Method and casting/rolling system for casting and rolling a continuous strand material

Abstract

A method for operating a casting/rolling system and to a corresponding system for casting and rolling an endless strand material. The casting/rolling system comprises a strand casting machine and a rolling train arranged downstream of the strand casting machine. The method has the following step: controlling the drive for the rollers of the first roller frame of the rolling train by means of a drive control in response to a target value specification of the pass sequence model. Furthermore, the drive of the at least one strand guiding roller is controlled by a strand guiding roller drive control in response to a target value specification of the strand casting machine drive model.

Claims

1. A method for operating a casting/rolling system for casting and rolling a continuous strand material, wherein the casting/rolling system comprises: a strand casting machine and a rolling line arranged downstream of the strand casting machine, wherein the strand casting machine is provided with a chill-mold; wherein the rolling line is provided with n roller frames, wherein n=1 through N, provided with respective drives for the roller frames, a pass sequence plan model and a drive controller for controlling the drives of the roller frames; and wherein the method comprises the following steps: controlling the drive for rollers of a first roller frame, wherein n=1, by the drive controller in response to a target value specification of the pass sequence plan model; wherein the strand casting machine is further provided with at least one strand guide arranged downstream of the chill-mold and upstream of the first roller frame with strand guide rollers and at least one drive for driving at least one of the strand guide rollers, a strand casting machine drive model and a strand guide roller drive controller, wherein control over the at least one drive of the at least one strand guide roller is performed via the strand guide roller drive controller in response to a target value specification of the strand casting machine drive model; wherein the pass sequence plan model sets as a target value specification a target rotational speed for the drive of the first roller frame, n=1, of the rolling line, the drive of the first roller frame of the rolling line being the only drive of the strand casting machine or rolling line having a set target rotational speed, and wherein the pass sequence plan model only sets as a target value specification a target torque for drives of roller frames of the rolling line only where n=2 through N, being downstream of the first roller frame; and the strand casting machine drive model sets as a target specification a target torque that is set in advance for the drive of the at least one driven strand guide roller, wherein the at least one driven strand guide roller is not provided a target rotational speed, wherein the detection of rotational speeds is omitted for the strand guide rollers and the rollers of the roller frames, wherein a thickness of the strand material at an exit of the strand guide and a casting speed are input as variables in the pass sequence model for determining a target torque Mi for drives of the rolling line where n=2 through N and the thickness of the strand material at the exit of the strand guide and the casting speed are input as variables in the strand casting machine drive model for determining a target torque Mn for the drive of the at least one driven strand guide roller.

2. The method according to claim 1, wherein the pass sequence model presets a target torque for the drive of rollers n=2 through N.

3. The method according to claim 1, wherein the pass sequence model sets an individual target torque for the drives of the rollers of the roller frames n=2 through n=k with k<N, each time a thickness of the strand material is below a predetermined thickness threshold value at an outlet of a roller frame n=k; and wherein a mass flowseen in a direction of a material flowis maintained constant after the k-th roller frame by means of a controlled or regulated loop formation of the strand material.

4. The method according to claim 3, wherein a predetermined target position is monitored in order to control the loop formation of each current position of the strand material.

5. The method according to claim 3, wherein the predetermined thickness threshold value at the outlet of the k-th roller frame is preset in dependence on an elasticity/E modulus of the strand material.

6. The method according to claim 1, wherein slippage of at least individual strand guide rollers is monitored and countered as required when there is a risk of a through-slippage of the strand guide roller at which the slippage was detected.

7. The method according to claim 1, wherein a position of a bottom tip of the strand material within the strand guide is controlled with suitable variations of control variables of a solidification model at a predetermined target position.

8. The method according to claim 7, wherein the control variables are in particular a cooling intensity of the strand material in the casting machine, a format of a cross-section, in particular thickness of the strand material in certain locations within and at an exit of the strand guide, a casting speed and a geometry of the casting machine.

9. The method according to claim 8, wherein the target rotational speed for the drive of the processing rollers of the first roller frame n=1 and the target torques for the drive of the processing rollers of the roller frames n=2 through n=N are set according to a specification of values for the thickness of the strand material at the exit of the strand casting machine and of the value for the casting speed, each time in the steady state of the casting/rolling system, and according to a specification of the measured thicknesses of the strand material at the exit of the first and of the second roller frame of the rolling line, calculated and preset by the pass sequence model.

10. The method according to claim 9, wherein the target torque for the drive of at least one driven strand guide roller is set according to a specification of the value for the thickness of the strand material at an exit of the strand guide and of a value for the casting speed, each time in the steady state of the casting roller system, as well as according to specification of a value for a strand extraction torque and profiles of a shell thickness and a temperature within and at the exit of the strand guide, calculated and preset by the strand casting machine drive model.

