JPS5847245B2 - Keijiyouseigiyosouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to shape control of hot rolled steel sheets, and more particularly to a shape control device that provides rolled steel sheets with good shapes.

Conventionally, temperature control of hot-rolled steel sheets has mainly focused on finishing temperature and coiling temperature in the longitudinal direction of the steel sheet.

Recently, there has been a report stating the need for temperature control in the width direction of steel plates, and the purpose of temperature control is to improve the physical properties of the steel plate, as in the longitudinal direction.

Although the present invention is aimed at shape control, the shape detector has been a bottleneck in conventional shape control.

Regarding shape detectors, various methods have been proposed and reported as shape control systems, but the detectors are expensive and there are problems with the performance of the detectors, so that they have not been fully put into practical use.

SUMMARY OF THE INVENTION An object of the present invention is to provide a shape control device that controls the temperature of a hot-rolled steel sheet in the width direction to obtain a steel sheet with a good shape.

The present invention predicts the shape of a hot rolled steel sheet by measuring the temperature in the width direction of the hot rolled steel sheet, and controls the shape by controlling control devices such as a roll bending device and a roll coolant device to produce a steel sheet with a good shape. obtain.

Regarding calculation of rolling load during hot rolling, equation (1) is well known.

p=ni-b-J'Fe・J h-QP...
...(1) P: Rolling load, R': Flat roll diameter = plate width, Ah Nidraft: Deformation resistance, QP: Load correction coefficient The deformation resistance in the rolling load formula is a function as shown in equation (2). It is also well known that it is expressed.

k=ko ・5 n-(5)m-exp ()”=(
2) k Os n s rns α: Constant, ε: Strain, ε
: Strain rate T: Temperature, that is, deformation resistance is a function of temperature, and by knowing the temperature, the load P can be calculated.

In commonly used computer control, the load is predicted by measuring the temperature of the steel plate.

In this case, the temperature is detected only at one point in the width direction of the steel plate.

Therefore, by measuring the temperature along the width direction of the steel plate, the rolling load in the width direction can be calculated.

There is a close relationship between the shape of the steel plate during rolling and the rolling load in the width direction.

Normally, in shape control analysis, the amount of bending of rolling mill rolls is calculated.

The mechanical equation regarding the bending of the roll is expressed by equation (3).

d'y P 1 d2p(x)=-
+ ・□・・・・・・(3) dX4 E-I
α・G-A dX2 y: Amount of bending of the roll axis Correction value for using the average value of shear force for a÷-2 circular cross section G: Roll modulus of transverse elasticity A: Roll cross-sectional area p(x): Rolling load distribution in the roll axis direction Solving equation (3) It is sufficient to give the load distribution p(X) and the boundary conditions.

A flowchart of the method for solving equation (3) is shown in FIG.

FIG. 1 shows the state of bending of the rolls when rolling a steel plate in a quadruple rolling mill.

In FIG. 1, the X-axis is a coordinate in the direction of the roll axis, and the y-axis is a coordinate indicating the amount of bending of the roll axis.

When the steel plate 3 is being rolled by the upper and lower work rolls 2 and 4, a load distribution of PL occurs between the steel plate 3 and the upper work roll 2.

At the same time, a load distribution of P2 is generated between the upper work roll 2 and the upper reinforcing roll 1.

Although not shown in FIG. 1, the same load distribution occurs on the lower work roll 4 and the lower reinforcing roll 5.

In the figure, P indicates a rolling blade detected by a load detector, and F indicates a roll pending force applied between the upper and lower work rolls.

P1■ indicates the load distribution per unit length in the width direction,
Assuming that ptω is a constant value p1, b-pl is the force acting between the steel plate and the work roll.

In Figure 1, considering the balance of forces, P-F=b
-pl (However, Pl (effect=p1), but since pl(x) is generally a function of X, it can be expressed as in equation (4).

b P-F=f 2p1(x)dx・・・・・・・・・・
...(4) 1°, where b: plate width p□ (X) can be determined by knowing the temperature distribution in the width direction of the steel plate.

