JPS61189810A - Shape-controlling method in finish rolling - Google Patents

Abstract

PURPOSE:To obtain reasonably and efficiently a rolling stock having prescribed sheet thickness and sheet shape, by obtaining the amount of offset of a roll gap and the amounts of thermal expansion and wear by performing the learning computation by optimization technique based on the data of actual results, for controlling the shape of stock. CONSTITUTION:The estimated outlet-side sheet thicknesses of all the stands, each of which makes the difference between the ratio, between the computed value and actual value of a rolling load of each stand, and the ratio, between the computed value and actual value of a rolling load of the next stand, into a minimum value, are obtained in series from the outlet-side gauge-meter thicknesses of respective stands by the learning computation by optimization technique based on the actual results, to use the difference between the estimated sheet thickness and said outlet-side gauge sheet-thickness, as the offset amount of the roll gap of said stand. Further, the amounts of thermal expansion and wear are estimated from the variation of said amount of roll gap, varying with the cumulation of the number of rollings. Based on said estimation; the shape control of a rolling stock, such as the computation of roll crown and the operations of roll bending and roll shifting, is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of controlling the shape of a rolled material by estimating wear and thermal expansion of rolls in hot finish rolling or the like.

<Prior art> In general, in hot tandem rolling, the wear and thermal expansion of the rolls of each stand have a large effect on the shape of the rolled material, so in order to obtain the target thickness and shape, it is necessary to It is necessary to accurately estimate thermal expansion and operate roll benders and roll shifts accordingly.

Conventionally, wear and thermal expansion of the rolls have been estimated from changes in the amount of offset between the rolls as the number of rolling cycles increases. The offset amount of the roll gap of each stand is determined by the mass flow plate thickness given by the following equation (1) at the same time of rolling and the outlet gauge meter plate thickness given by the following equation (2). It is determined by the difference (formula (3) below).

However, i: Stand number (i = 1 to 7) h': Simultaneous exit side mass of i-stand (i) Low plate thickness r(i): Advance rate N'' of i-stand (i): Simultaneous exit-side mass of i-stand Point roll rotation speed D(i
): Roll radius hx of i-stand Actual plate thickness measured at the same time using the X-ray thickness meter on the exit side of the near stand J(i): Plate thickness 5P (i) on the same point exit side of the i-stand: Same-point thickness of the i-stand Single point actual measured roll gap value Fjl'(i): i7. Actual load at the same point Mi: Mill constant of i-stand So: Constant OF'(i): Roll gap offset amount of i-stand <Problem to be solved by the invention> However, the above formula (1), that is, constant mass flow The advance rate f(i) of each stand used in the formula is As shown in FIGS. 6 and 7 as examples, the roll gap offset amount OF'(i) fluctuates irregularly and widely as the number of rolling operations increases. Therefore, it is impossible to accurately estimate roll wear and thermal expansion from such irregular fluctuations.

In addition, normally, in hot tandem finish rolling, each time rolling is performed, the calculated load is calculated using a rolling load model using the actual values of plate thickness, plate temperature, rolling load, etc. in the finished rolling. The difference between the calculated load Fc and the actual load FA is checked, and the rolling load model is corrected by a learning calculation method using an optimization method so as to eliminate this difference. However, the conventional rolling load model has been modified only for errors in the deformation resistance of rolled materials, and has not been corrected at all for sheet thickness errors. Therefore, the actual load F
As shown in Fig. 8 as an example, the ratio of A to the calculated load Fc fluctuates significantly for each round of rolling, making it impossible to set the next rolling conditions with precision, and the balance of rolling loads between stands is disrupted, resulting in poor rolling. There were drawbacks such as warping and distortion of the plate.

One of the inventors of the present invention has recently proposed a learning calculation method using a novel optimization method that can eliminate the above-mentioned drawbacks (Japanese Patent Laid-Open No. 57-4312). This learning calculation method sequentially calculates the difference between the ratio of the calculated value of the rolling force and the actual value (FA) in the stand of the previous stage and the ratio of the calculated value of the rolling load and the actual value (FA) of the stand of the next stage, from the first stage to the last stage. After successively finding the true outlet plate thickness for all stands that will minimize the value from the outlet gauge meter plate thickness of each stand through learning calculations using an optimization method based on past rolling results, The rolling load (Fc) of the current transformation stand is calculated using this near-true exit side plate thickness. As shown in FIG. 9, the ratio between the actual load FA and the calculated load Fc obtained in this way has a standard deviation of approximately 1/3, which shows little fluctuation compared to the conventional example (see FIG. 8). The accuracy of predicting the set values for the next rolling is significantly improved. In addition, the inventors have found that the above-mentioned true outlet side plate thickness is much more accurate than the above-mentioned outlet side mass flow plate thickness hIll (see iX (1) formula), which has many errors, and that it is measured by an X-ray thickness meter etc. We have actually confirmed that it approximately matches the measured plate thickness.

Therefore, an object of the present invention is to provide a method for controlling the shape of a rolled material by estimating the wear and thermal expansion of the rolls using the true outlet plate thickness obtained by the learning calculation method described above. .

