JPH02112814A - Sheet thickness control method for continuous rolling of metallic material - Google Patents

Abstract

PURPOSE:To obtain a sheet thickness with good accuracy by measuring a rolling load, rolling torque and forward slip at the time when the front end of a material to be rolled passes a stand, then by computing the deformation resistance of the material to be rolled and subjecting the roll gap of the downstream side to correction control. CONSTITUTION:The load Pi is actually measured by a load cell 3i, the torque Gi by a torque meter 49, the speed Vi by a speedometer 5i, the rotating speed Ni by a roll rotating meter 7i mounted to a rolling roll speed controller 6i, and the roll gap Si by a draft position detecting part 9i mounted to a draft position controller 8i and the measured values are inputted to a computer 10 for control at the time when the front end 1 of the material to be rolled passes along the rolling roll 2i of the i-th stand. The forward slip Fi is then calculated by the speed Vi and the deformation resistance Ki of the material to be rolled is computed by using these measured values and the rolling theory equations. The roll gap after the (i+1)th stand is subjected to the correction control by the results of these computations. The accurate sheet thickness in continuous rolling is obtd. in this way and the yield is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a temporary 17 control method in hot or cold continuous rolling of metal materials such as steel and aluminum.

<Prior Art> In continuous rolling, in order to obtain a highly accurate provisional j7 from the tip of the coil of the material to be rolled, it is necessary to set up the roll opening of each rolling stand to an appropriate value in advance. However, in areas other than the tip of the coil, rolling is stable, and normal feedback-type AGC (automatic plate thickness control?11) using plate thickness and tension detection values works effectively.
Plate thickness accuracy is guaranteed. Therefore, if proper set-up is performed during sheet passing (when the tip of the material to be rolled is bitten), a highly accurate sheet thickness can be obtained over the entire length of the coil.

By the way, cold continuous rolling mill (cold strip mill)
So, not only are coils long to begin with, but technology has recently been developed to weld and roll the coils in front of the rolling mill.
The proportion of the thickness defects during sheet threading in the total length is very small.
This does not pose a major problem in terms of yield. Therefore, the following description will focus on a continuous hot rolling mill (hot strip mill) in which defective sheet thickness during sheet passing is a major problem.

The roll opening degree for obtaining the target exit side plate w-hr of the i-stand is determined by the gauge meter formula of the following formula (1).

5i=hj fs (Pi, W, Pat)+Soi
-----(1) t, : Mill rigidity (function to calculate mill elongation during rolling) P: Rolling load W: Plate width P, : Pending force So: Zero point of roll opening L: Stand number Here , mill stiffness f, has been accurately converted into a function through elastic mechanics theory and pinching experiments using AI plates, etc., and the human force value B
, w, and p□ are known, so if Pi, SL, and L can be predicted accurately, Si with positive ci can be obtained. On the other hand, in order to predict PI, the following rolling load formulas (2) to (4) derived from the rolling theoretical formula are required.

PI leather ki・QPI-W-T revision 7T old-〇Below the shoulder--(
2) k: Deformation resistance port P: Rolling force function R': Flat roll radius H: Entry side plate thickness h: Output side plate thickness R: Roll radius μ: Friction coefficient tb: Input side tension tf: Output side tension E: Roll Young's modulus ν: Poisson's ratio of the roll As is clear from the above equations (1), (2), and (3), in order to obtain a highly accurate plate thickness, a highly accurate rolling force function Q1 and a high deformation resistance are required. Highly accurate prediction of the friction coefficient μ is required.

The rolling force function is derived from rolling theory, and Orovan's theory is famous as a strict rolling theory, and the formula for calculating the rolling force function derived from this theory was developed by Tamano and Yanagimoto (Japanese). Proceedings of the Japan Society of Mechanical Engineers.

42 (1978), P965), the present inventor (``Plasticity and Processing'').

27 (1982), p. 62), and it can be said that it has become possible to obtain a sufficiently high precision rolling force function.

The rolling force function according to the present inventor is shown in equation (3)'; however, in hot strip rolling, the tension term is not included because tensionless rolling is the standard.

μ self + 3.35 μi −ri −2,75 μm2・ri
l, 3/7 i-ri! −2,09βi +1.
28β12 On the other hand, a calculation formula is often used to predict the deformation resistance, and a constant value fixed to each stand is often used for the friction coefficient μ.The deformation resistance formula is the temperature of the rolled material.

