JP2015223616A - Method for controlling the thickness of the trailing end of the rolled material in a hot rolling mill and the method for controlling the thickness of both ends - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plate thickness control method improving a product yield by preventing a plate thickness deviation in a pinch-out side tail end and lessening the plate thickness deviation of the end of a finished plate in hot finish rolling of a high-strength steel plate, and particularly to provide the method capable of surely and stably preventing occurrence of the plate thickness deviation in the end even in the materials to be rolled of various steel types having different deformation resistances and of various plate thicknesses.SOLUTION: A control method for the plate thickness of a rolling material includes detecting that the position of the tail end of the rolling material during passing at the rear side in a rolling direction approaches to a roll caliber tool at a preset distance in a finish rolling pass, obtaining the fluctuation change speed of the opening of roll gap by differential of fluctuation in the opening of the roll gap after tail end detection, and controlling the operation of a hydraulic cylinder so as to negate the fluctuation speed.

Description

  The present invention relates to a method for controlling the thickness of a finished rolled plate (hot rolled plate) when hot rolling a steel plate having a relatively large hot deformation resistance, such as a stainless steel plate. In particular, a sheet at the tail end of the biting side of the rolling material in a hot rolling mill for controlling the thickness deviation at the end (tail end) on the biting side of the material to the rolling mill Thickness control method, and in combination with that method, the plate thickness at both ends of the material is also controlled by controlling the plate thickness at the end portion (tip portion) on the material biting side, thereby reducing the thickness deviation at both ends of the material. It relates to a control method.

In hot rolling of steel plates, particularly finish rolling, it is necessary to control the plate thickness so that the plate thickness after rolling reaches the target plate thickness with a high yield.
Various methods are known as plate thickness control methods. In hot rolling of steel plates, the rolling load during rolling is detected, and from the relationship between the plate thickness and the plastic coefficient (deformation resistance), A so-called AGC control (Automatic Gauge Control) system that grasps the thickness of the delivery side and controls the distance between the upper and lower rolls (roll gap) is widely applied. In addition, when the AGC control method is applied, so-called APC control (Automatic Position Control) is often applied to detect the roll position and control the roll position so as to keep the pass line during rolling constant. .

  An example of a conventional general control system for AGC-APC control in such a hot finish rolling mill is schematically shown in FIG.

  In FIG. 1, a rolling mill 10 includes a pair of upper and lower work rolls 11A and 11B into which a steel plate 20 as a material to be rolled, for example, a stainless steel plate 20 is bitten, and upper and lower backups for backing up these work rolls 11A and 11B. It is set as the structure which has roll 12A, 12B. The upper and lower work rolls 11A and 11B are each configured to be rotated in the reverse direction by a rotation driving device (not shown) to reduce the steel plate 20 to a predetermined plate thickness. In the illustrated example, the upper backup roll 12A and work roll 11A, and the lower backup roll 12B and work roll 11B are supported by chocks (not shown) so that the vertical position can be adjusted. In the case of this example, the upper backup roll 12A and the work roll 11A are adjusted in the vertical position by an electric motor (not shown). On the other hand, the upper and lower positions of the lower backup roll 12B and the work roll 11B are adjusted by the hydraulic cylinder 13.

  The hydraulic cylinder 13 is supplied with hydraulic pressure from a hydraulic pump 14 via a servo valve 15, and the vertical position of the lower backup roll 12 </ b> B and the work roll 11 </ b> B is adjusted by controlling the servo valve 15. It has become. The hydraulic cylinder 13 is provided with a position detector 16 for detecting the position in the vertical direction. Here, since the hydraulic cylinder 13 is indirectly in contact with the lower work roll 11B via the lower backup roll 12B, the vertical position of the lower work roll 11B is substantially detected. .

  On the other hand, the upper backup roll 12A is provided with a load cell 17 for detecting a load applied to the backup roll 12A (reaction force applied from the material to be rolled during rolling), and the distance between the upper and lower work rolls 11A and 11B. That is, an opening gauge 18 for detecting the roll gap s is attached. The opening gauge 18 actually detects the position of the backup roll 12A by a position detector, and calculates the roll gap (opening) from the relationship with the detection position by the lower position detector 16 described above. It is normal to do.

  On the other hand, the control part for electrically controlling the operation of the servo valve 18 on the basis of each detection signal or the like basically has the function of the servo valve 18 to control the interval (roll gap) between the upper and lower rolls. The AGC control unit 30 sets the gain, and the APC control unit 40 controls the roll position so as to keep the pass line during rolling constant according to the gain.

  And the signal regarding the detected value of the roll position or the roll gap opening degree s from the position detector 16 and the opening degree meter 18 as described above is given to the AGC control unit 30, and the first in the AGC control unit 30. The change Δs of the opening s is calculated by the first calculator (subtractor) 32 via the lock-on memory 31. On the other hand, the actually measured load (actual reaction force) F detected by the load cell 17 is also given to the AGC control unit 30 and the second reaction force FL stored in the target thickness portion in the AGC control unit 30 is stored. The reaction force change (F-FL) is calculated by the second arithmetic unit (subtractor) 34 through the lock-on memory 33, and given from a computer (not shown) by the third arithmetic unit (divider) 35. The value of (F−FL) / M is calculated after correction with the mill constant M.

Further, the change Δs of the opening s from the first calculator 32 and the value of (F−FL) / M from the third calculator 35 are given to the fourth calculator 36. The estimated thickness difference Δh from the target thickness is obtained, and the fifth computing unit is calculated from the relationship between the estimated thickness Δh obtained from the fourth computing unit 36 and the plastic coefficient Q. 37, the value of (M + Q) / M is calculated. The value of (M + Q) / M is given to the AGC control unit 38, and is given to the AGC control unit 38 as an AGC command signal (gain signal) G for hydraulic cylinder control. Further, the AGC command signal G is It is given to the APC control unit 41 in the APC control unit 40, and correction is performed based on the cross-sectional area of the hydraulic cylinder, the hydraulic system response time, etc., and the final servo operation signal SB is given to the aforementioned servo valve 16.
In this way, control is performed to keep the exit side plate thickness of the finish rolling mill constant during rolling and to keep the pass line constant.

  By the way, it is known that the material rolled by the finish rolling mill tends to be thicker at both end portions in the length direction (rolling direction) than the central portion (steady rolling portion). That is, the plate thickness deviation increases at both ends. In particular, in finish rolling such as a stainless steel plate having high strength and a large deformation resistance and a larger number of rolling passes than a general carbon steel, the thickness deviation at both end portions is usually large. . Here, it is normal to cut off both end portions where the thickness deviation is large as a defective part, but the length of the portion outside the tolerance (within tolerance) with respect to the target thickness due to the large thickness deviation at both ends. If it is long, the product yield will be reduced. In addition, if the plate thickness deviation is large, there is a problem that the quality of the product is deteriorated, for example, a welding failure is caused in an application in which butt welding is used.

  Here, as described above, the reason why the thickness deviation of both end portions is large is that when viewed in one rolling pass, the portion immediately after being bitten by the roll bite of the rolling mill, that is, the biting side end ( Since it corresponds to the tip side portion with reference to the rolling direction, it is hereinafter referred to as “tip portion”) and the portion immediately before biting from the roll bite of the rolling mill, that is, the biting side end portion (tail with reference to the rolling direction). Since this corresponds to the end portion, it will be hereinafter referred to as “tail end”), but there are some common points, but it is slightly different. However, in the hot rolling of stainless steel thick plates, it is common to apply reverse type rolling in which the rolling direction is alternately reversed and rolled by repeating a number of passes. The increase in the plate thickness deviation at the biting side tip and the increase in the plate thickness deviation at the biting side tail end in a certain pass are superimposed, resulting in a large plate thickness deviation at both ends of the finished rolled plate. Show the trend.

FIG. 2 schematically shows an increase in the thickness deviation at both end portions of the hot rolled plate. In FIG. 2, the horizontal axis indicates the length direction of the rolled up plate, and the vertical axis indicates the plate thickness. As shown in FIG. 2, the longitudinal end portions P1, steady rolling portion P2 excluding the central longitudinal side P0, whereas the thickness variation with respect to the target plate thickness t ₀ is relatively small, in longitudinal end portions P1, P2, locally thickness is increased, it may exceed large allowable thickness limit t _c, according to the experience of the present inventors, the stainless steel (SUS304) In the hot finish rolling with a finish target plate thickness of 22 mm, a plate length of 13000 mm, and a plate width of 2600 mm, the portions with a thickness deviation of about 0.5 to 1.0 mm at the maximum are long at both ends P1 and P2 in the length direction. It has been confirmed that it occurs over a length of about 500 to 1000 mm.

  By the way, as described above, the influence of the impact load when the material to be rolled is bitten by the roll bite is large as a cause of the large thickness deviation at the biting side end (tip portion) of the hot rolled plate. it is conceivable that.

  That is, in recent hot rolling mills, at least one of the upper and lower rolling rolls is supported by a hydraulic cylinder so that the vertical position can be adjusted as described in the example of FIG. Generally, it is configured so that it can be adjusted by hydraulic pressure, so the oil in the hydraulic cylinder is momentarily compressed by the impact load at the time of biting, the hydraulic cylinder sinks, and the lower roll The position fluctuates in the direction of opening the roll gap. As a result, the roll gap instantaneously increases and the plate thickness becomes excessive at that portion. In particular, when the material to be rolled is high-strength stainless steel and its plate thickness is large, the impact load described above is also large, and the instantaneous compression amount of oil in the hydraulic cylinder due to the impact load increases, As the gap becomes larger, the thickness deviation amount becomes excessive, and the length of the excessive portion becomes longer.

