JPH07227611A - Board wave shape control method for continuous hot rolling mill - Google Patents

Abstract

PURPOSE:To form board wave shape satisfactorily in hot rolling by a continuous hat rolling mill for a metallic strip consisting of plural stands. CONSTITUTION:The continuous hot rolling mill for the metallic strip consisting of the plural stands is provided with work roll vendors 4a-4g. The change of the output side board thickness of each stand, each parameter value of gage meter type, the expansion quantity of a roll center part, roll expansion quantity distribution in a roll axial direction, the board thickness and board crown of each stand output side are computed from board thickness measured values by board thickness meters 5, 6 provided on at least one or more stand output sides, the work roll peripheral speed value of each stand, a rolling load measured value, a roll gap measured value, and a roll bending force measured value. The bending quantity of the work roll bendors can be corrected so as to correct the change of the board wave generated by those change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a plate wave shape of a hot continuous rolling mill having a plurality of stands, which performs hot continuous rolling of a metal strip while maintaining a good plate wave shape.

[0002]

2. Description of the Related Art When rolling with a hot continuous rolling mill,
It has been conventionally known that in the longitudinal direction of the steel strip, the plate thickness on the outlet side of each stand may fluctuate in the widthwise central part and the plate edge part, and shape defects such as ear waves and medium waves may occur. There is.

As a cause of such a variation in the plate thickness, temperature variations occur in the longitudinal direction and the width direction of the steel strip, which changes the deformation resistance of the material to be rolled, so that the rolling pressure in the roll bite is changed. The distribution is changed, and it is balanced with the deflection of the work rolls so that the rolling progresses, and as a result, the plate thickness on the delivery side of each stand is changed in the longitudinal direction and the width direction.

2 (a) to 2 (c) are schematic perspective views showing changes in plate shape depending on rolling conditions. Figure 2 (a) ~ (c)
In, C is entry side crown for each stand, H _C is the thickness of the inlet side width direction center portion, H _E is the thickness of the inlet-side end portion in the width direction, c
Is the crown of the outlet side of each stand, h _C is the plate thickness of the central portion in the outlet width direction, and h _E is the plate thickness of the end portion in the outlet width direction. As shown in FIG. 2 (a), the plate thickness fluctuations that occur during rolling are the plate crown C on the entrance side, the plate thickness H _C at the widthwise central portion and the plate crown c at the exit side, and the widthwise central portion of each stand. Depending on the relationship with the plate thickness h _C , the shape becomes an ear wave shown in Fig. 2 (b) or a middle stretched shape shown in Fig. 2 (c). This causes cracks and folds in the rolled material, leading to deterioration in quality.

Therefore, as a method for solving such a defective shape, a method described in Japanese Patent Application Laid-Open No. 4-100624 has been proposed. In this method, a plate thickness detector is installed between at least one stand to correct the reduction (correction of gap between work rolls).
The work roll bender is operated according to the amount of change that the load gives to the plate crown. Further, in the method described in JP-A-60-223605, a shape detector and a crown detector installed on the exit side of the final stand are used to
The last stand and the stand immediately before the last stand are used for control.

[0006]

However, the above-mentioned prior art has the following problems. As another cause of causing such plate thickness fluctuation, heat conduction is performed to the work roll by the material to be rolled during rolling, the work roll is expanded by the heat, and particularly in the roll axial direction, There is a large temperature difference between the part that is in contact and the part that is not in contact, and the difference in the amount of expansion in the axial direction of the roll is also large.As a result, a gap difference occurs in the axial direction of each stand work roll, and The thickness of the rolled material on one side may vary in the width direction.

In the above-mentioned prior art method, the thermal expansion of the work roll which changes during the rolling is not taken into consideration. Further, in the method described in JP-A-4-100624, the plate thickness on the delivery side of the final stand is not detected.
In the method described in Japanese Patent Publication No. 05, no compensation is made to improve the plate wave shape for the stands other than the final stud and the stand immediately before it.

The present invention corrects the plate crown on the stand-out side of each stand by the work roll bender during rolling to make the ratio of the plate thickness and the plate-crown on the stand-out side constant so that the plate wave shape is obtained. For the purpose of good control, in particular, based on the measurement results of the stand outlet side thickness gauges installed at least at one or more places on the stand outlet side, the sheet thickness fluctuation on each stand outlet side during rolling and the thermal expansion amount of the work roll can be determined. The work roll bender operation amount of each stand is determined and the plate wave shape is controlled by combining the calculation results and the results of calculating the plate crown fluctuation amount due to the load fluctuation during rolling.

