FI75106C - Procedure for controlling multi-station roll series. - Google Patents

Description

rm m ADVERTISEMENT 75106 B 11 UTLAGGNINGSSKRIFT '° 1 u υ (51) Kv.lk.4 / lnt.CI4 B 21 B 37/00

SUOMI FINLAND

(FI) (21) Patent application - Patentansökning 802157 (22) Application date-Ansökningsdag 04.07-80

National Board of Patents and Registration (23) Start date - Giltighetsdag 04.07.80

Patent- och registerstyrelsen (41 j TuMutjU | kjseksi_stivit offentiig 12.01.81 (44) Date of dispatch and of publication - 29.01.88

Ansökan utlagd och utl.skriften publicerad (86) Kv. application - Int. trap (32) (33) (31) Privilege claimed - Begärd priority 11.07-79 Netherlands-Nederländerna (NL) 7905404 (71) Hoogovens Ijmuiden BV, Postbus 10000, Ijmuiden, Netherlands-Nederländerna (NL) (72) Dirk Dekker, Heemskerk , Hendrik Johan Ter Maat, Castricum, Netherlands-Nederländerna (NL) (74) Berggren Oy Ab (54) Method for controlling a multi-stationed batch series

The invention relates to a method for controlling a multi-station series of rollers by means of a computer for the cold rolling of a metal strip, in which method information about each strip following each strip is entered into the computer; (a) the thickness of the tape upon arrival in the series, (b) the desired or reference thickness of the tape on departure, (c) the width of the tape, (d) the desired roughness of the top surface of the tape on departure, and (e) the resistance material specific to the tape material, the computer producing at least -meters signals to adjust the roll set of the strip in question: (f) Strip thickness between stations as it passes through the set.

(g) belt speed in series, (h) belt speed control at each rolling station, (i) belt tensile forces between rolling stations, (j) belt reel tension on the belt, (k) rolling station motor power, 75 rolling intervals in each rolling mill, (m) possibly the bending loads of the rollers, whereby the computer classifies the strip into at least one of several thickness groups depending on at least said input quantities a), b) and d), determines standard values for each group, and uses linear functions to generate correction values for standard value deviations from control parameters; is adjustable based on the corrected control parameters.

The starting factors for setting the belt speed, roll spacing, rolling deflection and other multi-station rolling mill setpoints are process variables related to strips and rolling mill series, such as inter-station strip thicknesses (gauge values), strip speed, post-casting, post-casting the tensile force applied to the strip by the placed traction coils, the rolling forces, the feed powers of the motors, the roller spacing settings and possibly the rolling bending loads.

Together, these process variables determine the roll set setting and must be calculated for this purpose.

The final regulation based on these process variables must be chosen taking into account the plant-specific factors determined by the plant structure.

The inter-station thicknesses mentioned herein refer to the thickness of the rolled material between each successive pair of rolling stations.

The process variables listed above that need to be known for series setup are calculated from the strip data for each strip, namely, arrival thickness, desired starting thickness, strip width, desired surface roughness, and strength factor specific to the strip material. As used herein, the term "thickness" has the same meaning as the "gauge value". Said strength factor is in this case a variable which describes the resistance which the material causes at the rolling stations against the deformation caused to it. Although the tensile strength of the material is usually used as a measure of this resistance, it appears that in practice a more reliable rolling batch setting can be achieved by using a strength factor determined from the chemical analysis of the material and the temperature at which the material is wound after rolling in the previous hot rolling mill.

It has been found that the large number of input data, calculation variables and setpoints required for the rolling mill series make it impossible to achieve the exact setting of the rolling mill series for virtually each strip to be rolled in the time available.

U.S. Patent 3,641,325 discloses a rolling mill computer control method using multiple sets of predetermined averages of process variables. Based on the arrival and departure data present in the tape, the most appropriate such group of averages of the process variables is selected. Linear corrections are then made to the averages of the selected group, regardless of the prevailing strip data, to achieve the final process variables used to set the rolling mill.

Said patent mainly concerns the operation of a hot rolling mill, in which rolling mill calculations are required in the rolling mill, although reference is also made to cold rolling mills.

Accordingly, it is an object of the present invention to provide a method for setting a cold rolling mill so that it is possible in practice to achieve a sufficiently accurate fit of a series of rollers in the time available. It is also intended to achieve the optimum capacity of the rolling mill within the permissible forces as well as other limiting factors.

The invention is characterized in that the following standard values for the classified thickness groups (i) strip thinning distribution between rolling mills, (ii) deformation work and force per unit width of strip width, (iii) tensile stress between rolling mills, (iv) other influencing factors , namely depending on the deviation of the actual values of the three input variables a), b) and d) of the strip in question from the corresponding predetermined standard values of the thickness group, the linear function constants being selected values derived from said strip rolling process, and the adjustment parameters are determined, and the sets of rollers are adjusted for the strip in question according to the adjustment parameter values thus determined.