  Depending on the configuration of the rolling mill, the roll whose vertical position is adjusted by the hydraulic cylinder may be the upper roll, but generally there are many rolling mills in which the lower roll is supported by the hydraulic cylinder. Now, as described with reference to FIG. 1, it is assumed that the upper roll is supported by the electric cylinder so that the vertical position can be adjusted, and the lower roll is supported by the hydraulic cylinder so that the vertical position can be adjusted. Shall. That is, the momentary impact load applied when the material to be rolled is bitten by the roll bite compresses the oil in the hydraulic cylinder of the lower roll (that is, the oil column sinks), and the lower roll The description will proceed on the assumption that the position is instantaneously moved downward, and as a result, the roll gap is instantaneously opened.

The reason for the increase in thickness deviation at both ends of the hot finish rolled rolled plate is not only the impact load at the time of biting as described above, but also the variation in the length direction of the material temperature at the time of rolling is greatly affected. it seems to do.
That is, in general, in hot finish rolling of stainless steel thick plates, it is usual to repeat rolling a plurality of times by the reverse method, and during that time, the temperature of the material to be rolled tends to decrease gradually, At both end portions in the direction, the temperature decreases more severely than the central portion in the length direction. That is, both end portions in the length direction are supercooled. Such a supercooled portion is not easily crushed by the upper and lower work rolls because of the large deformation resistance of the material, and at the same time, the impact load at the time of biting is increased, so that the opening of the roll gap is also increased. And it is thought that these act synergistically, and an excessive thickness deviation will occur at both ends of the material to be rolled, particularly at the tip portion on the biting side.

  In particular, stainless steel has higher material strength than ordinary steel and has a higher deformation resistance than ordinary steel even at hot rolling temperatures, and therefore the influence of the above-described supercooling at both end portions becomes stronger. In addition, since stainless steel has a larger deformation resistance than ordinary steel, the number of hot finish rolling passes is usually higher than that of ordinary steel. The temperature drop is also greater than that of plain steel. For this reason, it is considered that the above-described overcooling at both end portions becomes intense, and finally the plate thickness deviation at both end portions is further increased.

  According to the experience of the present inventors, the temperature in the center portion in the longitudinal direction is 1100 ° C. in the hot finish rolling final pass of stainless steel (SUS316) with a finish target plate thickness of 4 mm, a plate length of 19000 mm, and a plate width of 1220 mm. In some cases, it has been confirmed that the temperature at both ends decreases to about 700 to 800 ° C., and the deformation resistance at both ends in that case is several times that of ordinary steel.

  On the other hand, at the tail end on the biting side in hot finish rolling, unlike the tip on the biting side, the impact load at the time of biting does not act, but as described above, the end in the length direction of the material to be rolled This is the same as the tip portion on the biting side in that supercooling occurs at the portion. Therefore, in the finish rolling of stainless steel, which has a particularly large deformation resistance and tends to increase the number of rolling passes, the plate thickness fluctuates due to supercooling even on the biting side. Thus, if only one pass in finish rolling is taken into consideration, the impact load at the time of biting and the variation in temperature distribution in the length direction (supercooling of the biting side tip portion) at the biting side tip as described above. ), A large plate thickness deviation occurs. On the other hand, the tail end on the biting side is considerably caused mainly by variations in the temperature distribution in the length direction (supercooling on the biting side tail end). A plate thickness deviation of the size will occur. FIG. 3 schematically shows the state of occurrence of thickness deviation considering only one pass. However, as already mentioned, in the hot rolling of stainless steel thick plates, it is common to apply reverse rolling in which the rolling direction is alternately reversed and repeatedly rolled. Since the side front end and the biting side tail end are reversed, the plate after the finishing pass finally has a large thickness deviation of about the same degree at both ends of the plate as shown in FIG. Usually, it exists.

  By the way, even if the roll gap is momentarily opened because the hydraulic cylinder supporting the lower roll (hydraulic roll) momentarily sinks due to the impact load at the biting side tip, a certain period of time is required. After the elapse of time, the lower roll returns (ascends) so that the oil column of the hydraulic cylinder is returned to the initial setting state and the roll gap returns to the initial setting value (that is, to the roll gap where the target plate thickness should be obtained). ) However, if no control is performed at that time, it takes a considerable time (for example, about 0.2 to 0.3 sec) to return to the initial setting position. As described above, it occurs over a considerable length (for example, 500 to 1000 mm).

  Here, in the conventional general AGC-APC control method, the position detector detects the position of the lower roll for the pass line control (APC control), and the pass line is always kept at a normal position. In general, the position of the side roll is controlled. In this case, if the position detector detects that the hydraulic cylinder sinking amount of the lower roll due to the impact load as described above exceeds a predetermined threshold value, the detection signal is sent to the APC control unit via the AGC control unit. A function of raising (returning) the lower roll works so as to return to the normal pass line position. However, it takes a considerable amount of time for the lower roll to return after it has been detected that the amount of depression of the lower roll has exceeded a predetermined threshold value. It is difficult to shorten the length of the excessive thickness deviation portion of the leading end portion on the insertion side, and the excessive thickness deviation portion remains over a considerable length.

  On the other hand, in order to compensate for the momentary opening of the roll gap at the time of biting, the APC control is turned off at the start of biting, and the position of the lower roll before the biting start is set during normal rolling. In order to prevent the tip plate from becoming excessively thick due to the depression of the hydraulic cylinder when it is bitten, it has been conventionally performed. This is a so-called “sinking compensation method when biting”, commonly referred to as a “getter wearing method”. By making the position of the position high (with gettering on), the roll gap does not become excessively large when an impact load is applied. It is something to try. In this case, in general, in advance, from the past results, predict the height and period to wear the geta, set the predicted value in the control unit, when the getter wearing period has passed, Usually, the APC control is functioned to control the position of the lower roll to the position of the normal pass line.

However, the getter wearing method as described above has the following problems.
That is, raising the position of the lower roll at the start of biting by a predetermined height above the pass line during normal rolling (during steady rolling) sets the roll gap smaller than during regular rolling. It means to keep. This, in turn, results in an increase in the impact load at the time of biting. In practice, there has been a limit to reducing the impact load and reliably solving the aforementioned problems.

  Moreover, in an actual rolling mill, it is necessary to roll various steel types with different deformation resistances and various steel plate thicknesses. On the other hand, the amount of subsidence of the hydraulic cylinder due to the initial play load at the start of biting varies greatly depending on the difference in deformation resistance inherent to the material and the difference in plate thickness. Therefore, it is extremely difficult to predict an appropriate amount of gettering and set an appropriate amount of gettering and time appropriately for all steel types and plate thicknesses. For this reason, optimal control is not always performed, and in practice, it has been difficult to reliably suppress the occurrence of excessive tip portion thickness deviation as described above.

  Further, in the gettering method, when the gettering period elapses as described above, the APS control is functioned to control the lower roll to the position corresponding to the normal pass line. When the amount of gettering is excessive, the lower roll rises to a position higher than the normal position at the end of gettingtering, so-called hunting occurs, and the plate thickness fluctuates. Even within the plate thickness tolerance, non-uniform plate thickness may result in a defective product.

  Therefore, the so-called gettering method is not the best measure for suppressing the tip thickness deviation, and more reliably and stably reducing the thickness deviation at the biting tip. A fundamental solution is needed.

  On the other hand, with regard to the plate thickness deviation of the tail end on the biting side, a large load (reaction force) acts when the supercooling portion (the portion with large deformation resistance) on the biting side is bitten by the roll. As with the biting side tip, the hydraulic cylinder that supports the lower roll sinks, and the roll gap opens. Even in this case, the lower roll returns (rises) after a certain period of time. However, if no control is performed at that time, it takes a considerable time (for example, about 0.2 to 0.3 seconds) to return to the initial setting position. Therefore, it is practically difficult to prevent the occurrence of the thickness deviation of the tail end portion because it passes through the roll gap.

  In addition, when the conventional general AGC-APC control method is applied as described above, the amount of depression of the hydraulic cylinder in the lower roll due to the large deformation resistance of the supercooling portion on the biting side has a predetermined threshold value. If it is detected by the position detector that the value has been exceeded, the detection signal is given to the APC control unit via the AGC control unit, and the function of pushing up the lower roll works. However, it takes a considerable amount of time for the lower roll to return after it has been detected that the amount of depression of the lower roll has exceeded a predetermined threshold value. It was difficult to reduce the thickness deviation at the leading end on the delivery side.

  Further, the method referred to as the “sinking subsidence compensation method” as described above, commonly referred to as “getter wearing method”, cannot be applied to the tail end portion on the biting side. That is, in the gettering method, the amount of subsidence at the time of biting is estimated, and the position of the lower roll immediately before biting is set higher than the position of the steady rolling state. It cannot be applied to the thickness control of the tail end portion on the biting side that occurs following the rolling.