[0009]

The above-mentioned problems can be solved by the following means. In a metal strip hot rolling mill consisting of a plurality of stands having a work roll bender, at least one sheet thickness measurement value provided by a thickness gauge provided on the stand exit side and the measurement value of the work roll peripheral speed at each stand Calculate the stand-out side plate thickness using, and the calculated stand-out side plate thickness, the rolling load measurement value of each stand, the roll gap measurement value and the roll bending force measurement value, each parameter of the gauge meter formula The roll expansion amount of the roll central portion is calculated to calculate the distribution of the roll expansion amount in the roll axial direction from the calculated parameters and the roll expansion amount of the roll central portion, and the calculated roll expansion amount. From the roll expansion change amount obtained from the measured rolling load change amount, work roll bending force change amount, input side plate crown change amount It calculates the amount of change in each stand outlet side of the plate thickness and the plate crown during the rolling,
Corresponding to these changes, the amount of change in bending force of the work roll bender of each stand to keep the ratio of plate thickness and plate crown constant is calculated, and the bending force is corrected. Method for controlling plate wave shape of continuous rolling mill.

[0010]

In the hot continuous rolling mill, in order to control the plate wave shape on the stand-out side, it is necessary to keep the ratio of the plate thickness and the plate crown on the stand-out side constant. For that purpose, it is indispensable to know the variation of the plate thickness and the variation of the plate crown with high accuracy.

In order to achieve the above object, at least one plate thickness gauge is provided on the stand-out side, and the measured values of these plate thickness gauges, the work roll peripheral speed measurement value of each stand, the rolling load measurement value, From the roll gap measurement value and the roll bending force measurement value, the stand outlet side plate thickness, each gauge meter parameter value, the roll expansion amount in the center of the roll, and the roll expansion amount distribution in the roll axial direction are calculated. Next, from the parameters obtained in the above calculation and the roll expansion amount at the center of the roll, No. The amount of change in the ratio b _i (b _i = c _i / h _ci ) between the plate thickness h _ci and the plate crown c _i on the stand side of the i-stand is calculated, and the amount of change of each stand corresponding to the change amount is calculated in order to cancel the change. In combination with a device for calculating the operation amount of the work roll bender, the plate wave shape is controlled by correcting the work roll bending force of the work roll bender device in each stand so that the plate crown ratio b _i becomes constant. .

A method for calculating the correction amount of the work roll bending force of each stand with the above configuration will be described below. No. during rolling The plate thickness h _ci of the widthwise central part on the stand side of the i stand is No. j Thickness measurement value h _cj ^{* at the} center in the width direction measured by a thickness gauge installed on the stand exit side
It is generally known that, due to the relationship of constant volume velocity, the following equation (1) enables accurate calculation.

H _ci = {(v _Rj (1 + f _j )) / (v _Ri (1 + f _i ))} _{h cj} ^* (1) where the meanings of the symbols are as follows. v _Ri : Work roll peripheral speed at No.i stand v _Rj : Work roll peripheral speed at No.j stand f _i : Advance rate at No. _i stand f _j : Advance rate at No. _j stand

The plate thickness calculated by the equation (1) is generally
It is called low thickness and can be measured v_Ri, V_RjAnd measured or known
F that can be calculated from the Simms formula of_i, F_jCan be calculated by
Is. It should be noted that the calculation value of the formula (1) is calculated by n plate thickness gauges.
But h_cj ¹, H_cj ², ─, h_cj ⁿ When n pieces are obtained,
Primary combination may be performed with an appropriate weighting coefficient.

