JP3272893B2 - Method and apparatus for calibrating sensitivity of steel strip defect detection device - 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 calibrating the sensitivity of a steel strip defect detecting apparatus which magnetizes a steel strip in a rolling direction and detects leakage magnetic flux generated by a defect inside or on the surface of the steel strip by using a large number of magneto-sensitive elements. And its device.

[0002]

2. Description of the Related Art Steel strip defects that detect surface defects such as pinholes and gouges generated in steel strips such as chrome-plated steel sheets and cold-rolled steel sheets and internal defects due to nonmetallic inclusions during running of the steel strips. Conventionally, various detection devices have been proposed. The magnetic sensing elements used in these steel strip defect detection devices include a Hall element, an SMD element, a sensing coil with a U-shaped core, a saturation magnetic flux type sensor utilizing the magnetic hysteresis effect of the core, and a flat coil on a thin printed circuit board. And the like are used. Since all of these magneto-sensitive elements cannot be used to inspect the entire width of the steel strip, a plurality of them are used in combination. It is necessary to set the sensitivity to a specified level while suppressing the fluctuation to a certain level. The specified sensitivity is set by processing an artificial contrast defect into the same material as the steel strip, or by preparing a steel strip with natural defects and detecting it under the same conditions as the actual inspection, and detecting the magneto-sensitive element. It is preferable to operate the amplification gain or attenuator so that the value falls within a specified range.

[0003] However, in order to perform such a sensitivity calibration, there are too many magnetically sensitive elements, and it is difficult to prepare a contrast defect or a natural defect. Therefore, an apparatus has been proposed which simply calibrates the detection sensitivity of a magneto-sensitive element based on a background noise signal of a healthy steel strip as a sensitivity calibration method with good reproducibility. (See, for example,
-95252). However, the background noise signal of the healthy steel strip detected by the magneto-sensitive element is the same as the surface roughness of the rolling roll, but the surface of the rolling roll gradually wears due to the rolling tonnage, and the beginning of the rolling unit starts. It is common sense to change at the end. For this reason, performing the sensitivity calibration based on the background noise signal of the steel strip whose surface roughness changes has a problem of a decrease in accuracy. Further, when the steel strip passed through is not always continuous in a time-series manner as in a refinery line, the background noise signal of the steel strip passed immediately before may have a different level from the background noise signal. There was a problem in securing the ratio.

A method and apparatus for generating a pseudo leakage magnetic flux by wrapping a wire near a magneto-sensitive element has been proposed. (For example, JP-A-5-10962). However, since the intensity of the magnetic flux generated by the inverse square of the distance between the magneto-sensitive element and the wire changes according to Ampere's law, strict dimensional accuracy is required, but it has been difficult to secure dimensional accuracy during winding. Therefore, it is conceivable to stabilize the pseudo leakage magnetic flux by wrapping the wire at a position far away from the magneto-sensitive element. If there is a difference between them, there is a problem that the path of the leakage magnetic flux passing through the magneto-sensitive element and the like are so different that accurate sensitivity calibration cannot be performed.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a method and a device for calibrating the sensitivity of a steel strip defect detecting device capable of easily performing high-accuracy sensitivity calibration. Is to do.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an electromagnet for a steel strip defect detecting device at a constant speed, wherein a standard test object provided with a thin wire over a steel strip width for generating a constant pseudo-leakage magnetic flux in a non-magnetic material made of a rigid body is provided. Through the magnetic flux of the standard inspection body, a constant pseudo-leakage magnetic flux generated by the standard specimen is detected by a large number of magnetic sensing elements of the steel strip defect detecting device disposed over the steel strip width, and is detected by each magnetic sensing element. A method of calibrating the sensitivity of the steel strip defect detection device, comprising comparing the detected value with a calibration device and calibrating the sensitivity variation of each magneto-sensitive element, an electromagnet of the steel strip defect detection device, and a non-magnetic material made of a rigid body. A fine wire for generating a constant pseudo-leakage magnetic flux is provided over the width of the steel strip, and a standard test object passing at a constant speed in the magnetic flux generated by the electromagnet; Calibrates the sensitivity variation of each magneto-sensitive element by comparing a large number of magneto-sensitive elements of the steel strip defect detecting device arranged over the steel strip width for detecting the leakage magnetic flux and the detection values detected by each of the magneto-sensitive elements. And a sensitivity calibration device for the steel strip defect detection device.

