JP3752807B2 - Surface defect detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for detecting a surface defect of, for example, a square billet, which is a material of various steel products.
[0002]
[Prior art]
As a method for inspecting a surface flaw of a metal material, for example, there is an electromagnetic inspection method such as a leakage magnetic flux inspection method or an eddy current inspection method. In the case of inspecting a material having a planar shape such as a square billet by an electromagnetic inspection method such as a leakage magnetic flux inspection method or an eddy current inspection method, a method of scanning the sensor in a plane is often used. .
[0003]
However, these electromagnetic inspection methods have a narrow effective sensor inspection range, so in order to ensure on-line inspection efficiency in the planar scanning method, multiple channels using a large number of sensors and a high-speed scanning mechanism are required. There is a need to adopt.
[0004]
Among these, in the case of adopting multi-channel, a large number of sensors are required, so that the equipment cost becomes enormous. In addition, when a high-speed scanning mechanism is adopted, a rotary type or a oscillating type high-speed scanner is required, and a scanning mechanism along the R portion of the corner is required. The distance from the material is 0. It may be difficult to maintain accuracy to maintain a delicate distance of several millimeters.
[0005]
Therefore, various methods using the surface wave ultrasonic method have been proposed.
For example, in Japanese Patent Publication No. 53-17315, surface waves are generated by using a jet nozzle that supplies coupling water to the propagation of surface wave ultrasonic waves (hereinafter simply referred to as “surface waves”), and the coupling is performed. A surface wave flaw detector that rotates a sensor has been proposed to cover the reduction of the propagation distance due to water attenuation.
[0006]
Also, Japanese Patent Publication No. 55-19503 proposes a surface wave flaw detector provided with an air purge header as a countermeasure for shortening the propagation distance caused by the attenuation of surface waves by coupling water in Japanese Patent Publication No. 53-17315. Has been.
[0007]
Japanese Patent Laid-Open No. 52-93389 proposes a flaw detection method in which surface waves are propagated in parallel with the corner side lines in order to detect flaws at the corners of steel materials.
Further, in JP 58- 9 2950, using a surface wave emanating from the two upper and lower tire probe, upon detecting a flaw on the surface by using a reflected signal from the defect, the inspection member There has been proposed a flaw detection apparatus that can stably follow the probe regardless of size, warpage, and the like.
[0008]
[Problems to be solved by the invention]
However, the surface wave flaw detectors proposed in Japanese Patent Publication Nos. 53-17315 and 55-19503 have a problem that a sufficient propagation distance cannot be obtained because water is used.
[0009]
Further, the flaw detection method proposed in Japanese Patent Application Laid-Open No. 52-93389 has a problem that an axial wrinkle generated at a corner portion cannot be detected because a surface wave is propagated parallel to the corner side line.
[0010]
Also, flaw detection apparatus proposed in JP 58 - 9 2950, because it is using a tire probe, when using the tire probe is to stabilize the incidence of surface waves, There is a case where a small amount of water is supplied between the material and the tire. In this case, since a reflection occurs at a point where the surface wave is incident on the material, a dead zone is generated at the incident point. Thus, in JP 58- 9 2950, the use of the two tire probe for examination of the dead zone, during testing, when the water is remaining on the surface of the material, Surface waves are reflected by water, causing false detection.
[0011]
Further, JP 58 - 9 in the proposed testing apparatus in No. 2950, in addition to using two tire probe, required because there is a complex tracking mechanism, increase in facility costs Inevitable. In addition, since a tire using thin rubber is scanned over a material with poor surface properties, there are many problems in practical use such as a short tire life.
[0012]
An object of the present invention is to provide a surface defect detection apparatus using a surface wave that can solve the above-described conventional problems.
[0013]
[Means for Solving the Problems]
In order to achieve the above-described object, the surface defect detection device of the present invention propagates a surface wave in a circumferential direction opposite to the surface by 180 ° along the surface of the material, and is disposed at a position separated by 90 ° in the circumferential direction of the material. The surface waves reflected from the defect are received using the two pairs of receiving sensors. And by doing in this way, the presence or absence of a defect can be determined, preventing a dead zone.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 6, in a method of detecting a defect by receiving a surface wave from an oscillation sensor and receiving the propagated surface wave with a reception sensor, the signal received by the reception sensor includes a reflected signal from the defect. In addition, there are signals that are propagated from the left and right of the oscillation sensor and directly detected by the reception sensor, and signals that are propagated through one round and detected by the reception sensor. For this reason, a defective signal existing at the same time position as these received signals cannot be identified, and a so-called dead zone occurs.
