JPH0727551A - Tube inner shape inspecting device - Google Patents

Abstract

PURPOSE:To accurately measure the shape (bead shape) of a weld section 6 exposed on the inner periphery of a tube body 5 from the outer periphery with ultrasonic waves. CONSTITUTION:A pair of angle beam probes 7a, 7b transmitting ultrasonic pulses toward a weld section 6 exposed on the inner periphery and receiving the reflected waves are arranged at opposite positions across the weld section 6 on the outer periphery of a tube body 5. Transmission pulses are applied to the angle beam probes 7a, 7b at a constant period from a pair of ultrasonic transceiver sections 9a, 9b, echo signals are received, and the received echo signals are averaged over multiple periods by synchronizing/adding/averaging means 10a, 10b. Different measuring periods for the averaged echo signal are specified by gate means 11a-11d, and the echoes caused by the weld section 6 on the inner periphery contained in the specified measuring periods are detected by echo detecting means 12a-12d. The weld shape on the inner periphery is specified by an inner shape specifying section 13 based on the detected echoes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses ultrasonic waves from the outer peripheral surface of the shape of the welded portion (beat shape) exposed on the inner peripheral surface of the tubular body in the production line of electric resistance welded pipes in, for example, a steel factory. The present invention relates to a pipe shape inspection device for inspecting.

[0002]

2. Description of the Related Art Generally, an electric resistance welded pipe is manufactured by rolling a strip-shaped steel plate while traveling and continuously electric resistance welding the abutting portions of the steel plates along the pipe axial direction. Therefore, if the welding is left as it is, the welded portion having unevenness is exposed on the outer peripheral surface and the inner peripheral surface of the manufactured electric resistance welded pipe, and thus the raised portion of this welded portion, that is, the weld bead is cut with a beat cutting machine. Then, a step of flattening the surface of the welded portion is required.

In this case, it is very important for the quality of the manufactured product to perform cutting so that no weld bead is left. Therefore, in the ERW pipe production line, the cutting condition of the welding bead in the bead cutting machine is detected, and the cutting condition is returned to the bead cutting machine to make the welded portions of the outer peripheral surface and the inner peripheral surface flatter. It controls the cutting operation of the bead cutting machine.

The cutting state of the weld bead of the welded portion exposed on the outer peripheral surface can be grasped relatively easily by visual inspection or an optical technique such as a camera. However, it is not possible to easily grasp the cutting state of the weld bead of the weld exposed on the inner peripheral surface.

The following three types have been proposed to date as typical methods for externally detecting the concavo-convex state of the welded portion exposed on the inner peripheral surface. (1) Contact method (Japanese Utility Model Laid-Open No. 58-24062) In this contact method, an inner cutter attached to the tip of a rod that is projected from the front side of the welding position toward the rear side of the welding position. A contact sensor for detecting the shape of the inner surface is provided in the vicinity of to detect the uneven state of the exposed welded portion. (2) Ultrasonic Thickness Gauge Method (JP-A-56-35057) In this ultrasonic thickness gauge method, as shown in FIG. Attach the child 2,
The thickness t of the tubular body 1 is measured by making ultrasonic waves enter the tubular body 1 in the vertical direction (radial direction). Then, the vertical probe 2 is moved in the circumferential direction D while measuring the thickness t. Then, as shown in FIG. 13B, if the uneven portion 3a caused by the welded portion 3 exists on the inner peripheral surface, it appears as a change in the thickness t. (3) Ultrasonic array probe method (JP-A-2-11411)
No. 4) In this ultrasonic array probe method, FIG.
As shown in FIG. 3, a pair of array probes 4a and 4b are arranged on the outer peripheral surface of the tubular body 1 at opposite positions with the welded portion 3 interposed therebetween. Then, while sequentially vibrating each transducer forming the one array probe 4a to make an ultrasonic pulse enter,
By scanning the transducers of the other array probe 4a in synchronization, the transducers that have received the ultrasonic waves from the transducers on the transmission side are identified, and the reflection of the ultrasonic waves on the inner peripheral surface is performed. Detect the position. By performing this from both array probes 4a and 4b, the unevenness of the welded portion exposed on the inner peripheral surface is grasped.

[0006]

However, the above-mentioned methods (1) to (3) still have the following problems to be solved. First, in the contact method (1), since it is necessary to insert the contact sensor into the tube body 1, it is difficult to apply it to the tube body 1 having a small diameter. In addition, the contact sensor is likely to be contaminated by pits and chips generated during welding, which may reduce measurement accuracy and reliability.

Next, in the ultrasonic thickness gauge system (2),
In order to use the ultrasonic thickness gauge, it is necessary to interpose water or the like between the probe 2 and the tube body 1. However, in the vicinity of the bead cutting machine, since the temperature of the welded portion 3 just welded is 300 ° C. or higher, it is impossible to acoustically contact the contactor 2.

If a large amount of water is used as a countermeasure against this, the welded portion 3 is rapidly cooled, so that the structure of the welded portion 3 changes and the quality of the material of the tubular body 1 deteriorates. Further, when the probe 2 is arranged at a position far away from the bead cutting machine in the axial direction of the pipe body 1, the circumferential position of the welded portion 3 may fluctuate (twist).
This method cannot be adopted either.

