KR790001893B1 - Shape control method for tandem rolling mill - Google Patents

Abstract

The method of the shape control for a tandem mill for rolling strip, wherein the shape of the rolled strip at the delivery side of the final stand is detected to provide with a signal corresponding to the long-edge shape, whereby the pattern of roll bending force for two or more latter stands are adjusted according to a signal or signals obtained effectively for desired-shape control without causing variations in the thickness of the strip at the delivery side of the last stand.

Description

Shape Control Method in Tandem Rolling Mill

1 is a diagram showing an example of the coefficient of influence in the case of a 5 stand cold tandem rolling mill.

2 is a diagram showing a waveform change of the edge of a strip in each stand when the material sheet thickness is changed into a step shape for a 5 stand cold tandem rolling mill.

3 is a diagram showing the change in the shape of the elongation of the central part of the same shape.

4 is a control block diagram of an embodiment of the present invention when changing the roll bender to modify the shape of the edge of the strip or the extension of the center portion.

5 is a control block diagram according to another embodiment of the present invention when changing the reduction force pattern to perform shape modification for extension of the central portion.

6 is a control block diagram according to another embodiment.

7 is a diagram showing an example of the waveform correction operation of the edge of the strip by the shape control method of the present invention.

Fig. 8 is a display ring diagram showing the change in the tension in front of each stand during the waveform correction operation of the edge of such a strip.

The present invention is due to the result of detecting the strip shape at the end of exiting the stand by using a roll bender or a rolling force pattern of one or more stands in rolling of the strip by a hot or cold tandem rolling mill. The shape control method in the tandem rolling mill which tries to obtain a good product shape by performing shape control with respect to the wave form of the edge of a strip and the extension | stretching of a center part in particular is carried out.

Conventionally, in the tandem rolling mill, as a method of controlling the shape of the product, that is, the waveform of the edge of the strip or the extension of the center portion, a roll bender is used to forcibly roll the roll to the outside in the stand of the rolling mill. The method of modifying the shape through the tension by a method of deforming or by the tension control means are known.

As a specific example, for example, as the former method, there is a method of controlling the thickness and the shape of a strip or a plate-like material, as indicated in Japanese Unexamined Patent Application Publication No. 47-47781. Stahl und Eisen, No. It is widely known that the shape control method described on page 90 Vol 22 124-1222 is typical. However, in the conventional shape control method, the scope of control is limited to a single stand, and a method of performing shape control in consideration of the mutual relationship between successive stands in a tandem rolling mill made of several rolling mills is not known at all. not.

In the so-called tandem rolling mill, it is needless to say that the tension is applied to the rolled material between successive stands. Therefore, if the method of modifying the shape of the short stand as described above is applied as it is to the tandem rolling mill, the first application stand is used. The change of tension in the front and rear causes a change in the pressing force of the stand and the front end of the stand, respectively, and as a result, an unnecessary shape change applied to the target shape correction is caused at the exit of the stand, and the predetermined shape correction is performed. Secondly, when the application stand is not the final stand, the effect of the shape correction on the application stand is mitigated sequentially at each subsequent stand while the application stand is rolled up to the final stand, and the expectation at the final stand exit is expected. Third effect is not obtained, The change in plate thickness due to the phase correction operation is captured by the automatic plate thickness control (AGC) circuit, the shape is changed again by the AGC operation, the desired shape correction operation is disturbed, and hunting of the whole control system is disturbed. It is obvious that the original purpose of shape control cannot be achieved, such as the possibility of occurrence. That is, since the conventional shape control method mentioned above is a shape control method in a single stand, it cannot be used at all in tandem rolling mills, and a tandem including the influence of each stand and the relationship with other controllers such as plate thickness control. The shape control method of a rolling mill is desired.

In the tandem rolling mill, the shape of the strip at the end of the final stand is

(a) The change of the profile of the cross section of the rolling material by the entrance side of a 1st stand by changes, such as a charging slab or a coil.

(b) Change in roll spacing of each stand due to roll bending.

(c) The change of the rolling load of each stand by the change of the material or plate | board thickness of the rolling material during rolling.

(d) Changes in tension before and after each stand for the same reason.

(e) It fluctuates by external hunting, such as the change of the roll crown of each stand, such as the increase of the heat crown by thermal expansion of a roll, or the decrease of the crown by abrasion of a roll.

Accordingly, an object of the present invention is to predetermine the shape change when various external heating occurs in the final stand exit in the rolling of a strip by a tandem rolling mill and to minimize the defective strip length according to the detection result. By changing the roll bender pressure or pressing force of the stand, shape control is effectively performed on the waveform of the edge of the strip or the extension of the center portion, or both.