Means for Solving the Problems> The shape control method in finish rolling of the present invention uses the learning calculations described above based on the past rolling results from the exit side gauge meter plate thickness of each stand to sequentially change the shape from the first stage to the last stage. The estimated plate thickness at the exit side of all stands is determined so that the difference between the calculated value and actual value of the rolling load in the stand and the ratio of the calculated value and actual value of the rolling load in the next stand is minimized. After calculating the thickness in series, the difference between the outlet gauge meter plate thickness of each stand and the estimated outlet plate thickness, which is considered to be the true plate thickness, is determined as the roll gap offset amount for that stand.
The present invention is characterized in that the thermal expansion amount and wear amount of the rolls are estimated from the variation in the roll gap offset amount as the number of rolling operations increases, and the shape of the rolled material is controlled based on these estimated amounts.

<Effects of the Invention> According to the present invention, it is possible to accurately and completely eliminate the adverse effects of roll wear and thermal expansion on the shape of the rolled material, and to rationally and efficiently produce the rolled material having the desired thickness and shape. can be obtained. .

<Example> Hereinafter, the present invention will be explained in detail with reference to Examples.

Roll gap offset amount OF of each stand for this rolling
(i) is determined by the following equations (4) and (5).

op(i)=J(f)-h*(D...
・(5) However, in h(i): Gauge meter plate thickness 5P on the exit side at the same point of the i stand (i): Actual roll gap value FK (t) at the same point on the i stand: Actual load Mi at the same point on the t stand :
Mill constant So of i-stand: Constant 0F(f): Roll gap offset amount h*(i) of i-stand: Estimated exit side plate thickness of i-stand The above estimated exit side plate thickness h*(i) was calculated by the inventors. A learning calculation method using the above-mentioned optimization method recently proposed by one of
This is the thickness of the exit side of the i-stand that is close to the true thickness obtained by No. 12).

Roll gap offset amount 0F calculated using formula (5) above
Examples of (i) are shown in FIGS. 1 and 2. In these figures, the horizontal axis represents the rolling number n, and the vertical axis represents the roll gap offset amount OFn, and shows the variation in the offset amount as the number of rolling times increases. As is clear from the figure, the offset amount fluctuates in a small range around 0Fn=0, and is much more continuous and smooth than the conventional example (see Figures 6-7). It was confirmed that the portion that increases substantially monotonically toward the maximum value corresponds to the thermal expansion of the roll, and the portion that decreases approximately monotonically from the maximum value quantitatively corresponds to wear of the roll. That is, FIG.

We actually measured the surface shape of the roll due to wear and thermal expansion for a specific offset amount variation on the vertical axis in Figure 2, and approximated the roll surface shape with a quadratic curve or a sine curve as shown in Figure 3. The amount of crown (value of y at x=0) was determined. As a result, the relationship between the offset amount variation and the roll crown amount becomes a monotonically increasing convex curve as shown in FIG. 4, and the roll crown amount, which represents roll wear and thermal expansion, can be determined from the offset amount variation. In other words, according to this embodiment, it is possible to accurately estimate the roll shape due to wear and thermal expansion of the roll as the number of rolling cycles increases. Note that wear and thermal expansion of the roll during rolling of one coil for a short period of time, for example, can be similarly estimated.

FIG. 5 is a flowchart illustrating a shape control method according to the present invention including the steps described above. First, in step (a), the actual load of each stand for this rolling.

Enter the actual data such as the measured roll gap value, and proceed to step (
(b) Output side gauge meter plate thickness of each stand (formula (4))
At the same time, the estimated outlet thickness is calculated by learning calculation using an optimization method, and the roll gap offset amount ((5
) formula). Next, in steps (c) and (d), the wear and thermal expansion of the rolls of each stand are estimated from the roll gap offset amount, and the roll crown amount is calculated (see Fig. 3.4). Finally, in step (E), rolling conditions are set based on the roll crown amount and the like in order to control the shape of the rolled material in the next rolling. In other words, the roll bender or roll shift is operated to eliminate the roll crown of the work roll due to roll wear and thermal expansion, and the well-known plate crown ratio constant rule is used to take into account the roll wear and thermal expansion of each stand. Based on this, the plate thickness distribution of each stand will be corrected in a well-balanced manner. By such a shape control method in tandem finish rolling, it is possible to completely eliminate the adverse effects of roll wear and thermal expansion and obtain a rolled material having a target thickness and shape.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing variations in the amount of roll gap offset according to an embodiment of the present invention, Figure 3 is a diagram showing the roll shape due to wear and thermal expansion, and Figure 4 is a diagram showing variations in the amount of offset and roll crown. 5 is a flowchart of a shape control method according to an embodiment of the present invention, FIGS. 6 and 7 are diagrams showing variations in roll gap offset amount according to a conventional example, and FIG. 8 is a diagram showing a conventional method. FIG. 9 is a diagram showing the actual load/calculated load ratio obtained by the learning calculation using the optimization method of the present invention.

Claims (1)

[Claims] (1) Through learning calculations using an optimization method based on past rolling results from the exit side gauge meter plate thickness of each stand,
From the first stage to the last stage, all stands are selected so that the difference between the ratio of the calculated value and actual value of the rolling load in the previous stage stand and the ratio of the calculated value and actual value of the rolling load in the next stage stand becomes the minimum value. After finding a series of estimated outlet plate thicknesses at , the difference between the outlet gauge meter plate thickness of each stand and the estimated outlet plate thickness, which is considered to be the true plate thickness, is taken as the roll gap offset amount for that stand, Shape control in finish rolling, characterized in that the amount of thermal expansion and wear of the rolls is estimated from the variation in the roll gap offset amount as the number of rolling cycles increases, and the shape of the rolled material is controlled based on these estimated amounts. Method.