JP2010227970A - Method of controlling plate thickness - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of highly precisely controlling a plate thickness by a mill stretch system which can correspond to a rolling mill provided with intermediate roll benders which are used in recent years and, furthermore, a UC mill which is provided with the intermediate roll benders having asymmetrical force working points. <P>SOLUTION: In the method of controlling the plate thickness by estimating mill stretch with the rolling mill having the intermediate roll benders, the influence of the intermediate roll bending force exerted on the mill stretch is taken as a polynomial function and it is added to a mill stretch model expression in which the intermediate roll bending force is not taken into consideration. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rolling mill equipped with an intermediate roll bender, and also includes a midpoint in the roll width direction of an action point of an intermediate roll bender force acting on both sides of the intermediate roll, and a midpoint in the roll width direction of the body length of the intermediate roll. The present invention relates to a plate thickness control method for estimating a mill stretch in a rolling mill equipped with an intermediate roll, and estimating and controlling a plate thickness based on the estimated mill stretch.

  Conventionally, as a sheet thickness control method in sheet rolling, a method of estimating a sheet thickness immediately below a roll bite and controlling based on an error between an estimated sheet thickness and a target sheet thickness, and a sheet thickness meter installed on the exit side of the rolling mill A method of controlling based on an error between the detected value and the target plate thickness is mainly used. The latter basic configuration feeds back the detected value, and there is a method in which modern control is added to it. However, in this control, dead time increases. Among the former methods, the mass flow method and the mill stretch method are mainly employed as the method for estimating the plate thickness.

  As shown in Non-Patent Document 1, the mass flow method is a method for estimating the exit side plate thickness from the output of the entrance side plate thickness meter and the input side plate speed meter and the output of the exit side plate speed meter according to the constant mass flow rule. It is characterized in that the plate thickness immediately below can be estimated continuously and the plate thickness can be estimated by a simple calculation formula. However, when using a mass flow thickness control method, the thickness gauge usually uses a filter to remove high-frequency components. For example, the vicinity of a joint in cold rolling or biting in hot rolling Immediately after that, the mass flow estimation plate thickness is not stable, and the plate thickness estimation accuracy is lowered.

On the other hand, the mill stretch method estimates the elastic deformation of the rolling mill by the rolling load and roll bending force, that is, the mill stretch (change amount of the roll gap), and captures the change in thickness as the change in mill stretch. It is a method to control.
As one of the mill stretch methods, ignoring the elastic deformation in the low load range, the relationship between the mill stretch and the load in the load range mainly used for actual rolling is the mill constant (mm / tonf, constant value or table value). ), And a method of controlling the plate thickness change when the load or bending force is changed from the mill constant and calculating the reduction change amount is known as BISRA AGC (BISRA Automatic Gauge Control). In this method, the plate thickness cannot be estimated by an absolute value, and follows a relative change, and is also called a relative value gauge meter AGC. Since BISRA AGC cannot estimate the plate thickness with an absolute value, feedback by a plate thickness meter installed on the delivery side of the rolling mill is indispensable, and is unsuitable for controlling unsteady parts such as the plate tip.

  Further, by using a mill stretch method that takes into account the non-linearity of the mill stretch in the low load range, which is basically described in Patent Document 1 (Japanese Patent Laid-Open No. 60-30508), the plate thickness is reduced to the initial value. The absolute value can be estimated with high accuracy as the sum of the gap between work rolls and the mill stretch. This method is called an absolute value gauge meter AGC because the plate thickness is estimated by an absolute value, and since the plate thickness directly under the roll bite of the rolling mill can be estimated, the control can be performed with very little dead time. It is superior to the control group.

  In recent years, particularly in the field of cold rolling, a six-high rolling mill called a UC mill is often used. Comparing the UC mill and the conventionally used six-high rolling mill, the conventional six-high rolling mill is equipped with a bender only on the work roll, whereas the UC mill is equipped with a bender on the intermediate roll as well. . Although the control end is increased, the control of the plate shape is excellent. However, if the plate thickness is not estimated in consideration of the influence of the intermediate roll bender force, the plate thickness estimation accuracy deteriorates.

