JPH08332507A - Method for controlling thickness of taper plate - Google Patents

Abstract

PURPOSE: To obtain a taper plate having the target gradient from one end toward the other end in the longitudinal direction. CONSTITUTION: This method is based on a method for controlling a roll gap based on the deviation between an estimated rolling load and a measured rolling load. In the process where the target taper thickness on the outlet side is changed according to rolling length, based on the target taper amount ΔH<0> on the inlet side and target taper amount Δh<0> on the outlet side which are set with a target taper amount setting 11, mill stiffness coefficient M which is set with a constant setting 12, plasticity coefficients Q, Q' of a material 6 to be rolled and scale factor KA. which is the gain of a thickness control system, the target changing amount ΔhT** of taper thickness on the outlet side is used correcting the target changing amount ΔhT of taper thickness on the outlet side with a target outlet-side taper thickness changing amount setting 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called taper plate whose thickness changes substantially continuously from one end in the longitudinal direction of a material to be rolled to the other end by using an ordinary rolling mill for steel plates (flat plates). The present invention relates to a plate thickness control method for rolling a steel sheet.

[0002]

2. Description of the Related Art Usually, the plate thickness control in flat plate rolling is a basic relation expressed by the following formula (1), which is established between a rolling load P, a roll gap S of a rolling roll, and a delivery side plate thickness h of a rolling mill. Is based on. h = S + (P / M) (1) where M: mill rigidity coefficient

Equation (1) is an equation that always holds in the state during rolling, but in the predictive calculation before biting of the material to be rolled, in order to obtain the target delivery side plate thickness h ₀ , the following equation similar to equation (1) is used. The roll gap S ₀ is set based on the predicted rolling load P ₀ using the equation (2). h ₀ = S ₀ + (P ₀ / M) (2)

Then, the outlet plate thickness h obtained by the equation (1)
The roll gap S is controlled according to the following equation (3) in order to match the target delivery side plate thickness h ₀ obtained by the equation (2). S = S ₀ − (1 / M) · (P−P ₀ ) ... (3)

Equation (3) is a control method generally called "absolute value AGC" and is widely used for plate thickness control of flat plate rolling. As a technique for applying this to plate thickness control of taper plates. In the past, for example, JP-A-51-9
Japanese Patent No. 7565 proposes a method shown in the equation (4) in which the output side target plate thickness value is changed from moment to moment in accordance with the equation (3).

S = S ₀ − (1 / M) · (P−P ₀ ) + Δh _T (4) where Δh _{T is} a target outlet taper plate thickness change corresponding to the rolling length based on the biting end. In addition, in Japanese Patent Application No. 6-225439, in order to prevent the control system from becoming unstable due to the influence of mill hysteresis, a scale factor K _A that is the gain of the plate thickness control system is used in the absolute value AGC. In order to obtain the target taper plate thickness also in the case of, the method of controlling the roll gap S according to the formula (6) is introduced by introducing the target output side paper thickness change amount Δh _T * given by the formula (5). Proposed.

[0007]

[Equation 1]

By setting the roll gap S according to the equation (6), the scale factor K _A is 1.0.
Even if it is smaller, the output side plate thickness is made to match the target output side taper plate thickness. By the way, if the equation (6) is replaced with ΔS = S−S ₀ and ΔP = P−P ₀ , the plate thickness control system according to this method is shown in FIG. FIG.
FIG. 6 is a block diagram showing the control contents of a taper plate thickness control system described in Japanese Patent Application No. 6-225439. In the plate thickness control system shown in FIG. 3, the target output side taper plate thickness change amount Δh _T is a plate thickness target value gain η expressed by the following equation.

[0009]

[Equation 2]

By multiplying by the target output side taper plate thickness variation Δh _T
* Is obtained, and a value obtained by multiplying the rolling load change amount ΔP (= P−P ₀ ) by the coefficient K _A / M is subtracted from this, and the result is given to the roll gap position control system. The roll gap position control system outputs the roll gap change amount ΔS (= S−S ₀ ) to the addition point. A value obtained by multiplying the rolling load change amount ΔP obtained from the roll gap change amount ΔS by 1 / M and the roll gap change amount ΔS are added at the combining point, and the following (7)
The outlet side plate thickness change amount Δh given by the formula is obtained.

[0011]

(Equation 3)

In the equation (7), when the change amount ΔH _T of the entrance side taper plate thickness is 0, that is, when the entrance side plate thickness is a flat plate, Δh = Δh
_It becomes _T , and the delivery side plate thickness matches the target delivery side taper plate thickness.
Therefore, if the same taper amount (difference in wall thickness at both ends) as that of the final product can be applied by rolling in one pass from a flat plate, Japanese Patent Application No.
The method of No. 439 causes no practical problem.

