JP2001318083A - Ultrasonic flaw detector and method of ultrasonic flaw detection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a defect at a low cost even if a long object vibrates or meanders while moving. SOLUTION: In this flaw detector, array probes 5, 7 are disposed around a cross-section of the long metallic object 2. Relative distance variations of the long object caused by its vibration or meandering are measured by a top surface echo and a bottom surface echo of the long object measured by one of the array probes to select the measurement range of a vibrator of the other array probe based on them, thus driving the array probe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detector and an ultrasonic flaw detection method for inspecting a defect existing in a long object such as a billet, a rail, a section steel and the like.

[0002]

2. Description of the Related Art Generally, when detecting a defect inside an object, an ultrasonic flaw detection method is used. In this ultrasonic flaw detection method, ultrasonic waves emitted from a probe are made incident on an object through an acoustic medium such as water, and ultrasonic waves reflected from a defect inside the object are received by the probe, and the defect is detected. It is to detect.

Inspection of internal defects existing in long objects such as billets, rails, and shaped steels detects defects while the long objects are being conveyed on a roller table. Two such methods are known.

One of the methods is called a water column method. An ultrasonic probe is attached to a nozzle, and water is jetted from the nozzle to form a water column between the probe and the object to be inspected. Then, the ultrasonic wave is made incident on the object to be inspected through the water column, and the ultrasonic wave reflected from the object to be inspected is received and flaw-detected. In the flaw detector using the water column method, the mechanical device having a mechanism for moving the probe in the vertical and horizontal directions and a mechanism for rotating the probe is used to position the probe with respect to the object to be inspected and to transmit ultrasonic waves. The irradiation direction is set.

[0005] Another method is called a water immersion flaw detection method. This is a method in which an object to be inspected is submerged or penetrated into a water tank filled with water, and ultrasonic waves are incident from a probe disposed in the water tank through the water in the water tank to detect the object to be inspected. It is.

[0006]

However, in the flaw detector using the water column method, it is necessary to use a relatively small probe in order to obtain a stable water column. In order to increase the flaw detection area of an object, a large number of probes must be provided. Also,
If the inspected object has various dimensions, the distance between the inspected object and the probe must be reset for all the probes in order to correspond to the inspected object of those dimensions.
Accordingly, a mechanical device having a mechanism for moving the probe in the vertical and horizontal directions and a mechanism for rotating the probe must be provided for each ultrasonic probe.

[0007] In addition, a moving long object is subject to vibration during transportation,
Since the relative position between the probe and the object to be inspected changes due to meandering or the like, the mechanical device provided with the mechanism needs to be configured to follow the vibration and meandering of the object to be inspected. In addition, the mechanism is large and complicated, and not only costs a large amount of equipment, but also requires a large amount of maintenance costs to maintain the accuracy of the apparatus for a long period of time.

On the other hand, changing the probe in response to the movement of the object to be inspected gives vibration to the water column, making it difficult to form a stable water column, thereby reducing the flaw detection accuracy. There is a problem such as cold.

The present invention has been made in view of the above circumstances, and stably maintains the relative position between a probe and a long object even with vibration and meandering during the conveyance of a long object, and has high accuracy. It is an object of the present invention to provide an ultrasonic flaw detector and an ultrasonic flaw detection method for performing flaw detection.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, a flaw detector according to the present invention uses a water immersion flaw detection method to detect a defect in a long object while conveying the long object in a predetermined conveyance direction. In an ultrasonic inspection device to be inspected, a first and a second array probes are arranged in a direction facing the side surface and any one of upper and lower surfaces of the long object and orthogonal to the transport direction. Configuration.

According to the present invention, the first and second array probes are disposed so as to face two adjacent surfaces of a long object. It is possible to accurately detect a defect of a long object from the output of the touch element, and it is possible to enhance the flaw detection performance even when the position of the long object fluctuates.

[0012] A flaw detector according to the present invention is an ultrasonic flaw detector which inspects a defect of the long object by a water immersion flaw detection method while transporting the long object in a predetermined transport direction. And either the upper or lower surface, and
First and second array probes arranged in a direction perpendicular to the transport direction, and ultrasonic waves incident on the long object from the first and second array probes, and the long object And a transducer selecting means for selecting a range of transducers constituting the array probe based on an ultrasonic signal reflected from the transducer.

