JPH04351215A - Method and device for correcting cross buckle in sheet rolling - Google Patents

Abstract

PURPOSE:To detect the cross buckle of extremely sheet that can not be detected by a traditional method and to surely correct it. CONSTITUTION:A linear image is projected in the vicinity of the outlet of work rolls 2, 3, the destorted image that is reflected from a sheet, is photographed with a telecamera 8 and image processing is executed. The case that the reflected image on the sheet is wavy and that this wave is moved in the breadthwise direction with the progress of rolling is judged as cross buckle and correction is executed. When rolling extremely thin sheet, cross buckle could not be detected and corrected. It has been the major cause of the decrease of yield, but yield is drastically improved by this invention.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet rolling mill, and more particularly to a method for correcting a phenomenon called cross buckling or herringbone in a cold sheet rolling mill, and an apparatus therefor.

0002

BACKGROUND OF THE INVENTION In recent years, in the field of cold-rolled products, there has been a strong demand for wide and thin plates, and there is also a trend toward higher quality materials with higher hardness. For this reason, efforts have been made to reduce the diameter of work rolls in cold rolling mills. When rolling thin, hard materials with small diameter work rolls, the incidence of cross buckling is extremely high. Cross buckles are fine washboard-like wrinkles that generally occur at an angle to the material. Cross buckles were difficult to correct once they occurred. In other words, the phenomenon of edge elongation and mid-elongation is different from the plate shape, and therefore cannot be eliminated by conventional shape control devices. For this reason, materials with cross buckles require a separate correction process using a tension leveler or the like, which is a major cause of reduced productivity.

A conventional method for correcting a cross buckle is the method shown in FIG. 3, which is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-219410. In other words, the cross buckle generated in material 1 is transferred to work roll 2,
At a location away from the exit 3, images are taken directly from above with a television camera 8 and image processing is performed. The image is held by a sample hold device 9, and the shading of the held image is processed by a processing device 10.
A diagonal striped pattern is obtained by binarizing the image. The longitudinal direction of the rolled material is taken as the y-axis, and the width direction is taken as the x-axis, and a group of sunspots among them is calculated by the calculator 11 using the least squares method.
y=ax+b

It is approximated by the linear equation (Equation 1). The angle α of the striped pattern of the cross buckle with respect to the board width direction is usually 20° to 6
Since it is about 0°, the coefficient a in equation (1) is tan20°<a<tan60°
(Number 2
), it is determined that a cross buckle has occurred; otherwise, the determiner 12 determines that a cross buckle is not occurring. This sends a signal to the correction device as to the presence or absence of the cross buckle. There are also various known examples of cross buckle correction methods. Method for increasing forward tension found in JP-A-61-219410, JP-A-63-2248
There are methods such as the method of tilting the material outflow angle with respect to the pass line as seen in Japanese Patent No. 08, and the method of controlling the deflection in the horizontal plane of the work roll as seen in Japanese Utility Model Application No. 195104/1983.

0004

[Problems to be Solved by the Invention] The above conventional method has the following drawbacks. In other words, when the thickness of the material becomes extremely small, especially 0.1 mm or less, even if cross buckling actually occurs, the tension during rolling will smooth out the wrinkles in the material and cause it to separate from the work roll exit. It looks flat at first glance. In this case, the cross buckle becomes visible only after rolling is finished and the tension is released. Therefore, during rolling, the cross buckle cannot be detected by the conventional method and cannot be corrected, resulting in a decrease in product yield. An object of the present invention is to provide a method and apparatus that can detect the occurrence of cross buckling in materials of any thickness and can correct it.

[0005]

[Means for Solving the Problems] The cross buckle is photographed at a location away from the work roll exit, and the plate surface is photographed near the work roll exit. At this time, a linear image is projected near the exit, and it is detected that the image is distorted into a wave shape when reflected by the plate. This distortion occurs even when a simple vertical wrinkle occurs, but in the case of a cross buckle, it can be determined by whether or not the corrugation moves in the width direction of the sheet as rolling progresses. In the case of simple vertical wrinkles, the waves do not move. Furthermore, even if the plate thickness is so small that the cross buckle cannot be seen at a distance from the work roll exit, the movement of such waves occurs and the cross buckle can be detected. The present invention was made based on such experimental facts.

[0006]

[Operation] When a cross buckle occurs, a wave-like distortion occurs near the exit of the work roll of the material, and this wave moves in the width direction of the sheet. By projecting a linear image near the exit, waves can be made apparent. As a result, a clear captured image can be obtained, and the accuracy of image processing is improved.

