JP2000121613A - Surface defect detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface defect detecting device adapted to detect a surface defect by using a surface wave and specify the position of the surface defect accurately. SOLUTION: This surface defect detecting device is so constructed that oscillation sensors 1a, 1b for oscillating a surface ultrasonic wave in the opposite directions at 180 deg. and receiving sensors 2a, 2b disposed near by on the same section as the sensors 1a, 1b for detecting the surface wave are provided in a pair, two pairs in total at positions spaced from each other by 90 deg.. The detecting device includes an oscillator 4 having a timing circuit 5 for alternately switching the oscillation of the oscillation sensors 1a, 1b, a gate unit 8 for detecting a defect signal among signals received by the receiving sensors 2a, 2b and amplified, a determining device (comparator 11) for discriminating a harmful defect according to the magnitude of a defect signal detected by the gate unit 8, and a discriminator 12 for discriminating the position of a defect according to an output signal from the comparator 11 and a previously input logic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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]

2. Description of the Related Art As a method of inspecting a surface flaw of a metal material, for example, there is an electromagnetic inspection method such as a magnetic flux leakage inspection method or an eddy current inspection method. Then, when 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 a sensor in a plane is often used.

However, since the effective inspection range of the sensor is narrow in these electromagnetic inspection methods, in order to secure the on-line inspection efficiency in the plane scanning method, it is necessary to increase the number of channels using a large number of sensors or to increase the speed. It is necessary to employ a scanning mechanism.

[0004] Among them, when adopting the multi-channel, a large number of sensors are required, so that the equipment cost becomes enormous. When a high-speed scanning mechanism is used,
Rotary and oscillating high-speed scanners are required,
Since a scanning mechanism along the R portion of the corner is required,
The device configuration becomes complicated, and the distance from the material is reduced to 0. Several mm
And it is difficult to maintain the accuracy for keeping the delicate distance.

Therefore, various methods using a surface acoustic wave method have been proposed. For example, in Japanese Patent Publication No. 53-17315, surface wave ultrasonic waves (hereinafter simply referred to as "surface waves").
A surface wave flaw detection device has been proposed which generates a surface wave using a jet nozzle that supplies coupling water for the propagation of water, and rotates a sensor to cover a reduction in the propagation distance due to the attenuation of the coupling water. .

In Japanese Patent Publication No. 55-19503, as a measure for shortening the propagation distance due to the attenuation of the surface wave due to the coupling water in the above-mentioned Japanese Patent Publication No. Sho 53-17315, a surface wave flaw provided with an air purge header is provided. A device has been proposed.

Japanese Patent Application Laid-Open No. 52-93389 proposes a flaw detection method in which a surface wave is propagated in parallel with a corner side line in order to detect a flaw at a corner of a steel material.
In Japanese Patent Application Laid-Open No. 58-72950, the size of a material to be inspected is determined by detecting surface flaws using surface acoustic waves emitted from two upper and lower tire probes and using reflection signals from defects. A flaw detection device that can stably follow a probe regardless of warpage or the like has been proposed.

[0008]

However, the surface wave flaw detectors proposed in JP-B-53-17315 and JP-B-55-19503 use water, so that a sufficient propagation distance cannot be obtained. There is.

In the flaw detection method proposed in Japanese Patent Application Laid-Open No. 52-93389, there is a problem that an axial flaw generated at a corner cannot be detected because a surface wave is propagated in parallel with a corner side line.

The flaw detection device proposed in Japanese Patent Application Laid-Open No. 58-72950 uses a tire probe. However, when a tire probe is used, it is necessary to stabilize the incidence of surface waves. In some cases, a small amount of water is supplied between the material and the tire. In this case, since reflection occurs at a point where the surface wave is incident on the material, a dead zone is generated at the incident point. Therefore, in Japanese Patent Application Laid-Open No. 58-72950, two tire probes are used for the inspection of the dead zone. However, if the water remains on the surface of the material at the time of flaw detection, As a result, the surface wave is reflected, causing an erroneous detection.

In addition, the flaw detector proposed in Japanese Patent Application Laid-Open No. 58-72950 uses two tire probes and requires a complicated follow-up mechanism, so that equipment costs are reduced. Growth is inevitable. In addition, since a tire using a thin rubber is scanned over a material having poor surface properties, there are many problems in practical use such as a short life of the tire.