[0007]

The sensitivity calibration method and apparatus for a steel strip defect detecting device according to the present invention are provided at a constant speed with a steel strip width standard test object in which a thin wire for generating a constant pseudo-leakage magnetic flux is provided on a non-magnetic material made of a rigid body. If it passes through the magnetic flux, the thin wire, which is provided on the rigid non-magnetic material and generates pseudo-leakage magnetic flux, changes the magnetic flux without deforming due to the attractive force of the magnetic flux, and generates a constant pseudo-leakage magnetic flux. This pseudo leakage magnetic flux is detected by a number of magneto-sensitive elements arranged over the entire width of the steel strip. The detected values will be different. The dispersion of the detected values is corrected by the calibration device to correct the sensitivity of the magneto-sensitive element to a specified level.

[0008]

Next, the present invention will be described in detail with reference to the illustrated embodiment. Reference numeral 1 denotes a bridle roll around which a steel strip is wound. An electromagnet 2 for DC-magnetizing a steel strip passing through the bridle roll 1 in a rolling direction is disposed slightly above the bridle roll 1. Reference numeral 3 denotes a number of magneto-sensitive elements disposed between the two poles of the electromagnet 2, and the magneto-sensitive elements 3
A magnetic flux change, that is, a leakage magnetic flux, which is generated when a surface defect such as a pinhole or a gouge or a defect such as an internal nonmetallic inclusion is present in a steel strip magnetized by direct current. Reference numeral 4 denotes a standard test object that is interposed in the magnetic flux of the electromagnet 2 when performing sensitivity calibration. The standard test object 4 is attached to a roll 5 of a nonmagnetic material made of a rigid SUS316 body having a diameter of 56 × 1200 mm and an axial line. In which a thin wire such as a piano steel wire 7 made of a ferromagnetic material having a diameter of 0.2 mm is stretched and buried with a synthetic resin 8 made of a non-magnetic material. And piano steel wire 7 by synthetic resin 8
, The piano steel wire 7 is integrated with the roll 5, preventing rust and preventing the central portion of the piano steel wire 7 from being lifted by the magnetic force of the electromagnet 2.

Reference numeral 9 denotes a calibration device to which an electric signal of a constant pseudo-leakage magnetic flux from the standard test object 4 detected by the magnetic sensing element 3 is input. As shown in the block diagram of FIG. The electric signal of the constant pseudo-leakage magnetic flux detected by each magneto-sensitive element 3 is reduced to about 60 by the wide-area amplifier 10 arranged near the magneto-sensitive element 3 in order to ensure noise immunity.
The more decibels are amplified. Then, only the predetermined frequency band of the amplified electric signal of the pseudo leakage magnetic flux is amplified by the variable band / variable amplifier 11. After that, the signals of the large number of pre-wide-area amplifiers 10 are collected by the detection / A / D converter 12 for each detection end block, and the two shake signals are detected as one-sided shake signals. The peak value within the circumference is A / D converted and input to the sub data processing unit 13 arranged for each detection end block. Since the sub-data processing unit 13 collects signals for each detection end block by the detection / A / D converter 12, only the variable band / variable amplifier 11 directly connected to the magnetic sensing element 3 of interest has a pseudo-leakage magnetic flux with a predetermined sensitivity. Is detected, and the variable band / variable amplifier 11 directly connected to the other magneto-sensitive element 3 controls the sensitivity so that the output of the magneto-sensitive element 3 is taken into the sub-data processing unit 13 as if one channel at a time.

The sub-data processing section 13 takes in the pseudo leakage magnetic flux a predetermined number of times and calculates an average value. The result is sent to the upper-level main data processing unit 14, and is judged from the sensitivity calibration data stored in the memory 15 in advance and the sheet width, sheet thickness, inspection conditions, and the like input for each production lot. A gain correction value of the amplifier and the like are calculated for each magnetic element 3. This result is immediately returned to the sub data processing unit 13. The sub-data processing unit 13 adjusts the gain of the variable band / variable amplifier 11 based on these data. The magneto-sensitive element 3 has 144 channels in total and is divided into nine detection end blocks. The sub-data processing section 13 controls the 16-channel magneto-sensitive element 3, and the main data processing section 14 has 9 sub-data processing sections. The unit 13 is controlled. And 9
The central processing unit 16 includes the sub data processing units 13 and the main data processing unit 14. 17, a monitor CRT; and 18, a printer.