[0015]

[Equation 1]

The meanings of the symbols are as follows. h _ci ^k : No. calculated from equation (1) from the measured values of the k thickness gauges.
Plate thickness at outlet side of i stand w _hi (k): Weighting coefficient for calculating plate thickness at outlet side of Noi stand by kth thickness gauge

However,

[0018]

[Equation 2]

When the stand outgoing side plate thickness during rolling is obtained by the calculation of (2), other known data during rolling measured at the same time as the calculation is used to calculate the known gauge meter formula of the following (3). By using, it is possible to calculate the amount of thermal expansion of the central portion of the work roll in the axial direction. h _Gi (t) = S _i (t) + P _i (t) / K _i + P _Bi (t) / K _Bi + α _i + C _RHi (t) (3)

The meanings of the symbols are as follows. t: Time after rolling of the material to be rolled h _Gi (t): Thickness of the No.i stand at the time t in the widthwise center of the stand side S _i (t): No.i stand gap at the time t Actual (measured value) P _i (t): No.i stand rolling load actual result (measured value) at time t P _Bi (t): No.i stand work roll bending force actual result (measured value) C _RHi ( t): Thermal expansion of No.i stand work roll center at time t K _i : Mill stiffness coefficient of No. _i stand K _Bi : Bender stiffness coefficient of No. _i stand α _i : Constant term

FIG. 3 is a diagram showing a state in which the amount of thermal expansion of the central portion of the roll changes depending on the rolling time.
C _RHi (t) is generally a function of the behavior for t as shown in FIG. Therefore, C _RHi (t) is appropriately approximated in a linear form with respect to t as shown in the following equation (4). C _RHi (t) = A _i · t ^1/2 (4) Here, the meanings of the symbols are as follows. A _i : constant

When C _RHi (t) is expressed by a linear function as shown in equation (4) and is substituted into equation (3), equation (3) yields S _i (t) and P _i ( It can be expressed in a linear form with t) and P _Bi (t) as variables.

Therefore, during rolling, every Δt time period
_Assuming that h _ci calculated by equation (2) and h _Gi (t) represented by equation (3) are equal, K _i , K _Bi , α _{i in} equation (3) and A in equation (4). _i can be accurately estimated each time the number of calculations in the period of Δt time is increased. The estimation method uses a parameter recursive estimation method (system identification method) typified by a known recursive least squares method, and if the period Δt is appropriately determined based on the sampling theorem or the like, the accuracy is practically sufficient. _Can estimate A _{i and the} like. As a result, the thermal expansion amount of the work roll central portion in the equation (4) can be calculated for each stand.

When the thermal expansion amount of the central portion of the work roll of the equation (4) is estimated, it is necessary to know the thermal expansion amount distribution of the work roll in the roll axial direction in order to calculate the plate crown amount of each stand. . For that purpose, it is necessary to solve the heat conduction equation of the work roll under various boundary conditions in the contact part of the plate material and the roll, the affected part of the work roll cooling water, and the part to be air-cooled, but it requires a huge calculation time. Not only that, but the accuracy is not sufficient enough to spend time for the calculation.

Therefore, in the present invention, the thermal expansion amount can be accurately estimated from the formula (4) at the center of the work roll. At the end of the work roll in the axial direction, due to the work roll cooling water effect and the heat capacity of the work roll itself,
The amount of thermal expansion may be regarded as none. Total amount of heat input from the plate material (mainly the contact time between the plate material and the work roll and the contact width in the roll axial direction)
Thus, the thermal expansion distribution of the work roll is determined. From the general knowledge that the contact time and contact width of the work roll and the plate material are taken into consideration, the center of the work roll and the end in the axial direction are interpolated by a free curve (cubic spline curve) to determine the thermal expansion distribution. Decided to get.

FIG. 4 is a diagram showing a profile of the amount of thermal expansion in the roll axis direction. In Fig. 4, [P] ₁ is the position vector of the point that indicates the amount of thermal expansion in the center, [T] ₁ is the tangent vector of the point that indicates the amount of thermal expansion in the center, and [P] ₂ is the end of the work roll axial direction. Vector of the point indicating the amount of thermal expansion of the part, [T] ₂ is the tangent vector of the point indicating the amount of thermal expansion at the end of the work roll axial direction, [C] _W (u) is the distribution vector of the amount of thermal expansion, and u Is a parameter (0 ≦ u ≦ 1), and L is a roll width. Regarding the work roll axial direction x shown in FIG. 4, the position vector [P] ₁ , the tangent vector [T] _{1 of the} point indicating the thermal expansion amount of the central portion, and the point indicating the thermal expansion amount of the end portion of the work roll axial direction By interpolating between the position vector [P] ₂ and the tangent vector [T] ₂ using the parameter u, the distribution vector of thermal expansion [C] _W (u)
Is described by the following equation.

