JP2022161315A - Method of detecting welded portion of steel strip, method of manufacturing steel strip, device for detecting welded portion of steel strip and equipment for manufacturing steel strip - Google Patents

Abstract

To provide a method of detecting a welded portion of a steel strip which makes tracking of the welded portion possible by appropriately detecting the welded portion by suppressing vertical vibrations of the steel strip without using a hole for tracking, a method of manufacturing a steel strip, a device for detecting a welded portion of a steel strip and equipment for manufacturing a steel strip.SOLUTION: A welded portion detecting method of a steel strip detects a welded portion W of the steel strip S formed by welding a preceding steel strip S1 and a following steel strip S2. A vibration width of the steel strip S in a vertical direction with respect to a transfer direction during transportation is suppressed into 20 mm or less, and the welded portion W is detected based on a magnetic flux density change produced on the steel strip S by actuating a high-frequency magnetic flux 24 generated by applying a high-frequency voltage onto the steel strip S.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a method for detecting a welded portion of a steel strip, a method for manufacturing a steel strip, a device for detecting a welded portion of a steel strip, and an apparatus for manufacturing a steel strip.

2. Description of the Related Art Conventionally, for example, Patent Document 1 discloses a device for tracking a steel strip obtained by welding a preceding steel strip and a succeeding steel strip running on a production line.

In the hole accuracy detection method of the steel plate hole detection device disclosed in Patent Document 1, the hole formed in the welded portion of the preceding steel strip and the following steel strip is used as a hole for steel plate tracking.

Further, conventionally, for example, a device disclosed in Patent Document 2 is known as a device for tracking a relay welded portion of an electric resistance welded steel pipe.

The method for detecting an electric resistance welded steel pipe relay weld described in Patent Document 2 forms a relay weld on the steel strip by welding the front end of the following steel strip to the rear end of the preceding steel strip running on the production line. Then, the steel strip is formed into a cylindrical shape, and the butted ends in the width direction are welded to form an electric resistance welded steel pipe.

In the method for detecting an electric resistance welded steel pipe joint weld described in Patent Document 2, a coil for applying a high-frequency voltage is arranged in proximity to an electric resistance welded steel pipe, and a vortex is generated in the electric resistance welded steel pipe by the high-frequency magnetic flux generated by the coil. The current is constantly measured, the measured value is compared with a certain threshold, and the relay position is determined based on the magnitude.

JP 2010-85213 A JP 2006-68759 A

However, the hole accuracy detection method of the steel plate hole detection device disclosed in Patent Document 1 and the detection method of the electric resistance welded steel pipe joint weld disclosed in Patent Document 2 have the following problems.
That is, in the case of the hole accuracy detection method of the steel plate hole detection device disclosed in Patent Document 1, the hole formed in the welded portion of the preceding steel strip and the following steel strip is used as a hole for steel plate tracking. Most of them are of the light emitting/receiving type, and hole detection errors often occur due to insufficient light intensity of the light emitter or contamination of the light receiver, and there are cases where tracking of the welded part cannot be performed.

In tracking by holes, work hardening of punched holes increases due to deterioration of the punch dies and punches that process the holes. I had a problem.
On the other hand, in the case of the method for detecting an electric resistance welded steel pipe relay weld described in Patent Document 2, since the welded portion is detected and tracked, there is no problem in forming tracking holes in the steel strip.

However, the detection method for the joint welds of electric resistance welded steel pipes disclosed in Patent Document 2 targets the joint welds of electric resistance welded steel pipes, and cannot easily detect welded joints of thin steel strips such as cold-rolled steel strips. . In the case of electric resistance welded steel pipes, the vertical vibration of the steel pipe during running is not much of a problem, but in the case of thin steel strips, the vertical vibration of the steel strip during running is large, and it is difficult to detect the welded part. It is difficult to apply the detection method of the joint weld of the electric resistance welded steel pipe shown in Document 2 to the detection of the weld of a thin steel strip such as a cold-rolled steel strip.

