JP4623738B2 - Shape control method in cold rolling - Google Patents

Description

  The present invention relates to a method for correcting the amount of work roll crown so that the plate shape of a rolled metal strip does not change according to wear of a backup roll.

In cold rolling, there is a method in which the shape of a rolled material is measured with a shape detector arranged on the delivery side of the rolling mill, and the control amount of shape control means such as roll bender and roll shift is corrected based on the measurement result. Generally adopted. However, the shape of the rolled material is often measured with a shape detector arranged at a position distant from the rolling mill, so that a detection delay occurs and control with high responsiveness may be difficult.
In order to control the shape with high-speed response, the rolling load is measured instead of the direct measurement of the plate shape on the premise that the fluctuation of the rolling load affects the shape change of the rolled material, and the rolling load is measured. Various methods for correcting the control amount of each shape control means based on the values have been proposed (Patent Document 1, Patent Document 2, and Patent Document 3). In any method, the shape of the rolled shape is controlled based on the rolling shape prediction formula expressed as a function of the rolling load. In the rolling shape prediction formula, the rolling shape is evaluated only at one shape in the sheet width direction. Yes. Therefore, when the rolling load fluctuates greatly, it is difficult to obtain a good shape over the entire plate width.

In order to solve such a problem, the present inventors use a mathematical model that incorporates elongation difference at a plurality of locations along the sheet width direction, thereby controlling the shape control means in accordance with the rolling load variation. A method of correcting the amount and manufacturing a steel strip having a good shape over the entire plate width was developed and introduced in Patent Document 4.
Although this method is intended for shape control during rolling, the mathematical model can be applied as it is to preset control for initially setting shape control means at the start of rolling.

The method according to Patent Document 4 is based on the premise that the shape control means has a wide specification range and can be controlled to a target shape over a wide range of rolling conditions. If the ability of the shape control means is sufficient, a good shape can be obtained. It is done. However, when the specification range of the shape control means is narrow, it is difficult to cope with a wide range of rolling conditions, and a good shape may not be obtained. In particular, when the rolling load is large and the ability of the shape control means is insufficient, a large ear extension shape is generated.
Therefore, the present inventors calculated a proper work roll crown amount using a mathematical model incorporating the effect of the work roll crown amount, and applied the work roll to start rolling corresponding to a wide range of rolling conditions. From time to time, a method for producing a steel strip having a good shape over the entire length of the coil was developed and proposed in Patent Document 5.
Japanese Patent Publication No.52-23873 JP 57-7309 A JP-A-8-257612 JP 11-267727 A Japanese Patent Application No. 2006-021314

  In general, in rolling, the work roll is exchanged more frequently than the backup roll from the viewpoint of adjusting the roughness of the rolled material and preventing the transfer of wrinkles generated in the roll to the rolled material. That is, it is common to change the work roll a plurality of times while continuing to use the worn backup roll. If the backup roll is worn, the profile of the backup roll changes, so the amount of bending of the work roll changes and the rolling shape also changes.

However, in the method proposed in Patent Document 5, since the profile change of the backup roll is not taken into consideration, when the work roll crown amount deviates from an appropriate value and the specification range of the shape control means is narrow, a wide range of rolling conditions can be achieved. Correspondence becomes difficult, and a good shape may not be obtained. Especially when the taper is given to the backup roll, the taper part will be greatly worn, so the control range by the shape control means is biased toward the medium elongation side with the increase in the usage time of the backup roll, and the large medium elongation shape Produce.
The present invention has been devised to solve such a problem, and calculates the proper work roll crown amount corresponding to the change in the profile of the backup roll due to wear and replaces the work roll to control the shape. It is an object of the present invention to provide a control method that can compensate for the insufficient capability of the means and can manufacture a rolled material with excellent shape accuracy with high productivity.

In order to achieve the object, the shape control method of the present invention formulates the relationship between the amount of change in the profile of the backup roll due to wear and the rolling length when using the backup roll, and the amount of change in the profile of the backup roll and the work roll crown. Using the amount of change as a variable, a mathematical model representing the amount of change in the elongation difference with respect to the center of the sheet width is created in advance for a plurality of locations with different distances from the sheet edge, and the backup roll By substituting the profile change amount of the backup roll predicted from the relational expression of the profile change amount and the rolling length when using the backup roll into the mathematical model representing the change amount of the elongation difference, according to the profile change of the backup roll due to wear. as the amount of change in elongation difference becomes minimum, the proper word Calculating a change amount of roll crown, and wherein the exchange of work rolls.

