JP2007196261A - Method and apparatus for detecting/controlling edge drop in cold rolling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out accurate edge drop control by means of a scanning type profile meter using a low priced γ ray thickness gauge. <P>SOLUTION: A fixed type thickness gauge and scanning type thickness gauges using γ ray sources are arranged on the inlet side of a cold rolling mill train 6. The fixed type thickness gauge 2 measures the thickness of the central portion of a strip 1. Besides, the scanning type thickness gauges 3 measure the plate thickness profile in the direction of the width by mechanically scanning the strip 1 in the direction of the width. When a feedforward control of the edge drop for changing shift positions of work rolls 7 is carried out based on the measured plate thickness profile, the plate thickness profile estimated using the measured values by the γ ray thickness gauges arranged inside the edge portions of the plate width is used as the plate thickness profile at the edge portions of the plate width, where the accuracy of the γ ray thickness gauges cannot be assured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for detecting and controlling edge drop in cold rolling, and in particular, an edge end in the width direction by a tapered crown applied to the end of a work roll, which is suitable for use in a thin steel plate. The present invention relates to a method and an apparatus for detecting and controlling edge drop in cold rolling, which can reduce edge drop generated in a section and reduce thickness direction thickness deviation.

  In cold rolling, it is common for the edge portion of the plate to have a so-called edge drop, in which the plate thickness is sharply thinner than the central portion due to the rapid recovery of the work roll flatness and the metal flow in the width direction of the rolled material. It is. If this edge dop is large, a uniform plate thickness cannot be obtained in the plate width direction, and in order to obtain a product with good quality, it is necessary to increase the ear cutting margin, resulting in a decrease in yield and inefficient production. The

  Conventionally, methods for reducing this edge drop include a method of applying a bending force to the roll and a method of applying an initial crown to the work roll.

  Further, Patent Document 1 discloses a method in which a simple tapered crown is applied to the roll end, the work roll is shifted in the axial direction, and the edge of the plate is rolled with this taper.

  In these controls, in order to compensate for the crown fluctuation of the base plate coil (hot coil), as shown in Patent Document 2, the edge drop meter installed on the outlet side of the cold rolling mill determines the edge A feedback control that measures the actual drop value and changes the work roll shift position based on the deviation from the target value, and as shown in Patent Document 3, a hot-coil is installed by installing a profile meter on the rolling mill entrance side. Feed forward control is performed to measure the crown of the workpiece roll and change the taper position of the work roll based on the measured value.

JP 55-77903 A Japanese Patent Laid-Open No. 60-12213 Japanese Patent Laid-Open No. 61-222619

  According to these methods, it is possible to compensate for the crown variation of the hot coil and stably reduce the edge drop after the cold rolling, but the edge drop meter on the outlet side or the inlet side of the cold rolling mill. It is necessary to install a measuring instrument that can measure the thickness deviation in the plate width direction, called a profile meter.

  As shown in FIG. 1, as a method of measuring the strip width direction profile of the strip, two types of thickness measuring devices of a fixed type and a scanning type using a radiation source are arranged. The thickness of the central portion of the strip 1 is measured, while the scanning type measuring device 3 mechanically scans the strip 1 in the plate width direction to measure the plate thickness profile in the width direction, as shown in FIG. In addition, a method of continuously measuring a plate thickness profile in the width direction by arranging a radiation generator 4 and a multi-channel radiation detector 5 in place of the scanning measuring device 3 has been put into practical use.

  X-rays or γ-rays are used as radiation sources for these profile meters. X-ray thickness gauges using X-rays are capable of obtaining large doses easily and providing profile measurements because of their excellent low noise and high-speed response. In particular, a profile meter combined with the multi-channel type measuring device is suitable for measuring a profile in the vicinity of an edge portion, but has a disadvantage that it is expensive.

  On the other hand, as a γ-ray thickness meter for the purpose of measuring a cold-rolled steel sheet, an Am (Americium) thickness meter having a thickness measurement range of 0 to 5 mm is generally used. Although it has the advantage of being inexpensive compared to the conventional method, it is difficult to increase the dose, so it is difficult to apply it to a multi-channel profile meter. The measurement accuracy at the outermost edge has a limit because it is as large as 25 to 50 mmφ, and the range in the plate width direction that can guarantee the accuracy is limited to the plate width end from the plate width end to the center of the plate width at most. It is done.

  However, the target range of edge drop control in cold rolling is the range of approximately 50 mm at the end of the plate width, and the plate thickness in this range cannot be measured accurately. It has the disadvantage of being unsuitable for use.

