JP5627553B2 - Thickness control method considering dynamic characteristics of rolling mill - Google Patents

Description

  The present invention relates to a plate thickness control method for a rolling mill that rolls thick plates.

Conventionally, when a thick steel plate is rolled using a rolling device, a gap between a pair of work rolls of a rolling mill provided in the rolling device (hereinafter referred to as a roll gap amount) is adjusted. Plate thickness control is performed so that the exit side plate thickness at the end in the plate width direction matches the target value.
The rolling device has a plate thickness control unit for controlling the plate thickness. In this plate thickness control unit, feed forward AGC, BISRA-AGC, monitor AGC, and absolute value are used as automatic plate thickness control (AGC). AGC is adopted.

  The feedforward AGC is, for example, control for feeding forward the sheet thickness and deformation resistance of the rolling mill in the previous pass or the previous control cycle to the rolling mill. The BISRA-AGC is based on a gauge meter type, and is a control for estimating the plate thickness directly under the rolling mill by applying the rolling load measured by the load measuring instrument to the gauge meter type. The monitor AGC is control for actually measuring the delivery side plate thickness and feeding back the measured value (integrated value) to the rolling mill. The absolute value AGC is, for example, control focusing on the rolling of the front end portion of the plate, and is control using a fixed thickness of the plate thickness determined in advance before passing. The above-described monitor AGC and absolute value AGC employ PI control that combines proportional action and integral action.

Patent Document 1 discloses a technique related to plate thickness control using a gauge meter type for the next rolled material.
In the sheet thickness control method of a rolling mill disclosed in Patent Document 1, when the sheet thickness of a rolled material is controlled using a gauge meter type including a roll gap offset amount and a mill constant, the roll gap offset amount at the time of the previous rolling. And the mill constant were estimated based on actual measurement data measured during the same rolling, and the estimated roll gap offset amount and mill constant at the previous rolling were corrected in consideration of the previous and next rolling conditions. A roll gap offset amount and a mill constant are applied to sheet thickness control at the next rolling.

Specifically, when the sheet thickness of the rolled material is controlled using a gauge meter formula including the roll gap offset amount S ₀ and the mill constant M, the roll gap offset amount S _0i and the mill constant at the previous (i-th) rolling are used. and M _i, actually measured data measured during the rolling (e.g., a pressing position and the rolling load P _i for a plurality of points in the length direction of the rolled material was measured during the rolling, a plate of the same plurality of points measured after rolling Thickness). Then, the roll gap offset amount S _0i and the mill constant M _i are corrected in consideration of the difference between the previous and next (i + 1) rolling conditions, and the corrected roll gap offset amount S _{0i + 1} and the mill constant are corrected. M _{i + 1} is applied to the thickness control at the next rolling.

JP-A-8-155515

  Usually, a steel plate rolling mill is composed of a mass spring damper system, and has dynamic characteristics such that roll deformation of a work roll and housing deformation of the rolling mill occur and change during rolling. doing. In a state where such deformation has occurred, for example, the rolling load measured by a load cell provided between the housing of the rolling mill and the hydraulic cylinder has a value including an error affected by the deformation.

When the rolling load thus measured includes an error, the BISRA-AGC that estimates the thickness immediately below the rolling mill by applying the rolling load including the error to a gauge meter type cannot estimate the correct thickness value. There is a problem. In order to solve this problem, a technique for eliminating an error caused by the dynamic characteristics of the rolling mill from the rolling load is required.
However, since the plate thickness control method described in Patent Document 1 does not consider the dynamic characteristics of the rolling mill, the measured rolling load includes an error due to the dynamic characteristics of the rolling mill. Due to the rolling load including this error, there is a problem that the BISRA-AGC using the gauge meter type cannot output an accurate estimated value of the plate thickness, and thus cannot accurately control the plate thickness.

  Therefore, in view of the above problems, the present invention considers the dynamic characteristics of the rolling mill, performs BISRA-AGC, and can reliably bring the thickness of the rolled material close to the target value. An object is to provide a thickness control method.