  In the present invention, an appropriate change amount of the work roll crown is calculated using a mathematical model that takes into account the influence of the profile change amount of the backup roll due to wear, and the work roll is replaced. Therefore, even if the wear of the backup roll progresses, it is possible to compensate for the insufficient capacity of the shape control means corresponding to a wide range of rolling conditions, and to obtain a rolled material having a good shape over the entire coil length from the start of rolling.

The present inventors calculated the appropriate amount of change of the work roll crown using a mathematical model that takes into account the influence of the profile change amount of the backup roll due to wear, and supports a wide range of rolling conditions by replacing the work roll. Various investigations and investigations were carried out on the cold rolling shape control method to obtain a good shape.
As a result, focusing on the fact that the elongation difference with respect to the center of the sheet width is proportional to the amount of change in the profile of the backup roll for each of multiple locations with different distances from the edge of the plate, It has been found that when a mathematical model incorporating the influence is used, a work roll having an appropriate crown amount corresponding to a wide range of rolling conditions can be used, and a rolled material having a good shape can be produced.
Hereinafter, the shape control method of the present invention will be described with respect to the influence of the wear of the backup roll of the four-high rolling mill, but the same applies to the influence of the wear of the backup roll and intermediate roll of the multi-high rolling mill having six or more stages. Of course, the present invention is applied.

In order to prevent not only simple shape defects such as ear elongation and medium elongation, but also complex elongation that is a complex combination of quarter elongation and various elongations, it is required to evaluate and control the rolling shape with multiple indices. The
Therefore, in the present invention, the rolling shape is evaluated by the difference between the elongation rate at a plurality of locations at different distances from the plate edge and the elongation rate at the center of the plate width. Specifically, the rolling shape is defined by elongation difference ε _e and ε _q with respect to the plate width center of the plate end portion and the quarter portion. Elongation difference epsilon _e, when epsilon _q is el _e elongation of the plate edge, elongation rate el _q quota portion, the elongation of the sheet width center and el _c, respectively formula (1) and (2) It is represented by
ε _e = el _e -el _c (1)
ε _q = el _q −el _c (2)
It should be noted that the measurement positions of the plate end portion and the quarter portion are determined empirically so as to appropriately represent the shape and obtain an accurate mathematical model.

The profile of the backup roll before wear is defined by the diameter difference S _e ⁰ , S _q ⁰ between the central part and the end part and the quarter part of the backup roll. Note that when the barrel length of the backup roll is longer than the body length of the work rolls, backup in S _e ^0, the edge portion of the backup roll diameter and the work rolls at the center of the S _q ⁰ work rolls and quarter unit roll The difference from the diameter. When the diameters of the backup rolls before wear at the end portion, the quarter portion, and the central portion are D _e ⁰ , D _q ⁰ , and D _c ⁰ , respectively, the diameter differences S _e ⁰ and S _q ⁰ before wear are respectively expressed by equations It is represented by (3) and (4).
S _e ⁰ = D _c ⁰ −D _e ⁰ (3)
S _q ⁰ = D _c ⁰ −D _q ⁰ (4)
The positions of the end portion and the quota portion are determined empirically so as to appropriately represent the profile change of the backup roll and obtain an accurate mathematical model.

Similarly, the profile of the backup roll after wear is defined by the diameter difference S _e ¹ , S _q ¹ between the center portion and the end portion and the quarter portion of the backup roll. Note that when the barrel length of the backup roll is longer than the body length of the work rolls, S _e ^1, back up the S _q ¹ at the ends and the quarter portion of the backup roll diameter and the work rolls at the center of the work roll rolls The difference from the diameter. When the diameters of the backup rolls after wear at the end portion, the quarter portion, and the central portion are D _e ¹ , D _q ¹ , and D _c ¹ , respectively, the diameter differences S _e ¹ and S _q ¹ after wear are respectively expressed by equations It is represented by (5) and (6).
S _e ¹ = D _c ¹ −D _e ¹ (5)
^{_{S q 1 = D c 1 -D}} q 1 (6)