  The present invention has been made to solve the above-described conventional problems, and it is an object of the present invention to enable highly accurate edge drop control by a scanning profile meter using an inexpensive γ-ray thickness meter.

  As a result of detailed analysis of the mother coil used for cold rolling, the inventors can estimate from the inner crown if the profile is in the range of 20 to 30 mm from the outermost edge. And found the present invention.

  That is, the present invention uses a γ-ray source, for example, one fixed type and, for example, one or two scanning type plate thickness measuring instruments are arranged on the inlet side of the cold rolling mill row, and the fixed type The thickness gauge measures the thickness at the center of the strip, while the scanning thickness gauge measures the workpiece using the thickness profile in the width direction measured by mechanical scanning in the width direction of the strip. When performing feed-forward control of edge drop that changes the roll shift position, the γ-ray thickness meter measurement value inside the plate width end is shown in the plate thickness profile at the end of the plate width where the accuracy of the γ-ray thickness meter is not guaranteed. The above-mentioned problem is solved by using the plate thickness profile estimated by using.

  In addition, as a method of estimating the profile of the plate width end from the measured plate thickness inside the plate width end, the measurement crown inside the plate width end is fitted to a plurality of even-ordered multi-order equations. The profile of the plate width end portion is estimated using this equation.

  Alternatively, the relationship between the crown and the plate width end profile at a predetermined position inside the plate width end is statistically calculated in advance, and this is used to measure the plate width end from the measurement crown inside the plate width end. The profile of the department is estimated.

  The present invention also provides an edge drop control method in cold rolling, wherein feedforward control is performed using the edge drop detected by the above method.

  Also, a fixed plate thickness measuring instrument using a γ-ray source for measuring the thickness of the central portion of the strip, which is arranged on the inlet side of the cold rolling mill row, and mechanical in the strip width direction. Γ-rays using a γ-ray thickness measuring instrument inside the plate width end and a scanning plate thickness measuring instrument using a γ-ray source to measure the thickness profile in the strip width direction. An apparatus for detecting an edge drop in cold rolling, comprising means for estimating a plate thickness profile at the end of the plate width where the accuracy of the thickness gauge is not guaranteed.

  Further, the present invention provides an edge drop control device in cold rolling characterized by including the detection device.

  According to the present invention, it is possible to perform edge drop control with high accuracy up to the outermost edge by using an inexpensive γ-ray thickness meter, and it is possible to manufacture a steel sheet having a small edge drop with inexpensive equipment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 3 shows a configuration example suitable for applying the present invention. A fixed-type and scanning-type plate thickness measuring device using a radiation source is arranged on the entrance side of the rolling mill group 6, and the fixed-type plate thickness measuring device 2 measures the thickness of the central portion of the strip 1, while The scanning plate thickness measuring device 3 mechanically scans the strip 1 in the plate width direction to measure the plate thickness profile in the width direction. The scanning plate thickness measuring device 3 may be one, but it is preferable to arrange two of the working side 3a and the driving side 3b.

In the measuring apparatus of such a profile, the position of the scanning instrument 3 shown in FIG. 4, if sufficiently widthwise center side than Itatan as x _1, emitted from the radiation source 31 since all of the radiation passes through the strip 1, but it can measure the thickness without problems by attenuation thereof, the position of the scanning instrument 3 and the Itatan near as x _2, scattered rays 8 More radiation than is originally generated and incident through the strip 1 is incident on the detector 32 and, as a result, is measured as a thickness that is less than the true thickness that should originally be obtained. Become.

FIG. 5 schematically shows this relationship, and the plate thickness error occurs because the distance from the plate end of the measuring device is approximately x _A from the plate end which is smaller than the size D of the radiation source 31. It is a range. Here, in the case of a plate thickness meter using X-rays capable of obtaining a large dose as a radiation source, since the size D of the radiation source is several mm, this error is unlikely to be a problem. In the case of a thickness gauge using γ-rays, the radiation source size D is about 25 to 50 mm, which is fatal in that the range of about 50 mm from the edge used for edge drop control cannot be measured accurately. As described above, it has a drawback.

Therefore, in the present invention, in FIG. 5, by the profile of the range of the plate end of x _A, estimated using precisely measured thickness profile of the sheet width center side than x _A from plate end, said The problem is solved.

  As a method for estimating the plate thickness profile at the end of the plate width, the following two methods are suitable.