In some UC mills, in recent years, the midpoint of the intermediate roll bending force acting point in the roll width direction and the midpoint of the intermediate roll body length in the roll width direction do not coincide with each other. In this case, since the influence of the moment due to the intermediate roll bender force becomes asymmetrical, it is more difficult to estimate the thickness. However, it should be noted that since the upper and lower sides of the steel plate are roughly point-symmetric, the rolling mill as a whole is not asymmetrical.
Furthermore, according to the estimation model of the sheet thickness by the present inventors described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-11546), the mill stretch (roll gap in the mill) is calculated from the load value applied to the rolling roll during rolling. Change amount) can be immediately determined, and the plate thickness can be corrected.

Japanese Patent Laid-Open No. 60-30508 JP-A-2005-11546

"Theory and Practice of Sheet Rolling" edited by the Japan Iron and Steel Institute Joint Study Group, Rolling Theory Section, Japan Iron and Steel Institute, issued on September 1, 1984

As described above, the control method using the absolute value gauge meter AGC is considered to be the best as the control method for estimating and controlling the thickness directly under the roll bite. However, the thickness control by the mill stretch method necessary for this method is considered. The method has the following problems. That is, with the absolute value AGC based on the mill stretch method described in Patent Document 1, a rolling mill having an intermediate roll bender has been developed at the stage where Patent Document 1 is disclosed, although high response plate thickness control can be performed. Was not. Therefore, since the intermediate roll bender developed and introduced in recent years and the intermediate roll bender having an asymmetrical roll bending force action point are not considered, the mill stretch estimation accuracy may be deteriorated.
Regarding the mill stretch model of Patent Document 2, the influence of the intermediate roll bending force is not taken into consideration, and has the same problem as Patent Document 1.

  Therefore, in view of the above problems, the present invention is a mill stretch that can be applied to a rolling mill equipped with an intermediate roll bender used in recent years and a UC mill equipped with an intermediate roll bender having an asymmetrical force acting point. An object of the present invention is to provide a highly accurate plate thickness control method using a method.

  According to the present invention, there is provided a sheet thickness control method for controlling a sheet thickness by estimating a mill stretch with a rolling mill having an intermediate roll bender, wherein the influence of the intermediate roll bending force on the mill stretch is determined by the intermediate roll bending force. A sheet thickness control method is provided, which is added as a polynomial function to a mill stretch model equation that does not consider the intermediate roll bending force.

  Further, according to the present invention from another viewpoint, the mill stretch is separated into the deformation of the roll system and the deformation other than the roll system by a rolling mill having an intermediate roll bender, and the kiss roll is tightened in advance for the deformation other than the roll system. Is a sheet thickness control method for controlling the sheet thickness by estimating and adding the deformation of the roll system during rolling and adding the deformation, and the estimation of the mill stretch takes into account the influence of the intermediate roll bending force Calculate the influence amount of the intermediate roll bending force by dividing into the power term and the unnecessary consideration term, and the influence amount of the intermediate roll bending force to the influence amount of the mill stretch of the unnecessary term considering the influence of the intermediate roll bending force. A sheet thickness control method is provided which is performed in an overlapping manner.

  The estimation of the mill stretch is divided into a term that should consider the roll width direction asymmetry of the intermediate roll bending force and a term that does not need to be considered, and the middle point of the intermediate roll body length in the roll width direction and both sides of the intermediate roll. The amount of influence on the mill stretch that takes into account the left-right asymmetry of the point of action of the intermediate roll bending force that acts on the roll is calculated. You may superimpose.

  Further, the roll deformation contribution of the backup roll, intermediate roll and work roll and the width direction distribution of the contact load between the backup roll, intermediate roll and work roll are affected by the intermediate roll bending force or the intermediate roll bending force. Assuming a linear distribution uniquely determined from the balance conditions of the forces and moments of the backup roll, the intermediate roll and the work roll in consideration of the influence of the width direction left-right asymmetry of the action point, the backup roll, The flat deformation of the intermediate roll and the work roll is obtained, and the backup roll, the intermediate roll, and the work roll are overlapped on the basis of the integral average straight line related to the contact area with the adjacent roll of the backup roll and the work roll. It calculates the sum of Wami, by a method of superimposing a deflection the said flat deformable, the effect of the intermediate roll bending force may be considered.

