JP2007118013A - Method for detecting edge overlapping flaw at tail end of steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting edge overlapping flaws at a tail end of a steel strip by which the edge overlapping flaws caused at the tail end of the steel strip in a rolling process can be detected and specified to prevent the steel strip from being broken in subsequent processes. <P>SOLUTION: The method for detecting the edge overlapping flaws at the tail end of the steel strip comprises: a vertical motion detecting step of detecting the vertical motion of a roll chock of a pinch roll to hold the steel strip and converting the vertical motion into the electric signal; an amplification step of amplifying the electric signal detecting the vertical motion; an edge overlapping flaw determination step of determining any abnormality of the amplified electric signal; and an alarm output step of informing the occurrence of an edge overlapping flaw by the result of determination. In the edge overlapping flaw determining step, the electric signal for each time corresponding to the actual vertical motion of the roll chock and the spectrum with the electric signal being subjected to the frequency analysis are combined with each other to determine the abnormality of the amplified electric signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for detecting edge folds at the tail end of a steel strip.

For example, in the pinch roll 3 before the winding of the downcoiler (DC) from the finish final stand of the hot rolling process of the steel strip 1 as shown in FIG. In order to prevent fluttering in the width direction of the steel strip 1 after being opened, a side guide 2 ′ is installed in front of the pinch roll 3 and in front of the inclined pinch roll 32.
The pinch roll 3 is installed in order to secure the tension of the steel strip in the inclined pinch roll 32 after the tail end of the steel strip has passed through the finishing final stand. Yes.
Further, since there is no tension on the pinch roll 3 side, there is a problem in that there is a high risk of occurrence of folding wrinkles.
That is, depending on the rolling operation situation, as shown in FIG. 3, the steel strip comes into contact with the side guide 2, whereby the edge of the side surface of the steel strip is folded and pinched by the pinch roll 3. Edge folds are generated in which the side surfaces partially overlap two or three. When this edge fold is generated, when cold rolling is performed in the lower process, there is a problem that a plate breakage occurs at the fold portion and a considerable damage is caused.
Conventionally, the detection of folds has been performed by the inspector after visual inspection of the end surface after winding the steel strip on the exit side of the line. Every several coils were sampled and rewinding inspection was performed in the lower process. However, since this inspection is only an inspection based on sampling, there is a case in which there is a case where a flaw is present in a coil other than sampling, and there is a problem that the possibility of overlooking cannot be eliminated.

Japanese Patent No. 3299351 (Patent Document 1) proposes a method in which a detecting means for detecting a load, a displacement, a pressure, and the like is provided on a roll, and a folding wrinkle generation position is detected by the detection signal.
However, the method described in Patent Document 1 above is a method for detecting the folding flaw occurrence position, and is not a method for accurately detecting the edge folding flaw at the tail end of the steel strip where the occurrence position has already been identified. It was.
In addition, all the wrinkle determination means of Patent Document 1 are determinations in the time domain, and only in the determination of the time domain, the signal noise and the steel strip shape are all mixed, and the overtest signal due to the pinch roll is mixed, There was a problem that edge folds could not be detected accurately.
Further, Japanese Patent No. 3605921 (Patent Document 2) proposes a method of detecting a folding flaw by providing at least three displacement meters in the steel strip rolling direction.
However, in the detection method described in Patent Document 2, since edge folds are generated at both ends of the edge, at least six displacement meters are actually required, and the number of detection means increases and the apparatus becomes complicated. There was a problem.
Japanese Patent No. 3299351 Japanese Patent No. 3605921

  The present invention eliminates the problems of the prior art as described above, detects edge folds occurring in the steel strip tail in the rolling process, identifies its occurrence, and prevents plate breakage in the lower process It is an object of the present invention to provide a method for detecting edge folds at the tail end of a steel strip.

