JP2011235325A - Method and device for controlling shape of strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for controlling the shape of a strip, by which control of local extension quantity in a sheet width direction, which is impossible with the conventional actuator such as a bender and work roll shift is made possible and also the defective shape of the strip is suppressed between stands without operating the complicated crown controller of each stand.SOLUTION: The defective shape of the strip in the middle of finish rolling is suppressed by measuring the shape of the strip during passage with a shape meter 2 installed between finish rolling mills 1 of at least one place, which includes a plurality of finish stands F1-F7, determining a place to be heated in the width direction of the strip and a calorific value on the basis of a shape data measured with the shape meter 2 and heating the strip by controlling the positions and the calorific values of at least two transverse type induction heating devices 4 installed on the upstream side of the finish rolling mill 1.

Description

  The present invention relates to a shape control method and a shape control apparatus that suppress shape defects between stands of a hot-rolled steel sheet (strip) that is rolled by a finishing mill composed of a plurality of rolling stands.

  In recent years, the plate thickness accuracy required for strips has become stricter. Up to now, the accuracy of the plate thickness in the longitudinal direction has been improved by introducing a high-speed responsive hydraulic AGC (Automatic Gauge Control). On the other hand, with regard to accuracy in the width direction, the crown has been reduced by bender and work roll shift crown control, and in the recent manufacture of strict plate thickness materials, it is more important to improve the accuracy in the width direction by lowering the latter. Has increased. Here, the crown refers to the difference between the thickness Hc at the center in the width direction of the strip and the thickness He at the end in the width direction, C = Hc−He, and the reduction in crown means that the difference between Hc and He is small. To improve the flatness.

  On the other hand, in finish rolling of hot rolling, in addition to roll deflection and roll flatness caused by temperature change of the strip, roll wear and thermal crown change due to roll thermal expansion cause crown change of each stand, The plate shape changes with the change in the crown ratio (crown / plate thickness = C / Hc).

  As for the plate shape, it goes without saying that the wave shape on the exit side of the final mill of the finishing mill is important because it greatly affects the shape of the final product, but the wave shape of the strip between the intermediate stands upstream of the final stand is important. However, if it gets worse, there will be a case where a threading trouble occurs as will be described later. Therefore, stabilization of the inter-stand plate shape is also an important factor.

  The plate shape is roughly divided into a medium wave shape (FIG. 8A) in which the central portion in the plate width direction extends, an ear wave shape in which both end portions of the plate extend (FIG. 8B), and a local shape in the plate width direction. There is a quarter wave shape (FIG. 8C) which is a large stretch. In the case where the roll cooling water or the like accumulates at the wave bottom, such as a medium wave or a quarter wave, the water is drawn into the roll biting portion of the finishing rolling stand, so that plate perforation occurs due to the water vapor pressure. In addition, if the wave is large in any shape of medium wave, quarter wave, and ear wave, two-plate chewing accompanied by looper hunting or the like occurs. Such troubles in sheet passing in finish rolling cause not only a reduction in operating rate and product yield, but also a great loss such as damage to rolls and equipment.

  Therefore, in order to stably manufacture the low crown material, it is required to establish a control method for controlling and stabilizing the shape between the finishing rolling stands during rolling as flat as possible.

  In Patent Document 1, a plate shape measuring device is installed on the final stand exit side, and the crown control device of the nearest stand including the final stand is simultaneously operated based on the deviation from the target shape, while minimizing the shape change between the stands, A plate shape control method in a continuous hot finish rolling mill for shape adjustment is disclosed.

JP 2006-281231 A

  In the plate shape control method disclosed in the above-mentioned Patent Document 1, the shape measurement value used for shape control feedback is only the final stand exit side, and the controlled object is only the final stand exit side shape. Even if this occurs, there is a problem that shape control is not performed if the deviation from the target shape on the final stand exit side is small. In addition, since shape control is performed by a bender operation as a crown control device in a plurality of stands including the final stand, there is a fundamental problem that a local shape change in the width direction such as a quarter wave cannot be controlled.