Further, in the ultrasonic array probe method (3), if the shape of the welded portion on the inner peripheral surface is inclined as shown in FIG. There arises a problem that the receiving array probe cannot detect the corresponding ultrasonic wave. In addition, this method requires array probes 4a and 4b having many channels and a multi-channel ultrasonic wave transmitting / receiving unit, which may significantly increase the manufacturing cost of the entire apparatus.

The present invention has been made in view of the above circumstances, and by using only a pair of beveled probes, it is possible to apply a tubular body having a small diameter and in the vicinity of a bead cutting machine. It is an object of the present invention to provide an in-pipe shape inspection device that can be installed in a pipe and can detect the shape of a welded portion on the inner peripheral surface reliably and accurately with low manufacturing cost.

[0011]

In order to solve the above-mentioned problems, in the pipe shape inspection apparatus of the present invention, the pipe inner shape inspection device is arranged at opposite positions on the outer peripheral surface of the pipe body with the welded portion interposed therebetween and is exposed to the inner peripheral surface. A pair of bevel probes for transmitting ultrasonic pulses and receiving reflected waves in the direction of the welded part, and transmit pulses are applied to each bevel probe at a constant cycle and echo signals are received. A pair of ultrasonic transceivers, a pair of synchronous averaging means for averaging the received echo signals over a plurality of cycles,
A plurality of gate means for designating different measurement periods in the averaged echo signal, a plurality of echo detection means for detecting echoes caused by the welded portion of the inner peripheral surface included in the designated measurement period, and detected. An inner surface shape specifying portion that specifies the welding shape of the inner peripheral surface based on each echo.

Further, in the invention of claim 2, the inner surface shape specifying portion has a welding shape type judging means for judging the kind of the welding shape based on the combination of the echo detection presence / absence information in each echo detecting means. .

Further, according to the invention of claim 3, in addition to the above-mentioned welding shape type determining means for the inner surface shape specifying portion, the radius of the welding shape is determined from the echo height of the echo detected by each echo detecting means. Radial dimension calculating means for calculating the directional dimension is added.

Further, in the invention of claim 4, in addition to the welding shape type determining means and the radial dimension calculating means described above, each echo detecting means is a beam for detecting the beam path length of the ultrasonic pulse to the detected echo. It has a path length detecting means, and a circumferential dimension calculating means for calculating the circumferential dimension of the welded shape from each detected beam path length is added to the inner surface shape specifying portion.

Further, in the invention of claim 5, the synchronous averaging means is an A / D converting means for converting an echo signal received by the ultrasonic wave transmitting / receiving section into a digital echo signal, and an A / D converting means. A first signal memory for always storing the latest predetermined number of echo signals sequentially output from the means, a second signal memory for storing one added echo signal, and a latest signal memory for the first signal memory. A signal reading means for reading a predetermined number of echo signals written ahead of the echo signals, an echo signal sequentially output from the A / D conversion means, and an addition echo signal read from the second signal memory are added. The addition unit, a subtraction unit that subtracts one echo signal read by the signal reading unit from the addition echo signal output from the addition unit, and the addition echo signal output from the subtraction unit is used as a second signal memo. An addition echo signal updating means for writing as a new addition echo signal to the dividing unit, a division unit for dividing the addition echo signal output from the subtraction unit to obtain an averaged echo signal, and an averaged echo signal for analog It is composed of D / A conversion means for converting into an echo signal.

[0016]

The operation principle (function) of the pipe shape inspection device thus configured will be described. The bevel probes are arranged at opposite positions on the outer peripheral surface of the pipe body with the welded portion interposed therebetween. Then, each of the bevel probes transmits the ultrasonic pulse not at a right angle (radial direction) to the tubular body but at a constant directivity angle toward the weld portion exposed on the inner peripheral surface. Therefore, if there is no unevenness in the welded portion exposed on the inner peripheral surface, the reflected wave of the transmitted ultrasonic pulse is not received. Therefore, in this case, the echo signal output from the ultrasonic wave transmission / reception unit connected to this bevel probe does not include an echo. If the welded portion exposed on the inner peripheral surface has irregularities, the bevel probe receives the echo reflected at the portion of the shape of the weld facing the bevel probe.

Similarly, in the bevel probe arranged on the opposite side of the welded portion, if there is a portion facing the bevel probe of its own in the welded portion of the inner peripheral surface, this portion Receive the echo from.

Even in the shape of one welded portion exposed on the inner peripheral surface, since the incident direction of the ultrasonic pulse is different, the unevenness of the welded portion always faces either one of the oblique angle probes. An inclined surface is formed, and each echo corresponding to the inclined surface facing each welded bevel probe is received by each bevel probe.

If each echo signal received by each ultrasonic transmitter / receiver is divided into a plurality of measurement periods, which part of the welding shape each measurement period corresponds to is uniquely determined. Therefore, the welding shape can be specified to some extent by detecting the echo of each measurement period in each echo signal.

Further, the S / N ratio of the echo signal output from the ultrasonic wave transmitting / receiving section is increased by using the synchronous averaging means. That is, for example, when performing an online inspection while moving the tubular body in the axial direction, it is possible to remove electrical noise caused by the ultrasonic wave transmitting / receiving unit and noise caused by crystal grain boundaries and surface structure of the material of the tubular body.