A beautiful equation expressed in the functional form of rolling strain, rolling strain rate, and chemical components ([Plasticity and Processing, 8 (1967L)
PdI2) is famous.

Furthermore, JP-A-56-163017, JP-A No. 60-150
In Publication No. 10, as a method to improve the accuracy of the deformation resistance formula and friction coefficient, the rolling load and advance rate are measured, k and μ are derived from these measured values, and these are used to set up the next coil. It has been proposed to constantly modify the deformation resistance formula and friction coefficient, and it can be said that sufficiently high accuracy has been obtained for the deformation resistance formula and friction coefficient.

The advance rate Fi is determined by the roll circumferential speed V□ and the rolled material exit speed vi
(hereinafter referred to as plate speed) is defined as follows.

βl = mu h [(F + 1.5ri) u i
]fil Here, vl can be easily determined from the roll rotation speed N+ and the roll diameter DI, so if Vi can be measured, Fi can be determined. In order to back-calculate μ from this advanced rate, it is necessary to express the advanced rate formula in a form that includes μ, and various methods have been proposed. We have obtained a formula for calculating the advanced rate.

<Problem to be solved by the invention> However, in order to accurately predict the deformation resistance, positive values such as temperature of the rolled material and rolling strain, which are the manual conditions of the equation, are required. As for the temperature of the rolled material, it is currently difficult to obtain a positive value. The reason for this is that the temperature of the rolled material in each stand is calculated by referring to the surface temperature measured by a radiation thermometer at the entrance of the finishing mill, but due to problems such as the surface properties of the rolled material or water riding, etc. This is because there are often discrepancies between the measured temperature value and the actual temperature value. Therefore, since the deformation resistance (temperature of the rolled material) cannot be accurately predicted, it has been difficult to obtain a good thickness from the tip of the coil using only set-up.

As a method to solve such problems, for example,
0-99410, the rolling load and advance rate are measured when the tip of the material to be rolled is bitten by the first stand of the finishing rolling mill, and these measured values and the rolling theoretical formula are used to calculate the friction in the first stand. A method has been proposed in which the coefficient and deformation resistance are calculated, and the roll openings from the second stand onward are corrected based on the calculated values.

At that time, methods for determining the plate speed V include (1) a method of directly measuring the plate speed using a plate speed meter such as a laser speed meter, (2)
A method is disclosed in which the time taken for the tip of the rolled material to pass between two detectors installed at a fixed interval is measured and determined.

However, the actual measured values of rolling load P and plate speed V are not always correct due to various reasons described below, and therefore the calculated k and μ are not necessarily correct values. Therefore, the calculated value k .

If the correction system f21 of 1 m degree for the rolls from the second stand onwards was made based on μ, the accuracy of the coil tip thickness might deteriorate.

The causes of errors in the actual measured value of the rolling load P mentioned above include: ■ temperature changes or deterioration of the load cell, ■ changes in the output of the load cell due to differences in the way the pressure receiving surface of the load cell receives the load (unbalanced load, etc.); Possible causes include frictional force between the jacket and the housing.

In addition, the causes of errors in the actual measured value of the plate speed (■) mentioned above are: (1) When the plate speed meter such as a laser speed meter is used, the speed meter and the rolled material may be affected by an adverse environment such as water vapor and dust in the actual machine, or by loosening of the rolled material. (1) Regarding the method of measuring the transit time between two detectors, possible causes include slack in the rolled material that occurs during sheet passing.

The present invention has been made to solve the above-mentioned problems, and is aimed at stably rolling t/w from the tip of the coil of a material to be rolled.
It is an object of the present invention to provide a thickness side in method that allows continuous rolling of a thick plate with a good F degree.

Means for Solving the Problems> The present invention focuses on the fact that not only the rolling load and rolling rate but also the rolling torque depend on the friction coefficient μ between the rolling rolls and the rolled material and the deformation resistance k of the rolled material. In continuous rolling of metal materials, when the tip of the rolled material passes through the i-stand, the rolling load, rolling torque, and advance rate are measured, and these measured values and the rolling theoretical formula are used to calculate the The deformation resistance of the rolled material is calculated, and based on this calculation result (i
+1) The roll opening degree during rolling after the stand is corrected and controlled.

