JP2705514B2 - Ultrasonic flaw detection method for welded H-section steel welds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detection method for a welded H-section steel weld, and more particularly to an ultrasonic flaw detection method for a welded H-section steel weld for ensuring quality over the entire length of the welded H-section steel.

[0002]

2. Description of the Related Art In the manufacture of H-section steels, large H-section steels are manufactured by rolling, but lightweight H-section steels are generally manufactured continuously by resistance welding. Since the quality of a welded lightweight H-section steel mainly depends on the presence or absence of a weld defect, it is extremely important for quality assurance to test whether or not a weld has a defect. For quality assurance, an online ultrasonic flaw detection method has conventionally been adopted.

FIG. 15 is an explanatory view of a conventional typical ultrasonic flaw detection method for a welded H-section steel, in which a flat probe 2 ′ is disposed above the center of a flange 1 F of a welded H-section steel 1, and a water tank 3 is provided. Is filled with water 4 and a local water immersion method is performed. A parallel ultrasonic beam is incident from a probe 2 ′ to a welded portion 5 between the flange 1F and the web 1W, and an echo is reflected from a position corresponding to the thickness of the flange 1F. By monitoring the height, the presence or absence and size of the defect are estimated.

However, it has been found that this method has problems in the following points. First of all, according to this method,
Since the ultrasonic beam is incident over an area wider than the welded portion, the sum of both the bottom echo and the defect echo on the flange 1F is detected, and the waveform becomes a waveform in which the defect echo is superimposed on the bottom echo and discrimination is not possible. To be able to
Detection accuracy is extremely low.

Second, the defect echo generally has a low echo height when the surface of the defect is rough or inclined with respect to the beam incident direction, which further contributes to the above-described poor detection accuracy. Was on.

Accordingly, the applicant of the present invention has disclosed the above-mentioned
No. 020 and JP-A-59-99254 disclose a method of performing an ultrasonic flaw detection with high accuracy by using a focus type probe having high defect detection accuracy.

In the former, as shown in FIG. 16, a focused probe 2 capable of reciprocating in the thickness direction of a web 1W of a welded H-section steel 1 is used, and a focused ultrasonic beam is incident from above a flange 1F. In addition, the ultrasonic beam is reciprocated right and left about the welding center line to perform ultrasonic flaw detection.

On the other hand, as shown in FIG. 17, a large number of focal spots are arranged above the flange 1F of the welded H-section steel 1 over a length 1 in the width direction capable of covering at least the welded portion at intervals P in the width direction. The ultrasonic probe is arranged by arranging the type probes 2 and making a focused ultrasonic beam incident from each probe 2.

[0009]

Problems to be Solved by the Invention
In the method described in JP-A-15020, the probe 2 is reciprocated right and left around a welding center line in order to enable a single focus type probe 2 to detect flaws in the entire width direction of the welded portion. While performing the flaw detection by injecting an ultrasonic beam from above the flange 1F, the trajectory of each flaw detection point by the probe 2 in the longitudinal direction of the welded H-beam 1
A waveform as shown in FIG. 18 is drawn.

In this case, for example, the probe is provided with an amplitude of 10 mm with respect to the thickness of 2.3 mm of the web 1W so that the welded portion 5 can be slightly fluctuated right and left due to the conveyance of the welded H-section steel 1. Because of the reciprocating movement of No. 2, flaw detection at portions other than the circled portion in FIG. 18 becomes impossible. Therefore, for example, when the unwelded defect passes through the X point other than the circle, the portion passes as it is as a healthy weld.

On the other hand, in the method described in Japanese Patent Application Laid-Open No. Sho 59-99254, flaw detection can be performed over substantially the entire width of the welded portion by arranging a large number of focus-type probes 2. On the other hand, the configuration of the apparatus must be complicated. In addition, the thickness of the flange usually changes in the range of 3.0 to 12.0 mm. However, it is not practical to change the arrangement of the probe every time, because it is difficult to adjust the probe.

On the other hand, the inventor has also performed the method shown in FIG. That is, one focus-type probe 2 is fixed at a position above the center of the flange 1F of the welded H-section steel 1, and the focused ultrasonic beam from the probe 2 is orthogonally incident on the flange 1F and is superposed. This is to perform sonic flaw detection.