  The present invention makes it possible to control the amount of local elongation in the plate width direction, which has not been possible with conventional actuators such as benders or work roll shifts, and without operating complicated crown control devices for each stand. It is an object of the present invention to provide a shape control method and a shape control apparatus between finish rolling stands for a strip that suppress the shape failure of the strip.

  In order to solve the above-mentioned problem, the strip shape control method according to the first configuration of the present invention is based on a shape meter installed between at least one finishing rolling stand of a finishing mill having a plurality of finishing rolling stands. , Measure the shape of the strip in the plate, based on the shape data measured by the shape meter, determine the location and amount of heating in the width direction of the strip, at least installed on the upstream side of the finishing mill The strip is heated by controlling the position and heat generation amount of the two transverse induction heating devices, and the shape defect of the strip during finish rolling is suppressed.

  In the first configuration of the present invention, in order to suppress the shape defect between the finish rolling stands of the strip rolled by the finish rolling mill, the plate width direction shape is measured with a shape meter, and the plate width direction temperature control is performed. At least two possible transverse induction heating devices are installed upstream of the finishing mill to manipulate the temperature distribution in the width direction of the strip. Since the temperature of the heating position of the strip is high, the thermal expansion of the work roll of the finishing mill that is in contact with that portion is increased, and the roll gap is locally narrowed. Further, since the deformation resistance of the strip is lowered at the heating position, the work roll flatness in the roll biting portion is locally reduced, and the action of narrowing the roll gap works. This makes it possible to control the amount of local elongation in the plate width direction, which was not possible with conventional actuators such as benders and work roll shifts, and without having to operate complicated crown controllers on each stand. The control which suppresses the shape defect of a strip in can be performed.

The wave shape of the strip, that is, the difference in elongation in the width direction, occurs due to a change in the crown ratio (crown amount / plate thickness) on the entry / exit side of each finishing rolling stand.
For example, in the case of a medium wave shape in the finishing rolling stand F5-F6 at the latter stage of the finishing mill, the crown ratio is greatly changed in the minus direction at the finishing rolling stand F5, that is, it is generated by suddenly rolling down in the low crown direction. If the crown of the strip on the entry side of the finish rolling stand F5 is reduced to reduce the change in the crown ratio, the medium wave shape is reduced and approaches the flat shape. As a means for that purpose, the plate thickness central portion of the strip is heated by an induction heating device installed on the entrance side of the finishing mill, and the thickness of the central portion in the width direction of the strip is reduced from the finish rolling stand F1 by the mechanism described above. Thus, the crown can be lowered, and the change in the crown ratio at the finish rolling stand F5 can be reduced.

Further, in this method, since the plate crown can be gradually changed from the finishing rolling stand F1 to the finishing rolling stand in which the wave shape is generated, when operating the bender of the finishing rolling stand, the work roll shift, and the actuator of the reduction device The balance of the crown ratio with the finish rolling stand before and after the occurrence of the trouble is not greatly lost.
For the ear waves that extend at both ends in the width direction of the strip, the crown at the front stage of the finish rolling stand is reduced by heating the both ends in the width direction of the strip with an induction heating device. Suppress changes in the crown ratio at the later stage to reduce the shape of the ear wave.
Furthermore, even for quarter waves, local unevenness is generated continuously and gently from the front stage of the finishing rolling stand by raising the temperature in the width direction where quarter waves are generated in the latter stage with an induction heating device using the same mechanism. By doing so, it becomes possible to reduce local elongation at the finishing rolling stand.

  As a means for heating the strip, a solenoid type induction heating device is known (for example, see JP-A-3-314216). In this, a coil (solenoid) is wound so as to surround the strip, and parallel to the plate. Since the entire surface of the plate is heated by generating a magnetic field, local heating in the width direction of the strip cannot be performed. Therefore, in the present invention, a plurality of (two or more) transverse type induction heating apparatuses that can divide the width direction into a plurality of portions and independently perform local heating independently are used.

