JP2000158045A - Method for straightening shape of strip steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a strip steel having an excellent shape by eliminating fluctuation in shape or disturbances in measurement in a short span along the longitudinal direction and setting suitable shape-straightening conditions in accordance with the actual change in shape. SOLUTION: A distance is continuously measured from a travelling strip steel to each distance sensor by means of plural sensors arranged along the width direction; the timewise fluctuation of the measured distance is fast Fourier transformed at an interval not less than the time in which a wave generated in the steel strip passes for one period; and the elongation percentage by an elongation roll 1a is controlled so that the peak of the frequency obtained becomes zero. In addition, in straightening C-camber, the distances are each averaged out which are measured by the distance sensors arranged in the center part in the width direction and the edge part of the steel strip; and the rolling reduction of a C-camber straightening roll 1b is controlled in the manner that the difference becomes zero between the average distance at the edge part and that of the center part in the width direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling shape correction by a leveler while measuring the shape of a steel strip in a shape correction line.

[0002]

2. Description of the Related Art Steel strips are given predetermined sizes and material properties by rolling, heat treatment, or the like. However, in a steel strip that has undergone processes such as rolling and heat treatment, warpage in the longitudinal direction (hereinafter, referred to as L warpage), warpage in the sheet width direction (hereinafter, referred to as C warpage), ear elongation, middle elongation, and quarter elongation. (Hereinafter referred to as a wave shape) and the like, and often do not satisfy required flatness specifications. For this reason, shape correction is required as a post-process of rolling and heat treatment, and L-warp, C-warp, corrugation and the like are eliminated by a tension leveler, a roller leveler, or the like.

[0003] straightening by a tension leveler, for example, the bridle roll 2 _in, 2 _out and placed before and after the tension leveler roll 1 as shown in FIG. 1, the additional tension to the steel strip S by bridle rolls 2 _in, 2 _out While the bridle roll 2 _in and 2 _{out have} a difference in peripheral speed, the steel strip S
The shape is corrected by controlling the elongation percentage. Tension leveler roll 1 is arranged a number along the running direction of the steel strip S, and rolls 1 _a acting on the extension of the steel strip S, break up the rolls 1 _b, 1 _c acting on the warp correction.

[0004] The corrugated shape is caused by the fact that the strain along the longitudinal direction of the steel strip S is distributed in the width direction of the steel strip. Is corrected. Since the elongation rate changes with the amount of tension and the tension of the elongation roll, the elongation rate of the elongation roll is set in the elongation area 3 and the tension is changed by the peripheral speed difference between the bridle rolls 2 _in and 2 _out to obtain a predetermined elongation rate. Have gained. In the warp correction area 4, the warpage generated or changed in the extension area 3 is corrected by adjusting the amount of reduction of the correction roll. Various patterns are known with regard to the arrangement of the straightening roll, the warp correction in Figure 1, configured in the second unit 4 ₂ Two units for correcting the first unit 4 ₁ and L warp correcting C warp Region 4 is shown.

[0005] In shape correction using a roller leveler, FIG.
A roller leveler showing a typical roll arrangement is used. A plurality of upper rolls 5 _u and the lower roll 5 _d are staggered from each other, the amount under inlet side pressure and out lateral pressure under weight moves up and down together so that it can be set independently. Generally, the shape of the steel strip S is controlled by adjusting the amount of reduction on the inlet side and the amount of reduction on the outlet side. Since the shape of the steel strip S varies along the longitudinal direction, the shape correction conditions are set while measuring the shape of the steel strip S in-line.