However, in this method, the welded H-section steel usually has a runout of 10 mm or more on the left and right during the conveying process.
When the ultrasonic beam from the probe 2 comes off the welded portion 5 and enters the flange bottom surface, the returned echo is determined to be an unwelded defect echo while being an echo of the flange bottom surface, There is a possibility that a defect determination signal is output.

Further, since the effective flaw detection width of the ultrasonic beam from the focus type probe is only about Ef ≒ 0.6 mm, even if the ultrasonic flaw detection is performed continuously, the result is as follows.
Intermittent flaw detection at a certain pitch, and cannot be performed over the entire length of the welded H-section steel. The problem of intermittent flaw detection caused by the effective flaw detection width also applies to the methods disclosed in the above publications.

Therefore, the present inventor has used a focus type probe capable of detecting flaws with high detection accuracy, and has attempted to increase the effective flaw detection width of this probe so as to ensure the entire H-shaped steel welded portion. In order to perform ultrasonic flaw detection, the focus probe is fixed at a position separated from the center of the flange of the welded H-section steel that is continuously conveyed, and water is used as a propagation medium from the probe as water. A sound wave beam is orthogonally incident on the flange, and while continuously performing ultrasonic flaw detection, a web restraining roller is provided to abut on both sides of the web of the welded H-section steel and regulate a pass line of the welded H-section steel, Furthermore, it has been found that it is effective to focus the ultrasonic beam at a position between the probe and the outer surface of the flange.

According to this method, in the process of transporting the welded H-section steel, the probe always looks at the welding surface, so that no flaw detection leakage occurs. Further, the focus of the ultrasonic beam from the probe is focused at a position between the probe and the outer surface of the flange, so that the effective flaw detection width of the probe can be increased. As a result, as shown in FIG. 8, since the ultrasonic beam from the probe performs the flaw detection while overlapping, the continuous flaw detection becomes possible, and therefore, there is an advantage that the flaw detection can be reliably performed over the entire length of the welded H-section steel. .

However, it has been found that there is a new problem here. That is, the outer surface of the flange may come into contact with the tip of the water cup for forming a water column as a transmission medium of ultrasonic waves between the probe and the flange as the welded H-section steel is continuously transported. The shorter the distance between the distal end of the water cup and the outer surface of the flange, the better the flaw detection performance. During normal operation, the vertical run-out of the welded H-section steel is at most about 5 mm. Therefore, for example, if the separation distance is set to 6 mm, sufficient flaw detection performance can be obtained, and there is no problem of contact in normal times. However, the situation is different for the following abnormal states.

That is, in the case of a lightweight welded H-section steel, for example, as shown in FIG. 10, the material web coil is made continuous while performing transverse joint welding every certain length. When the material enters the ultrasonic flaw detector after the above, the material may enter, for example, in an upwardly bent state as shown in FIG. 11 depending on the shape characteristics (flatness, bending, warpage, etc.) of the material and the transverse welding conditions. At this time, the bent portion in the upwardly bent state may collide with the upper water cup in the fixed state, thereby damaging the water cup and making it impossible to detect flaws. Or, even if it is not damaged, the orientation of the water cup may be changed to cause a false detection.

Alternatively, as shown in FIG. 12, when the pinch rolls 15, 15 for transporting the web of the welded H-section steel are inclined, the balance for rolling down the web is not uniform in the vertical direction. Such contact can also occur by moving upward (in the illustrated example).

Accordingly, an object of the present invention is to detect a defective welding portion of a welded H-section steel, and particularly to prevent damage and erroneous detection of the flaw detection device even when the welded H-section steel moves up and down at a flaw detection position. And to enable high-accuracy and continuous ultrasonic flaw detection.

[0021]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an ultrasonic probe which is spaced apart from the outer surface of a flange of a continuously conveyed welded H-section steel. The ultrasonic beam from the probe is orthogonally incident on the flange using water as a propagation medium, and continuously ultrasonically flaw-detected. Providing a web restraining roller for regulating the pass line of the shaped steel, further moving the probe away from the flange outer surface only when the separation distance between the probe and the outer surface of the flange is out of an allowable range. When the probe returns to the range, the probe is returned to the original position.

For this purpose, specifically, an avoidance gate is provided in the time axis direction between the transmitted wave of the ultrasonic beam and the first surface wave, and a gap between the end of the avoidance gate and the first surface wave is provided. Provided as a non-operating area without a gate,
When the surface wave hits the avoidance gate, the probe is moved away from the outer surface of the flange, and thereafter, when the probe comes off the avoidance gate, the probe returns to its original position.