<Function> As is well known, rolling torque can be easily measured using a torque meter with a strain gauge attached to the spindle shaft of a rolling roll, and has a responsiveness comparable to rolling load measurement using a load cell. However, like with a load cell, a torque meter does not always provide accurate measured values due to factors such as temperature rise and deterioration of the strain gauge.Rolling torque Gi can be calculated using equations (7) and (8) from rolling theory. It is expressed as

Gi=Ri (IIL-hi) ・ki-Qe+・W
−−−−−−−(7) QG:) The torque function QGi is derived from the rolling theory, and Or
The calculation formula derived from OWAN's theory was published by Tamano and Kamiki (Proceedings of the Japan Society of Mechanical Engineers, 42 (1978), P965).
The present inventor further proposed Orowa
Formula (8)' has been developed as a calculation formula close to the theory of n.

0.2524 F-0,7033ri ・αi +0.
05534 μl ・αi +0.00869
αiα1-ri-,E-r100.8886! FT・
a i・βi−0.683αiFπd=■・β10.9
966ri"・ki ------1----
--(8)' However, since tensionless rolling is the standard for hot strip rolling, the tension term is not included in equation (8)'.

Then, the present inventor calculated the deformation resistance ki and the friction coefficient μi from only the measured values of both the rolling load Pi and the advance rate Pi, since ki and ki may not be predicted correctly, so the actual measurement of the rolling torque I thought about using the value to predict ki and ki.

The detailed procedure of the present invention will be explained with reference to FIG.

■ When the tip end 1 of the rolled material passes the rolling roll 21 of the i-stand, the load r'i, ) is applied by the load cell 31.
Torque Gi from the luxmeter 41, plate speed V from the temporary speedometer 51
i. The rotation speed Ni is measured by a roll tachometer 71 attached to the rolling roll speed control device 61, and the roll opening degree Si is measured by the rolling position detector 9I attached to the rolling position control device 81. input. however,
Although the plate speed is actually measured using a laser velocimeter in this figure, a method may also be used in which the tip passage time between two predetermined points (for example, between rolling rolls) is measured.

■ From the above formula (4), the flat roll radius Ri' is calculated from the above (
5] Calculate the advanced rate Fi from the formula and ki from the formula (6) above. However, the plate thickness hi is calculated using the gauge meter formula (see formula (1) above) using the measured values of Pi and Si.

(2) Deformation resistance ki is expressed by equations (2), (3)', and (7) above.

(8)', and let them be k jG') and ki (G).

■ kiG') and ki (G) are almost equal (for example, 5
%), the deformation resistance ki of the i stand is its average value ((ki (P) - 1 - ki (G))
/21, and the deformation resistance k after the (i+1) stand
j (j>i+1) and rolling load Pj are predicted by the following formula.

ko: Deformation resistance at set-up po: Rolling load at set-up■ (i+l) The roll opening degree Si after the stand is defined as (
Calculate from formulas 1), (2), (4), and (3)'. However, the friction coefficient μj used at that time is a learned value calculated from the rolling results of the previous coil.

(2) Output the 1 command value Sj0 of Sj from the control computer 8 to the reduction position control device 9.

<Example> When rolling ordinary steel with a 7-stand continuous hot finishing mill,
Effects of implementing the method of the present invention and conventional method (free? II)
A comparison was made with the effect of implementing this method using the plate thickness accuracy at the tip of the coil (standard deviation of the final exit side plate thickness deviation) as an evaluation item. The results are shown in Table 1.

Table 1 On the other hand, if kiψ) and k i (G) are not equal (for example, there is an error of 5% or more), kj and Pj are assumed to be equal to the set-up value. That is, let kj=7°pj=p7.

As is clear from Table 1, it can be seen that the method of the present invention can significantly improve the plate thickness accuracy at the tip of the coil compared to the conventional method.

<Effects of the Invention> As explained above, according to the present invention, a highly accurate plate thickness can be obtained from the tip portion of the rolled material during continuous rolling, and this can greatly contribute to improving the yield.

[Brief explanation of drawings]

FIG. 1 is a control block diagram showing an example of the present invention. 1... Tip of the material to be rolled, 2... Roll. 3...Load cell, 4...Torque meter 1
5... Plate speed meter, 6... Roll speed control device. 7... Roll tachometer, 8... Roll down position control n
Device. 9... Roll down position detector, 10... Control computer.

Claims (1)

[Claims] In continuous rolling of metal materials, when the tip of the rolled material passes through one stand, the rolling load, rolling torque, and advance ratio are measured, and these measured values and the rolling theoretical formula are used to calculate the deformation resistance of the rolled material. Based on the result of this calculation, (i+
1) A method for controlling plate thickness in continuous rolling of metal materials, which comprises corrective control of the roll opening after the stand.