Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/12—Accessories for subsequent treating or working cast stock in situ
  • B22D11/124—Accessories for subsequent treating or working cast stock in situ for cooling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/16—Controlling or regulating processes or operations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/16—Controlling or regulating processes or operations
  • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/16—Controlling or regulating processes or operations
  • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
  • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling

Definitions

• the present invention relates on the one hand to a method for controlling a temperature of a strand, preferably a steel slab, by positioning a movable cooling nozzle in a strand guide of a continuous casting plant, and on the other hand, a method for controlling a
• Temperature profile of a strand preferably one
• Cooling nozzle in a strand guide of a continuous casting plant Cooling nozzle in a strand guide of a continuous casting plant.
• Cooling nozzles is that changing the operating conditions of the continuous casting plant can result in overcooling (i.e., excessive cooling) or undercooling (i.e., overheating) of the strand, particularly the strand edges, thereby significantly degrading the quality of the strand. Travelable cooling nozzles can at least partially overcome these problems.
• Movable cooling nozzles are used in continuous casting plants
• a cooling nozzle a certain value xl or x2 from the edge of the strand (see FIG. 2) as a function of the machine position, the strand age or the shell thickness of the strand (see FIG. 3) in a direction transverse to the casting direction of the strand
• Movable cooling nozzles are used in continuous casting plants
• FIG. 5 shows that cooling nozzles should not be moved by an arbitrary value x (positive values indicate a displacement of the cooling nozzle in the direction of the center of the strand), since otherwise there would be an increase in temperature in the vicinity of the edge of the strand
• the positioning of the cooling nozzles due to the shell thickness sets a
• the object of the invention is to overcome the disadvantages of the prior art and to provide a method for controlling a temperature or a temperature profile of a strand by the optimized positioning of a movable cooling nozzle, so that even with very different
• the controlled variable r is supplied to an actuator, which moves the cooling nozzle as a function of the controlled variable r, so that the control error e is minimized.
• the control error e is minimized.
• the form takes place
• Determination of the temperature value T at a strand edge of the strand since the strand edges are most sensitive to under- or over-cooling.
• the temperature control of the strand edges is particularly important for the quality of the strand.
• the controlled variable r is supplied to an actuator which moves the cooling nozzle as a function of the controlled variable r, so that the control error e is minimized.
• Temperature profile is particularly advantageous because not only a single temperature of the strand can be controlled by the positioning of a movable cooling nozzle, but it can actually be on a temperature gradient across the
• Casting of the strand are regulated out. Under a temperature profile is used in this application e.g. one
• control law can be either a linear behavior (e.g.
• Heat equation for the strand Further details of a possible process model may e.g. WO 01/91943 AI be removed.
• the state observer design allows a variety of different temperatures to be determined without even measuring one of them.
• Temperature control of the strand can be used.
• state observers are of course familiar to the person skilled in the art, see e.g. Lutz, Wendt: Taschenbuch der brungstechnik, 7.
• the determination of the temperature value T or the temperature profile is carried out by measuring at least one temperature of the strand.
• This variant may have a higher accuracy than the observation of a state observer, but this is offset by a higher cost of measuring means.
• the scalar cost function f calculates the maximum norm. This will be the maximum
• Cost function f the two-norm (also known as Euclidean norm), whereby overcooling as well as subcooling of the strand are weighted equally.
• control law has a linear control behavior, preferably that of a P, PI, PID, H 2 , H or a state controller.
• the behavior and merits of classical controllers for example, the input-output behavior as a transfer function
• control law has a non-linear control behavior, e.g. the one
• the two-position controller is special
• Coolant flow can be done to the cooling nozzle.
• Symmetry axis of the strand observed.
• the axis of symmetry extends through the width direction of the slab.
• Fig la an arrangement of two cooling nozzles at a
• Fig lb an arrangement of two cooling nozzles at a
• FIG. 7 shows a schematic representation of a first control loop for carrying out the method according to the invention.
• FIG. 1 a shows a steel slab 1 having a first width 3 which is cooled in a direction transverse to the casting direction of the slab by two movable cooling nozzles 4.