[C] _W (u) = (2 · [P] _1-2 − [P] ₂ + [T] ₁ + [T] ₂ ) · u ³ + (− 3 · [P] ₁ + 3 · _{[P] 2 -2 · [T} ] 1 - [T] 2) · u 2 + [T] 1 · u + [P] 2 ─ (5) (0 ≦ u ≦ 1) here, in equation (4) Using the _calculated C _RHi (t),

[0028]

[Equation 3]

[0029]

FIG. 5 shows the time after changing the work rolls and the work time.
Width of contact between roll and plate material and center of roll
It is a figure which shows the relationship with the amount of thermal expansion. In FIG. 5, B₁
~ B _nIs the strip width of each rolled material, T₁~ T_nIs the rolling of each rolled material
Time, T_H1~ T_H5Is the non-rolling time between rolling of each rolled material
is there.

In equation (6), T _1x and T _2x are determined by the time and width of contact between the work roll and the plate material. As shown in FIG. Assuming that the roll and the plate material are in contact with each other during rolling, it can be described by the following equation.

[0032]

[Equation 4]

[0033]

[Equation 5]

Here, a ₁ , b ₁ , c ₁ , a ₂ , b ₂ ,
c ₂ is a constant. FIG. 6 is a diagram showing the result of calculation by actually adjusting a ₁ , b ₁ , c ₁ , a ₂ , b ₂ , c ₂ from the measurement data of the actual machine. In FIG. 6, L is the roll width. The calculation conditions based on the measurement data are as shown in Table 1. The constant values used are as follows. a ₁ = 0.0002 b ₁ = 900.0 c ₁ = 1.5 a ₂ = 0.0001 b ₂ = 900.0 c ₂ = 1.7

[0035]

[Table 1]

FIG. 6 shows a distribution of the amount of thermal expansion equivalent to the result of strictly solving the heat conduction equation of the roll, which can be used practically without any problem.

The variation of the plate crown on the stand-out side of each stand can be calculated by the following formula.

[0038]

[Equation 6]

The meanings of the symbols are as follows.

[0040]

[Equation 7]

[0041]

[Equation 8]

[0042]

[Equation 9]

ΔP _i : Change amount of rolling load based on the value at the start of rolling ΔP _Bi : Change amount of work roll bender force based on the value at the start of rolling ΔC _i-1 : Value at the start of rolling Amount of change in crown on the entry side ΔC _Ri : Amount of change in plate crown due to roll expansion calculated by equations (5) and (6) with reference to the value at the start of rolling ΔC _Ri = {C _Ri (t, 0 ) −C _Ri (t, B / 2)} − {C _Ri (t ₀ , 0)
-C _Ri (t ₀ , B / 2)} t ₀ : Time at the start of rolling B: Strip width Further, the strip thickness variation on the stand-out side of each stand can also be easily obtained from equations (1) and (2). .

To satisfactorily control the shape on the outlet side of each stand, as described above, C _i / h _Ci = (C _i ⁰ + ΔC _i ) / (h _Ci ⁰ + Δh _Ci )
= C _i ⁰ / h _Ci ⁰ = constant. Here, C _i ⁰ and h _Ci ⁰ are the plate crown target value and the plate thickness target value on the delivery side of each stand at the start of rolling, and are numerically calculated when calculating various set values for the rolling mill. .

From the above equation, since ΔC _i / Δh _Ci = C _i ⁰ / h _Ci ⁰ = constant, the equation (9) is substituted and the work roll bender operation amount is calculated by the following equation.

[0046]

[Equation 10]

By correcting the work roll bending force during rolling by the work roll bender operation amount calculated by the formula (10), the ratio of the plate crown to the plate thickness of the formula (10) can be controlled to be constant. it can. As a result, the shape of the plate wave on the exit side of each stand becomes good.

[0048]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of an apparatus for carrying out a method for controlling a plate wave shape of a hot continuous rolling mill according to the present invention, which comprises 7 stands. In FIG. 1, 1 is a material to be rolled, 2a
~ 2g is a work roll, 3a to 3g is a backup roll, 4a to 4g is a work roll bender, 5 and 6 are plate thickness gauges, 7 is a stand outlet side plate thickness calculation device, and 8 is a stand outlet side gauge meter type parameter. Sequential estimation calculation device, 9 is each stand roll expansion distribution calculation device, 10 is a plate thickness / plate crown change amount calculation device, and 11 is each stand bender operation amount calculation device.