The strip shape control method according to the second configuration of the present invention controls the position of the transverse induction heating device so as to heat the generation position of the strip waveform measured by the shape meter, and the waveform The amount of heating is determined from the steepness of.
With this second configuration, it is possible to control the position of the induction heating device and the amount of heat generated according to the wave pattern, and to control strip shape defects between the finishing rolling stands. In order to determine the heating amount from the steepness of the wave shape, the relationship between the steepness and the heating amount is obtained in advance by experiment and stored, and the heating amount corresponding to the steepness obtained from the wave shape measured by the shape meter is determined. Just decide. After heating is started with the heating amount once determined, a change in steepness is sequentially measured with a shape meter, and the result is fed back to control the heating amount.

The strip shape control apparatus according to the third configuration of the present invention includes at least two transverse induction heating apparatuses installed upstream of a finishing mill having a plurality of finishing rolling stands, and the finishing mill Based on the shape meter installed between at least one of the rolling stands and the shape data measured by the shape meter, the location and amount of heating in the width direction of the strip are determined, and the transverse induction heating device And an induction heating control device for controlling the position and the amount of heat generation.
In the strip shape control apparatus according to the third configuration, in order to flatten the plate shape between the finish rolling stands, the transverse direction shape can be measured with a shape meter and the transverse direction temperature control can be performed. A die induction heating device is installed on the upstream side of the finish rolling mill, and the temperature distribution in the width direction of the strip is manipulated to control the deformation resistance distribution. By thermal expansion, it is possible to control the amount of local elongation in the plate width direction, which was impossible with conventional actuators such as benders and work roll shifts, and without operating complicated crown controllers on each stand. Control is performed to suppress strip shape defects between finish rolling stands.

  According to the present invention, the shape of the strip in the plate is measured by a shape meter installed between at least one rolling stand of a finishing mill equipped with a plurality of finish rolling stands, and measured by the shape meter. Based on the shape data, the location and amount of heating in the width direction of the strip are determined, and the position and heat generation amount of at least two transverse induction heating devices installed upstream of the finishing mill are controlled. The strip is heated to suppress strip shape defects during finish rolling, enabling local elongation control in the plate width direction, which was not possible with conventional benders or work roll shift actuators. In addition, it is possible to suppress strip shape defects between the stands without operating complicated crown control devices for the stands.

It is the schematic of the hot finishing rolling equipment which concerns on embodiment of this invention. It is a control flow figure of the strip shape control method concerning an embodiment of the invention. It is a perspective view which shows the structure of the optical inter-stand shape meter used for the shape control method of the strip which concerns on embodiment of this invention. It is a graph which shows the plate shape measurement pattern by the optical inter-stand shape meter which concerns on embodiment of this invention. It is explanatory drawing which shows the definition of steepness. It is a perspective view which shows the example of arrangement | positioning of each induction heating apparatus which comprises the transverse type induction heating apparatus which concerns on embodiment of this invention. The upper figure in (a) is a plan view showing the position of the induction heating device in the case of medium waves, the lower figure is a graph showing the temperature rise characteristics in that case, and the upper figure in (b) is in the case of ear waves The top view which shows the position of the induction heating apparatus in FIG., The lower figure is a graph which shows the temperature rising characteristic in that case, The upper figure of (c) is the top view which shows the position of the induction heating apparatus in the case of quarter wave, The figure is a graph showing the temperature rise characteristics in that case. It is a figure which shows the pattern of an inter-stand board shape.

Embodiments of the present invention will be specifically described below with reference to the drawings.
As shown in the schematic diagram of FIG. 1, the hot finish rolling facility according to the embodiment of the present invention includes a finish rolling mill 1 including finish rolling stands F1 to F7, and in this example, between finish rolling stands F5 and F6. The installed shape meter 2 and the induction heating control device 3 that controls the transverse induction heating device 4 based on the shape of the strip measured by the shape meter 2 are provided. In this example, as shown in FIG. 6, the transverse type induction heating device 4 has two pairs of induction heating devices 4-1 and 4-2 arranged in the rolling direction of the strip with the upper and lower sides as a pair. Each induction heating device 4-1, 4-2 is independently movable in a direction (width direction) perpendicular to the strip rolling direction.