Further, the same type of welded shape having irregularities continues for a certain length or more in the axial direction of the pipe body, and the defect is shorter than the welded shape. Therefore, by averaging the echo signals, it is caused by the defect. By reducing the proportion of echoes, only echoes due to the welded shape can be detected with a high S / N.

According to the second aspect of the present invention, when the welded portion exposed on the inner peripheral surface has one inclined surface, the echo is received only by the bevel probe facing the inclined surface. ,
No echo is received by the bevel probe that does not face the inclined surface. On the other hand, when an echo is detected by the gate means in each measurement period for each measurement period, a general generation position range of the welded part is specified for the echo.

Therefore, when one inclined surface exists in the welded portion, the inclination direction of this inclined surface and the approximate position in the welded portion are specified. As a result, the type of welding shape such as in which direction the inclined surface is inclined can be specified according to the combination of the presence or absence of echo detection in each echo detecting means.

According to the third aspect of the invention, since the ultrasonic pulse propagates in the tube with a constant directivity angle, the energy of the reflected ultrasonic pulse is also increased if the area of the inclined surfaces facing each other is widened. growing. Therefore, the echo height (signal level) of the echo detected at a particular measurement time of a particular bevel probe is the area of the opposing inclined surface, that is, the radial dimension of the welding shape of the inner peripheral surface. Correspond.

In the invention of claim 4, the beam path of the ultrasonic pulse of the echo detected at each measurement time is from the bevel probe which transmits the ultrasonic pulse to the inclined surface corresponding to the echo. Corresponds to the distance. Since the position of the bevel probe is known, the position of the corresponding inclined surface of the welding shape on the inner peripheral surface is specified. Therefore, the circumferential dimension of the welded shape can be calculated.

Therefore, according to the invention of claim 4, the type of the welded shape, the radial dimension and the circumferential dimension on the inner peripheral surface of the inspection object are specified. Further, in the invention of claim 5, since the synchronous addition averaging means is realized by digital processing, the averaging processing can be performed at high speed without time delay.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of the in-pipe shape inspection device of the embodiment. For example, the tubular body 5 such as an electric resistance welded pipe is transported by an unillustrated transport mechanism in the axial direction orthogonal to the paper surface, while the exposed portion 6a of the outer peripheral surface and the exposed portion 6b of the inner peripheral surface of the welded portion 6 are not shown in the bead cutting. Machine cut.

An in-pipe shape inspection device for inspecting the welded shape of the exposed portion 6b (welding bead) of the welded portion 6 on the inner peripheral surface of the pipe body 5 that has been cut is disposed near the discharge port of this bead cutting machine. . As shown, the welded portion 6 on the outer peripheral surface of the pipe body 5
A pair of oblique angle probes 7a and 7b are arranged at opposite positions sandwiching. Specifically, the bevel probes 7a and 7b are attached to the outer peripheral surface of the tube body 5 by a local water immersion contact method. The transducers 8a and 8b in the oblique angle probes 7a and 7b are adjusted in angle so that the propagation directions of the ultrasonic pulses Pa and Pb pass through the center position of the inner peripheral surface of the welded portion 6.

A transmission pulse is applied to each of the oblique angle probes 7a and 7b from the ultrasonic wave transmitting / receiving sections 9a and 9b having the same configuration at a constant period T ₀ , and the transmission pulse is applied to the transducers 8a and 8b. As a result, the ultrasonic pulses Pa and Pb are incident on the tubular body 5. When there is a defect in the tube body 5 or there is unevenness in the welded portion 6 on the inner peripheral surface, each of the beveled probes 7a and 7b causes echoes reflected by these to be transmitted to the transducers 8a and 7b.
The ultrasonic wave is received at 8b and sent as echo signals a and b to the corresponding ultrasonic wave transmitting / receiving sections 9a and 9b.

That is, each ultrasonic pulse Pa, Pb is
As shown in FIG. 2A, it has a directivity of an angle θ,
It spreads within this angle θ and propagates. Therefore, the bevel probe 7a of the welding shape of the exposed portion 6b on the inner peripheral surface,
The reflected wave (echo) from each inclined surface facing 7b is received. Therefore, the echo signals a and b output from the bevel probes 7a and 7b include two echoes, an echo from the front inclined surface and an echo from the rear inclined surface, or more echoes. Is included.

In the apparatus of the embodiment, the transducers 8a and 8b of the bevel probe 7a and 7b have an area of 8 × 9 mm ² and a vibration frequency of 5 MHz. The refraction angle is 45 degrees.

Further, the cycle T of the transmission pulse transmitted from each ultrasonic wave transmitting / receiving section 9a, 9b to each bevel probe 7a, 7b.
₀ is 1 ms, and each angle beam probe 7a, 7b is connected to the tube 5
The phases are shifted by 0.5 ms so that the ultrasonic pulses Pa and Pb entering the inside do not interfere with each other.

Further, the pipe 5 to be inspected has an outer diameter of 219.1.
It is an electric resistance welded pipe having a thickness of mm and a thickness t of 8.2 mm. Then, the pipe body 5 is transported in the axial direction at a speed of 1 m / s by the transport mechanism. As a result, the axial incident density of the ultrasonic pulses Pa and Pb incident on the tube body 5 from the respective bevel probes 7a and 7b on the tube body 5 is 1 mm / s.

