JP2001321811A - Thickness control method in continuous rolling mill - Google Patents

Abstract

(57) [Problem] To provide a method for controlling a thickness of a continuous rolling mill which is excellent in responsiveness and control accuracy and does not cause fluctuation in tension. SOLUTION: In step 1, rolling results such as a thickness gauge and a passing speed detector for a material to be rolled are read. Next, in step S2, the exit plate thickness of each stand is calculated by mass flow calculation. Next, in step S3, the deformation resistance of the rolled material in each stand is determined. Next, in step S4, a rolling load for obtaining a target exit plate thickness at each stand, that is, a reference rolling load is obtained. next,
In step S5, an error term of the gauge meter type is calculated. Next, in step S6, a reference roll gap is determined. Next, in step S7, a main engine speed that maintains the mass flow balance is calculated. Finally, in step S8, the roll gap of each stand and the main machine speed are corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a thickness of a continuous rolling mill comprising a plurality of rolling mill stands, the thickness being controlled at a target value on the exit side of the rolling mill.

[0002]

2. Description of the Related Art In a continuous hot rolling mill comprising a plurality of rolling mill stands, conventionally, a thickness gauge is provided only on the exit side of a final stand, and the thickness on the exit side of each stand is indirectly determined from a measured value of a rolling load. It is general to control the thickness in accordance with the above. That is, the outlet plate thickness at each stand is calculated based on the following gauge meter formula (BISRA formula). h (i) = s (i) + P (i) / M (i) + δ (i) ... (1) where, h (i): Estimated exit plate thickness s (i): Roll gap P ( i): Rolling load M (i): Rolling mill stiffness coefficient (mill constant) δ (i): Correction term for roll thermal expansion, wear, etc. In each stand, due to inaccuracy of correction term δ (i) In order to reduce the influence of the error, the estimated value of the exit side thickness of the rolled material is calculated based on the roll gap and the rolling load (referred to as lock-on roll gap and lock-on rolling load) at the moment when the tip of the strip is caught in each stand. The thickness control by the lock-on method (lock-on AGC) that adjusts the roll gap according to the fluctuation of the rolling load so as to be maintained at the exit-side sheet thickness estimated value calculated by the above equation (1) is generally performed. It is used for In addition, in this specification, the roll gap means a roll gap converted into a no-load state in which no rolling load is applied.

In this case, the lock-on-roll gap is s0 (i),
Assuming that the lock-on rolling load is P0 (i), the plate thickness at this time is calculated from h0 (i) by the equation (1). Then, the roll gap during rolling is s (i), the rolling load is P (i), and at this time, as the sheet thickness h (i) calculated by the equation (1), the sheet thickness deviation is Δh (i). = h (i) -h0 (i), roll gap deviation Δs (i) = s (i)
-s0 (i), assuming that the rolling load deviation is ΔP (i) = P (i) −P0 (i), Δh (i) = Δs (i) + ΔP (i) / M (i) (2) Becomes

In the lock-on AGC, since Δh (i) = 0 is maintained, the roll gap is maintained such that Δs (i) = − ΔP (i) / M (i) (3) from equation (2). Can be adjusted.

However, as described above, the lock-on AGC only works to maintain the exit plate thickness of each stand when the leading end of the rolled material bites into each stand. There is no function to control the target value. Therefore, when the sheet thickness on the final stand exit side does not match the target sheet thickness of the product, a feedback control system for correcting h0 (i) of each stand according to the deviation is provided. being called.

However, in the monitor AGC,
When feedback is provided to the upstream stand, the dead time increases, the control gain cannot be increased, and control with high responsiveness cannot be performed. In addition, it is difficult to optimally determine the distribution of the gain at which feedback is provided to each stand. Therefore,
The control is performed centering on the final stand, and the load is concentrated on the final stand. As a result, the shape of the rolled material may be deteriorated.

[0007] Recently, the mill constant and the correction term in the equation (1) are accurately calculated by a computer, and the roll gap is adjusted so that the exit side sheet thickness estimation value h (i) in the equation (1) is maintained at a target value. The absolute value AGC to be controlled has been used. According to the absolute value AGC, the output side plate thickness of each stand is maintained at the target value, so that the problems that the lock-on AGC has are reduced to some extent. However, it is difficult to accurately calculate the mill constant and the correction term.
The problems that GC has are not completely solved.