By the way, the technique of patent document 1 (Unexamined-Japanese-Patent No. 2013-81969) is proposed as a sheet thickness control method of a rolling mill aiming at making the sheet thickness of a rolling mill approach the target value reliably.
The sheet thickness control method of Patent Document 1 basically calculates a rolling load fluctuation value ΔP ′ that satisfies the gauge meter type while considering the dynamic characteristics of the rolling mill, and the dynamic characteristic rolling load fluctuation value ΔP. 'Is used to determine the roll gap correction amount ΔS, and the correction amount ΔS is applied to the rolling mill. Here, the gauge meter formula includes a mill constant, and therefore, in this method, control is performed in consideration of factors relating to the rolling mill body such as elongation of the roll itself. Therefore, it is considered that this is not effective for increasing the plate thickness at the biting side tip portion due to the momentary opening of the roll gap due to impact load and the biting side tail end portion which is not substantially related to the mill constant. Further, in the technique of Patent Document 1, even if a load is detected due to biting or the arrival of the supercooling portion on the tail end side, the response is delayed with respect to an instantaneous roll gap opening, and in practice It seems that it is difficult to suppress the increase in the plate thickness at both end portions including the tail end portion on the biting side.

  Patent Document 2 (Patent No. 3350140) proposes a method for controlling the thickness of the biting end of plate rolling. The technique disclosed in Patent Document 2 basically assumes AGC control, but predicts the next path from the measured value of the previous path and controls the roll opening degree in the next path. Such a control technique based on prediction from the previous pass has a problem that appropriate control cannot always be performed for rolling of various steel types and various plate thicknesses having different deformation resistances. Further, the method of Patent Document 2 has a problem that it cannot cope with the plate thickness deviation of the tail end portion on the biting side.

  Further, in Patent Document 3 (Japanese Patent No. 2885601), on the premise of AGC control, the roll opening at the time of biting is set larger than the opening at the time of normal rolling based on the prediction, so that the impact at the time of biting is set. It is intended to compensate for the subsidence of the hydraulic cylinder due to the load. In this technique, the roll opening at the time of biting is set in the opposite direction to the gettering method as described above, and in this technique, the impact load at the start of biting becomes small, Although it is considered that the amount of subsidence of the hydraulic-side roll is reduced, conversely, if the setting is inappropriate, there is a possibility that the plate thickness of the biting-side front end portion will rather increase. Moreover, since the amount of sinking at the time of biting is based on the prediction from the previous pass as in the technique of Patent Document 2, it is not always appropriate to control various steel types with different deformation resistance and various sheet thicknesses. There is a problem that cannot be performed. Further, even the method of Patent Document 3 has a problem that it cannot cope with the plate thickness deviation of the tail end portion on the biting side.

  Further, in Patent Document 4 (Patent No. 3278120), as a method for controlling the thickness of the biting side end, the roll opening at the time of biting is increased (so-called gettering), and AGC is performed. Although it is disclosed to control, this technique has various problems described with respect to the getter wearing method, and as described above, this method can be applied to the tip on the biting side. There is a problem that it is limited to the portion, and it is impossible to deal with the plate thickness deviation of the tail end portion on the biting side.

  Furthermore, in Patent Document 5 (Japanese Patent Laid-Open No. 2000-288613), as a sheet thickness control method based on the AGC control method, a roll gap fluctuation amount during rolling, a roll gap value, and a roll gap fluctuation speed (that is, roll gap fluctuation speed). A method has been proposed in which the roll gap is automatically adjusted to reduce the plate thickness deviation by feeding back the amount time differential value) to the roll position controller (AGC controller). In this proposed method, since the roll gap is feedback controlled not by the roll gap fluctuation amount but by the roll gap fluctuation speed (differential value), it is relatively responsive compared to the feedback control by the roll gap fluctuation amount. In practice, however, the roll gap passage time at the portion where the thickness deviation occurs on the tail end side (the time from the start of the tail end deviation due to overcooling until the tail exits the roll gap) is considered. ) Is extremely short, and it is difficult to reliably suppress the thickness deviation on the tail end side. That is, in the technique of Patent Document 5, when the roll gap varies, the variation speed (differential value) is calculated, the value is given to the AGC control unit, and further by the control signal from the AGC control unit. The servo system of the hydraulic cylinder is controlled, and this causes the hydraulic cylinder to operate, and finally the roll gap is corrected (adjusted). The tail end slips out of the roll gap until the roll gap is actually adjusted after the occurrence of deviation at the part, and it is difficult to actually suppress the plate thickness deviation at the top end part. Conceivable. That is, the control method of Patent Document 5 has a problem that the responsiveness is not sufficiently good and the thickness deviation of the tail end portion on the biting side cannot be reliably suppressed.

  Further, in the control method of Patent Document 5, since the responsiveness is not sufficiently good as described above, there is a problem that it is not possible to surely suppress the tip side plate thickness deviation on the biting side. That is, the opening of the roll gap due to the impact load at the time of biting (sinking of the lower roll) is an abrupt and instantaneous phenomenon as described above. Even if it is detected at an early stage, the roll gap is often widened until the hydraulic cylinder actually operates and the adjustment of the roll gap is started. The deviation was also difficult to be surely kept small.

JP 2013-81969 A Japanese Patent No. 3350140 Japanese Patent No. 2885601 Japanese Patent No. 3278120 JP 2000-288613 A

  The present invention has been made against the background described above, and when hot-rolling a high-strength steel sheet having a high deformation resistance as represented by stainless steel, the thickness deviation at the tail end on the biting side is reduced. To provide a plate thickness control method that can reliably and stably produce a hot-rolled plate product of good quality with little variation in plate thickness while suppressing product reliably and stably and thereby improving product yield. This is the first issue. Moreover, at the same time as suppressing the plate thickness deviation at the biting side tail end, the plate thickness deviation at the biting side tip is also reliably and stably suppressed. Reduced sheet thickness deviation and, in turn, reduced the length of excessively thick parts at both ends in the length direction of rolled-up sheets, improving product yield, and good quality hot rolled sheets with less variation in sheet thickness It is a second object to provide a plate thickness control method capable of manufacturing a product reliably and stably. In particular, it is possible to reliably and stably suppress the occurrence of thickness deviations at the tail end of the biting side or both end portions including the same for various steel types having different deformation resistance and materials to be rolled having various thicknesses. Providing a plate thickness control method that can be obtained is also a major issue.

  In order to solve the problems as described above, as a result of repeated various experiments and researches by the present inventors, as the sheet thickness control of the biting side tail end, the position of the tail end in the finish rolling pass is detected, Obtain the rate of change of the roll gap opening (the differential value of the amount of change in the roll gap opening) from the point when the position approaches the upper and lower roll bites up to a predetermined distance. The control signal corresponding to the value of the roll gap opening change speed is directly given to the servo system of the hydraulic cylinder so as to cancel the differential value of the degree change degree), and the hydraulic cylinder is controlled in the roll gap closing direction (therefore, the roll position is moved). Control)), it becomes possible to correct the roll gap (reduce the roll gap) at an early point in time, and as a result, The thickness deviation due to cooling, etc. can be minimized and at the same time the length of the excessive thickness deviation area to be discarded as a defective part can be minimized, and the steel grades and thicknesses with different deformation resistance are different. It has been found that it can be applied in common to the material to be rolled.

  In other words, the steel grades with different deformation resistance and rolled materials with different plate thicknesses have different roll gap fluctuation magnitudes when biting, but the roll gap fluctuation patterns themselves are substantially the same. Recognized.

  That is, at the end of rolling in a certain pass, it is detected that the tail end of the material to be rolled is close to the roll bite, and if the portion where the deformation resistance is actually large (supercooled portion) is caught between the upper and lower rolls, The increase in the opening of the roll gap is started and the increase in the plate thickness is also started, but the start of the increase in the plate thickness immediately appears as a differential value (change speed) of the variation amount of the opening increase in the roll gap. For example, in the steady rolling state in the central portion in the length direction, there is substantially no variation in thickness, and in that state, the differential value of the variation amount of the roll gap opening expansion is substantially zero. From the further progress of rolling in the rolled state, if the opening of the roll gap is started by biting between the rolls of the part having a large deformation resistance on the tail end side (supercooled part) as described above, The differential value has a pattern of suddenly changing from zero to a certain direction. It was recognized that such a pattern is substantially common regardless of the steel type and plate thickness.

  If the change rate (differential value) of the roll gap opening expansion is used as a starting factor for control instead of the fluctuation amount of the roll gap opening expansion itself, the supercooling part on the tail end side reaches between the rolls. At an extremely early stage, it is possible to detect the opening of the opening of the roll gap at an early stage and start the operation control of the hydraulic cylinder. As a result, the opening of the opening of the roll gap is much smaller than in the case of no control. It was recognized that it can be controlled appropriately without being affected by the difference in steel type and plate thickness.

  Furthermore, when the material to be rolled is biting as described above, the roll gap opening is detected, the change speed (differential value of the opening change amount) is obtained, and the operation of the hydraulic cylinder is performed to cancel the change speed. In controlling the operation of the hydraulic cylinder obtained from the obtained position change speed (control command signal) directly to the servo system of the hydraulic cylinder, that is, not the so-called AGC control unit, It is preferable to apply to the end of the hydraulic cylinder control system (generally, the APC control unit), thereby further improving the control responsiveness and the length of the plate thickness deviation and the plate thickness deviation excessive region at the biting end. As a result, it has been found that the thickness can be reliably and stably suppressed to the minimum, and an invention has been made for a method for controlling the thickness of the tail end on the biting side.

