JPH11267727A - Method for controlling shape of hot rolled band-shaped sheet before pickling in cold rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute cold rolling of a hot rolled band-shaped sheet before pickling with deposited scale into a favorable shape. SOLUTION: A numerical formula model is previously formed to indicate a difference of elongation percentage of a plurality of spots at different distances from the side edges to the center of the width of the sheet, and taking up actully measured values of continuous measurement of rolling load as variables, based on the numerical formula model, a control amount of an intermediate roll bender 1 and/or a work roll bender 2 is calculated and adjusted so that the difference of elongation percentage may coincide with a target value. In the case that thus calculated control amount of the intermediate roll bender 1 or the work roll bender 2 is deviated from the maximum value or the minimum value in the range of specification, the maximum value or the minimum value is taken into the numerical formula model, and then a control amount of the other work roll bender 2 or the intermediate roll bender 1 is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cold rolling a hot-rolled steel strip before pickling while controlling a coil shape.

[0002]

2. Description of the Related Art As for shape control in cold rolling, the shape of a rolled material being rolled is measured by a shape detector arranged on the exit side of a rolling mill, and shape control such as roll bender and roll shift is performed based on the measurement result. A method of correcting the control amount of the means is generally used. However, since the shape of the rolled material is measured by a shape detector arranged at a position distant from the rolling mill, a detection delay occurs, and it is difficult to perform control with high responsiveness. Therefore, the rolling load was measured in place of the direct measurement of the plate shape on the premise that the variation in the rolling load affected the shape change of the rolled material,
A method of correcting the control amount of each shape control means based on the measured value is introduced (Japanese Patent Publication No. 52-23873, Japanese Patent Application Laid-Open No. 57-7309, Japanese Patent Application Laid-Open No. 8-2576).
No. 12).

In some cases, a hot-rolled steel strip before pickling is cold-rolled before pickling (hereinafter referred to as cold-rolling before pickling) in order to improve descalability. When a contact roll type shape detector is used in cold rolling before pickling, it is susceptible to the adhesion of scale peeled from the steel strip during rolling, and it is difficult to measure the plate shape with high accuracy. In addition, there is a problem in using a contact roll type shape detector from the point that the roll is flawed by the peeled scale and the flaw is transferred to a rolled material to become a flaw. On the other hand, the non-contact excitation shape detector has a drawback in that the range of the plate thickness that can be measured is limited, and the measurement accuracy is reduced in a rolled material having a large plate thickness.

[0004]

In cold rolling before pickling, the lubricating state changes according to the scale peeling state during rolling, and the rolling load greatly fluctuates. The sheet thickness also changes with the change in the rolling load. As a result, when the automatic thickness control is performed by operating the reduction device, the rolling position is changed, and the fluctuation of the rolling load is enlarged as compared with the case where the automatic thickness control is not performed. Therefore, a method of correcting the control amount of the shape control means based on the measured value of the rolling load described above is adopted. In this case, the rolling shape is controlled based on a rolling shape prediction formula that expresses the rolling shape as a function of the rolling load. In the rolling shape prediction formula, the rolling shape is evaluated using only one shape in the sheet width direction. . Therefore, even if a good shape can be obtained over the entire width of the strip when rolling pickled materials with small fluctuations in rolling load, a good shape can be obtained over the entire width of the strip with cold rolling before pickling, where the rolling load fluctuates greatly. Is difficult and the shape is often defective.

[0005]

