JPS6239706B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an ultrasonic flaw detection device that detects flaws in welded pipes using a vertical probe and an oblique probe. The present invention provides an ultrasonic flaw detection device for welded pipes that has a function of changing the defect determination level.

For steel pipes such as ERW pipes that are directly welded in the longitudinal direction of the pipe, the steel strip is generally uncoiled into a coil, conveyed continuously to a pipe-making line, bent into a round shape by a pipe-making machine, and then joined. Automatically manufactured by high frequency welding of parts.

Incidentally, the spread of ultrasonic flaw detection in the quality control of ERW pipes has become extremely popular, and it has become essential for product quality assurance. It is necessary to detect welding defects by using ERW and to detect lamination defects by vertical ultrasonic testing of the base material of ERW steel pipes.

Conventionally, in the ultrasonic flaw detection method for ERW pipes, the base material is tested using a vertical probe in the state of the steel strip before pipe making, and the welded part is detected obliquely by moving the ERW pipe in the longitudinal direction without rotating it. The first flaw detection method involves placing the angle probe over the welding line for flaw detection, and the other involves rotating the vertical probe and angle probe around the welded ERW tube without rotating the ERW tube. There is a second flaw detection method in which the base metal part and the weld line are scanned in a spiral manner by sending the weld in the longitudinal direction.

However, in the first flaw detection method described above, an ultrasonic flaw detector to detect flaws in the base material and an ultrasonic flaw detector to detect flaws in the welded part are required at different locations on the pipe production line, which reduces the equipment cost and installation space for the flaw detector. becomes large.
Furthermore, since the base material before pipe making is a plate material that has been uncoiled, the plate is subject to significant bending and vibration, and in order to perform precise flaw detection, various equipment such as pinch rolls is required to improve the properties of the plate. On the other hand, in the second flaw detection method, flaws can be detected using a single rotary contact type flaw detector that scans the ERW pipe after tube formation in a spiral pattern by rotating a vertical probe and an angle probe. When detecting flaws in the base metal using a vertical probe, there is a risk of erroneous detection of flaws in the weld line due to the shape of the weld and the unevenness of the cut surface of the weld. Furthermore, in weld line flaw detection using an angle probe, there is a problem in that the presence of minute inclusions in the base metal deteriorates the defect discrimination ability for detecting even the minute inclusions.

Therefore, good products are also sorted out as defective products, requiring equipment and personnel for re-inspection, resulting in a problem of deterioration of manufacturing efficiency.

This invention was made to improve these conventional problems, and its feature is that in a rotating probe type ultrasonic flaw detection device, a vertical probe and an oblique probe can be used. A detector that detects the ultrasonic beam scanning position, a detector that detects the position of the weld line of the welded pipe, and the output of the two detectors determines the ultrasonic beam of the vertical probe and the angle probe. A determination device for determining whether the scanning position is in the base metal portion of the welded pipe or the weld line is provided, and the defect determination levels for the base metal portion and the weld line are changed respectively based on the output of the determination device. be.

An embodiment of the present invention will be described in detail below with reference to FIGS. 1 to 3.

FIG. 1a is a block diagram of an ultrasonic flaw detection apparatus for a welded pipe showing an embodiment of the present invention, and FIG. 1b is a diagram showing the relationship between the welded pipe and a probe.