  On the other hand, it has been found that the same concept can be applied to the thickness control of the biting side tip. That is, the position of the hydraulic cylinder is detected when the tip of the material to be rolled is caught in the roll roll rolling mill of the rolling mill, and the position change speed (the differential value of the position change amount; therefore, the hydraulic cylinder) (The differential value of the position change amount of the roll on the side supported so that the position can be adjusted) is obtained, and the hydraulic cylinder is controlled in the roll gap closing direction so as to cancel the position change speed (differential value of the position change amount) ( Therefore, by controlling the roll position movement, it becomes possible to correct the roll gap at an early stage (return the roll gap back to the roll gap at the time of normal rolling). It is possible to minimize the maximum absolute amount of subsidence of the hydraulic cylinder due to overcooling at both ends in the length direction. Te is recognized that it is possible to minimize the thickness deviation of the tip portion of the biting side in the rolling up material. Also in this case, it has been found that, similarly to the biting side tail end portion, it can be commonly applied to steel materials having different deformation resistances and rolled materials having different plate thicknesses.

  That is, as described above, the steel type with different deformation resistance and the rolled material with different plate thickness differ in the magnitude of the position fluctuation (sinking) of the hydraulic cylinder at the time of biting and the duration thereof, It was newly recognized that the hydraulic cylinder position variation (sinking) pattern itself is substantially the same. In other words, the position fluctuation suddenly occurs from the moment when the tip of the material to be rolled is caught in the roll bite, but the speed of the position fluctuation (hence the absolute value of the time differential value of the position) is from the moment of biting. If the position fluctuation speed exceeds the maximum, the position change speed gradually decreases, and after the position fluctuation amount reaches the maximum value, the position of the hydraulic cylinder resulting from the impact at the time of biting by APC control becomes the target position. Recognize that the subtraction pattern is converged to the maximum, and that the time when the absolute value of the position change speed in the subtraction pattern reaches the maximum is earlier than the time when the subtraction amount reaches the maximum value. . It was recognized that such a pattern at the time of biting is basically common to steel materials having different deformation resistances and materials to be rolled having different plate thicknesses.

  Therefore, when controlling the thickness of the tip on the biting side, if the subsidence change rate (position change rate) is used as a starting factor for control, not the magnitude of subsidence (position change amount) of the hydraulic cylinder itself. At the very beginning of biting, that is, before the point when the amount of subsidence becomes maximum in the case of no control, control the operation of the hydraulic cylinder at an early stage so that the maximum amount of subsidence is less than in the case of no control. Can be significantly reduced, and the length of the region where the thickness deviation increases due to subduction (length from the biting side tip position in the length direction of the rolled plate) can be shortened, and the difference in steel type and thickness It was found that it can be controlled properly without being affected by And if the plate thickness control for the biting side tip and the plate thickness control of the biting side tail end are used in combination, both end portions are rolled up as finished rolled plates by a reverse rolling mill. As a result, it was found that the length of the large thickness deviation area at both ends so that the thickness deviation is less than the allowable tolerance can be shortened, and the invention for the method of controlling the thickness at both ends has been made. It is.

  In addition, as described above, the position of the hydraulic cylinder is detected immediately before or during biting of the material to be rolled, and the speed of subtraction (position change) (differential value of the position change) is obtained, and the position change When controlling the operation of the hydraulic cylinder so as to cancel the speed (differential value), a signal (control command signal) for controlling the operation of the hydraulic cylinder obtained from the obtained position change speed is sent to the servo system of the hydraulic cylinder. To the end of the hydraulic cylinder control system (generally, the APC control unit) rather than the so-called AGC control unit. It has been found that the thickness deviation of the tail end portion and the biting side tip portion and the length of the excessive thickness deviation region can be reliably and stably minimized.

  And by using both the thickness control of the leading end portion on the biting side and the thickness control of the tail end portion on the biting side as described above, the thickness deviation at both ends of the rolled material is minimized. I found that it can be suppressed.

That is, the plate thickness control method of the biting side tail end of the rolling material in the hot rolling mill of the basic aspect (first aspect) of the present invention is as follows.
While detecting the roll gap opening during the finish rolling pass,
Detecting that the position of the tail end on the rear side of the rolling material in the finish rolling pass is close to the roll bite by a predetermined distance with respect to the rolling direction,
The time difference of the change in the roll gap opening after the tail end is detected, and the rate of change in the roll gap opening is obtained.
A hydraulic cylinder operation control command signal is sent to the servo system that drives the hydraulic cylinder that supports the roll so that the position of the roll can be adjusted (the roll gap can be adjusted) so as to cancel the rate of change of the roll gap. It is characterized by giving.

Moreover, the plate thickness control method of the biting side tail end portion of the rolling material in the hot rolling mill of the second aspect of the present invention is the plate thickness control method of the first aspect,
When detecting that the position of the tail end on the rear side of the rolling material in the finish rolling pass is close to a predetermined distance from the roll bite in the rolling direction, the tail end detection position is set in the rolling direction according to the rolling speed. It is characterized by adjusting to.

  Further, in the following third to sixth aspects, the biting side described in the sheet thickness control method of the biting side tail end of the rolling material in the hot rolling mill according to any of the first and second aspects described above In addition to controlling the thickness of the tail end, a method of controlling the thickness of the biting side tip is also defined, that is, a method of controlling the thickness of both ends of the rolled material.

That is, the thickness control method of the both ends of the rolling material in the hot rolling mill of the third aspect is the same as that of the tail end on the biting side of the rolling material in the hot rolling mill of the first or second aspect. Thickness control at the tail end of the biting side is performed by the plate thickness control method,
Moreover, as the plate thickness control of the biting side tip,
For the roll on the side supported by the hydraulic cylinder so that the position can be adjusted, the position of the hydraulic cylinder is detected when the material to be rolled is caught in the roll bite of the rolling mill,
The position detection value of the hydraulic cylinder is obtained by time differentiation of the position detection value of the hydraulic cylinder,
Controlling the operation of the hydraulic cylinder so as to cancel the position change speed;
It is characterized by.

Moreover, the thickness control method of the both ends of the rolling material in the hot rolling mill of the fourth aspect of the present invention is the thickness control method of both ends of the third aspect,
As the plate thickness control of the biting side tip,
In controlling the operation of the hydraulic cylinder so as to cancel the position change speed, a hydraulic cylinder operation control command signal obtained from the obtained position change speed is provided to a servo system of the hydraulic cylinder. To do.

Furthermore, the thickness control method of both ends of the rolling material in the hot rolling mill of the fifth aspect of the present invention is the thickness control method of both ends of the third or fourth aspect,
As the plate thickness control of the biting side tip,
In determining the position change speed of the hydraulic cylinder, at least within the period until the absolute value of the position change speed is maximized, the position change speed is determined,
The operation of the hydraulic cylinder is controlled so as to cancel the position change speed at least during the period.

Furthermore, the thickness control method of both ends of the rolling material in the hot rolling mill of the sixth aspect of the present invention is the thickness control method of both ends of the fifth aspect,
As the plate thickness control of the biting side tip,
When the absolute value of the position change speed of the hydraulic cylinder becomes maximum, the operation of the hydraulic cylinder is controlled so as to cancel the position change speed.

  According to the thickness control method for the biting side tail end of the rolling material in the hot rolling mill of the present invention, in hot finish rolling a steel sheet having a large deformation resistance at a hot rolling temperature represented by stainless steel. The occurrence of the thickness deviation at the biting side tail end can be reliably and stably suppressed. In addition, according to the method for controlling the thickness of both ends of the rolling material in the hot rolling mill of the present invention, it is possible to reliably generate not only the tail end on the biting side but also the tip thickness on the biting side. And it can suppress stably. Therefore, according to the thickness control method of each invention, the length of the excessively thick portion at the end in the length direction of the rolled-up plate is reduced to improve the product yield, and the quality of the plate is less variable. It is possible to manufacture hot-rolled sheet products reliably and stably, and even when rolling materials with various steel grades and various sheet thicknesses with different deformation resistance, occurrence of sheet thickness deviations at each end. Can be reliably and stably suppressed, and a hot-rolled sheet product of good quality with a small length of the excessively thick part at the end in the lengthwise direction and with little variation in the thickness can be reliably obtained.