[0013]

However, it is generally impossible to give a required taper amount in one pass because of restrictions on the rolling mill equipment such as maximum rolling load and torque. There is no choice but to sequentially apply the taper amount separately for each.

In this case, in the second and subsequent rolling passes, since the inlet side plate thickness changes in a taper shape in the longitudinal direction of the material to be rolled, the inlet side taper plate thickness change amount ΔH _T does not become 0, and as described above. Scale factor K _{A that is} the gain of the plate thickness control system
When is less than 1.0, Δh ≠ from the relationship of equation (7).
There is a problem that Δh _T results and the output side plate thickness cannot match the target output side taper plate thickness.

If the scale factor K _A, which is the gain of the plate thickness control system, can be set to 1.0, as can be seen from the equation (7), the output side plate thickness always matches the target output side taper plate thickness, but generally the control system is There is a unavoidable condition that K _A <1 in order to secure the stability of the rolling stock. Therefore, the strip thickness on the delivery side includes the value of the scale factor K _A , the mill rigidity coefficient M, the plasticity coefficient Q ′ of the material to be rolled, and the like. Gain of plate thickness control system and amount of change in taper plate thickness on inlet side Δ
Due to the influence of H _T, the taper plate thickness deviates from the target exit side taper plate thickness.

The present invention has been made in view of the above circumstances, and its object is to provide a large taper amount,
If it is necessary to perform rolling in multiple passes by a rolling mill to form a predetermined amount of taper, or in order to control and stabilize the scale factor, which is the gain of the plate thickness control system of the absolute value AGC, It is another object of the present invention to provide a plate thickness control method for a taper plate that can obtain a taper plate having a target gradient without any inconvenience even if the taper plate has a small value.

[0017]

A taper plate thickness control method according to the present invention is a control system for performing plate thickness control based on a relationship between a rolling roll gap and a rolling load during flat plate rolling and a predicted rolling load. In the plate thickness control method of the taper plate to obtain a taper gradient in the output side plate thickness by changing the output side plate thickness target value into a tapered shape in accordance with the rolling length,
Output side target thickness gain, mill rigidity value, material plasticity coefficient,
It is characterized in that the correction calculation is performed based on the gain of the plate thickness control system and the target taper amounts of the inlet and outlet plate thicknesses.

[0018]

In the present invention, the amount of change in the thickness of the taper plate on the outgoing side is defined as the mill rigidity coefficient, the plasticity coefficient of the material to be rolled, the gain of the plate thickness control system, the amount of taper on the incoming plate side and the outgoing taper on the outgoing side. Since the value corrected by the target thickness gain based on the thickness taper amount is used, multi-pass rolling is performed and even if the gain of the thickness control system is less than 1.0 in order to avoid the influence of mill hysteresis. It is possible to control the thickness of the taper plate in a stable manner.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing a control system for carrying out the method for controlling the plate thickness of a taper plate according to the present invention. In the figure, 1 is a rolling mill, 2 is a reduction device, 3 is a roll gap detector, and 4 is rolling. A reaction force detector, 5 is a pulse oscillator, and 6 is a material to be rolled. The rolling mill 1 is provided with a pair of work rolls 1a and a backup roll 1b, and the material to be rolled 6 is rolled plural times from the arrow direction in the same direction or alternately in the forward and reverse directions. .

During rolling, the detection value of the roll gap detector 3 is given to the roll gap position control system 15 and the output side plate thickness change amount detector 16, and the pulse output from the pulse oscillator 5 is the target output side taper plate thickness. To the change amount setting device 13, the detection value of the rolling reaction force detector 4 is detected by the output side plate thickness change amount detector 1.
6 are given respectively. Reference numeral 11 denotes a target taper amount setting device, which is a plate thickness difference ΔH ⁰ between the thin end and the thick end of the material to be rolled 6 on the inlet side of the rolling mill 1, and the thin end and the thick end on the outlet side of the rolling mill 1. And a plate thickness difference Δh ⁰ between the target taper plate thickness change amount setter 13 and the target output side taper plate thickness change amount setter 13.

The target output side taper plate thickness change amount setting device 13 is
The target inlet side plate thickness difference ΔH ⁰ and the target outlet side plate thickness difference Δh ⁰ input from the target taper amount setter 11, and the constant setter 1
2, the mill rigidity coefficient M of the rolling mill 1, the scale factor K _{A which is} the gain of the strip thickness control system, and the plasticity coefficient Q (−
∂P / ∂h), plasticity coefficient Q '(∂P / ∂H), and the number of pulses taken from the pulse oscillator 5 (corresponding to the rolling length)
Based on the following equation (8), a target output side taper plate thickness change amount Δh _T ** which is a plate thickness target value gain is calculated, and this is given to the output side plate thickness control system 14.