The array probe has a plurality of transducers arranged in an array, and the plurality of transducers in the arrangement direction can generate or stop vibration individually. The present invention employs an array probe as described above, so that even when a long object undergoes a position change, the position of the long object can be changed without moving the probe. Correspondingly, by selecting and vibrating a probe in a necessary range, flaw detection is possible.

Next, the flaw detector according to the present invention uses the first and second array probes to vary the facing distance to the side surface and any one of the upper and lower surfaces of the long object. This is a configuration in which drive mechanisms for individually moving operations are provided.

According to the present invention having the above-described configuration, the position can be set to an appropriate distance based on the reflected ultrasonic level obtained from each probe.

On the other hand, the flaw detection method according to the present invention is directed to an ultrasonic flaw detection method for inspecting a defect of the long object by a water immersion flaw detection method while transporting the long object in a predetermined transport direction. A first step of setting one of the array probes facing the side surface and one of the upper and lower surfaces at a predetermined position, and irradiating the long object with ultrasonic waves; Irradiates ultrasonic waves reflected from the surface and bottom surface of the long object,
Based on a second step of determining the dimension of any of the following surfaces or side faces, and based on the dimensions determined in the second step,
A third step of selecting a transducer within a measurement range of the other array probe, and irradiation of ultrasonic waves from the transducer selected in the third step with side surfaces or upper and lower surfaces of the long object Selecting a transducer to be a measurement range of the one array probe from ultrasonic waves reflected from any of the surface and the bottom surface.

Therefore, by adopting such a method,
One array probe measures the position and shape of the long object and selects the vibrator of the other array probe. It is possible to perform flaw detection with good performance while avoiding the influence.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of the ultrasonic flaw detector according to the present invention. In FIG. 1, reference numeral 1 denotes a conveying table roller provided at a predetermined interval in a predetermined conveying line direction, and 2 denotes a billet, a round bar,
It is a long metal object such as a bar steel (rail or mold steel), and is conveyed in the direction of the arrow (a), for example, under the rotational direction of the table roller 1 and a required rotational speed. Reference numeral 3 denotes a water tank installed on the transport line of the long metal object 2, and an input opening 4a and an outlet opening 4b are formed on the upstream and downstream lines of the water tank 3, and the long metal object 2 Are transported in the order of the input opening 4a → the inside of the water tank 3 → the outlet opening 4b in accordance with the rotation of the table roller 1. Reference numeral 5 denotes a first member which is provided in the height direction of the side surface of the long metal object 2, irradiates ultrasonic waves toward the object surface, and detects flaws inside the long metal object 2 from ultrasonic waves reflected from the object. , Which includes a first array probe 5 that drives the first array probe 5 in the width direction of the long metal object 2.
Drive mechanism 6 is provided. 7 is installed along one of the upper surface width direction and the lower surface width direction of the long metal object 2, irradiates ultrasonic waves toward the object, and generates ultrasonic waves reflected from the inside of the object 2 inside the object 2. A second array probe for flaw detection, which is provided with a second drive mechanism 8 for driving the second array probe 7 in the vertical direction of the object. Have been.

The array probe 5 and the array probe 7
Are perpendicular to each other, and ultrasonic waves emitted from the array probe 5 do not interfere with the array probe 7, and ultrasonic waves emitted from the array probe 7 The long metal objects 2 are arranged slightly shifted in the transport direction of the long metal objects 2 so as not to interfere. The drive mechanisms 6 and 8 have a function that can be driven with a stroke that sets the array probe 5 and the array probe 7 at appropriate positions in accordance with the dimensions of the long metal object 2.

In the figure, reference numeral 9 denotes a long metal object passing through the entrance of the water tank.
An entrance passage detector for detecting 2, an exit passage detector for detecting a long metal object 2 passing on the exit side of the water tank, a water supply valve 11 for supplying water to the water tank 3, and a long metal object for 12. 2 is a pulse transmitter for measuring the transport distance.