Each of the ultrasonic wave transmitting / receiving sections 9a, 9b processes the received echo signals a, b to the next synchronous averaging circuit 10a, 10b.
Send to b. The synchronous averaging circuits 10a and 10b receive the received echo signals a. For example, b is added for Na cycles and averaged. Each of the averaged echo signals a ₁ and b ₁ has two gate circuits 11a, 11b, 11c and 11d, respectively.
Is input to.

As shown in FIG. 3, the echo signals a and b output from the ultrasonic wave transmitters / receivers 9a and 9b are transmitted pulses c.
, Which includes a surface echo (S echo) synchronized with the echo and an echo caused by the welding shape of the exposed portion 6b.
As shown in FIG. 2 (a), 1a is the front of the welding center of the welded portion 6, that is, the beveled angle of the welded portion 6b of the echo signal a ₁ from the left beveled probe 7a. Only the measurement period T _GA including only the echo caused by the inclined surface on the probe 7a side (front side) is passed. Specifically, the gate is opened only for the measurement period T _GA after a lapse of time T ₁ from the sending time of the transmission pulse c.

Further, the gate circuit 11b, as shown in FIG. 2 (a), of the echo signal a ₁ from the oblique-angle probe 7a on the left side, as shown in FIG. Only the measurement period T _GB including only the echo caused by the inclined surface on the side of the bevel probe 7b (right side) in the shape of the portion 6b is passed. Specifically, the gate is opened only for the measurement period T _GB after the time T _{2 has} elapsed from the time of sending the transmission pulse c.

The gate circuits 11c, 1 for controlling the passage time of the echo signal b ₁ from the right-angled oblique probe 7b.
1d is the same measurement period T as the circuit 11a, 11b.
_{It has GA} and T _GB .

In the apparatus of the embodiment, each gate circuit 11
Each of a to 11d is configured using, for example, an analog switch or the like. When the pipe body 5 and the oblique-angle probes 7a and 7b having the above-described shapes are adopted, the distance from the incident point of the ultrasonic pulses Pa and Pb to the pipe body 5 to the welding center of the inner peripheral surface is 12.1 mm, and assuming that the acoustic velocities of the ultrasonic pulses Pa and Pb propagating in the pipe body 5 are 3230 m / s, the time required for the ultrasonic pulses Pa and Pb to propagate from the incident point to the welding center of the inner peripheral surface. Is 7.492 μs. Therefore,
Gate circuits 11a, 11 for extracting the echoes on the front side
The measurement period of c is set to a time range of 3.5 to 7.4 μs, and the measurement period of each of the gate circuits 11b and 11d for extracting each echo on the back side is set to a time range of 7.5 to 11.5 μs.

Now, the relationship between the signal waveforms of the echo signals a and b and the welding shape of the exposed portion 6b on the inner peripheral surface will be described with reference to FIGS. 2 (a) (b) (c)
(D) shows a state in which the ultrasonic pulse Pa is propagated from the bevel probe 7a to different welding shapes of the exposed portion 6b on the inner peripheral surface thereof. And FIG. 3 (a) (b)
2C and 2D show respective waveforms of the echo signal a corresponding to the states of FIGS. 2A, 2B, 2C and 2D.

For example, in FIG. 2A, since the ultrasonic pulse Pa is reflected only by the inclined surface on the right side (back side) of the welded shape of the exposed portion 6b, an echo as shown in FIG. An echo appears in the signal a only in the gate circuit 11b.

Further, in FIG. 2B, since the ultrasonic pulse Pa is reflected by the inclined surface on the right side and the inclined surface on the left side of the welding shape of the exposed portion 6b, an echo is generated as shown in FIG. 3B. Both gate circuits 11a. An echo appears at 11b.

Further, in FIG. 2 (c), since the ultrasonic pulse Pa is reflected only by the inclined surface on the left side (front side) of the welded shape of the exposed portion 6b, it is echoed as shown in FIG. 3 (c). An echo appears only in the gate circuit 11a in the signal a.

Further, as shown in FIG. 2 (d), when the exposed portion 6b has a flat welded shape and coincides with the inner peripheral surface, there is an inclined surface facing the bevel probe 7a. Therefore, no echo appears at all in the echo signal a as shown in FIG.

With respect to the ultrasonic pulse Pb transmitted from the other angle probe 7b as well, the position of the echo appearing in the echo signal b changes similarly in accordance with the welding shape of the exposed portion 6b. Therefore, if the presence or absence of an echo and the echo position in each echo signal a, b are determined, the welding shape of the exposed portion 6b of the welded portion 6 on the inner peripheral surface is determined.

Each gate circuit 11a, 11b, 11c, 1
Each echo signal a ₂ . a ₃ , b ₂ ,
b ₃ are echo detection circuits 12a, 12b, 12 respectively.
c, 12d. Each echo detection circuit 12a-1
2d includes, for example, a peak hold circuit and a comparison circuit. Then, each echo detection circuit 12a to 12d
Detects whether or not the echo signals a _{2 to} b _{3 corresponding} to the respective input measurement periods T _GA and T _GB include echoes exceeding a predetermined threshold value, and includes echo presence / absence information. Measures the echo height E and sends it to the inner surface shape specifying unit 13.