75106 This invention differs from the method disclosed in U.S. Patent 3,641,325 primarily in that linear corrections are made to the standard conditions of a selected thickness group to provide applied values for those conditions, which values are then used to calculate process variables. In previous methods, corrections are made directly to process variables.

5 75106

The above "other influencing factors" can be explained as follows. For materials with different widths and thicknesses (gauge values), which can also be rolled at different speeds, the roll frame will have differences in deformation, lubricant layer thickness, etc. This affects the shapes and extent of the rolling mills at each rolling station, so that these shapes and sizes may differ from the "theoretical" values. The prevailing dimensions of the roller spacing are also affected by the wear of the rollers, bearings, etc., which gradually causes a change. All these discrepancies between the prevailing and theoretical conditions must be taken into account when determining the so-called standard values that exist for a given thickness group.

The linear functions mentioned above have "constants" which are in fact variable depending on such mixtures as the thickness distribution, the actual rolling diameter, etc.

One of these variables is the strength factor specific to the sheet material.

In addition, "thickness group" means a combination of variables which, based on the arrival thickness, the exit thickness and the desired surface roughness, comprise the following interdependent standard conditions: thinning distribution, deformation work and force, and tensile stress. These standard conditions apply to the material with which the coefficient of strength has been made and are a function of the factors acting outside the plant. They are also determined for the optimal conditions of production capacity within the limits of the money allowed to the plant. It will be appreciated that said thickness groups may be determined partly arithmetically and partly empirically for a particular plant. The larger the number of thickness groups thus determined, the closer the actual operating situation is to a known standard condition. Once the strip fed to a roll set has been classified into a thickness group, the standard conditions appropriate for that thickness group are converted to the conditions applicable to the strip before the process variables required to set the roll set can be calculated. The applied conditions derived from the standard conditions are now calculated using linear functions, which include the desired thickness ratios before and after rolling, the actual diameters of the work rolls, and the variable variables of the material used as influencing variables. Models are known in the literature and practice for the calculation of the above setting variables from the standard conditions applied. The applied process variables determined according to the new method are fed to the rolling mill control system. The control system of the rolling mill series then ensures that the set values of the rolling mill are applied according to the available data on the strip, such as arrival thickness, desired starting thickness, strip width, desired surface roughness and the strength factor specific to the strip material. The calculations are performed in such a way that, taking into account the required traction forces on the strip, there is no risk of the strip breaking. However, significantly different conditions may occur when threading a strip through a series of rollers or removing the end of the strip therefrom. Accordingly, according to the invention, it is recommended that from the threading of the strip until the tensile strength of the tension reel and / or from the end of the strip feed reel to the last rolling station at its end, the correction term is added to the calculated speed and for whenever strip material is present in the rolling station. The correction terms are determined as the quotient of the average starting thickness of the thickness group in question and the calculated actual starting thickness at each rolling station multiplied by the empirical coefficient determined for each rolling station and each thickness group. The same considerations apply as the welding spot in the strip passes through the series of rollers. In this connection, it is advantageous that from the moment the welding point is detected until it has passed through all rolling stations, for each rolling station and for all rolling stations simultaneously the correction term is added to the calculated speed of the rolling stations, which correction term is determined in the same way at the time of termination. Further development of the method is achieved by controlling the rolling mill set by means of a control computer, while the calculation of the applied variables can take place by means of a process computer. In a certain embodiment of the method according to the invention, provision is made for exceptional situations in which the process computer cannot be used. In this embodiment of the method, the rolling mill control is fed into this exceptional situation using a simplified version of a computer program, in which much fewer thickness groups are expected, classified only on the basis of desired starting thickness and strip surface roughness without correction , tensile stress and external factors. However, adaptation to the known strength factor of the material takes place. It has been stated that, although the optimum setting is not reached in this way, reliable operation can in any case be maintained for as long as the exceptional situation lasts.

With regard to the determination of the extreme setpoints of the rolling mill series, it is important that the speeds are optimized within the permissible values of engine power and speed for each rolling station. In this connection, according to the invention, it has been found useful to adjust the speeds of successive rolling stations as a function of the passage of strip thicknesses through a series of rollers, a slip coefficient which is linear. as a function of the maximum permissible values of the motor capacity and the engine speed at each rolling station are adapted to the differences in traction, adjusted to each other over successive rolling stations.