It is a schematic diagram which shows typically the outline | summary of an example of the control system in the case of controlling plate | board thickness by the conventional AGC-APC control system with the outline | summary of a hot finish rolling mill. It is explanatory drawing which shows typically an example of plate | board thickness distribution in the length direction in the stainless steel plate obtained by the conventional hot finish rolling. It is explanatory drawing which shows notionally an example of plate | board thickness distribution in the length direction in a certain 1 pass in the conventional hot finish rolling. When the plate thickness is controlled by the conventional general AGC-APC control method, the sinking state of the hydraulic cylinder at the tail end of the biting side, the fluctuation state of the roll gap opening, and the plate thickness fluctuation state are conceptually shown. It is explanatory drawing shown. Explanatory drawing which shows notionally the subsidence situation of the hydraulic cylinder in the biting side tail end part, fluctuation state of the roll gap opening degree, and fluctuation state of the plate thickness in the plate thickness control method of the first embodiment of the present invention. It is. FIG. 6 is an explanatory diagram in which FIG. 4 and FIG. 5 are overlapped with the same time axis scale. It is an approximate solution figure showing an outline of an example of a system configuration for carrying out a board thickness control method of a 1st embodiment. It is explanatory drawing which shows notionally the subsidence state of a hydraulic cylinder in the front-end | tip part at the biting side, and a plate | board thickness fluctuation | variation state at the time of plate | board thickness control by the conventional general AGC-APC control system. As the plate thickness control method of the second embodiment of the present invention, when the control of the biting side tail end and the control of the biting side tip are used together, the hydraulic cylinder sinks at the biting side tip. It is explanatory drawing which shows a condition and a board thickness fluctuation | variation condition notionally. It is explanatory drawing which overlapped FIG. 8 and FIG. 9 on the same time scale. It is a schematic diagram which shows the outline | summary of an example of the system configuration for implementing the plate | board thickness control method of 2nd Embodiment. An explanatory diagram conceptually showing the subsidence of the hydraulic cylinder at the tip of the biting side and the plate thickness fluctuation state in the hydraulic cylinder subsidence compensation method (getter wearing method) as the plate thickness control of the biting side tip It is. In the plate thickness control method of the third embodiment, in which the hydraulic cylinder sinking compensation method is used together as the plate thickness control of the biting side tip, the sinking state and plate thickness fluctuation of the hydraulic cylinder at the biting side tip It is explanatory drawing which shows a condition notionally corresponding to FIG.

Next, each embodiment of the present invention will be described in detail.
[First embodiment]
This 1st embodiment is an embodiment corresponding to the board thickness control method of the biting side tail end part of the above-mentioned 1st and 2nd mode. Here, as a premise of the plate thickness control method according to the first embodiment of the present invention, the subsidence of the hydraulic cylinder at the biting side tail end in the case of the conventional non-control and the accompanying fluctuation of the roll gap opening degree FIG. 4 schematically shows the situation and the plate thickness fluctuation state, and the subsidence of the hydraulic cylinder at the biting side tail end by the plate thickness control method according to the first embodiment of the present invention compared with that. FIG. 5 schematically shows the fluctuation state of the roll gap opening and the thickness fluctuation situation associated therewith, and FIG. 6 shows FIGS. 4 and 5 superimposed on each other. FIG. 7 shows an example of a system configuration for carrying out the first embodiment.

FIG. 4 shows a conventional submerged state of the hydraulic cylinder at the biting side tail end in the case of no control, a fluctuation state of the roll gap opening, and a fluctuation state of the plate thickness.
As shown in FIG. 4, if the region where the deformation resistance due to supercooling near the biting side tail end portion of the material to be rolled reaches the roll bite at the timing T1, the subtraction of the hydraulic roll is started from the timing T1, Normally, the amount of subsidence gradually increases, and accordingly, the roll gap opening increases and the thickness deviation also increases. That is, the thickness of the tail end on the biting side becomes larger than the target thickness, and the thickness deviation may exceed the allowable tolerance.

Here, if the behavior of the change in the roll gap opening accompanying the subsidence of the hydraulic cylinder immediately after the timing T1 when the region having a large deformation resistance reaches the roll bite, particularly the process shown in FIG. The speed of change of the gap opening (and hence the time differential value of the fluctuation amount of the roll gap opening) remains substantially zero until the timing T1, increases rapidly from the moment of the timing T1, and then the roll gap opening. If the fluctuation speed exceeds the maximum (timing T2), the fluctuation speed of the roll gap opening degree suddenly decreases and returns to zero or a value close thereto.
The timing T2 at which the absolute value of the opening fluctuation speed in the roll gap opening fluctuation pattern at the biting side tail end is maximized is the timing T1 when the region where the deformation resistance is large reaches the roll bite. It turns out that it is very close.

Therefore, in the thickness control method of the biting side tail end according to the present invention, the roll gap opening degree is controlled in order to suppress the increase in the plate thickness deviation at an early stage before the plate thickness deviation of the biting side tail end increases. The hydraulic cylinder operation is controlled based on the obtained differential value, i.e., the roll gap opening fluctuation speed value (specifically, the fluctuation speed is canceled and the fluctuation speed is set to zero). Dodging control).
It should be noted that the pattern of fluctuation of the roll gap opening at the tail end on the biting side as described above, particularly the pattern in the vicinity of the timing T1 when the region having a large deformation resistance reaches the roll bite, has different steel types and plate thicknesses with different deformation resistance. Since different materials to be rolled are basically the same, they can be applied regardless of the steel type and thickness.

FIG. 5 shows the subsidence of the hydraulic cylinder at the tail end on the biting side and the fluctuation of the roll gap opening associated therewith in the plate thickness control according to the first embodiment of the present invention based on the pattern as described above. The situation and the thickness fluctuation situation are shown.
In the case of the first embodiment, after detecting that the region on the tail end side where the deformation resistance is large has reached a position close to the roll bite (timing T0), the fluctuation speed (differential value) of the roll gap opening is set. In response, the operation of the hydraulic cylinder is controlled in a direction to cancel the fluctuation speed. That is, in this embodiment, the position change speed in the sinking direction (downward direction) of the hydraulic cylinder becomes zero so that the speed of the roll gap opening fluctuation in the direction in which the roll gap opening increases becomes zero. As described later, a control command signal for controlling the hydraulic cylinder is applied to the servo system of the hydraulic cylinder. When the subsidence speed of the hydraulic cylinder actually decreases, and when the subsidence speed becomes zero and the fluctuation speed of the roll gap opening becomes zero (timing T3), the subsidence operation of the hydraulic cylinder is stopped. At this time (T3), the cylinder sinking amount (absolute value) is maximized, and as a result, the roll gap opening is maximized. The maximum sinking amount of the hydraulic cylinder at this time is represented by ΔGa.
When the roll gap opening becomes maximum, that is, after the time (T3) when the cylinder sinking amount reaches the maximum ΔGa, the hydraulic cylinder is raised by the same APC control function as before, and finally the roll gap is reached. Returns to the opening at or near that of steady rolling.

  Here, for the above control, it is detected (timing T0) that the region on the tail end side where the deformation resistance is large has reached a position close to the roll bite, in other words, the tail end in the rolling pass. It is necessary to detect that the position is close to the roll bite to some extent, and to start operation control of the hydraulic cylinder based on the differential value of the change amount of the roll gap opening from the detection time (T0). That is, if there is a slight variation in the plate thickness during steady rolling, the differential value of the change amount of the roll gap opening appears as a large value even with the slight variation in the plate thickness. Therefore, if the control by the differential value as described above is started at a considerably earlier stage than the area where the deformation resistance is large reaches the roll bite, hunting occurs due to the influence of slight plate thickness fluctuation during steady rolling, On the contrary, the plate thickness deviation becomes large, or the plate thickness deviation quality deteriorates even if the plate thickness deviation is within the allowable tolerance. In order to avoid such an adverse effect as much as possible, it is desirable to start the above control from the timing T0 as close as possible to the timing T1 at which the region having a large deformation resistance reaches the roll bite. For that purpose, according to the rolling speed, the length of the region where the deformation resistance increases due to overcooling on the tail end side is predicted from the past results, etc., and the length from the tail end is slightly smaller than the above predicted length. It is desirable to start the control with the above-described differential value from the time when the long part reaches the roll bite.

If the conventional uncontrolled pattern shown in FIG. 4 and the pattern according to the first embodiment shown in FIG. 5 are overlapped with the same time scale, the result is shown in FIG. .
As is apparent from FIG. 6, in the method according to the first embodiment of the present invention, the subsidence of the hydraulic cylinder at the timing T3 at which the roll gap opening becomes the maximum and the subsidence amount of the hydraulic cylinder reaches the maximum value ΔGa. The amount (ΔGa) is much smaller than the maximum subsidence amount (ΔGb) when the method of the present invention is not applied. That is, the maximum deviation of the plate thickness deviation at the time of biting is reduced. In the case of the present invention, this is because the control is not performed by the variation amount of the roll gap opening, but by the change rate (differential value) of the variation of the roll gap opening.

  The system for carrying out such a plate thickness control method of the first embodiment is based on the AGC-APC control system and differentiates the detected value of the roll gap opening (opening fluctuation amount) to open the roll gap. Control command to control the operation of the hydraulic cylinder to cancel the roll gap opening fluctuation speed to the control part (usually APC control part) of the hydraulic servo system in response to the differential value A function of giving the signal SD and a structure incorporating a tail end position detector for detecting that the position of the tail end on the biting side is close to the roll bite may be incorporated, and the rest is not particularly limited. FIG. 7 shows a system configuration in which these functions and the tail end position detector are incorporated in the conventional representative AGC-APC control system shown in FIG. 7, the same elements as those shown in FIG. 1 are denoted by the same reference numerals as those in FIG.