[0023]

[0024]

According to the present invention, the conventionally fixed probe is retracted when the vertical run-out in the pass line of the welded H-section steel is excessive. Accordingly, contact with the welded H-section steel can be prevented, and erroneous detection due to change in the direction of the water cup can be prevented even if damage and breakage of the probe and the water cup do not occur. Further, when the separation distance is restored within the proper range, the probe is returned to the initial position, so that the period during which the flaw detection accuracy is reduced or the flaw detection is disabled is short, and substantially continuous flaw detection can be performed.

By the way, in the case of the above-mentioned method, since the ultrasonic probe is temporarily retracted, ultrasonic inspection may not be performed during the retreat. Therefore, in the present invention, the distance between the ultrasonic probe and the outer surface of the flange is constantly kept within a certain range using the time-axis direction interval between the transmitted wave of the ultrasonic beam and the first surface wave as an index. Then, the ultrasonic probe is moved in the direction perpendicular to the flange while following the vertical movement of the welded H-section steel. Therefore, the ultrasonic flaw detection can be performed completely continuously without interruption while preventing the contact with the probe and the water cup.

Usually, in ultrasonic flaw detection of a welded portion, the distance between the ultrasonic flaw detection probe and the outer surface of the flange, that is, the so-called water distance, is the most important factor affecting the detection accuracy. By following and moving the flaw detection device, a constant water distance is constantly secured, so that flaw detection accuracy can be improved.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to the embodiments shown in the drawings. As shown in FIG. 4, in the present invention,
The upper flange 1F of a welded H-section steel (hereinafter referred to as a section steel) 1 which is continuously conveyed using a focus type probe 2A as a probe
Is positioned spaced by probe 2A in a central position of the _U, the ultrasonic beam is perpendicular to the incident the upper flange 1F _U water 4 as the propagation medium, to monitor the reflected echo.

Here, according to the present invention, the focus position of the focus type probe 2A is determined by using the probe 2A and the upper flange 1F.
_U The position between the outer surface, that is, within the water distance. This is intended to increase the effective flaw detection width of the ultrasonic beam from the probe 2A.

[0029] When the manufacturing inspection line section steel to which the present invention is applied will be explained with reference to FIG. 5, first conveyed upper and lower flanges 1F _U, was welded by the welder 11 and 1F _L and web 1W, the aforementioned pinch rolls While sending by 15,
Water cooling is performed in a water cooling zone (not shown), and thereafter, ultrasonic testing is performed by the ultrasonic testing device 12 according to the present invention. This ultrasonic flaw detection, for example, has a maximum line speed of 7
It is performed at a high speed of 0 m / min. In this case, since section steel 1 as described above have a deflection of more than 12mm to the left and right by the conveying, inspection position fixed and spaced at the central position of the flange 1F _U on the shaped steel 1 the probe 2A is It will be impossible.

Therefore, in the present invention, as shown in FIG. 6 and FIG.
A web constraining roller 6 is provided to abut on both sides of the web 1W of the section steel 1 to regulate the path line of the section steel. By installing the web restraining roller 6, the run-out of the shaped steel 1 is reduced to ±
It can be suppressed to a range of 0.5 mm, and the probe 2A can always monitor only the welding surface in the process of transporting the shaped steel 1.

[0031] In the present invention, the water 54 when used as a propagation medium of the ultrasonic beam, connecting between the flange 1F _U outer surface on the shaped steel 1 is continuously conveyed probe 2A For this purpose, as shown in FIG. 2, a water cup 10A is provided to form a local water immersion chamber, which is supplied with water at a rate of, for example, about 5 liters per minute, and a rectifier having a plurality of through holes therein as necessary. provided a plate (not shown), while escape bubbles generated in the water during upward, by discharging water from the discharge port of the lower end, the gap a of the discharge port and the upper flange 1F _U, for example, in 6～18Mm, A water column can be formed in the meantime. As described above, the ultrasonic probe 2A on the upper flange 1F _U side
It has been described, an ultrasonic probe 2B also lower flange 1F _L side are arranged in the same configuration.

Under the above conditions, the probes 2A, 2A
Flange 1F _U shape from steel B 1, reflected echoes of the ultrasonic beams incident on 1F _L is incorporated in the ultrasonic flaw detector 12, the threshold level 50 for example a predetermined
%, A defect determination signal is output as a reject level (defect), and a marking command can be issued to the defect marking device 13.