  According to the present invention, a high-precision plate by a mill stretch method that can be used for a rolling mill equipped with an intermediate roll bender that has been used in recent years, and a rolling mill equipped with an intermediate roll bender having an asymmetrical force acting point. A thickness control method is provided. The intermediate roll bending force is about several tens to one hundred tons / chock (several hundreds to one thousand kN / chock), and an error reduction of about several tens to several hundreds of μm with respect to the mill stretch can be achieved only by considering this. Especially for the asymmetric rolling mill, it is possible to accurately consider the influence of the bending force moment on the mill stretch, and the plate after accurately grasping the mill stretch change due to the influence of the intermediate roll bending force. Thickness control is possible. Thereby, there is a possibility that a plate thickness estimation error of about several tens of μm may be removed, so that the accuracy of plate thickness control is improved and the yield is improved. Here, the symmetrically acting bending force action point can be treated as a singular point of the asymmetric action point in calculation. This point will be explained again below along with the formula description.

  In addition, according to the present invention, a mill stretch model formula that can be used online is created. Therefore, in an actual machine, high precision plate thickness control can be achieved by applying this mill stretch model formula regardless of rolling conditions. It becomes possible. Furthermore, since the plate thickness control method according to the present invention can be applied to an actual machine only by software change, it is possible to improve the plate thickness control accuracy at low cost.

It is a graph which shows the result of having measured the mill stretch change when an intermediate roll bending force is loaded (plate thickness change). It is explanatory drawing of a cold tandem rolling mill. It is explanatory drawing which looked at the rolling stand from the front. It is a graph which shows the relationship between a load and a mill stretch. It is a flowchart which shows the calculation method of mill stretch.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  The intermediate roll bending force can usually be applied to several tens of tons / chock (several hundreds kN / chock), and the loaded roll bending force is a force that elastically deforms the entire rolling mill via the load cell. FIG. 1 shows the result of measuring the mill stretch change when the intermediate roll bending force is applied (plate thickness change). All rolling conditions including the rolling position were fixed, and only the intermediate roll bending force was changed. The intermediate roll bending force is initially 10 ton / check (98 kN / chock) and is increased to 70 tonf / chock (686 kN / chock). It was confirmed that the plate thickness changed by about 150 μm. It can also be seen from FIG. 1 that the relationship between the intermediate roll bending force and the plate thickness change amount is not completely linear. If the influence of the intermediate roll bending force is not taken into account when estimating the mill stretch, all of this becomes a plate thickness estimation error, so it can be confirmed that the influence of the intermediate roll bending force is considered in the mill stretch estimation. It was. The relationship between the intermediate roll bending force and the plate thickness change naturally varies depending on the rolling mill, and also varies depending on the rolling conditions, but for each rolling mill, the relationship as shown in FIG. It can be approximated as a polynomial such as a quadratic or cubic function of the roll bending force and used for mill stretch estimation. Of course, rolling conditions such as load and intermediate roll shift amount may be included in the polynomial. In addition, approximation may be performed using a linear expression, an exponential function, or a trigonometric function instead of a polynomial expression. The value of the intermediate roll bending force according to these formulas can be added to the rolling mill without the intermediate roll bender or the mill stretch amount used when the influence of the intermediate roll bending force was not taken into consideration.

  The above is a method that simply incorporates the influence of the intermediate roll bending force on the mill stretch into the mill stretch estimation, but if possible, it is better to estimate it using a theoretical or pseudo-theoretical model that considers rolling conditions. . This is because the amount of influence of the intermediate roll bending force on the mill stretch varies depending on the rolling conditions as described above. Accordingly, a mill stretch estimation model that takes into account the intermediate roll bending force and can be estimated even when rolling conditions change will be described below with reference to the drawings.

  FIG. 2 is an explanatory diagram of a UC mill 4-stand cold tandem rolling mill 1 provided with an intermediate roll bender having an asymmetrical intermediate roll bending force action point for performing plate rolling. The cold tandem rolling mill 1 is constituted by four rolling stands 10 (10a to 10d from the left in FIG. 2) of the same type, and the rolling material S passes through and is rolled in the order of 10a to 10d. The rolling rolls of each rolling stand 10 are an upper work roll 20 and a lower work roll 21 provided above and below the rolling material S, and an upper middle provided adjacent to the upper side of the upper work roll 20 and the lower side of the lower work roll 21. The roll 22, the lower intermediate roll 23, and three types of rolls, an upper backup roll 24 and a lower backup roll 25 provided adjacent to the upper side of the upper intermediate roll 22 and the lower side of the lower intermediate roll 23 are configured.