In Figures 1a and b, 1 is a welded pipe that is sent in the direction of arrow a without rotating, 2 is the base material of the welded pipe 1, 3 is a weld line in the longitudinal direction of the welded pipe, and 4 is the hollow part of the welded pipe as described above. This is a rotating mechanism in which the welded tube 1 passes through and rotates around a fixed member 5 via a bearing 6. A vertical probe 7 and an angle probe 8 are attached at a predetermined interval to this rotating mechanism. The tentacles 7, 8 are arranged so as to be able to rotate around the welded pipe 1 in the direction of the arrow 9. The vertical probe 7 detects lamination defects 10 in the base material by vertically injecting an ultrasonic beam into the welded pipe 1 as shown by the dotted line A, and the oblique probe 8 As shown in FIG. 1, an ultrasonic beam is incident at an oblique angle into a welded pipe 1 to detect row-shaped defects 11 such as poor welding. 12 is a probe rotation angle detector attached to the fixed member 5, and this detector 12 is attached to the rotation mechanism 4,
It is combined with a disk 13 that has one protrusion per revolution and 360 gear-like protrusions to generate a pulse P every rotation of the probe, and a pulse P every 1/360 revolution of the rotation angle. /360. Reference numeral 14 denotes a welded pipe detector that is attached to the rotating mechanism 4 and rotates around the welded pipe 1 in the same way as a probe to detect the deflection of the welded line 3 in the pipe circumferential direction. It is turned on during scanning and generates output 15. Note that as this weld line detector 14, an eddy current detector is normally used. 16 is the output P of the probe rotation angle detector 12
Then input P/360 and the output 15 of the welding line detector 14 to check whether the ultrasonic beams of the vertical probe 7 and the angle probe 8 are scanning the base material 2 or scanning the welding line. This is a defect determination level converter that outputs defect determination levels L and N that are switched to two levels depending on whether the defect determination level L or N is being output. Also, this converter 1
6 corrects the difference in tube circumferential position between the welding line detector 14, the vertical probe 7, and the oblique angle probe 8 by counting the output P of the rotation angle detector 12 and 1/360P, and also adjusts the above defect judgment level. The switching is controlled at the timing when the ultrasonic beams from each of the probes scan the weld line section. 17 supplies transmission pulses to the bevel probe 8 via the rotary transformer 18, receives and amplifies the defect echo signal detected by the bevel probe 8 via the rotary transformer 18, and determines the magnitude of the defect echo. A transmitter/receiver 19 for angle angle flaw detection generates an analog output VL proportional to A transmitter/receiver for vertical flaw detection receives and amplifies the signal via a rotary transformer 18 and generates an analog output VN proportional to the size of the defect echo. 20 is a transmitter/receiver for oblique flaw detection where the analog output VL of the transmitter/receiver 17 is used for defect determination. Defect level determiner for angle angle flaw detection that determines that there is a defect when level L or higher, 2
1 is the analog output of the transceiver 19 for vertical flaw detection
A defect level determiner 22 for vertical flaw detection determines that there is a defect when VN is equal to or higher than the defect determination level N, and a defect level determiner 22 inputs the outputs of the two defect level determiners 20 and 2 to select pass/fail for the welded pipe 1 and determine the defect location. This is a processing unit that records and displays markings, defects, etc.

Next, the defect determination level converter 1 shown in FIG.
The specific configuration and operation of 6 will be explained with reference to FIGS. 2 and 3.

FIG. 2 is a block diagram showing an example of the defect determination level converter 16 which is a feature of the present invention, and FIG. 3 is a block diagram showing the ultrasonic beam positions of the angle probe 8 and the vertical probe 7 and the position of the weld line 3. FIG.

In FIGS. 2 and 3, the rotation angle generation counter 23 indicates the output pulse of the probe rotation angle detector 12.
After receiving PP/360, the counter is reset to zero by the output pulse P, and then the output pulse P/360 is counted to generate a probe rotation angle signal A based on the circumferential position of the rotation angle detector 12. Weld line position generator 24
is the center of the weld line shown in FIG. 3 by the weld line detector 14.
By inputting the output of the rotation angle generation counter 23 using the pulse signal 15 generated when the B ₀ point is detected and storing it until the center passes through the center B ₀ point again, the deflection in the circumferential direction of the pipe due to the pipe running of the weld line can be reduced. It is now being detected. Adder 25 and subtracter 26
is a device that inputs the output B ₀ of the welding line position generator 24 and outputs signals corresponding to both end positions B ₁ and B ₂ of the welding section, and as shown in FIG.
When the area of widths △ ₁ and △ ₂ with respect to B ₀ is defined as a welding area, the adder 25 has B ₀ + △ ₂ and the subtracter 2
6 calculates B _{0 -Δ1} and generates position signals B ₁ and B ₂ , respectively. The first scanning position generator 27 inputs the probe rotation signal A and generates a circumferential scanning position signal of the beam from the vertical probe 7.
It generates AN and has a function to correct the position of the weld line detector 14 and the vertical probe 7 in the tube circumferential direction. If the pipe circumference differs by 180 degrees, AN=A+
It is designed to add 180. The second scanning position generator 28 receives the probe rotation angle signal A and generates a circumferential scanning position signal AL of the beam from the angle probe 8. For example, as shown in FIG.
When the bevel probe 8 and the weld line detector 14 are located at the same circumferential position as shown in FIG. Since the angle θ differs from the angle θ, the scanning position signal AL is output by subtracting A−θ.

