JPS63188417A - Control method for plate thickness in rolling mill - Google Patents

Abstract

PURPOSE:To perform the high accurate and stable control by calculating a drafting position correction amount by use of an intermediate value between a mill rigidity modulus value corresponding to a rolling load lock-on value and a mill rigidity modulus value corresponding to a detected rolling load value during rolling as a mill rigidity modulus for control. CONSTITUTION:A load cell 2a detects a rolling load P and outputs the load P to an arithmetic controller 3, which stores a relation between a rolling load P determined by previous actual measurement and a mill rigidity modulus M into the memory of the controller 3. A circuit 3a reads out a rigidity modulus corresponding to a lock-on rolling load from the memory at a start of rolling and outputs the modulus as a mill rigidity modulus Mc for control. At the time when a load is changed from the lock-on point during rolling, a rigidity modulus corresponding to a rolling load at that moment is read and outputs an intermediate value between the read modulus and the Mc at the lock-on moment as a mill rigidity modulus Mc for control. An arithmetic circuit 3c calculates a drafting position correction amount S1 based on respective outputs of Mc and P from the circuits 3a, 3b and uses the amount S1 in a stand 2.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a method for improving the thickness of a rolling mill that maintains the thickness of a plate material after rolling at a predetermined value by correcting and controlling the rolling position during rolling of a steel plate, etc. Concerning control'a method. In particular, by always accurately determining the current value of the mill stiffness coefficient that changes during rolling, highly accurate and stable control can be achieved. The present invention relates to a method for controlling plate thickness of a rolling mill that achieves B.

(Prior Art) The thickness of a steel plate or the like at the exit side during rolling is generally expressed by the following formula (Z) using a gauge meter formula.

h=s+ (P/M)...(1) However, h: Output plate thickness S: Roll gap (rolling position) at no load P; Rolling load M: Mill rigidity coefficient.

Further, the exit side plate thickness deviation Δh during rolling when based on the lock-on time is expressed by the following equation (2).

Δh attack ΔS+(ΔP/M)...(2) However, ΔS tonnage 33 (1 Δp=p-pe Δh-h-h.

So, Po, and ha are the rolling position, rolling load, and exit side plate thickness at the reference time (lock-on time), respectively.

In automatic plate thickness control using a gauge meter, the plate thickness deviation Δh is detected using equation (2), and the rolling position is corrected and controlled so that this deviation approaches zero. The reduction position correction command amount ΔSr at this time is generally given by the following equation (3).

ΔSr−-KA·(ΔP/M) (31 Here, Km is a scale factor gain, and is preferably Ka″1 in terms of plate thickness control accuracy.

However, due to the need to perform stable control against various disturbances,
Control is performed by setting the value to be as large as possible within the range <1.

Further, M()n/-resistance is the mill rigidity coefficient, and is a parameter indicating the change in rolling load with respect to the elongation of the mill. Therefore, the term 8P/M in the right-hand side of equation (3) is the change in rolling conditions, for example, the change in the entrance plate thickness H1, the plasticity coefficient Q of the rolled material
It shows the amount of elongation of the mill due to load fluctuation ΔP caused by changes in .

The reason why the plate thickness deviation Δh can be brought closer to zero and the plate thickness can always be maintained at approximately a predetermined value by correcting the rolling position using equation (3) is as follows.

FIG. 2 is a graph showing the relationship h-3+ (P/M)...+11 between the thickness of the exit side plate and the rolling load P when the rolling position is constant. In Fig. 2, in the reference state A at the lock-on point, the entry side plate thickness is He, the rolling position is So, and the rolling load is P.
o, and the outlet side plate thickness is ho. Here, for the reference state a80, the entrance side plate thickness H.

When increases by ΔH, the load increases by ΔP and the outlet plate thickness increases by Δh, shifting to the state ta A+.

At this time, if ideal plate thickness control is performed and the rolling position is corrected by ΔS from S, then A! The state shown in is reached, and the rolling load at this time is P2.

The reduction position correction command amount ΔSr in automatic plate thickness control using a gauge meter type is calculated by equation (3) as described above. In the past, the value of the mill rigidity coefficient M used in equation (3) was often fixed to a value set when the rolled material was bitten. However, the mill stiffness coefficient M is a quantity that depends on the magnitude of the rolling load P. For this reason, the value of M used to calculate the reduction position correction amount ΔSr in equation (3) becomes inaccurate, and the accuracy of plate thickness control deteriorates.