  Moreover, in FIG. 3, the explanatory view which looked at the rolling stand 10 from the front is shown. An upper work roll 20 and a lower work roll 21 provided above and below the rolled material S; an upper intermediate roll 22 and a lower intermediate roll 23 provided adjacent to the upper side of the upper work roll 20 and the lower side of the lower work roll 21; An upper backup roll 24 and a lower backup roll 25 provided adjacent to the upper side of the upper intermediate roll 22 and the lower side of the lower intermediate roll 23 are configured as shown in FIG. The intermediate roll is used by shifting according to the width of the rolled material, and FIG. 3 shows the shifted state. In addition, about the upper work roll 20, the lower work roll 21, the upper backup roll 24, and the lower backup roll 25, the state comprised respectively symmetrically with respect to the centerline X of the width direction of the cold tandem rolling mill 1 is shown. ing. Of course, in the rolling mill having the work roll shift function, the center axis of the body length of the work rolls 20 and 21 may not coincide with the center line X. The current work roll bending force action point is only a symmetric rolling mill where the midpoint of the work roll body width direction and the midpoint of the bending force action point coincide with each other. When an asymmetric rolling mill is developed, it is a matter of course that this point can be taken into consideration if it is handled in the same manner as described below, as shown for the intermediate roll bending force. Furthermore, the rolled material is not always in the center of the rolling mill during rolling. It should be noted that the center line in the width direction of the rolled material may not coincide with the center axis of the rolling mill. Since the thickness of the sheet is usually the thickness of the central axis portion of the rolled material, the point where the center of the rolled material does not coincide with the central axis of the rolling mill, as already considered in Patent Document 1, is rolled. The elastic deformation amount of the machine may be considered by the deformation amount of the center line portion of the rolled material. The influence is taken into consideration in the later-described expressions (3) and (7).

Further, as shown in FIG. 3, work roll bending forces f1 and f2 are applied to the left and right sides of the upper work roll 20 by a roll bender (not shown), and the upper intermediate roll 22 is intermediated by a roll bender (not shown). Roll bending forces f3 and f4 are acting. The center A1 of the body length of the upper intermediate roll 22 in the roll width direction does not coincide with the midpoint p3 in the roll width direction of the action points p1 and p2 of the intermediate roll bending forces f3 and f4. That is, when both f3 and f4 are equal in upward force, the moment distribution due to the intermediate roll bending forces f3 and f4 is asymmetric with respect to the rolling stand 10 when viewed from the center A1. Has occurred.
Also, different forces f3 and f4 may be applied. At this time, it is a matter of course that there may be a ratio of f3 and f4 that can apply the moment distribution symmetrically.

Up to this point, we have described a left-right asymmetric rolling mill in which the midpoint of the intermediate roll bending force action point does not coincide with the center of the intermediate roll cylinder length, but it is calculated using the same distance assuming that the intermediate roll bending force action point is symmetrical. Needless to say, it can be calculated as a symmetrical rolling mill. That is, although the formula for the mil stretch calculation is described below, it is sufficient to solve the formula as symmetrical in that. Further, since the lower roll group is handled in the same manner as the upper roll group, the description thereof is omitted.

  On the other hand, as shown in FIG. 2, a load cell 30 for measuring a load is installed on the upper backup roll 24, and a hydraulic reduction device 31 is installed below the lower backup roll 25. Further, a mill motor 32 that drives the lower work roll 21 is attached to the lower work roll 21. Furthermore, a speedometer 40 and a plate thickness meter 41 are installed before and after each rolling stand 10 (10a to 10d), and the speed and plate thickness of the rolling material S between the rolling stands 10 (10a to 10d). Is measured. In FIG. 2, a thickness gauge 41 is installed before and after the rolling stand 10a and at the rear of the rolling stand 10d.

In the cold tandem rolling mill 1 configured as described above, the rolled material S is rolled, and the thickness of the rolled material S is controlled by each rolling stand 10 (10a to 10d) during rolling. This plate thickness control will be described below with reference to FIG. In FIG. 5 and below, WR represents a work roll, IMR represents an intermediate roll, and BUR represents a backup roll.