[0015]
On the other hand, for example, an oscillation sensor and a reception sensor are arranged in order on the same cross section of the square billet in a clockwise direction at a distance of 1/8, and surface waves oscillated from the oscillation sensor are moved along the surface of the square billet. FIG. 6A shows a surface wave reception waveform at the reception sensor when there is no defect on the surface of the square billet when propagating in the clockwise direction 9/8 rounds. FIG. 6 (a) shows the reception sensor when there is a defect. The surface wave reception waveform (9/8 round transmission echo) of FIG. 6 is shown in FIG. 6B. As shown in FIG. 6, if there is a defect on the surface of the square billet, some energy is being propagated. Since it is reflected, the defect signal F at the receiving sensor is detected.
[0016]
In FIG. 6, T is an oscillation signal from the oscillation sensor, DR is, for example, a direct reception signal that is propagated only in the clockwise direction and is received directly by the reception sensor, and Rcw is 9/8 in the clockwise direction. Rccw propagates the received signal (9/8 round transmitted echo) received by the receiving sensor and propagated 7/8 round in the counterclockwise direction and received by the receiving sensor (−7/8 round transmitted) E) indicates a received signal (reflected echo) received by the receiving sensor when the surface wave propagated in the clockwise direction is reflected by the artificial defect.
[0017]
FIG. 5 (a) shows the positional relationship of the sensor arrangement with respect to each surface of the square billet when the sensor arrangement is adopted, and FIG. 5 (b) shows the relationship between the effective flaw detection range and the dead zone. In FIG. 5 (b), the propagation wave in the CW direction and the propagation wave in the CCW direction when the oscillation sensor and the reception sensor are provided on the A surface of the square billet and the square billet is flawed are described separately.
[0018]
The surface wave oscillated in the CW direction is directly received as a received wave (signal) DR immediately after that, propagates once in the circumferential direction, and is detected as a CW1 wave. When this round propagates, if there is a defect on the B surface of the square billet, a defect signal is detected at E1 to E2 (edge 1 to edge 2) in FIG. That is, the reflected wave is detected between the E1 and E2 in order to propagate in the opposite direction to the CW after the reflected wave is reflected with respect to the round propagation wave.
[0019]
Similarly, if there is a defect on the C plane of the square billet, E2 to E3 (edge 2 to edge 3) in FIG. 5 and if there is a defect on the D plane of the square billet, E3 to E4 (edge) in FIG. 3 to edge 4), a defect signal is detected. On the other hand, in the CCW direction, a wave that makes one round of the square billet is detected as a received wave CCW1. Similarly to the CW direction, when the surface wave oscillated in the CCW direction has a defect on the D plane of the square billet, a defect exists on the C plane of the square billet at E4 to E3 in FIG. If there is a defect on the B surface of the square billet at E3 to E2 in the middle, a defect signal from each surface of the square billet will be detected as at E2 to E1 in FIG.
[0020]
Thus, CW1 is in the E2 to E3 / C plane of CW and E3 to E2 / C plane of CCW, and further in the E4 to E1 / A plane of the CW wave of the second round propagation wave and in the E1 to E4 / A plane of CCW. Alternatively, since CW2, CCW1, or CCW2 is detected and a dead zone is generated, the C plane and the A plane cannot be detected.
[0021]
On the other hand, flaw detection can be performed on the D and B surfaces, which are both sides of the A surface on which the oscillation sensor and the reception sensor are arranged, without causing a dead zone. Accordingly, in order to detect the entire surface, it is only necessary to arrange two pairs of sensors at positions 90 ° apart in the circumferential direction.
[0022]
However, the problem here is that the defect signal received by the receiving sensor may be from the B-side or D-side of the billet in the effective flaw detection zone Z. In the case of care processing, it is important to specify which surface has a defect.