For example, in Japanese Patent Publication No. Hei 3-7330, a shape measuring instrument 6 provided in a line as shown in FIG.
_out , the shape of the steel strip S after the tension leveler straightening is measured, and the shape straightening conditions obtained from the measurement result are output to the elongation rate control device 8 and the rolling reduction amount control device 9. For measuring the shape of the steel strip S, a shape measuring device 6 corresponding to each of L warp, C warp, ear extension, medium extension, and wave shape is used, and the leveler condition is changed based on the measurement result. Is done. In Japanese Patent Application Laid-Open No. 7-96326, as shown in FIG. 4, a shape measuring instrument 6 _in is arranged in the line at the entrance side of the tension leveler, and the wave shape generated in the steel strip S before the tension leveler is corrected is determined. Measuring. The measurement result is output to the elongation rate control device 8 as the shape correction condition, and the shape of the steel strip S is corrected under the condition corresponding to the wave shape. For the measurement of the wave shape, a shape detection roll or a plurality of distance sensors arranged in the plate width direction is used. The distribution of the strain in the width direction of the steel strip S in the plate width direction is calculated from the measurement result, and the leveler condition is set so that the elongation according to the difference in the distribution of the steel strip S is given to the steel strip S.

[0007]

In both the method of measuring the shape after leveler straightening (Japanese Patent Publication No. 3-7330) and the method of measuring the shape before leveler straightening (JP-A-7-96326), the steel strip S The detection signal for evaluating the shape of
It includes a disturbance and constantly fluctuates in the steel strip S. Causes of the disturbance and fluctuation include that the shape measuring devices 6 _in and 6 _out are affected by _flapping of the steel strip S, that the shape of the steel strip S is not constant in the longitudinal direction and the sheet width direction.
Since the shape correction condition obtained from the detection signal including the disturbance is different from the appropriate shape correction condition, the shape of the steel strip S whose shape has been corrected may be rather deteriorated. In addition, since the wave height of the wave shape is slightly changed for each wave, if the shape is corrected by changing the leveler conditions one by one according to the detection signal for evaluating the shape, there is a time lag from the shape measurement to the shape correction. Therefore, the shape of the current steel strip S is corrected based on the past measurement results. Also in this case, the shape of the steel strip S is deteriorated.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in order to solve such a problem. The present invention is directed to a steel strip which is running with a plurality of distance sensors arranged along the width direction of the plate. Continuously measures the shape in the longitudinal direction and the width direction of the strip, and eliminates shape fluctuations and disturbances in a short span along the longitudinal direction of the steel strip, thereby correcting the shape of the steel strip under appropriate conditions over the entire length and width. And to produce a steel strip having a good shape.

In order to achieve the object, the shape correcting method of the present invention continuously measures the distance from a running steel strip to each of the distance sensors with a plurality of distance sensors arranged along the width direction of the steel sheet. Fast Fourier transform of the time change of the measurement distance at intervals longer than the time during which the wave generated in the band passes for one cycle, and controlling the elongation rate of the steel strip so that the peak of the obtained frequency becomes zero. Features. At the same time, C warpage can be corrected by controlling the amount of reduction. In this case, the distances measured by the distance sensors disposed at the center and the ends of the steel strip in the sheet width direction are respectively averaged, and the average distance at the sheet end and the distance at the center of the sheet width direction are measured. The reduction amount of the leveler is controlled so that the difference from the distance average value becomes zero.

[0010]

In the shape measurement according to the present invention, a plurality of distance sensors 11 ₁ , 11 ₂ ... 11 _i are arranged along the width direction of a steel strip S as shown in FIG. Inside steel strip S
From the distance to the distance sensors 11 _1, 11 ₂ ··· 11 _i to continuous measurement. If the steel strip S has a wave shape, the distances detected by the distance sensors 11 ₁ , 11 ₂ ... 11 _i are represented by a period T according to the equation (1), where λ is a wave pitch and v is a line speed. fluctuate. T = λ / v (1) Specifically, assuming the ear extension at the end of the steel strip S,
The distance from the running steel strip S to each of the distance sensors 11 ₁ , 11 ₂ ... 11 _i varies in a pattern as shown in FIG. Here, when the time change of the distance is performed by the fast Fourier transform by the analysis device 12 at intervals longer than the time during which the wave passes for one cycle, as shown in FIG. 7, the wave shape is located at a frequency position corresponding to the wave pitch of the wave shape. An intensity peak corresponding to the wave height is obtained.

In the fast Fourier transform, the temporal change of the distance between the steel strip S and the distance sensor 11 during the passing of the steel strip S is converted into the relationship between the frequency representing the degree of the distance variation and the frequency representing the time variation. . The peak after fast Fourier transform increases as the wave height indicating the distance variation increases, and the frequency of the peak after fast Fourier transform increases when the pitch indicating the time variation decreases.