FIG. 1 shows an example of the arrangement of the probes 2A and 2B. That is, the post 20 is erected at the flaw detection position, and a pair of upper and lower holding arms 21A and 21B is disposed on the post 20. These holding arms 21A and 21B can be moved up and down by elevating means 23A and 23B including a motor and the like provided on the post 20. When the shaped steel 1 is transported on the transport roller table, the lower surface level of the shaped steel 1 is regulated by this, so that the problem of collision with the water cup 10B does not occur. ,
Elevation does not have to be performed.

Each of the holding arms 21A and 21B has
Probes 2A and 2B and water cups 10A and 10A, respectively
B are provided, and the support rods 22A, 22B are horizontally moved between a pass line shown in FIG. 1 and a calibration position (indicated by a virtual line) deviating therefrom. )). Note that the horizontal position adjustment of the section steel 1 may be performed by the web restraining rollers 6, 6,..., And the support rods 22A, 22B may be configured to be vertically movable.

When the excessively bent portion of the section steel 1 shown in FIG. 11 enters, or when the section steel 1 rises as shown in FIG.
A is raised retracted away a distance from the flange 1F _U outer surface by the elevating means 23A, then when returning within the allowable range, then the probe is lowered the upper retaining arms 21A returned to the original position is there.

[0036] In this case, the distance between the probe 2A and the flange 1F _U outer surface it is necessary to determine whether the allowable range, as a determination means, a distance meter according to the inspection position, for example a laser beam and disposed to staring the upper flange 1F _U outer surface, it can also be provided measuring means, such as measuring the distance from time until the reflected time of providing the length-measuring unit separately, costly It is most suitable to use the flaw detection device itself from the viewpoint that the flaw detection is connected.

[0037] That is, when sending an ultrasonic beam from a probe 2A, as shown in FIG. 3, after a lapse of time that is subsequent to the transmission wave, appear first surface wave reflected by the flange 1F _U outer surface, then In the case where there is a defect, a defect echo occurs at the defective gate portion. What appears next is the second surface wave. The dimensional relationship between FIGS. 2 and 3 is shown.

Therefore, in a preferred embodiment of the present invention, the avoidance gate G is provided in the time axis direction between the transmitted wave and the first surface wave, and the end between the avoidance gate G and the first surface wave is provided. It is provided as a non-operation area Z without a gate.

Under such a configuration, when the first surface wave moves leftward as shown by a broken line in FIG. retracting the upper holding arm 21A upward away from the flange 1F _U outer surface. Thereafter, when the first surface wave comes off the avoidance gate G, the probe 2A is returned to the initial position.

[0040] More specifically with more specific numerical values of this operation, when the first surface wave is applied to avoid the gate G by the lifting of Katachiko 1 during testing, away the probe 2A from the flange 1F _U outer surface Upper holding arm 21A
Is raised by 10 mm. The avoidance time is 3 seconds,
After the elapse of the avoidance time, it returns to the original position. If the first surface wave still hits the avoidance gate G even if it is avoided by rising by 10 mm, it is further raised by 10 mm, and as a result, 20 mm
Rise. In this way, the avoidance is performed with the avoidance length of 10 mm pitch and the avoidance holding time of 3 seconds.

By the above operation, it can be said that the necessary and sufficient continuous flaw detection for defect location detection is achieved. However, when a large vertical movement occurs during the transportation of the shaped steel 1 and the probe 2 is avoided, In the above method, the distance between the probe 2 and the surface of the shaped steel 1 becomes too large, so that flaw detection becomes impossible.

[0042] Therefore, in the present invention, in order to realize the ultrasonic flaw flaw rate of 100% over the entire length of the shaped steel 1, for example the distance between the ultrasonic probe 2A and the upper flange 1F _U outer surface Under the most appropriate condition, an allowable swing width f is set from the reference point, for example, with reference to the interval in the time axis direction between the transmitted wave of the ultrasonic beam and the first surface wave in the echograph, and the second When the generation time P of the surface wave is [(c−
f) to c) so as to fall within the range of
Are moved in the orthogonal direction of the flange 1F _U, always with to keep a certain range the distance between the ultrasonic probe 2A and the upper flange 1F _U outer surface, the ultrasonic probe 2B the flange 1F _L Move so that the separation distance is kept constant.