[0023]
Therefore, this receiving sensor is composed of two sensors a and b, and the length thereof is set to ½ of the length of the saddle to be detected. As shown in FIG. Lay it out. Further, the oscillation sensor has an effective length equivalent to the length of the heel to be detected.
[0024]
In the receiving sensor having the above arrangement, the sensor 2a receives the defect signal before the sensor 2b in the reflected wave from the defect a on the A surface. In addition, in the reflected wave from the defect a on the c-plane, the sensor 2b receives the defect signal before the sensor 2a, so that it is possible to specify the surface where the defect exists.
[0025]
The present invention has been made based on the above findings and has the following configuration.
That is, the surface defect detection device of the present invention is a device for detecting a surface defect of a round or square billet or a steel pipe, and an oscillation sensor that oscillates a surface wave in a direction opposite to 180 °, and the same cross section as this oscillation sensor. A pair of reception sensors that are arranged in the immediate vicinity and detect surface waves are paired at two positions 90 ° apart in the circumferential direction of the round or square billet or steel pipe, and the signals received by these reception sensors are amplified. An amplifier and a determination unit for determining the presence or absence of a defect based on the ratio of the height of the defect signal to the height of the direct reception signal among the amplified signals are provided. And, if necessary, the receiving sensor is arranged with an axial length of at least 1/2 of the beam width through which the surface wave propagates, with a slight distance in the circumferential direction of the round or square billet or steel pipe. The two sensors are used as one channel sensor.
[0026]
In the surface defect detection apparatus of the present invention, the axial length of two single-channel sensors is set to at least 1/2 of the beam width for propagation of surface waves. This is to make the same and to efficiently receive the oscillated surface wave energy.
[0027]
In the surface defect detection device of the present invention, a surface wave is oscillated from the oscillation sensor to the surface of, for example, a square billet. Then, the surface wave is received by a receiving sensor arranged on the same cross section as the oscillation sensor, the signal received by these receiving sensors is amplified, and then the presence / absence of a defect is determined by the determination device from the height of the amplified signal. However, in the online automatic flaw detection line, a tracking mechanism is used to keep the relative position of the sensor and the material constant, but it is difficult to make it constant depending on the unevenness or bending of the material.
[0028]
Therefore, in the present invention, as shown in FIG. 2, two gates of a defective signal gate (F gate shown in FIG. 6B) and a direct reception signal gate (DR gate shown in FIG. 6B) are provided. I use it.
[0029]
Now, when the distance between the material and the sensor changes slightly, the transmission / reception efficiency decreases and the defect signal becomes small, so the defect may be missed. On the contrary, when approaching, the defect signal becomes large, so that a defect that is not harmful is overdetected.
[0030]
Therefore, if the defect signal height ratio Fn (= defect signal height Dn / direct reception signal height DRn) is used by utilizing the fact that the DR signal changes in the same way when the user is away or approaches, It is possible to prevent oversight and overdetection of defects due to distance changes.
[0031]
In the surface defect detection apparatus of the present invention, when two pairs of transmission / reception sensors are installed at positions 90 ° apart in the circumferential direction , for example, in the case of a square billet, a dead zone generated by the pair of sensors is generated. In addition, it is possible to detect defects on both sides with the receiving sensor placed on the upper and lower surfaces, and defects on the upper and lower surfaces with the receiving sensor placed on the side surface, and determine whether the defect exists on the upper or lower surface or both sides. Can do.
[0032]
In the surface defect detection apparatus of the present invention, the receiving sensor has an axial length of at least 1/2 of the beam width through which the surface wave propagates, and has a slight distance in the circumferential direction of a round or square billet or steel pipe. If two sensors that are arranged in a single channel are used, it is possible to determine whether a defect further exists on the upper surface, the lower surface, or on which side surface from the time difference between the signals received by the two sensors.
[0033]
【Example】
Hereinafter, the surface defect detection apparatus of the present invention will be described based on one embodiment shown in FIGS.
FIG. 1 is a configuration diagram of a surface defect detection device of the present invention, and FIG. 2 is a diagram showing determination logic in the surface defect detection device of the present invention.