  The operation of the optical shape meter used as the shape meter 2 in the embodiment of the present invention will be described with reference to FIG. As shown in FIG. 3, the shape meter 2 is a pulse-shaped rod-shaped light source 10 such as a strobe that illuminates the surface of the strip S, and a CCD camera that captures a rod-shaped light source image formed on the surface of the strip S. It is composed of a two-dimensional camera 11, and the rod-shaped light source 10 and the two-dimensional camera 11 are in positions facing each other on both sides of the strip S, and the surface of the straight horizontal strip S connecting the center of the rod-shaped light source 10 and the two-dimensional camera 11. This is a shape measuring device in which the main projection line is inclined with respect to a straight line extending in the width direction of the strip S.

  In this shape measuring apparatus, the surface of the strip S is illuminated by strobe light emission with the rod-shaped light source 10 while feeding the strip S in the rolling direction. The rod-shaped light source 10 emits strobe light by a pulse voltage from a power source (not shown), and the shutter of the two-dimensional camera 11 is opened. As a result, an image of the surface of the strip S synchronized with the light emission of the rod-shaped light source 10 is captured by the two-dimensional camera 11.

  The position where the rod-shaped light source image is formed changes according to the distortion of the strip S. The relationship between the position of the rod-shaped light source image and the distortion amount is obtained in advance by calculation or experiment, and the relationship between the image position and the distortion amount is stored in the induction heating control device 3 as a calculation table. The shape of the strip S can be obtained by measuring the position of the image on the surface of the strip S irradiated by the rod-shaped light source 10 while feeding the strip S in the longitudinal direction, and sequentially accumulating it in the longitudinal direction of the strip S.

FIG. 4 is a graph showing an example of output corresponding to the three deformation patterns of the strip measured by the shape meter 2. In this graph, the horizontal axis indicates the position in the width direction of the strip (distance from the DS end), the vertical axis indicates the steepness, and the steepness distribution in the plate width direction indicates the wave shape. In the example in the graph, the ear wave indicated by the solid line has higher steepness at both ends in the width direction of the strip than the central portion, and the medium wave indicated by the broken line has higher steepness at the central portion than the end portion. In the quarter wave indicated by the dotted line, there is a portion where the steepness is high between the center and the end. Here, the steepness is, as shown in FIG. 5, a ratio between the height δ of the corrugations in the longitudinal direction of the strip and the pitch L (λ = δ / L). When the length of the plate can be approximated as L + ΔL and the plate wave can be approximated as a sine curve, the steepness λ = 2 / π × (ΔL / L) is expressed as ^0.5 .

  As described above, the shape meter 2 measures the local deformation pattern and steepness of the strip shape. Therefore, the induction heating control device 3 is used to control the transverse induction heating device 4 and the upstream of the finishing mill 1. Control the heating in the width direction of the strip on the side.

The control flow will be described with reference to FIG.
In step S110, the shape meter 2 detects the leading end portion of the strip in the passing plate between the finishing rolling stands F5 to F6 and the uneven shape in the longitudinal direction.
In step S 120, the width direction wave generation position and the steepness are transmitted to the induction heating control device 3.
In step S130, the induction heating control device 3 determines the position of the induction heating device 4 to be used. That is, a) When the medium wave is detected, the induction heating device 4 is moved to the center portion of the width direction plate. b) When the ear wave is detected, the induction heating device 4 is moved to both ends of the widthwise plate. c) When the quarter wave is detected, the induction heating device 4 is moved to the position where the quarter wave is generated.
In step S140, the induction heating control device 3 determines the temperature increase amount of the induction heating device based on the temperature increase amount (heating amount) corresponding to the steepness. The temperature increase amount is selected based on a temperature increase output table value corresponding to a preset steepness.
In step S150, the induction heating device 4 is moved to the position determined by the induction heating control device 3.
In step S <b> 160, heating of the induction heating device 4 is started with the temperature increase determined by the induction heating control device 3.

