particular the chemical composition of the strip, the thermomechanical and metallurgical transformations undergone by the strip during the production stages carried out upstream of the line such as continuous casting, hot rolling, pickling, cold rolling, its mechanical properties such as tensile strength or elastic limit, its surface condition, etc.

[0024] Since the line may include induction heating equipment, whether longitudinal flow and / or transverse flow, one can also consider, for example, the electrical resistivity or more generally the magnetic properties of the strip at the line entrance.

[0025] The final state of the strip expected at the exit of the line may also be characterized by these same criteria and / or other criteria, for example the coating thickness for galvanizing lines or the quantity of oxides present on the surface of the strip.

[0026] From this input and output data, the calculation unit determines an optimal thermal cycle to obtain a strip with all the desired characteristics at the line output.

[0027] A metallurgical model according to the invention has the function of determining the thermal cycle to be applied to the strip as a function of its composition, its initial state at the inlet of the line and the final state of the strip expected at the outlet of the line. It is based in particular on equations translating the kinetics of recrystallization, phase transformations or grain growth. Thus, for example, the rate of rise to temperature, the temperature reached, the duration of maintenance at this temperature, then the cooling rate of the strip are determined using the metallurgical model.

[0028] A thermal model according to the invention has the function of determining the heat exchanges between the strip and the line. Thus, for example, it makes it possible to determine the heating or cooling power required along the line to apply the desired thermal cycle to the strip. It is based in particular on equations for heat transfer by radiation, convection and conduction.

[0029] A model for optimizing operating parameters of the line according to the invention has the function, in particular, of defining the optimum improvement parameters, for example making it possible to reduce the energy consumption of the line, to increase the productivity of the line, or to best reproduce the desired final state. The model compares, for example, several thermal cycles determined with the metallurgical model and the thermal model to retain the best according to a criterion or a weighting of criteria.

[0030] If the equipment present on the line does not allow a thermal cycle to be carried out which will produce a strip with all the desired characteristics at the line outlet, the optimal thermal cycle will be the one which will come as close as possible.

[0031] The optimal thermal cycle may not be able to be achieved for several reasons, for example after an unexpected change resulting from equipment failure or a change of setpoint by an operator.

[0032] If some desired characteristics can be achieved and others cannot, a weighting grid for these characteristics can be established so that the computing unit determines an optimal cycle taking into account this weighting grid, the characteristics to be achieved as a priority being those whose relative weight is the greatest. The optimal cycle can also be established with a complex mathematical function linking all or part of the parameters to be optimized.

[0033] For the optimal thermal cycle calculated by the calculation unit, it determines a set of operating parameters for the line, such as the running speed of the belt, the set temperatures and the heating powers of the heating zones, the adjustment of frequency converters on electric motors, in particular those of the fans located in the cooling sections, etc.

[0034] According to the invention, the calculation unit also calculates a set of alternative thermal cycles intended to replace the optimal thermal cycle when the latter cannot be carried out. It also determines all the operating parameters of the line for each of these cycles.

[0035] The invention thus makes it possible to have alternative thermal cycles ready to constitute fallback solutions when an event in the operation of the line makes it necessary to change the thermal cycle applied to the strip.

[0036] This avoids the need for the calculation unit to calculate a new optimal thermal cycle, by using its metallurgical, thermal and line operating parameter optimization models, while the strip is moving through the furnace under unsuitable conditions.

[0037] The determination of the alternative thermal cycles is carried out before the strip enters the line so that they are available when the unexpected change occurs. The method according to the invention is thus predictive in that it makes it possible to anticipate the changes to be made to the operating parameters of the line.

[0038] Thus, when an event in the line operation makes it necessary to change the thermal cycle applied to the strip, the line operation is quickly switched from an optimal thermal cycle to an alternative thermal cycle, or between two alternative thermal cycles if the line was already operating on an alternative thermal cycle.

[0039] Alternating thermal cycles are calculated based on a key line operating parameter, such as strip speed or annealing temperature, or other parameters that operators may force during line operation.

[0040] According to the invention, all of the operating parameters of the line, for each of these alternative thermal cycles, are formatted into one or more data tables.

[0041] For example, for a table, each row corresponds to an alternating cycle and each column corresponds to an operating parameter of the row. For example, the first column contains the key parameter from which the alternating thermal cycles in the data table were calculated, such as the strip speed or the annealing temperature.

[0042] Multiple tables can be calculated and made available, each based on a different key parameter. Thus, depending on the nature of the unexpected event that necessitates the change in thermal cycle, the system chooses the table whose key element is most relevant.

[0043] For example, the key event in a first table may be the line speed, which appears in the first column of the table. When the unexpected event is a change in the line speed setpoint by an operator, the system takes directly from this table all the parameters found in the table in the row where the new speed setpoint is found, or the row whose speed is closest to the new setpoint.

[0044] Advantageously according to the invention, the choice of the alternating cycle is made according to the nature of the event in the operation of the line and the importance of the deviation that it causes on the key operating parameter(s) of the line.

[0045] The event in the operation of the line which makes necessary a change in the thermal cycle applied to the strip is undergone or chosen.