Accordingly, the present invention has been made in view of these conventional problems, and its object is to appropriately detect the weld by suppressing the vertical vibration of the steel strip without using a tracking hole. It is therefore an object of the present invention to provide a steel strip weld zone detection method, a steel strip manufacturing method, a steel strip weld zone detection apparatus, and a steel strip manufacturing facility that enable tracking of the weld zone.

A steel strip weld zone detection method according to an aspect of the present invention is a steel strip weld zone detection method for detecting a weld zone of a steel strip formed by welding a preceding steel strip and a succeeding steel strip. The magnetic flux generated in the steel strip by suppressing the vibration width of the steel strip in the direction perpendicular to the conveying direction in the steel strip to 20 mm or less and applying a high-frequency voltage to the steel strip by applying a high-frequency magnetic flux to the steel strip. The gist of the invention is to detect the welded portion based on a change in density.

Further, a steel strip manufacturing method according to another aspect of the present invention is summarized in that it includes a weld zone detection step of performing the steel strip weld zone detection method described above.

A steel strip weld zone detection device according to another aspect of the present invention is a steel strip weld zone detection device for detecting a weld zone of a steel strip formed by welding a preceding steel strip and a succeeding steel strip. a vibration suppressing device for suppressing vibration width of the steel strip in a direction perpendicular to the transport direction during transport; a voltage applying device for applying a high frequency magnetic flux generated by applying a high frequency voltage to the steel strip; A magnetic flux density change detecting device for detecting a change in magnetic flux density generated in the steel strip by applying a high frequency magnetic flux to the steel strip by the voltage applying device, and a magnetic flux density change detected by the magnetic flux density change detecting device. and a weld detector for detecting the weld.

Further, a steel strip manufacturing facility according to another aspect of the present invention is summarized in including the steel strip weld zone detection device described above.

According to the steel strip weld zone detection method, the steel strip manufacturing method, the steel strip weld zone detection device, and the steel strip manufacturing equipment according to the present invention, the vertical vibration of the steel strip can be detected without using a tracking hole. Proper detection of the weld by suppression allows tracking of the weld.

1 is a schematic configuration diagram of a cold rolling line provided with a steel strip weld zone detection device according to an embodiment of the present invention; FIG. 2 is a schematic configuration diagram of the weld detection device shown in FIG. 1; In the example, (A ) shows the change in voltage difference seen from the plane side of the steel strip S, and (B) shows the change in voltage difference at line 3B in (A). FIG. 4 is a diagram for explaining a welded portion between a leading steel strip and a trailing steel strip;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. Note that each drawing is schematic and may differ from the actual one. Moreover, the following embodiments are intended to exemplify devices and methods for embodying the technical idea of the present invention, and are not intended to limit the configurations to those described below. That is, the technical idea of the present invention can be modified in various ways within the technical scope described in the claims.

FIG. 1 shows a schematic configuration of a cold rolling line equipped with a steel strip weld zone detector according to an embodiment of the present invention. A cold rolling line 1 shown in FIG. 1 is a steel strip manufacturing facility according to an embodiment of the present invention. The front end S2a (see FIGS. 2 and 4) of the leading steel strip) S2 passes through the pinch roll 3 and the trailing end S1a (see FIGS. 2 and 4) of the preceding rolled material (preceding steel strip) S1 in the welding machine 4. ). The welded steel strip S passes through a bridle roll 6, an entry-side looper 7, a plurality of pass line rolls 8, etc., and is cold-rolled by a tandem rolling mill 9. The weld W (see FIGS. 2 and 4) is cut off. Then, each of the leading steel strip S1 and the trailing steel strip S2 is wound by the winder 12 . As shown in FIG. 4, the welded portion W between the leading steel strip S1 and the trailing steel strip S2 extends over substantially the entire width direction of the steel strip S formed by welding the leading steel strip S1 and the trailing steel strip S2. exist.

