JPH11211698A - Method and apparatus for calibrating sensitivity of magnetic flaw detector and calibration roll - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To accurately calibrate all the elements arranged in the width direction of a flaw detector in an extremely short time and accurately. An object of the present invention is to provide a calibration method that enables long-term use of the same artificial calibration sample. A flaw detection device comprising a group of magnetically sensitive elements arranged side by side in the width direction of a thin steel strip to be inspected, wherein a magnetic field is generated in a running direction of the thin steel strip to be inspected, and a leakage magnetic flux generated due to an internal or surface defect is provided. In a method for calibrating the sensitivity of a magnetic flaw detector which detects an on-line position by a head and generates a defect signal, a calibration roll provided with a calibration magnetic generator capable of generating an output related to a defect to be inspected is provided at an off-line position, The flaw detection head is moved from the online position to the calibration roll position, and fixed at a predetermined lift-off so that the length direction of the flaw detection head and the axial direction of the calibration roll match, while rotating the calibration roll, Calibrate the sensitivity of each magnetic element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for calibrating the sensitivity of a magnetic flaw detector, and more particularly, to a magnetic flaw detector suitable for use in a magnetic flaw detector for detecting a traveling thin steel strip (strip) online. And a calibration roll.

[0002]

2. Description of the Related Art In order to detect a surface defect or an internal defect of a running thin steel strip, a magnetic field is generated in the running direction of the steel strip to be inspected, and a leakage magnetic flux generated by the internal or surface defect is detected. A magnetic flaw detector which detects a defect at an on-line position by using a flaw detection head having a plurality of magnetic sensitive elements arranged side by side in the width direction of the band and generates a defect signal is used. Such a flaw detector is disclosed in Japanese Utility Model Laid-Open No. 63-107849. Has a flaw detection head having a group of magnetically sensitive elements that detect magnetic flux arranged in a straight line, and a magnetic flaw detection device that continuously detects defects existing in the entire width of a thin steel strip traveling at a constant speed has been proposed. .

In the magnetic flaw detector, since a number of magnetic sensitive elements are arranged in parallel in the width direction of the thin steel strip to be inspected, the sensitivity of these magnetic sensitive elements must be adjusted prior to the inspection. As means for that purpose, conventionally,
As shown in Japanese Patent No. 27747, a standard defect sample having an artificial defect serving as a standard is placed on each magnetic sensitive element (also simply referred to as an element), and the sensitivity is calibrated one by one.

However, such a method naturally takes a long time and is troublesome, and as a means for solving this, as shown in Japanese Patent Application Laid-Open No. 3-134555, a pseudo leakage magnetic flux is externally generated. It has been proposed to eliminate the use of a standard defect sample by applying a uniform magnetic field to the entire flaw detection head. Further, as an improved technique, Japanese Patent Application Laid-Open No. 5-10926 discloses an excitation coil for calibration, which includes a flaw detection head and a magnetized magnet. It has been proposed to be wound around an iron core, disposed within the magnetized iron core, or disposed together with a second hollow roll at a position opposite to a thin steel plate.

[0005]

However, Japanese Patent Application Laid-Open No. 3-134555 or Japanese Patent Application Laid-Open No. 5-109
The means described in Japanese Patent Publication No. 26 is wide and calibrates only with a magnetic field from a certain direction. Therefore, it generates only an extremely small magnetic field from a certain direction like a defect of an actual inclusion defect. Calibration for detecting defects that do not occur cannot be performed sufficiently.

In order to solve the problem of the prior art, the present inventor has disclosed in Japanese Patent Application No. 9-265734 an off-line position of a calibration roll on which an artificial calibration sample capable of generating an output related to a defect to be detected is wound. Provided in
Means has been proposed for moving the flaw detection head from the online position onto the calibration roll, rotating the calibration roll in that state, and moving the flaw detection head in the axial direction to efficiently calibrate the flaw detection device. According to this proposal, it is possible to quickly calibrate all the elements across the width of the flaw detector, but since the calibration work must always use an artificial calibration sample, it is painful and has a long life. There was the problem of being short.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and it is possible to calibrate all elements arranged in the width direction of a flaw detector in an extremely short time and accurately. In particular, an object of the present invention is to enable long-term use of the same artificial calibration sample without always using the artificial calibration sample.