Here, when detecting the long metal object 2, the array probes 5 and 7 are individually arranged along the height direction and the width direction of the long metal object 2 as described above. However, the reason will be described with reference to FIG.

As shown in the figure, a thin flat crack or inclusion is present inside the long metal object 2.
It is assumed that two exist as 1 and 22. One internal defect 21 exists along a plane parallel to the side surface of the long metal object 2 and has a narrow shape in the width direction. The other internal defect 22 exists along a plane parallel to the upper surface or the lower surface of the long metal object 2 and has a narrow shape in the vertical direction.

When such a defect is detected by the array probe 5, the internal defect 21 has a large area in a plane perpendicular to the ultrasonic wave to be irradiated, and the ultrasonic wave is reflected from the entire defect. As a result, the defect can be detected. However, it is difficult to detect the internal defect 22 because the area of the surface perpendicular to the irradiated ultrasonic waves is small. On the other hand, the relationship between the array probe 7 and the internal defects 21 and 22 is opposite to that described above. As a result, the array probe 5 has the ability to detect the internal defect 21, but the internal defect 22 has a high probability of overlooking the defect because its shape is narrow in the ultrasonic irradiation direction. Therefore, array probes 5 and 7 are provided to detect flaws extending in completely different directions.

Next, the operation of the above-described ultrasonic flaw detector will be described.

Now, by opening and closing the solenoid valve 11, the water tank 3 is full. At this time, the drive mechanisms 6 and 8 previously set the array probes 5 and 7 at required positions with strokes corresponding to the dimensions of the long metal object 2. If the long metal object 2 has various dimensions, an appropriate flaw detection position must be set for each dimension. However, by using an array probe, the ultrasonic irradiation range can be reduced by using the transducer of the array probe. It is possible by selecting. Therefore, the array probe and the long metal object 2
If it has a drive mechanism that can change only the distance to the position, it can be positioned at an appropriate flaw detection position even when the dimensions are changed.

In this state, when the table rolls 1,... Are driven to rotate in the direction shown in FIG. However, at this time, flaw detection is performed at the next timing.

That is, when the long metal object 2 is conveyed by the table rolls 1,..., And its tip is detected by the passage detector 9, the pulse signal generated by the pulse transmitter 12 for measuring the conveyance distance is taken in. The tip position of the long metal object 2 is tracked. When it is determined that the tip position of the long metal object 2 has reached the position corresponding to the installation of the array probe 5 through the opening 4a of the water tank 3 based on this tracking,
Each transducer of the array probe 5 is vibrated to start irradiation of ultrasonic waves (step 1). Since the array probe 5 is installed so as to detect a flaw from the side surface of the long metal object 2, the long metal object is obtained from the reflected wave from the side surface of the long metal object 2 and the reflected wave from the opposite side end surface. The distance to the side surface 2 and the dimension of the long metal object 2 can be obtained (step 2), and based on the measurement result, a transducer to be irradiated with ultrasonic waves of the array probe 7 is selected (step 3). .

Here, a method of calculating the distance and the dimension will be described. When a probe capable of irradiating and receiving ultrasonic waves is installed at a predetermined position, and the probe irradiates ultrasonic waves, FIG.
As shown in (2), the ultrasonic wave travels through the underwater distance L in the water tank, a part of the ultrasonic wave is reflected on the surface of the long metal object 2, and travels again through the water to reach the probe. The rest propagates along the internal distance D of the long metal object 2 and is reflected on the bottom surface of the long metal object 2 and again returns to the long metal object 2.
And reaches the probe through the water. When the reflected ultrasonic wave is captured by the probe and converted into an electric signal, a time-series signal waveform as shown in FIG. 4 is obtained. In FIG. 4, T is a waveform when an ultrasonic wave is emitted from the probe, and S is a long metal object 2.
B is a waveform when the ultrasonic wave reflected from the surface of the long metal object 2 is received, and B is a waveform when the ultrasonic wave reflected from the bottom surface from the long metal object 2 is received. The time ts from T to S is the time required for the ultrasonic wave emitted from the probe to travel through the water, be reflected on the surface of the long metal object 2, travel through the water again, and reach the probe. Here, assuming that the sound velocity in the water is Vw, the distance L between the probe and the surface of the long metal object 2 is expressed by equation (1).