As described in Patent Document 1 (Japanese Patent Laid-Open No. 60-30508), the load distribution in a rolling mill is linearly approximated, and the load distribution is obtained by solving the balance condition equation of the rolling load and the balance equation of the moment. Can do. The load distribution in the contact area can be calculated in the same way between WR / IMR and IMR / BUR. The roll flatness in the roll contact area is obtained from the load distribution. The flat calculation between the work roll and the material is also disclosed in Patent Document 1. Further, the deflection amount of the roll can be solved as a beam deflection problem, and the deflection during the actual rolling can be obtained by correcting it. Patent Document 1 describes that the roll deformation amount is obtained by adding the roll flatness and the deflection amount, and the mill stretch amount is obtained by adding deformation (housing / deformation deformation) other than the roll system. Has been. In the present invention, the roll deformation amount is calculated with a term that needs to consider the influence of the intermediate roll bending force and a term that does not need to consider the influence of the intermediate roll bending force. The amount of mill stretch is obtained by adding the amount of deformation other than the roll system (deformation of the housing / rolling system). The term that needs to consider the influence of the intermediate roll bending force is the IMR / BUR contact area, and there is no need to consider in the deformation other than the WR / IMR contact area / WR / material and the roll system. The deformation of the housing / rolling system is identified in advance by extracting the deformation of the roll system at the time of the kiss roll from the relationship between the load and the mill stretch by the kiss roll tightening test.

Therefore, as shown in FIG. 3, a cold tandem having an upper intermediate roll 22 and a lower intermediate roll 23 in which the middle point of the intermediate roll bending force acting point position may not be coincident with the center of the roll body length may be asymmetrical. In order to apply the method described in Patent Document 1 to the rolling mill 1, it is necessary to consider the influence of the intermediate roll bending force acting on the asymmetric upper and lower intermediate rolls 22 and 23.

On the other hand, FIG. 4 is a graph showing the relationship between the load and the mill stretch when a rolling load is applied during rolling in the rolling mill. The rolling mill is elastically deformed when a rolling load is applied during rolling, and the mill stretch, which is this elastic deformation, is strictly nonlinear. In the plate thickness estimation model described in Patent Document 2, the mill stretch is estimated in consideration of this nonlinearity. That is, the mill stretch is first separated into roll-type deformation and other deformations. The roll system deformation is classified into a term due to roll flat deformation and a term due to roll deflection deformation, and each is calculated. As for the rolls in contact with each other, the deformation can be obtained by obtaining the load distribution by solving the force equilibrium condition equation and the moment equilibrium condition equation simultaneously assuming that the load distribution is a straight line. Further, other deformations are identified in advance by extracting the deformation of the roll system at the time of the kiss roll from the relationship between the load by the kiss roll tightening test and the mill stretch. Mill stretch is calculated | required by superimposing the deformation | transformation of the roll type | system | group at the time of each said coil rolling on this other deformation | transformation.

ここで上記Ｐ_ＢＩ(ｘ)は、以下に示す式（２）：圧延荷重Ｐ（ｔｏｎｆ）との平衡条件式および式（３）：モーメントの平衡条件式を満足しなければならない。

なお、上記式（１）〜（３）において、ｘ_ＢＩはバックアップロール〜中間ロール接触領域の中心のＸ座標、Ｆ_Ｗ−Ｗ（ｔｏｎｆ／ｃｈｏｃｋ）はワークサイド側のワークロールベンディング力、Ｆ_Ｗ−Ｄ（ｔｏｎｆ／ｃｈｏｃｋ）はドライブサイド側のワークロールベンディング力、Ｆ_Ｉ−Ｗ（ｔｏｎ／ｃｈｏｃｋ）はワークサイド側の中間ロールベンディング力、Ｆ_Ｉ−Ｄ（ｔｏｎ／ｃｈｏｃｋ）はドライブサイド側の中間ロールベンディング力、ｌ_ＢＩはバックアップロール〜中間ロール接触領域の長さ（ｍｍ）、Ｘ_Ｃは圧延材中心のＸ座標、ａ_Ｗはワークロールベンディング力作用点間距離（ｍｍ）、ａ_Ｉ−Ｗは中間ロール胴長中心からワークサイド側の中間ロールベンディング力作用点までの距離（ｍｍ）、ａ_Ｉ−Ｄは中間ロール胴長中心からドライブサイド側の中間ロールベンディング力作用点までの距離（ｍｍ）、Ｓ_Ｉは中間ロールシフト量（ｍｍ）である。中間ロールベンダー作用点の左右非対称性がない圧延機であれば、この式でａ_Ｉ−Ｗとａ_Ｉ−Ｄの値を同じにすればよい。すなわち、請求項２のような左右非対称性のない圧延機でも、請求項３のような左右非対称性がある圧延機でも上記式にて計算できる。 Hereafter, the term which needs to consider the influence of intermediate roll bending force will be explained. The fact that the intermediate roll bending force needs to be taken into account means that it is also necessary to take into account the left-right asymmetry of the intermediate roll bending force acting point. In consideration of the left-right asymmetry of the intermediate roll bending force acting point described above, assuming that the contact load between the intermediate roll and the backup roll is linear, the contact load P _BI (x) (tonf / m between the intermediate roll and the backup roll) ) Can be expressed as the following equation (1).