In FIG. 7, the position of the tail end portion in the finish rolling pass is detected, and when the position approaches a predetermined distance to the roll bite, the control based on the differential value of the roll gap opening fluctuation amount at the tail end portion is started. . For example, as shown in FIG. 7, a tail end position detector 70 is disposed at a position separated from the roll bite by a predetermined distance on the entry side (biting side) of the roll bite. From timing T0 (see FIG. 5) when the tail end is detected by 70, the plate thickness estimated deviation Δh obtained from the fourth computing unit 36 is led to the seventh computing unit 71 which is a differentiator. Here, the plate thickness estimation deviation Δh corresponds to the fluctuation of the roll gap opening, so that the seventh calculator 71 as a differentiator is given the fluctuation amount of the roll gap opening. . Then, the seventh calculator 71 calculates a differential value of the roll gap opening fluctuation amount, and the obtained differential value is introduced into the control command signal generator 72, and a control command signal ( A control command signal SD for canceling the roll gap opening variation speed is provided to the APC controller 41, and the servo valve 15 is controlled by the servo operation signal SB from the APC controller 41.
That is, the operation of the hydraulic cylinder 13 is controlled by the operation of the servo valve 15 based on the control command signal SD, and the sinking speed thereof is slowed down. Therefore, the fluctuation speed of the roll gap opening is reduced. Thereafter, the rise of the hydraulic cylinder is stopped, and the fluctuation of the roll gap opening is stopped (timing T3 in FIG. 5). After this timing T3, the descent of the hydraulic cylinder is started by APC control, and the roll gap is returned to the opening at the time of steady rolling or an opening close thereto.
Therefore, according to the first embodiment, an increase in the plate thickness deviation of the tail end portion is suppressed, and at the same time, the length of the tail end side region exceeding the allowable tolerance is shortened, and the yield is improved.

The specific configuration of the tail end position detector 70 is not particularly limited. For example, an HMD (Hot Metal Detector) or a laser position detector may be used.
Here, the timing at which the control based on the fluctuation speed of the roll gap opening by the tail end position detection is desirably changed according to the rolling speed, so that the tail end position detector 70 also sets the detection position of the tail end in the rolling direction. It is desirable to provide it so that it can adjust along.

  Here, in the above embodiment, the control command signal SD for the biting side tail end is the position of the APC controller 41 for directly controlling the servo valve 15, in other words, the control part for the servo valve control. Since it is directly applied to the servo system at the end, the response time to the control command signal SD is extremely short. That is, in the conventional general AGC-APC control, the control of the position of the hydraulic cylinder accompanying the change in the roll gap opening degree is performed through the entire AGC control unit 30, so that the responsiveness is poor and the speed is high. Although it has been difficult to reliably control the thickness of the biting side tail end portion of the material to be rolled, responsiveness is provided by directly giving a control command signal SD to the servo system (APC controller 38). It became possible to improve. And as mentioned above, coupled with capturing and controlling the fluctuation speed of the roll gap opening that changes from the moment when the deformation resistance (supercooling area) on the tail end side reaches the roll bite, In addition, it is possible to reliably suppress an increase in the plate thickness deviation at the biting side tail end by controlling the hydraulic cylinder much earlier.

[Second Embodiment]
In the first embodiment described above, only the control of the biting side tail end portion has been described. However, the control of the biting side tip end portion is not performed independently of the control of the biting side tail end portion (first embodiment). In combination, it is possible to further reliably reduce the thickness deviation of both end portions in the rolling method in which reverse rolling is alternately bitten in the reverse direction. Therefore, this combination method will be described as a second embodiment with reference to FIGS. The plate thickness control for the biting side tail end may be the same as in the first embodiment, and therefore only the plate thickness control for the biting side tip is described here.

  As a premise of the plate thickness control method of the second embodiment, FIG. 8 schematically shows a sinking state and a plate thickness fluctuation state of the hydraulic cylinder at the front end of the biting side in the case of conventional non-control, In comparison, FIG. 9 schematically shows the hydraulic cylinder sinking state and the plate thickness fluctuation state at the biting side tip by the plate thickness control method of the second embodiment of the present invention, and FIG. Shows a state in which FIGS. 8 and 9 are overlapped. FIG. 11 shows an example of a system configuration for implementing the second embodiment.

FIG. 8 shows the state of subsidence of the hydraulic cylinder and the state of fluctuation of the plate thickness at the front end of the bite side in the conventional case of no control (however, general AGC-APC control is performed). ing.
As shown in FIG. 8, at the moment of biting (N1), the hydraulic cylinder is sunk by the impact load (the oil column is sunk). During the subduction period (N2), the thickness deviation increases. That is, the plate thickness becomes larger than the target plate thickness. Let ΔGn be the maximum value of the oil column subsidence when the plate thickness deviation becomes maximum (N3: indicated as valley point). Then, from the valley point N3, the hydraulic cylinder rises so as to return (converge) the cylinder position to the target position by APC control by APC control (N4), and the plate thickness deviation decreases accordingly, and finally the target plate thickness To reach.

  If the behavior (position change) of the hydraulic cylinder sinking from the moment of biting (N1) to the valley point (N3) is observed in detail, the speed of the sinking will be described. (Therefore, the time derivative of the position) suddenly increases from the moment of biting, and if the sinking speed (position changing speed) exceeds the maximum, the sinking speed (position changing speed) gradually decreases, and then the valley point (N3) is reached, and therefore the time point when the absolute value of the position change speed in the subtraction pattern becomes maximum is greater than the time point when the subtraction amount reaches the maximum value (valley point N3). Recognized that it was early. Therefore, in the present invention, in order to suppress the plate thickness deviation at the biting side tip portion at an early stage, the change in the subsidence (position change) of the hydraulic cylinder is differentiated, and the operation of the hydraulic cylinder is performed according to the obtained change speed value. Trying to control. In addition, the pattern of the change rate of the amount of subduction at the beginning of biting as described above is basically common to steel materials with different deformation resistances and rolled materials with different plate thicknesses, so regardless of the steel type and plate thickness, Applicable.

  FIG. 9 shows a subsidence state and a plate thickness fluctuation state of the hydraulic cylinder at the biting side tip in the plate thickness control according to the second embodiment of the present invention based on the pattern as described above. In this case, on the premise of the conventional general AGC-APC control method, a control method peculiar to the present invention at the time of biting is added (introduced).

  Also in the case of this second embodiment, at the moment of biting (C1), the hydraulic cylinder sinks (sink of the oil column) due to the impact load, and this sinking increases rapidly with time. Become. The sinking speed (position change speed) increases rapidly from the moment of biting (C1 to C2). Here, the position of the hydraulic cylinder is detected by a position detector attached to the hydraulic cylinder, the amount of change is differentiated with time, and the change speed (sinking speed) is obtained (C3). Then, at the time point Cp when the change speed reaches the maximum value, a command signal for controlling the operation of the hydraulic cylinder is given to the servo system of the hydraulic cylinder so as to cancel the change speed of the hydraulic cylinder (C3 to C4). That is, in this embodiment, the hydraulic cylinder is controlled so that the position change speed in the sinking direction (downward direction) of the hydraulic cylinder becomes zero. Note that the timing of the time point Cp at which the change rate becomes the maximum value can be detected when the differential value of the change rate becomes zero.

  As described above, at Cp, a command signal for controlling the operation of the hydraulic cylinder is given to the servo system of the hydraulic cylinder so that the differential value of the changing speed becomes zero and the absolute value of the changing speed of the hydraulic cylinder is canceled. After that, if the subsidence speed of the hydraulic cylinder actually decreases and the subsidence speed becomes zero (C4), the subsidence operation is stopped (C5). At this time (C5), the cylinder sinking amount (absolute value) becomes maximum. The maximum sinking amount at this time is set to ΔGc.

  After the time point (C5) when the cylinder sinking amount reaches the maximum ΔGc, the hydraulic cylinder is raised (C6 to C7) by the APC control function similar to the conventional one, and the roll gap finally reaches the target opening degree. (C8).

  In addition, when the roll gap approaches the target opening to some extent during the period of C6 to C7, it is preferable to give a command to increase the rolling speed from the low speed state at the start of biting toward the steady rolling speed.

  Further, at the timing of Cp, a command signal for controlling the operation of the hydraulic cylinder is once given to the servo system of the hydraulic cylinder so that the differential value of the changing speed becomes zero and the absolute value of the changing speed of the hydraulic cylinder is canceled. After being given, the hydraulic cylinder can be raised by the function of the command signal and the APC control of the cylinder without actively performing the control based on the differential value of the changing speed. In other words, after the differential value of the change speed becomes zero, it is not necessary to perform control with the differential value, and thereafter, the calculation of the differential value and the control are not necessary for the calculated value.

The pattern on the biting side in the conventional control method on the biting side shown in FIG. 8 above and the pattern on the biting side according to the second embodiment shown in FIG. If superimposed as the same scale, it is represented as shown in FIG.
As is apparent from FIG. 10, in the method of the second embodiment of the present invention, the timing Cp at which the amount of subsidence of the hydraulic cylinder at the tip end portion on the biting side becomes the maximum value ΔGc is determined when the method of the present invention is not applied. The timing is much earlier than the timing Cn at which the sinking amount reaches the maximum value ΔGn. Therefore, the maximum value ΔGc of the subduction amount in the method of the second embodiment of the present invention itself is also smaller than the maximum value ΔGn of the subduction amount when the method of the present invention is not applied, and as a result, the plate at the time of biting The thickness deviation (maximum deviation) is also reduced. This is because it is not controlled by the amount of change in the subsidence of the hydraulic cylinder, but is controlled by the speed of change in subsidence that immediately appears from the moment of start of biting (the differential value of the amount of change).
Furthermore, as described above, the maximum value ΔGc of the sinking amount is reduced and the maximum thickness deviation amount on the biting side is reduced, so that the length of the region where the thickness deviation exceeds the education tolerance is also reduced. is there.