An object of the present invention is to provide a surface defect detecting apparatus using a surface wave which can solve the above-mentioned conventional problems.

[0013]

In order to achieve the above-mentioned object, a surface defect detecting apparatus according to the present invention comprises a pair of an oscillation sensor and a reception sensor, and two pairs are arranged at positions separated from each other by 90 °. One of the oscillation sensors and the other oscillation sensor are alternately oscillated at appropriate timings, and the surface wave is propagated along the surface of the material in a circumferential direction opposite by 180 °, and the oscillation by these oscillation sensors is received. The sensor receives and amplifies the signal, detects a defect signal from the amplified signal, and detects a harmful defect signal from the magnitude of the defect signal. If the signal is a harmful defect signal, the defect signal is a harmful defect. Then, the position where the defect exists is discriminated based on the signal indicating that the defect is present and the logic input in advance.
And in this way, while preventing the dead zone,
The presence or absence of a defect can be determined.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 6, in a method of oscillating a surface wave from an oscillation sensor and receiving a propagated surface wave by a reception sensor to detect a defect, a signal received by the reception sensor is used. Is not only the reflected signal from the defect,
There are signals that propagate from the left and right sides of the oscillation sensor and are directly detected by the receiving sensor, and signals that propagate in one round and are detected by the receiving 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.

On the other hand, for example, an oscillation sensor and a reception sensor are sequentially arranged at a position 1/8 turn clockwise on the same cross section of the square billet, and the surface wave oscillated from the oscillation sensor is transmitted to the surface of the square billet. FIG. 6A shows the surface wave reception waveform of the receiving sensor when no defect is present on the surface of the square billet when propagation is performed 9/8 times clockwise in the direction of. FIG. 6B shows a surface wave reception waveform (9/8 round transmission echo) at the reception sensor. As shown in FIG. 6, when a defect exists on the surface of the square billet, a part of energy is lost. Since the light is reflected during the propagation, the defect signal F at the receiving sensor is detected.

In FIG. 6, T is an oscillation signal from the oscillation sensor, DR is, for example, a direct reception signal that propagates only 1/8 of a clockwise turn and is directly received by the reception sensor.
Rcw represents a received signal (a 9 / 8-lap transmitted echo) that has propagated clockwise in a 9 / 8-lap and received by the receiving sensor.
cw represents a received signal (−7/8 round transmitted echo) that has propagated 7/8 round in the counterclockwise direction and received by the receiving sensor,
Indicates that the surface wave propagated clockwise is reflected at the defect,
The reception signal (reflection echo) received by the reception sensor is shown.

FIG. 5 shows the positional relationship of the sensor arrangement with respect to each surface of the square billet when the sensor arrangement is used.
FIG. 5A shows the relationship between the effective flaw detection range and the dead zone.
(B). In FIG. 5B, 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 surface A of the square billet and the square billet is detected are separately described.

The surface wave oscillated in the CW direction is immediately received as a directly received wave (signal) DR, propagates once in the circumferential direction, and is detected as a CW1 wave. During this one round of propagation, if a defect exists on the B side of the square billet, a defect signal will be detected at E1 to E2 (edge 1 to edge 2) in FIG. In other words, the reflected wave is detected between E1 and E2 because the reflected wave propagates along the same path in the opposite direction to the CW after being reflected.

Similarly, if there is a defect on the C-plane of the square billet, E2 to E3 (edges 2 to 3) in FIG.
If there is a defect on the D surface of the square billet, E3 to E3 in FIG.
A defect signal is detected at E4 (edge 3 to edge 4). On the other hand, in the CCW direction, a wave that has made one round of the angular billet is detected as the received wave CCW1. As in the case of the CW direction, the surface wave oscillated in the CCW direction also shows that if a defect exists on the D-plane of the square billet, a defect exists on E4 to E3 in FIG. If there is a defect on the B-side of the square billet in E3 to E2 in the middle, as shown in E2 to E1 in FIG.
A defect signal from each surface of the square billet will be detected.