Then, the profile change amounts ΔS _e and ΔS _q of the backup roll due to wear are expressed by equations (7) and (8), respectively, as changes in the diameter difference at the end portion and the quarter portion.
ΔS _e = S _e ¹ −S _e ⁰ (7)
ΔS _q = S _q ¹ −S _q ⁰ (8)
If the profile of the backup roll changes, the amount of deflection of the work roll in contact with the backup roll changes, but the relationship between the amount of change in profile ΔS _e , ΔS _{q of the} backup roll and the amount of change in roll deflection covers deformation in the elastic region. Therefore, there is a nearly linear relationship.
Therefore, the profile change amounts ΔS _e and ΔS _{q of} the backup roll and the change amounts Δε _e and Δε _q of the elongation difference ε _e and ε _q are also in a linear relationship as shown in FIGS.

The amount of work roll crown was defined by the difference in diameter between the end of the work roll and the center of the work roll. As shown in FIG. 3, the change amount ΔWr of the work roll crown amount Wr and the change amounts Δε _e and Δε _q of the elongation difference ε _e and ε _q are also in a linear relationship.
From the relationship among the above factors, the prediction formulas for the rolling shape change can be expressed by equations (9) and (10) using a _e , b _e , c _e , a _q , b _q and c _q as influence coefficients. it can.
Δε _e = a _e · ΔS _e + b _e · ΔS _q + c _e · ΔWr (9)
Δε _q = a _q · ΔS _e + b _q · ΔS _q + c _q · ΔWr (10)

The influence coefficients a _e , b _e , c _e , a _q , b _q , and c _q are constants determined by the product type such as plate width, plate thickness, and material, and are either experimental or elastic deformation analysis of the roll and plastic deformation of the material. It can be obtained from a simulation using an analysis model coupled with analysis. Each influence coefficient is set in a table for each section such as plate width, plate thickness, and material, or expressed as a function of plate width, plate thickness, material, and the like.

Regarding the relationship between the amount of change in the profile of the backup roll due to wear and the rolling length when the backup roll is used, the profile of the backup roll is measured for each rolling length as shown in FIG. The quantities ΔS _e and ΔS _q may be obtained and formulated by a regression equation or the like.
When calculating the appropriate work roll crown change amount ΔWr so that the elongation difference does not change in accordance with the change in the backup roll profile due to wear, formula (11) is used for each table section such as plate width, plate thickness, and material. An appropriate value of the amount of change of the work roll crown is calculated so that the evaluation function J shown in FIG.

For the calculation of the appropriate value of the work roll crown change amount for each table category, the backup predicted from the relational expression of the profile change amount of the backup roll and the roll length when using the backup roll corresponding to the rolling length when using the backup roll. The roll profile change amounts ΔS _e and ΔS _q are substituted into the equations (9) and (10), and the change amount of the work roll crown is calculated so that the evaluation function represented by the equation (11) is minimized.
Then, the appropriate value of the work roll crown change amount for each table section is averaged and replaced with a work roll whose crown is changed by the average value ΔWr.
^{_{J = w e · Δε e 2}} + w q · Δε q 2 (11)
In the equation, w _e and w _q indicate weighting factors.

In the above description, the rolling shape is defined by the elongation difference ε _e and ε _q with respect to the center of the plate width at the two points of the plate end portion and the quarter portion, the appropriate work roll crown change amount ΔWr is calculated, and the work roll is We are exchanging. However, the present invention is not constrained to this, and the amount of change in the work roll crown is similarly applied when the rolling shape is defined using the elongation difference with respect to the center of the sheet width at three or more points along the sheet width direction. Can be optimized.
The backup roll profile before and after the wear is defined by the diameter difference S _e ⁰ , S _q ⁰ , S _e ¹ , S _q ¹ between the central part and the end part and the quarter part of the backup roll. It can also be defined by the difference in diameter between the center of the roll and three or more positions along the body length direction.