That is, in equation (1), P/b=Kv'R'-J
Since h-QP expresses the load per unit length in the width direction,
Considering that the deformation resistance K is a function of the temperature T as shown in equation (2), pt(x) is pt(x)=KJR'・Jh −QP...
・−(1) 'α=Ko°ε0°−, exp , , , , , , ,
, , , (2)/T(x).

In addition, p2(X) indicates the load distribution between the work roll and the reinforcing roll, and considering the balance of forces as described above, (5
) can be expressed as follows.

L P=f2P2(x) dx・・・・・・・・・(5)L Matadashi, L: Long roll body, 0) In the formula, the expressions for 1 -b, -b are as follows: 2. This is because the center point in the board width direction is set as the coordinate origin in the X direction.

That is, as is clear from FIG. 1, the coordinate origin O of the steel plate in the width direction It is expressed as b.

Similarly, 2 1 The expressions 1L and --L in equation (5) are the roll body length 2 Set the center point of L as the coordinate origin in the X direction, and set the left and right mouth 1 This is due to the fact that the trunk length is expressed as -L and -L.

2 Now, the amount of bending of the roll is determined by the given load distribution p□
It is obtained by applying (X) to the equation (3)-<5), and it is obtained by varying the value of the roll pending force F.

The same applies to the amount of roll crown.

The optimum relationship between roll crown amount and roll bending shall be determined by determining a shape evaluation formula.

The evaluation of the shape shall be performed as follows.

That is, in equation (3), the distribution of the amount of bending y of the roll axis in the X direction is y■, and y(x) corresponding to the point where X=O (center point) is y(0).

A good shape means that there is no bending of the roll axis or the bending is small, so if we express this in an evaluation formula, the bending amount y(0) at the point X=O and the
The deviation y(
0)-y(x) is 0 or a very small value, it is considered to be a good shape.

To perform this evaluation from X=O to the end of the roll, integrate along the length of the roll body, and find the smallest value i (y(x)).
Determine.

Since the deviation of h, y(0)-y(X) can be positive or negative, using the evaluation function that minimizes the squared deviation yields the following equation.

2L 1=-1・'x” (y(0)-t(・)]・d...
(6) Using this evaluation formula to determine the rolling load, the optimum roll pending force for that rolling load can be determined as follows.

FM = a − P + c ・I (: r ””
(7) However, FM: Optimal roll pending force a, c: Coefficient that is a function of plate width Icr: Roll initial crown The function of equation (7) is shown in FIG.

As described above, if the rolling load P(x) is determined, the roll pending force to be controlled can be determined.

Therefore, it is necessary to know the temperature distribution in the width direction and predict the load distribution.

Heat transfer science teaches that the temperature distribution in the width direction of a heat source with a finite width, such as a rolled material, can be approximated by a quadratic curve as shown in FIG.

That is, if the temperature in the width direction of the steel material is T, then T=T s o -
d−x2=・・・・・・・・・(8) Tso: Surface temperature at the center of the steel material width d: Coefficient X: Distance from the width center temperature T.

and temperature changes due to water cooling, air cooling, and processing after exiting the furnace.

When the steel material comes out of the furnace, it is uniformly heated in the furnace, so the entire steel material is at the initial temperature To, but when placed on the rolling line, the surface and interior of the steel material are also at the initial temperature To, as shown in equation (8). It has a temperature distribution.

That is, the coefficient d in equation (8) is a time function like Tso, and if water cooling, air cooling, and processing are uniform in the left and right width directions of the steel material, it can be considered as a time function with respect to the surface temperature Tso at the center of the width.

At the stage where rolling has progressed to a certain extent, the temperature difference between the width center and the edge can be said to be a function of time and is no longer 20 to 40℃.
It can be considered that the degree is constant.

Also, there is no difference depending on the thickness of the steel material.