On the other hand, a thickness gauge is arranged on the exit side of each stand to accurately measure and control the thickness of each stand, or a thickness gauge on the exit side by detecting the speed of each stand. Mass flow AGC that determines the mass flow thickness using the constant law of mass flow based on information from one or more thickness gauges separately installed between them, and controls the roll gap of each stand to keep this at the target value. Is valid.

[0009]

However, the method of arranging a thickness gauge on the exit side of each stand and controlling the thickness of each stand has a problem that a large capital investment is required. In the mass flow AGC, although the capital investment can be suppressed, since the operation is performed only with the roll gap, the mass flow between the stands is disturbed, the looper fluctuates, the tension is fluctuated, and the yield is reduced due to the occurrence of width reduction, There is a problem that hinders the stability of operation.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a method of controlling a thickness of a continuous rolling mill which is excellent in responsiveness and control accuracy and does not cause tension fluctuation. .

[0011]

A first means for solving the above-mentioned problems is that in a continuous rolling mill comprising a plurality of rolling mill stands, a passing speed detector for a material to be rolled installed between the stands is provided. , Using a thickness detector installed on one or more stand exits except for the last stand and a thickness detector installed on the exit side of the last stand, there are both a thickness detector and a sheet speed detector Calculate the volume velocity between the stands
This is set as the reference volume velocity, and based on the law of constant volume velocity, the thickness between each stand is calculated from the reference volume velocity and the plate velocity obtained from the velocity detector arranged between each stand, and it can be obtained simultaneously. Estimate the rolling load, roll gap and main machine speed ratio of each stand to maintain the target plate thickness during rolling using the thickness of the final stand exit side online, and constantly correct the roll gap and main machine speed ratio of each stand. A method for controlling a thickness of a continuous rolling mill (claim 1), wherein a target thickness is achieved by performing the method.

The operation of this means will be described below with reference to the flowchart shown in FIG. First, in step 1,
Each rolling gauge such as a passing speed detector, a rolling load meter, a main machine speed, a roll gap actual value, and the like, which are installed between each stand and each stand, are read. This is a step of collecting data that is a premise of the present invention.

Next, in step S2, the exit plate thickness of each stand is calculated by mass flow calculation. In other words, the mass flow (volume velocity) in the stand provided with both the thickness gauge and the material passing speed detector on the exit side is defined as the reference mass flow, and the passage of the reference mass flow and the material to be rolled on the exit side of each stand. From the output of the speed detector, determine the exit plate thickness of each stand. However, for the final stand only, the exit thickness is determined from the output of the thickness gauge on the exit side of the final stand.

Next, in step S3, the deformation resistance of the rolled material in each stand is determined. This means that the thickness of the entrance side, the thickness of the exit side, and the rolling load of each stand are actually measured.
Since the data necessary for obtaining the deformation resistance such as the roll diameter and the sheet width has been obtained, it can be obtained by a known method.

Next, at step S4, a rolling load for obtaining a target exit plate thickness at each stand, that is, a reference rolling load, is determined. If the deformation resistance is determined, the standard rolling load is
It can be easily obtained by a well-known rolling load equation such as the Sims equation.

Next, in step S5, an error term (correction term) of the gauge meter type is calculated. This is based on the above (1)
In the equation, since the exit side plate thickness, roll gap, rolling load, and mill constant are known, they can be easily obtained.

Next, in step S6, the delivery side plate thickness h
The reference roll gap is determined by substituting the delivery target sheet thickness into (i), the reference rolling load into the rolling load P (i), and the error term obtained in step S5 into the correction term δ (i).

Next, at step S7, the advance rate is calculated based on the measured main machine speed and the output of the passing speed detector for the material to be rolled. Then, the main engine speed is calculated so as to maintain the mass flow balance when the delivery target plate thickness is achieved.

Finally, in step S8, the roll gap of each stand and the main engine speed are corrected based on the values obtained by the above calculations.