Here, P _BI (x) must satisfy the following formula (2): equilibrium condition formula with rolling load P (tonf) and formula (3): moment equilibrium condition formula.

In the above formulas (1) to (3), x _BI is the X coordinate of the center of the contact area between the backup roll and the intermediate roll, F _W−W (tonf / check) is the work roll bending force on the work side, and F _{W -D} (tonf / chock) is the work roll bending force on the drive side, FI _-W (ton / chock) is the intermediate roll bending force on the work side, and FI _-D (ton / chock) is the drive side bending force. Intermediate roll bending force, l _BI is the length of the contact area between the backup roll and the intermediate roll (mm), X _C is the X coordinate of the center of the rolled material, a _W is the distance between the work roll bending force acting points (mm), a _{I− W} is the distance from the intermediate roll barrel length center to the intermediate roll bending force acting point of the work-side (mm), a _I-D is Distance from between the roll barrel length center to the intermediate roll bending force acting point of drive-side (mm), S _I is an intermediate roll shift amount (mm). If the rolling mill has no left-right asymmetry of the intermediate roll bender acting point, the values of a _I-W and a _I-D may be made the same in this equation. In other words, even a rolling mill with no left-right asymmetry as in claim 2 or a rolling mill with left-right asymmetry as in claim 3 can be calculated by the above formula.

たわみについては特許文献１に開示されている通り、梁のたわみとして計算した上で補正を加えることにより求めることができる。 By substituting equation (1) into the above equations (2) and (3) and solving the substituted A and B binary linear equations, the contact load P _BI (x) (between the intermediate roll and the backup roll) (tonf / m) load distribution is obtained. Then, showing the obtained _P BI (x) to the following equation (4) so that the value of roll flattening is obtained by substituting the _{P BI} (Expression of Patent Document 1 (36)).

As disclosed in Patent Document 1, the deflection can be obtained by calculating the deflection of the beam and adding correction.

ここで、ｌ_ＩＷは中間ロール〜ワークロール接触領域の長さ（ｍｍ）、Ｐ_ＩＷ(ｘ)はワークロールと中間ロール間の接触荷重（ｔｏｎｆ／ｍ）、であり、このほかは式（１）〜（３）と同じである。 From here, the term which does not consider the influence of intermediate roll bending force is demonstrated. The fact that the intermediate roll bending force does not need to be considered means that the left-right asymmetry of the intermediate roll bending force acting point need not be considered. When considering the contact load P _IW (x) (tonf / m) between the work roll and the intermediate roll, it is not necessary to consider the influence of the intermediate roll bending force. Therefore, the intermediate roll bending force is expressed by the above formulas (2) and (3). It is the form which removed the influence of. In P _BI (x), I represents an intermediate roll and B represents a backup roll. Therefore, if B in the formula is changed to W (meaning work roll), the contact load between the work roll and the intermediate roll is obtained. These newly considered equations do not include the effects of intermediate roll bending forces. That is, it can be said that it is not necessary to consider the influence of intermediate roll bending force. If the items with and without the influence of the intermediate roll bending force are separated from the formula of Patent Document 1 and the influence of the intermediate roll bending force is added only to the affected terms, the intermediate roll bending force is considered. The completed mill stretch formula is completed. The mill stretch calculation formula is described as Formula (5)-Formula (7) below.

Here, l _IW is the length from the intermediate roll to the work roll contact area (mm), and P _IW (x) is the contact load (tonf / m) between the work roll and the intermediate roll. ) To (3).

Substituting Equation (5) into Equations (6) and (7) above, and solving the substituted linear equations D and E, the contact load P _IW (x) (between the intermediate roll and the work roll) (tonf / m) load distribution is obtained. Based on this contact load, roll flatness and deflection as terms that do not require consideration of the influence of the intermediate roll bending force are required.