The peak frequency f is expressed by equation (2). f = 1 / T (2) When the shape of the steel strip S fluctuates in a short span in the longitudinal direction, the peak becomes gentle. When the measurement distance fluctuates due to the flapping of the steel strip S, if the fluctuation is periodic, a peak exists at a frequency position corresponding to the fluctuation. Since the frequency of the peak due to the periodic flapping is sufficiently higher than the frequency of the peak due to the wave shape, the peak can be easily identified. If the wave shape fluctuates for each wave in a range of, for example, ± 10% with respect to a reference wave pitch, the frequency of the peak subjected to fast Fourier transform for each wave is theoretically in a range of ± 11%. Change. As the wave height changes, the peak height also changes in proportion to the change in wave height. When fast Fourier transform is performed on all of several waves, the peaks have a distribution centered on a reference period, and the larger the fluctuation width of the wave shape, the larger the distribution of the peaks. Therefore, the reference wave shape and the variation of the shape in a short span can be known from the peak profile. The main disturbance is the fluttering of the plate generated under the influence of the mechanical vibration of the device. The frequency at this time is
Generally, it is in the range of several tens Hz to several hundred Hz. On the other hand, the wave pitch is generally in the range of 10 cm to 1 m. For example, when the board runs at a line speed of 60 m / min, the frequency due to the wave shape is about 10 Hz or less. From the difference in frequency, a disturbance peak and a wave-shaped peak can be identified.
Therefore, by performing the fast Fourier transform of the time change of the distance in the data of the time change of the distance, the influence of the disturbance can be easily grasped, and the influence of the disturbance can be easily eliminated.

[0013] In shape correction by a leveler, waves
The shape correction conditions are adjusted so that the peaks disappear. You
That is, in the tension leveler, the elongation rate control device 8 is used.
To control the elongation by the elongation roll 1a (FIG. 8).
In the roller leveler, the entrance side and the exit side are controlled by using the reduction amount controller 9.
The amount of reduction on the side is controlled (FIG. 9). Analysis device for control
Distance sensor 11 from steel strip S at 12₁ , 11_Two ... 11
_i The average distance at the center of the board width is averaged over time.
C warpage is calculated as the difference between the separation and the average distance at the edge of the plate width.
(See FIG. 6). Therefore, the tension leveler (Fig. 8)
In order to reduce the difference in average distance to zero,
The amount of reduction of the C warpage straightening roll 1b is controlled through the setting device 9.
You. Note that the tension leveler shown in FIG.
Although the regular roll is a roller leveler type,
Instead of the leveler type, a roll arrangement similar to that in Fig. 1 is also used.
It is possible. Whether to use the roller leveler type
The same applies to the long roll 1a and the C warp straightening roll 1b.
is there.

[0014]

EXAMPLE Five laser type distance sensors are arranged at equal intervals of 290 mm at the center of the plate width direction including the plate edge, and the wave width is 13 cm, the ear width is 1200 mm, and the plate thickness is 0.8 mm. Was passed through the steel strip at a line speed of 10 m / min, and the distance from the steel strip surface to the distance sensor was detected. The distance at the edge of the plate fluctuated at the cycle shown in FIG. 10 showing the measurement results. When the measurement result of FIG. 10 is subjected to the fast Fourier transform, as shown in FIG.
There was a peak at a frequency of 1.3 Hz corresponding to cm. Since the peak intensity corresponds to the wave height of the ear extension, it can be seen that the ear extension shape can be monitored based on the peak in FIG.

When the distances in FIG. 10 are averaged, 3
It was 9.5 mm. On the other hand, the average distance between the steel strip surface and the distance sensor detected by the distance sensor disposed at the center in the plate width direction was 39.0 mm. That is, it was found that the steel strip had a C warpage of 0.5 mm, which was a difference between the average distance of 39.5 mm at the end of the plate and the average distance of 39.0 mm at the center in the width direction of the plate. According to the wave shape and the C-warp obtained in this manner, the elongation rate is set so that the peak after the fast Fourier transform becomes zero in the line of FIG. 12 in which the tension leveler roll 1 and the roller levelers 5u and 5d are combined. The amount of reduction by the C warpage straightening roll 1b was controlled so that the difference between the average distance between the plate edge and the center in the plate width direction became zero.