Another object of the present invention is to provide a shape control method that can be used in combination with a plate thickness control system or an AGC system without any problems, and to achieve the best effect in consideration of the propagation of the rolled shape for each stand.

The basic idea of the present invention is to understand that the defective shape of the strip is the deformation of the strip caused by the difference in the elongation in the strip width direction, and the strip is divided into an arbitrary number in the width direction. It is based on defining the shape of the strip, taking into account the difference in the mean.

That is, the shape defects such as the edges of the strip edges or the extension of the center portion are caused by the nonuniformity of the tension width due to the nonuniformity of the width side of the elongation rate, and finally occur due to elasticity and plastic deformation. For example, as a result of elongation, the sheet thickness is rolled to the width side before rolling, and when there is a portion uneven in the elongation ratio of the width side without tension in the vicinity of the center of the rolled material, when tension is added to it, it is dependent on the elongation distribution. The tension distribution may be non-uniform, resulting in intermediate elongation.

When the shape of the strip is defined in consideration of the nonuniformity of the elongation at the width of the strip, the length before the rolling of the strip at the k-th dividing point of the width of the strip at the i-th stand exit is defined as Li, k, If the length after rolling is li and k, the average value of elongation is m

The shape at the k-th division point of the strip width side at the i-th stand exit side is represented by

Therefore, when Si and k are combined with Li and k in the denominator molecule and only the length after rolling is expressed, the following formula (1) is obtained.

In the normal rolling of tandem rolling mill, the distribution of the exit plate thickness and the exit plate speed of each stand is well known according to the so-called flow rate constant law. Since the product (i.e. volume) of is constant and there is no movement of the width of the material by rolling, the product of its length and plate thickness at each subdivided split point is the same at the entry and exit sides of the stand. The length of the strip at the same kth division point at the stand inlet side is l ₀ , k and the plate thickness at that point is h ₀ , k and the kth at the i-th stand exit side. If the plate thickness at the split point is set to hi and k, the following relationship holds for k = 1-m.

(In this case, l ₀ and k are constant at k = 1 to m, i.e., the premise is that the length of the charging material is constant in the width side)

Replacing li and k with the above formula (1),

(Where h ₀ , m, h _i , m represent the average values of the plate thicknesses at the first stand inlet side and the i-th stand outlet side, respectively)

Considering the variation in formation with respect to disturbance as described above, according to the whole derivative of the formula (2),

In this case, as the shape defects, hi, k or h _o , k is to occur in a difference of about 0.2% with respect to the respective average values hi, m or h _o , m, so hi, k / hi, m ≒ 1, h _o , k / h _o , m ≒ 1 Therefore, ΔSi, k is

Provided that ΔSi,

와 그 스탠드 입측 판단면 프로필(profile)의 변화에 의한 출측 형상 변화를 표시한 △Si,

로 나누어지며,ΔSi, k denotes ΔSi representing the exit shape change due to disturbance of the stand,

And ΔSi representing the exit shape change due to the change of the stand entrance judgment surface profile.

Divided into

(3)

(3)

는 탠덤압연기에 있어서만이 생기는 값이고 형상의 영향계수 Wi, k를 사용하면,ΔS _i ,

Is the value which is generated only in tandem rolling mill, and when the influence coefficients of shape Wi and k are used,

(4)

(4)

Is displayed.

The influence coefficients Wi and k are coefficients determined by rolling mill specifications, rolling pass schedules, and the like, and are determined in advance for each stand of the rolling mill to be applied. When an example is displayed, the rolling mill specifications and the schedule are the same as the first degree.

Target rolling mill: 5 stand cold tandem rolling mill

Work roll diameter: 610mmø

Back up roll diameter: 1455mmø

Roll fuselage length: 1370mm

Roll choke center length: 2330mm

Roll neck diameter (827 mmø)

Rolling Schedule

Strip width 959 mm

Division k = 28

Therefore, when ΔSi, k is expressed using this influence coefficient Wi, k, the equations (2 '), (3) and (4)

That is, in this equation (5), the shape change with respect to the disturbance in the i-th stand is the shape deviation of the stand of the front end and the change of the exit shape due to the disturbance of the stand, and the degree of influence determined by the specifications of the stand. It is expressed as a total with the change of the exit shape of the stand of the front end which adds to, and it is grasped including not only the stage but also the shape change in the stand of the front end.