[0034]
In FIG. 1, reference numerals 1a and 1b denote oscillation sensors that oscillate surface waves, and reference numerals 2a and 2b denote receptions arranged in the nearest cross section on the same cross section as the oscillation sensors 1a and 1b in the angular billet 3 to detect surface defects. It is a sensor. The oscillation sensors 1a and 1b cause a surface wave to oscillate by causing a pulsed eddy current to flow in a magnetic field (not shown) by an electric signal from the oscillator 4. In order to prevent two pairs of interference, the oscillation sensors 1a and 1b oscillate alternately.
[0035]
In the surface defect detection device of the present invention, the surface wave oscillated from the oscillation sensors 1a and 1b propagates at least the round billet 3 one or more times. The surface wave propagates on the surface of the square billet 3 in the clockwise direction and the counterclockwise direction and is received by the reception sensors 2a and 2b. The reception sensors 2a and 2b detect the surface wave as an electric signal by an induced voltage generated by material vibration (ultrasonic vibration) in a magnetic field.
[0036]
Reference numeral 5 denotes an amplifier that amplifies the signals received by the reception sensors 2a and 2b through the receivers 10a and 10b. The signal amplified by the amplifier 5 is input to the determination unit 6. In the embodiment shown in FIG. 1, the signal amplified by the amplifier 5 is also input to the CRT 7 so that the waveform can be confirmed.
[0037]
The determiner 6 is based on the ratio of the height of the reflected signal from the defect and the height of the directly received signal, based on the F gate and DR gate signals that are positioned from the gate unit 8 as shown in FIG. 6B. In the logic shown in FIG. 2, it is determined whether or not it is a defect, and if it is a defect, whether the defect exists on the upper or lower surface or both side surfaces of the square billet. When detecting the height of the defect signal and the direct reception signal, a sensor 2aa or 2ab described later, or a large signal in the sensor 2ba or 2bb is used.
[0038]
For example, the threshold value ARM of the defect signal height ratio obtained using an artificial defect processed on the surface of the square billet 3 is input to the determiner 6 in advance.
[0039]
When the inspection is started and, for example, a signal at a time axis position set in advance by the F gate and the DR gate is received by the reception sensor 2a and the signal amplified by the amplifier 5 is taken into the determination unit 6, the height of the defect signal A ratio Fn between Dn and the directly received signal height DRn is obtained.
[0040]
Then, the defect signal height ratio Fn is compared with the threshold ARM, and if the defect signal height ratio Fn is larger, it is determined as a defect. After these determinations are made, an alarm is issued. On the other hand, if Fn is smaller, it is determined that it is not a defect. After the determination, it is determined whether or not the inspection is in progress. If the inspection is not in progress, the inspection is terminated. If the inspection is in progress, the operation returns to the operation of the determination unit 6 described above.
[0041]
Next, as shown in FIG. 3, for example, the receiving sensor 2 b has an axial length of at least 1/2 of the beam width through which the surface wave propagates, and has a slight distance in the circumferential direction of the angular billet 3. As shown in FIGS. 4A and 4B, the defect 9 is detected from the time difference between the signals received by the two sensors 2ba and 2bb. Can be determined on the left and right sides, that is, on the upper surface or the lower surface.
[0042]
That is, when the two sensors 2ba and 2bb constituting the receiving sensor 2b are arranged as shown in FIG. 3, when the defect 9 exists on the upper surface of the square billet 3, the two sensors 2ba, As shown in FIG. 4A, the sensor 2ba closer to the upper surface of the square billet 3 receives the reflected signal from the defect 9 first, as shown in FIG. On the other hand, as shown in FIG. 4B, the sensor 2bb closer to the lower surface of the square billet 3 receives the reflected signal from the defect 9 first, as shown in FIG.
[0043]
Similarly, when the two sensors 2aa and 2ab (not shown) constituting the receiving sensor 2a are arranged with a slight distance in the circumferential direction of the square billet 3, any of both side surfaces of the square billet 3 is arranged. Needless to say, it can be determined whether or not there is a defect on the side surface.
[0044]
In the present embodiment, the case of detecting the surface flaw of a square billet has been described, but it goes without saying that the present invention can also be applied to the case of detecting the surface flaw of a round billet or a steel pipe.