L = Vw × ts / 2 (1) During the time tb from T to B, the ultrasonic wave emitted from the probe travels through the water to reach the long metal object 2 and the long metal object 2
This is the time required for the sound wave transmitted inside to be reflected on the bottom surface of the long metal object 2, travel again through the long metal object 2 and water, and reach the probe. Here, assuming that the sound velocity inside the long metal object 2 is Vm, the dimension D of the long metal object 2 is expressed by the following equation (2).

D = Vm × (tb−ts) / 2 (2) Therefore, the distance to the side surface of the long metal object 2 and the length of the long metal object 2 are calculated using the expressions (1) and (2). Can be obtained.

Here, a signal processing method when an internal defect signal is present in the main measurement signal will be described. FIG. 5 is a waveform diagram of a time-series signal captured by the ultrasonic probe. In FIG. 5, T is a waveform when an ultrasonic wave is emitted from the probe, S is a waveform when an ultrasonic wave reflected from the surface of the long metal object 2 is received, and D is the inside of the long metal object 2. B is a waveform when the ultrasonic wave reflected from the defect is received, and B is a waveform when the ultrasonic wave reflected from the bottom surface of the long metal object 2 is received. When these signals are compared, in S and B, all of the incident ultrasonic waves are reflected at a predetermined reflectance at the boundary surface between the water and the long object 2, while D is a part of the incident ultrasonic waves. The characteristic is that the sound receiving level of D is lower than the sound receiving level of S or B because it is reflected by an internal defect. Therefore, by setting a sound receiving level lower than the sound receiving level of S or B and higher than the sound receiving level of D as the threshold Ls, and extracting and processing only a signal higher than the threshold Ls, the ultrasonic signal is obtained. Even when a defect signal is included therein, the dimension of the long metal object 2 can be measured without being affected by the defect signal.

Further, the time t thus processed
Since a signal generated at time td between s and time tb can be determined to be a signal from the inside of the long metal object 2, the reflected wave is generated only when there is a reflected wave generated during this period due to an internal defect. If it is determined that a defect has occurred, erroneous detection can be prevented and the flaw detection accuracy can be increased.

Subsequently, when the leading end position of the long metal object 2 reaches the array probe 7, the array probe 7 selects the transducer determined by the signal of the array probe 5 and transmits the ultrasonic wave. Start irradiation. The array probe 7 is a long metal object 2
The distance from the reflected wave from the upper surface of the long metal object 2 and the reflected wave from the lower surface to the upper surface of the long metal object 2 and the length of the long metal object 2 The dimensions of the upper and lower sides can be determined. Then, based on the measurement result, a transducer for irradiating the ultrasonic wave of the array probe 5 is selected (step 4), and based on the selection result, the transducer in the range selected in advance is selected. To perform ultrasonic irradiation.

When the long metal object 2 is moved in the horizontal direction of the cross section, in the vertical direction of the cross section, or in the combined direction of the vertical and horizontal cross sections while the long metal object 2 is being conveyed, as shown in FIG. A transducer for irradiating the ultrasonic wave of the array probe 7 is selected and switched based on the distance from the side 5 to the side surface of the long metal object 2 and the size of the side surface of the long metal object 2, and at the same time, the array probe A transducer for irradiating the array probe 5 with ultrasonic waves is selected and switched based on the distance between the probe 7 and the upper surface of the elongated metal object 2 and the dimensions of the upper and lower surfaces of the elongated metal object 2. As described above, even when the long metal object 2 vibrates or meanders during transportation, the vibrator irradiates the ultrasonic waves of the array probe 7 with the position and the size of the long metal object 2 measured by the array probe 5. Is selected, and the range of the vibrator for irradiating the ultrasonic wave of the array probe 5 with the position and the size of the long metal object 2 measured by the array probe 7 is selected. A stable flaw detection area can be obtained with respect to the cross section.