SUMMARY OF THE INVENTION The present invention has been devised in order to solve such a problem. By using a mathematical model which takes in elongation differences at a plurality of locations in the width direction of the sheet, An object of the present invention is to correct a control amount of a shape control unit in accordance with a change in a rolling load, and to manufacture a steel strip having a good shape over the entire width of a sheet. In order to achieve the object, the shape control method of the present invention previously creates a mathematical model with a variable rolling load representing an elongation difference with respect to the center of the sheet width at a plurality of points having different distances from the sheet edge, and continuously creates the model. A control value of the intermediate roll bender and / or the work roll bender is calculated and adjusted so that the measured rolling load measured value is substituted into the mathematical model so that the elongation difference matches the target value. If the calculated control value of the intermediate roll vendor or work roll vendor deviates from the maximum value or the minimum value of the specification range, incorporate the maximum value or minimum value into the mathematical model, and control the other work roll vendor or intermediate roll vendor. Is calculated.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors correct the control amount of each shape control means in consideration of the fluctuation of the rolling load so that the shape of cold rolling before pickling can be obtained so that a good shape can be obtained over the entire width of the sheet. Various control methods were investigated and studied. As a result, paying attention to the fact that the difference between the elongation rate at a plurality of places at different distances from the sheet edge and the elongation rate at the center of the sheet width is proportional to the rolling load, the effect of the rolling load on the difference in elongation rate is considered. Using the imported mathematical model, the inventors found that the shape control means worked with high accuracy and high responsiveness, and that a hot-rolled steel strip before pickling having a good shape was produced. In cold rolling before pickling, not only simple shape defects such as ear elongation and medium elongation but also complex elongation, which is a complex combination of quarter elongation and various types of elongation, occurs in the rolled material. In order to always obtain a good shape over the entire sheet width in cold rolling before pickling in which such complicated shape defects are likely to occur, it is necessary to evaluate and control the rolling shape with a plurality of indices.

Therefore, in the present invention, the elongation is measured at a plurality of different positions in the sheet width direction, and the difference between the measured elongation and the elongation at the center of the sheet width is determined. Has been evaluated. Specifically, the rolled shape is defined by the elongation differences ε _e and ε _q of the plate edge and the quarter portion with respect to the center of the plate width. Elongation difference epsilon _e, is epsilon _q, when el _e elongation of the plate edge, el _q elongation quota portion, the elongation of the sheet width center and el _c, equation (1), (2) Respectively. Note that the measurement positions of the plate edge and the quarter portion are empirically determined so as to appropriately represent the shape and obtain an accurate mathematical model. ε _e = el _e −el _c (1) ε _q = el _q −el _c (2)

Factors that affect the shape of the rolled material include disturbances such as plate thickness, material, lubrication state, and rolling load, and control amounts of shape control means such as an intermediate roll bender, a work roll bender, and an intermediate roll shift. . The sheet thickness is an important quality item, and is usually controlled to be substantially constant by automatic sheet thickness control. The lubrication state, which is a major factor in the cold rolling before pickling, is affected by the shape of the rolled material.
Most of the effect is caused by a change in roll deflection according to a change in rolling load. Therefore, the main factors causing the shape change during rolling are the rolling load and the control amount of the shape control means. Typical examples of the shape control means include an intermediate roll bender, a work roll bender, and an intermediate roll shift. However, in consideration of responsiveness, the intermediate roll shift is fixed during rolling and the intermediate roll bender and the work roll bender are controlled. Preferably, it is used as a means.

[0009] When the rolling load changes, the deflection of the roll due to the rolling reaction force changes, and changes the shape of the rolled material. Here, since the rolling load per unit width and the amount of deflection of the roll are in a linear relationship, the rolling shapes ε _e and ε _q expressed by the equations (1) and (2) are also equal to the unit width as shown in FIG. It has a linear relationship with the rolling load per hit. The intermediate roll bender and the work roll bender also change the roll shape by changing the roll deflection like the rolling load.
As shown in (1), a linear relationship is established between the intermediate roll bender and the work roll bender and the rolling shapes ε _e and ε _q . Therefore, the rolling shape prediction formula is represented by formulas (3) and (4).

[0010] _{ε e = a e · p +} b e + c e · F I + d e · F W ···· (3) ε q = a q · p + b q + c q · F I + d q · F W ···· (4) However, p: rolling load per unit width F _I: control amount of the intermediate roll bender F _W: control quantity a _e of the work roll _{bender, b e, c e, d} e, a q, b q, c _q , _dq : Influence coefficient