[0046] It is experienced, for example, when it follows a failure of line equipment. It is chosen, for example, during a band change. The invention thus makes it possible to respond to all scenarios.

[0047] Advantageously according to the invention, the management of transient regimes during changes in formats or strip quality can be carried out using alternative thermal cycles previously calculated and available in tables.

[0048] To move from band A to band B, the line control system can thus use a succession of previously calculated alternating cycles.

[0049] The choice of alternative cycles can advantageously take into account information received from different sensors during the transition phase.

[0050] Switching from one thermal cycle line operation to another can be done without requiring recalculation of the computing unit.

[0051] Alternate thermal cycles can be defined so that the final state of the strip is as expected with the optimal cycle or as close to it as possible.

[0052] Advantageously according to the invention, the optimal thermal cycle and the alternative thermal cycles are defined to optimize a quality index. This is defined by one or more criteria such as the productivity of the line, the energy consumption of the line, the level of polluting emissions of the line, or the water consumption of the line.

[0053] A continuous line for processing metal strips is proposed comprising a control and command system capable of implementing a method according to the invention.

[0054] According to a second aspect of the invention, a computer program product is proposed comprising instructions which, when loaded into a memory of a desktop computer or a computer embedded in an electrical cabinet, an automaton, an electronic calculator or any other control and command system of an industrial installation, lead a control and command system of a line according to the invention to execute the steps of a method according to the invention. Brief description of the figures

[0055] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0056] is a schematic and partially illustrated view of a continuous line for processing metal strips,

[0057] is a schematic and partially represented view of a first part of a control and command system of a line according to an exemplary embodiment of the invention, and,

[0058] is a schematic and partially represented view of a second part of the control and command system of the.

[0059] As shown in, a continuous line 1 for processing metal strips 2 comprises an input section 3, a processing section 4, an output section 5 and a control and command system 10. In the processing section 4, the strip can pass through heating, holding, cooling and coating chambers intended to modify its mechanical properties and its surface condition.

[0060] As shown in, a system 10 for monitoring and controlling a continuous line according to an exemplary embodiment of the invention comprises a calculation unit 100 intended to calculate thermal cycles adapted to the strips to be treated in the line.

[0061] For a strip, as input data, the calculation unit uses information 101 relating to the state of the strip at the line input, information 102 relating to the state of the strip targeted at the line output and information 103 relating to the characteristics of the line. Among this information, some can be acquired or measured via sensors present on the line. The calculation unit notably implements a metallurgical model 160 and an optimization model 170.

[0062] The information 101 relating to the state of the strip at the line input is, for example, its chemical composition, its mechanical or magnetic properties, its metallurgical structure, its geometric characteristics, its electrical resistivity and its surface state. They result from the stages of preparation and treatment of the strip upstream of the continuous line.

[0063] The information 102 relating to the state of the strip targeted at the line exit is, for example, its optimal and tolerated mechanical properties, its metallurgical structure, its surface condition, or the coating thickness. They are linked to the operations carried out during the passage of the strip through the line.

[0064] Information 103 relating to the characteristics of the line are, for example, the heating capacity and the maximum temperature of the heating chambers, the cooling power of the cooling sections, the nature of the atmosphere in the different chambers of the line, the maximum pressure available to the dewatering machine of the coating section, or the maximum speed of the line.

[0065] The data 103 may correspond to the nominal characteristics of the line or they may be a function of the actual state of the line, in particular if certain equipment is operating in degraded mode. For example, if a burner is faulty on a heating section, the maximum heating capacity of said chamber considered by the calculation unit will be lower than its nominal capacity of the power of said faulty burner.

[0066] As output data, the calculation unit delivers an optimal thermal cycle, and the operating parameters 110 of the line associated with it, making it possible to obtain the desired characteristics of the strip at the line output, or the characteristics closest to these if it is not possible to obtain the desired characteristics.

[0067] It also provides a set of tables 111, 112, 113, each table comprising a series of alternative thermal cycles according to the evolution of a key parameter, and the line operating parameters associated with them.

[0068] In this exemplary embodiment of the invention, table 111 comprises a series of alternating thermal cycles depending on the line speed, table 112 comprises a series of alternating thermal cycles depending on the maximum annealing temperature and table 113 comprises a series of alternating thermal cycles depending on the hydrogen content in a rapid cooling chamber under an N2-H2 gas mixture.

[0069] For each strip to be processed, the line control and command system 10 stores the optimal thermal cycle and the alternative thermal cycles, as well as the line operating parameters associated with them, in a database, RAM or any other computer solution allowing these cycles to be stored.

[0070] The line control and command system 10 includes a production planning program for defining the order in which the strips pass through the line, according to the characteristics of the strips and the optimal thermal cycles associated with them, so as to limit changes in line instructions between two strip changes.

[0071] The calculation of the optimal and alternative thermal cycles, as well as the choice of the order of passage of the strips, are carried out upstream, before the strips enter the line.