In order to improve the accuracy of plate thickness control while keeping the mill stiffness coefficient M fixed, for example, Japanese Patent Application Laid-Open No. 60-9512 has already proposed a method that uses a method to calculate the reduction position correction amount in accordance with fluctuations in the rolling load P. We propose to change the value of the coefficient M.

(Problems to be Solved by the Invention) The control method proposed in this publication has improved control accuracy compared to the previous control method in which the mill stiffness coefficient M remains fixed. However, even with the method disclosed in this publication, the value of the mill rigidity coefficient M used to calculate the amount of correction of the rolling position is still inaccurate, and a considerable error is involved in calculating the amount of command for correction of the rolling position ΔSr or the deviation between plates Δh.

The reason why the plate thickness deviation Δh cannot be calculated accurately even with the control method of changing the coefficient M according to the above-mentioned publication will be explained next with reference to FIG.

When the rolling load increases from Po to P+ by ΔP from standard state A to state A, the actual plate thickness deviation is Δh (Δh−
ΔP/Mc), but in the conventional method such as that of the publication,
The slope of the tangent to the mill stiffness characteristic curve at the rolling load value P during rolling is defined as the mill stiffness coefficient M1 for calculating the control amount.

However, the detected plate thickness deviation calculated using this coefficient M+ is Δh' (Δh゛=ΔP/M + ), and Δh>Δh'' with respect to the actual deviation Δh, that is, the mill stiffness coefficient is overestimated. Therefore, the calculated plate thickness deviation and reduction correction amount become too small, and the plate thickness control accuracy decreases.

On the other hand, if the rolling differential load P decreases with respect to the standard state A, contrary to the above explanation, the mill stiffness coefficient will be underestimated. As a result, the amount of reduction correction becomes excessive. Therefore, not only the accuracy of plate thickness control is reduced, but also the control becomes unstable in some cases, which may impede the rolling operation itself. For this reason, we have to set it to a low value with a safe margin. This further deteriorates control accuracy.

Therefore, an object of the present invention is to improve control accuracy and control stability in the conventional method described above, by successively and accurately determining the mill stiffness coefficient according to rolling conditions, especially changes in rolling load, so as to obtain an optimal gain. An object of the present invention is to provide a method for controlling plate thickness of a rolling mill that enables control of the thickness of a rolling mill.

(Means for Solving the Problems) Thus, the gist of the present invention is to detect the rolling load during rolling, obtain the plate thickness deviation, and correct and control the rolling position so that the plate thickness deviation approaches zero. In the automatic plate thickness control method, the relationship between rolling load and mill stiffness coefficient is determined in advance by actual measurement, and at lock-on, the value of the mill stiffness coefficient corresponding to the rolling load lock-on value in the above relationship is used as the mill stiffness for control. After lock-on, the intermediate value between the value of the mill rigidity coefficient corresponding to the rolling load lock-on value and the value of the mill rigidity coefficient corresponding to the rolling load detection value during rolling in the above relationship is used as the mill rigidity coefficient for control. Calculating the reduction position correction amount as
This is a method for controlling plate thickness of a rolling mill, which is characterized by the following.

(Effect) The control mill rigidity coefficient used to calculate the rolling position correction amount is:
Using the relationship between the rolling load and the mill rigidity coefficient determined experimentally in advance, the mill rigidity coefficient during rolling is determined as the intermediate value between the mill rigidity coefficients corresponding to the rolling load detection value at lock-on of the rolling load and during rolling. The intermediate value is used here in the following meaning. Third
In the mill stiffness characteristic curve shown in the figure, the mill stiffness coefficient corresponding to the rolling load lock-on value P0 is Mo, and the mill stiffness coefficient corresponding to the rolling load detection value P1 during rolling is M
, but the intermediate value Mc of these mill stiffness coefficients M0 and M is two points A corresponding to the rolling loads P0 and P on the mill stiffness characteristic curve. , A, is the value supported by the slope of the chord (straight line) connecting .

Therefore, the reduction position correction amount calculated using this controlling mill rigidity coefficient accurately corrects the plate thickness deviation even during rolling.

(Example) Next, an example of the present invention will be described in detail with reference to FIG. 1 and FIG. 4.

FIG. 1 is a block diagram of a control system for controlling the thickness of a rolled plate by the plate thickness control method of the present invention.

The steel plate 1 is rolled into the entry side plate r! by the rolling mill stand 2. It is rolled from I-H to the thickness of the exit side. The load cell 2a detects the rolling load P and outputs it to the arithmetic and control device 3.

The arithmetic and control device 3 stores in its memory the relationship between the rolling load P and the mill stiffness coefficient M, which has been determined in advance through actual measurements.