If such calculation is always performed from the timing when the rolled material passes through the thickness detector on the exit side of the final stand,
Each stand exit plate thickness can be maintained at the target value, and
The mass flow balance can be kept stable. In addition,
The exit plate thickness (product plate thickness) at the final stand may be controlled by using a conventional monitor AGC. In this case, since the outlet plate thickness of each stand is maintained at the target value, even if the monitor AGC is used, the load does not concentrate on the final stand. At the time of threading before the start of this control, the lock-on AGC or the absolute value AGC
After the main control is started, the control may be performed by the main control.

A second means for solving the above-mentioned problem is as follows.
In a continuous rolling mill composed of a plurality of rolling mill stands, a passing speed detector for a material to be rolled installed between the stands,
Using a thickness detector installed on one or more stand exits except for the final stand and a thickness detector installed on the exit side of the final stand, a thickness detector and a sheet speed detector are both present. Calculate the volume velocity between the stands, define this as the reference volume velocity, and, based on the law of constant volume velocity, calculate the plate velocity between the stands from the reference volume velocity and the plate velocity obtained from the velocity detector placed between each stand. Calculate the thickness, and simultaneously obtain the rolling load, roll gap, and main machine speed ratio of each stand that maintains the target thickness during rolling by using the thickness of the exit side of the final stand that is obtained at the same time, and lock each stand. A method for controlling a thickness in a continuous rolling mill, wherein a target thickness is realized by constantly correcting an on-load, a roll gap, and a main machine speed ratio.

In the first means, while the control according to the first means is being performed, an AGC of a gauge meter system is used.
Had not gone. In this means, the control method of the first means and the AGC of the lock-on method are used together. That is, the present means performs the same processing up to step S7 in the flowchart shown in FIG. 1, but in step S8 not only corrects the roll gap and the main engine speed but also lock-on load (P0 (equivalent to (i)).

Therefore, even if the interval for performing this control based on the mass flow thickness control is lengthened, the lock-on A
GC works to keep the plate thickness constant. Therefore, the load on the computer can be reduced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows Embodiment 1 of the present invention.
In an example, it is a block diagram explaining a method of calculating a board thickness by mass flow. In FIG. 1, 1 is a rolling mill stand, 2 is a steel plate, 3 is a looper, 4 is a thickness gauge between stands, 5 is a thickness gauge on the exit side of the last stand, 6 is a steel plate speedometer, 7
Denotes a reference volume velocity calculation device, and 8 denotes a mass flow plate thickness calculation control device.

FIG. 2 shows a hot rolling mill with seven stands (F1 to F7), and a steel sheet speed gauge 6 is arranged between the stands. The steel plate speed meter 6 may be a non-contact type speed meter such as a laser Doppler speed meter or a contact type speed meter for detecting rotation of the looper 3. Further, in this embodiment, the inter-stand thickness gauge 4 is disposed on the F4 stand exit side, but may be disposed between any stands. However, in order to reduce the accumulation of mass flow errors, it is preferable to provide as close to the central stand as possible.

Between the F4 and F5 stands, the plate thickness,
Since the steel sheet speed can be measured simultaneously, the reference volume velocity mf0 is calculated from the steel sheet velocity v (4) and the sheet thickness h (4) as mf0 = h (4) * v (4)… (4) . This calculation is performed by the reference volume velocity calculator 7. Since the steel sheet speed v (i) at each stand exit side has been detected, using these, the stand exit side sheet thickness h (i) (i = 1 to 6) is given by h (i) = mf0 / v (i) It can be calculated by (5). This calculation is performed by the mass flow thickness calculation control device 8. The F7 stand exit thickness is measured directly by the final stand exit thickness gauge 5.

When the exit plate thickness of each stand is obtained, the deformation resistance of the steel plate at each stand can be obtained by using these values. To find this, a rolling load equation is required. Various calculation formulas have been studied for the rolling load formula. For example, according to the Sims formula in the two-dimensional rolling theory, the rolling load P (i) of the i-stand is

[0028]

(Equation 1)

Is calculated as Here, R 'is the flat roll radius of the work roll, kf (i) is the deformation resistance, Qp is the rolling force function, and B is the sheet width.