As described above, in the mill stretch calculation method described in Patent Document 1, the above method that considers the left-right asymmetry of the intermediate roll bending force in the balance formula between the load and the moment is also incorporated into other balance formulas. Roll flatness and deflection are required for the terms that need to consider the effect of roll bending force and the terms that do not need to consider the effect of intermediate roll bending force. The amount of stretch can be calculated. According to this method, a highly accurate plate thickness control method by a mill stretch method that can be applied to a UC mill provided with an intermediate roll bender having a left-right asymmetric force acting point used in recent years is provided. If there is no asymmetry of the intermediate roll bender action point, it can be considered as a singular point of the condition considering the left-right asymmetry as described above. Regardless, it can be calculated.

  Next, handling of the load when considering roll deformation during rolling will be described. The rolling load depends on the deformation of the roll, and conversely, the roll deformation cannot be obtained unless the rolling load is known. Therefore, the load distribution cannot usually be obtained unless convergence calculation is performed. However, even if convergence calculation is performed during rolling, it is impossible in terms of time to obtain the rolling load distribution and the deformation of the rolling mill that change from moment to moment. Therefore, as disclosed in Patent Document 1, it is effective to obtain a roll deformation assuming that the load distribution is a straight line. By assuming the rolling load distribution to be a straight line, the amount of deflection of each roll can also be estimated, and by adding it to the effects other than the roll system, the amount of mill stretch at the time of a certain rolling load is finally obtained. It is. The influence of the intermediate roll bender can be incorporated into the load distribution by adding to the load distribution. If this method is used, the amount of mill stretch can be obtained online.

  As mentioned above, although an example of embodiment of this invention was demonstrated, this invention is not limited to the form of illustration. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

Example 1
In order to confirm the necessity of the plate thickness control method according to the present invention, the following verification was performed as Example 1 assuming a UC mill and a new UC mill. The only difference between the UC mill and the new UC mill is that the position of the working point of the intermediate roll bender of the new UC mill is asymmetrical, and the same rolling mill was used for all parts other than the asymmetry of the intermediate roll. . In each case, equal work roll bending force and intermediate roll bending force were applied to tighten the kiss roll, and the relationship between rolling load and mill stretch was measured.

  Here, the conditions for performing the verification were a work roll bending force of 5 ton / chock (49 kN / chock), an intermediate roll bending force of 10 ton / chock (98 kN / chock), and an intermediate roll shift of 150 mm. The roll diameter and body length were 600 mm and 600 mm for the backup roll, 450 mm and 600 mm for the intermediate roll, and 250 mm and 600 mm for the work roll, and the upper and lower roll dimensions of each roll were the same. The left-right difference (the difference between the distance from the center of the roll cylinder length to the work side side action point position and the distance from the drive side side action point position) of the intermediate roll bender action point of the new UC mill was 160 mm.

  When the kiss roll is tightened under the above conditions and the rolling load is set to the maximum load, it is confirmed that the tightening position is shifted by 18 μm between the UC mill condition and the new UC mill condition. It was done. Here, since the verification was performed under the same conditions except for the condition of the intermediate roll, it was confirmed that the displacement of the tightening position was caused by the left-right asymmetry of the intermediate roll. Since the difference as described above is generated only by tightening the kiss roll, it is easily estimated that the estimation error when there is a plate during rolling is of the above level or more.

(Example 2)
Next, Example 2 for confirming the effect of the plate thickness control method according to the present invention was performed. In Example 2, a rolling experiment was performed using a new UC mill 4 stand cold tandem rolling mill having the structure shown in FIG. The load estimation method of claim 3 was used for the plate thickness estimation calculation.

  All four stands were of the same type, and the roll diameter was 1250-1291 mm for the backup roll diameter, 491-503 mm for the intermediate roll diameter, and 425-426 mm for the work roll diameter. About the work roll, there was almost no difference in the diameter of the upper and lower rolls, and it was within 0.3 mm. The work roll bending force was about 15 tonf / check (147 kN / chock), and the intermediate roll bending force was about 45 tonf / chock (441 kN / chock). The rolling load and bending force were measured at 10 ms. In the cold tandem rolling mill used in Example 2, the intermediate roll bender was asymmetrical, and the distance difference between the intermediate roll bender force action points was 230 mm.

  Under the conditions described above, 15 coils having a width of 1210 mm to 600 mm were rolled, and the thickness measured by the thickness gauge on the first stand exit side of the cold tandem rolling mill and the thickness control method according to the present invention were obtained. The estimated thickness was compared.