11. The method according to claim 1, wherein the target torques for the drives of the strand guide rollers are preset suitably distributed over a length of the strand guide by the strand casting machine drive model, while taking into account a strand casting machine geometry, a strand extraction total torque, as well as a distribution of the thickness of the strand shell and the temperature over the length of the strand guide.

12. The method according to the claim 11, wherein the target torques of the strand casting machine drive model are present in such a manner that they are increasing in a first region from a chill-mold exit until an actual position of the bottom tip of the strand material within the strand guide, and remain constant in a second region of the bottom tip until a metallurgic length of the strand casting machine.

13. The method according to claim 1, wherein a change of the value for a target rotational speed of the first roller frame and of a target value for the torques of the drives of the strand guide rollers and of the drives of the rollers of the roller frames occurs over temporal ramps.

Description

(1) A total of six figures are attached to the invention, which indicate the following:

(2) FIG. 1 a casting/rolling system according to prior art;

(3) FIG. 2 a detailed view of the casting/rolling system according to prior art of FIG. 1;

(4) FIG. 3 a schematic representation of the superordinate synchronization according to the invention of the drives of the strand casting machine and of the rolling line;

(5) FIG. 4 a solidification model for calculating the position of the bottom tip with its inlet and outlet variables;

(6) FIG. 5 the strand casting machine/drive model for calculating the torque distribution of the drive of the individual driven strand guide rollers within the strand guide with its inlet and outlet sizes, and

(7) FIG. 6 an example of mass flow regulation by means of a controlled loop formation of the strand material.

(8) The invention will next be explained in more detail with reference to FIGS. 3 through 6 in the form of embodiments thereof.

(9) FIG. 3 shows a schematic representation according to the invention of the control system of the drives and of the strand casting machine 110, as well as of the rolling line 120. The starting point of the concept according to the invention is a control circuit 130 for controlling the position of the bottom tip at a predetermined target position X_S_target within the strand guide 112. The target position X_S_target corresponds to a predetermined position of the path component x. The bottom tip regulation 130 ensures that the respective actual position of the bottom tip 160 is simulated or theoretically calculated by means of a solidification model 134, which creates the regulating distance of the bottom peak control loop 130. The position X_S_actual determined in this manner is compared to the predetermined target position X_S_target and a deviation, if it is eventually determined during the comparison, is supplied as a control variable to a controller 132 as an input variable. The controller then determines according to the value of the control deviation, as well as on the basis of a predetermined control strategy, a suitable value for certain control variables 133 that are suitable for influencing the position of the bottom tip. These control variables are in particular the intensity of the cooling of the strand material within the chill-mold and/or within the strand guide, i.e. inside the casting machine generally, the cross-sectional format, in particular the thickness h(x) of the strand material at certain locations inside and outside of the strand guide, the casting speed V_G and the geometry of the casting machine. Suitable values or modifications of the values that are determined by the controller are supplied to the solidification model as input variables 133. In the steady state of the casting/rolling system 100 and in particular of the strand casting machine 110, said control variables 133 will differ, if at all, only marginally. It is expected that the newly calculated actual position of the bottom peak 160 that is calculated from the solidification model on the basis of the supplied modified input variables is better adapted to the desired target position, see FIG. 4.

(10) Two of these control variables, in particular the thickness H0 of the strand material 200 at the exit of the strand guide 112 and the value of the casting speed V_G are respectively introduced as input variables in the steady state of the strand casting machine 110 to pass sequence model 126 for the rolling line 120 as input variables. In addition, the thicknesses H1, H2 at the exit of the first and of the second roller frame are also supplied to the pass sequence model as input variables. The thicknesses H1 and H2 can be also determined independently from the pass sequence model. This can be advantageously obtained under the criteria for the target thickness HN and for the loading limit for the roller frames. The pass sequence model 126 then calculates according to the values of said input variables first a target rotational speed N1_target for the drive 124_1 of the first roller frame n1, and the target torques Mn_target for the drive 124_n of the remaining roller frames 112 n2 through 122_N, provided that they are present in the rolling line 120. The target rotational speed n1_target calculated in this manner for the drive 124_1 of the first roller frame 122_1 is then output to the driver controller 128 of the rolling line so that they will be again controlled accordingly. It is also possible to specify the target rotational speed for the first roller frame for the driver controller 128 while taking into account a correction value d_n.