An example in which the present invention is applied to cold rolling using the four-high rolling mill shown in FIG. 5 will be described. The four-high rolling mill 1 includes a work roll bender 2 as a shape control means on a work roll 5. In addition, rolling conditions are input to the host computer 3, and the process computer 4 has influence coefficients a _e , b _e , c _e , a _q , b _q , c calculated in advance for each of the width, thickness, and material classification. _q is taken in.
Regarding the relationship between the amount of change in the profile of the backup roll 7 due to wear and the rolling length when using the backup roll, the profile of the backup roll is measured for each rolling length, and as shown in FIG. The amounts of change ΔS _e and ΔS _q were obtained and formulated by regression equations shown in equations (12) and (13). Then, the equations (12) and (13) are taken into the process computer 4.
ΔS _e = −0.74 × 10 ⁻¹⁰ · L ² + 0.39 × 10 ⁻³ · L (12)
ΔS _q = 0.19 × 10 ⁻¹⁰ · L ² + 0.44 × 10 ⁻⁴ · L (13)
Here, L is the rolling length when using the backup roll.

First, an appropriate work roll crown amount immediately after the use of the backup roll was calculated by the method proposed in Patent Document 5, and 90 μm was applied to the work roll 5 as an appropriate crown amount. For each coil, an appropriate work roll bender force was calculated and set by the method proposed in Patent Document 5 as well. And after rolling start, it rolled, controlling based on the output value of the shape detector 6. FIG.
A work roll crown change amount appropriate value ΔWr is calculated based on the equations (9), (10), and (11) at each work roll replacement timing, and the work roll is changed by ΔWr as shown in FIG. Replaced with 5. Even after the work roll replacement, an appropriate work roll bender force was calculated and set by the method proposed in Patent Document 5, and after starting rolling, rolling was performed while controlling based on the output value of the shape detector 6. For comparison, when using a work roll having a crown amount of 90 μm without considering the wear of the backup roll, an appropriate work roll bender force is calculated and set by the method proposed in Patent Document 5, and after rolling starts, Rolling was performed while controlling based on the output value of the shape detector 6.

According to the present invention, when a roll length when using a backup roll is 9 × 10 ⁵ m, a work roll having a crown amount of 40 μm is used, and skin pass rolling with a plate width of 1000 mm, a plate thickness of 2.0 mm and an elongation of 2.0% is performed. As shown in FIG. 8, the steel strip thus obtained had a steepness within 0.5% over the entire length of the coil from the start of rolling, and was rolled into a good shape.
On the other hand, as a comparative example, a work roll having a crown amount of 90 μm is used when the roll length when using a backup roll is 9 × 10 ⁵ m, and the elongation is 2.0% at a plate width of 1000 mm and a plate thickness of 2.0 mm. The steel strip subjected to the skin pass rolling had a large middle elongation with a steepness of 1.0% or more over the entire length of the coil from the start of rolling.

Graph showing the effect on the amount of change in profile variation [Delta] S _e is the elongation difference between the backup roll Graph showing the effect of backup roll profile change ΔS _q on the change in elongation difference A graph showing the effect of change in work roll crown on change in elongation difference Graph showing the profile of the backup roll before and after wear Schematic diagram of the four-high rolling mill and control system used in the examples Graph showing the relationship between the rolling length when using a backup roll and the amount of change ΔS _e , ΔS _q of the diameter difference at the end and quarter The graph which shows the relationship between the rolling length at the time of use of the backup roll in an Example, and the amount of work roll crowns The graph which shows the steepness of the steel strip rolled in the Example

Explanation of symbols

1: Four-high rolling mill 2: Work roll bender 3: Upper computer 4: Process computer 5: Work roll 6: Shape detector 7: Backup roll

Claims (1)

Formulate the relationship between the amount of change in the backup roll profile due to wear and the rolling length when using the backup roll, and use the amount of change in the profile of the backup roll and the amount of change in the work roll crown as variables, and multiple locations with different distances from the plate edge A mathematical model representing the amount of change in the elongation difference with respect to the center of the sheet width is created in advance, and the relationship between the amount of change in the profile of the backup roll and the rolling length when using the backup roll corresponds to the rolling length when using the backup roll. By substituting the predicted amount of change in the profile of the backup roll into the mathematical model that represents the amount of change in the elongation difference , an appropriate amount is set so that the amount of change in the elongation difference is minimized according to the profile change of the backup roll due to wear. Calculate the amount of work roll crown change and Shape control method in cold rolling, characterized in that the conversion.

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