[0008]

According to the present invention, a magnetic field is generated in the running direction of a thin steel strip to be inspected, and a large number of leakage magnetic fluxes generated by internal or surface defects are arranged in parallel in the width direction of the thin steel strip to be inspected. A calibration roll equipped with a calibration magnetic generator capable of generating an output related to a defect to be detected in a method for calibrating the sensitivity of a magnetic inspection device that detects a defect signal at an online position by a flaw detection head having a group of magnetic sensitive elements. Is provided at the off-line position, the flaw detection head is moved from the on-line position to the calibration roll position, and fixed with a predetermined lift-off so that the length direction of the flaw detection head and the axial direction of the calibration roll coincide with each other. This problem is solved by calibrating the sensitivity of each magnetic element while rotating the roll.

The present invention also provides a magnetic sensitive element in which a magnetic field is generated in the running direction of a thin steel strip to be inspected, and a large number of leakage magnetic fluxes generated by internal or surface defects are arranged in parallel in the width direction of the thin steel strip to be inspected. A sensitivity calibration device for a magnetic inspection device that detects a defect signal online by using a flaw detection head provided with a group, a calibration roll having the calibration magnetic generator provided at an off-line position, and means for rotating the calibration roll. Means for moving the flaw detection head from the online position to the calibration roll position, and fixing the flaw detection head with a predetermined lift-off so that the length direction of the flaw detection head and the axial direction of the calibration roll coincide with each other; This problem has been solved by providing a means for calibrating the sensitivity.

Further, in the present invention, as a calibration roll suitable for the above-described method of calibrating a flaw detector, the calibration roll includes an excitation yoke and a calibration excitation coil for applying a calibration magnetic field to the excitation yoke.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. Magnetic flaw detector 1 according to one embodiment of the present invention
Reference numeral 00 denotes a magnetization yoke 10 as shown in FIGS.
Flaw detection head 1 including, for example, 1000 magnetically sensitive elements 111 linearly arranged in the width direction of the thin steel strip 10 to be inspected, and a magnetizer 102 including a magnetizing coil 4 and a magnetizing coil 106.
10 and a DC power supply 112 for supplying an exciting current to the magnetizing coil 106. Have been.

The sensitivity calibration device 120 according to the device of the present invention comprises:
As shown in FIGS. 1 and 2, a calibration roll 124 which is provided at an off-line position and has a built-in calibration magnetic generator 200 capable of generating an output related to a defect to be inspected, and the calibration roll 124 is indicated by an arrow in FIG. A calibration roll moving device 126 that moves in the axial direction while rotating in the direction D as shown by an arrow E in FIG.
Is moved together with the magnetic flaw detector 100 from the online position to the position of the calibration roll 124 as shown by arrows B and C so that the length direction of the flaw detection head 110 and the axial direction of the calibration roll 124 match. , A lifting device 150 and a moving device 152 for fixing with a predetermined lift-off, and a sensitivity calibration circuit that moves in the axial direction while rotating the calibration roll 124 to calibrate the sensitivity of each magnetic sensitive element 111. ing.

Here, the calibration roll 124 corresponds to FIG.
As shown in (a) and (b), a calibration magnetic generator 200 is incorporated. The calibration magnetic generator 200 includes a calibration excitation coil 201 and a calibration excitation yoke 202. A DC current is supplied to the calibration excitation coil 201 from a slip ring (not shown) to generate a calibration magnetic field. The excitation yoke 202 is excited.

