JPS5944128B2 - Hot strip width control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling the width of a hot strip.

(Conventional Background) The following two factors are considered to be the main causes of strip width variations occurring in the longitudinal direction of the hot strip.

That is, one of them is based on the strip width fluctuation that has already occurred at the end of rough rolling, and the other is one that occurs during the finish rolling process.

The main cause of the latter is fluctuations in deformation resistance due to temperature differences in the longitudinal direction of the rolled material due to skid marks, and fluctuations occur even under constant inter-stand tension.

By the way, in conventional hot strip hot rolling,
Because the strip width after finish rolling fluctuates in the longitudinal direction of rolling due to various reasons, the nominal strip width in finish rolling for rolled materials is determined by adding an allowance αmm to the strip width Wmm requested by the customer or the next process. After rolling, both ends having a width of W mm or more are sheared off with a shearing machine,
Usually, the plate is finished to a predetermined width Wmm.

Therefore, as shown by curve a in the attached Fig. 1, the greater the strip width variation after finish rolling that occurs in the longitudinal direction of rolling, the larger the allowance αmm must be, which may lead to a decrease in rolling yield. become.

In view of the above points, methods for controlling strip width have been studied for some time.One method focuses on the fact that changes in tension between stands have a large effect on changes in strip width of rolled material in the finish rolling process. This method reduces strip width fluctuations that occur in the longitudinal direction of a rolled material by changing the tension between stands during rolling, which was conventionally kept constant during rolling.

However, since the influence of changes in tension on sheet width correction is complex, no established technology has yet been disclosed regarding a specific method thereof.

(Objects and Structure of the Present Invention) The present invention has been made in view of the above points, and is aimed at minimizing variations in strip width after finish rolling by hot stripping by controlling the tension between each stand. The purpose is to easily provide a control method, and its characteristics are as follows: First, the width and temperature of the rolled material after rough rolling are measured at regular intervals over the entire length of the rolled material;
The strip width Wi after finish rolling at each measurement point is predicted using a predetermined formula under the condition that each finishing stand tension is a predetermined constant value, and the target strip width W is determined.

deviation W.

-Wi, the tension setting value Tri between the first and second stands that minimizes the deviation is calculated for each measurement point using a predetermined formula, and then the strip width W11 after finish rolling at each measurement point The first ~
The tension between the second stands is the calculated value Tlj-dashi,
The width difference W from the target plate 1 is predicted by a predetermined formula under the condition that the tension between the stands after the second stand is a predetermined constant value.

After determining -Wll, the tension setting value T2i between the second and third stands that minimizes the deviation is calculated for each measurement point using a predetermined formula, and the tension setting value between the third stand and the subsequent stands is further calculated using a predetermined formula. The hot strip strip width control method uses the same calculation method to set the tension from the stand side and outputs the tension setting value between each stand according to each measurement point during finish rolling of the rolled material.

(Example) Hereinafter, an example of the method of the present invention shown in the accompanying drawings starting from FIG. 2 will be described in more detail.

FIG. 2 is an explanatory diagram of the tension between the first and second stands in an apparatus according to an embodiment of the method of the present invention, and FIG. 3 is a diagram showing the configuration of the entire apparatus and equipment.

In FIG. 3, the plate width meter 2 and thermometer 3 of the rolled material 4 installed on the exit side of the rough rolling mill 1 measure the position P at every constant length over the entire length of the rolled material 4 after rough rolling. The plate width and plate temperature are measured at , and inputted into the tension setting value calculation and storage device 5 .

On the other hand, "product information" (details thereof are omitted) such as material information such as steel type, composition, plate width and thickness, and finished dimensions of the rough-rolled material 4 preset on the material information setting panel 6 is Finish rolling pass schedule calculation for the rough rolled material 4 and each stand 8, 9, 10, 11 of the finishing mill...
It is input to the reduction schedule setting device 7 which performs the reduction setting control, and is also input to the tension setting value calculation and storage device 5.

Furthermore, the finish rolling pass schedule calculation result by the rolling schedule setting device 7 is also stored in the tension setting value calculation storage device 5.
is input.

Therefore, the tension setting value calculation/storage device 5 determines that each measurement point at which the strip width and strip temperature were actually measured for each fixed length based on these manual efforts has reached the exit side of the finishing rolling mill (arrow on the right side of the figure). Calculate the predicted strip width at the time using the method described later, find the deviation from the target strip width, and set the inter-stand tension at each stand rolling timing at each measurement point to minimize the deviation using the same method described later. The amount of change in value from the standard setting value (deviation from the target finished width) is calculated and stored.