The ear height and the amount of C warpage of the steel strip after shape correction were measured at the top, middle and end of the steel strip.
The measurement results are shown in FIGS. 13 and 14, respectively. In addition,
For comparison, the results of similarly measuring the ear height and the amount of C warpage for the steel strip whose shape was corrected under the conditions set only based on the distance from the steel strip surface to the distance sensor are shown in FIGS.
FIG. 4 shows a conventional method. As is clear from FIGS. 13 and 14, by controlling the elongation and the amount of reduction according to the present invention, the ear height and the C warpage after the shape correction were reduced. In addition, even in the steel strip whose shape was corrected, the fluctuation amount of the ear height and the C warpage was small.

[0017]

As described above, according to the present invention, the distance from the surface of the steel strip to the distance sensor is continuously measured, and the time change of the distance is determined based on the frequency peak obtained by the fast Fourier transform. Controls the elongation of the steel strip. When setting the shape correction conditions in this manner, shape fluctuations in short spans along the longitudinal direction and disturbances in measurement are eliminated, so that the shape correction conditions are set corresponding to the actual shape change, and L Warp, C warp, corrugation, etc. are suppressed, and a steel strip having a good shape is manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a typical tension leveler.

FIG. 2 is a schematic view of a typical roller leveler.

FIG. 3 shows a conventional tension leveler having a shape correction control mechanism.

FIG. 4 shows a conventional tension leveler having a shape correction control mechanism.

FIG. 5 shows a plurality of distance sensors arranged in the width direction of a steel strip according to the present invention.

FIG. 6 is a graph showing a time change of a distance from a running steel strip surface to a distance sensor.

FIG. 7 is a graph showing a result of a fast Fourier transform of a time change of a distance.

FIG. 8 is a schematic view of a tension leveler provided with a roller leveler type L warpage correcting roll.

FIG. 9 is a schematic view of a roller leveler in which a distance sensor for setting a shape correction condition is arranged on an output side.

FIG. 10 is a graph showing a temporal change in the distance from the steel strip surface to the distance sensor obtained in the example.

FIG. 11 is a graph showing a result of performing a fast Fourier transform on a time change of the same distance.

FIG. 12 is a schematic diagram of a shape control device used in the embodiment.

FIG. 13 is a graph comparing the change in ear height between the present invention and the conventional method.

FIG. 14 is a graph in which a change in the amount of C warpage is compared between the present invention and a conventional method.

[Explanation of symbols]

1: tension leveler roll 1a: elongation roll 1b: C warp straightening roll 1
c: L warp correction roll 2 _in: bridle roll (entering-side) 2 _out: bridle roll (exit side) 3: elongation zone 4: warp correction region 4 _1: the first unit 4 _2: second unit 5 _u: roller leveler Upper roll 5 _d : Lower roll 6 _in : Shape measuring device (entrance side) 6 _out : Shape measuring device (outside) 8: Elongation rate control device 9: Reduction amount control device 11 ₁ , 11 ₂ ... 11 _i ： Distance sensor 12 ： Analyzer S ： Steel strip T ： Period of distance fluctuation

Claims (2)

[Claims] 1. A continuous measurement of a distance from a running steel strip to each of the distance sensors by a plurality of distance sensors arranged along a sheet width direction, and a time required for a wave generated in the steel strip to pass for one cycle. A method for correcting the shape of a steel strip, comprising: performing a fast Fourier transform on a time change of a measured distance at the above intervals, and controlling an elongation rate of the steel strip so that an obtained frequency peak becomes zero. 2. The method according to claim 1, further comprising averaging distances measured by distance sensors disposed at a center portion and a plate end portion of the steel strip in the plate width direction, respectively, to calculate a distance average value at the plate end portion and a central portion in the plate width direction. The method for correcting the shape of a steel strip according to claim 1, wherein the amount of reduction of the leveler is controlled so that the difference from the distance average value in step (1) becomes zero.