JP5565214B2 - Thickness control method of rolling mill - Google Patents

Description

  The present invention relates to a sheet thickness control method for a rolling mill suitable for application to a steel rolling process or the like.

In order to obtain the target thickness after rolling in steel plate rolling, it is necessary to accurately estimate the roll gap before rolling. When determining this roll gap, the gauge meter type generally expressed by the following formula (1) is used.
H = S + F / M + K ……… (1)
Here, H: gauge meter thickness (estimated plate thickness), S: roll gap before rolling, F: rolling load, M: mill constant, and K: roll gap offset amount. The mill constant M represents the rigidity of the rolling mill (mill), and F / M obtained by dividing the rolling load F by the mill constant M is the mill elongation due to the rolling load F. The roll gap offset amount is an error due to heat, wear, or the like. In order to bring the thickness after rolling closer to the target thickness, it is necessary to accurately grasp the mill constant M and the roll gap offset amount K.

  The mill constant M can be grasped by kiss-rolling the work roll of the rolling mill and measuring a stretch curve indicating the relationship between the roll gap and the rolling load. In actual rolling, rolling conditions (rolling load, sheet width) Since the mill constant M varies depending on the sheet crown, work roll diameter, work roll crown, etc., the mill constant M is calculated based on the rolling conditions at that time.

  Since the mill constant M fluctuates due to various factors and becomes a disturbance of the sheet thickness accuracy, the sheet thickness is actually measured between passes of the same rolled material and between the rolled materials at the end of rolling. An attempt has been made to improve the thickness accuracy by correcting the gauge meter type with the difference from the gauge meter thickness H as an offset amount. However, in this method, since the rolling conditions are different between when the offset amount is acquired and when rolling, the calculation accuracy of the mill constant M is not sufficiently improved.

  On the other hand, in the following Patent Document 1, while measuring a plurality of rolling load Fi and rolling roll gap Si during rolling in the length direction of the rolled material, the thickness at the same plurality of points is measured by a thickness gauge after rolling. A method of measuring hi and calculating a mill constant M and a roll gap offset amount K from the measured rolling load Fi, roll gap Si, and plate thickness hi is described. In Patent Document 2 below, as in Patent Document 1, the rolling load Fi, the roll gap Si, and the plate thickness hi are measured at a plurality of points in the longitudinal direction of the rolled material, and the mill constant M and the roll are measured based on them. The gap offset amount K is calculated, and the mill constant M and the roll gap offset amount K are corrected in consideration of the difference between the rolling conditions at the time of measurement and the rolling conditions of the next rolled material, and the corrected mill constant M and the roll gap offset are corrected. It is described that the plate thickness accuracy is improved by applying the amount K to the plate thickness control during the next rolling.

Japanese Patent No. 2538942 JP-A-8-155515

However, an error depending on the rolling load remains in the difference between the gauge roll thickness H and the plate thickness actual measurement value, and even with the method described in the above-mentioned patent document, this error is corrected and high-precision plate thickness control is performed. There is a problem that can not be done.
The present invention has been made paying attention to the above problems, and provides a sheet thickness control method of a rolling mill that enables highly accurate sheet thickness control by estimating an error depending on a rolling load. It is for the purpose.

  In order to solve the above problems, the sheet thickness control method of the rolling mill of the present invention is a sheet thickness control method of a rolling mill that performs sheet thickness control using a gauge meter type, and is actually measured on the last path exit side of the rolled material. Last path thickness error between the measured plate thickness and the estimated thickness after the last pass calculated from the gauge meter formula, and the halfway calculated from the measured thickness and gauge meter formula measured on the exit side of the path before the last pass. Calculate the intermediate pass plate thickness error from the post-pass estimated plate thickness, and calculate the mill from the last pass plate thickness error and the plate thickness error difference value of the intermediate pass plate thickness error and the rolling load difference value of the last pass and the rolling load of the intermediate pass. The calculation error of the elongation amount is estimated, and the gauge meter equation is corrected using the calculation error, and is applied at the next and subsequent rolling.

  Further, the difference between the thickness error difference value and the rolling load difference value for a plurality of rolled materials, and calculating a correction coefficient for the calculation error of the mill elongation amount from the plurality of thickness error difference values and the rolling load difference value, The gauge meter type is corrected from the correction coefficient of the calculation error of the mill elongation amount and the rolling load after the next time, and is applied at the next and subsequent rolling.

