JP2647326B2 - Metal strip break detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting breakage of a metal strip, and more particularly to a method for detecting breakage of a metal strip suitable for application in continuous annealing equipment in which a metal strip is annealed at high speed.

[0002]

2. Description of the Related Art A break detecting method for detecting a break in a continuously processed metal strip includes the following methods. (1) A method for detecting a break in a metal strip based on a change in a current value of an electric motor that applies tension to the metal strip. (JP-A-60-122
22) and (2) a method of comparing the rotational speed of a roll with the moving speed of a metal strip to detect breakage of the metal strip (see JP-A-2-149689). However, a change in the current value of the electric motor and a change in the moving speed of the metal strip are caused not only by the breakage of the metal strip but also by the slip of the metal strip. Therefore, in the methods (1) and (2), the metal strip is not used. There is a problem in that the slip of the metal strip may be erroneously detected as a break of the metal strip.

There is also known a method of measuring the tension of a metal strip to obtain an actual tension value and detecting breakage of the metal strip. In this method, a lower limit tension set value is determined in advance, and the actual tension value is set to a predetermined value. If the value equal to or less than the lower limit tension set value continues for a predetermined set time, it is determined that the metal strip has broken.

[0004]

In the above-described conventional method for detecting breakage of a metal strip based on the lower limit tension set value,
There are the following problems. (1) Depending on the type of steel, the actual tension value may be low. Therefore, if the lower limit tension setting value is lowered, breakage cannot be detected due to a zero point shift of the tensiometer or the like. (2) When the lower limit tension setting value is increased, the detection is liable to be erroneously detected because it is easily affected by tension fluctuations other than breakage. (3) To solve the above problem (2), a method of adding a detection timer to remove the influence of tension fluctuations other than breakage can be considered. In this method, however, the actual tension value is kept lower for a predetermined time. The metal strip is considered to be broken only when the tension value is equal to or less than the set value, and the predetermined time is 2 to
Three seconds are required, and erroneous detection can be prevented, but detection of breakage is delayed.

The present invention has been made in view of the above circumstances, and has as its object to provide a metal strip breakage detection method for quickly and reliably detecting a metal strip breakage.

[0006]

According to a first aspect of the present invention, there is provided a metal strip breakage detecting method for detecting a breakage of a metal strip based on an actual tension value of the metal strip. (1)
The actual tension value is compared with a value obtained by multiplying a predetermined tension command value by a preset value. (2) When the actual tension value is equal to or less than the value obtained by multiplying the preset value, the range in which the actual tension value fluctuates is set to a predetermined value. (3) When the fluctuation width of the actual tension value is within the above-mentioned set width, the time in which the actual tension value fluctuates is compared with a predetermined set time. When the set time is continued within the set width, the metal strip is determined to be broken.

Here, the set time is preferably set to a time inversely proportional to the passing speed of the metal strip.

[0008]

According to the metal strip breakage detecting method of the present invention, when the actual tension value of the metal strip is equal to or less than the set magnification of the tension command value, it is recognized as "abnormal tension", and the fluctuation of the actual tension value is subsequently detected. It is determined whether the width is within the set width. If the fluctuation range of the actual tension value is within the set range, when this state is continued for the set time, it is recognized as 'no tension change' and then determined as 'break'. When the tension is temporarily reduced due to, it is not judged as 'break'. As a result, the break can be quickly and reliably detected without being affected by disturbance.

Here, since the tension is stabilized as the passing speed of the metal strip approaches the rated value, if the set time is set to a time inversely proportional to the passing speed, if the passing speed is low, The break can be reliably detected without being affected by the tension fluctuation that tends to occur when the threading speed is low.
When the passing speed is high, the rupture can be detected quickly, so that damage due to the rupture can be minimized. Further, the time for detecting a break can be shortened as necessary, and unnecessary detection time can be reduced.

[0010]

An embodiment of the present invention will be described with reference to the drawings. Here, a case where the method for detecting fracture of a metal strip of the present invention is applied to a continuous annealing process will be described. FIG.
FIG. 2 is a schematic configuration diagram showing a continuous annealing facility in which a continuous annealing process is performed. The metal strip 10 is rewound from the payoff reel 11, annealed in an annealing tank 12, and then sent to bridle rolls 14 a and 14 b on the right side of the drawing.
Further, it is transported to the next step (not shown). The tension of the metal strip 10 is generated between the payoff reel 11 and the bridle rolls 14a and 14b. The bridle rolls 14a and 14b are respectively connected to the power supply 1
It is rotated by electric motors 16a and 16b driven by 5a. The power supply device 15a is driven based on a difference between a speed command value input to the speed control device 17 via the signal line 17a and an actual speed value measured by the pulse generator 18.