The inner surface shape specifying unit 13 is composed of a kind of information processing device such as a computer, and is exposed based on a combination of echo presence / absence information sent from each echo detection circuit 12a to 12d and each echo height E. The type of the welding shape of the portion 6b is determined, and the radial dimension d of the welding shape is calculated.

More specifically, the combination table 14 shown in FIG. 6 is stored in the inner surface shape specifying section 13. In the combination table 14, each echo detection circuit 12a-1
The welding shape of the inner peripheral surface described above is stored for each of the combinations 1 to 9 of the echo detection presence / absence information in 2d.

For example, all the echo detectors 12a to 12d
For the first combination that does not detect echo at all,
A flat weld shape (equal to the inner peripheral surface) is stored.
Further, in the case of the second combination shown in FIG. 7 in which echoes are detected by the echo detectors 12b and 12d, the welding shape protruding in a rectangular shape with respect to the inner peripheral surface is stored.

Further, in the case of the third combination in which echoes are detected by the echo detectors 12a and 12c, as shown in the figure, the welding shape depressed in a rectangular shape with respect to the inner peripheral surface is stored.

Further, as shown in FIG. 8, the echo detector 1
In the case of the eighth combination in which the echo is detected only in 2d, the welding shape protruding in a wedge shape with respect to the inner peripheral surface is stored as illustrated.

Therefore, when the inner surface shape specifying unit 13 receives the echo detection presence / absence information from the echo detecting units 12a to 12d, the inner surface shape specifying unit 13 searches the combination table 14 for a corresponding combination, and finds the welding shape corresponding to this combination. The type is determined, and the pattern is displayed and output on, for example, a CRT display device.

Next, a procedure for the inner surface shape specifying portion 13 to calculate the radial dimension d of the welded shape of the exposed portion 6b which has been previously determined by using the echo height E received from each of the echo detecting portions 12a to 12d is illustrated. This will be described using 9. In the case of the welding shape shown in FIG. 9 (a), the echo signal a detected by the bevel probe 7a includes the echo 15 _L reflected by the left inclined surface of the welding shape and the echo signal a reflected by the right inclined surface. Echo 15 _R
And two echoes are included.

The echo heights (amplitudes) E _L and E _R of the respective echoes 15 _L and 15 _R are proportional to the area of each inclined surface as described above, so that the radial dimension d of each inclined surface is finally obtained. _L. It becomes a value corresponding to d _R. Therefore, each echo height E _L obtained by each echo detection circuit 12a, 12b,
By multiplying the multiplier determined experimentally E _R, the radial dimension d _L of the weld shape. Calculate d _R. Each of the calculated dimensions is C in the form in which the dimensions are added to the pattern of the welded shape.
Display output on RT display device.

FIG. 9C shows a bead height d which is known in advance.
It is an actual measurement value when the echo height E of the echo signal a is measured for a plurality of welding shapes having (radial dimension). As shown, the bead height d (radial dimension) was demonstrated to be approximately linearly proportional to the echo height E.

Next, the synchronous addition / averaging circuits 10a and 10
The detailed configuration and operation of b will be described with reference to FIGS. 4 and 5. FIG. 4 is a block diagram showing a schematic configuration of the synchronous averaging circuit 10a. The analog echo signal a input from the ultrasonic wave transmitting / receiving unit 9a in FIG. 1 is converted into a digital echo signal a _D at a predetermined sampling frequency f _R in the A / D converter 16 and then FIFO (first-in first-out) It is temporarily stored in the type register 17.

Each of the N _M (= 1024) 8-bit (n = 8) -structured data constituting the echo signal a _D sequentially read from the FIFO register 17 at the same sampling frequency f _R is the first signal. The data is written in the memory 18 and is also input to the adder 19 which performs digital addition processing.

As shown in the figure, the first signal memory 18 is formed with 256 areas 18a for storing the echo signal a _D. Therefore, each region 18a has N _M (=
1024) addresses, and each address can store 8-bit data. The write address WA ₁ of each data forming the echo signal a _D to the first signal memory 18 is the first write address counter 20.
Specified by a. The read address RA ₁ for reading the echo signal a _D stored in the first signal memory 28 is designated by the first read address counter 20b. Each counter 30a, 30b is driven by a clock signal ck having the same frequency as the sampling frequency f _R.

Further, the read address RA ₁ of the first read / read address counter 20b is delayed (small) by the average number Na times of the area 18a times the write address WA ₁ of the first write address counter 20a. The default setting is.

[0059] _{RA 1 = WA 1 -N M ·} Na = WA 1 -1024 · Na That is, each data of each echo signal a _D input the writing address WA ₁ that increases in synchronization with the clock signal ck
Are sequentially stored at each address specified by. At the same time, each data at the same waveform position of the echo signal a _D stored in the first signal memory 18 before Na times is read in synchronization with this writing operation.

When the write address WA ₁ and the read address RA ₁ reach the final address of the first signal memory 18, they return to the first address. Each data of the echo signal a _D before Na times read from the first signal memory 18 is input to the subtracter 21 which performs the following digital subtraction processing.