More specifically, the shape steel 1
Under There When moved upward, the distance between the ultrasonic probe 2A and the upper flange 1F _U outer surface disposed on the upper side approaches, an ultrasonic probe 2B disposed on the lower side distance between flange 1F _L outer surface is would be receding, when became that the the amplitude exceeds the allowable fluctuation range f moves the holding arm 21A upward, water cup 1
0A or the probe 2A is prevented from contacting, and the separation distance is kept within a predetermined range. Further, the holding arm 21B to keep a predetermined range even if the distance between the moving amount and the same amount corresponding moves upward ultrasonic probe 2B and the lower flange 1F _L outer surface of the holding arm 21A. It is preferable that the allowable swing width f is, for example, about 5 to 10 mm.

The operation will be described in a control manner.
A always emits ultrasonic waves (transmitted waves),
The probe 2A senses the transmitted wave and the first surface wave returned from the surface of the section 1. The transmitted wave emitted by the probe 2 </ b> A and the sensed first surface wave are signalized and transmitted to the flaw detector 51. The flaw detector 51 processes the transmitted signal and transmits it to the position control sequencer 52. The position control sequencer 52 manages, based on the transmitted signal, whether or not the separation distance between the oscillation wave and the first surface wave is within an allowable range, and deviates from the range of the allowable swing width f. time, the drive signal to the drive means 23A is emitted from the position control sequencer 52, the ultrasound by the movement of the upper holding arm 21A so as to keep the distance between the ultrasonic probe 2A and the upper flange 1F _U outer surface in a predetermined range The probe 2A is moved up and down. At the same time, a drive signal is also issued from the position control sequencer 52 to the driving means 23A, and the lower holding arm 21B is moved in conjunction with the upper holding arm 21A and the vertical movement.
Is moved. Note that the movement control of the ultrasonic probe 2B may be independent control based on the measured ultrasonic waveform. When the section steel 1 is transported on the roller table, the lower holding arm 21B does not need to move up and down.

Thus, even when the profiled steel 1 moves up and down greatly, the distance relationship between the profiled steel 1 and the probe 2 is always properly maintained within a certain range, and the ultrasonic flaw detection can be performed without interruption. Ultrasonic flaw detection is performed over 100% of the entire length of steel 1.

On the other hand, as another following means of the present invention, FIG.
As shown in FIG. 2, the water cup 10 is provided on the support rod 22 via a spring 30 so as to be able to move up and down. The water cup 10 is provided with connecting arms 31 in the front and rear direction of the line, and copying rollers 32 and 32 are provided at both ends thereof. This copying roller 3
2, 32 can follow the flange 1F while contacting the outer surface. Even with such a retreat means, the shape steel 1
Can be prevented from colliding with the water cup.

(Embodiment 1) Next, the method of the present invention in which the probe is moved upward when the first surface wave hits the avoidance gate, and a comparative method (method described in Japanese Patent Publication No. 2-15020)
And comparative evaluation was performed. Table 1 shows the results.

[0048]

[Table 1]

As can be seen from Table 1, the comparative method was an intermittent flaw detection with an effective flaw detection width of 0.6 mm, while the method of the present invention was able to expand the effective flaw detection width to 1.2 mm, making continuous flaw detection possible. It becomes possible. Further, the flaw detection area ratio was improved to about eight times that of the comparative method.

On the other hand, as dimensions shown in FIG.
Under the flaw detection conditions of b = 10 mm, c = 20 mm, and e = 10 mm,
The time from the transmission of the ultrasonic beam to the generation of the avoidance output signal to the lifting / lowering means of the holding arm is 0.01 seconds, and the time from the avoidance output signal to the actual start of the avoidance of the holding arm is 0.1 seconds. The avoidance pitch was 10 mm and the avoidance holding time was 3 seconds.

As a result, in the conventional water cup fixing mode, the number of times of contact of the shaped steel was 37 times / month, and the number of times of water cup breakage and deformation was 1.5 times / month. , And both of them were gone.

(Example 2) Next, the following test was conducted. Artificially shaped steel welds at multiple locations (AH)
To form welding defects having different defect lengths (2-4 mm),
As shown in FIG. 13, as shown in FIG. 13, welding defects are detected by adjusting the transfer device when the vertical movement is conveyed within 5 mm (line) and when it is conveyed within 20 mm (line). did. The conveying speed was 30 m / min, and the size of the test section steel was 20 m / min.
It is 0x100x3.2x4.5mm (SS400). Under these conditions, the allowable deflection width f is set to 5 to 10 mm, and the probes 2A and 2B and the water cup 10 are made to follow the vertical movement of the shaped steel.
A and 10B were moved. Note that the flaw detection sensitivity condition was set at 50% for the 2φ hand bottom hole.