Here, since the deformation resistance varies depending on the steel type (component) of the material to be rolled, the temperature, the rolling speed, etc., it is difficult to obtain a correct value in advance. Since it is detected, if the entrance side plate thickness h (i-1) and the exit side plate thickness h (i) of the i stand are known, an estimated value of the deformation resistance kf can be calculated by the following equation. The rolling force function
It is known that Qp (i) is calculated from the work roll radius, the entrance side, and the exit side plate thickness.

[0031]

(Equation 2)

It is known that the deformation resistance is described below based on a study by Misaka et al.

[0033]

(Equation 3)

Where T (i) is the temperature of the material to be rolled on the i stand,
ε and dε / dt are the strain and the strain rate, respectively, and can be calculated from the entry side plate thickness, the exit side plate thickness, R ′, and the rolling speed. Α and β are coefficients calculated from strain and steel type components. Here, if the term depending on the temperature and the steel type component is set as f (T (i)) = exp (A / T (i) + B) (9), an indefinite term can be collected into this term. . Since ε and dε / dt can be calculated from the actual thickness and rolling speed during rolling, this f (T (i))

[0035]

(Equation 4)

It can be estimated that

Therefore, it is possible to estimate a variation term such as a temperature dependency, and by using this, the rolling load for obtaining the target plate thickness hr (i) for each stand by the setting calculation before rolling can be estimated as Pr (i). Then, Pr (i) can be estimated as follows.

[0038]

(Equation 5)

Here, variables with a subscript r indicate numerical values when the target thickness is obtained by the above-mentioned symbols.

On the other hand, the calculation of the error term δ (i) in the gage meter equation (1) is performed by estimating the output sheet thickness h (i) and the observed roll gaps s (i) and P (i). The value Δp (i) can be determined as follows. δp (i) = h (i)-s (i)-P (i) / M (i) ... (12) At this time, the roll gap for obtaining the plate thickness hr (i) of each stand by the setting calculation sr (i) is Pr obtained by equation (12).
It is calculated below using (i). sr (i) = hr (i)-Pr (i) / M (i)-δp (i)… (13)

Here, the roll gap at the time of lock-on is s0
(i), assuming that the rolling load is P0 (i), the roll gap operation amount Δs0 (i) and the load operation amount ΔP0 during rolling to be changed from this state.
(i) is s (i), P (i) to be detected and s calculated by the above calculation.
It can be described by the difference between r (I) and Pr (I). That is, ΔP0 (i) = P (i) -Pr (i) (14) Δs0 (i) = s (i) -sr (i) (15) Therefore, ΔP0 (i), Δs0 (i) If the lock-on load and the lock-on roll gap are changed by using this, the outlet side plate thickness of each stand can be set to the set plate thickness.

By the way, when only the reduction of the stands is performed as described above, the volume velocity between the stands fluctuates.
May cause tension fluctuation. This is usually
Although a minor looper control system that stabilizes the looper angle and the tension works, it is difficult to sufficiently absorb the fluctuation when the thickness deviation at the time of lock-on is large. Therefore, in the present invention, the main machine speed of each stand is simultaneously changed so that the mass flow between the stands becomes constant. At this time, in order for the mass flow to be constant, the plate speed ratio at the outlet of each stand only needs to be the reciprocal of the plate thickness at the outlet of each stand.

The main machine speed vr (i) is set as vr (i) = MRH * ssrh0 (i) * ssrhc (i) (16). Here, MRH is the reference speed, ssrh0 (i) is the speed ratio of each stand main machine to the reference speed MRH, and ssrhc (i) is a speed ratio change term by looper control. Since ssrhc (i) is a term that changes only when the looper fluctuates, it is regarded as 1 and ssrhc (i)
0 (i) may be set to a predetermined value.

At this time, the advance rate of each stand during rolling can be constantly calculated as a ratio between the detected sheet speed and the main machine speed. Therefore, using the reference mass flow mf0 detected on the exit side of the four stands, ssrh0 (i) of each stand
Should be changed to the following values.

[0045]

Ssrh0 (i) = vr (i) / MRH = mf0 / {(1 + f (i)) * hr (i) * MRH} (17) where fr (i) is {v (i) / vr (i) -1}.

As described above, by determining the value of ssrh0 (i), the speed ratio of each stand is always kept close to the ideal state, and the mass flow fluctuation can be minimized.