The object of the present invention is to obtain an i-rolled material with a good shape by rolling the steel material so that the distribution of the rolling temperature in the width direction becomes a quadratic equation such as equation (8).

Shape defects caused by hot rolling will not occur if rolling is performed with uniform temperature distribution in the width direction.

The causes of uneven temperature distribution are uneven water cooling,
There is uneven roll bending.

Normally, water cooling is controlled uniformly, but the result may be non-uniform.

Furthermore, since the material is directly processed with respect to the bending of the roll, defects in the shape of the roll have a large effect.

The shape of the roll is usually provided with an initial crown for the purpose of shape control.

This initial crown changes with the progress of rolling of the steel material, thermal expansion of the roll, and wear of the roll.

Also, roll thermal equilibrium differs depending on the left and right sides of the roll.

This is because the motor system is connected to the 7-drive mechanism of the roll, and heat dissipates quickly.

Due to these various reasons, the shape of the roll changes over time, and the shape of the rolled material during rolling also changes.

For this purpose, a roll bender and roll cooler flow rate control are used as control means.

Roll bender control involves knowing the load distribution from the temperature distribution of the steel material and setting the optimum roll pending force for a good shape.Roll coolant control involves adjusting the width direction to eliminate left and right unevenness in the temperature distribution of the steel material. It is to control the flow rate.

FIG. 5 shows the principle of temperature detection in the width direction of the present invention.

FIG. 5a shows the screen of a thermo camera that measures the temperature distribution of an object. Although not indicated in the figure, the temperature distribution of the steel material is shown in brightness and darkness, similar to a black and white television.

The pixels of a thermo camera are based on the same principle as that of a television, and A in the figure indicates the position at which the image is scanned in the horizontal direction.

This scanning position is fixed, and each time a scan is performed, a signal indicating a temperature distribution waveform as shown in the figure is obtained.

Although this scanned waveform is depicted as continuous in the figure, it is actually a signal for each pixel and is a discontinuous amount.

Normally, the number of pixels is fixed and is about 400, but about 20 pixels is sufficient for the detection amount, and one pixel among the 20 pixels divided into 20 pixels is selected as the representative temperature of that section.

Then, from among the selected 20 pixels, n pixels corresponding to the width of the steel material are used to grasp the temperature distribution of the selected steel material.

FIG. 6 shows an embodiment of the present invention.

When the material 23 reaches the thermo camera 9 installed in front of the rolling mill, the temperature distribution of the material is immediately sent to the computer 17 through the image converter 16.

The computer 17 immediately presets the number of sampling pulses in the counter 20.

The preset counter 20 counts the pulses output from the pulse transmitter 14 attached to the lower work roll 13, and when it counts to the preset value 1, it sends a count end signal to the calculator 17 and starts counting again.

The computer 17 outputs the image converter 1 according to the force and runt end signals.
A signal indicating the temperature distribution on the screen is acquired from 6.

FIG. 7 shows a flowchart of the subsequent processing within the computer 17.

In block 110 of the figure, first, the average temperature TM of the steel material is determined.

TM is n TM =, jX:, T i""° (9) However, Tj
: Temperature n in the j-th section in the board width direction (j is an integer of 1 - j≦n): Number of section divisions in the board width direction j: Indicates each section in the board width direction, corresponding to The reason for this distinction is that j is discrete.

Using TM, the rolling load P is determined by the above-mentioned equations (1) and (2).

Next, in block 120, pl (x)(pt (j
)).

pl (x) is the temperature T(x)(T
j) to calculate the load per unit width as described above (IL (2)
It can be found using K.

In block 130, the amount of roll bending y(X) is determined.

The method of determination follows the flow shown in Figure 2.

In block 140, the optimal roll pendency is determined using equation (6).

In block 150, the amount of roll cooling water in the width direction is determined.

The calculation method is to calculate the temperature at each point in the width direction using equation (8), and by setting this as Tj, the cooling water flow deviation JQ at the j-th division point is determined using the following equation.