Furthermore, the device 5 continuously captures the detection outputs of the rolling pressure and rolling speed detectors 12, 13, 14, 15, . . . of each stand, so that the measurement points of the rolled material 4 can be The timing of reaching each stand is calculated, and the amount of change in the tension setting value already calculated and stored is calculated accordingly to each stand tension control device 16.17.18.
Output to...

Therefore, tension control devices 16, 17 between each stand are provided.

18, . . . control the tension between each stand based on the given set value, and function to give a desired amount of change in plate width to the rolled material 4 existing between each stand.

The details of the processing are roughly divided into two as described below.

One is to predict and calculate the strip width after finishing rolling at each measurement point of the rolled material 4, and determine the amount of change from the standard value of the tension setting value to be applied between each stand according to the deviation (amount of change) from the target value. The other function is to change the tension setting value determined in this way by the tension control device 1 according to the movement of the rolled material 4.
This is a function to control the timing of output on 6, 17, 18, . . . .

The former (amount of change) is shown in the flowchart of FIG. 4a, and the latter (timing) is shown in the flowchart of FIG.

In other words, block B1 in Fig. 4a predicts the width of the rolled material when it reaches the exit side of the finishing mill at each point of the rolled material whose width and temperature are measured at every fixed length after the completion of rough rolling. This is a calculation block, but first we will explain its theoretical background.

It has been experimentally determined that the amount of width shrinkage of a rolled material in a finishing mill is expressed by the following equations 0 and 0.

ΔWf=ΔWf (t, Tf, v, Wk)
”...■Δwb=ΔWb(t, Tb, v, Wk)
...-■Here, ΔWf: Amount of width reduction due to front tension (mm) ΔWb: Amount of width reduction due to rear tension (mm) t
: Rolling temperature 0 Tf, Tb: Forward tension and backward tension per unit area in the cross section of the rolled material (K4/ma) V: Rolling time required for the rolled material to pass through the roll bit (sec) Wk: Nominal plate of the rolled material Width (mm) The above formula 0 is, for example, for low carbon killed steel, ΔWb =
Wk (1-exp (-1,91-10'・eO・0
0795j, Tb2,5 ・vO02)) ,,・,・
・It is like ■.

The rolling temperature, rolling time, and tension setting value between each stand in each stand of the finishing mill can be easily obtained by a well-known finishing mill setting calculation, so a description of the calculation method will be omitted.

After all, if the width of the strip at the entry side of the finishing rolling mill is known, the width of the strip at the exit side of the finishing rolling mill can be predicted using equations (1) and (2) above.

That is, if the strip width at the exit side of the finishing rolling mill is Wout and the strip width at the entry side of the finishing rolling mill is Win, then Wont can be determined by the following formula (2).

However, the subscript j represents the stand shop, and n represents the stand removal of the finishing rolling mill.

Now, let's consider simplifying Equation 0.

Now, 1. gl, 10 9. e000795j, T
Assuming that the value of bS,5・vQ,2 is sufficiently smaller than 1, ΔWb#Wl(-1,91・10−”・eo・007
It is approximated as "t-Tb"・vo・2...■.

Furthermore, considering that the range in which the inter-stand tension can be changed in normal rolling is not wide, Tb2.5 is linearly approximated within the range in which the tension setting value is used.

Here, Tb2.5 is approximated as follows near the set value Tbo calculated by the finishing rolling mill setting calculation.

Tb2・5: Sun 2.5-'rbo'-5 ('rb-Tb
o)+Tbo''-'...■ If you substitute the 0 expression into the 0 expression and rearrange it by Tb, you will eventually get the following expression.

Tb (t, Tb, v) two α・Tb ten β ...
...■Here, α=ko・2.5・Tbol・5β=-
ko・1.5・Tbo2・5 ko = Wk ・1.91.10 “eO・007”
The following equation is obtained in the same manner for the t-vo.2■ equation.

T + (t, Tf, v) = γ°Tf: δ °° song ■
In the end, the formula (■) can be expressed as follows.

In particular, j stands for stand shop.

Considering the above, the width of the rolled material at each point when it reaches the exit side of the finishing rolling mill can be predicted and calculated using the following equation 0.