When the cross section of the long metal object 2 is complicated and it is difficult to capture the reflected wave from the bottom surface of the long metal object 2, the long metal object 2 is sandwiched between the array probes 5. And the array probe 7
The array probes are arranged so as to sandwich the long metal object 2 in such a manner as to face each other, and each of the array probes is ultrasonically reflected from the long metal object 2 irradiated from each array probe. The range of the transducer to be irradiated with the ultrasonic wave of the transducer may be determined.

Although the range of the transducer of the array probe is determined in the above embodiment, the driving mechanisms 6 and 8 operate the probe so that the distance between the probe and the long object is always constant. The position may be controlled.

[0037]

As described above, according to the present invention, since an array probe is used, a flaw detection area in a cross section of a long object can be enlarged, and a long object having various dimensions as in the prior art can be obtained. The need for a moving mechanism and a rotating mechanism for positioning the probe and setting the irradiation direction of the ultrasonic wave in order to cope with the above becomes unnecessary, and it is possible to simplify the mechanism and reduce the equipment cost, Maintenance costs can be reduced even in long-term use. Furthermore, highly reliable flaw detection is possible, such as maintaining a stable relative distance between the probe and the long object due to vibration or meandering during the conveyance of the long object.

[Brief description of the drawings]

FIG. 1 is a view showing the operation of a water immersion ultrasonic testing apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a defect generated inside a metal object and a probe for detecting the defect.

FIG. 3 is a diagram showing a transmission state of an ultrasonic wave.

FIG. 4 is a diagram showing time-series signals of reflected ultrasonic waves.

FIG. 5 is a diagram showing a time-series signal of reflected ultrasound including a defect signal.

FIG. 6 is a diagram illustrating a method of switching the range of the transducer of the other array probe based on the measurement of one array probe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transport table roll 2 ... Long metal object 3 ... Water tank 4a, 4b ... Opening of water tank 5 ... Array probe 6 ... Drive mechanism of array probe 5 7 ... Array probe 8 ... Array search Driving mechanism of child 7 9 ... Entry passage detector 10 ... Outlet passage detector 11 ... Solenoid valve for water tank water supply 12 ... Pulse transmitter for measuring long object conveyance distance

Claims (4)

[Claims] 1. An ultrasonic flaw detector for inspecting a defect of a long object by a water immersion flaw detection method while conveying the long object in a predetermined conveyance direction, wherein: An ultrasonic flaw detector wherein the first and second array probes are arranged in a direction facing the surface and perpendicular to the transport direction. 2. An ultrasonic flaw detector for inspecting a defect of a long object by a water immersion flaw detection method while conveying the long object in a predetermined conveyance direction, wherein the ultrasonic test apparatus is provided with a side surface and an upper or lower side of the long object. And a second array probe disposed in the direction orthogonal to the transport direction and facing the surface of the first and second arrays, and ultrasonic waves are transmitted from the first and second array probes to the long object. And a transducer selecting means for selecting a range of transducers constituting the second and first array probes based on an ultrasonic signal reflected from the long object.
An ultrasonic flaw detector which avoids the influence of the position change of the long object. 3. The ultrasonic flaw detector according to claim 1, wherein the first and second flaws are varied to change a confronting distance between a side surface and an upper or lower surface of the long object. An ultrasonic flaw detector comprising a drive mechanism for individually moving and operating each of the array probes. 4. An ultrasonic flaw detection method for inspecting a defect of a long object by a water immersion flaw detection method while transporting the long object in a predetermined transport direction, wherein: A first step of setting one array probe facing the surface at a predetermined position, and irradiating the long object with ultrasonic waves, and irradiating the long object with ultrasonic waves in the first step. A second step of determining the size of the upper or lower surface or side surface of the long object from the ultrasonic waves reflected from the front surface and the bottom surface, based on the size determined in the second step, To select a transducer within the measurement range of the array probe
And the one array from the ultrasonic waves reflected from the surface or the bottom surface of either the side surface or the upper or lower surface of the long object by the irradiation of the ultrasonic wave from the transducer selected in the third step. 4th selection of transducers within the measurement range of the probe
Ultrasonic testing method comprising the steps of: