JP2878060B2 - Automatic hot thickness control method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automatic thickness control in hot rolling at a continuous hot rolling mill or a thick plate mill, and more particularly to a thickness control for suppressing a thickness deviation due to mill stretching.

[0002]

2. Description of the Related Art For example, the amount of increase in the roll gap, in which the roll gap of a rolling mill spreads, depends on the rolling conditions such as the load and bender force generated when a rolled material is bitten into a hot rolling mill such as a hot rolling finishing stand. This is referred to as mill stretching, which includes elastic deformation of the housing, bending and elastic flattening of the work roll, bending and elastic flattening of the backup roll, and the like. Therefore, in order to accurately estimate the mill stretch, it is necessary to calculate the stretch amount for each item using a theoretical model that is dynamically analyzed for each of the items included in the mill stretch, and superimpose them. But A
In control requiring high responsiveness, such as GC (automatic thickness control), reflecting these stretch amounts in real time in the calculated AGC is too time-consuming to apply and cannot be applied. Therefore, methods for estimating the amount of mill stretch of a rolled material in AGC include housing, work roll,
The whole rolling mill including the backup roll is considered as one elastic body, and from the mill constant equivalent to the spring constant of this elastic body, the actual rolling load, the zero adjustment load, and the width correction coefficient of the rolled material, the following equation (1) or I was asking for it in a similar way.

[0003] This technology has been generalized as a well-known fact since AGC was developed from the beginning.

MS = (P−P _z ) / (M × α) (mm) (1) where MS: estimated mill stretch amount (mm) P: actual rolling load (ton) P _z : zero adjustment Load (ton) M: Mill constant (ton / mm) α: Width correction coefficient of rolled material (−) The above-mentioned mill constant M is measured for each stand. That is, when rolling is not being performed, the work roll is gradually tightened from the state where the upper and lower work rolls are in contact with each stand, and the value is obtained off-line from the relationship between the actually measured load and the actually measured pressure reduction position (gap) at that time. It is stored in advance on the device on which the AGC operates.

Further, the width correction coefficient α of the rolled material is such that an aluminum plate having a different width is inserted between upper and lower work rolls for each stand and gradually tightened from the contact state, and the actual measured load and the actual measured pressure reduction position (gap) at that time are determined. Is obtained off-line from the relationship, and its value is stored in advance on a device on which the AGC operates.

[0006]

The components (components) of the mill stretch include bending deformation of the work roll, flattening deformation of the work roll at the contact portion between the rolled material and the work roll, bending deformation of the backup roll, and work roll. Flattening deformation of the two rolls, elastic deformation of the housing, the width profile of the work roll, which changes with time, and the width profile of the backup roll at the contact portion between the roll and the backup roll. And the rate of change is also different. Therefore, as in the conventional method, the whole rolling mill is considered as one elastic body, and the accuracy of the mill stretch estimated based on the mill constant M equivalent to the spring constant of this elastic body has a limit. The accuracy of gauge gauge thickness calculated using
The thickness accuracy of GC does not increase.

[0007] It is an object of the present invention to make the grasp of the mill stretch more accurate and reflect it in the automatic thickness control in hot rolling.

[0008]

According to the present invention, immediately after a rolled material bites into a stand, the actual rolling position of the stand, the actual rolling load, and the peripheral speed of the mill are input for each control cycle. Calculate the mill stretch from the elastic modulus of the mill and the mill, calculate the oil film amount from the actual rolling load and the mill peripheral speed,
Calculate the correction amount such as the thermal expansion of the roll, calculate the thickness of the rolled material on the exit side of the stand by the gauge meter formula from these calculation results and the actual rolling position, and reduce the difference between the target thickness on the exit side of the stand to zero. In a self-contained hot automatic thickness control method that determines and controls the amount of rolling reduction that can be applied , the rolling load and bender pressure must be adjusted for each rolled material before starting the automatic thickness control. Predict and the predicted rolling load
Based on the predicted bender pressure and the mill stretch rolling load influence coefficient, mill stretch bender pressure influence coefficient and constant, ie, the mill stretch parameter, the mill including the mill stretch parameter, the rolling load and the bender pressure is calculated at the time of the mill stretch calculation. The mill stretch is calculated by introducing the calculated mill stretch parameter, the actual rolling load, and the actual bender pressure into the stretch calculation model.

In the apparatus embodying the present invention, the mill stretch parameter required for estimating the amount of mill stretch in each control cycle of AGC is set to a relatively responsive function such as a finish setting calculation function (FSU) which is different from AGC. New functions that allow precise calculations without requiring

[0010]

The principle of calculation of the mill stretch parameter will be described first. FIG. 3 shows a conceptual diagram of the mill stretch. In general, the rolling position in a state where a zero load _Pz is applied to the work roll in the kiss roll state is set to 0 (zero). Mill stretch (M required for position calculation)
S) is represented by the following equation.

[0011] _{MS = Ω pt -Ω 0 pt +} g (pt) (mm) Ω pt in ... (2) (2), the mill stretch when the rolling load P _t in the real rolling conditions has occurred And is represented by equation (3). Also, Omega _{0 pt} is the mill stretch when rolling load P _t in the kiss roll conditions occurs, represented by the formula (4). Ω _pt = Ω _{BW i} + Ω _{WM i} + Ω _B + Ω _W + Ω _H (mm) ··· (3) Ω _{0 pt} = Ω _{0 · BW i} + Ω _{0 · WW i} + Ω _{0 · B} + Ω _{0 · W} + Ω _{0 H} ( mm) ··· (4) However, Ω _{BW i:} BUR at the time of load P _t is applied in the real rolling conditions
-WR between flat weight (both rolls min) (mm) Ω _{WM i:} when load P _t is applied in a real rolling conditions WR-
WR flat amount between the materials (both rolls min) (mm) Ω _B: BUR when the load P _t is applied in actual rolling conditions
Amount of deflection (both rolls min) (mm) Ω _W: actual WR bending amount when the load P _t is applied in the rolling conditions (both rolls min) (mm) Ω _H: housing when the load P _t is applied in actual rolling conditions elongation amount (both rolls _{min) (mm) Ω 0 · BW} i equal: BUR-WR flat amount when the load P _t is applied in a kiss roll conditions (both rolls _{min) (mm) Ω 0 · WW} i: kiss conditions load P _t flat weight between WR-WR when applied (both rolls min) (mm) Ω _{0 · B} in: BU when the load P _t is applied at kiss conditions
R amount of deflection (both rolls _{min) (mm) Ω 0 · W} : In the kiss under the conditions at the time of load P _t applied WR
Amount of deflection (both rolls min) (mm) Ω _0H: elongation of the housing or the like during the load P _t is applied in a kiss roll conditions (both rolls min) (mm) WR: work roll BUR: backup rolls g _(pt): kiss the difference of the load P _t is applied at the Reicho load P _z applied during the mill stretch under conditions (mm) Next, in the formula _{(2), Ω pt, Ω} 0 pt is posted to a known literature "plastic and processing" “Calculation of Mill Stretch of Four-high Rolling Mill and Six-high Rolling Mill” (VOL.27 NO304,1986 Page57
Assuming that it is a dynamic theoretical model that can be arranged as a function of rolling load and bender force as shown in 9), (Ω _pt −Ω _{0 pt} ) in equation (2) becomes (5) It can be expressed by an expression.

(Ω _pt −Ω _{0 pt} ) = K _P × P _t + K _F × F + K _C (mm) (5) where, K _P : rolling load influence coefficient of the mill stretch (mm /
ton) K _F : Mill stretch bender pressure influence coefficient (mm / ton) K _C : Constant (mm) P _t : Rolling load (ton) under actual rolling conditions F: Bender pressure (ton) under actual rolling conditions the material different function from the AGC predetermined time before biting the rolling mill, for example, finishing setting calculation function (FSU) in the predicted rolling load P _e based on rolling conditions of the rolled material, the prediction vendor pressure F _e and (Omega _pe −Ω _{0 pe} ) is accurately calculated, and the sum of partial derivatives by rolling load and the sum of partial derivatives by bender force are calculated for all components of (Ω _pe −Ω _{0 pe} ). These are called the rolling load influence coefficient K _{P of} the mill stretch and the bender influence coefficient K _{F of the} mill stretch, respectively. From the previously obtained (Ω _pe −Ω _{0 pe} ), the contribution of the mill load to the mill stretch (K _P × A value K _C is obtained by subtracting P _e ) from the mill stretch contribution amount (K _F × F _e ) of the bender force.

These three coefficients are collectively called mill stretch parameters.

The above K _P , K _F , and K _C can be expressed by the following equations (6), (7), and (8). K _P = ∂ (Ω _pe −Ω _{0 pe} ) / ∂P _e = ∂ (Ω _{BW i} + Ω _{WM i} + Ω _B + Ω _W + Ω _H −Ω _{0 · BW i} −Ω _{0 · WW i} −Ω _{0 · B} −Ω _{0 · W} −Ω _{0 H} ) / ∂P _e (mm / ton) (6) K _F = ∂ (Ω _pe −Ω _{0 pe} ) / ∂F _e = ∂ (Ω _{BW i} + Ω _{WM i} + Ω _B + Ω _W + Ω _H −Ω _{0 ・ BW i} −Ω _{0 ・ WW i} −Ω _{0 ・ B} −Ω _{0 ・ W} −Ω _0H ) / ΔF _e (mm / ton) ・ ・ ・ (7) K _C = (Ω _pe −Ω _{0 pe} ) − (K _P × P _e + K _F × F _e ) (mm) (8) where K _{P is} the rolling load influence coefficient of the mill stretch (mm /
ton) K _F: Vendor pressure influence coefficients of mill stretch (mm / ton) K _C: Constant (mm) P _e: actual rolling predicted rolling load in conditions (ton) F _e: Prediction Vendor pressure in the actual rolling conditions ( ton) Ω _pe: real prediction in the rolling conditions rolling load P _e mill stretch of time that occurred (mm) Ω _{0 pe:} kiss roll mill stretch when the predicted rolling load P _e occurs in conditions (mm) all stand After calculating these mill stretch influence coefficients (mill stretch parameters) for the FSU at an appropriate timing before the rolled material arrives at the corresponding rolling mill.
The obtained mill stretch parameters are passed to the AGC function via a transmission circuit that connects the control device that functions with the control device with which the AGC functions. The mill stretch parameter obtained here is extremely high precision because it is a rolling load and a bender pressure influence coefficient that match the rolling conditions of the material from the theoretical model for each material.

Next, when estimating the amount of mill stretch for each control cycle, the AGC function uses a linear equation shown below to quickly and accurately calculate the mill stretch parameter, the actual rolling load (Pa), and the actual bender pressure (Fa). The stretch can be estimated, and as a result, a high-accuracy plate thickness accuracy can be obtained.

MS = K _p × P _a + K _F × F _a + K _C + g _(pa) (mm)
(9) However, K _P : rolling load influence coefficient of mill stretch (m
m / ton) K _F: Vendor pressure influence coefficients of mill stretch (mm / ton) K _C: Constant (mm) P _a: rolling load actual value in the actual rolling (ton) F _a: Vendor pressure results in the actual rolling value (ton) g _(pa): the difference between the mill stretch and Reicho load P _Z upon application of the mill stretch when a load P _a is applied in a kiss roll conditions (mm) formula (9), the value of g _(pa) Is the difference between the mill stretch when the load Pt is applied and the mill stretch when the zero load Pz is applied under the kiss roll condition. Therefore, the relationship between the load measured during the mill stretch measurement and the rolling position is prepared as a constant table in the AGC. In other words, it can be accurately obtained by broken line interpolation or the like.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be described in detail below with reference to FIGS. 1, 2, 4 and 5. FIG. 2 shows that the rolled material 6
And a thermometer 4 installed on the rear surface of the rough rolling mill 3.
Shows the state where the measurement of the temperature of the rolled material 6 has been completed.

FIG. 1 shows a system in which the rolled material 6 shown in FIG. 2 finishes rough rolling, bites into the finishing rolling mill group 5, and performs an enemy calculation of the mill stretch in the AGC operation state. First, in FIG. 2, at the timing when the temperature measurement of the rolled material 6 is completed, the finish setting calculation function (FSU) stored in the general control computer 1 which is the computer that controls the entire hot rolling line operates. .

As shown in the FSU schematic flow chart of FIG. 4, the FSU inputs initial data such as the product specification and material of the material at F11, calculates the thickness of the finishing stand at the stand at F12, and calculates the heat at each stand at F13. The temperature and mill speed of the rolled material are calculated, the rolling load of the material is estimated from the draft and the temperature at each stand in F14, and the bender pressure for realizing the target crown of the material is estimated in F15.

Next, in step F16, the mill stretch of the material is calculated, and the mill stretch parameters represented by equations (6), (7), and (8) are calculated. In F17, the rolling position of each stand is calculated, and in F18, the set value for the auxiliary device such as a looper is calculated, and the process ends. In this flowchart, the mill stretch parameter calculation portion of F16 is a process newly provided in the present invention. Except for the mill stretch parameter calculation part of F16, the processing of F11 to F18 is a conventionally known processing function.

The mill stretch parameter calculated by the FSU is transmitted to the AGC control device by a data transmission function existing in the general control computer 1 as a function different from the FSU.

The following table shows a calculation example of the mill stretch parameter calculated by the FSU. Table 1 shows the material conditions used for the mill stretch parameter calculation. Table 2 shows the machine conditions used for the mill stretch parameter calculations. Table 3 shows a calculation result of the mill stretch parameter and a calculation example of the main mill stretch parameter components at this time.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

Next, after the rough rolling (FIG. 2), the rolled material 6
Is transported to a finishing stand (FIG. 1), and the AGC control is started in order from the stand that has been engaged. FIG. 1 shows a state in which the rolled material 6 bites into the Fi stand, and the AGC stored in the AGC control device 2 at this timing.
The function starts the thickness control of the Fi stand.

As shown in the AGC schematic flowchart of FIG. 5, the AGC checks control conditions such as a control mode and a control gain in F21 for each control cycle of the stand, and in F22, the rolling position, rolling load, bender and the like of each stand. The actual data such as pressure is read, the mill stretch calculation shown in equation (10) is performed in F23, the oil film of each stand is calculated in F24, the thickness of the material in each stand is calculated in F25, and the plate thickness is calculated in F26. Deviation calculation is performed, and in step F28, a draft correction amount for making the thickness deviation zero is calculated, and a control output is performed.

In this flowchart, the mill stretch calculation method of F23 is a process newly provided in the present invention.
Except for the mill stretch calculation method of F23, F23 to F23
The process 28 is a conventionally known processing function.

MS = K _p × P _a + K _F × F _a + K _C + g _(pa) (mm) (10) where K _{P is} the rolling load influence coefficient of the mill stretch (mm /
ton) K _F: Vendor pressure influence coefficients of mill stretch (mm / ton) K _C: Constant (mm) P _a: real rolling when the rolling load actual value (ton) F _a: real rolling when vendors pressure actual value ( _ton) g _(pa): the difference between the mill stretch and Reicho load P _Z upon application of the mill stretch when a load P _a is applied in a kiss roll conditions (mm) mill stretch obtained in this manner is strictly by FSU As a result, the same accuracy as the result calculated from the simple model formula can be obtained, and the prediction accuracy of the strip thickness on the stand exit side can be greatly improved.

As a result, the amount of mill stretch that matches the rolling conditions that change for each rolled material can be estimated in a short time and with high accuracy.

Therefore, a control cycle such as AGC is several tens of meters.
Even if the control is severe in s and responsiveness, accurate mill stretch estimation can be performed without time constraints (in real time), so accurate estimation of the exit side thickness of each stand is possible. As a result, if absolute value AGC can be applied Dramatically improved clamping thickness accuracy.

Table 4 shows the quantitative effects. Table 4 shows the variation of the head thickness deviation of the rolled material having a product thickness of 2 mm to 9 mm before and after using the present invention in the finish rolling in the hot rolling mill.

[0033]

[Table 4]

[0034]

As described above, according to the present invention, the AGC in the finishing mill of the hot strip mill is used.
The function makes it possible to more accurately grasp and reflect on the AGC the mill stretch required when estimating the exit side plate thickness of the rolled material that is caught in the stand. As a result,
AGC control accuracy of AGC is improved, and product thickness is 2mm to 9mm
The variation in head thickness deviation of the rolled material was 61.6 μm, but it was improved to 43.2 μm after using the present invention.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a rough rolling mill for supplying a rolled material 6 to a finishing mill 5 shown in FIG.

FIG. 3 is a graph showing a relationship between a rolling load of a rolling stand of a finishing mill 5 and a mill stretch.

FIG. 4 is a flowchart showing a part of the processing functions of the general control computer 1 shown in FIG.

FIG. 5 is a flowchart showing a part of a processing function of the AGC control device 2 shown in FIG. 1;

[Explanation of symbols]

1: General control computer 2: AGC
Control device 3: Rough rolling mill 4: Thermometer 5: Finishing rolling mill group 6: Rolled material 7: Transmission circuit

Claims (2)

(57) [Claims] 1. Immediately after the rolled material bites into the stand,
For each control cycle, input the actual rolling position of the stand, the actual rolling load, and the mill peripheral speed, calculate the mill stretch from the actual rolling load and the elastic modulus of the mill, and calculate the oil film amount from the actual rolling load and the mill peripheral speed. Then, the correction amount such as the thermal expansion of the roll is calculated, and the thickness of the rolled material on the exit side of the stand is calculated from the calculated result and the actual reduction position by a gauge meter formula, and the difference between the thickness and the target thickness on the exit side of the stand is calculated. In a self-contained automatic hot plate thickness control method that determines the amount of draft reduction to zero and controls the output, the rolling load must be set for each rolled material before starting the automatic plate thickness control.
Weight and bender pressure, and the predicted rolling load and
Based on the mill pressure, the mill stretch rolling load influence coefficient and the mill stretch bender pressure influence coefficient and constants, ie, the mill stretch parameters, are calculated. When the mill stretch is calculated, the mill stretch including the mill stretch parameters, the rolling load, and the bender pressure is calculated. An automatic hot plate thickness control method, wherein a mill stretch is calculated by introducing the calculated mill stretch parameter, actual rolling load and actual bender pressure into a model. 2. A method for predicting a rolling load and a bender pressure.
Rolled material of the mill stretch calculation model that includes the rolling load effect factor that defines the relationship of mill stretch to rolling load based on the rolling load and predicted bender pressure, and the bender pressure effect factor and constant that defines the relationship of mill stretching to bender pressure The corresponding rolling load influence coefficient, bender pressure effect coefficient and constant are calculated for each rolled material, and these coefficients and constants are calculated for the rolled material before the automatic thickness control of each rolled material is started. Mill stretch parameter calculation means to be provided to the control means; and, immediately after the rolled material has caught in the hot rolling stand, the coefficient and constant of the rolled material provided by the mill stretch parameter calculation means for each control cycle. The mill stretch is calculated by introducing the rolling load and bender pressure of the stand into the mill stretch calculation model. Calculate the amount of oil film from the rolling load of the stand and the peripheral speed of the mill, calculate the correction amount such as the thermal expansion of the roll, and calculate the correction amount such as the thermal expansion of the roll on the exit side of the stand by the gauge meter type from the rolling position of the stand. An automatic thickness control means for calculating the thickness of the rolled material, calculating a reduction amount for making the thickness substantially the target thickness, and controlling the reduction of the stand.