The present invention has been made as a result of intensive studies in order to solve the above-mentioned problems, and the gist of the present invention is the following contents as described in the claims.
(1) A method for detecting edge folds at the tail end of a steel strip,
A vertical motion detection step of detecting the vertical motion of the roll chock of the pinch roll sandwiching the steel strip and converting it into an electrical signal;
An amplification step of amplifying the electrical signal that detects the vertical movement;
An edge folded wrinkle determination step for determining abnormality of the amplified electrical signal;
An alarm output step for notifying that an edge folding flaw has occurred according to the determination result,
In the edge folding wrinkle determination step, the abnormality of the amplified electric signal is determined by combining both the electric signal for each time corresponding to the actual vertical movement of the roll chock and the spectrum obtained by frequency analysis of the electric signal. A method for detecting edge folds at the tail end of a steel strip.
(2) In the edge folding wrinkle determination step, a threshold value is provided for an electrical signal for each time corresponding to the actual vertical movement of the roll chock, and when the threshold value is exceeded, a preset number of electrical signals are transmitted in real time. The edge folding at the tail end of the steel strip according to (1), characterized in that when the spectrum peak subjected to frequency analysis is lower than the natural frequency of the pinch roll and the spectrum peak exceeds a threshold value, it is determined as abnormal.疵 Detection method.
(3) In the edge folding wrinkle determination step, a threshold is set for an electric signal for each time corresponding to the actual vertical movement of the roll chock, and when the time exceeding the threshold becomes larger than a set value, or When a time integral value exceeding the threshold value becomes larger than a set value, a spectrum peak obtained by frequency analysis of a predetermined number of electrical signals in real time is lower than the natural frequency of the pinch roll, and the spectrum The method for detecting edge folds at the tail end of the steel strip according to (1), wherein an abnormality is determined when the peak exceeds a threshold value.

  According to the present invention, by combining both the electrical signal for each time corresponding to the actual vertical movement of the roll chock and the spectrum obtained by frequency analysis of the electrical signal, it is possible to reduce the number of edge folding defects as much as possible. It is possible to detect edge crease detection methods that can be detected and not missed, so it is possible to prevent the occurrence of sheet breakage during cold rolling in the lower process, and there are no additional processes such as sampling inspection, which are defective. There are significant industrially useful effects such as the prevention of shipment of different materials.

  The present invention is a method for detecting edge folding wrinkles at the tail end of a steel strip, wherein the vertical motion detection step of detecting the vertical motion of a roll chock of a pinch roll sandwiching the steel strip and converting it into an electrical signal, and the vertical motion An amplification step for amplifying the detected electrical signal, an edge folding wrinkle determination step for determining abnormality of the amplified electric signal, and an alarm output step for notifying that an edge folding wrinkle has occurred according to the determination result, The edge folded wrinkle determination step combines both the electric signal for each time corresponding to the actual vertical movement of the roll chock and the spectrum obtained by frequency analysis of the electric signal, and determines the abnormality of the amplified electric signal. It is characterized by.

FIG. 1 is a flowchart showing an embodiment of a method for detecting edge folds at the tail end of a steel strip in the present invention.
First, the vertical movement of the roll chock of the pinch roll that sandwiches the steel strip is detected and converted into an electrical signal (S-1).
By detecting the vertical movement of the roll chock of the pinch roll and determining this by the method described later, it is possible to detect the edge folded wrinkles.
In the present invention, any means for detecting the vertical movement of the roll chock is usable, but from the viewpoint of detection accuracy and versatility, a vibrometer or displacement meter using a contact-type piezoelectric element is preferable.
Next, it is made easier to determine by amplifying the electric signal that has detected the vertical movement (S-2).

Next, an abnormality of the amplified electric signal is determined by combining both the electric signal for each time corresponding to the actual vertical movement of the roll chock and the spectrum obtained by frequency analysis of the electric signal (S-3). .
In the conventional detection method, it was determined that a folding flaw occurred when the electrical signal for each hour corresponding to the actual vertical movement of the roll chock exceeded the threshold value. However, in the present invention, both the electrical signal for each time corresponding to the actual vertical movement of the roll chock and the spectrum obtained by frequency analysis of the electrical signal are combined. Then, since the abnormality of the amplified electric signal is determined, this overdetection can be remarkably reduced.
In the present invention, there is no limitation on the combined method of both the electric signal per time corresponding to the actual vertical movement of the roll chock and the spectrum obtained by frequency analysis of the electric signal, but one of the following two methods is used. It is preferable.