Hereinafter, the operation of the sensitivity calibration device for the steel strip defect detection device will be described. As shown in FIG. 6, the steel strip defect detection device is configured to perform direct current magnetization of a steel strip wound around a bridle roll 1 by an electromagnet 2 and detect a leakage magnetic flux due to a surface flaw of the steel strip by a magneto-sensitive element 3. However, when performing sensitivity calibration before and after the inspection and after a certain period of time, as shown in the flow of FIG. 4, the steel strip defect detection device is temporarily stopped to generate a certain pseudo leakage magnetic flux in the non-magnetic material. A roll 5 made of a non-magnetic material made of a rigid body of the standard test body 4 and provided over the width of the steel strip is disposed immediately below the detection unit of the steel strip defect detection device, and the roll 5 is rotated at a constant peripheral speed. (This peripheral speed may be the same speed as the passing speed or a different peripheral speed, but if the peripheral speed is different from the passing speed, the detected value needs to be corrected.) When the roll 5 rotates, the electromagnet 2 causes a direct current. A magnetic field is applied under the same conditions as during the actual inspection. (If the magnetizing current at this time is different from that at the time of the actual inspection, it is necessary to correct the detected value.) When the standard inspection object 4 passes through this magnetic flux, it moves in the axial direction of the roll 5 of a non-magnetic material made of a rigid body. With the piano steel wire 7 made of a ferromagnetic material integrated with the roll 5 buried with a non-magnetic material in the formed groove 6, the magnetic flux coming out of the iron core of the electromagnet 2 will pass through a path having a small magnetic resistance. Bend as The bent magnetic flux is detected by the magneto-sensitive element 3 as a constant pseudo-leakage magnetic flux.

The constant pseudo-leakage magnetic flux detected by each magneto-sensitive element 3 is amplified as an electric signal via the front wide-band amplifier 10 and the variable band / variable amplifier 11 of the calibrator 9 to detect and detect the A / D. A / D detected by the converter 12
After being converted, they are taken into a central processing unit 16 as a sub data processing unit 13 and a main data processing unit 14. At this time, the accuracy can be improved by measuring the detection value from each magnetic sensing element 3 many times and calculating the average value. Then, prior to the sensitivity calibration, the central processing unit 16 reads the set sensitivity calibration data, for example, the sheet passing material such as the sheet width and the sheet pressure and the inspection conditions such as the sheet passing speed and the detection sensitivity. The sensitivity correction amount of each magneto-sensitive element 3 is calculated by comparing the detection value of each magneto-sensitive element 3 with the data for sensitivity calibration. Based on the calculation result, the variable band / variable amplifier 11 corresponding to each magnetic sensing element 3
Is adjusted by a command from the central processing unit 16. After that, the detection values of the respective magneto-sensitive elements 3 are taken into the central processing unit 16 again, and it is confirmed whether or not the values converge to the prescribed values. If they do not converge, the same operation as described above may be repeated until they converge.

FIG. 5 (a, b) shows an iron roll (56 × diameter).
When a contrast defect having a diameter of 0.2 mm is formed in the width direction of the surface and the leakage magnetic flux is detected by the magneto-sensitive element,
Defect signals appearing at the edge and the center and a width of 0.3 in the width direction on the surface of a SUS roll (diameter 56 x width 1200 mm)
When a groove of 0.2 mm is formed and a piano steel wire as a comparative defect having a diameter of 0.2 mm is buried in a non-magnetic material and a leakage magnetic flux is detected by a magneto-sensitive element, a defect signal appears at an edge portion and a central portion. . From the two defect signals, the central part of the iron roll is attracted and lifted by the magnetic force, and the central part has a higher sensitivity than the edge part.
Because the roll made by the magnet is not attracted by the magnetic force and is not lifted, the piano steel wire affected by the magnetic force is thin and embedded with a non-magnetic material and integrated with the SUS roll,
Since there is no lift due to suction, the sensitivity is the same at the edge portion and the central portion, which indicates that the sensitivity is suitable for sensitivity calibration.

The roll 5 is provided with two concave grooves 6 or 4 concave grooves.
Form this and embed a dummy non-magnetic wire to achieve dynamic balance, embed a ferromagnetic thin wire with the same wire diameter or a slightly different wire diameter and perform sensitivity calibration with the average value of several signals, Needless to say, sensitivity calibration may be performed by a signal. In this embodiment, the standard test body 4 rotates a piano steel wire 7 embedded in a concave groove 6 of a non-magnetic stainless steel roll 5 made of a rigid body to generate a constant pseudo leakage magnetic flux. An amorphous ribbon may be attached to the surface of a roll 5 made of a non-magnetic material made of a rigid body. Alternatively, instead of the roll 5, a groove may be formed in a plate made of a non-magnetic material made of a rigid body. Of course, a ferromagnetic thin wire may be embedded with a synthetic resin of a non-magnetic material, or an amorphous ribbon attached to the surface of a rigid body may be linearly moved to generate a constant pseudo-leakage magnetic flux. is there. Further, it goes without saying that the electromagnet 2 may be provided in the bridle roll 1.