Here, during cold rolling in this cold rolling line 1, in order to track the welded portion W of the steel strip S, welding is performed in the vicinity of the bridle roll 6 and in the vicinity of one of the plurality of pass line rolls 8. A part detection device 20 is installed.

First, the weld detection device 20 installed in the vicinity of the bridle roll 6 will be described. Each weld detecting device 20 detects the weld W of the steel strip S by an eddy current flaw detection method. The installation interval in the steel strip width direction of the plurality of weld detection devices 20 is set to, for example, 20 mm to steel strip width-20 mm.

Each weld detection device 20 includes a bridle roll 6 as a vibration suppressing device that suppresses the vibration amplitude of the steel strip S in the direction perpendicular to the conveying direction (from left to right in FIG. 1) during conveying. there is The bridle roll 6 applies tension to the conveyed steel strip S, and when applying tension to the steel strip S, the vibration width of the steel strip S in the direction perpendicular to the conveying direction during conveyance is 5 mm or less ( (within 2.5 mm vertically around the pass line). If the vibration width of the steel strip S is larger than 20 mm, the steel strip S may come into contact with the voltage application device 21 and the magnetic flux density change detection device 22 of the weld detection device 20, which will be described later. Sometimes I can't do it properly.

In the conventional detection method for an electric resistance welded steel pipe joint weld described in Patent Document 2, the joint welded part of an electric resistance welded steel pipe is targeted for detection. Although this is not a problem, in the case of a thin steel strip such as a cold-rolled steel strip as in this embodiment, since the section modulus is small, there is a risk that the vertical vibration of the steel strip during running may increase. The bridle roll 6 suppresses the vibration width.

2, each weld detecting device 20 includes a voltage applying device 21 for applying a high frequency magnetic flux 24 to the steel strip S, which is generated by applying a high frequency voltage. The voltage applying device 21 includes an exciting coil 21a wound around the central iron core portion in the conveying direction of the E-shaped iron core 20a arranged along the conveying direction of the steel strip S, and a voltage applying section 21b for applying a high frequency voltage to the exciting coil 21a. and When a high frequency voltage is applied to the excitation coil 21a, the applied high frequency voltage generates a high frequency current in the excitation coil 21a, and the high frequency current generated in the excitation coil 21a generates a high frequency magnetic flux 24. The generated high-frequency magnetic flux 24 acts on the steel strip S, and an eddy current is generated in the steel strip S so as to cancel the high-frequency magnetic flux 24 . The eddy current value changes as the steel strip S approaches or separates from the excitation coil 21a (when the welded portion W passes, it approaches the excitation coil 21a). That is, the magnetic flux density generated in the steel strip S changes.

As shown in FIG. 2, each weld detecting device 20 detects a change in magnetic flux density generated in the steel strip S by applying a high-frequency magnetic flux 24 to the steel strip S by means of a voltage applying device 21. A device 22 is provided. A first detection coil 22a wound around the entrance-side iron core portion in the conveying direction of the E-shaped iron core 20a, a first voltage detector 22b for detecting the voltage of the current flowing through the first detecting coil 22a, and the conveying direction of the E-shaped iron core 20a. A second detection coil 22c wound around the output side iron core, a second voltage detection section 22d for detecting the voltage of the current flowing through the second detection coil 22c, a voltage detected by the first voltage detection section 22b and the second and a voltage difference calculator 22e for calculating a voltage difference from the voltage detected by the voltage detector 22d. The magnetic flux density change detection device 22 detects the magnetic flux density change occurring in the steel strip S, and detects the difference between the voltage of the current flowing through the first detection coil 22a and the voltage of the current flowing through the second detection coil 22c. there is