[0022]

[Equation 4]

The delivery side plate thickness control system 14 includes a target delivery side taper plate thickness variation amount Δh _T ** input from the target delivery side taper plate thickness variation setting device 13 and rolling input from the constant setting device 12. Mill stiffness coefficient value M of machine 1, scale factor K _A that is the gain of the plate thickness control system, and output side gauge meter thickness change amount Δh given by the following equation (10) input from the output side plate thickness change amount detector 16. Based on _g , the roll gap control amount is calculated according to the following equation (9), and this is given as the reference S _REF to the roll gap position control system 15.

S = S ₀ − (K _A / M) · (P−P ₀ ) + Δh _T ** (9) The output side plate thickness change amount detector 16 is a rolling reaction force taken from the rolling reaction force detector 4. Based on the force change amount ΔP and the roll gap ΔS fetched from the roll gap detector 3,
Egress gauge thickness variation Δh according to the following equation (10)
_g is calculated and given to the outlet plate thickness control system 14.

Δh _g = ΔS + (K _A / M) · ΔP (10) where ΔS: roll gap change amount ΔP: rolling reaction force change amount M: mill rigidity coefficient

The roll gap position control system 15 sends to the reduction device 2 based on the roll gap as a reference given from the delivery side plate thickness control system 14 and the roll gap detection value S taken from the roll gap detector 3. Outputs a control signal to adjust the roll gap.

[0027] Thus, the equation (9) and, Delta] h _T * as Delta] h _T ** and also η as (8) side thickness variation out using a thickness target value gain in the expression Delta] h of FIG. 2
When (Break end reference) is calculated, Δh = Δh _T ,
The control is performed so that the delivery side plate thickness always matches the target delivery side taper plate thickness. Therefore, the target tapered plate can be obtained by repeating such rolling control a plurality of times, that is, performing rolling in a plurality of passes.

In this case, it is premised that the inlet side taper plate thickness change amount ΔH _T shown in the equation (7) is equal to the target outlet side taper plate thickness change amount in the previous pass. When the taper amount is applied over the entire length, the plate thickness on the delivery side of each pass is sequentially controlled from the first pass. Further, since the thickness and temperature change in the longitudinal direction of the rolled material 6, the plasticity coefficient Q,
Q'also changes. This is dealt with by obtaining the values of the plasticity coefficients Q and Q'at a plurality of points in the longitudinal direction of the material to be rolled 6 in advance and changing the values of Q and Q'instantaneously according to the rolling length. .

The method of the present invention and the conventional method (Japanese Patent Application No. 6-225)
No. 439), the conditions and results of the comparison test are shown in FIG. The rolled material 6 having a plasticity coefficient Q of 500 ton / mm was rolled at a scale factor K _{A of} 0.9 under the conditions shown in the left column of the chart, 10 sheets each, and the average taper gradient was detected and compared. As is clear from the right column of the chart, the result of the method according to the present invention is 0.5 to 1.0% different from the target taper gradient as compared with the case of the conventional method.
It is understood that the degree has been improved.

[0030]

As described above, in the method of the present invention, when the taper amount is applied over a plurality of passes, due to the influence of mill hysteresis, etc., the gain of the plate thickness control system is theoretically maintained in order to maintain the control stability. Even when it is inevitable to lower the value, it is possible to obtain a taper plate having a stable and accurate taper gradient.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control system for carrying out a plate thickness control method for a tapered plate according to the present invention.

FIG. 2 is a chart showing the conditions and results of a comparative test between the method of the present invention and the conventional method.

FIG. 3 is a block diagram showing control contents of a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolling mill 2 Rolling down device 3 Roll gap detector 4 Rolling reaction force detector 5 Pulse oscillator 11 Target taper amount setting device 12 Constant setting device 13 Target output side taper plate thickness change amount setting device 14 Output side plate thickness control system 15 Roll gap Position control system 16 Output side plate thickness change detector

Claims (1)

[Claims] 1. The target value of the outlet plate thickness is changed to a taper according to the rolling length by using a control system that controls the plate thickness based on the relationship between the rolling roll gap and the rolling load during flat plate rolling and the predicted rolling load. In the plate thickness control method of the taper plate that obtains a taper gradient to the output side plate thickness by setting the output side plate thickness target value gain to the mill rigidity value, the plasticity coefficient of the material,
A plate thickness control method for a tapered plate, characterized in that a correction calculation is performed based on a gain of a plate thickness control system and a target taper amount of an input side and an output side plate thickness.