The present inventors investigated the behavior of the shape change in a tandem rolling mill in detail about the stand cold tandem rolling mill using said Formula (5). That is, in addition to the experimental method showing the behavior of the plate thickness change of the tandem rolling mill, the above-described shape change block and AGC block were added to each stand when the material plate thickness was changed to step shape for the 5 stand cold tandem rolling mill. The waveforms of the edges of the strips and the elongated shape changes in the center portion were examined to obtain the same results as in FIGS. 2 and 3. The shape change pattern of each stand at the time of the plate thickness change of FIG. 2 takes the time (second) on the vertical side, and the horizontal side shows the shape function (ΔSi, k) corresponding to the waveform of the edge of the strip, In FIG. 3, the change of the shape function (DELTA Si, k) corresponding to the elongation of a center part is shown similarly.

As can also be determined from the drawing, the shape change due to the disturbance given to the first stand entrance in the state where the shape control is not performed at all is alleviated as it proceeds to the rear end sequentially, but the shape defect still occurs normally. .

This is also proved that the influence coefficient Wi, k of each stand becomes larger as the rear stand and becomes maximum at the final stand, as shown in FIG. 1. Therefore, in the shape control of the tandem rolling mill, Is the most effective. On the other hand, however, the AGC circuit is usually installed at the final stand of the tandem rolling mill, so that if the reduction force is changed in the shape control, the control system causes hunting.

Therefore, in the present invention, the shape control for changing the bender pressure by the roll bending device (waveform of the edge of the strip or the extension of the center part) includes the final stand because the thickness change by the bender is small. For the shape control (extension of the center part) which changes the shape, the final stand is not included and at the same time, the control is applied to the stand near the rear end having high control effect in consideration of the magnitude of the above-described influence coefficients Wi and k under such conditions. will be.

The shape control method of the present invention will be described with reference to the illustrated embodiment as follows.

In the shape control method of the present invention, the elongation of the split point in the width side as indicated by the above-described calculation formula at the final stand exit of the tandem rolling mill for shape defects such as the wave shape of the edge of the strip or the extension of the center portion as described above. The difference with respect to the average value of is detected as a shape change, and shape control is performed by changing the bender pressure or the pushing force of a predetermined stand based on this detection signal, and, as a shape detector, a suitable number of detection points in the width of the strip For example, the ones arranged near both ends of the width of the strip with respect to the waveform of the edge of the strip and near the center with respect to the extension of the center are used. Actually, the difference in the tension distribution is detected due to the change in the permeability. Or scattering of air micrometers or light It is preferable to use a non-contact detector, for example, to detect a shape change due to irregularities on the plate thickness side.

FIG. 4 shows a control block when the shape control is performed in the fourth and fifth stands with respect to the wave shape of the edge of the strip or the extension of the center part by changing the roll bender. Uniloilers (2) (3) (4) (5) (6) are the first, second, third, fourth, fifth, and stand (7) tension tensioners for winding the strip after rolling, respectively. (tension reel), (8) is the shape detector described above. The output from the shape detector 8 is continuously detected for the strip coming out from the fifth stand 6 which is a signal corresponding to the waveform of the edge of the strip or the elongated shape of the center as described above. This detection signal is changed with respect to a signal having a magnitude exceeding the deadband of the differential output generators 9 and 10 of the respective vendor output deviation derivatives 9 and 10 of the fourth and fifth stands. It is output as a deviation derivative value as the minute and is converted into a signal indicating the change of the change to the integrators 11 and 12 and applied to the vendor output signal controllers 13 and 14. The vendor output signal control paper 13, 14 is composed of a proportional circuit, an integration circuit, and a derivative circuit having a predetermined gain, and the output signal from the controller 13, 14 is used as a vendor output. Inputs to the respective vendor drive control devices 17 and 18 of the fourth stand and the fifth stand via limiters 15 and 16, and the elongation detected by the shape detector 8 is the polarity of the deviation. And the respective roll bender devices of the fourth stand 5 and the fifth stand 6 so as to increase or decrease the bender pressure corresponding to the amount thereof. In this case, for example, the X-ray thickness meter 19 arranged on each exit side of the fifth stand and the first stand by the rolling control method shown in Japanese Unexamined Patent Application Publication No. 47-2018, that is, the on-line calculator 31. Due to the measurement inputs from) and (20), the roll speed controllers 21, 22, 23, 24, 25 and the roll reduction controllers 26, 27, 28 of each stand. (29) and (30) are applied to the shape control of the present invention by simultaneously applying a rolling control system for controlling the plate thickness in accordance with a predetermined program, respectively, and it is possible to carry out rolling work by keeping the final stand exit plate thickness constant at the set value. .

5 shows a control block when the shape control is performed in the third stand and the fourth stand with respect to the extension of the central part by changing the pressing force, and in the figure, the parts denoted by the same reference numerals indicate that they correspond. do.