If the steel strip S does not have a portion different from the mother plate portion such as the welded portion W, the voltage at the first detection coil 22a and the voltage at the second detection coil 22c will be substantially equal (the phases will also be equal), and the voltage difference will be The voltage difference calculated by the calculator 22e is also substantially zero. On the other hand, when the welded portion W of the steel strip S passes under the welded portion detection device 20, the voltage at the first detection coil 22a and the voltage at the second detection coil 22c are different, and are calculated by the voltage difference calculator 22e. voltage difference increases. For example, FIG. 3 shows the voltage difference between the voltage at the first detection coil 22a and the voltage at the second detection coil 22c when the welded portion W of the steel strip S in the embodiment passes under the welded portion detection device 20. , and when the weld W passes under the first detection coil 22a, the voltage difference calculated by the voltage difference calculator 22e is a (V) on the positive side. Further, when the welded portion W passes under the second detection coil 22c, the voltage difference calculated by the voltage difference calculation section 22e is b (V) on the minus side.

Further, each weld detection device 20 includes a weld detector 23 that detects the weld W based on the magnetic flux density change detected by the magnetic flux density change detector 22 .

Specifically, when the magnetic flux density change detected by the magnetic flux density change detection device 22 exceeds a predetermined threshold, the weld detection unit 23 detects that the voltage difference calculated by the voltage difference calculation unit 22e exceeds the predetermined threshold. In this case, the welded portion W is identified as the detection target location. That is, the voltage difference calculated by the voltage difference calculator 22e when the detection target location passes under the first detection coil 22a and the voltage difference calculation when the detection target location passes under the second detection coil 22c If the difference from the voltage difference calculated at the portion 22e exceeds a predetermined threshold value, the welded portion W is set as the detection target portion. For example, in the example shown in FIG. 3, the voltage difference (+a (V)) calculated by the voltage difference calculator 22e when the welded portion W serving as the detection target portion passes under the first detection coil 22a, and the welding The difference (+a−(−b)=a+b(V)) from the voltage difference (−b(V)) calculated by the voltage difference calculating unit 22e when the portion W passes under the second detection coil 22c is It exceeds a predetermined threshold, and the detection target location is identified as the welded portion W. Note that this predetermined threshold value is the voltage difference calculated by the voltage difference calculator 22e when a portion of the steel strip S other than the welded portion W passes under the first detection coil 22a, It is set to the median value of the difference from the voltage difference calculated by the voltage difference calculator 22e when the part passes under the second detection coil 22c.

As a result, the welded portion W can be tracked by appropriately detecting the welded portion W by suppressing the vertical vibration of the steel strip S without using a tracking hole.

As described above, a plurality of the weld detection devices 20 are arranged along the width direction of the weld W, and the voltage application device 21 of each weld detection device 20 detects the voltage along the width direction of the weld W. High-frequency magnetic flux is applied to a plurality of locations, and the magnetic flux density change detectors 22 of the respective weld detection devices 20 detect the magnetic flux density changes occurring at each location of the steel strip S due to each high-frequency magnetic flux. The welded portion W is detected based on the magnetic flux density change generated at each location of the steel strip S by each high-frequency magnetic flux detected by the magnetic flux density change detection device 22 .

The plurality of welded portion detection devices 20 identify the welded portion W as the detection target portion when all changes in the magnetic flux density occurring at each portion of the steel strip S exceed a predetermined threshold value. That is, the weld detector 23 of each weld detector 20 is connected to another common weld detector (not shown), and all the weld detectors 23 of all the weld detectors 20 have detection target locations. The voltage difference calculated by the voltage difference calculation unit 22e when passing under the first detection coil 22a and the voltage difference calculation unit 22e when the detection target location passes under the second detection coil 22c. When the difference from the voltage difference exceeds a predetermined threshold value and the welded portion W is identified, another common welded portion detecting portion identifies the detected portion as the welded portion W.