  The system for carrying out the plate thickness control method of the second embodiment is based on the AGC-APC control system, and the control of the first embodiment as described above (control of the biting side tail end portion). ) Function to obtain the cylinder position change speed by differentiating the detection value (position fluctuation amount) of the hydraulic cylinder position detector on the biting side, and respond to the differential value (cylinder position change speed) Then, the control part (usually the APC control part) of the hydraulic servo system may be configured to have a function of giving a command signal SC that cancels the subsidence change speed. FIG. 11 shows the configuration of a system in which the function for controlling the biting side tip portion is incorporated into the system for controlling the thickness of the biting side tail end shown in FIG. In FIG. 11, the same elements as those shown in FIG. 1 or FIG. 7 are denoted by the same reference numerals as those in FIG. 1 and FIG.

In FIG. 11, the position detector 16 detects the position of the hydraulic cylinder 13. Since the position of the hydraulic cylinder 13 corresponds to the vertical position of the lower work roll 11B, the detection signal output from the position detector 16 corresponds to the roll position detection signal. Then, this roll position detection signal is guided to the sixth arithmetic unit 61 which is a differentiator, and the differential value is introduced into the command signal generator 62, and the command signal corresponding to the differential value (sinking at the time of biting) A command signal SC for canceling the change speed of the servo valve 15 is supplied to the APC controller 41, and the servo valve 15 is controlled by the APC controller 41.
Here, the change amount Δs of the roll gap opening s is differentiated, not the change rate itself of the subsidence amount of the hydraulic cylinder obtained from the position detector 16, but the change Δs of the roll gap opening s is differentiated. The change speed (differential value) corresponds to the change speed of the subsidence amount of the hydraulic cylinder. Therefore, the control method of the second embodiment can be implemented by such a system.

  Here, also in the second embodiment, the command signal SC for controlling the plate thickness at the biting side tip is the position of the APC controller 41 for directly controlling the servo valve 15, in other words, for servo valve control. Therefore, the response time to the command signal SC is very short. That is, in the conventional general AGC-APC control, the control of the position of the hydraulic cylinder is performed through the entire AGC control unit 30, so that the response is poor and the biting of the material to be rolled that is rolled at a high speed is performed. Although it has been difficult to reliably control the thickness at the front end portion of the insertion side, it is possible to improve the responsiveness by giving a command signal directly to the servo system (APC controller 38). And as described above, coupled with capturing and controlling the change rate of the amount of subsidence that changes from the moment of biting, the hydraulic cylinder is controlled much earlier than before, and the biting side tip portion It has become possible to reliably suppress an increase in the plate thickness deviation.

[Third Embodiment]
Further, when the thickness control of the tail end on the biting side and the thickness control of the tip on the biting side are used in combination, the above-mentioned subtraction compensation method for biting on the biting side tip partial plate thickness control Can be used together with (getter wearing system). An embodiment in this case will be described as a third embodiment with reference to FIGS. 12 and 13. Note that FIG. 12 does not apply the plate thickness control at the time of biting described in the second embodiment, and is a bite when the conventional general gettering method is implemented on the premise of AGC-APC control. FIG. 13 shows the submerged state of the hydraulic cylinder and the plate thickness fluctuation state at the tip of the insertion side, and FIG. 13 shows the plate thickness at the time of biting according to the present invention on the premise of AGC-APC control as the third embodiment. The submerged state of the hydraulic cylinder and the plate thickness fluctuation state at the biting side tip when the control method and the getter wearing method are used together are shown. However, although the thickness control of the tail end portion of the biting side is the same as that of the first embodiment, the gettering method cannot be applied to the control of the tip portion on the biting side, so This is the same as the first and second embodiments, and a description thereof is omitted.

  In order to compensate for the momentary opening of the roll gap at the time of biting, the conventional general gettering method is such that the APC control is turned off at the start of biting and the hydraulic cylinder at the start of biting The position of is raised by a predetermined height than during steady rolling (thus setting the roll opening smaller than during steady rolling), thereby compensating for the sinking of the lower roll during biting, This is a technique for preventing an excessive increase in the thickness of the tip due to subduction. That is, even if the hydraulic cylinder sinks due to impact load when biting, the roll gap becomes excessively large when the impact load is applied by increasing the position of the hydraulic cylinder in advance (by putting the getter on). It is to prevent it from becoming. In this case, the height and period of wearing the getter are predicted in advance from past results, and the predicted values are set in the control unit. When the getter wearing period elapses, the APC control is performed. It is made to function, and the position of the hydraulic cylinder is positioned at a position where a roll gap during steady rolling can be obtained.

  In the conventional general gettering method as described above, as described above, if the gettering amount (sinking compensation amount) is increased, the opening of the roll gap is reduced accordingly. As a result, the impact load at the time of biting becomes large, and as shown in FIG. 12, the hydraulic cylinder suddenly moves up and down at the initial stage after biting, resulting in a jumping-up thickness deviation. Often occurs. However, if the control method of the third embodiment, which combines the method described in the second embodiment and the gettering method, is used as the plate thickness control of the biting side tip portion, the gettering amount (sinking) Even if the compensation amount) is reduced, it is possible to more reliably suppress the occurrence of a plate thickness deviation due to the jumping in the conventional gettering system as described above at the biting side tip portion. In other words, by combining the control by the hydraulic cylinder sinking speed (differential value) with the gettering method, the need to excessively increase the roll gap opening when biting with the gettering method is reduced, and gettering is performed. It is possible to reduce the thickness deviation at the biting side tip while minimizing the disadvantages of the method.

The steel type to which the present invention is applied is not basically limited, but is particularly effective when applied to a steel type having a large deformation resistance at a hot rolling temperature, such as stainless steel, heat resistant steel, superalloy, and the like. It is. As the stainless steel, ferritic stainless steel, martensitic stainless steel, austenitic stainless steel, duplex stainless steel, precipitation effect type stainless steel, and any other steel types can be applied.
In addition, the target plate thickness after the hot finish rolling is not particularly limited, but in the case of stainless steel, it is generally about 4 mm to 100 mm.
Furthermore, the average rolling reduction per pass, the average rolling load, and the rolling speed are not particularly limited and may be the same as those in normal hot finish rolling. In the case of stainless steel, the rolling reduction in one pass is generally used. Is about 10% to 25%, the rolling load is about 1000 to 6500 tons, and the rolling speed is about 0.5 m / sec to 5.0 m / sec.

  Examples of the present invention will be described below together with comparative examples. The following examples are for clarifying the operation and effect of the present invention, and it is needless to say that the conditions described in each example do not limit the technical scope of the present invention.

[Example 1]
About the SUS316 steel which is an austenitic stainless steel, the raw plate after hot rough rolling was subjected to finish rolling in 10 passes with a reverse rolling mill. The dimensions of the original plate were a length of 3000 m, a width of 1500 mm, a plate thickness of 150 mm, the target plate thickness of the final pass rise was set to 12 mm, and the plate thickness tolerance that should be recognized as a non-defective product was set to ± 1.5 mm. The temperature of the original sheet immediately before finish rolling is 1000 ° C. on average. The average rolling speed in each pass is 2.0 mm / sec, the average rolling reduction is 20%, and the average rolling load (set rolling load for setting the target plate thickness) is 3500 ton.
Under the above-described conditions, hot finish rolling was performed while applying the thickness control method for the biting side tail end described as the first embodiment.
The tail end position detector detects the tail end when the tail end approaches a roll bit up to a distance of 3000 mm, and starts tail end plate thickness control.

  About the plate obtained through the final pass of finish rolling in Example 1, the plate thickness distribution in the length direction along the plate width center line was calculated by simulation, and the average plate thickness of the total length in the length direction was At 12 mm, it was confirmed that the maximum thickness deviation in the portion on the tail end side in the length direction (the portion corresponding to the biting side in the final finish rolling pass) was 0.12 mm. Furthermore, it was confirmed that the length of the region exceeding the allowable tolerance was 0 mm. In addition, the average plate thickness in the length direction of the portion excluding the region of the crop defective portion (the central portion in the length direction; the portion which is regarded as a product without being cut off) is 12 mm, and the thickness deviation of the portion is the above It was confirmed that it was within a range of +0.05 mm and −0 mm at the maximum with respect to the average thickness of the central portion in the length direction.

[Example 2]
As described in the second embodiment above, the plate thickness control is applied to the leading end portion of each pass on the raw plate that has been subjected to hot rough rolling similar to that used in Example 1, and each pass The tail end on the biting side was also controlled to perform hot finish rolling. The control conditions for the tail end on the biting side of each path are the same as those described in the first embodiment.

  With respect to the plate obtained through the final rolling in Example 2 above, the plate thickness distribution in the length direction along the plate width center line was calculated by simulation, and the average plate thickness of the total length in the length direction was 12 mm, the maximum thickness at the tip end portion in the length direction (the portion corresponding to the biting side in the final finish rolling pass) is 0.68 mm, and the tail end portion in the length direction (the biting in the final finish rolling pass) It was confirmed that the maximum thickness in the portion corresponding to the delivery side was 0.1 mm. Further, it was confirmed that the length of the region exceeding the allowable tolerance in the tip side portion was 0 mm, and the length of the region exceeding the allowable tolerance was 0 mm in the tail side portion. In addition, the average plate thickness in the length direction of the portion excluding the region of the crop defective portion (the central portion in the length direction; the portion which is regarded as a product without being cut off) is 12 mm, and the thickness deviation of the portion is the above It was confirmed that it was within the range of +0.04 mm and −0 mm at the maximum with respect to the average thickness of the central portion in the length direction.