The second signal memory 22 has N (= 1024) addresses for storing one added echo signal a _D , that is, the added echo signal a _D1. Each 16-bit data can be stored in. Each data of the added echo signal output from the subtractor 21 is sequentially written in the second signal memory 22. Further, the added echo signal a _D1 read from the second signal memory 22 is input to the adder 19.

The write address WA ₂ of each data of the added echo signal from the subtracter 21 is designated by the second write address counter 23a. Further, the read address RA ₂ of each data of the added echo signal a _D1 to be sent to the adder 19 is the second address.
Designated by the read address counter 23b. Each counter 20a, 20b is driven by the clock signal ck. Further, in synchronization with the clock signal d, the four address counters 20a, 20b, 23a, 23b are arranged at the same position on the waveform signal of the echo signal a _D , that is, in each area 18a and the second signal memory 22. 1-102
It is initially set to specify the same address among the four.

The adder 19 composes the input echo signal a _D and each 16-bit data which composes the addition echo signal a _D1 read from the second signal memory 32.
Each bit-structured data is added and an addition echo signal composed of 16-bit structure data is sent to the subtractor 21.

The subtractor 21 subtracts each 8-bit data of the echo signal read from the first signal memory 18 from each 16-bit data of the added echo signal input from the adder 19. Then, the added echo signal including the subtracted 16-bit data is sent to the second signal memory 22 and the divider 24.

The divider 24 is composed of, for example, a bit shifter, divides the added echo signal by the average number of times Na, and writes the averaged echo signal a _D2 into the next FIFO register 25. The FIFO type register 25 sequentially reads out each of the 1024 pieces of written averaged echo signals a _{D2 at} the sampling frequency f _R , and D
It is sent to the / A converter 26. The D / A converter 26 is a FIF
The digital echo signal a _D2 read from the O-type register 25 is converted into an averaged analog echo signal a ₁ , and each gate circuit 11a. 11b.

Synchronous averaging circuit 1 configured in this way
The operation of 0a will be described. Initially, in the initial state where no echo signal a _D is input, the first signal memory 1
No data 18 of the echo signal a _D is stored in each area 18a of 8 and the second signal memory 22.

Then, from the FIFO type register 17 to the first
When the echo signal a _{D for the} second time is input, it is stored in the first area 18 a of the first signal memory 18. At the same time, it is stored in the second signal memory 22. That is, initially, since nothing is stored in each address of the area 18a designated by the read address RA ₁ of the second signal memory 22 and the first signal memory 18, the input echo signal a _D is added to the adder 19 And the second signal memory 22 through the subtractor 21.
Stored in.

When the second echo signal a _D is input,
The adder 19 adds the echo signal of this time and the echo signal of the previous time (first time) to create an added echo signal. However, in the case of the average number of times Na> 2, nothing is stored in each address of the area 18a designated by the read address RA _{1 of} the first signal memory 18, so that the addition echo signal passes through the subtractor 21 without passing. Then, it is stored in the second signal memory 22.

As described above, the echo signals are sequentially added to the second signal memory 22 until the average number Na of echo signals a _D are input. When the echo signal a _D having the average number of times Na or more is input, the echo signal input Na number of times before the newly input echo signal a _D is read and sent to the subtractor 21.

That is, when the new echo signal a _D is input to the added echo signal a _D1 stored in the second signal memory 22, the new echo signal a _D is added,
The echo signal a _{D, which} is the Na-th previous signal, is subtracted. Therefore,
The second signal memory 22 always stores the added echo signal a _D1 obtained by adding the latest Na echo signals.

Therefore, the divider 24 outputs the echo signal a _D2 obtained by averaging the latest Na echo signals. Then, the averaged analog echo signal a ₁ is output from the synchronous addition and averaging circuit 10a.

The synchronous addition / averaging circuit 10b for averaging the other echo signal b has the same structure as the above-mentioned synchronous addition / averaging circuit 10a for the echo signal a. By adopting the synchronous averaging circuits 10a and 10b having such a configuration, the S / N ratios of the echo signals a and b output from the ultrasonic wave transmitting / receiving units 9a and 9b are increased. That is, for example, when performing an online inspection while moving the tube body 5 in the axial direction, it is possible to remove electrical noise caused by the ultrasonic wave transmitting / receiving section and noise caused by the crystal grain boundaries and the surface structure of the material of the tube body 5.

Further, as described above, in the electric resistance welded pipe manufactured by rolling the steel plate while the pipe body 5 is running and continuously welding the abutting portions, the welded portion 6 is formed along the axial direction of the pipe body 5. 2 (a) (b)
The same type of welding shape on the inner peripheral surface as shown in (c) continues for a certain length or more in the axial direction of the tubular body 5. However, the general defects that are not related to the welding are shorter than the weld shape described above.

Therefore, by averaging the echo signals a and b, it is possible to reduce the proportion of the echoes caused by the defects and detect only the echoes caused by the weld shape with a high S / N.

FIG. 5 shows the waveform of each echo signal a before input to the synchronous addition / averaging circuit 10a and the echo signal a averaged by the synchronous addition / averaging circuit 10a when the average number Na is set to 4. _It can be understood that the S / N ratio of the echo in the averaged echo signal a ₁ is significantly improved as shown in the figure, which is an actual measurement diagram showing a comparison with the waveform of ₁ .