However, since the applied method is used for exceptional situations, it is recommended to adjust the speeds of successive rolling stations as a function of the passage of strip thicknesses through the rolling mill series, the constant slip coefficient, and the allowable values of motor power and speed at each rolling station. It should be noted in this connection that the passage of strip thickness through a series of rollers is determined by the thinning distribution, which in turn is determined by the choice of thickness group.

In addition to the speed control of successive rolling mills, an important control variable in the rolling mill series is the roll spacing setting at each rolling mill. The rolling spacing settings are determined according to the new method based on: the thickness of the strip leaving the rolling mill, the mechanical elongation of the strip at rolling mills 8 75106 due to rolling forces, the speeds per rolling station the uncompensated pressure of the upper rollers and possibly the bending forces of the roll. In this case, the speeds in each rolling station are adjusted according to the method described above, while the mechanical elongation due to rolling forces is a known basic value of the plant, which can be measured for several speeds of rolls without steel strip present in the plant.

Also in this case, the calculations of the rolling spacing setting for each rolling station must, of course, be performed separately if an exceptional situation occurs. In this case, the rolling spacing setting at each rolling station must be determined based on the thickness of the strip leaving this rolling station, the elongation of the strip at the rolling stations due to rolling forces and the speeds per rolling mill and strip width, in this case from standard rolling press

In this way, the control of the rolling mill set can be performed possibly on the basis of variables calculated in the process computer, which variables are functions of the data specific to the strip in question. However, a further extension of the method involves taking into account the experience gained from previous rolling mills. This can be achieved if in each strip rolling the deviations between the measured and calculated rolling forces, the motor power and the roller spacing settings are determined and the former two are applied as a corrected adjustment for deformation force and work to the for the strip to be rolled first. According to the invention, it is further recommended to use these corrections as an adjusted correction for the first roll to be rolled in the roll spacing calculation calculation based on the comparison of the calculated rolling forces and rolling interval settings and the measured values obtained when this rolling has to be performed in exceptional situations where the process computer is not available.

9 75106

A further developed form of the method further comprises determining, from a tensile force according to the coefficient of resistance, strip width and inter-station thickness, inter-station tension levels for each strip, which are corrected by rolling speeds and then fed to the inter-station tension control system. In this way, a process is obtained in which slipping in the rolling stations is more controllable and in which strip breaks are more effectively prevented.

According to another improvement of the method, starting from the standard conditions for each thickness group by making corrections for strength factor and strip width, the bending force of the roll at each rolling station is determined for each strip for varying speed values of the rolling mill. Thus, the shape of the tape can be controlled.

The invention is further described below with reference to the block diagrams shown in Figures 1 and 2.

Figure 1 illustrates a previously used method and Figure 2 illustrates an improved method according to the invention.

Figure 1 schematically shows how the control of a series of rollers can be performed in general. From the tape data, the process variables are determined through a calculation model. Process variables indicate the process under which a particular strip must be subjected to obtain the desired end product. Based on these process variables, it is determined according to the setpoints of the rolling mill which setpoints are then fed to the control device of the rolling mill. In general, the various mathematical processes required to define process variables and convert process variables to setpoints must be performed using computers. However, this is not relevant for understanding the essential content of the invention.

As mentioned above, in this way it is not possible to achieve precise adjustment of the rolling mill in practice.

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Figure 2 shows a computational model system manipulated according to the invention. Here, it is essential that the tape is first classified into a particular thickness group based on several selected tape information. In the calculation model, only a predetermined set of thickness groups are manipulated, each corresponding to only one combination of separate strip data. In practice, essentially no private strip shows that it is identical to this strip information, so that the selected thickness group is only the first approximation for the strip to be practically rolled. Standard conditions apply to each thickness group, including thinning distribution, deformation work and force, tensile stress between Vals dry stations, and factors affecting the strip from outside the plant. For a given thickness group, these standard conditions are decisive for the other process variables from which the rolling set setpoints can be derived.

However, since the standard conditions for a close thickness group do not exactly apply to the strip in question, a correction must be made to the standard conditions, and these corrections will result in the conditions applied. Since these applied conditions are predetermined, it is possible to derive the final process variables and setpoints from them.

To determine the applied conditions from the standard conditions, a correction is made based on the deviations of the strip thickness ratios before and after each rolling station, as well as the deviations of the diameter of the work rolls and the strength coefficients characteristic of these strips. The wedding deviations are used to correct the standard conditions, for which purpose the effects of these thickness ratios, roll diameters, and resistance coefficients on the linear functions are derived as a calculation process.

Since the standard conditions under the classification resulting from the classification into a particular thickness group are used primarily for the fed strip, the necessary corrections (to achieve the applied conditions) are so small that it is justified to operate with linear functions. This greatly simplifies the calculation model, allowing practical processing to be achieved in practice.

