US-12617008-B2 - Thickness controlling method and rigidity monitoring method for rolling mill

US12617008B2US 12617008 B2US12617008 B2US 12617008B2US-12617008-B2

Abstract

A thickness controlling method for a rolling mill includes using a regression model to recursively approximate a relationship between the roll force change amount between the preceding material and the present material and a gap error change amount of the rolling mill, and predicting a gap error in a rolling of the present material on the basis of the regression model, the preceding material being a rolled coil rolled by the rolling mill immediately prior, and the present material being another rolled coil to be rolled following the preceding material, correcting a gap setting amount in the rolling of the present material, on a basis of a value of the predicted gap error, and updating a regression coefficient of the regression model, on a basis of an actual roll force and an actual gap error change amount obtained from the rolling of the present material.

Inventors

Toshihito SHIMOTANI

Assignees

TMEIC CORPORATION

Dates

Publication Date: 20260505
Application Date: 20220808

Claims (4)

1 . A thickness controlling method for a rolling mill that rolls a material to be rolled so as to have a target thickness, the thickness controlling method comprising: a step of using a regression model to recursively approximate a relationship between a roll force change amount between a preceding material and a present material and a gap error change amount of the rolling mill, and predicting a gap error in a rolling of the present material on the basis of the regression model, the preceding material being a rolled coil rolled by the rolling mill immediately prior, and the present material being another rolled coil to be rolled following the preceding material; a step of correcting a gap setting amount in the rolling of the present material, on a basis of a value of the predicted gap error; and a step of updating a regression coefficient of the regression model, on a basis of an actual roll force and an actual gap error change amount obtained from the rolling of the present material.
2 . The thickness controlling method for the rolling mill according to claim 1 , wherein a difference is calculated between the gap error change amount predicted by the regression model by using the actual roll force and the actual gap error change amount, and when the calculated difference is larger than a reference value, the regression coefficient is not updated, and a most recent regression coefficient is maintained.
3 . A rigidity monitoring method for a rolling mill comprising: a step of determining whether there is a chronological change in rigidity of the rolling mill on a basis of a time-series transition in the regression coefficient updated at each rolling with the thickness controlling method for the rolling mill according to claim 1 ; and a step of issuing a notification when it is determined that the chronological change has occurred in the rigidity of the rolling mill.
4 . A rigidity monitoring method for a rolling mill comprising: a step of determining whether there is a chronological change in rigidity of the rolling mill on a basis of a time-series transition in the regression coefficient updated at each rolling with the thickness controlling method for the rolling mill according to claim 2 ; and a step of issuing a notification when it is determined that the chronological change has occurred in the rigidity of the rolling mill.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is based on PCT filing PCT/JP2022/030309, filed Aug. 8, 2022, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a thickness controlling method and a rigidity monitoring method for a rolling mill. BACKGROUND ART In rolling processes, to control the thickness of a material to be rolled with a high level of precision, it is necessary to appropriately set a gap between rolls of a rolling mill. When the gap is to be set, a gap setting value is determined through a calculation employing a model (a gauge meter model) used for calculating the rolling mill gap while taking into consideration gap fluctuations caused by various factors including an elastic deformation (a mill elongation) of the rolling mill caused by a reaction force (a roll force) from the material to be rolled. Accordingly, to enhance the precision level for thicknesses, it is important to improve the precision level of the gauge meter model. The amount of the aforementioned mill elongation is dependent on the strength of the rolling mill (rolling mill rigidity) against the elastic deformation. The rolling mill rigidity is estimated from a result of a measuring test called a mill curve measuring process. A mill curve is a characteristic curve obtained as a relationship between the mill elongation amount and the roll force applied to the rolling mill. That is to say, the gradient of a mill curve expresses rigidity of the rolling mill. The gauge meter model predicts the gap, on the basis of a predicted mill elongation amount derived from the mill curve corresponding to a predicted roll force, so as to determine the gap setting value. Examples of typical mill curve measuring methods include tightening methods. According to a tightening method, while top and bottom work rolls of a rolling mill are in direct contact with each other (called a kiss roll state) having no plate therebetween, a pressing screw is tightened while the rolls are rotated. The rolling mill rigidity is estimated from a relationship between a measured tightening amount and the roll force. Because this process needs to be performed while the operation is suspended, the mill curve measuring process is not frequently performed. As a result, an estimated result based on a past measured result tends to be used for a long period of time. In the aforementioned prediction using the gauge meter model, chronological changes in the rolling mill rigidity may impact the precision level of the calculation of the gap setting value. Both FIGS. 6 and 7 are graphs in which roll force change amounts (each being the difference between a roll force of a coil (a preceding material) rolled immediately prior and a roll force of another coil (a present material) rolled next) are plotted along the horizontal axis, whereas gap error change amounts (each being the difference between a gap error of the preceding material and a gap error of the present material) are plotted along the vertical axis. The tendency exhibited in FIG. 6 is a tendency observed when there is a small prediction error in the mill elongation amounts. No correlation is observed between the two variables, namely the roll force change amounts and the gap error change amounts. In contrast, the tendency exhibited in FIG. 7 is a tendency observed when there is a large prediction error in the mill elongation amounts. A correlation is observed between the two variables. In other words, in FIG. 7, the gap error change amounts occur as being caused by the roll force change amounts. As explained above, the prediction error in the mill elongation amounts caused by the chronological changes in the rolling mill rigidity could be a cause of a gap error. However, because the mill rigidity is directly available only from the mill curve measuring process, it is difficult to take such an error into consideration in a rolling model. In relation to the above, to improve precision levels of gauge meter models, PTL 1 and PTL 2 listed below have proposals. PTL 1 discloses a method by which a roll force fluctuation value that satisfies a gauge meter formula is calculated while dynamic characteristics of a rolling mill are taken into consideration, so as to calculate a correction amount for a roll gap by using the calculated dynamic characteristic roll force fluctuation value. Further, PTL 2 discloses a method by which condition items (certain operation factors and a mill elongation amount) are weighted according to similarities with past data calculated under the condition items, so as to calculate coefficients of impact imposed on the roll force by the condition items with respect to a material to be rolled in question, so as to use, in a gauge meter formula, one of the coefficients of impact (a mill constant) imposed on the roll force by the mill elongation amount. CITATION LIST Patent Literature [PTL 1] Japanese Patent No. 5627553[PTL 2] JP