(11) The inclusion of the target torque Mn_target that is calculated from the pass sequence model 126 for the drives 124_n with 2<nN is carried out essentially via the drive controller 128. This inclusion of the torques for the drives can be essentially realized for any thin strand materials, in particular for strand materials having a thickness of >0.6 mm. This first alternative is not shown in FIG. 3.

(12) FIG. 3, on the other hand, shows a second alternative for the case when the thickness of the strand product downstream of the k-th roller frame 122_k with k1 is below a predetermined threshold value H_Lim. In this case it can be provided according to a second alternative, which is an alternative to the first alternative, that the drives 124_n with k+1<nN and with k1 for the roller framers 122_n with k+1<nN will not be impacted by the target torque predetermined by the pass sequence model in order to keep the mass flow constant also in the region of this roller frame so as to correspond to the mass flow predetermined by the first roller frame 122_1. Instead, the mass flow in the region of the following frames is maintained constant by providing looping control at least between these individual frames.

(13) An example of a per se known mass flow control circuit 140 is shown in FIG. 6, wherein the mass flow between two frames is monitored or detected by means of a mass flow monitor 142, so that consequently, a mass flow controller 144 can generate a suitable control signal for the drive controller 128, or for the drive of the loop storage device of the upstream and/or downstream connected roller frame 122_n. As can be seen also from FIG. 3, said control parameters, which is to say the thickness H0 of the strand product 200 at the exit of the strand casting machine 110, as well as the casting speed V_G in the steady state, are not supplied only to the pass sequence model 126 for the rolling line, but also to the strand casting machine/drive model 115 as input variables. In addition, the distribution of the shell thickness f(x) calculated by the solidification model is also received as long as the strand material has not completely solidified yet, which is also calculated along the path component x from the solidification model along with thickness distribution h(h) of the strand 200 along the path component x, as well as from the predetermined total torque M_G, which corresponds to the sum of all target torques of the individual drives within the strand guide. Thanks to these input parameters, the strand casting machine drive model 115 calculates the suitable target torques Mi_target for the individual drives 114_i within the strand guide 112. These target values are output via the strand guide rollers/drive controller 117 to the drive 114_i; see also FIG. 5.

(14) FIG. 5 shows said strand casting machine/drive model 115 with its input variables, which are evaluated by it in order to calculate a suitable distribution of predetermined target torques Mi_target for the individual drives 114_i within the strand guide 112 along the path component x. As can be seen from FIG. 5, the magnitude of the target torque is first increased in direction x starting from the exit from the chill-mold until a predetermined maximum value is reached at the height of the actual position of the bottom peak X_S_actual. This maximum value is then maintained for the torque of the drive within the strand guide until its metallurgic length L_G is reached.

LIST OF REFERENCE SYMBOLS

(15) 100 casting and rolling system 110 strand casting machine 111 chill-mold 112 strand guide 113_i i-th driven strand guide rollers 113a not-driven strand guide roller 114_i drive for i-th strand guide roller 115 strand casting machine drive model 117 strand guide roller drive control 118 slippage detection unit 120 rolling line 122_n n-th roller frame 124_n n-th driver for rollers of the n-th roller frame 126 pass sequence model 128 driver controller 129 inductive heating 130 bottom tip-regulation circuit 132 regulator 133 adjusting variables (=input variables of the solidification model) 134 regulation path=solidification model 140 mass flow monitor 144 mass flow regulator 160 bottom tip 170 cooling path 180 separating device 190 handling device 200 strand material d_n correction value for the target rotational speed of the first roller frame f(x) thickness of the shell of the strand material at the position x g(x) temperature of the strand material at the position x h(x) thickness of the strand material at the position x H0 thickness of the strand material at the exit from the strand casting machine H1 thickness of the strand material at the exit from the n=1 roller frame H2 thickness of the strand material at the exit from the n=2 roller frame Hk thickness of the strand material of the exit from the k-th roller frame HN thickness of the warm band when it is leaving the rolling line H_Lim predetermined threshold value for the strand material i running parameter of the strand guide rollers or number of a roller frame k parameter L number of roughing frames in the rolling line L_G metallurgic length of the strand casting machine M_G total extraction torque Mi_target target torque for the i-th strand guide target Mn-target target torque for the n-th roller frame n running parameter for roller frames or number of a roller frame N maximum number of the roller frame or the last roller frame in the rolling line nn_target target rotational speed for the n-th roller frame n1_target target rotational speed for the first roller frame V-G casting speed x path coordinate in the casting directionpath coordinate in material flow direction X_X_target target position of the bottom tip X_S_target target position for the position of the bottom tip