• the method of the cooling nozzles 4 takes place in a direction of travel 5.
• Each cooling nozzle has an injection pattern 6, which is a function of the pressure of the cooling fluid and the distance of the cooling nozzle 4 of the
• FIG. 1b shows a steel slab 1 which is narrower than FIG. 1a and which in turn is cooled by two cooling nozzles 4.
• the directional arrows 5 indicate the direction of travel of the cooling nozzles at a
• FIG. 2 likewise shows a steel slab 1, which is cooled by a total of three cooling nozzles 4.
• a cooling nozzle is assigned to the center and lies on the symmetry axis 2 of the slab 1.
• cooling nozzles 4 are designed as movable cooling nozzles.
• the movable in the direction of travel 5 cooling nozzle 4 has in the position shown a distance x2 to the strand edge 10.
• the distance xl indicates the distance in the horizontal direction from the outer boundary of the spray pattern 6 to the strand edge 10.
• a positive value of x1 or x2 corresponds to a displacement of the cooling nozzle in the direction of the center of the strand.
• a movable cooling nozzle 4 dynamically depending on the
• Figure 3 also shows a known dynamic employment of a movable cooling nozzle 4, wherein xl indicates a horizontal distance of the outer boundary of the spray pattern 6 of the cooling nozzle 4 to the strand shell 8 of the slab 1 and x2 a distance of the center axis of the cooling nozzle 4 to the strand shell 8 of the slab.
• xl indicates a horizontal distance of the outer boundary of the spray pattern 6 of the cooling nozzle 4 to the strand shell 8 of the slab 1 and x2 a distance of the center axis of the cooling nozzle 4 to the strand shell 8 of the slab.
• FIG. 5 shows the surface temperatures T on the
• Edge temperature leads, but from a certain distance - in this case, from about 50 mm - the temperature of the edge remains constant even with larger xl, so that by another
• FIG. 7 shows a schematic control diagram of a first control loop for carrying out the invention
• Pyrometer 11 determines and a control device 12th fed.
• FIG. 9 shows the control error e (reference symbol 14 in FIG. 7) over the distance x1.
• e «0 so that a controlled variable r « 0 is also set. Consequently
• the actuator moves in dependence on the controlled variable r with variable
• Speed i.A. it is expedient to limit the maximum travel speeds of the actuator in the positive and negative directions.
• FIG. 10 shows a second embodiment of the control loop for carrying out the method according to the invention, which works without a measurement of the temperature of the strand.
• the surface temperature of the strand edge is calculated by a so-called state observer 18, which implements the thermodynamic heat equation for the strand in a process model.
• a three-dimensional, nonlinear and transient heat equation in enthalpy formulation is solved taking into account temperature-dependent density changes; for details, reference is made to WO 2009/141205 AI.
• the strand edge is fed to the controller 12 via the state feedback.
• Figure 11 shows a local discretization of the strand 1 in the width direction, wherein the temperature profile of the
• FIG. 12 shows how the method according to the invention can also be used for the regulation of temperature profiles.
• the control loop is a temperature profile 19, eg in vector form Solll SollN supplied, whereupon the
• State variables T for the temperature of the strand result from the evaluation of a state observer 18, which contains a process model with a two-dimensional formulation of the heat conduction equation.
• Temperature deviation profile ⁇ ( ⁇ 7 [... ⁇ ) the scalar control deviation 14 is calculated by applying a scalar cost function 22 to the temperature deviation profile ⁇ , the cost function being the Euclidean norm of
• control deviation 14 is a digital controller 12, specifically a PI controller,
• the controlled variable is supplied on the one hand to an actuator of the cooling nozzle 4, which moves the cooling nozzle 4 in the width direction of the steel slab 1.
• the position 23 of the traversed cooling nozzle 4 is also fed back to the status observer 18, which underlies the temperature distribution on the strand 1
• FIG. 13 shows an alternative embodiment of FIG. 12, which does not require a status observer 18.
• the temperature profile 21 of the strand 1 is determined by the measurement of the surface temperatures of the strand, for example by a pyrometer 11, which is designed to be movable in the width direction of the strand 1.
• a pyrometer 11 which is designed to be movable in the width direction of the strand 1.
• a possible Discretization of the temperature profile 21 is shown in FIG.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
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• 2011
  • 2011-12-23 CN CN201180067033.2A patent/CN103347626B/zh active Active
  • 2011-12-23 WO PCT/EP2011/073939 patent/WO2012107143A1/de active Application Filing
  • 2011-12-23 EP EP11805854.4A patent/EP2673099B1/de active Active
  • 2011-12-23 KR KR1020137022823A patent/KR101806819B1/ko active IP Right Grant
  • 2011-12-23 DE DE112011104849.1T patent/DE112011104849B4/de active Active

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