Claims (12)

A method for computer controlled control of a multi-station series of rollers for cold rolling a metal strip, the method comprising entering into the computer information about each strip from each strip; (a) the thickness of the tape upon arrival in the series, (b) the desired or reference thickness of the tape on leaving the series, (c) the width of the tape, (d) the desired roughness of the top surface of the tape on departure, and (e) an anine resistance factor for the tape material. signals for adjusting the series of rolls of the strip in question: (f) the thickness of the strip between the stations as it passes through the set, (g) the speed of the strip in the set, (h) the speed of the strip at each rolling station, (i) the tensile forces (k) the feed powers of the rolling mill motors, (l) the roll spacing adjustments at each rolling mill, and (m) possibly the rolling loads of the rolls, the computer classifying the strip depending on at least said input quantities (a), b) and d) into one of several thickness groups; using linear functions to produce a correction for deviations of standard values from control parameters to correct control parameters, the rolling mill series being adjustable based on corrected control parameters, characterized in that the following standard values for classified thickness groups are: (i) strip thinning distribution between rolling stations; (iv) other influencing factors can be converted to corrected values by linear functions, namely depending on the deviation of the actual values of the three inputs a), b) and d) for the tape in question from the corresponding predetermined standard values in the thickness group, the linear function constants being derived values depending on the rolling process of the strip and that the adjustment parameters are determined on the basis of the corrected values, and the rolling mill series is adjusted for the strip in question according to the adjustment parameter values thus determined. in accordance with. A method according to claim 1, characterized in that from the threading of the strip to provide coil traction and / or the end of alignment of the fed strip until leaving the last rolling station at the end of the strip, the correction term is added to the calculated speed and calculated interval whenever strip material is present at a rolling station, the correction terms are determined as the quotient of the average starting thickness of the thickness group in question and the calculated actual starting thickness at each rolling station multiplied by the empirical coefficient determined for each rolling station and each thickness group. Method according to Claim 1 or 2, characterized in that from the moment when the welding point in the strip is detected until it has passed through all rolling stations, for each rolling station and for all rolling stations simultaneously the correction term is added to the calculated speed of the rolling stations. is prescribed in the same way as the repair term when threading or terminating a tape. A method according to claim 1, 2 or 3, wherein the calculated applied process variables are fed to a batch control system, characterized in that in exceptional situations a simplified version of a calculation program is fed to the batch control system comprising fewer thickness groups with respect to the strength factor only. 13 751 06 Method according to Claim 1, characterized in that the speeds of successive rolling stations are adjusted as a function of the passage of strip thicknesses through the rolling mill, the slip factor due to linear dependence . Method according to Claim 4, characterized in that, for exceptional situations, the speeds of successive rolling stations are adjusted as a function of the passage of strip thicknesses through the rolling mill, the constant slip coefficient and the maximum permissible values for motor power and speed at each rolling station. A method according to claim 1 or 5, characterized in that the rolling spacing setting at each rolling station is determined based on the thickness of the strip leaving the rolling station, the mechanical elongation due to rolling force rates at each rolling station and the width of the strip. the strength factor of the strip material, the thickness ratios, the diameters of the work rolls, and the uncompensated pressure of the upper rolls, and possibly the bending forces of the rolls. Method according to Claim 4 or 6, characterized in that the roll spacing setting in each rolling station is determined for an exceptional situation based on the strip thickness on leaving the rolling station, elongation in the rolls due to rolling forces, speeds in each rolling station and strip width with respect to the bending forces of the rollers. Method according to Claim 1, 5 or 7, characterized in that, when each strip is rolled, the deviations between the measured and calculated rolling forces, the motor capacities and the roller spacing settings are determined and the former two are added to the appropriate thickness group as deformation corrections. and the latter factors are added to provide an adjusted correction thereafter to the roll spacing adjustment calculation of the strip to be rolled first. Method according to Claim 4, 6 or 8, characterized in that when rolling the strip in normal situations, the deviations between the measured rolling forces and the calculated rolling forces and the roll spacing adjustments are determined and used as applied corrections for calculating the roll spacing adjustment for the next roll to be rolled in exceptional situations. Method according to claims 1 and 4, characterized in that for each strip, starting from the tensile stress adjusted according to the strength factor, width and inter-station thickness, inter-station tensile levels are determined, which are corrected for rolling speeds and then fed to the inter-station tensile control device. 11 75106 Method according to claims 1 and 4, characterized in that for each strip, starting from the standard conditions of each thickness group and making corrections for strength factor and strip width, the rolling force of the roll for each rolling station for varying speed levels of the rolling station is determined. 15 751 06