In the above embodiment, the thickness of the entry side plate of the F1 stand is not actually measured, but is calculated as a gauge meter plate thickness in a rolling mill installed before these rolling mills. Instead of using such a gauge meter plate thickness, an entry-side plate thickness gauge may be provided for measurement. But F
Since the plate thickness on the one-stand entry side is large, sufficient accuracy can be obtained even with the gauge meter plate thickness.

In the above embodiment, the mass flow thickness control is performed using the lock-on AGC, but the thickness control is performed only by the mass flow thickness control without using the lock-on AGC. Can also. In this case, control is performed by operating only the roll gap and the main machine speed.

FIG. 3 shows an example of a control block diagram for realizing the above-described control. FIG. 3 is for controlling the F5 stand. 3, the same reference numerals are given to the components shown in FIG. 2 and the description is omitted. In FIG. 3, reference numeral 9 denotes a pressure reduction control device, and 10 denotes a main engine control device.

As described above, the reference volume velocity calculating device is:
Output h4 of thickness gauge 4 between stands and output of speedometer between stands
Input V4 to calculate the reference volume velocity. The mass flow thickness calculating and controlling device 8 includes an output V4 of the inter-stand speedometer,
In response to the output of the rolling load meter, the output of the rolling position (roll gap), etc., the roll gap change value ΔS5 and the main machine speed change value ΔV5 are obtained by the above-described procedure and output to the rolling reduction control device 9 and the main machine control device 10, respectively. I do. Lock on AG
In the case where C is used in combination, a lock-on load change value is also obtained, and a reduction control device (including a lock-on AGC device) 9
Output to

[0051]

As described above, according to the first aspect of the present invention, the thickness of each stand outlet can be maintained at the target value, and the mass flow balance can be maintained stably. .

According to the second aspect of the invention, in addition to this, the load on the computer can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining the operation of the present invention.

FIG. 2 is a block diagram illustrating a method for calculating a plate thickness by mass flow in one example of an embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a control block for implementing control according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rolling mill stand 2 ... Steel plate 3 ... Looper 4 ... Stand thickness gauge 5 ... Final stand exit side thickness gauge 6 ... Steel plate speed meter 7 ... Reference volume velocity calculation device 8 ... Mass flow plate thickness calculation control device 9 ... Reduction control Device 10: Main engine control device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Wang Country 1-1-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) in Nihon Kokan Co., Ltd. 4E024 AA07 CC01 CC02 CC03

Claims (2)

[Claims] In a continuous rolling mill comprising a plurality of rolling mill stands, a passing speed detector for a material to be rolled installed between the stands and one or more stand excluding the last stand are installed. Using the thickness detector and the thickness detector installed on the exit side of the final stand, calculate the volume velocity between the stands where both the thickness detector and the velocity detector are present, and use this as the reference volume velocity. Based on the law of constant volume velocity, the plate thickness between each stand is calculated from the reference volume velocity and the plate velocity obtained from the velocity detector placed between each stand, and the sheet thickness on the final stand exit side obtained simultaneously. Estimate the rolling load, roll gap and main machine speed ratio of each stand that maintains the target plate thickness during rolling online, and constantly correct the roll gap and main machine speed ratio of each stand to achieve the target plate thickness. Specially A method for controlling the thickness of a continuous rolling mill. 2. In a continuous rolling mill comprising a plurality of rolling mill stands, a passing speed detector for a material to be rolled installed between each stand and one or more stand excluding the last stand are installed. Using the thickness detector and the thickness detector installed on the exit side of the final stand, calculate the volume velocity between the stands where both the thickness detector and the velocity detector are present, and use this as the reference volume velocity. Based on the law of constant volume velocity, the thickness of each stand is calculated from the reference volume velocity and the plate velocity obtained from the velocity detector arranged between each stand, and the thickness of the final stand exit side obtained simultaneously. Estimating the rolling load, roll gap, and main machine speed ratio of each stand that maintains the target plate thickness during rolling online, and constantly correcting the lock-on load, roll gap, and main machine speed ratio of each stand to achieve the target plate Thick A method for controlling a thickness of a continuous rolling mill, which is realized.