As a result, a plurality of weld detection devices 20 are provided side by side along the width direction of the weld W, and only when the weld is detected as the weld W at the same time, the detection target location is the weld W. The possibility of erroneously detecting a surface defect other than W as a weld W when it passes under the weld detector 20 can be avoided. This makes it possible to distinguish between welds W and detection of surface defects. The voltage difference calculated by the voltage difference calculator 22e when the detection target location passes under the first detection coil 22a in the weld detection unit 23 of any of the weld detection devices 20, and the voltage difference calculated by the voltage difference calculation unit 22e when the detection target location is the second If the difference between the voltage difference calculated by the voltage difference calculation unit 22e when passing under the detection coil 22c does not exceed a predetermined threshold, another common weld detection unit detects that the detection target location is welded. It is judged that it is not part W.

Here, the voltage application device 21 and the magnetic flux density change detection device 22 of each weld detection device 20 are arranged to face the bridle roll 6 as a vibration suppression device with the steel strip S interposed therebetween.
The distance between the excitation coil 21a constituting the voltage applying device 21 of each weld detection device 20, the first detection coil 22a and the second detection coil 22c constituting the magnetic flux density change detection device 22, and the surface of the steel strip S ( lift-off) is preferably set to 5 to 100 mm.

Also, the intervals in the conveying direction of the steel strip S between the excitation coil 21a, the first detection coil 22a and the second detection coil 22c are the intervals between the excitation coil 21a and the first detection coil 22a and the intervals between the excitation coil 21a and the second detection coil 22c. is preferably set to 10 to 80 mm.

Although the weld detection unit 23 is provided for each weld detection device 20, one weld detection unit is provided for a plurality of weld detection devices 20, and the steel strip S is detected by this weld detection unit. It is also possible to specify that the detection target location is the welded portion W when all changes in the magnetic flux density occurring at each location exceed a predetermined threshold value.

Next, the weld detection device 20 installed in the vicinity of one of the plurality of pass line rolls 8, like the weld detection device 20 installed in the vicinity of the bridle roll 6, the width direction of the steel strip S That is, along the width direction of the welded portion W, a plurality of them are arranged side by side. The installation interval in the steel strip width direction of the plurality of weld detection devices 20 is set to, for example, 20 mm to steel strip width-50 mm.

The basic configuration of each weld detection device 20 is the same as the weld detection device 20 installed near the bridle roll 6, and suppresses the vibration width of the steel strip S in the direction perpendicular to the conveying direction during conveying. A pass line roll 8 as a vibration suppressing device, a voltage applying device 21 that applies a high frequency magnetic flux 24 generated by applying a high frequency voltage to the steel strip S, and a high frequency magnetic flux 24 applied to the steel strip S by the voltage applying device 21. A magnetic flux density change detection device 22 for detecting a change in magnetic flux density occurring in the steel strip S, and a weld detection unit 23 for detecting a weld W based on the magnetic flux density change detected by the magnetic flux density change detection device 22. and However, as shown in FIG. 1, the voltage application device 21 and the magnetic flux density change detection device 22 of each weld detection device 20 face one surface (upper surface) and the other surface (lower surface) of the weld W, respectively. It is different from the weld detection device 20 installed near the bridle roll 6 in that it is installed as a pair.

In this manner, a pair of the voltage application device 21 and the magnetic flux density change detection device 22 of each weld detection device 20 are installed on one surface and the other surface of the weld W so as to face each other. Compared with the case where the voltage application device 21 and the magnetic flux density change detection device 22 are installed only on one side, there is an advantage that it is possible to identify defects on the plate surface layer.

The pass line rolls 8 transport the steel strip S. When transporting the steel strip S, the vibration width of the steel strip S in the direction perpendicular to the transport direction during transport is 20 mm or less (up and down around the pass line within 10 mm). If the vibration width of the steel strip S is larger than 20 mm, the steel strip S may come into contact with the voltage application device 21 and the magnetic flux density change detection device 22 of the weld detection device 20, which will be described later. Sometimes I can't do it properly.