The first method is a method of estimating the plate thickness profile of the plate width end using this equation by fitting the measurement crown inside the plate width end to a plurality of even-ordered multi-order equations. is there. That is, using the inside of the crown measured values from the sheet width end portion for each coil, to determine the coefficient of the formula a _1, a _2, · · ·, the a _n

^{_{Cr (x) = a 1 X}} m1 + a 2 X m2 + ··· + a n X mn ... (1)

Here, as shown in FIG. 6, X is a distance from the center of the plate width, and Cr is a crown at a position X from the center of the plate width. In addition, m ₁ , m ₂ ,..., _Mn are arbitrary even numbers, but it is important to select this combination appropriately so that the plate thickness profile at the plate width end can be estimated. According to the study by the inventors, a multi-order expression of three or more terms including the terms of the second order and the tenth order or more is suitable. Since it changes depending on the operating conditions and the edge cutting process in the intermediate process, it is desirable to collect samples in advance for each line to be applied and determine the optimum combination. Further, these coefficients may be determined by simultaneous equations from n measurement points, or by multiple regression from n + 1 or more measurement points.

Next, in the second method, the relationship between the crown and the plate thickness profile of the plate width end portion at a predetermined position inside the plate width end portion is statistically obtained in advance, and this is used to calculate the plate width end portion. This is a method of estimating the plate thickness profile at the plate width end portion from the measurement crown inside the plate portion. That, _x 1 from the plate width end portions which can accurately measured according to the following equation in this _{way, x 2, ···,} x _n positions of the crown _{Cr (x1), Cr (x2} ), ···, Cr The crown Cr _{(x) in} the plate width end region is estimated from _(xn) .

Cr _(x) = f _{0 (x)} + f _{1 (x)} Cr _{(x 1 )} + f _{2 (x)} Cr _{(x 2)} +... + F _{n (x)} Cr _{( x n )}
... (2)

Here, f _{0 (x)} , f _{1 (x)} , f _{2 (x)} ,..., F _{n (x)} are coefficients relating to the respective terms and are functions of the distance x from the plate edge. Further, the measurement points x ₁ , x ₂ ,..., X _n used for estimation include at least the points closest to the plate edge that can be measured accurately according to the inventors' investigation, and three points from the edge to about 100 mm. Although it is preferable to make the above points, also regarding these coefficients and measurement points, as in the first method, the cold rolling base plate that is the subject of the present invention is the operating conditions of hot rolling, Since it changes depending on the ear-cut process in the intermediate step, it is desirable to determine by taking a sample in advance for each applied line.

Comparative example

  First, as a conventional method, measurement was performed up to the plate edge with γ-rays, and the measurement was made with a contact-type plate thickness meter in an offline state (hereinafter referred to as a true value). An example is shown in FIG. It can be seen that the measured value by the γ-ray thickness gauge is abruptly smaller at the edge of the plate than 25 mm from the edge, compared to the true value of the thickness profile measured by the contact-type thickness gauge. 8A to 8F show a comparison between the true crown value from the edge 25 mm to the outermost edge and the measured value by the γ-ray thickness gauge for the sample of 100 coils. Show.

  As can be seen, the plate edge has a larger error than the edge 25 mm, and it was impossible to use the measured value for edge drop control.

Using the first method described above, the plate thickness profile on the plate end side from the edge 25 mm with a large error was estimated using the measurement result on the plate width center side from the edge 25 mm with a small measurement value error due to γ rays. As a result of analyzing the conditions for accurately estimating the plate thickness profile at the plate end, it is preferable to use the measured values of the edges 25 to 100 mm and fit them to a multi-order equation consisting of the 4th order of the 12, 12, 18, and 20th order. there were. That is, for each coil, the coefficients a _{1 to} a ₄ of the following equation were obtained using the measured values of the edges 25 to 100 mm, and the plate thickness profile on the plate end side from the edge 25 mm was estimated from this result.

^{_{Cr (x) = a 1 X}} 2 + a 2 X 12 + a 3 X 18 + a 4 X 20 ... (3)

  An example is shown in FIG. 9A to 9E show a comparison between the true crown value and the estimated value according to the present invention for the same sample as the comparative example, and Table 1 shows the average value and standard deviation of the error together. It can be seen that the estimation accuracy is sufficient for use in edge drop control.

  The plate thickness profile on the plate end side from the edge 25 mm with a large error was estimated by using the measurement result on the plate width center side with respect to the edge 25 mm with a small error in the measurement value due to the γ rays by the second method described above. In this case, the relationship between the plate thickness profile on the center side of the plate width from the edge 25 mm and the plate thickness profile on the plate end side from the edge 25 mm was formulated in advance. As a result of analyzing the conditions for accurately estimating the plate thickness profile at the plate end, it was preferable to use the crown measurement values at four points of the edges 25, 30, 35 and 50 mm.