The excitation yoke 202 for calibration includes the calibration roll 12
4, and a gap 203 corresponding to the length of the target defect is provided. Using a yoke 202 having a gap 203 corresponding to the length of the defect, the leakage magnetic flux matching the magnetomotive force to the defect, that is, 0.1 to 1
If the adjustment is performed in the range of 00 × 10 ⁻⁴ Wb / m ² , the same leakage magnetic flux as the target defect such as inclusions in the thin steel strip to be tested is generated. Similar calibration is possible. For this purpose, it is preferable that the depth 204 of the gap 203 and the yoke thickness 205 of the gap portion be 10 times or more the gap 203. For example, when the gap 203 is 0.1 mm, the depth of the gap 203 is 2 mm.
04 is 20 mm, and the thickness 205 of the portion is 10 mm.
And

In order to perform a calibration operation using the calibration roll 124 having the built-in calibration magnetic generator 200, the calibration roll 124 must be moved in the axial direction while rotating. Therefore, the calibration roll moving device 1
26, a motor 130 for rotating the calibration roll 124 via a belt 132 and a pulley 134, a bearing 138 for supporting the calibration roll 124, and a motor 13
0 is fixed to the movable base 140 and the movable base 14
It is configured to include a guide rail 136 for moving the zero in the axial direction of the calibration roll 124 and a fixed base 142 for fixing the guide rail 136.

A magnetic flaw detector 10 including the sensitivity calibration circuit
The circuit 0 is provided for each magnetic element 111, and includes a capacitor, an amplifier including an electronic volume for sensitivity calibration, a band-pass filter passing the output of the amplifier, and rectifying the output of the band-pass filter. It comprises a dual-wave rectifier, a buffer for passing the output of the dual-wave rectifier, an aggregate circuit for combining the outputs of a large number of magneto-sensitive elements via the buffer, and a comparator for comparing the output of the aggregate circuit.

In the above-described apparatus, in a normal online state, the magnetic flaw detector 100 is at the position shown by a solid line on the left side of FIG.
It is running in the direction of arrow A with 0 ° winding. A magnetized yoke 104 for introducing a magnetic flux into the thin steel strip 10 is disposed below the magnetic flaw detector 100 and at a position 0.5 mm above the thin steel strip 10, and a flaw detection including the magnetically sensitive element 111 is interposed therebetween. A head 110 is also provided. The magnetized yoke 1
During the flaw detection, the thin steel strip 10 is magnetized to about 1 kG in the running direction by the excitation of the DC current from the DC power supply 112 in the magnetizing coil 106 provided above the 04. The magnetizing current at this time is, for example, 0.81 A (600 ampere turn). The running speed of the thin steel strip 10 is, for example, 1200 m / mim at the maximum. When the detection of inclusions is unnecessary or when other inspection is unnecessary, the magnetic flaw detector 100 is moved by the elevating device 150 as shown by the arrow B,
It can be evacuated upward.

At the time of sensitivity calibration, first, the magnetic flaw detector 100 at the on-line position is lifted upward by the elevating device 150 as shown by the arrow B, and then off-line by the moving device 152 as shown by the arrow C. It moves to just above the sensitivity calibration device 120 at the position. The moving position of the magnetic flaw detector 100 can be set by, for example, a numerical value of a counter, and can be moved with an accuracy of ± several μm.

Next, the magnetic flaw detector 100 is lowered by the elevating device 150 so as to approach the calibration roll 124. The calibration roll 124 is located at the center of the flaw detection head 110, and is calibrated by the displacement roll sensor (not shown) in the magnetic flaw detection device 100 and the magnetic sensitive element 111.
Is adjusted to a set value, for example, 0.5 mm.

Next, as shown in FIG.
4 is moved in the axial direction as shown by arrow E, and the calibration roll is rotated to perform the calibration work. This calibration operation may be performed, for example, in order from the first element of the magnetic element group so that the sensitivity of each magnetic element becomes the same with respect to the target defect.