In order to achieve the above-described object, the present invention takes the following technical means.
The sheet thickness control method of the present invention is a sheet thickness control method for controlling the roll gap of a rolling mill that rolls a rolled material. In consideration of the dynamic characteristics of the rolling mill, the rolling load fluctuation value ΔP ′ that satisfies the gauge meter formula is satisfied. Using the calculated dynamic characteristic rolling load fluctuation value ΔP ′, the roll gap correction amount ΔS is obtained, and the obtained roll gap correction amount ΔS is applied to the rolling mill , The rolling load fluctuation value ΔP ′ that satisfies the gauge meter equation is calculated by the following equation .

Where s is a Laplace operator, and a _{0 to} a ₃ , b _{0 to} b ₃ , and c _{0 to} c ₃ are the spring constant Ky of the housing, the spring constant Kb of the roll bending deformation, and the flat deformation of the roll. Spring constant Kr, equivalent mass My for elastic deformation of housing, equivalent mass Mb for bending deformation of roll, equivalent mass Mr for flat deformation of roll, viscosity coefficient By for elastic deformation of housing, viscosity coefficient Bb for bending deformation of roll, roll Is a coefficient calculated on the basis of the viscosity coefficient Br for flat deformation.
Further, the most preferable other embodiment of the sheet thickness control method of the rolling mill according to the present invention is a sheet thickness control method for controlling a roll gap of a rolling mill for rolling a rolled material, wherein a transfer function relating to a rolling load in the rolling mill is used. A rolling load fluctuation value ΔP ′ satisfying the gauge meter equation is calculated from Np (s) and a transfer function Ns (s) relating to the gap change amount, and a roll is calculated using the calculated dynamic characteristic rolling load fluctuation value ΔP ′. The amount of correction of the gap is obtained, and the amount of correction of the roll gap obtained is applied to the rolling mill. The rolling load fluctuation value ΔP ′ satisfying the gauge meter equation is “ΔP ′ = Np (s) ΔP + Ns (s) · ΔS ”.
However, Np (s) is a transfer function related to the rolling load fluctuation value ΔP, and Ns (s) is a transfer function related to the speed of the gap change amount ΔS.

  According to the present invention, a thickness control method for a rolling mill is provided, in which BISRA-AGC is executed in consideration of the dynamic characteristics of the rolling mill, and the thickness of the rolled material can be reliably brought close to the target value. can do.

It is the schematic which shows the structure of the rolling apparatus by embodiment of this invention. It is the schematic which shows the structure of the rolling mill (rough rolling mill thru | or finish rolling mill) of this invention. The figure shows the result when BISRA-AGC is executed in the case where the gauge meter plate thickness and the like are obtained by using the load measured as before, and (a) is a diagram showing a step response waveform graph. (B) is a Nyquist diagram showing the stability at that time. FIG. 7 shows the results when BISRA-AGC is executed when the gauge meter plate thickness or the like is obtained using the dynamic rolling load fluctuation value ΔP ′ according to the embodiment of the present invention, and (a) shows a step response. It is a figure which shows the graph of a waveform, (b) is a Nyquist diagram which shows the stability in that case. It is the block diagram which showed the structure of the rolling mill and plate | board thickness control apparatus by embodiment of this invention. It is a figure which shows the dynamic characteristic model in the conventional rolling mill, (a) is a model figure of roll deformation | transformation, (b) is a model figure of housing deformation | transformation. It is a figure which shows the model of the mass-spring-damper system in a rolling mill.

Hereinafter, a sheet thickness control method for a rolling mill according to the present invention will be described with reference to the drawings.
Referring to FIG. 1, a rolling device 1 for rolling a rolled material such as a thick steel plate has a heating furnace 3 for heating the rolled material 2 on the upstream side thereof, and a rolling material 2 on the downstream side of the heating furnace 3. The rough rolling machine 4 which performs rough rolling is provided. A finish rolling mill 5 that performs finish rolling is provided on the downstream side of the rough rolling mill 4. The slab heated in the heating furnace 3 is rolled a plurality of times (a plurality of passes) by the rough rolling mill 4 and the finish rolling mill 5 to become a thick steel plate of the product.

FIG. 2 shows a finish rolling mill 5 (hereinafter referred to as a rolling mill 5) provided in the rolling device 1. The rolling mill 5 has a pair of work rolls 6 and 6 for rolling the rolled material 2 and a pair of backup rolls 7 and 7 for backing it up.
Further, the rolling mill 5 is provided with a hydraulically driven reduction device that adjusts a gap length between the work rolls 6 and 6 (hereinafter referred to as a roll gap amount S). The reduction device includes, for example, a hydraulic cylinder 8 and a hydraulic reduction position control unit 9 that controls the hydraulic cylinder 8 to adjust the reduction position of the work roll 6.

A base end of a hydraulic cylinder 8 supported by a frame 11 of the rolling mill 5 is connected to the roll chock 10 that supports both ends of the work roll 6, and a rolling load P is measured on the frame 11 that supports the hydraulic cylinder 8. A load cell 12 is provided.
Further, a linear gauge 13 for measuring the distance from the frame 11 to the roll chock 10 is provided along the hydraulic cylinder 8 between the roll chock 10 and the frame 11 of the rolling mill 5. The distance measured by the linear gauge 13 Thus, the roll gap amount S or the change amount ΔS of the roll gap amount is obtained.

Further, on the exit side of the rolling mill 5, a plate thickness meter 14 for measuring the exit side plate thickness (exit side edge thickness) of the rolled material 2 is provided. As the thickness gauge 14, a γ-ray thickness gauge or the like can be adopted.
The rolling mill 5 receives the rolling load P measured by the load cell 12 and the outlet side plate thickness measured by the plate thickness meter 14, and the hydraulic pressure reduction position control unit so that the outgoing side plate thickness of the rolled material 2 becomes a predetermined one. A plate thickness control unit 15 for controlling 9 is provided. The plate thickness control unit 15 is composed of a process control or a PLC, and an AGC control system, a vendor control system, etc., which will be described later, are incorporated in the form of a program.

As shown in FIGS. 2 and 5, the plate thickness control unit 15 in the present embodiment executes BISRA-AGC to control the hydraulic pressure reduction position control unit.
BISRA-AGC is a type of AGC (gauge meter AGC) using a gauge meter type, and determines the thickness of the outlet side of the rolling mill 5 in consideration of the elasticity of the rolling mill 5 and the deformation resistance of the rolled material 2. Thus, for example, the exit side plate thickness is estimated based on the rolling load P measured by the load cell 12 in consideration of the mill constant, and the rolling mill 5 is controlled based on the value.

In FIGS. 2 and 5, a monitor AGC and an absolute value AGC that employ PI control combining proportional control and integral control are shown as an AGC control system, but this is not implemented in this embodiment. Make it not exist. Although FF-AGC is also shown, it is assumed that FF-AGC is not executed in the plate thickness control unit 15 according to the present embodiment.
First, the problems that occur when the rolling mill 5 according to the present embodiment is controlled by the conventional plate thickness control method will be described with reference to FIG.

  As shown in FIGS. 6A and 6B, the rolling mill 5 can be modeled as a mass-spring-damper system. That is, the mass (mass) of the work roll, the backup roll, and the housing, the elastic deformation (spring) of the work roll, the backup roll, the housing, and the like when the rolling load P is applied, and the elastic deformation amount and the rolling load change. The rolling mill 5 can be expressed using a buffer (damper).

Since the rolling mill 5 is composed of such a mass-spring-damper system, the roll deformation of the work roll and the backup roll and the housing deformation of the rolling mill 5 occur and change during the rolling time during rolling. It has the following dynamic characteristics.
The rolling load P measured by the load cell 12 is affected by the dynamic characteristics of the rolling mill 5 and includes an error. Depending on the rolling load P including such an error, the gauge meter equation shown in the equation (1) does not hold correctly with respect to the rolling load variation value ΔP which is the variation amount of the rolling load P including the error.

Thus, when the rolling load fluctuation value ΔP that does not satisfy the gauge meter type is used, an error also occurs in the BISRA-AGC that operates on the premise of the gauge meter type.
Further, a gauge meter thickness Δhg based on the gauge meter formula is widely used in the control of sheet rolling. However, when the rolling load fluctuation value ΔP that does not satisfy the gauge meter equation is used, the gauge meter plate thickness Δhg does not match the true plate thickness Δh, as shown in equation (2).

  The gauge meter plate thickness Δhg is a plate thickness relating to a minute displacement near the equilibrium point, and an estimated value hg of the absolute plate thickness is calculated from the mill elongation ε and the roll gap amount S estimated from a static mill deformation model ( Also in the case of estimation in 3), since the dynamic characteristics of the rolling mill 5 are not affected, the estimated value hg does not coincide with the true thickness h, similarly to the gauge meter thickness Δhg.

In addition to this, in gauge rolling, gauge meter plate thickness AGC, absolute value AGC, and the like for feedback control of gauge meter plate thickness Δhg and absolute plate thickness estimated value hg are widely used. However, since neither the gauge meter plate thickness Δhg nor the estimated value hg of the absolute plate thickness coincides with the true plate thickness h, an error also occurs in these AGCs.
In order to solve the problems in the conventional sheet thickness control method as described above, dynamic rolling load fluctuations satisfying the gauge meter formula as shown in formula (4) in a state where the rolling mill 5 has dynamic characteristics. The value ΔP ′ will be described.

The plate thickness controller 15 according to the present embodiment uses a dynamic rolling load fluctuation value ΔP ′ that satisfies the gauge meter equation as shown in equation (4).
This dynamic characteristic rolling load fluctuation value ΔP ′ is given by an expression having a transfer function in each term of ΔP and ΔS, as shown in Expression (5). The details of the derivation of Equation (5) will be described at the end of this specification (see [Regarding Derivation of Equation (5)]).

  Where Ky is the spring constant of the housing, Kb is the spring constant of the bending deformation of the roll, Kr is the spring constant of the flat deformation of the roll, My is the equivalent mass for the elastic deformation of the housing, Mb is the equivalent mass for the bending deformation of the roll, Mr Is an equivalent mass with respect to flat deformation of the roll, By is a viscosity coefficient with respect to elastic deformation of the housing, Bb is a viscosity coefficient with respect to bending deformation of the roll, and Br is a viscosity coefficient with respect to flat deformation of the roll.

  By using the dynamic characteristic rolling load fluctuation value ΔP ′ shown in Expression (5), the sheet thickness control unit 15 executes BISRA-AGC based on Expression (6).

  Also, with respect to the gauge meter plate thickness Δhg, the dynamic characteristic rolling load fluctuation value ΔP ′ is used in place of the rolling load fluctuation value ΔP, so that the gauge matches the true plate thickness Δh as shown in the equation (7). Meter plate thickness Δhg can be obtained.

In addition to this, with respect to the estimated value hg of the absolute plate thickness, similarly, by using P ₀ + ΔP ′ (P ₀ is the equilibrium point of ΔP ′) instead of the rolling load P, the true plate thickness Δh can be obtained. An estimated absolute thickness hg can be obtained.
With reference to FIGS. 3 and 4, the control result when the gauge meter plate thickness and the like are obtained using such dynamic characteristic rolling load fluctuation value ΔP ′ and BISRA-AGC is executed will be described.

FIG. 3 shows that the dynamic characteristics of the modeled mass-spring-damper system shown in FIG. 6 exist, and the gauge meter plate thickness, etc. is obtained by using the load measured as before, and the control gain of the BISRA-AGC (Tuning rate) This is a result when BISRA-AGC is executed with α _{b set} to 0.75.
4, the formula (5) using the dynamic characteristic rolling load variation [Delta] P 'calculated gauge meter thickness, etc., when running BISRA-AGC control gain alpha _b of BISRA-AGC as 0.75 It is a result.

In FIG. 3 (a), the step response at a delay time of about 1 second is largely staggered, and in FIG. 4 (a), it is close to 0 without hunting.
Also, in FIG. 3B, the stability margin is very small, whereas in FIG. 4B using the dynamic rolling load fluctuation value ΔP ′, the stability margin is large, and very stable control is realized. ing.

Increasing the control gain alpha _b further BISRA-AGC from the state shown in FIG. 3, when advancing the time constant of the control system, if not using the equation (5) dynamic characteristics rolling load variation [Delta] P 'by plate thickness control not Stabilize. However, when the dynamic characteristic rolling load fluctuation value ΔP ′ is used, the plate thickness control is not destabilized, and the step response and stability are stabilized in the state shown in FIG. This is also clear from the fact that the range of “stability margin” shown in FIG. 4B is wider than the range of “stability margin” shown in FIG.

Further, according to the equation (5), the Laplace operator s has a third-order dynamic characteristic, and in particular, the speed term of the roll gap amount ΔS has a high s-order of the numerator and the higher-order mode is omitted. There is no problem. In general the mass very small compared to the viscosity and the spring constant, for example, c ₃ is smaller than the other c ₂ to c _0, no problem be omitted and c 3 _{= 0.}
[Modification]
By the way, in equation (5), the coefficient of the transfer function is given from physical parameters such as the spring constant Ky of the housing and the equivalent mass My for the elastic deformation of the housing. The order may be determined.

  For example, when the speed of the gap change amount ΔS, the rolling load fluctuation value ΔP, and the time series data of the delivery side plate thickness Δh are given, the dynamic rolling resistance fluctuation value ΔP ′ is obtained from the equation (4). Here, the relationship of Formula (5) to Formula (8) is materialized.

Therefore, the coefficient of the transfer function can be identified by using the least square method or the like based on the equation (8) for each time series data.
Further, the order of the transfer function can also be determined by using AIC (Akaike Information Criterion) or the like. Thus, from the transfer function Np (s) regarding the rolling load fluctuation value ΔP obtained by identifying the order and the coefficient and the transfer function Ns (s) regarding the speed of the gap change amount ΔS, Alternatively, the dynamic rolling load fluctuation value ΔP ′ may be given by equation (9).

Further, the dynamic rolling load fluctuation value ΔP ′ may be given by the equation (10) with respect to the delay time T _y of the hydraulic reduction system.

Here, α _y is a constant indicating the gain of BISRA-AGC, and is 100% when 1 and 0% when 0.
According to equation (10), it is possible to enhance the responsiveness of the compensating rolling control delay time T _y of the hydraulic pressure system.
As described above, the rolling load fluctuation value ΔP ′ satisfying the gauge meter formula is calculated in consideration of the dynamic characteristics of the rolling mill, and the roll gap of the roll gap is calculated using the calculated dynamic characteristic rolling load fluctuation value ΔP ′. By using the thickness control method of the rolling mill according to the present invention in which the correction amount ΔS is obtained and the obtained roll gap correction amount ΔS is applied to the rolling mill, the thickness of the rolled material is reliably brought close to the target value. It becomes possible.
[Regarding derivation of Equation (5)]
Details of the derivation of Equation (5) used in the above-described invention will be described below.