In particular, i: the tip of the strip at a measurement point where the width and temperature of the strip are measured by the aforementioned strip width gauge 2 and thermometer 3 at regular intervals along the length of the strip after rough rolling. The order is from .

i must be 1≦i≦, and k is the total number of measurement points.

Wi: Predicted plate width calculation value of the finishing rolling mill at the first measurement point WRl: Actual measurement value of the plate width after rough rolling at the first measurement point n: Number of stands of the finishing rolling mill aji, bji: 1st It is a constant determined from the relationship between the forward tension in rolling at the j-th strand of measurement point and the amount of change in strip width, and aji=aji(tji t vj tWk) bji=
bji (tji t Vj , Wk) cji, dji
: A constant determined from the relationship between the rear tension and the amount of plate width change in rolling of the j-th stand at the first measurement point, cji = cji (tji, vj, Wk) dji = dj
i(tjis vj tWk)Tfi: forward tension per unit cross-sectional area acting on the rolled material during rolling at the j-th stand, that is, the standard tension setting value between the i-th to j+1-th stands.

However, Tfn=0.

Tbj: Backward tension per unit cross-sectional area acting on the rolled material during rolling on the first stand, that is, the standard tension setting value between the j-1th to j-th stands.

However, Tb1=O.

tji: Predicted rolling temperature calculation value at the j-th stand at the first measurement point vj: Rolling time required for the rolled material to pass through the roll bit at the j-th stand Target strip width WO is set on the straight line a in FIG. An example of the calculated value Wi of the predicted sheet width after finish rolling using the above-mentioned formula 0 is shown below the curve.

In addition, block B2 in FIG.
Wi is calculated according to the following formula 0.

ΔWi=Wi−Wo...
...■ Block B3 in Fig. 4a is the amount of change ΔT from the standard setting value of the inter-stand tension at the timing when the first measurement point is rolled at the j-th stand according to the above-mentioned ΔWi.
In the block for calculating ij, the amount of change in the tension between each stand is determined by the method shown in the flowchart of FIG.

In addition, in FIG. 6, block B1 calculates the tension between the first and second finishing stands ( FIG. 2 is a block diagram for calculating the amount of finished plate width modification possible by changing the width of the finishing plate (see FIG. 2).

Regarding the influence of inter-stand tension on plate width changes, as is known from experiments with single stands, the degree of influence that "front tension" and "backward tension" have on plate width correction is different, so Between two stands as shown in FIG.
It acts as a backward tension on the material present in the position where the stand is ejected.

In this way, changing the tension between the stands of a continuous mill will change the strip width at different positions of the rolled material, so it is necessary to pay attention to this point.

[While the first measurement point passes through the first and second stands, the inter-stand tension is changed by ΔT, 1 from the standard tension setting value, resulting in a slight change Δ in the predicted finished plate width
In the above formula 0, W11 is Wi and Tf 1. T
By considering the change in b1, it is given by the following equation 0.

ΔW1i= b'1iΔTri 10d2iΔTri
・・・・・・■However, from various experimental results regarding the tension between stands, it has been known that the first term on the right side of the above equation (■) is smaller than the second term, so as shown in Fig. 5, For fixed points on each side of the rolled material corresponding to each predicted finished plate width calculation value, the deviation from the target finished width is almost zero (zero).
In order to do this, it is sufficient to give the tension set value change amount between the first and second stands, which is calculated by the following formula 〇.

ΔWi / d 2 i to ΔT1
......0 Here, ΔTli: Amount of change in the tension setting value between the first and second stands at the moment when the i-th measurement point enters the second stand Block B1 in Fig. 6 is based on the above formula 0.
Calculate the amount of change in the tension setting value between the second stands, 1”nT11J.

However, ΔTri is the upper and lower limit values ΔT1max and ΔT1mm determined from work standards or rolling equipment specifications.
If the limit value is exceeded, processing is performed to stop the limit value.

That is, the relationship between ΔWi and ΔTri is as shown in FIG.

In this way, each point (1, 2, 3, 4, . . .
The amount of change in the tension set value between the first and second stands calculated for .

Here, as mentioned above, when calculating the amount of change in the tension set value between the first and second stands based on the formula 0, the front tension acting on the rolling in the first stand was ignored, so
Since it may not be possible to reduce the ΔWi to zero just by changing the tension between the second stands, the following process is performed to ensure that the finished plate width accurately matches the target value.

That is, in block B1 of FIG. 6, it is assumed that the tension between the first and second stands has been changed according to the amount of change in the tension set value between the first and second stands obtained in this way, and that Assuming that the tension setting value remains the standard setting value, the finished plate width W11 is predicted and calculated using equation 0, which is similar to equation 0.