[0011] The influence coefficient _{a e, b e, c e} , d e, a q,
b _q , c _q , and d _q are constants determined by the product type, such as the sheet width, sheet thickness, and material, and are simulations based on experiments or analysis models obtained by coupling the elastic deformation analysis of a roll and the plastic deformation analysis of a material. Respectively. For example, when all the other rolling conditions are kept constant and the control amounts F _I and F _{W of} each shape control means and the rolling load p per unit width are changed, the control amounts F _I and F _W and the rolling load p And the rolling shape ε _e , ε _q . Each influence coefficient is set in a table for each category such as sheet width, sheet thickness, material, etc.
Formulated as a function such as material. In cold rolling before pickling, the lubricating state changes according to the scale peeling state during rolling, so that the rolling load greatly changes as shown in FIG. For example, what was initially a large rolling load at the beginning of rolling,
As the scale peeling progresses, the rolling load decreases significantly. Therefore, in order to prevent the rolling shape from being deteriorated by the fluctuation of the rolling load, the rolling load P is continuously measured with a load meter, and the rolling load per unit width is calculated from the rolling load P and the sheet width w according to the formula (5). Calculate p. Based on the calculation results, the rolling shapes ε _e , ε _q represented by equations (3) and (4)
Controlled variable F _W of but controlled variable F _I and the work roll bender of the intermediate roll bender such that each target value ε _e ^0, ε _q ⁰
Is constantly corrected. p = P / w (5)

When the rolling load at the time of rolling greatly fluctuates, the rolling shapes ε _e and ε expressed by the equations (3) and (4) are used.
_q is each target value epsilon _e ^0, either or both of the control amount F _W of the controlled variable F _I and the work roll bender of the calculated intermediate roll bender such that epsilon _q ⁰ can exceed its specification range There is. In this case, the control amounts F _I and F _W of the shape control means that exceed the specification range are set to the maximum value or the minimum value, and the shape control that does not exceed the specification range is performed so that the evaluation function J expressed by the equation (6) is minimized. The control amount of the means is calculated and constantly corrected. However, w _e, w _q of formula (6), respectively indicate weighting factors. _{J = w e (ε e -ε} e 0) 2 + w q (ε q -ε q 0) 2 ···· (6)

For example, the control amount F of the intermediate roll bender calculated so that the rolling shapes ε _e and ε _q represented by the equations (3) and (4) become the target values ε _e ⁰ and ε _q ⁰ , respectively. among the control amount F _{W I} and the work roll bender, when the control amount F _W of the work roll bender exceeds the maximum value F _Wmax of the specification range, the maximum value F _Wmax the controlled variable F _W.
On the other hand, when the control amount _FW of the work roll vendor is smaller than the minimum value _FWmin of the specification range, the control amount _FW is set to the maximum value _FWmin . Thus, equations (3) and (4) are rewritten as equations (7) and (8), respectively. _{ε e = a e · p +} b e '+ c e · F I ···· (7) ε q = a q · p + b q' + c q · F I ···· (8) However, b _e 'and b _q 'Is a function represented by equations (9) and (10). _{b e '= b e + d} e · F Wmax or _{b e' = b e + d} e · F Wmin ···· (9) b q '= b q + d q · F Wmax or _{b q' = b q + d} q・ F _Wmin・ ・ ・ ・ （10）

Substituting equations (7) and (8) into equation (6),
The evaluation function J is calculated controlled variable F _I of the intermediate roll bender that minimizes, constantly corrected. The control amount F _I of the intermediate roll bender is the maximum value F _Imax or the minimum value F _{Im of the} specification range.
_{In the} case of deviation from "_in" , the control amount _FW of the work roll bender is calculated in the same manner and is constantly corrected. In a rolling mill provided with one of the shape control means of the intermediate roll bender and the work roll bender, it is handled in the same manner as when the shape control means is out of the specification range, and the control amount of the provided shape control means is calculated. Then, it is constantly corrected based on the calculated value. In the above description, the rolling shape is defined by the elongation difference with respect to the center of the sheet width at two points of the sheet edge and the quarter, and each shape control means is corrected. However, the present invention is not limited to this. For example, even when the rolled shape is defined by the elongation difference with respect to the center of the sheet width in three or more sheet width directions, the evaluation function similar to the equation (6) is obtained. Can be used to control the rolling shape.

[0015]

EXAMPLE As shown in FIG. 5, a 6-high rolling mill 3 having an intermediate roll bender 1 and a work roll bender 2 as shape control means was used, and a work roll having a diameter of 300 mm, a sheet width of 1060 mm and a sheet thickness of 3.0 mm. Was rolled to a sheet thickness of 1.5 mm. The rolling conditions were previously input to the host computer 4, and the measured values of the rolling loads continuously measured by the load cells 5 were input. In the process computer 6, the optimum control amounts of the intermediate roll bender 1 and the work roll bender 2 are calculated from the actually measured values by taking in the influence coefficients calculated in advance for each type of production such as plate width, plate thickness, and material. The calculated values are input to the intermediate roll bender 1 and the work roll bender 2, respectively, and the respective control amounts F _I and F _W are corrected. The rolled shape was defined by a difference in elongation percentage with respect to the center of the plate width at two points of the plate end and the quarter portion, and was represented by ε _e and ε _q in equations (1) and (2). At this time, as the position of the plate end, a position 20 mm inward from the plate end where the influence of the measurement error and the calculation error of the influence coefficient was small was selected. The quarter part is w / (2√2) from the center of the sheet width where the peak of the shape easily occurs in the rolling mill used.
Was selected.