Thus, the E2 to E3 / C plane of CW and CC
In the E3 to E2 / C plane of W, and in the E4 to E1 / A plane of the CW wave of the propagation wave of the second round and the E1 to E4 / A plane of CCW, C
Since W1 or CW2, CCW1 or CCW2 is detected, a dead zone is generated, so that the surface C and the surface A cannot be detected.

On the other hand, flaw detection can be performed on the D and B faces, which are both sides of the A face on which the oscillation sensor and the reception sensor are arranged, without generating a dead zone due to the sensor arrangement.
Therefore, in order to detect a flaw on the entire surface, two pairs of sensors may be arranged at 90 ° positions in the circumferential direction.

However, the problem here is that the defect signal received by the receiving sensor may be from the plane B of the angular billet or from the plane D in the effective flaw detection zone Z. In the case of a maintenance process in a process, it is important to specify which surface has a defect.

Accordingly, the present invention provides an oscillation sensor which oscillates surface acoustic waves in directions opposite to each other by 180 ° as described above, and a receiving sensor which is disposed immediately on the same cross section as the oscillation sensor and detects surface waves. Are provided as a pair at a position separated by 90 °, and the oscillation of one oscillation sensor and the oscillation of the other oscillation sensor of the pair of the oscillation sensor and the reception sensor are alternately measured at timing. An oscillator having a circuit for switching to a signal, an amplifier for amplifying a signal received by each receiving sensor, a gate device for detecting a defect signal from the signal amplified by the amplifier, and a defect signal detected by the gate device A discriminator that identifies a harmful defect from the size of the discriminator, and a discriminator that discriminates a position where the defect exists based on an output signal from the discriminator and logic input in advance. It is equipped with.

According to the above configuration, the oscillation from one of the oscillation sensors and the oscillation from the other oscillation sensor are alternately switched at appropriate timing to oscillate, and the defective signal is obtained from the signal received and amplified by the receiving sensor. If there is a defect signal, the presence or absence of a harmful defect is identified based on the magnitude of the defect signal. If the defect signal is a harmful defect, it is determined based on a harmful defect signal and a logic previously input. The position where the defect exists is discriminated. As a result, defect detection and position discrimination of a defective portion can be accurately performed.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface defect detecting device according to the present invention will be described below with reference to one embodiment shown in FIGS. FIG. 1 shows a schematic configuration of a surface defect detection device of the present invention. FIG. 2 shows an angular billet subjected to ultrasonic flaw detection by the surface defect detection device of the present invention. FIG. 3 shows the oscillation of the oscillation sensor and the reception status of the reception sensor. FIG. 4 shows the oscillation of the oscillation sensor, the reception signal of the reception sensor, and the position of the set gate.

In FIG. 1, reference numerals 1a and 1b denote oscillation sensors for oscillating surface waves, and reference numerals 2a and 2b denote corner billets 3 for detecting surface defects.
This is a receiving sensor that is disposed immediately on the same cross section as 1b. The oscillation sensors 1a and 1b cause a pulse-like eddy current to flow in a magnetic field (not shown) in response to an electric signal from the oscillator 4 to oscillate a surface wave. Reference numeral 5 denotes a timing circuit that measures the oscillation timing of the oscillation sensors 1a and 1b in the oscillator 4 in order to prevent interference of the oscillations of the oscillation sensors 1a and 1b and to perform defect position discrimination described later.

In the surface defect detecting device of the present invention, the surface wave oscillated from the oscillation sensors 1a and 1b propagates at least one time in the angular billet 3 or more. The surface wave propagates on the surface of the angular billet 3 in the clockwise direction (CW) and the counterclockwise direction (CCW), and is received by the receiving sensors 2a and 2b. Receiving sensor 2
a and 2b detect the surface wave as an electric signal by an induced voltage generated by material vibration (ultrasonic vibration) in a magnetic field.

7a and 7b are the receiving sensors 2a and 2b
Is an amplifier that amplifies the signal received at the receiver via the respective receivers 6a and 6b. 8 is an amplifier 7a, 7b
Is a gating device for detecting a defective signal from the signal amplified in step (1). Reference numeral 9 denotes a gate generator that sets a signal (hereinafter, referred to as a gate signal) at a predetermined time axis position and outputs the signal to the gate unit 8. In the embodiment shown in FIG. 1, the signal input to the gate unit 8 is also input to the CRT 10 so that the waveform can be confirmed.