In this embodiment, between the fourth and fifth stands and the seventh stand.
Plate thickness gauges 5 and 6 are installed on the stand-out side. Using the plate thickness measurement values measured by the plate thickness gauges 5 and 6 during rolling of the material to be rolled 1, each stand output side plate thickness calculation device 7 calculates each stand output side plate thickness from the constant volume rule.

From the calculated plate thickness, the actual rolling load of each stand during rolling, and the actual roll gap, each parameter of the gauge parameter formula is calculated by the parameter sequential calculation device 8
The parameters are successively estimated at, and the roll expansion amount at the center of the roll is sequentially calculated. As a result, each stand roll expansion distribution calculation device 9 calculates the distribution of the roll expansion amount in the roll axial direction, and the plate thickness / plate crown change amount calculation device 10
At, the plate thickness and the amount of plate crown change on the stand-out side of each stand during rolling can be obtained. Corresponding to this variation, the operation amount of each stand bender to keep the ratio of plate thickness and plate crown constant is
Calculated by each stand bender operation amount calculation device 11,
By correcting the bending force of the work roll bender of 4a to 4g, a good plate wave shape can be obtained.

[0051]

As described above, according to the present invention, the roll axial direction of the roll due to thermal expansion is based on the detection value of the plate thickness gauge installed at at least one location of the hot continuous rolling mill including a plurality of stands. Calculates the amount of expansion and the amount of change in plate thickness and plate crown on the stand exit side during rolling, and modifies the work roll bending force of the work roll bender for that stand so that the plate wave shape on the stand exit side does not change. By doing so, it becomes possible to manufacture a product having a good plate wave shape from the tip of the material to be rolled. The significance of the present invention having such effects is extremely remarkable.

[Brief description of drawings]

FIG. 1 is a schematic view showing a method for controlling a plate wave shape of a hot continuous rolling mill according to the present invention.

2A, 2B, and 2C are schematic perspective views showing changes in plate shape depending on rolling conditions.

FIG. 3 is a diagram showing a state in which the amount of thermal expansion of the central portion of the roll changes depending on the rolling time.

FIG. 4 is a diagram showing a profile of the amount of thermal expansion in the roll axis direction.

FIG. 5 is a diagram showing the relationship between the time after the work rolls are reassembled, the width of the work rolls in contact with the plate material, and the amount of thermal expansion of the roll central portion.

FIG. 6 is a diagram showing calculation results of thermal expansion in the roll axis direction based on measured data in an actual machine.

[Explanation of symbols]

 1 material to be rolled 2a to 2g work roll 4a to 4g work roll bender 5 and 6 plate thickness gauge 7 each stand output side plate thickness calculation device 9 each stand roll expansion distribution calculation device 10 plate thickness / plate crown change amount calculation device 11 each stand Bender manipulated variable calculator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B21B 37/18 B21B 37/12 BBM 8315-4E 111 B

Claims (1)

[Claims] 1. In a metal strip hot rolling mill comprising a plurality of stands having a work roll bender, a sheet thickness measurement value obtained by a sheet thickness gauge provided on at least one or more stand outlet sides, and a work roll of each stand. Calculate the stand outlet side plate thickness using the measured peripheral speed, from the calculated stand stand side plate thickness, the rolling load measurement value of each stand, the roll gap measurement value and the roll bending force measurement value, a gauge meter By calculating each parameter of the formula to calculate the roll expansion amount of the roll central portion, from the calculated each parameter and the roll expansion amount of the roll central portion, calculate the distribution of the roll expansion amount in the roll axial direction, the calculation Roll expansion change amount obtained from the measured roll expansion amount, measured rolling load change amount, work roll bending force change amount, entry side plate crown Based on the amount of change, calculate the amount of change in the plate thickness and plate crown on the stand exit side during rolling,
Corresponding to these changes, the amount of change in bending force of the work roll bender of each stand to keep the ratio of plate thickness and plate crown constant is calculated, and the bending force is corrected. Method for controlling plate wave shape of continuous rolling mill.