During rolling, the rolling load P was continuously measured by the load meter 5, and the rolling load p per unit width was calculated from the rolling load P and the sheet width w according to the equation (5). Then, equation (3) and rolling shape represented by (4) ε _e, ε _q each target value ε _e ^0, ε _q ⁰ and becomes such an intermediate roll bender 1 of the controlled variable F _I and the work roll bender The control amount _{FW of} 2 was calculated. Note that the target values ε _e ⁰ and ε _q ⁰ of the rolling shape are both ε _e ⁰ =
0, ε _q ⁰ = 0. Since calculated control amount F _I and F _W was both a specification range was continued rolling while correcting the intact control amount.

During rolling, the rolling load changed as shown in FIG. On the other hand, in the rolling according to the conventional method in which the rolling shape is controlled based on the rolling shape prediction formula in which the rolling shape is evaluated only at one location in the sheet width direction, there is no great difference from the method of the present invention as far as the rolling load is concerned. . However, the rolled shape was measured at 20 positions in the sheet width direction using an off-line shape measuring instrument, and the maximum steepness in the sheet width direction was obtained as the maximum value of the obtained steepness distribution. As is clear from the comparison, the shape deteriorates with the progress of rolling in the conventional method,
The maximum steepness exceeded. On the other hand, in the rolling according to the present invention, the maximum steepness was within 0.5%, which indicates that a steel strip having a good shape was obtained.

[0018]

As described above, according to the present invention, when controlling the rolling shape based on the rolling shape prediction formula in consideration of the load variation, the rolling is performed by using a plurality of indexes in the rolling shape prediction formula. The shape is being evaluated. Therefore, the rolling load fluctuates greatly due to the effect of the scale, and even if the steel strip before pickling cannot use a shape detector because of scale or scale peeling pieces on the steel strip surface, it is rolled into a good shape over the entire length. You.

[Brief description of the drawings]

FIG. 1 is a graph showing an effect of a rolling load per unit width on a rolling shape.

FIG. 2 is a graph showing an influence of a control amount of an intermediate roll bender on a rolling shape.

FIG. 3 is a graph showing an influence of a control amount of a work roll bender on a rolling shape.

FIG. 4 is a graph showing, in the longitudinal direction of a coil, a change in rolling load when a steel strip before pickling is rolled.

FIG. 5 is a schematic diagram of a six-high rolling mill and a control system used in the embodiment.

FIG. 6 is a graph showing a change in rolling load when a steel strip before pickling is rolled under control conditions according to the present invention, in comparison with a conventional method.

FIG. 7 is a graph comparing the steepness of a steel strip rolled according to the present invention with the steepness of a steel strip rolled by a conventional method.

[Explanation of symbols]

1: Intermediate roll vendor 2: Work roll vendor
3: 6-high rolling mill 4: Host computer 5: Load cell 6: Process computer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuhiko Okano 962-14 Hojo, Toyo City, Ehime Prefecture Nisshin Steel Co., Ltd.

Claims (2)

[Claims] An equation model is prepared in advance with a rolling load representing a difference in elongation relative to the center of a sheet width as a variable for a plurality of locations at different distances from a sheet edge, and an actual measured value of a continuously measured rolling load is calculated using the equation. Cold rolling of a hot-rolled steel strip before pickling, wherein a control amount of an intermediate roll bender and / or a work roll bender is calculated and adjusted so as to be substituted into a model so that the difference in elongation is equal to a target value. Shape control method. 2. When the calculated control amount of the intermediate roll vendor or the work roll vendor deviates from the maximum value or the minimum value of the specification range, the maximum value or the minimum value is taken into a mathematical model, and the work roll vendor or the intermediate roll vendor is obtained. The shape control method according to claim 1, wherein the control amount is calculated.