Reference numeral 11 denotes a comparator for determining whether the defect signal is larger than a threshold set at a predetermined level when the gate unit 8 detects a defect signal. Reference numeral 12 denotes a discriminator for discriminating a position where a defect is present from a signal indicating that the signal is harmful in the comparator 11 and a logic inputted in advance. Reference numeral 13 denotes an output signal for marking a position where a defect exists.

Next, a case will be described in which, for example, ultrasonic flaw detection of a square billet 3 as shown in FIG. Oscillation sensors 1a, 1b
As shown in the figure, the reception sensors 2a and 2b are provided with the oscillation sensor 1a and the reception sensor 2a on the upper surface, and the oscillation sensor 1b and the reception sensor 2b on the right side of the paper 90 ° away from the oscillation sensor 1a and the reception sensor 2a. ing.

As will be described in detail later, the square billet 3 shown in FIG. 2 will be described in advance in the discriminator 12 with points A to P, planes AC, CE, EG, GI, and GI. I to K,
It is recognized as eight surface portions, that is, surfaces K to M, surfaces M to O, and surfaces O to A, and four corner portions of corner A, corner E, corner I, and corner M.

For example, as shown in FIG. 3, the timing circuit 5 shifts the oscillation sensor 1b by half the oscillation interval of the oscillation sensor 1a to shift the oscillation sensor 1b.
The timing is measured so as to oscillate at the same interval as a. Therefore, the oscillation sensors 1a and 1b alternately emit the surface acoustic waves. On the other hand, the receiving sensors 2a and 2b always receive signals as shown in FIG. 3, regardless of the oscillation timing of the oscillation sensors 1a and 1b.

The signals received by the receiving sensors 2a and 2b are amplified by amplifiers 7a and 7b via receivers 6a and 6b, and then input to the gate unit 8 and the CRT 10
The waveform is displayed with.

On the other hand, as shown in FIG. 4, when the oscillation sensor 1a oscillates, the gate generator 8 sets the gate signals 1, 2, 3, 7, and 8 and outputs them to the gate unit 8. Also, when the oscillation sensor 1b transmits, the gate signals 4, 5, 6, 9, and 10 are set and output to the gate unit 8.

FIG. 4A shows a waveform when the oscillation sensor 1a oscillates and is received by the reception sensor 2a.
(B), the oscillation sensor 1a oscillates and the reception sensor 2
4C shows the waveform when the oscillation sensor 1b oscillates, and FIG. 4D shows the waveform when the oscillation sensor 1b oscillates. FIG. 4D shows the waveform when the oscillation sensor 1b oscillates. The waveforms received at 2b are shown together with the setting gates.

In FIG. 4, T is the oscillation sensor 1
The signals oscillated at a and 1b are propagated clockwise around the outer periphery of the square billet 3 by the CW, and the signals directly received by the receiving sensors 2a and 2b are propagated counterclockwise around the outer periphery of the square billet 3. , Signals received by the direct receiving sensors 2a and 2b, respectively.

When there is a defect on the surface of the square billet 3, a signal other than the signal shown in FIG. 4 (hereinafter referred to as a defect signal) is received.
a, 2b, the receivers 6a, 6b, the amplifier 7
The signal is input to the gate unit 8 via the gates a and 7b, and the gate unit 8 detects a defect signal. The defect signal is input to a comparator 11 where a comparison is made as to whether the defect signal is above a predetermined level threshold. Comparator 1
If the defect signal is higher than the threshold value, the discriminator 1 identifies the defect signal as a harmful defect and outputs a digital pulse signal indicating the fact to the discriminator 12. Note that the comparator 11
The gate signals 1 to 10 set together with the digital pulse signal to be output to the discriminator 12 are output.

In the discriminator 12, the square billet 3 is determined based on the digital pulse signal and the logic shown in Tables 1 and 2 below.
In the position where the defect exists.