Under the above conditions, the difference between the flaw detection echo heights was evaluated under the two types of transport conditions.
The result is shown in FIG.

As can be seen from FIG. 14, the same echo height was obtained irrespective of the magnitude of the vertical movement change of the section steel. That is, in the present embodiment, it can be said that regardless of the magnitude of the vertical movement of the section steel, it is possible to always reliably detect a flaw in a welding defect.

In this embodiment, the holding arms 21A and 21B smoothly follow the up and down movement of the section steel, and there is no contact between the water cups 10A and 10B and the section steel 1. Furthermore, as a result of comparing the defect detection rate with the fixed probe and the defect detection rate in the present example, when the probe was fixed, the defect detection rate was about 70% due to the separation and proximity to the flange surface. In this embodiment, a detection rate of 100% has been obtained. Note that the defect detection rate = (the number of detected defects / the total number of artificial defects) × 100.

[0056]

As described above, according to the present invention, when flaw detection is performed on a defective welded portion of a welded H-beam, the probe is immediately evacuated when the welded H-beam goes up and down abnormally, particularly at the flaw detection position. After the abnormal condition ends, return the probe quickly to its normal position, or move the probe in a manner that follows the vertical movement of the shaped steel, thereby preventing damage to the flaw detection device and preventing false detection. This makes it possible to perform ultrasonic flaw detection.

[Brief description of the drawings]

FIG. 1 is a schematic view on a cross section orthogonal to a line direction showing an entire example of a flaw detector according to the method of the present invention.

FIG. 2 is a diagram showing a relationship between a probe, a water cup, and a section steel.

FIG. 3 is a waveform diagram of an ultrasonic echo level in a time axis direction.

FIG. 4 is an explanatory diagram of a propagation state of an ultrasonic beam.

FIG. 5 is a perspective view of a main part of a production line for a lightweight welded H-section steel.

FIG. 6 is a cross-sectional view showing an installed state of a web restraining roller according to the present invention.

FIG. 7 is a front view thereof.

FIG. 8 is an explanatory diagram of a flaw detection range.

FIG. 9 is a front view of another example of the retracting means of the present invention.

FIG. 10 is a schematic perspective view for explaining a cross connection of a web coil.

FIG. 11 is an explanatory diagram showing an example of collision of a lightweight welded H-section steel with a water cup.

FIG. 12 is an explanatory diagram of a shaft shift of a pinch roll.

FIG. 13 is a graph showing the amount of vertical movement and the amount of movement in the flow direction of a section steel in Example 2.

FIG. 14 is a graph showing the flaw detection echo height in Example 2 and under the conditions.

FIG. 15 is an explanatory view showing a conventional flaw detection method.

FIG. 16 is an explanatory view showing a conventional flaw detection method.

FIG. 17 is a plan view of another example.

FIG. 18 is a plan view showing a flaw detection range in FIG. 16;

FIG. 19 is an explanatory diagram showing an example of a method performed to complete the present invention.

[Explanation of symbols]

1: welded H-section steel, 1F: flange, 1W: web, 2 ...
Focus type probe, 4 water, 10 water cup, 12 flaw detector, 15 pinch roll, 21 holding arm, 22 holding rod, 23 driving means, 51 flaw detector, 52 position control sequencer .

Claims (1)

(57) [Claims] An ultrasonic probe is disposed at the center of a flange of a welded H-section steel that is continuously conveyed and spaced apart from the outer surface of the flange, and an ultrasonic beam from the probe propagates water. As a medium, it is orthogonally incident on the flange and continuously performs ultrasonic flaw detection, and a web restraining roller is provided which abuts on both sides of the web of the welded H-section steel and regulates a pass line of the welded H-section steel. An avoidance gate is provided in the time axis direction between the transmitted wave of the sound beam and the first surface wave, and a non-operating region having no gate is provided between the end of the avoidance gate and the first surface wave. A welding H-shape characterized by moving the probe away from the outer surface of the flange when the first surface wave hits the avoidance gate, and thereafter returning the probe to its original position when it comes off the escape gate. Ultrasonic testing of steel welds.