The first comparator 30 compares the output B ₂ of the adder 25 with the output AN of the first scanning position generator 27;
Only when the comparison result is AN< _B2 , a high level (or low level) signal is output to the first AND circuit 34, and the second comparator 31 outputs the output _B1 of the subtracter 26 and the 1 and the output AN of the scanning position generator 27, and when the comparison result is AN>B ₁
High level (or LOW level) signal is the first
The output signal is output to an AND circuit 34.
The first AND circuit 34 operates so that the outputs of the first and second comparators 30 are both at High level (or Low level).
level), that is, when B ₁ < AN < B ₂ , the gate is opened and a high level (or low level) signal is output, and the first switch S ₁ is used to determine the welding part from the base metal determination level generator 36 side. The switch is made to the level generator 37 side.

The third comparator 32 is connected to the second scan position generator 28
The output AL of the adder 25 is compared with the output _B2 of the adder 25, and the fourth comparator 33 compares the output AL of the adder 25 with the output B2 of the adder 25.
When the output AL of the subtracter 26 is compared with the output B ₁ of the subtracter 26, and the respective comparison results are AL<B ₂ and AL>B _1.
High level (or LOW level) signal to the second
The output signal is output to an AND circuit 35.

This second AND circuit 35 opens the gate when the outputs of the third and fourth comparators 32 and 33 are both at High level (or Low level), that is, B ₁ < AL < B _{2 .} ) is output to the second switch S ₂ to switch the second switch S ₂ from the base metal determination level generator 38 side to the weld zone determination level generator 39 side.

The first and second switches S ₁ and S ₂ are normally connected to the base metal judgment level generators 36 and 38, and the first and second AND circuits 34,
The judgment level signal is controlled by the output of 35.
LN is output to defect level determiners 20 and 21, respectively.

The defect determination level of the welded part in vertical flaw detection is set to a high level that does not cause malfunction due to irregularities caused by weld overfill, etc., and the defect determination level of the base metal part in oblique flaw detection is set to a high level that does not cause malfunction due to irregularities caused by welding excess. is set to a high level that does not detect it.

As described above, the ultrasonic flaw detection device of the present invention changes the defect determination level depending on whether the ultrasonic beams of the vertical probe and the oblique probe scan the melt line or the base material excluding the weld line. Since the signal processing obtained by the vertical probe can be used to collect defect data on the weld line, the signal processing obtained by the oblique probe can be used to collect defect data on the base material excluding the weld line. Each can be masked. Therefore, by masking the weld line during vertical flaw detection, false detections due to shape changes at the weld line can be eliminated.
In addition, in oblique flaw detection, by masking the base metal except for the weld line, minute inclusions in the base metal are not detected, allowing efficient flaw detection.

In the above embodiment, as a method for detecting the position of the weld line, for example, an eddy current detector is provided at a rotating position integral with the probe, and the position of the weld line is detected while rotating around the weld pipe. However, the present invention is not limited to this, and there are various methods including, for example, a method of detecting a weld line protrusion using an outer surface echo of a vertical probe.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an ultrasonic flaw detection device for welded pipes showing an embodiment of the present invention, Fig. 2 is a block diagram showing a defect judgment level converter which is a feature of the present invention, and Fig.
The figure is a diagram for explaining the positional relationship between the weld line and the probe. In the figure, 1 is a welded pipe, 2 is a base metal part, 3 is a weld line, 4 is a rotation mechanism, 7 is a vertical probe, 8 is an oblique angle probe, 12 is a probe rotation angle detector, and 14 is a 16 is a defect determination level converter; 20 is a defect level determiner for oblique flaw detection; and 21 is a defect level determiner for vertical flaw detection. It should be noted that the same or corresponding parts in the figures are indicated by the same reference numerals.

Claims (1)

[Claims] 1. A welded pipe in which the welded pipe is scanned in a spiral manner by a vertical probe and an oblique probe installed in a rotating mechanism that rotates around the welded pipe that is fed in the longitudinal direction without rotating. The ultrasonic flaw detection apparatus includes a first detection means for detecting the weld line position of the welded pipe, and a rotation angle of the vertical probe and the oblique probe to detect the ultrasonic beam position with respect to the welded pipe. The ultrasonic beams of the vertical probe and the oblique probe scan the weld line or the base material based on the outputs of the second detection means and the first and second detection means. a signal obtained by a vertical probe; An ultrasonic flaw detection device for welded pipes, characterized in that defect data of the weld line is masked during processing, and defect data of the base metal portion is masked during signal processing obtained by an angle probe. .