In particular, Tf1i=Tb2i are the same value, and take the value obtained by adding the value shown in curve a in FIG. 8 to the standard film constant value.

Tfji (j>2) and Tbji (j > 3) is a constant value It is.

The results calculated using the formula 00 and 00 are shown in the curve a in Figure 9.The deviation from the target finished board width is as shown in the curve a in Figure 9 if the tension setting value between the first and second stands is not changed. It can be clearly seen that the amount decreases by a large margin compared to .

Block B2 in FIG. 6 is a second block B2 in order to zero the deviation from the target finished width of each point shown in the curved line in FIG. This block determines the third inter-stand tension setting value change amount ΔT2i in the same manner as in block B above.

Similarly to block B1, an example of the calculation result is shown in Figure 8, curve b.
1 Shown in curve C in Figure 9.

Further, block B3 and subsequent blocks Bn-1 (not shown) in FIG. 6 are block B1 or B2.
Similarly, the amount of change in the inter-stand tension setting value for the third and subsequent stands is determined.

In this case, [ΔWiJ
When the width of the finished plate is small, the finished plate width can be controlled to the target finished width over the entire length of the rolled material by changing only the pre-stage inter-stand tension settings.

Conversely, if ΔWiJ is large, it is conceivable that the deviation between the finished plate width and the target finished width cannot be made zero even if the tension settings between all the stands are changed.

In addition, during normal operation, there is no need to change the tension setting value between all stands, and the amount of change in the tension setting value between each stand is determined so that the deviation between the predicted finished board width at each measurement point and the target finished width is almost zero. be done.

Block B4 in FIG.
Using signals from the rolling pressure and rolling speed detectors 12, 13, 14, 15°, etc. of each stand, the plate width and A process is performed to track the movement of each measurement point where the temperature is measured, and a signal is issued at the moment each measurement point reaches the first to nth stands.

Block B in FIG. 4 takes out the amount of change in the inter-stand tension setting value corresponding to each measurement point according to the signal issued in the process of block B4, and calculates the amount of change in the inter-stand tension setting value corresponding to the corresponding inter-stand tension control device 1.
6, 17, 18. Output to...

(Effects of the Invention) As described above in detail with respect to the embodiments, according to the method of the present invention, in the hot strip strip width control method, strip width fluctuations after finish rolling of a rolled material can be suppressed to almost zero. Remarkable actions and effects are exhibited.

As a result, the board width margin that was conventionally expected can be significantly reduced, which greatly contributes to improving yield.

[Brief explanation of the drawing]

Fig. 1 is an explanatory graph showing an example of the measured value of the strip width after finish rolling, Fig. 2 is an explanatory drawing showing the tension between the first and second stands, and Fig. 3 is an explanatory graph showing an example of the measured value of the strip width after finish rolling. FIG. 4 is a flowchart showing the method of the present invention, FIG. 5 is a graph showing an example of the measured width of the rolled material after rough rolling, and FIG. 6 is the method of the present invention. A flowchart diagram showing details of the method, FIG. 7 is a graph diagram showing the relationship between plate width deviation and tension setting value change amount in an example of the present invention, and FIG.
FIG. 9 is a graph diagram showing an example of calculated values in the embodiment of the present invention.

Claims (1)

[Claims] 1. The plate width and plate temperature of the rolled material after rough rolling are measured at fixed length intervals over the entire length of the rolled material, and the plate width Wi after finish rolling at each measurement point is determined by the tension between each finishing stand. The deviation W from the target plate portion is predicted using a predetermined formula under the condition that W is a preset constant value. After determining -Wi, the tension setting value Tri between the first and second stands that minimizes the deviation is calculated for each measurement point using a predetermined formula, and then the strip width Wli after finish rolling at each measurement point The first ~
The tension between the second stands is the calculated value Tli. Under the condition that the tension between the stands after the second stand is a predetermined constant value as above, it is predicted by a predetermined formula, and the target plate is Width W. deviation W. After determining -Wl i, the tension setting value T2i between the second and third stands that minimizes the deviation is calculated for each measurement point using a predetermined formula, and the tension values between the stands after the third stand are further calculated using a predetermined formula. A method for controlling the width of a hot strip strip, characterized in that the tension is calculated sequentially from the stand side using the same calculation method, and the tension setting value between each stand is outputted according to each measurement point during finish rolling.