[0015]

As is apparent from the above description, the present invention provides a standard test object in which a thin wire for generating a constant pseudo-leakage magnetic flux is formed in a rigid nonmagnetic material over the width of a steel strip. Since a constant pseudo-leakage magnetic flux can be generated directly under the element, high-precision sensitivity calibration can be performed under the same conditions as in the actual inspection without being affected by the directivity of the magneto-sensitive element. In addition, there is no need to prepare a steel strip having uniform natural defects and contrast defects, and the fine wire made of ferromagnetic material that generates a certain pseudo-leakage magnetic flux of the standard test object is embedded in a non-magnetic material made of rigid material. Because it does not generate rust or wear, and it is not deformed by being attracted by magnetic flux, it is necessary to perform stable calibration over a long period without fluctuation or fluctuation of pseudo leakage magnetic flux. If the fine wire that generates a certain pseudo-leakage magnetic flux of the standard test object is made of amorphous material, there is no need to worry about corrosion or abrasion. There is no need to bury the material, and the manufacturing cost can be reduced. Accordingly, the present invention greatly contributes to the development of the industry as a method for calibrating the sensitivity of a steel strip defect detecting apparatus which solves the conventional problems and the apparatus therefor.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view showing an embodiment of the standard test object of the present invention.

FIG. 3 is a block diagram of the calibration device of the present invention.

FIG. 4 is a flowchart of an embodiment of the present invention.

FIG. 5 shows a case where a contrast defect is formed on an iron roll and SUS.
It is a waveform diagram which shows the pseudo leakage magnetic flux which appears at the edge part and central part at the time of embedding a piano steel wire in a roll made.

FIG. 6 is a schematic diagram illustrating detection of a defect in a steel strip.

[Explanation of symbols]

 2 Electromagnet 3 Magnetic sensing element 4 Standard test object 5 Roll 6 Groove 7 Ferromagnetic wire 9 Calibration device

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Toshiyuki Matsumine 81-81 Kitahiro, Tomishima-cho, Tokai City, Aichi Prefecture Taihei Kogyo Co., Ltd. (56) References JP-A-63-311165 (JP, A) JP-A-61-215959 (JP, A) JP-A-58-129361 (JP, A) JP-A-58-55752 (JP, A) JP-A-6-281625 (JP, A) JP-A-52-50787 (JP, U) JP-A-56-135157 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB G01N 27/72-27/90

Claims (6)

(57) [Claims] 1. A standard test object provided with a thin wire for generating a constant pseudo-leakage magnetic flux in a non-magnetic material made of a rigid body over the width of a steel strip is passed at a constant speed through the magnetic flux of an electromagnet of a steel strip defect detecting device. A constant pseudo-leakage magnetic flux generated by the standard test object is detected by a large number of magneto-sensitive elements of the steel strip defect detecting device arranged over the width of the steel strip, and the detection values detected by each magnetic sensitive element are compared by a calibration device. A sensitivity variation method for a steel strip defect detecting device, wherein the sensitivity variation of each magneto-sensitive element is calibrated. 2. An electromagnet of a steel strip defect detecting device and a fine wire for generating a certain pseudo-leakage magnetic flux in a non-magnetic material made of a rigid body are provided over the width of the steel strip, and pass through the magnetic flux generated by the electromagnet at a constant speed. A number of magnetic sensing elements of a standard inspection object, a steel strip defect detection device disposed over a steel strip width for detecting a constant pseudo-leakage magnetic flux generated by passage of the standard inspection object in magnetic flux, and each of the magnetic sensing elements And a calibration device for comparing sensitivity values of the respective magneto-sensitive elements by comparing detection values detected by the above-described methods. 3. The sensitivity calibrating device for a steel strip defect detecting device according to claim 2, wherein the fine wire for generating a certain pseudo-leakage magnetic flux of the standard test object is a ferromagnetic material. 4. The sensitivity calibrating device for a steel strip defect detecting device according to claim 2, wherein the fine wire for generating a certain pseudo-leakage magnetic flux of the standard test object is an amorphous material. 5. The standard test object according to claim 2, comprising a roll of a non-magnetic material made of a rigid body and a ferromagnetic thin wire embedded in the groove formed in the axial direction of the roll with the non-magnetic material. Calibration device for steel strip defect detector. 6. The steel strip defect detecting device according to claim 2, wherein the standard test object is composed of a roll made of a non-magnetic material made of a rigid body and an amorphous thin strip attached in the axial direction of the roll. Sensitivity calibration device.