JP4396340B2 - Method for detecting defects in steel sheet in rolling line - Google Patents

Description

  The present invention relates to a method for detecting defects that occur when a rolled steel sheet, particularly a hot rolling line, guides and winds a rolled steel sheet to a coiler through a pinch roll and a side guide.

  In the hot rolling of the steel plate, after the rough slab is applied to the heated slab, as shown in FIG. 1, the finish rolling mill 1 performs finish rolling to finish the steel plate 2 having a predetermined thickness, and then the side guide. In general, it is guided to the coiler 5 through the pin 3 and the pinch roll 4 and wound up to be shipped or used for the next process as a coil.

  In this hot rolling line, in particular, in the process of winding up the steel sheet after finish rolling, the sheet passing speed of the steel sheet from the finish rolling mill 1 exit side to the coiler (mandrel) 5 is the same as that on the finish rolling mill 1 side. Although the operation is synchronized, this synchronization may be disturbed. In particular, at the tip and tail ends of the steel plate, the speed at which the finish rolling mill side passes is increased, and as a result, the tip and tail ends of the steel plate, as well as places where sagging has occurred, pass between the subsequent pinch rolls. As a result of being folded, so-called folding occurs. When the fold is generated, if it is wound as it is, it may cause a plate breakage in the next process or become a defective product, so it is necessary to cut it outside the hot rolling line. For that purpose, it is important to detect the occurrence of folding in advance.

Regarding the detection of this folding, Patent Document 1 proposes to detect the load, displacement, etc. in the roll to be passed and identify the folding position.
Japanese Patent No. 3299351

  It is possible to detect the occurrence of folding by the technique described in Patent Document 1. However, the steel plate defect generated in the process until the steel plate after finish rolling is wound is not limited to folding, and there are various other defects. In particular, a defect called a so-called ear loss is installed in combination with the pinch roll due to the floating of the steel sheet occurring immediately before the pinch roll (deviation from the steel plate pass line, deviation in the thickness direction of the steel sheet). This is a defect in which the side guide and the steel plate come into contact with each other, and the side edge of the steel plate is chipped.

  Such a defect is different from the generation mechanism of folding, and therefore it is difficult to detect even if the technique described in the above-mentioned Patent Document 1 is applied. However, there is a need to establish a method for distinguishing and detecting defects.

  In view of this, the present invention has an object to propose a method for detecting the occurrence of an ear loss separately from the occurrence of folding.

The gist configuration of the present invention is as follows.
1. When the rolled steel sheet is guided to the coiler through the pinch roll and the side guide and wound, the load and the oil column of the hydraulic cylinder are measured on the pinch roll through which the steel sheet is passing, and the oil column fluctuation of the hydraulic cylinder A method for detecting a defect in a steel sheet in a rolling line, characterized by detecting the occurrence of an ear loss when only a load change is detected.

2. When the rolled steel sheet is guided to the coiler via the pinch roll and side guide and wound up, the load and the hydraulic cylinder oil column are measured on the pinch roll through which the steel sheet is passing, and the load fluctuation and the hydraulic cylinder oil are measured. A method for detecting a defect in a steel sheet in a rolling line, characterized by detecting the occurrence of an ear loss and a crease when both column fluctuations are detected.

  According to the present invention, it is possible to distinguish between steel sheet defects occurring in the rolling line, and particularly to detect the occurrence of the ear notches separately from the occurrence of folding, so that the removal process according to the defects can be realized quickly. .

First, the mechanism of the occurrence of an ear loss in a steel plate will be described.
Now, in the steady state shown in FIG. 1, that is, in a state where the steel plate 2 is continuously passed from the finish rolling mill 1 to the coiler 5, the steel plate 2 has a rotational speed controlled to the finish rolling mill 1. Appropriate tension is applied by controlling the rotation of the coiler 5 with a current. At this time, the pinch roll 4 is synchronized with the sheet passing speed. It should be noted that one or more pairs of pinch rolls are sufficient, and although two pairs are illustrated in FIGS. 1 and 2, they are not particularly distinguished in the following description.

  Immediately before the tail end of the steel plate 2 comes out of the finish rolling mill 1 through this steady state, the tension in the steel plate 2 is changed from the control between the finish rolling mill 1 and the coiler 5 to the control between the pinch roll 4 and the coiler 5. The load is transferred. That is, in order to wind a steel plate around the coiler 5, a certain tension is required, and when the steel plate 2 comes off from the finish rolling mill 1, the necessary tension is lost, so that a new tension is applied. This load transfer is necessary.

  Here, for example, in the case where the gap indication value necessary for gap control between the upper and lower pinch rolls is wide and different from the actual gap and sufficient pressing force cannot be generated, when the steel plate comes off from the finishing mill, When the plate slips and the load transfer from the finish rolling mill 1 to the pinch roll 4 is not realized smoothly, the steel plate is removed from the sheet passing line between the finish rolling mill 1 and the coiler 5, particularly immediately before the pinch roll 4. A floating phenomenon occurs.

And when this steel plate has a large lift, as a result of strongly contacting the side guide 3, which normally separates the both sides of the through-plate line with the U-shaped guide facing each other,
The side edge of the steel plate 2 is missing. When the side edge of the steel plate 2 comes into contact with the side guide 3 in this way, the tension on the entry side of the pinch roll 4 downstream of the side guide 3 increases, and the load on the pinch roll 4 decreases. This decrease in load is difficult to detect because the steel sheet is under tension control, but can be detected by the method described later. Thereafter, when the contact between the side edge of the steel plate 2 and the side guide 3 is finished, the incoming tension of the pinch roll 4 is decreased, and the load on the pinch roll 4 is increased.