The average number of times Na is the first write address counter 20a and the first read address counter 20.
This can be easily changed by appropriately setting the relationship between the count values WA ₁ and RA ₁ of b.

In the apparatus of the embodiment, the echo signal a in each of the synchronous averaging circuits 10a and 10b,
The average number Na of b is set to Na = 128 times in consideration of the axial length of a defect not caused by welding.

This means that the traveling speed of the tubular body 5 is 1 m / s.
Since the c transmission period T ₀ of the ultrasonic pulses Pa and Pb is 1 ms, it corresponds to an average of 128 mm in the axial direction of the tubular body 5. Even with this average number of times, the welding shape of the welded portion 6 on the inner peripheral surface hardly changes, and the echo height E included in the obtained echo signals a and b does not decrease.

On the other hand, the axial length of the defect in the tubular body 5 is about 20 mm at the longest. Therefore,
Averaging over a length of 128 mm significantly reduces the average echo height due to this defect. That is, the echo caused by the defect can be removed from the echo signals a and b, and only the echo caused by the welding shape can be extracted with a high S / N. Especially for electrical noise, S / N is 12
Since it can be improved by 8 ^1/2 (about 21 dB), it is possible to detect a slight step in the welded portion.

FIG. 10 is a block diagram showing the schematic arrangement of an in-pipe shape inspection apparatus according to another embodiment of the present invention. Figure 1
The same parts as those in the embodiment shown in FIG. Therefore, detailed description of the overlapping portions is omitted.

In this embodiment, the gate circuit 1
The echo signal a ₂ output from 1a is input to the echo height detection circuit 41a and the beam path detection circuit 42a.
Similarly, the echo signal a ₃ output from the gate path 11b
Is an echo height detection circuit 41b and a beam path detection circuit 4
Input to 2b.

Further, the echo signal b ₂ output from the gate circuit 11c is input to the echo height detecting circuit 41c and the beam path detecting circuit 42c. The echo signal b ₃ output from the gate circuit 11d is the echo height detection circuit 41.
d and the beam path detection circuit 42d.

[0083] determines whether the echo height detection circuit 41a~41d are included the input echo signals _{a 2, a 3, b 2} , b 3 to the above echo batchwise, if it contains the The height E of the echo is measured, and the next inner surface shape specifying portion 43 is measured.
Send to. In addition, the beam path length detection circuits 42a to 42
As shown in FIG. 11, d is the input echo signal a ₂ ,
When echoes are included in a ₃ , b ₂ and b ₃ , the times Ta and Tb from the time of incidence of the ultrasonic pulses Pa and Pb of the echoes a and b to the tube body 5 to the time of rise of the echoes Ta and Tb.
Is measured to measure the beam path length L of the ultrasonic pulses Pa and Pb.
Calculate ₁ and L ₂ . The calculated beam path lengths L ₁ and L ₂ are sent to the next inner surface shape specifying unit 43.

Therefore, each echo height detection circuit 4 described above
1a-41d and each beam path detection circuit 42a-42d
Constitutes an echo detection circuit. Next, the inner surface shape specifying unit 4
The operation of No. 3 will be described with reference to FIGS. 11 and 12.

First, the inner surface shape specifying section 43 specifies the type of welding shape from the above-mentioned combination table 14 based on the combination of the echo detection presence / absence information received from the echo height detection circuits 41a to 41d. Next, the radial dimension d of the welding shape is calculated from the echo heights E received from the echo height detection circuits 41a to 41d.

Further, the inner surface shape specifying unit 43 receives the beam path lengths L received from the beam path length detection circuits 42a to 42d.
The circumferential dimension Ls of the welded shape is calculated from. That is,
As shown in FIG. 12, it can be considered that the inclined surface where the echo is generated is present at the intersection of the arc having the radius of the beam path L and the inner peripheral surface of the tubular body 5 centering on the incident point of the ultrasonic pulses Pa and Pb. It is possible. Since the distance between each bevel probe 7a, 7b and the center line of the welded portion 6 and the thickness t of the tubular body 5 are known, the position of the inclined surface, that is, the position in the circumferential direction is specified. When the positions of the inclined surfaces existing at both ends of the welding waveform are specified, the circumferential dimension Ls of the welding waveform is calculated.

For example, in the case of the rectangular welding shape corresponding to the second combination type shown in FIG. 12, the echo signals a and b are only echo signals a ₃ and b _{3 as} shown in FIG. Each has an echo. Then, the echo heights E _R and E _L become the radial dimensions d _R and d _{L at} both end positions of the welding shape. Further, the circumferential dimension Ls of the welding waveform is calculated from the beam path lengths L ₁ and L _{2 of} each echo.

Then, the determined welding waveform pattern, the calculated radial dimensions d _R and d _L, and the circumferential dimension Ls are graphically displayed on a CRT display device (not shown).

With the pipe shape inspection device thus constructed, not only the type (pattern) of the welding shape on the inner peripheral surface of the pipe body 5 but also the respective dimensions of this welding shape can be grasped. Therefore, by returning this quantitative data to the bead cutting machine, the bead cutting machine can be controlled more precisely, and even the slight unevenness due to welding existing on the inner peripheral surface of the pipe body 5 is not overlooked and the flat bead cutting is performed. it can. Therefore,
The yield and quality of the manufactured tubular body 5 can be improved.