Equation (5) is formulated in consideration of the dynamic characteristics of the rolling mill 5 shown by the mass-spring-damper system in FIG.
The derivation of Equation (5) will be described with reference to FIGS. FIG. 7 shows a mass-spring-damper system model on the right or left side of the symmetric rolling mill 5, which is a mass M of the roll, loads P _{1 to} P ₃ applied to the roll, and a plate thickness h. , And the hydraulic cylinder X ₀ , the upper roll center of gravity position X ₁ , the displacement amount X _{2 of the} upper surface of the rolled material, the displacement amount X _{3 of} the lower surface of the rolled material, and the lower roll center of gravity position X ₄ . Equation (5) is derived based on this model.

First, equations (11) to (16) are established from the model of FIG. First, the load _{P 1} is expressed by the equation (11).

Next, regarding the load P ₁ and the load P ₂ , the equation of motion of Expression (12) is established from the mass M of the work roll and the acceleration of the work roll.

Further, the load _{P 2} is expressed by the equation (13) and (14).

Furthermore, regarding the load P ₂ and the load P ₃ , the equation of motion of Expression (15) is established from the mass M of the work roll and the acceleration of the work roll.

Here, with respect to load _{P 3,} equation (16) holds.

The following calculation is performed based on the equations (11) to (16). First, by modifying the equation (11) leads to equation (17) representing the displacement amount _{X 1.}

This equation (17) from equation (12) leads to equation (18) representing a load _{P 2.}

Thus guided equations (18) from equation (13) leads to equation (19) representing the displacement _{X 2.}

Next, Expression (20) representing the displacement amount X ₃ is derived from Expression (14) and Expression (16).

Furthermore, Expression (21) is obtained from Expression (15) and Expression (16). From this Expression (21), the displacement amount X ₄ is expressed as Expression (22).

  In addition, Expression (23) representing the plate thickness h is obtained from Expression (19) and Expression (20).

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, for example, operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that a person skilled in the art normally performs. Instead, values that can be easily assumed by those skilled in the art are employed.

DESCRIPTION OF SYMBOLS 1 Rolling apparatus 2 Rolled material 3 Heating furnace 4 Coarse rolling mill 5 Finish rolling mill 6 Work roll 7 Backup roll 8 Hydraulic cylinder 9 Hydraulic pressure reduction position control part 10 Roll chock 11 Frame 12 Load cell 13 Linear gauge 14 Plate thickness gauge 15 Plate thickness control part

Claims (2)

In the sheet thickness control method for controlling the roll gap of the rolling mill for rolling the rolled material,
The rolling load fluctuation value ΔP ′ satisfying the gauge meter formula is calculated while considering the dynamic characteristics of the rolling mill, and the roll gap correction amount ΔS is obtained using the calculated dynamic characteristic rolling load fluctuation value ΔP ′. Applying the obtained roll gap correction amount ΔS to the rolling mill ,
The rolling load fluctuation value ΔP ′ satisfying the gauge meter equation is calculated by the following equation :
Where s is a Laplace operator, and a0 to a3, b0 to b3, and c0 to c3 are the spring constant Ky of the housing, the spring constant Kb of the roll bending deformation, the spring constant Kr of the flat deformation of the roll, Equivalent mass My for elastic deformation, equivalent mass Mb for roll bending deformation, equivalent mass Mr for roll flat deformation, viscosity coefficient By for elastic deformation of housing, viscosity coefficient Bb for roll bending deformation, viscosity coefficient for roll flat deformation This is a coefficient calculated based on Br. In the sheet thickness control method for controlling the roll gap of the rolling mill for rolling the rolled material,
A rolling load fluctuation value ΔP ′ satisfying the gauge meter equation is calculated from the transfer function Np (s) related to the rolling load in the rolling mill and the transfer function Ns (s) related to the gap change amount, and the calculated dynamic rolling Using the load fluctuation value ΔP ′, the correction amount of the roll gap is obtained, and the correction amount of the obtained roll gap is applied to the rolling mill,
The rolling load fluctuation value ΔP ′ satisfying the gauge meter equation is calculated by the following equation :
However, Np (s) is a transfer function related to the rolling load fluctuation value ΔP, and Ns (s) is a transfer function related to the speed of the gap change amount ΔS.