  Thus, by detecting an increase in the load on the pinch roll 4, it is possible to detect that the side edge of the steel plate 2 is in contact with the side guide 3, that is, the occurrence of an ear loss. In addition, since the occurrence of the ear loss is as described above, the oil column of the hydraulic cylinder, which will be described later, does not fluctuate. Therefore, when the load fluctuates in the state where there is no oil column fluctuation, the ear loss has occurred. It can be judged.

  Here, the load in the pinch roll 4 is detected by measuring the oil pressure on the head or rod side of the cylinder in the case of a load cell installed in the roll housing or a hydraulic cylinder.

  Further, it is desirable to determine that an ear loss has occurred when a threshold value is set for the detected load and the fluctuation range of the load exceeds this threshold value. Here, the threshold value may be an intermediate value obtained by taking the difference between the normal coil and the ear missing coil by recording the maximum load actual value of the rolled coil.

On the other hand, the defect of folding is
-When the tip of the steel plate passes between the finishing mill and the coiler, the tip of the plate breaks into two pieces due to the lift of the tip of the plate. And the finishing speed are temporarily asynchronous (finishing speed> coiler speed), and when the plate is lifted, there is a steady-state folding in which the pinch roll is bitten in a folded state. In any case, since the plate passes through the pinch roll in a state where it overlaps with two or three sheets, the fluctuation of the oil column can be observed.

  In this way, the occurrence of folding can be detected when a change is detected in the oil column of the hydraulic cylinder. Since the occurrence of folding is as described above, the load described above does not fluctuate. Therefore, if there is a fluctuation in the oil column of the hydraulic cylinder in the absence of load movement, it is assumed that folding has occurred. I can judge.

  Here, the oil column of the hydraulic cylinder in the pinch roll 4 is detected by a position sensor built in the cylinder.

  Further, it is desirable to determine that the folding has occurred when a threshold value is set for the detected oil column of the hydraulic cylinder and the fluctuation range of the oil column exceeds this threshold value. Here, the threshold value may be an intermediate value obtained by taking the difference between the normal coil and the folding coil by recording the maximum oil column fluctuation record value of the rolling coil.

  Since it is as mentioned above, as shown in FIG. 2, only the load fluctuation (increase) is detected by detecting both the load in the pinch roll 4 and the oil column of the hydraulic cylinder with the detecting device 6 and observing the fluctuation. In the case of, the missing ear can be detected, and in the case of oil column fluctuation and load fluctuation, folding can be detected.

  In addition, as the detection apparatus 6, a computer, a sequencer, etc. are used in combination as appropriate.

  In the hot rolling line shown in FIG. 2, the load on the pinch roll 4 is taken up when the tin plate finished to 2 mm thick is wound from the finish rolling mill 1 by the coiler 5 via the side guide 3 and the pinch roll 4. And the oil column of the hydraulic cylinder was detected. Each detection was performed by the following method.

  That is, the load was detected from the head side pressure and the rod side pressure of the hydraulic cylinder, and the oil column of the hydraulic cylinder was detected from a position sensor built in the cylinder.

Also, for the load, the battle value is 20 kN from the rolling record, and for the oil column of the hydraulic cylinder, the battle value is 0.8 mm deviation from the oil column before the pinch roll is bitten, and both have the battle value. When it exceeded, it was assumed that fluctuation occurred.
In all cases, fluctuation occurred when the threshold value was exceeded.

  FIG. 3 illustrates the detection measurement thus obtained over a period of one month of operation. This figure shows the result of distinguishing and determining the ear missing, folding, and the occurrence of ear missing and folding with each threshold as a boundary. In addition, the plot in the figure shows the maximum value in the rolled coil, ○, △, × shows the results of inspecting the appearance after rewinding the coil after rolling, ○ is no ear missing / folding, Δ indicates that there is only an ear loss, and × indicates that there is both an ear loss and a fold. By the way, since there were a lot of ○, some of the measurement results are shown. Thus, when a defect was detected on the entrance side of the coiler 4 with respect to the detection result of distinguishing the defect type, the accuracy was 99%.

It is a figure which shows the process of the finish rolling delivery side of a hot rolling line. It is a figure which shows the process of the finish rolling delivery side of the hot rolling line according to this invention. It is a figure which shows the detection result of the load in a pinch roll, and the oil column of a hydraulic cylinder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Finish rolling mill 2 Steel plate 3 Side guide 4 Pinch roll 5 Coiler 6 Detector

Claims (2)

  When the rolled steel sheet is guided to the coiler through the pinch roll and the side guide and wound, the load and the oil column of the hydraulic cylinder are measured on the pinch roll through which the steel sheet is passing, and the oil column fluctuation of the hydraulic cylinder A method for detecting a defect in a steel sheet in a rolling line, characterized by detecting the occurrence of an ear loss when only a load change is detected.   When the rolled steel sheet is guided to the coiler via the pinch roll and side guide and wound up, the load and the hydraulic cylinder oil column are measured on the pinch roll through which the steel sheet is passing, and the load fluctuation and the hydraulic cylinder oil are measured. A method for detecting a defect in a steel sheet in a rolling line, characterized by detecting the occurrence of an ear loss and fold-in when both column fluctuations are detected.

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