The operation and action of each induction heating device 4-1, 4-2 controlled by the induction heating control device 3 is as follows.
a) When an intermediate wave is detected by the F5-F6 inter-stand shape meter 2, the induction heating devices 4-1 and 4-2 are moved to the center in the width direction of the strip S as shown in FIG. In step S140, the amount of temperature rise of the induction heating device is determined corresponding to the steepness, and either or both of the induction heating devices 4-1 and 4-2 are used to raise the temperature at the center of the strip and finish rolling. By reducing the crown at the front stage F1-F4 stand in the machine, the change in the crown ratio at the F5 stand is suppressed and the medium wave shape is reduced.

  b) When an ear wave is detected by the F5-F6 inter-stand shape meter 2, as shown in FIG. 7 (b), the induction heating devices 4-1 and 4-2 are moved to both ends in the width direction of the strip. In step S140, the temperature increase amount of the induction heating device is determined corresponding to the steepness, the temperature of both ends of the strip S is increased by the induction heating devices 4-1, 4-2, and the first stage F1-F4 of the finishing mill. By reducing the crown at the stand, the change in the crown ratio at the F5 stand is suppressed and the shape of the ear wave is reduced.

  c) When the quarter wave is detected by the F5-F6 inter-stand shape meter 2, the induction heating devices 4-1 and 4-2 are moved to the quarter wave generation position in the width direction as shown in FIG. 7C. In step S140, the heating amount of the induction heating device is determined corresponding to the steepness, the quarter wave generation position is heated by the induction heating devices 4-1 and 4-2, and the first stage F1-F4 of the finishing mill. The quarter wave is reduced by increasing the extension of the quarter wave generation position from the stand within a necessary minimum range and alleviating the local thickness change at the F5 stand.

In the present embodiment, an example in which two pairs of induction heating devices are provided is shown, but three or more pairs can be sequentially arranged in the rolling direction of the strip to further finely control the heating of the strip. Further, the apparatus for heating the edge of the strip is not limited to the induction heating apparatus, and an edge heater may be used.
In addition, the installation position of the shape meter is not limited to between F5-F6 stands, for example, it may be installed between F6-F7 stands or between F4-F5 stands, Ideally, installation between all stands is desirable.

  The present invention enables local elongation amount control in the plate width direction, which was impossible with an actuator such as a conventional bender or work roll shift, and without operating complicated crown control devices for each stand. It can be used in the field of hot rolling as a strip shape control method which suppresses strip shape defects between stands.

DESCRIPTION OF SYMBOLS 1 Finishing mill 2 Shape meter 3 Induction heating control apparatus 4 Transverse type induction heating apparatus 4-1, 4-2 Induction heating apparatus 10 Bar-shaped light source 11 Two-dimensional camera

Claims (3)

  By a shape meter installed between at least one finish rolling stand of a finish rolling mill equipped with a plurality of finish rolling stands, the shape of the strip in the plate is measured, and based on the shape data measured by the shape meter, Determine the location and amount of heating in the width direction of the strip, heat the strip by controlling the position and heat value of at least two transverse induction heating devices installed upstream of the finishing mill, A strip shape control method, characterized by suppressing strip shape defects during finish rolling.   The heating amount is determined from the steepness of the wave shape by controlling the position of the transverse induction heating device so as to heat the generation position of the wave shape of the strip measured by the shape meter. The strip shape control method according to claim 1. At least two transverse induction heating devices installed upstream of a finishing mill with a plurality of finishing rolling stands;
A shape meter installed between at least one finishing rolling stand of the finishing mill;
Based on the shape data measured by the shape meter, an induction heating control device that determines the heating location and heating amount in the width direction of the strip, and controls the position and heat generation amount of the transverse induction heating device;
A strip shape control device.

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