The tension of the metal strip 10 is controlled by the number of revolutions of the pay-off reel 11, and an automatic tension controller 20 for controlling the number of revolutions is disposed on the exit side of the annealing tank 12. While the actual tension value measured by the tensiometer 19 is input via the signal line 20a, a tension command value is also input via the signal line 20b. The power supply 15b is moved based on the difference between the actual tension value and the tension command value input to the automatic tension controller 20, whereby the electric motor 16c is controlled and the tension of the metal strip 10 is kept constant. On the other hand, the actual tension value and the tension command value input to the automatic tension controller 20 are respectively equal to the signal lines 21a and 21a.
It is also input to the arithmetic processing unit 21 via 1b. The arithmetic processing unit 21 detects the breakage of the metal strip 10 by performing the calculation described below, and outputs a breakage detection signal via the signal line 21c. The output break detection signal is input to the speed control device 17 and the automatic tension control device 20, and the electric motors 16a, 16b, and 16c are stopped. Further, an alarm device that issues an alarm based on the output break detection signal may be provided.

Referring to FIGS. 2 and 3, arithmetic processing unit 21
The calculation performed in is described. FIG. 2 is a diagram illustrating a change state of the actual tension value when the metal strip is broken between the payoff reel 11 and the bridle rolls 14a and 14b. FIG. 3 is a flowchart showing the logic performed by the arithmetic processing unit 21 when the actual tension value changes.

This flow is executed when the power is turned on. First, in step S100, the actual tension value measured by the tensiometer 19 (see FIG. 1) is checked to determine whether the actual tension value is an abnormal value. Is the α of the predetermined tension command value A.
It is compared with a value of twice (α is preferably 0.7 to 0.3 as an empirical value). The actual tension value is α of the predetermined tension command value A.
If not, the process returns to the start and step S100 is repeated. If the actual tension value is not more than α times the predetermined tension command value A, it is determined that the tension is abnormal, and the process proceeds to step S110. Here, the width in which the actual tension value varies is compared with a predetermined set width Bkg. . Where B
The appropriate value is 1.2 to 2 times the amount of fluctuation during idle rotation of the roll attached to the tensiometer as an empirical value. Step S110
If it is determined that the variation width of the actual tension value is not within the predetermined set width B, the process returns to the start and proceeds to step S100.
Is executed. If it is determined that the fluctuation range of the actual tension value is within the predetermined set width B, it is determined that there is no change in the tension, and the process proceeds to step S120. It is compared with a predetermined set time T (T is suitably 0.5 to 2 seconds as an empirical value). If the change in the actual tension value does not continue for the predetermined set time T, the process returns to step S110. If the change in the actual tension value continues for a predetermined set time T, it is determined that the metal strip 10 (see FIG. 1) has broken, a break detection signal is output, and this flow ends. As described above, in the method for detecting breakage of a metal strip according to the present invention, the detection of breakage is determined in three steps, so that a favorable result without erroneous detection can be obtained.

Referring now to FIG. 4, the relationship between the above set time T (set time for recognition of break detection) and the passing speed (processing speed V) of the metal strip will be described. FIG. 4 shows that the set time T and the processing speed V are in an inversely proportional relationship, and the set time T and the processing speed V are shown as percentages to represent relative values. As described above, the tension is stabilized as the passing speed of the metal strip approaches the rated value, so the set time T is set to be inversely proportional to the processing speed V. As a result, the higher the processing speed is, the shorter the time required for detecting the break is not influenced by the influence of the tension control accuracy, and a favorable result that the damage at the time of the break can be minimized can be obtained.

In this embodiment, a set width for recognizing abnormal tension and no change in tension is shown as an example.
The present invention is not limited to this, and may be set according to the characteristics of the equipment.

[0016]

As described above, the method for detecting breakage of a metal strip according to the present invention detects breakage when the actual tension value is abnormal and when the change in tension has continued for a set time within a set width. As a result, reliable break detection can be performed. In addition, since the duration of the tension change is set in inverse proportion to the processing speed of the equipment, there is also an effect that breakage damage in a high-speed region can be minimized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of a continuous annealing facility in which a continuous annealing process to which the present invention is applied is performed.

FIG. 2 is a diagram illustrating a change state of an actual tension value when a metal strip breaks between a payoff reel and a bridle roll.

FIG. 3 is a flowchart showing a logic performed by the arithmetic processing unit when the actual tension value changes.

FIG. 4 is a graph showing a relationship between a set time T (break detection recognition set time) and a metal strip passing speed (processing speed V).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Metal strip 11 Payoff reel 12 Annealing treatment tank 14a, 14b Bridle roll 15a, 15b Power supply device 16a, 16b, 16c Electric motor 17 Speed control device 18 Pulse generator 19 Tensiometer 20 Tension control device 21 Arithmetic processing device

Claims (2)

(57) [Claims] 1. A method for detecting breakage of a metal strip based on an actual tension value of a metal strip, wherein the actual tension value is compared with a value obtained by multiplying a predetermined tension command value by a preset value. When the actual tension value is equal to or less than the set multiplied value, the width in which the actual tension value fluctuates is compared with a predetermined set width, and when the fluctuation width of the actual tension value is within the set width, Comparing the time during which the actual tension value fluctuates with a predetermined set time, and determining that the metal strip has broken when the fluctuation of the actual tension value has continued for the set time within the set width. A method for detecting breakage of a metal strip. 2. The method according to claim 1, wherein the set time is a time inversely proportional to a passing speed of the metal strip.