A first method is to provide a threshold value for an electric signal for each time corresponding to the actual vertical movement of the roll chock, and when the threshold value is exceeded, a spectrum peak obtained by performing frequency analysis on a predetermined number of electric signals in real time. Is lower than the natural frequency of the pinch roll, and when the spectrum peak exceeds a threshold value, it is determined to be abnormal.
As a result of conducting various investigations on the vibration of the pinch roll when the wrinkle is generated, the present inventors, as shown in FIG. 4 (a), the upper pinch roll 31 is in a state of supporting both ends during normal rolling. Although it vibrates at the natural frequency, as shown in FIG. 4 (b), when an edge folding wrinkle occurs, one end of the upper pinch roll 31 is lifted, and in a state close to cantilever support. It was found that the vibration frequency was lower than the natural frequency during normal rolling.
Therefore, a spectrum peak obtained by frequency analysis of a predetermined number of electrical signals in real time is lower than the natural frequency of the pinch roll (preferably 70 to 95% of the natural frequency), and the spectral peak exceeds a threshold value. It was found that the over-detection of edge folds was significantly reduced by determining that there was an abnormality.

In the second method, a threshold is provided for the electric signal for each time corresponding to the actual vertical movement of the roll chock, and the time when the time exceeding the threshold becomes larger than the set value or the time exceeding the threshold When the integral value becomes larger than the set value, the spectrum peak obtained by frequency analysis of the preset number of electrical signals in real time is lower than the natural frequency of the pinch roll, and the spectrum peak exceeds the threshold value. This is a method for determining that an abnormality has occurred.
In addition to setting a threshold for the electrical signal for each hour corresponding to the actual vertical movement of the roll chock, the time exceeding the threshold is greater than the set value, or the time integral value exceeding the threshold is set. Over-detection can be further reduced by making the condition that the value is larger than the above value.
If it is determined from the determination result that an edge folding flaw has occurred (Yes in FIG. 1), an alarm is output to notify the operator of the occurrence of a folding flaw (S-4).

FIG. 2 is a side view illustrating an embodiment of a method for detecting edge folds at the tail end of the steel strip according to the present invention.
In FIG. 2, when the tail end of the steel strip 1 passes through the finishing final stand, the tension applied so far is released and pulled to the pinch roll 3 side, and the steel strip 1 is attached to the side guide 2 in front of the pinch roll 3 according to the operating conditions. , A fold is generated and the pinch roll 3 sandwiches the fold so that an edge fold is generated. When this edge folding wrinkle occurs, the pinch roll 3 is lifted upward and a large vibration is generated. When the frequency is analyzed after the signal is amplified by the signal amplifying means 5, the specific frequency shifted downward from the natural vibration of the vertical vibration of the pinch roll. Spectral peaks occur. In other words, a threshold value is set for the vibration raw signal in the time domain, and the threshold value has a magnitude at which a spectrum peak appears at a frequency lower than the specific frequency corresponding to the natural frequency by the edge fold determination means 6. By determining whether or not the value exceeds the threshold value, edge folds are detected, and the occurrence is output to the alarm output means 7 to output an alarm.

In order to detect folding wrinkles, for example, a vibration meter or a displacement meter using a contact-type piezoelectric element is installed as the vertical motion detection means 4 and the folding wrinkles can be detected accurately only by detecting vibration abnormality data. I can't.
That is, noise and overdetection signals are mixed in the abnormal data, and it is necessary to determine the edge crease from them. For this purpose, as described above, abnormal vibrations need to be determined by frequency not only in the time domain but also in the frequency domain, and determined by the position (frequency) and magnitude of the spectrum peak in a specific frequency range. There is a need to.

The present invention is not the detection of folds in the longitudinal direction of rolling as in Patent Document 1 described above. That is, since the generation position is specified at the tail end of the steel strip, the position of the folding rod is not detected.
In addition, a vibrometer is provided to detect the folding flaw, but if you want to determine the vibration raw signal only in the time domain for the detection of the folding flaw, noise, steel strip shape disturbance, or pinch roll However, this problem is solved by combining the logic of analyzing the frequency of the vibration raw signal and determining the position and the size of the spectrum peak in the specific frequency region. In addition, by making the determination logic as described above, the number of vibrometer detectors can be reduced to two, the left and right (WS / DS) of the pinch roll, and a simple detection device can be realized.