[0007]

[Embodiment] An embodiment of the present invention is shown in FIG. A rolled material 1 is being rolled by work rolls 2 and 3. A rod-shaped light source 6 is installed near the roll exit, and a television camera 8 photographs an image 7 projected onto the material surface. The obtained image is held in a sample hold device 9, and the gradation of the held image is binarized in a processing device 10 to obtain a wavy line. Next, the pitch and height of this waveform are determined by the arithmetic unit 11, and various methods can be considered for this purpose. One method is to approximate the following sine curve using the least squares method. Here, the longitudinal direction of the rolled material is the y-axis, the width direction is the x-axis, and the origin is the center of the plate.

y=Asin(Bx+C)

(Equation 3) In Equation (3), the coefficient A can be said to be a parameter indicating the height of the wave, the coefficient B the pitch, and the coefficient C the phase. From this, the determiner 12 determines whether or not a cross buckle has occurred based on the following determination criteria. First, a large value E with an error when performing least squares approximation
If it is larger, it means that the obtained line shadow does not have a regular wave shape, and it is determined that it is not a cross buckle. Next, if the wave height A is smaller than a certain small value ε1, even if there is a cross buckle, it is extremely slight and can be ignored.
It is determined that there is no such thing. Next, when A is large to some extent, it is determined whether the waves move in the width direction (x-axis direction) to distinguish them from simple vertical wrinkles. For this purpose, equation (3) is approximated at a certain short time pitch, and temporal changes in the phase C are observed. Assuming that the phase at time t1 is C1 and the phase at time t2 is C2, the speed at which the phase changes VC is determined by the following equation.

VC=(C2-C1)/(t2-t1)
(Equation 4) At this time, the speedometer 14 connected to the defroller 13 detects whether rolling is in progress, that is, whether the plate is advancing, and outputs the speed VR to the determiner 12. Naturally, the determination itself is not performed when rolling is not being performed. During rolling, if VC is smaller than a certain small value ε2, it is assumed that the waves do not move, and it is determined that vertical wrinkles have occurred, and that there is no cross buckle. When VC is large to a certain extent, it is determined that there is a cross buckle, and a signal is sent to the correction device 15. Cross buckle modification is accomplished by increasing the forward tension in a known manner. That is, upon receiving the cross buckle presence signal, the forward tension increment ΔT is output to the controller 18 that adjusts the motor 17 of the reel 16. This is repeated until it is determined that there is no cross buckle, but a certain limit is set for the front tension due to concerns about plate breakage. Therefore, if the forward tension exceeds this, a switch is made to other correction means. This is done by moving up and down the roller 19 disposed between the work roll and the defroller to change the flow angle of the material. The roller height increment amount Δh is output to the roller height adjusters 20 and 21, and the outflow angle is sequentially increased until the cross buckle is corrected. By combining these two types of correction methods,
Cross buckles can be reliably corrected. As for the cross buckle correction method, known means such as a method of controlling the deflection of the work roll in the horizontal plane or a method of controlling the inclination in the horizontal plane can also be used.

The present invention is of course not limited to the above-described embodiments, and various other modifications are possible. For example, in image processing methods, instead of approximating a sine curve, the maximum and minimum values of the wave are extracted, and the wavelength of the wave is calculated from the average value of the pitch in the width direction between each maximum value and each minimum value. The wave height can also be determined from the average height between the minimum value and the minimum value. In addition, methods other than image processing are also possible. FIG. 4 shows another embodiment. A large number of gap sensors 22 are arranged near the roll exits of the work rolls 2 and 3 to measure the height distribution in the width direction of the plate surface. The outputs of all these sensors are collected in the sample holder 23, and all outputs at a certain time are stored simultaneously. This determines the height distribution in the width direction of the plate surface at a certain time. The subsequent processing is exactly the same as the embodiment shown in FIG. That is, the arithmetic unit 11 approximates this distribution to a sine curve, determines the height and pitch of the wave, and the determiner 12 determines whether or not it is a cross buckle. If it is a cross buckle, the correction device 15
send a signal to.

[0011]

According to the present invention, it is possible to detect cross buckles in extremely thin plate materials, and to reliably correct them. Therefore, cross buckles cannot be detected or corrected during rolling of ultra-thin sheet materials, which was the main cause of lower yields, but this greatly improves yields.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a cross buckle.

FIG. 3 is an explanatory diagram of a conventional method.

FIG. 4 is a block diagram of an embodiment of the present invention.

[Explanation of symbols]

1... Plate material, 2, 3... Work roll, 6... Rod-shaped light source, 7...
Projected image, 8... Television camera, 9... Sample holder, 10
...Binarization processing device, 11... Arithmetic unit, 12... Judgment device, 13
... Deflorer, 14... Speedometer, 15... Cross buckle correction device, 16... Reel, 17... Reel motor, 18...
Motor controller, 19...Roller, 20, 21...Roller height adjuster.

Claims (4)

[Claims] Claim 1: Detecting the height distribution in the width direction of the plate surface near the exit of the work roll, and determining whether this distribution has a wavy shape, and whether this waveform moves in the width direction of the plate as rolling progresses. A cross buckle detection method, characterized in that it is determined whether a cross buckle has occurred in a plate material by determining whether or not a cross buckle has occurred in a plate material. 2. The cross buckle correction method according to claim 1, wherein the cross buckle is corrected if the cross buckle has occurred. 3. A plate surface height detector installed near a work roll outlet; a device for determining whether or not a widthwise height distribution measured by the detector exhibits a wave shape; A cross buckle detection device comprising a device that determines whether a waveform moves in the width direction of the sheet as rolling progresses. 4. The cross buckle correction device according to claim 3, comprising: the detector; and a correction device that corrects the cross buckle using a cross buckle generation signal from the detector.