At this time, the magnetic flux leakage from the calibration yoke 202 during the calibration is from 0.1 × 10 ⁻⁴ Wb / m ² to 100 × 10
^The current value is adjusted so as to be variable up to ⁻⁴ Wb / m ² so as to match the leakage flux of a target defect, for example, a nonmetallic inclusion. This value can be determined by an experimental result using a standard calibration sample, for example, 1 × 10 ⁻³ mm ³
Fig. 3 (b) corresponds to the leakage magnetic flux of the inclusion having a volume of
In this case, a magnetic flux of about 1 × 10 ⁻⁴ Wb / m ² is generated at the point M in FIG. Since the value of the leakage magnetic flux varies depending on the material and the thickness of the target material, it may be determined individually.

After the automatic sensitivity calibration, the magnetic flaw detector 100 is returned to the online position by the elevating device 150.

In the above example, the calibration roll 124 having the built-in calibration magnetic generator 200 is connected to the flaw detection head 11.
The case where the width of the calibration roll is configured to be much narrower than the width of 0 and moved in the axial direction while rotating the calibration roll has been described. However, if the width of the calibration roll is equal to or larger than the flaw detection head, the calibration roll is moved in the axial direction. Calibration can be performed more quickly without the need for calibration.

[Brief description of the drawings]

FIG. 1 is a front view showing the entirety of a magnetic flaw detector and its sensitivity calibration device according to the present invention.

FIG. 2 is a side view of the sensitivity calibration device at an off-line position.

FIG. 3 shows a configuration of a calibration roll according to the present invention,
(A) is a perspective view of a calibration magnetic generator, and (b) is a side view.

FIG. 4 is a conceptual diagram showing a calibration process according to the present invention.

[Explanation of symbols]

 10: Thin steel strip 80: Non-magnetic roll 100: Magnetic flaw detector 102: Magnetizer 104: Magnetization yoke 106: Magnetization coil 110: Flaw detection head 111: Magnetic sensitive element 112: DC power supply 120: Sensitivity calibrator 124: Calibration roll 126 : Calibration roll moving device 136: Guide rail 140: Moving base 142: Fixed base 150: Elevating device 152: Moving device 200: Calibration magnet generator 201: Calibration excitation coil 202: Calibration excitation yoke 203: Gap 204: Gap depth 205: Gap yoke thickness

Claims (3)

[Claims] 1. A magnetic sensitive element group in which a magnetic field is generated in a running direction of a thin steel strip to be inspected and a leakage magnetic flux generated due to an internal or surface defect is provided in a large number in parallel in a width direction of the thin steel strip to be inspected. In the method of calibrating the sensitivity of a magnetic flaw detector which detects a defect signal online and generates a defect signal, a calibration roll having a calibration magnetic generator capable of generating an output related to a defect to be detected is provided at an off-line position. The head is moved from the on-line position to the calibration roll position, and fixed with a predetermined lift-off so that the length direction of the flaw detection head and the axial direction of the calibration roll coincide with each other. A method for calibrating the sensitivity of a magnetic flaw detector, comprising calibrating the sensitivity of a magnetic element. 2. A magnetic sensing element group in which a magnetic field is generated in a running direction of a thin steel strip to be inspected, and a plurality of magnetic flux-sensitive elements arranged in parallel in a width direction of the thin steel strip to be inspected to generate a leakage magnetic flux generated by an internal or surface defect. A sensitivity calibration device for a magnetic flaw detector which detects a defect signal online and generates a defect signal; a calibration roll having a calibration magnetic generator provided at an off-line position; a means for rotating the calibration roll; and the flaw detection head. Means for moving from the on-line position to the calibration roll position, means for fixing with a predetermined lift-off so that the length direction of the flaw detection head and the axial direction of the calibration roll coincide, and means for calibrating the sensitivity of each magnetically sensitive element And a sensitivity calibration device for a magnetic flaw detector. 3. A calibration roll comprising an excitation yoke and a calibration excitation coil for applying a calibration magnetic field to the excitation yoke.