FIG. 5 and FIG. 6 are diagrams showing an embodiment of the method for detecting an edge folding flaw at the tail end of the steel strip according to the present invention, FIG. 5 shows a case where there is no edge folding flaw, and FIG. .
FIG. 5B shows an electrical signal (analog signal of the vibrometer) representing the vertical movement (amplitude) of the roll chock at each time indicated on the horizontal axis on the vertical axis.
The amplitude peak exceeds Max, which is 3 V, and indicates Max 4.4 V.
FIG. 5 (a) shows the result of frequency analysis by taking 5000 points of data for 100ms from the time when the electrical signal representing the amplitude in FIG. 5 (b) first exceeds the threshold value of 3V, and is shown on the horizontal axis. The spectrum for each frequency is shown.
In FIG. 5 (a), since the spectrum peak is at a position of 700 Hz corresponding to the natural frequency of the roll chock, it indicates that no wrinkle has occurred.

FIG. 6B shows an electrical signal (an analog signal of a vibrometer) representing the vertical movement (amplitude) of the roll chock at each time indicated on the horizontal axis, and the amplitude peak exceeds 3 V as a threshold value. Max4V is shown.
FIG. 6A shows the result of frequency analysis of 5000 points of data taken for 100 ms from the time when the electric signal representing the amplitude in FIG. The spectrum for each frequency is shown.
In FIG. 6 (a), the spectrum peak is at a position of about 540 Hz lower than 700 Hz corresponding to the natural frequency of the roll chock, and the peak exceeds the threshold value of −15 dB. It shows that.
When the method for detecting edge folds at the tail end of the steel strip according to the present invention is applied to a hot rolling line of an actual steel strip, the edge folds are not overlooked, and the overdetection rate in conventional edge fold detection is 1. The effect of the present invention was confirmed from the fact that 6% could be reduced to 0.006%.

It is a flowchart which shows embodiment of the edge crease detection method of the steel strip tail end in this invention. It is a side view which illustrates embodiment of the edge fold detection method of the steel strip tail end in this invention. It is a top view which illustrates embodiment of the edge fold detection method of the steel strip tail end in this invention. It is a front view which illustrates embodiment of the edge fold detection method of the steel strip tail end in this invention. It is a figure which shows the Example of the edge folding flaw detection method of a steel strip tail end. It is a figure which shows the Example of the edge crease detection method of the steel strip tail end in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel strip 2, 2 'side guide 3 Pinch roll 31 Upper pinch roll 32 Inclined pinch roll 4 Vertical motion detection means 5 Signal amplification means 6 Edge folding wrinkle determination means 7 Alarm output means DC Downcoiler

Claims (3)

A method of detecting edge folds at the tail end of a steel strip,
A vertical motion detection step of detecting the vertical motion of the roll chock of the pinch roll sandwiching the steel strip and converting it into an electrical signal;
An amplification step of amplifying the electrical signal that detects the vertical movement;
An edge folded wrinkle determination step for determining abnormality of the amplified electrical signal;
An alarm output step for notifying that an edge folding flaw has occurred according to the determination result,
In the edge folding wrinkle determination step, the abnormality of the amplified electric signal is determined by combining both the electric signal for each time corresponding to the actual vertical movement of the roll chock and the spectrum obtained by frequency analysis of the electric signal. A method for detecting edge folds at the tail end of a steel strip.   In the edge folding wrinkle determination step, a threshold value is provided for an electrical signal for each time corresponding to the actual vertical movement of the roll chock, and when the threshold value is exceeded, the electrical signal of a preset number of points is subjected to frequency analysis in real time. 2. The edge fold detection method for a tail end of a steel strip according to claim 1, wherein a spectrum peak is determined to be abnormal when the spectrum peak is lower than the natural frequency of the pinch roll and the spectrum peak exceeds a threshold value. . In the edge folding wrinkle determination step, a threshold is provided for an electric signal for each time corresponding to the actual vertical movement of the roll chock, and the time when the time exceeding the threshold becomes larger than a set value or the threshold is set. When the exceeding time integral value becomes larger than the set value, the spectrum peak obtained by frequency analysis of the preset number of electrical signals in real time is lower than the natural frequency of the pinch roll, and the spectrum peak is a threshold value. 2. The method for detecting edge folds at the tail end of a steel strip according to claim 1, wherein an abnormality is determined when the value exceeds.

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