[0039]

[Table 1]

[0040]

[Table 2]

For example, in the case of the square billet 3 shown in FIG.
Since the reception sensor 2b receives the defect signal with the gate signal 6 shown in FIG. 4D from the signal oscillated at b, it is possible to specify that there is a defect at the L position from this result. Incidentally, the receiving sensor 2a receives the defect signal with the signal oscillated by the oscillation sensor 1a at the gate signal 7 shown in FIG. 4A, and the receiving sensor 2b generates the defect signal with the signal oscillated by the oscillation sensor 1b. FIG. 4 (d)
When the gate signal 9 is received, it can be specified that the corner E has a defect as shown in Table 2 above.

In this embodiment, the case where the surface flaw of the square billet 3 is detected has been described. However, it is needless to say that the present invention can be applied to the case where the surface flaw of a round billet or a steel pipe is detected. Also, the number of divisions of the peripheral surface and the number of gate signals can be set as appropriate, and furthermore, by appropriately setting the threshold level appropriately, surface defect detection can be performed with high accuracy as described above. .

[0043]

As described above, in the surface defect detecting device of the present invention, two pairs of oscillation and receiving sensors are installed at positions separated by 90 °, and the oscillation timings of the two oscillation sensors are alternately switched. ° Propagating surface waves in opposite directions along the surface of the material, detecting the defect signal from the signals received by the receiving sensor, identifying the harmful defect from the magnitude of the defect signal, harmful defect signal Is determined based on the signal indicating that the defect is present and the logic inputted in advance, so that the surface defect can be detected with simple equipment without using a complicated mechanism and the defect can be detected. The position can be discriminated.

Further, the surface defect detection device of the present invention can detect flaws in the entire periphery without producing a dead zone. For example, in the case of a square billet, it is possible to discriminate where a defect exists. . This method requires four pairs of transmission / reception sensors in the method of propagating a surface wave 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 reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a surface defect detection device of the present invention.

FIG. 2 is a diagram showing an arrangement example of an oscillation sensor and a receiving sensor in a square billet where ultrasonic testing is performed, and also showing a state where the surface of the square billet is divided.

FIG. 3 is a diagram for explaining oscillation of an oscillation sensor and a reception state of a reception sensor.

FIG. 4 shows the oscillation of the oscillation sensor and the reception status of the reception sensor in detail. FIG. 4A shows a waveform when one oscillation sensor oscillates and one reception sensor receives the waveform.
(B) shows a waveform when one of the oscillation sensors oscillates and is received by the other reception sensor, and (c) shows a waveform when the other oscillation sensor oscillates and the one reception sensor receives. (D) is a diagram showing waveforms when the other oscillation sensor oscillates and is received by the other reception sensor, together with the setting gates.

5A is a diagram showing a positional relationship of a sensor with respect to an angular billet, and FIG. 5B is a diagram showing a reception waveform when a surface wave is propagated along the surface of the angular billet by distinguishing between a CW direction and a CCW direction. FIG. 4 is a diagram showing the effective flaw detection zone and the occurrence of a dead zone.

6A and 6B are diagrams showing a surface wave reception waveform when a surface wave is propagated along the surface of the angular billet, where FIG. 6A shows a case where no artificial defect exists on the surface of the angular billet, and FIG. Is a case where an artificial defect is present on the surface of FIG. 2B, and is also an explanatory diagram of the setting of the F gate and the DR gate.

[Explanation of symbols]

 1a Oscillation sensor 1b Oscillation sensor 2a Receiving sensor 2b Receiving sensor 3 Square billet 5 Timing circuit 9 Gate generator 12 Discriminator

Claims (1)

[Claims] An apparatus for detecting a surface defect of a round or square billet or a steel pipe, comprising: an oscillation sensor for oscillating surface wave ultrasonic waves in directions opposite to each other by 180 °; Two pairs of receiving sensors arranged to detect surface waves are provided at a position separated by 90 ° as a pair, and the oscillation of one of the two pairs of the oscillation sensor and the reception sensor and the other oscillation sensor An oscillator having a circuit that alternates between the oscillation and the oscillation of each of the timings, an amplifier that amplifies the signal received by each receiving sensor, and a gate device that detects a defect signal from the signal amplified by the amplifier And a determiner for identifying a harmful defect based on the magnitude of the defect signal detected by the gate device, and a defect exists based on an output signal from the determiner and a logic inputted in advance. Surface defect detecting apparatus characterized by comprising a discriminator for discriminating the position.