JQ, = (T, -TM) demand.

n β=q/[-(Σ(T,-TM))] ・・・・・・11
n j = 1 Here, it is convenient to find β in advance by experiment.

The roll cooling water amount Qn is determined by adding JQn to the reference cooling water amount Qon.

That is, 12 formula % formula % (12) It can be expressed as

By the above method, the roll pendency and roll cooling water amount are determined as shown in the flowchart of FIG.

These values are determined by the roll bending control device 18 and the roll bending control device 18 through delay circuits 21 and 22, which delay the time for the material 23 to travel the distance between the thermo camera 9 and the center axis of the upper work roll, respectively, as shown in FIG. Cooling water control device 19
can be conveyed.

The roll bending control device 18 applies force to the roll chock 24 so as to reach this value.

Further, the roll cooling water control device 19 is installed on the front and rear surfaces of the upper work roll, and further controls so that a predetermined amount of cooling water Qn is discharged from the cooling water nozzles 10.11 each having n nozzles in the width direction.

Therefore, when one point of the steel material whose temperature is measured by the thermo camera 9 reaches the rolling mill, processing conditions have been established in which the steel material can be rolled with a uniform temperature distribution, and a steel plate with a good shape can be rolled. Ru.

This control is performed every time the counter finishes counting, and is performed over the entire length of the material 23.

In this example, a thermometer is installed in front of the rolling mill, and the output of this thermometer is used to determine the rolling load distribution at each point in the strip width direction.
This is a feedforward system that uses this for control.

In the case of this feedforward method, the result is predicted, the control amount is determined and controlled so that the result becomes the desired state, so the predicted physical quantity or the result calculated using the physical quantity ( predicted values) are not necessarily accurate.

Therefore, in this embodiment, the roll cell 15 is installed, the actual rolling load P is input into the calculator 17, and the
It is possible to verify how much the rolling load predicted by 7 differs from the actual rolling load, or in other words, how accurate the prediction is.

As a result of this verification, if the predicted value and the actual rolling load are significantly different, the well-known adaptive correction control technique can be used to accurately predict the subsequent rolling load.

In the example, a method was described in which a thermometer was installed in front of the rolling mill to perform feedforward, but a method in which a thermometer was installed at the rear of the rolling mill to perform feedback, a combination of feedforward and feedback, etc. are similar. Can be configured.

As described above in detail, the present invention enables shape control without directly detecting the shape, and can be expected to produce products easily and with high precision.

[Brief explanation of drawings]

Figure 1 is a diagram showing the bending state of the roll, Figure 2 is a diagram showing the flow for calculating the amount of roll bending, Figure 3 is a diagram showing the relationship between the optimum roll pendency and rolling load, and Figure 4 is a diagram showing the relationship between the optimum roll bending force and rolling load.
Figure 5 shows the surface temperature distribution of steel material, Figure 5 shows the principle of detecting temperature distribution in the width direction, Figure 6 shows an embodiment of the shape control device according to the present invention, and Figure 7 shows shape control. It is a figure which shows the flow which performs. 1...Top reinforcement roll, 2...Top work roll, 3...
- Steel plate, 4... Lower work roll, 5... Lower reinforcing roll, 9... Thermo camera, 10... Cooling water nozzle, 1
1... Cooling water nozzle, 12... Upper work roll, 13
...Lower work roll, 14...Pulse transmitter, 15.
... Load cell, 16... Image converter, 17... Computer, 18... Roll bending control device, 19.
... Roll cooling water control device, 20 ... Counter, 21
... Delay circuit, 22... Delay circuit, 23... Rolled material, 24... Roll chock.

Claims (1)

[Claims] 1. A temperature detector that detects the temperature distribution in the width direction of the steel material;
A calculation device that calculates the load distribution in the width direction of the steel material based on the output of the temperature sensor, and a control device that controls the optimal roll bending device and the amount of roll cooling water based on the output of the calculation device. A shape control device characterized by making the shape good.