As the comparison result, the estimated thickness that does not consider intermediate roll bender as compared to measuring thickness, that there is an average 3.8% of the error is confirmed (Formula 2,3 F _I-W, F _{ID is set} to 0). In addition, if the influence of the intermediate roll bender is taken into consideration (left-right asymmetry is not taken into account. The average value is used for the distance to the left and right action points), the estimated thickness is an error of 1.2% on average compared to the measured thickness. It was confirmed that there is.

On the other hand, when the estimated plate thickness in consideration of the left-right asymmetry of the intermediate roll was compared with the measured plate thickness, the average error was 0.2%. From this result, by considering the intermediate roll bender by the plate thickness control method according to the present invention and performing the plate thickness control in consideration of the left-right asymmetry of the intermediate roll bender action point, the plate thickness control with very small error is performed. It became clear that it was possible to do.
Finally, rolling was performed using an intermediate roll having an intermediate roll bender acting point that is symmetrical, and the thickness estimation accuracy was confirmed in the same manner as described above. When the intermediate roll bender was not considered, there was an average error of 3.9%, but when considered, the error was 0.18%. It was confirmed that this mill stretch estimation model can estimate the thickness sufficiently even when the intermediate roll is symmetrical.

  The present invention relates to a rolling mill having an intermediate roll bender, and the midpoint in the roll width direction of the point of action of the intermediate roll bender force acting on both sides of the intermediate roll coincides with the midpoint of the intermediate roll body length in the roll width direction. In a rolling mill equipped with an intermediate roll, in some cases, the mill stretch is estimated, and the present invention can be applied to a plate thickness control method that estimates and controls the plate thickness based on the estimated mill stretch.

DESCRIPTION OF SYMBOLS 1 ... Cold tandem rolling mill 10 ... Rolling stand 20 ... Upper work roll 21 ... Lower work roll 22 ... Upper intermediate roll 23 ... Lower intermediate roll 24 ... Upper backup roll 25 ... Lower backup roll 30 ... Load cell 31 ... Hydraulic reduction device 32 ... Mill motor 40 ... Speedometer 41 ... Thickness gauge

Claims (4)

A sheet thickness control method for controlling a sheet thickness by estimating a mill stretch with a rolling mill having an intermediate roll bender,
A sheet thickness control method characterized by adding the influence of the intermediate roll bending force on the mill stretch as a polynomial function of the intermediate roll bending force to a mill stretch model formula that does not consider the intermediate roll bending force. The mill stretch is separated into a roll-type deformation and a non-roll-type deformation by a rolling mill having an intermediate roll bender, and the non-roll-type deformation is identified in advance through kiss roll tightening, and the roll-type deformation during rolling is identified. A plate thickness control method for controlling the plate thickness by estimating with the method of adding,
The estimation of the mill stretch is divided into a term that should consider the influence of the intermediate roll bending force and a term that does not need to be considered, a calculation amount of the influence of the intermediate roll bending force, and a term that does not need to consider the influence of the intermediate roll bending force. The thickness control method is performed by superimposing the influence amount of the intermediate roll bending force on the influence amount of the mill stretch. The estimation of the mill stretch is divided into a term that should consider the roll width direction asymmetry of the intermediate roll bending force and a term that does not need to be considered, and the middle point of the intermediate roll body length in the roll width direction and both sides of the intermediate roll The amount of influence on the mill stretch that takes into account the left-right asymmetry of the point of action of the intermediate roll bending force that acts on the roll is calculated. The plate | board thickness control method of Claim 2 performed by superimposing. The roll deformation contribution of the backup roll, intermediate roll and work roll, and the width direction distribution of the contact load between the backup roll, intermediate roll and work roll, the influence of the intermediate roll bending force, or the intermediate roll bending force action point In consideration of the effect of asymmetry in the width direction of the backup roll, the intermediate roll and the backup roll, the intermediate roll, and the work roll And obtaining the flat deformation of the work roll,
Superimposing on the basis of the integral average straight line related to the contact area with each adjacent roll of the backup roll and the work roll to obtain the sum of the deflection of the backup roll, the intermediate roll and the work roll,
The plate | board thickness control method in any one of Claim 2 or 3 which considers the influence of intermediate | middle roll bending force by the method of superimposing the said flat deformation and the said bending | deflection.

Images