[Comparative Example 1]
For the same hot rough rolled finished sheet as used in Example 1, the thickness control of the present invention is not applied to the tail end on the biting side of each pass, and the tip on the biting side of each pass is applied. Also, the hot finish rolling was performed by applying the conventional general AGC control-APC control method shown in FIG. The conditions described in Example 1 were applied except that the plate thickness control method of the present invention was not applied.

  With respect to the plate obtained through the final rolling in the comparative example 1, the plate thickness distribution in the length direction along the plate width center line was calculated by simulation. The average plate thickness of the total length in the length direction is The maximum thickness at the tip side portion in the length direction (the portion corresponding to the biting side in the final finish rolling pass) is 0.86 mm, and the tail end side portion in the length direction (the biting in the final finish rolling pass) It was confirmed that the maximum thickness in the portion corresponding to the delivery side was 0.26 mm. Further, it was confirmed that the length of the region exceeding the allowable tolerance in the tip side portion was 0 mm, and the length of the region exceeding the allowable tolerance was 0 mm in the tail side portion. In addition, the average plate thickness in the length direction of the portion excluding the region of the crop defective portion (the central portion in the length direction; the portion which is regarded as a product without being cut off) is 12 mm, and the thickness deviation of the portion is the above It was confirmed that it was within the range of +0.18 mm and −0 mm at the maximum with respect to the average plate thickness in the central portion in the length direction.

  As is clear from the comparison between the results of Examples 1 and 2 and the results of Comparative Example 1, in the case of Examples 1 and 2, the comparison in which the plate thickness control method of the present invention was not applied. Compared to Example 1, the thickness deviation at both end portions in the length direction of the hot finish rolled sheet was significantly reduced. Further, in the case of Example 1 and Example 2, the thickness deviation of the central portion region that does not exceed the thickness tolerance is also smaller than in the case of Comparative Example 1, and thus the product thickness quality may be good. it is obvious.

Example 3
About the SUS410 steel which is martensitic stainless steel, the hot rolled plate was subjected to finish rolling in 12 passes with a reverse rolling mill. The dimensions of the original plate were 3200 mm in length, 1250 mm in width, and 250 mm in thickness, the target plate thickness after final pass was 16 mm, and the plate thickness tolerance that should be recognized as a non-defective product was set to ± 1.9 mm. The temperature of the original sheet immediately before finish rolling is 900 ° C. on average. The average rolling speed in each pass is 2.0 m / sec, the average rolling reduction is 22%, and the average rolling load (set rolling load for setting the target plate thickness) is 2250 ton. In the third embodiment, as in the first embodiment, the above-described plate thickness control is not applied to the leading end portion on the biting side of each path, and only the tail end portion on the biting side of each path is used. Hot finish rolling was performed by applying the sheet thickness control method of the invention. The position of the tail end position detector was the same as in Example 1.

  For the plate obtained through the final rolling in Example 3 above, the plate thickness distribution in the length direction along the plate width center line was calculated by simulation, and the average plate thickness of the total length in the length direction was The maximum thickness at the tip end portion in the length direction (the portion corresponding to the biting side in the final finish rolling pass) is 16 mm, and the tail end portion in the length direction (the biting in the final finish rolling pass) It was confirmed that the maximum thickness in the portion corresponding to the delivery side was 0.10 mm. Further, it was confirmed that the length of the region exceeding the allowable tolerance in the tip side portion was 0 mm, and the length of the region exceeding the allowable tolerance in the tail side portion was 0 mm. Further, the average plate thickness in the length direction of the portion excluding the crop defective portion (the central portion in the length direction; the portion which is regarded as a product without being cut off) is 16 mm, and the thickness deviation of the portion is the length described above. It was confirmed that it was within the range of +0.03 mm and −0 mm at the maximum with respect to the average plate thickness in the central portion in the direction.

[Comparative Example 2]
With respect to the raw sheet after hot rough rolling similar to that used in Example 3, the conventional AGC control-APC control method shown in FIG. 1 is applied without applying the sheet thickness control method of the present invention. Intermediate finish rolling was performed. The conditions described in Example 3 were applied except that the plate thickness control method of the present invention was not applied.

  About the plate obtained through the final pass of finish rolling in Comparative Example 2 above, the plate thickness distribution in the length direction along the plate width center line was calculated by simulation. The average plate thickness of the total length in the length direction was The maximum thickness at the tip end portion in the length direction (the portion corresponding to the biting side in the final finish rolling pass) is 0.77 mm, and the tail end portion in the length direction (the biting in the final finish rolling pass) It was confirmed that the maximum thickness in the portion corresponding to the delivery side was 0.21 mm. Further, it was confirmed that the length of the region exceeding the allowable tolerance was 0 mm in the tip side portion, and the length of the region exceeding the allowable tolerance was 0 mm in the tail side portion. Furthermore, the average plate thickness in the length direction of the portion excluding the portion other than the crop defective portion (the central portion in the length direction; the portion that is regarded as a product without being cut off) is 16 mm, and the plate thickness deviation of the portion is It was confirmed that it was within the range of +0.16 mm and −0 mm at the maximum with respect to the average plate thickness at the central portion in the length direction.

Even in the case where the steel type is martensitic stainless steel different from Example 1 and Example 2 (Example 3), as is clear by comparing the results of Example 3 and Comparative Example 2 above, Compared with Comparative Example 2 in which the plate thickness control method of the present invention was not applied, the plate thickness deviation at both end portions in the length direction of the hot finish rolled plate was reduced. In addition, it is clear that the thickness deviation of the central portion area excluding the defective crop portion is also smaller than that in the case of Comparative Example 2, and thus the thickness quality of the product is also good.
In addition, in the case of steels other than the steel types shown in the above examples, for example, ferritic stainless steel, precipitation hardening, austenite / ferrite duplex stainless steel, it has been confirmed that the same effect as described above can be obtained. Yes.

  The preferred embodiments and examples of the present invention have been described above, but the present invention is not limited to these embodiments and examples. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 Hot finish rolling mill 11A, 11B Work roll 12A, 12B Backup roll 13 Hydraulic cylinder 14 Hydraulic pump 15 Servo valve 16 Position detector 20 Steel plate (rolled material)
30 AGC control unit 40 APC control unit 70 Tail end position detector SB Servo operation signal SC command signal SD command signal

Claims (6)

While detecting the roll gap opening during the finish rolling pass,
Detecting that the position of the tail end on the rear side of the rolling material in the finish rolling pass is close to the roll bite by a predetermined distance with respect to the rolling direction,
The time difference of the change in the roll gap opening after the tail end is detected, and the rate of change in the roll gap opening is obtained.
A hydraulic cylinder operation control command signal is sent to the servo system that drives the hydraulic cylinder that supports the roll so that the position of the roll can be adjusted (the roll gap can be adjusted) so as to cancel the rate of change of the roll gap. A sheet thickness control method for a tail end portion of a biting side of a rolled material in a hot rolling mill. In the sheet thickness control method of the biting side tail end of the rolling material in the hot rolling mill according to claim 1,
In detecting that the position of the tail end on the rear side of the rolling material in the finish rolling pass is close to a predetermined distance to the roll bite in the rolling direction,
A method for controlling the thickness of a tail end portion of a rolled material biting side in a hot rolling mill, wherein the tail end detection position is adjusted in the rolling direction according to the rolling speed. The thickness control of the biting side tail end is performed by the plate thickness control method of the biting side tail end of the rolled material in the hot rolling mill according to any one of claims 1 and 2,
Moreover, as the plate thickness control of the biting side tip,
For the roll on the side supported by the hydraulic cylinder so that the position can be adjusted, the position of the hydraulic cylinder is detected when the material to be rolled is caught in the roll bite of the rolling mill,
The position detection value of the hydraulic cylinder is differentiated with respect to time to determine the position change speed of the hydraulic cylinder,
Controlling the operation of the hydraulic cylinder so as to cancel the position change speed;
A method for controlling the thickness of both end portions of a rolling material in a hot rolling mill. In the thickness control method of the both ends of the rolling material in the hot rolling mill according to claim 3,
As the plate thickness control of the biting side tip,
In controlling the operation of the hydraulic cylinder so as to cancel the position change speed, a hydraulic cylinder operation control command signal obtained from the obtained position change speed is provided to a servo system of the hydraulic cylinder. The thickness control method of the both ends of the rolling material in the hot rolling mill which performs. In the plate thickness control method of both ends of the rolling material in the hot rolling mill according to any one of claims 3 and 4,
As the plate thickness control of the biting side tip,
In determining the position change speed of the hydraulic cylinder, at least within the period until the absolute value of the position change speed is maximized, the position change speed is determined,
A method for controlling the thickness of both ends of a rolling material in a hot rolling mill, wherein the operation of the hydraulic cylinder is controlled so as to cancel the position change speed at least during the period. In the thickness control method of the both ends of the rolling material in the hot rolling mill according to claim 5,
As the plate thickness control of the biting side tip,
When the absolute value of the position change speed of the hydraulic cylinder becomes maximum, the operation of the hydraulic cylinder is controlled so as to cancel the position change speed. Thickness control method.

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