  Thus, according to the sheet thickness control method of the rolling mill of the present invention, when performing the sheet thickness control using the gauge meter formula, it is calculated from the actually measured sheet thickness and gauge meter formula measured on the last path exit side of the rolled material. The plate thickness error between the estimated plate thickness after the last pass and the measured plate thickness measured on the exit side of the intermediate pass before the last pass and the estimated plate thickness after the intermediate pass calculated from the gauge meter equation The error is calculated, and the calculation error of the mill elongation amount is estimated from the plate thickness error difference value of the last pass plate thickness error and the intermediate pass plate thickness error and the rolling load difference value of the rolling load of the last pass and the intermediate pass, and the calculation error is calculated. Since the gauge meter formula is modified and applied at the next and subsequent rolling, it is possible to estimate the calculation error of the mill elongation amount depending on the rolling load and to control the plate thickness with high accuracy.

  Further, a thickness error difference value and a rolling load difference value are obtained for a plurality of rolled materials, and a correction coefficient for a calculation error of the mill elongation amount is calculated from the plurality of thickness error difference values and the rolling load difference value. The gauge meter formula was corrected from the correction coefficient for calculation error of mill elongation and the rolling load after the next time, and it was decided to apply it at the next and subsequent rolling. More accurate plate thickness control can be performed by accurately estimating the calculation error.

It is a schematic block diagram which shows one Embodiment of the rolling equipment to which the plate | board thickness control method of the rolling mill of this invention is applied. It is explanatory drawing of the calculation error of the mill elongation amount according to a rolling load. It is explanatory drawing which calculates a correction coefficient from the calculation error of mill elongation. It is explanatory drawing of the Example of the gauge meter thickness error which corrected the gauge meter type | mold using the calculation error of mill elongation, and a prior art example.

Next, an embodiment of a sheet thickness control method for a rolling mill according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a rolling equipment to which a thickness control method for a rolling mill according to this embodiment is applied. The rolling equipment includes a reversible rolling mill 1 that can repeatedly roll a rolled material 10. The reversible rolling mill 1 includes upper and lower work rolls 2 and upper and lower backup rolls 3. The amount of opening between the upper and lower work rolls 2 can be adjusted by the opening changing mechanism 4, and the amount of opening between the work rolls 2 is adjusted by the opening changing mechanism 4, so that the amount of reduction, that is, a predetermined reduction rate is set. can do. The opening changing mechanism 4 changes the setting of the opening in each pass according to an opening command from the controller 5. The rolling load at the time of rolling is detected by the load cell 6, and the detected value is output to the controller 5.

In the example of the rolling equipment of the present embodiment, the rolled material 10 is conveyed from the left side of the figure, and is rolled by the reversible rolling mill 1 from the left side to the right side of the figure and from the right side to the left side for a determined number of passes. Processing is performed. When the rolling with the target plate thickness is completed, the rolled material 10 after rolling is conveyed to a post process (not shown) provided on the right side of the drawing.
On the exit side of the first pass of the reversible rolling mill 1 (on the right side in FIG. 1), a thickness gauge 7 for measuring the thickness of the rolled material 10 is provided, and the rolling measured by the thickness gauge 7 is performed. The thickness of the material 10 is read by the controller 5, the calculation error of the mill elongation is estimated as will be described later, a correction coefficient is calculated from the calculation error, and the gauge is calculated from the rolling load and correction coefficient at the next and subsequent rolling. The meter type is corrected, and the thickness control is performed at the next and subsequent rolling using the corrected gauge meter type. In order to calculate the correction coefficient from the calculation error of the mill elongation amount, it is necessary to measure the plate thickness on the exit side of the last pass and the exit side of the intermediate pass for a plurality of rolled materials. The thickness gauge 7 can be installed not only on the exit side of the first pass of the reversible rolling mill 1 (right side of FIG. 1) but also on the entrance side of the first pass (left side of FIG. 1). Thereby, it is possible to actually measure the plate thickness on the exit side of the rolling pass from the right side to the left side in FIG.

  The relationship between the measured plate thickness on the exit side of the intermediate pass, the estimated plate thickness after the intermediate pass (gauge meter thickness), the measured plate thickness on the exit side of the final pass, the estimated thickness after the last pass (gauge meter thickness), and the rolling load It appears as shown in FIG. The rolling load of the last path is small, and errors due to heat, wear, etc. (corresponding to the roll gap offset amount) are considered to be the same or almost the same even if the path is different. If the last pass plate thickness error is subtracted from the intermediate pass thickness error between the measured and estimated plate thicknesses of the intermediate pass, the calculation error of the mill elongation due to the rolling load in the intermediate pass (mill elongation error in the figure) is obtained. It is done.

  When a plurality of calculation errors of the mill elongation due to this rolling load are obtained from a plurality of rolled materials and plotted according to the rolling load difference between the rolling load of the last pass and the rolling load of the intermediate pass, as shown in FIG. A correlation of calculation error (mill elongation error in the figure) of the mill elongation amount depending on the difference is obtained. Since this correlation has a linear characteristic, for example, if the slope α is obtained by the least square method or the like, a calculation error of the mill elongation per unit rolling load can be obtained. The calculation error α of the mill elongation amount per unit load is set as a correction coefficient α of the calculation error of the mill elongation amount. The correction coefficient α for the calculation error of the mill elongation amount is considered to be substantially constant for each rolling line in operation.