The output from the shape detector 8, in this case, is a signal corresponding to the elongation and shape of the center portion of the strip, and this detection signal is the angular roll installation interval deviation differential value generator of the third stand 4 and the fourth stand 5. Input to (43) (44), and output as a deviation non-differential value for the signal having a magnitude exceeding the deadband of the corresponding deviation derivative generator (43) (44) and the change in the integrator (45) (46) It is converted into a signal indicating the sum of and added to the roll installation interval output signal controllers 47 and 48. The roll installation interval output signal controllers 47 and 48 are used to control the signal reduction due to changes in the rolling conditions that are predicted in advance in order to keep the rolling force patterns of the third and fourth stands constant at the thickness of the final stand exit side. The roll reduction control devices 28 and 29 of the third stand 4 and the fourth stand 5 are changed to correspond to the polarity and the size. In fact, as described above, since the rear end is more effective in shape control, the roll reduction control device 29 of the fourth stand 5 mainly changes the reduction force for shape correction, and The roll reduction control device 28 compensates for the reduction in the reduction force for shape correction in the fourth stand, and changes the reduction force for keeping the final stand exit plate thickness constant.

In the control block shown in FIG. 5, since the shape reduction is performed by changing the reduction force, the final stand is excluded from the application of the control in order to prevent hunting due to the action of the final stand with the AGC circuit. In FIG. 5, the shape control is performed as described above in the two stands near the rear end, that is, the third stand and the fourth stand, and at the same time, the final stand exit plate thickness is kept constant. When the stand exit plate thickness is kept constant by the rolling control method using the above-described online calculator 31, as shown in FIG. 6, the controller of FIG. It is possible to do

In the above-described control block, the control method in the embodiments of FIGS. 4, 5 and 6, in particular as an example of the control block for the extension of the center part, is selected by the expected magnitude of the output signal of the shape detector 8. The control method of FIGS. 4, 5, and 6 may be applied in order from the case where the output number of the shape detector is small. In practice, the control method of each of the coils of the rolling pass schedule can be switched. It is good to construct the control circuit.

In the above description, the shape control is performed solely with respect to the waveform of the edge of the strip or the extension of the center portion. However, when both of them are controlled, the control method of FIG. 4 is applied to the waveform of the edge of the strip. Further, the control circuit may be configured so that the control method of FIG. 5 or 6 is applied to the extension of the central portion, and the combination is simultaneously performed.

The result obtained when the shape control method (FIG. 4) of this invention demonstrated above is applied with respect to the 5 stand cold rolling mill is shown in FIG.

In this case, although the normal AGC circuit is provided in the first stand and the fifth stand, the waveform of the edge of the strip caused by the disturbance given to the final stand is significantly reduced by the correction operation of the present invention. In the case of applying the control only to the stand, there is no problem in reducing the control effect and hunting.

In addition, as shown in FIG. 8, it was confirmed that the variation in tension between the respective stands was as small as 1% of the normal tension at most, and there was no fear of causing trouble in the work.

Although the above-mentioned details explained about the cold tandem rolling mill, the shape control method of this invention is not only the shape control of a cold tandem rolling mill, For example, the cold tempering mill which rolls two or more stands through tension, for example. It can be applied entirely to the back, and needless to say the same for the hot tandem rolling mill. In the hot tandem rolling mill, there is no uncoiler 1 as shown in FIG. 4, and a looper is disposed between the stands, and the tension between the stands by the yiper is extremely small. Although it can be ignored, it is considered to be the same phenomenon as in the case of cold tandem rolling mill in that the other influence of the front end has a rear end. Therefore, the shape control method of the present invention can be effectively applied to a hot rolling mill without any problem. It is possible.

As described above, according to the shape control method of the present invention, it is possible to make shape control on the waveform of the edges of the strips or the extension of the center portion in the hot and cold tandem rolling mills alone or both effectively. It is different from applying the control method in the stand as it is, and since all propagation of the shape change is taken into consideration for each stand, it is possible to detect the shape defect and correct the shape in the shortest time. The use of another control system, for example, AGC and other plate thickness control systems, can be used without any problems, and in addition to these control effects, a remarkable shape correction effect can be achieved, and thus quality control based on improvement of product recovery rate. Work management benefits cannot be measured individually.

Claims (1)

In the rolling of the strip by hot or cold tandem rolling mill, the shape of the exit strip of the final stand is detected and the signal corresponding to the waveform of the edge of the strip or the extension of the center part is taken out, and at least close to the rear due to the detection signal. A shape control method in a tandem rolling mill characterized by changing the bender pressure of two or more stands and controlling the plate thickness so as to uniformly correct the final stand exit plate thickness.

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