[0072] Alternatively, all or part of the calculation of the thermal cycles, the determination of the operating parameters of the line associated with them, the creation of the data tables and the planning of the order of passage of the strips, is carried out on a computer system other than the control and command system 10 of the line. The results obtained are transmitted to the control and command system 10 of the line to ensure the processing of the strips.

[0073] We can see represented in a second part of the system 10 of control and command of the line of the.

[0074] This also includes a computer program 200, commonly referred to as "Level 2." Level 2 refers to the software layer just above Level 1. The latter is associated with real-time control of equipment such as sensors, actuators, and programmable logic controllers.

[0075] Level 2 is responsible for coordinating and supervising continuous line production processes. This may include production monitoring software, quality management systems, production planning programs, and inventory management software.

[0076] It is located between level 1 and level 3 which manages production planning, human resources and financial aspects of the factory.

[0077] For each strip, before processing it, level 2 receives as input data the optimal thermal cycle, and the operating parameters 110 of the line associated with it, as well as the tables 111, 112, 113 comprising the series of alternative thermal cycles and the operating parameters of the line associated with them. It also receives a set 105 of other information such as the parameters of the galvanizing bath, the wringing system, the painting line, the skin-pass mill.

[0078] Level 2 checks whether the optimal thermal cycle can be achieved and, if necessary, when the time comes, transmits the instructions corresponding to the operating parameters of the line to the various actuators 150 present on it.

[0079] If level 2 determines that the optimal thermal cycle cannot be achieved because a key operating parameter of the line cannot be obtained, i.e. it will not be within the tolerances defined by the information 102 relating to the state of the strip targeted at the line outlet, level 2 chosen from the table corresponding to this key parameter is the first alternative cycle. If this cannot be achieved either, level 2 chooses the next one. The operation is repeated until an alternative cycle can be achieved. Level 2 then transmits the instructions corresponding to the operating parameters of the line for this alternative cycle to the various actuators 150.

[0080] Two successive bands may require significant changes in setpoints. A transition phase allows one or more parameters to be varied from the value corresponding to the first reel to that required for the second. Level 2 controls this transition.

[0081] For example, the annealing of a first coil is carried out at a lower temperature than that of the second coil. During the transition phase, level 2 will define or receive a first setpoint 131 corresponding to a first intermediate annealing temperature, then a second higher intermediate setpoint 132 before applying the setpoint corresponding to the annealing temperature of the second coil.

[0082] Advantageously according to the invention, level 2 uses alternating thermal cycles for each of the intermediate annealing temperatures to ensure the transition between these two bands.

[0083] Level 2 can receive a command 103 from an operator to change an instruction, for example the speed of the tape.

[0084] In this case, level 2 will search for the line corresponding to the new speed setpoint in table 111 whose key parameter is the speed, or the line corresponding to the speed of the table closest to the new setpoint, and apply the corresponding alternative thermal cycle.

[0085] Another example, if level 2 receives a command 104 from an operator changing the maximum annealing temperature setpoint, it will search for the corresponding alternative cycle in table 112 whose key parameter is the maximum annealing temperature.

[0086] Level 2 can receive information 121,122,123 when an unexpected event occurs. For example, when a row of burners in a heating chamber has just failed.

[0087] Level 2 determines a new maximum annealing temperature that can be achieved without this row of burners and it looks up the corresponding alternative cycle in table 112 whose key parameter is the maximum annealing temperature.

Claims

Method for operating a continuous line (1) for processing metal strips (2), said processing being intended to pass strips from an initial state at the line input (3) to a final state at the line output (5), each state being defined by a set of properties of the strip, the method comprising a determination by a calculation unit (100) of an optimal thermal cycle to be subjected to a strip to reach its final state according to its initial state, the calculation unit implementing a metallurgical model (160) and an optimization model (170) of operating parameters of the line, the optimal thermal cycle defining a set of operating parameters of the line, characterized in that it comprises a step of determining tables (111, 112, 113) of alternative thermal cycles for each strip as a function of a key operating parameter of the line, the determination step being carried out before the strip enters the line,each alternating thermal cycle defining a set of operating parameters of the line, and in that the operation of the line is switched from an optimal thermal cycle to an alternating thermal cycle, or between two alternating thermal cycles, when an event in the operation of the line makes it necessary to change the thermal cycle applied to the strip., Method according to claim 1, characterized in that the choice of the alternating cycle is made according to the nature of the event in the operation of the line and the importance of the deviation that it causes on the key operating parameter of the line. Method according to claim 1, characterized in that the event in the operation of the line is undergone or chosen. Method according to claim 1, characterized in that the alternative thermal cycles are defined so that the final state of the strip is as expected with the optimal cycle. Method according to claim 1, characterized in that the optimal thermal cycle and the alternative thermal cycles are defined to optimize a quality index. Continuous line (1) for processing metal strips comprising a control and command system (10) capable of implementing a method according to one of the preceding claims. Computer program product comprising instructions which, when loaded into a memory of a desktop computer or a computer embedded in an electrical cabinet, an automaton, an electronic calculator or any other control and command system of an industrial installation, lead a system (10) for control and command of a line (1) according to claim 6 to execute the steps of a method according to one of claims 1 to 5.

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