In addition, a weld detection unit 23 connected to a magnetic flux density change detection device 22 arranged to face one surface of the weld W and a magnetic flux density change detection device 22 arranged to face the other surface of the weld W The welding part detection part 23 connected to is configured by a common welding part detection part. Then, this common welded portion detection unit detects the voltage difference calculated by the voltage difference calculation unit 22e of the magnetic flux density change detection device 22 arranged to face one surface of the welded portion W, and the other surface of the welded portion W. When the voltage difference between the voltage difference calculated by the voltage difference calculation unit 22e of the magnetic flux density change detection device 22 and the voltage difference exceeds a predetermined threshold value, the detection target location is the welded portion W and Identify.

As a result, the welded portion W can be tracked by appropriately detecting the welded portion W by suppressing the vertical vibration of the steel strip S without using a tracking hole.

As described above, a plurality of the weld detection devices 20 are arranged along the width direction of the weld W, and the voltage application device 21 of each weld detection device 20 detects the voltage along the width direction of the weld W. The high-frequency magnetic flux 24 is applied to a plurality of locations, and the magnetic flux density change detector 22 detects the magnetic flux density variation generated at each location of the steel strip S by each high-frequency magnetic flux 24. The welded portion W is detected based on the change in magnetic flux density generated at each location of the steel strip S by each high-frequency magnetic flux 24 detected in .

Then, in the same way as the weld detection devices 20 installed near the bridle roll 6, the plurality of weld detection devices 20 detect when all changes in the magnetic flux density occurring at each location of the steel strip S exceed a predetermined threshold value. , that the detection target location is the welded portion W. That is, the aforementioned common weld detection unit of each weld detection device 20 is connected to another common weld detection unit (not shown), and all the common weld detection units of all the weld detection devices 20 When the detection target location is identified as the welded portion W, another common welded portion detection unit identifies the detection target location as the welded portion W.

As a result, a plurality of weld detection devices 20 are provided side by side along the width direction of the weld W, and only when the weld is detected as the weld W at the same time, the detection target location is the weld W. The possibility of erroneously detecting a surface defect other than W as a weld W when it passes under the weld detector 20 can be avoided.

Although a common weld detection unit composed of two weld detection units 23 is provided for each weld detection device 20 , one weld detection unit is provided for a plurality of weld detection devices 20 . may be provided, and the welded portion W may be specified as the detection target portion when all changes in the magnetic flux density occurring at each portion of the steel strip S exceed a predetermined threshold value.

Here, the position where the weld detection device 20 installed on the upstream side (the bridle roll 6 side) detected the weld W, and the position where the weld detection device 20 installed on the downstream side (the pass line roll 8 side) detected the weld. If the deviation between the weld W and the detected position is within a predetermined threshold value (within 10% of the coil length in the actual line), the position detected as the weld W by the weld detector 20 on the downstream side is "positive". , and the position of the welded portion W is corrected to the position detected by the welded portion detection device 20 on the downstream side.

On the other hand, if the difference between the position detected as the weld W by the weld detection device 20 on the upstream side and the position detected as the weld W by the weld detection device 20 on the downstream side exceeds a predetermined threshold value, the plate surface roughness There is a high possibility of detection failure due to a defect, and it is treated as if there is no weld W.

If one of the welded portion detection device 20 on the upstream side and the welded portion detection device 20 on the downstream side detects the welded portion W and the other detects the welded portion W, the above-described positional deviation may As in the case of exceeding the threshold value, there is a high possibility of detection failure due to plate surface defects, and the welded portion W is treated as non-existent.

Then, the cold rolling line 1 performs notching on the widthwise end of the welded portion W of the steel strip S detected by the welded portion detection device 20 installed near the bridle roll 6 and near the pass line roll 8. A notching device 5 is provided. A notching device 5 is installed between the welder 4 and the bridle roll 6 .