As described above, the amount of mill elongation should be woven into the gauge meter thickness H by F / M in the gauge meter type. However, in an actual operation, a calculation error that does not appear in the stretch curve due to the kiss roll described above occurs. The calculation error of the mill elongation amount can be corrected by multiplying the correction coefficient α by the rolling load F at the next and subsequent rolling, thereby correcting the estimated plate thickness at the next and subsequent rolling, that is, the gauge meter thickness H. Therefore, the estimated plate thickness, that is, the gauge meter thickness H, corrected by adding the product value of the correction coefficient α and the rolling load F to the gauge meter equation, is obtained. That is, the corrected gauge meter thickness H is expressed by the following two formulas. If the roll gap S of each pass is set so that the corrected gauge meter thickness H becomes the target value of the exit side plate thickness of each pass, the measured plate thickness can be brought close to the estimated plate thickness. It can be said that the correction coefficient α corrects the mill constant M because the term of the rolling load F in the following equation (2) is F ((1 / M) + α).
H = S + F / M + K + αF (2)

  FIG. 4 shows an error of the gauge meter thickness in the embodiment in which the calculation error of the mill elongation amount is corrected and an error in the gauge meter thickness in the conventional example without correction. The plot shows, for example, rolling load categories of rolling load of 4000T or less, 4000T or more, 5000T or less, 5000T or more, 6000T or less, or 6000T or more. As is apparent from the figure, the example in which the calculation error of the mill elongation amount is corrected has a smaller gauge meter thickness error than the conventional example in which correction is not performed. In particular, an error in gauge meter thickness in a high rolling load section can be suppressed. This means that the gauge meter thickness can be effectively corrected in a region where the rolling load is large because the calculation error of the mill elongation described above depends on the rolling load.

  As described above, in the sheet thickness control method of the rolling mill according to the present embodiment, when performing the sheet thickness control using the gauge meter formula, the thickness was calculated from the actually measured sheet thickness and the gauge meter formula measured on the last path exit side of the rolled material. The plate thickness error between the estimated plate thickness after the last pass and the plate thickness error between the measured plate thickness measured on the exit side of the intermediate pass before the last pass and the estimated plate thickness after the intermediate pass calculated from the gauge meter equation. The calculation error of the mill elongation amount is estimated from the plate thickness error difference value of the last pass plate thickness error and the intermediate pass plate thickness error and the rolling load difference value of the rolling load of the last pass and the intermediate pass, and the calculation error is used. By correcting the gauge meter formula and applying it at the next and subsequent rolling, it is possible to estimate the calculation error of the mill elongation amount depending on the rolling load and to perform highly accurate sheet thickness control.

  Further, a thickness error difference value and a rolling load difference value are obtained for a plurality of rolled materials, and a correction coefficient for a calculation error of the mill elongation amount is calculated from the plurality of thickness error difference values and the rolling load difference value. Calculation of mill elongation depending on rolling load at the next and subsequent rollings by correcting the gauge meter formula from the correction coefficient for calculation error of mill elongation and the rolling load at and after the next and applying it at the next and subsequent rolling It is possible to accurately estimate the error and perform more accurate plate thickness control.

  1 is a reversible rolling mill, 2 is a work roll, 3 is a backup roll, 4 is an opening changing mechanism, 5 is a controller, 6 is a load cell, 7 is a thickness gauge, and 10 is a rolled material.

Claims (1)

A sheet thickness control method for a rolling mill that performs sheet thickness control using a gauge meter expression represented by the following two formulas, and for a plurality of rolled materials, measured sheet thicknesses and gauges measured on the last path exit side of the rolled material Last path thickness error with the estimated thickness after the last pass calculated from the meter formula, the measured thickness measured on the exit side before the last pass and the estimated thickness after the mid-pass calculated from the gauge meter formula An intermediate pass plate thickness error is calculated, and a plate thickness error difference value of the last pass plate thickness error and the intermediate pass plate thickness error and a rolling load differential value of the last pass and the rolling load of the intermediate pass are obtained, and the plurality of plate thickness errors are calculated. From the difference value and the rolling load difference value, the correction coefficient α of the calculation error of the mill elongation amount depending on the rolling load is calculated, and the gauge meter type is calculated from the correction coefficient α of the calculation error of the mill elongation amount and the rolling load after the next time. Fix A method for controlling the thickness of a rolling mill, which is applied during subsequent rolling.
H = S + F / M + K + αF (2)
Here, H: gauge meter thickness (estimated plate thickness), S: roll gap before rolling, F: rolling load, M: mill constant, K: roll gap offset, α: correction coefficient for calculation error of mill elongation

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