[0090]

As described above, according to the in-pipe shape inspection apparatus of the present invention, the pair of beveled probes are arranged at opposite positions with the welding portion sandwiched therebetween, and the welding portion exposed on the inner peripheral surface is provided. In contrast, an ultrasonic pulse is transmitted, and an echo caused by the exposed unevenness is received. Then, the pattern (type), dimensions, etc. of the welding shape are inspected by using the position of the echo, the echo height, the beam path length, etc. included in the echo signal.

Therefore, it can be applied to a pipe having a small diameter, can be installed in the vicinity of a bead cutting machine, and can reliably and accurately form the shape of the welded portion on the inner peripheral surface with a low manufacturing cost. Can be detected.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a pipe shape inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a welding shape generated on an inner peripheral surface of a tubular body due to a welding operation and a state in which an ultrasonic pulse is reflected by each welding shape.

FIG. 3 is a diagram showing a relationship between an echo signal and a measurement period of a gate circuit in the apparatus of the embodiment.

FIG. 4 is a block diagram showing a schematic configuration of a synchronous averaging circuit incorporated in the apparatus of the embodiment.

FIG. 5 is an echo waveform diagram showing an averaging operation of the synchronous addition and averaging circuit.

FIG. 6 is a view showing a combination table stored in the apparatus of the embodiment.

FIG. 7 is a diagram showing a relationship between a welding shape and an echo signal waveform.

FIG. 8 is a diagram showing a relationship between a welding shape and an echo signal waveform in the same manner.

FIG. 9 is a diagram showing a measurement principle and a measured value of a radial dimension of a welded shape in the apparatus of the embodiment.

FIG. 10 is a block diagram showing a schematic configuration of an in-pipe shape inspection device according to another embodiment of the present invention.

FIG. 11 is an echo signal waveform diagram measured by the apparatus of the embodiment.

FIG. 12 is a view showing a principle of measuring a circumferential dimension of a welded shape in the apparatus of the embodiment.

FIG. 13 is a schematic diagram showing a conventional pipe shape measuring method.

FIG. 14 is a schematic view showing a conventional pipe shape measuring method.

[Explanation of symbols]

5 ... tubular body. 6 ... Welded part, 7a, 7b ... Angle probe, 9
a, 9b ... Ultrasonic wave transmitting / receiving section, 10a, 10b ... Synchronous averaging circuit, 11a-11d ... Gate circuit, 12a-12
d ... Echo detection circuit, 13, 43 ... Inner surface shape specifying unit, 1
4 ... Combination table, 16 ... A / D converter, 17, 25
... FIFO type register, 18 ... First signal memory, 19
... adder, 21 ... subtractor, 22 ... second signal memory, 2
6 ... D / A converter, 41a-41d ... Echo height detection circuit, 42a-42d ... Echo height detection circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Nakazawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (5)

[Claims] 1. A pair of slanting members which are disposed on the outer peripheral surface of a tubular body at opposing positions with a welded portion interposed therebetween and which transmit an ultrasonic pulse toward a welded portion exposed on the inner peripheral surface and receive a reflected wave. An angle probe, a pair of ultrasonic wave transmitting / receiving units that apply a transmission pulse to each of the oblique angle probes at a constant cycle and receive an echo signal, and the received echo signal over a plurality of cycles. A pair of synchronous addition averaging means for averaging, a plurality of gate means for designating mutually different measurement periods in the averaged echo signal, and a welded portion of the inner peripheral surface included in the designated measurement period An in-pipe shape inspection device comprising: a plurality of echo detection means for detecting the resulting echo; and an inner surface shape specifying section for specifying the welded shape of the inner peripheral surface based on the detected echoes. 2. The inner surface shape specifying section has a welding shape type judging means for judging a kind of the welding shape based on a combination of echo detection presence / absence information in each echo detecting means. The pipe shape inspection device described. 3. The inner surface shape specifying section has a radial dimension calculating means for calculating a radial dimension of the welded shape from an echo height of an echo detected by each echo detecting means. Item 2. The pipe shape inspection device according to item 2. 4. Each of the echo detecting means has a beam path detecting means for detecting a beam path of the ultrasonic pulse up to a detected echo, and the inner surface shape specifying section is configured to detect the beam path from the detected beam paths. The pipe shape inspection device according to claim 3, further comprising a circumferential dimension calculation unit that calculates a circumferential dimension of the welded shape. 5. The synchronous averaging means converts A / D conversion means for converting the echo signals received by the ultrasonic wave transmitting / receiving section into digital echo signals, and outputs the A / D conversion means in sequence. A first signal memory that always stores a predetermined number of latest echo signals, a second signal memory that stores one added echo signal, and the latest echo signal in the first signal memory. A signal reading means for reading the echo signals written in the number of the destinations;
An adding unit that adds the echo signals sequentially output from the D conversion unit and the added echo signal read from the second signal memory, and the signal reading unit reads the added echo signal output from the adding unit. A subtraction unit for subtracting the generated one echo signal; an addition echo signal updating unit for writing the addition echo signal output from the subtraction unit into the second signal memory as a new addition echo signal; and the subtraction unit. And a D / A conversion means for converting the averaged echo signal into an analog echo signal. The in-pipe shape inspection device according to claim 1, which is characterized in that.