In the cold rolling line 1 configured in this way, when detecting the welded portion W of the steel strip S by the welded portion detection devices 20 installed in the vicinity of the bridle roll 6 and the pass line roll 8, respectively, In the weld detection step, the weld detection device 20 suppresses the vibration width of the steel strip S in the direction perpendicular to the conveying direction during conveyance to 20 mm or less, and suppresses the high-frequency magnetic flux generated by applying the high-frequency voltage. By acting on the steel strip S, the welded portion W is detected based on the change in magnetic flux density occurring in the steel strip S.

As a result, the welded portion W can be tracked by appropriately detecting the welded portion W by suppressing the vertical vibration of the steel strip S without using a tracking hole.

In addition, a plurality of weld detection devices 20 arranged along the width direction of the weld W are used to apply high-frequency magnetic fluxes 24 to a plurality of locations along the width direction of the weld W, and each high-frequency magnetic flux 24 detects the steel strip S. The welded portion W is detected based on the magnetic flux density change occurring at each location of the steel strip S, and when all the magnetic flux density changes occurring at each location of the steel strip S exceed a predetermined threshold value, it is determined that the detection target location is the welded portion W Identify.

As a result, only when a plurality of welded portion detection devices 20 detect the welded portion W at the same time, the detection target location is the welded portion W, so that the surface defects of the steel strip S other than the welded portion W are detected by the welded portion detection devices 20 . The possibility of falsely detecting that surface defect as a weld W when passing under the W can be avoided.

Then, in manufacturing the steel strip S, notching is performed on the widthwise end portion of the welded portion W of the steel strip S detected in the welded portion detection step (notching step).
As a result, the notching process performed on the welded portion W can be performed on the widthwise end portion of the welded portion W of the steel strip S that has been detected accurately.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications and improvements can be made.

For example, the magnetic flux density change detection device 22 detects the magnetic flux density change occurring in the steel strip S, and detects the difference between the voltage of the current flowing through the first detection coil 22a and the voltage of the current flowing through the second detection coil 22c. is doing. However, the magnetic flux density change detecting device 22 detects the magnetic flux density change occurring in the steel strip S, and detects the eddy current value occurring in the steel strip S by measuring the current value flowing through the detection coil. good too.

Further, even if the voltage flowing through the detection coil is detected as in the present embodiment, each weld detection device 20 winds the excitation coil 21a around the central core portion of the E-shaped core 20a in the conveying direction. It is not necessary to wind the first detection coil 22a around the iron core portion on the conveying direction entry side of the E-shaped iron core 20a and wind the second detection coil 22c around the iron core portion on the conveying direction exit side of the E-shaped iron core 20a.

Also, although the bridle rolls 6 and the pass line rolls 8 are used as the vibration suppressing device, other members may be used. In this case, the weld detection device 20 may be installed in the vicinity of the separate member instead of the vicinity of the bridle roll 6 and the passline roll 8 .

In addition, although a plurality of weld detection devices 20 are provided side by side along the width direction of the steel strip S, only one device may be provided instead of a plurality of devices.

In addition, in the present embodiment, the cold rolling line 1 is used as the steel strip manufacturing equipment, but the weld detection device 20 is provided in the steel strip manufacturing equipment to which welding is applied. It may be provided not only in the cold rolling line 1 but also in, for example, a hot rolling line.

In the cold rolling line 1 shown in FIG. 1 , the welded portion W of the steel strip S was detected by the welded portion detection device 20 installed near the bridle rolls 6 . A plurality (two pieces) of the weld detection devices 20 are installed at predetermined intervals (20 cm) along the width direction of the steel strip.