FIG. 4 is a graph showing the relationship between the rolling load P and the mill stiffness coefficient M (PM characteristic) determined by this actual measurement. The mill stiffness characteristics shown in the mill stiffness characteristic curve in Figure 3 were determined by actual measurements in a roll kiss state before rolling operation.
Find the mill stiffness coefficient at that point from the slope of the tangent at each load. Next, the relationship between the rolling load MP and the mill stiffness coefficient M shown in FIG. 4 is calculated as a PM characteristic and stored in advance in the memory of the circuit 3a of the arithmetic and control unit 3.

The circuit 3a has a coefficient M corresponding to the lock-on rolling load P0 in the relationship shown in FIG. 4 (P-M characteristic) at the start of rolling.
is read from the memory and used as the control mill stiffness coefficient Mc
Output as . Also, if the load P changes from the lock-on point P0 during rolling, the coefficient M corresponding to the rolling load P at that point is read out, and the intermediate value between Mo and Mo at the time of lock-on is used as the control mill rigidity coefficient Mc. Output. The intermediate value is used here in the following meaning. In the mill stiffness characteristic curve shown in FIG. 3, the rolling load lock-on value P.

The mill rigidity coefficient corresponding to is Mo, and the mill rigidity coefficient corresponding to the rolling load detection value P during rolling is MI,
The intermediate value Mc of these mill stiffness coefficients Mo, M is:
It refers to the value supported by the slope of the chord (straight line) connecting the two points As and A+ corresponding to the rolling load P and Pl in the mill stiffness characteristic curve. Note that the circuit 3a operates in the same manner as in the above-mentioned lock-on during re-lock-on.

The circuits 3b and 3C in the arithmetic and control device 3 are the rolling load P0 and the rolling position S at the reference time (lock-on time).

Then, the differences ΔP and ΔS between the rolling load P and the rolling position S during rolling are calculated, respectively.

The arithmetic circuit 3d receives the outputs Mc and ΔP1ΔS of the circuits 3a to 3C.
The plate thickness deviation Δh is calculated based on the following formula.

Δh Hatake ΔS+(ΔP/Mc) (4) Also, based on the outputs Mc and ΔP of the circuits 3a and 3b, the arithmetic circuit 3e calculates the reduction position correction amount ΔS1 using the following formula using an appropriate scale factor gain KA. calculate.

ΔS1 Volume - (ΔP/Mc)...(5) The correction amount ΔSI calculated above may be used as it is as the reduction position correction command amount to the stand 2, but the monitor control pressure reduction correction command amount may also be used as it is. Adding ΔS□, ΔSs”ΔS1 +ΔS! (It is preferable to use the amount ΔS given by η as the reduction position correction command amount.

(Effects of the Invention) According to the present invention, the relationship between the rolling load and the mill rigidity coefficient can be determined in advance by actual measurement, and using this relationship, the mill rigidity coefficient that changes during rolling can be accurately evaluated as the mill rigidity coefficient for control. The scale factor gain KA in gauge meter type automatic plate thickness control can be set to a value closer to 1 than in the past, improving plate thickness control accuracy and increasing control stability.

Therefore, it is effective not only to improve the accuracy of plate thickness but also to prevent a decrease in efficiency due to work interruptions, etc.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a control system for carrying out the control method according to the present invention; Fig. 2 is a graph showing the principle of determining the reduction position correction amount in plate thickness control; Fig. 3 is a diagram of the conventional control system. A graph for explaining the error that occurs in calculating plate thickness deviation based on the calculation mill stiffness coefficient; and Fig. 4 shows the relationship between the rolling load and the mill stiffness coefficient (P-M characteristics) used in the control system of Fig. 1. ). l:t! j4 plate 2: Rolling mill stand 3: Arithmetic control device

Claims (1)

[Claims] In an automatic plate thickness control method that detects a rolling load during rolling to obtain a plate thickness deviation, and corrects and controls a rolling position so that the plate thickness deviation approaches zero, the rolling load and mill rigidity coefficient are determined in advance. Determine the relationship by actual measurement. At the time of lock-on, the value of the mill rigidity coefficient corresponding to the rolling load lock-on value in the above relationship is used as the mill rigidity coefficient for control, and after lock-on, the rolling load in the above relationship is determined. Calculating the reduction position correction amount using the intermediate value of the mill rigidity coefficient corresponding to the lock-on value and the mill rigidity coefficient corresponding to the rolling load detection value during rolling as a control mill rigidity coefficient. A method for controlling plate thickness in a rolling mill.