Cr _(x) = f _{0 (x)} + f _{1 (x)} Cr ₍₂₅₎ + f _{2 (x)} Cr ₍₃₀₎ + f _{3 (x)} Cr ₍₃₅₎ + f _{4 (x)} Cr ₍₅₀₎
... (4)

That is, f _{0 to} f ₄ were obtained as shown in FIG. 10 with respect to the crown of the plate end expressed as in equation (4). These constants or coefficients could be well expressed by a quadratic expression such as

f _{i (x)} = a _i x ² + b _i x + c _i (5)

  Table 2 shows constants and coefficients.

  For each coil, the measured values of the edges 25, 30, 35 and 50 mm with γ rays were substituted into the equation (4), and the plate thickness profile on the plate end side from the edge 25 mm was estimated. An example is shown in FIG. 11A to 11E show a comparison between the crown true value and the estimated value according to the present invention for the same sample as the comparative example, and Table 1 shows an average value and standard deviation of errors. As in the first embodiment, it can be seen that the estimation accuracy is sufficient for use in edge drop control.

  As described above, according to the present invention, it is understood that edge drop at the edge of the plate can be detected with high accuracy even if an inexpensive γ-ray thickness gauge is used, and advanced edge drop control can be performed.

  The number of fixed plate thickness measuring instruments is not limited to one, but may be two or more, and the number of scanning plate thickness measuring instruments is not limited to one or two, but may be three or more. .

Schematic diagram showing how to measure the thickness profile using a scanning thickness gauge Schematic diagram showing how to measure the thickness profile using a multi-channel thickness gauge Schematic diagram showing a preferred configuration example for carrying out the present invention Schematic diagram showing the positional relationship between the scanning measuring instrument and the sheet width direction of the steel sheet Conceptual diagram showing measurement accuracy of thickness profile Explanatory drawing showing the definition of crown Comparison diagram of measured values of plate thickness profiles in comparative examples and examples Relationship diagram between crown true value and measured value of comparative example Relationship diagram between true crown value and measured value of Example 1 Relationship diagram between constants and coefficients in the width direction in Example 2 Relationship diagram between true crown value and measured value of Example 1

Explanation of symbols

1 ... Strip (steel plate)
2 ... Fixed plate thickness measuring device 3, 3a, 3b ... Scanning plate thickness measuring device 4 ... Radiation generator 5 ... Multichannel radiation detector 6 ... Rolling mill 7 ... Work roll 8 ... Scattered radiation

Claims (6)

Fixed type and scanning type thickness measuring instruments using γ-ray sources are arranged on the inlet side of the cold rolling mill row, and the fixed type thickness measuring instrument measures the thickness at the center of the strip, while the scanning type When performing a feedforward control of the edge drop that changes the shift position of the work roll using the thickness profile in the width direction measured by mechanically scanning the strip thickness direction in the strip width direction,
A sheet thickness profile estimated by using a gamma ray thickness meter measurement value inside the sheet width end is used as the sheet thickness profile at the sheet width end where the accuracy of the γ-ray thickness meter is not guaranteed. Edge drop detection method in hot rolling.   The measurement crown inside the plate width end portion is fitted to a predetermined multi-order equation composed of a plurality of even orders, and the plate thickness profile of the plate width end portion is estimated using this equation. An edge drop detection method in cold rolling as described.   The relationship between the crown at a predetermined position inside the plate width end and the plate thickness profile of the plate width end is statistically calculated in advance, and this is used to measure the plate width from the measured crown inside the plate width end. 2. The edge drop detection method in cold rolling according to claim 1, wherein a thickness profile of the end portion is estimated.   An edge drop control method in cold rolling, wherein feedforward control is performed using the edge drop detected by the method according to claim 1. A fixed plate thickness measuring instrument using a γ-ray source for measuring the thickness of the central part of the strip arranged on the inlet side of the cold rolling mill row and mechanically scanning in the strip width direction. A scanning plate thickness measuring device using a gamma ray source for measuring a plate thickness profile in the strip width direction;
Means for estimating the plate thickness profile of the plate width end where the accuracy of the γ ray thickness meter is not guaranteed, using the measured value of the γ ray thickness meter inside the plate width end;
An apparatus for detecting an edge drop in cold rolling, comprising:   An apparatus for controlling edge drop in cold rolling, comprising the detection apparatus according to claim 5.