The excitation frequency of the voltage application device 21 in each weld detection device 20 was 16 kHz, and the excitation voltage was 2.5V. FIG. 3 shows the change in voltage difference between the voltage at the first detection coil and the voltage at the second detection coil when the welded portion of the steel strip in this embodiment passes under the welded portion detection device. there is

The distance between the excitation coil 21a constituting the voltage applying device 21 of each weld detection device 20, the first detection coil 22a and the second detection coil 22c constituting the magnetic flux density change detection device 22, and the surface of the steel strip S ( Lift-off) was measured from 15 mm to 100 mm, and it was confirmed that the weld W was detectable. The thickness of the steel strip S was measured at 0.5 mm to 10 mm, and the welded portion W could be detected.

1 Cold rolling line (manufacturing equipment for steel strips)
2 payoff reel 3 pinch roll 4 welding machine 5 notching device 6 bridle roll 7 entry side looper 8 pass line roll (vibration suppression device)
9 tandem rolling mill 10 pinch roll (vibration suppression device)
Reference Signs List 11 cutting machine 12 winding machine 20 weld detection device 20a E-shaped iron core 21 voltage application device 21a excitation coil 21b voltage application section 22 magnetic flux density change detection device 22a first detection coil 22b first voltage detection section 22c second detection coil 22d Second voltage detector 22e Voltage difference calculator 23 Welded portion detector 24 High-frequency magnetic flux S Steel strip S1 Leading steel strip S1a Tail end S2 Trailing steel strip S2a Tip W Welding

Claims (11)

A method for detecting a welded portion of a steel strip for detecting a welded portion of a steel strip formed by welding a preceding steel strip and a trailing steel strip, comprising:
The vibration width of the steel strip in the direction perpendicular to the conveying direction during transportation is suppressed to 20 mm or less, and a high-frequency magnetic flux generated by applying a high-frequency voltage is applied to the steel strip, thereby generating in the steel strip. A method for detecting a welded portion of a steel strip, comprising detecting the welded portion based on a change in magnetic flux density. A high-frequency magnetic flux is applied to a plurality of locations along the width direction of the welded portion, and the welded portion is detected based on a change in magnetic flux density generated at each location of the steel strip by each high-frequency magnetic flux. A method for detecting welds in the steel strip described. 3. The welded portion of the steel strip according to claim 2, wherein the detected portion is specified as the welded portion when all changes in magnetic flux density occurring at each portion of the steel strip exceed a predetermined threshold value. Detection method. A method for manufacturing a steel strip, comprising a weld detection step of performing the steel strip weld detection method according to any one of claims 1 to 3. 5. The method for manufacturing a steel strip according to claim 4, further comprising a notching step of performing notching on the width direction end portion of the welded portion of the steel strip detected in the welded portion detecting step. A steel strip welded portion detection device for detecting a welded portion of a steel strip formed by welding a preceding steel strip and a trailing steel strip,
a vibration suppressing device that suppresses the vibration width of the steel strip in the direction perpendicular to the transport direction during transport;
a voltage applying device that applies a high frequency magnetic flux generated by applying a high frequency voltage to the steel strip;
a magnetic flux density change detecting device for detecting a magnetic flux density change occurring in the steel strip by applying a high-frequency magnetic flux to the steel strip by the voltage applying device;
and a weld detection unit for detecting the weld based on the magnetic flux density change detected by the magnetic flux density change detection device. 7. The steel strip welded portion detection device according to claim 6, wherein the voltage application device and the magnetic flux density change detection device are arranged to face the vibration suppression device with the steel strip interposed therebetween. 7. The welding of steel strips according to claim 6, wherein at least one pair of the voltage applying device and the magnetic flux density change detecting device are installed facing each of the one surface and the other surface of the welded portion. Part detection device. The steel strip weld according to any one of claims 6 to 8, wherein a plurality of the voltage application device and the magnetic flux density change detection device are provided side by side along the width direction of the weld. detection device. A steel strip manufacturing facility comprising the steel strip weld zone detection device according to any one of claims 6 to 9. 11. The steel strip manufacturing facility according to claim 10, further comprising a notching device for performing notching on the width direction end portion of the welded portion of the steel strip detected by the steel strip welded portion detection device.

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