[0045]
【The invention's effect】
As described above, the surface defect detection apparatus of the present invention propagates surface waves in a direction opposite to each other by 180 ° along the surface of the material, receives the surface waves by the respective receiving sensors, Since the presence or absence of a defect is determined based on the ratio of the magnitude of the defect signal and the direct reception signal, a surface defect can be detected with simple equipment without being affected by a change in distance without using a complicated mechanism.
[0046]
Further, in the surface defect detection device of the present invention, since two pairs of transmission / reception sensors are installed at positions 90 ° apart in the circumferential direction , flaw detection can be performed all around without causing a dead zone. For example, in the case of a square billet It is possible to determine whether a defect exists on the upper and lower surfaces or both side surfaces. In this method, four pairs of transmission / reception sensors are required in the method of propagating surface waves in one direction. However, according to the method of the present invention, two pairs of transmission / reception sensors are sufficient, and the equipment can be compressed.
[0047]
In the surface defect detection apparatus of the present invention, the receiving sensor has an axial length of at least 1/2 of the beam width through which the surface wave propagates, and has a slight distance in the circumferential direction of a round or square billet or steel pipe. If two single-channel sensors are arranged, it is possible to determine whether a defect further exists on the upper surface, the lower surface, or on which side. Further, since the flaw detection zone is between DR and CCW1, the propagation distance of the surface wave is the same on both side surfaces of the transmission / reception sensor, and the same detection performance is obtained. Further, since the space between CW1 and CCW2 is not used as a flaw detection zone, the propagation distance of the surface wave can be shortened, and this is a flaw detection method in which the S / N ratio does not decrease due to the influence of attenuation.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a surface defect detection apparatus of the present invention.
FIG. 2 is a diagram showing determination logic in the surface defect detection apparatus of the present invention.
3A and 3B are explanatory views of an arrangement example of a receiving sensor corresponding to claim 2, wherein FIG. 3A is a diagram viewed from the front, and FIG. 3B is a diagram of a main part viewed from the side of FIG.
FIGS. 4A and 4B are diagrams showing detection positions of the respective sensors when a reception signal of a defect is received by the reception sensor of FIG. 3, wherein FIG. 4A is a clockwise direction, and FIG. 4B is a counterclockwise direction. It is a figure which shows the case of.
FIG. 5A is a diagram showing the positional relationship of a sensor with respect to a square billet, and FIG. 5B is a diagram showing the received waveform when a surface wave is propagated along the surface of the square billet, with the CW direction and the CCW direction being distinguished. It is shown and it is the figure which showed generation | occurrence | production of the effective flaw detection zone and a dead zone.
FIG. 6 is a diagram showing a surface wave reception waveform when a surface wave is propagated along the surface of a square billet, where (a) shows a case where no artificial defect exists on the surface of the square billet, and (b) shows a square billet. This is a case where an artificial defect is present on the surface of the film, and is also an explanatory diagram for setting the F gate and the DR gate.
[Explanation of symbols]
1a Oscillation sensor 1b Oscillation sensor 2a Reception sensor 2b Reception sensor 3 Square billet 5 Amplifier 6 Determinator 9 Defect

Claims (2)

A device that detects surface defects in round or square billets and steel pipes, and an oscillation sensor that oscillates surface wave ultrasonic waves in a direction opposite to 180 °, and a surface wave that is disposed in the immediate vicinity on the same cross section as this oscillation sensor. A pair of receiving sensors to be detected are provided at two positions 90 ° apart in the circumferential direction of the round or square billet or steel pipe, and an amplifier for amplifying a signal received by these receiving sensors, and the amplified signal A surface defect detection apparatus comprising a determination device for determining the presence or absence of a defect based on a ratio between a defect signal height and a direct reception signal height. The receiving sensor has an axial length of at least 1/2 of the beam width through which the surface wave ultrasonic wave propagates, and two receiving sensors are arranged with a slight distance in the circumferential direction of a round or square billet or steel pipe. 2. The surface defect detection apparatus according to claim 1, wherein the surface defect detection apparatus is a channel sensor.

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