JP4425690B2 - Method and apparatus for measuring outer peripheral length of spiral steel pipe, method for manufacturing spiral steel pipe and equipment therefor - Google Patents

Description

The present invention relates to a spiral steel pipe outer peripheral length measuring method and apparatus, a spiral steel pipe manufacturing method using the spiral steel pipe outer peripheral length measuring method, and a spiral steel pipe manufacturing facility using the spiral steel pipe outer peripheral length measuring apparatus.

Conventionally, as a device for measuring the outer peripheral length of a steel pipe, as shown in FIG. 13, a reference point p is set at a position of a distance L longer than the outer peripheral length of the steel pipe 101 to be measured from the fixed end a of the measuring belt 100, The fixed end a of the measurement belt 100 is tightly fixed on the outer surface of the steel pipe 101 by the fixed terminal 102, the measurement belt 100 is wound around the steel pipe 101, and the reference point p side of the measurement belt 100 is tangential from the fixed position of the fixed end a. An outer peripheral length measuring device 104 is proposed in which the distance k to the reference point p of the measuring belt 100 taken out is measured by the length measuring device 103 and Lk is calculated to obtain the outer peripheral length of the steel pipe 101 ( For example, see Patent Document 1).
Further, as shown in FIG. 14, a steel pipe 105 whose outer peripheral length is to be measured is placed on a gantry 106, light is emitted from a projector 107 from a predetermined angle direction with respect to the gantry surface, and the projector is sandwiched between the steel pipes 105. For example, two photodetectors 109 and 110 are arranged on a screw 108 provided on the opposite side of 107, the screw pitch for moving one photodetector 109 is increased, and the screw pitch for moving the other photodetector 110 is increased. A steel pipe outer diameter measuring device capable of simultaneously adjusting the positions of the photodetectors 109 and 110 according to a change in the outer diameter of the steel pipe 105 with a single screw driving device 111 while reducing the screw direction and reversing the screw direction. 112 has been proposed (see, for example, Patent Document 2).

On the other hand, as shown in FIG. 15, the transmitter A and the receiver B of the surface wave are arranged on the steel pipe surfaces on both sides of the welded seam portion 115 of the spiral steel pipe 114 manufactured by forming the strip 113, and the transmitter A The surface wave propagation path L _AB from the receiver A to the receiver B is set so as not to cross the weld seam 115, and the surface wave is transmitted based on the measured surface wave propagation time and surface wave propagation velocity from the transmitter A to the receiver B. There has been proposed a method for calculating the outer peripheral length of the spiral steel pipe 114 by obtaining the length of the propagation path L _AB (see, for example, Patent Document 3).
Further, as shown in FIG. 16, the transmitting and receiving ultrasonic probes 117 and 118 are mounted on the same peripheral surface of the tube material 116 via the gimbal mechanism 119, and the transmitting ultrasonic probe 117 is attached. An ultrasonic distance measuring device 120 that measures the tube circumference length of the tube material 116 from the time until the transmitted surface wave propagates on the surface of the tube material 116 and reaches the reception ultrasonic probe 118 and the surface wave propagation velocity. Has been proposed (see, for example, Patent Document 4).

JP 58-83207 A JP-A-58-108406 Japanese Patent Laid-Open No. 7-83644 JP 2000-329543 A

In general, as shown in FIG. 15, when manufacturing the spiral steel pipe 114 by forming the strip 113 into a spiral shape, it is necessary to sequentially correct the forming conditions of the strip 113 in accordance with the fluctuation of the outer peripheral length of the spiral steel pipe 114. is there. For this purpose, it is preferable to measure the outer peripheral length of the spiral steel pipe 114 immediately after the strip 113 is formed into a spiral shape and welded to the outer surface. Therefore, it was examined that the inventions described in Patent Documents 1 to 4 are applied to the measurement of the outer peripheral length of a spiral steel pipe immediately after outer surface welding.
In the case of using the outer peripheral length measuring device 104 described in Patent Document 1, there is a problem that it is difficult to stably measure the outer peripheral length and maintain the measurement accuracy from the viewpoint of durability of the measuring belt 100. In addition, it is necessary to secure a wide space for installing the outer peripheral length measuring device 104. However, when the outer peripheral length of the spiral steel pipe immediately after the outer surface welding is to be measured, the outer surface welding machine becomes an obstacle and the outer peripheral length becomes longer. There also arises a problem that the measuring device 104 cannot be installed.
In the outer diameter measuring device 112 of the steel pipe described in Patent Document 2, since the outer peripheral length is calculated from the outer diameter of the spiral steel pipe, there is a problem that the measurement accuracy is essentially inferior. Furthermore, since the light emitted from the projector 107 is detected by the photodetectors 109 and 110 through an inferior atmosphere caused by fume generated during welding, the outer diameter of the spiral steel pipe is measured while maintaining stable measurement accuracy. The problem of not being able to do arise.

When applying the method for measuring the outer peripheral length of a spiral steel pipe described in Patent Document 3, if the surface wave propagation path L _AB is perpendicular or close to the pipe axis of the spiral steel pipe, it is transmitted to avoid the influence of welding heat. It is necessary to dispose the child A and the receiver B away from the weld seam 115. At this time, depending on the inclination of the weld seam portion 115 with respect to the steel pipe shaft, the transmitter A and the receiver B are installed at a large distance, and the distance between the transmitter A and the receiver B must be measured separately when determining the outer peripheral length. In other words, there arises a problem that the measurement accuracy of the outer peripheral length is lowered. On the other hand, when the surface wave propagation path L _AB is inclined with respect to the steel pipe axis of the spiral steel pipe, the geometrical calculation is performed from the measured surface wave propagation path L _AB to calculate the outer peripheral length, so that there is a problem in accuracy. . Furthermore, the transmitter A and the receiver B must be arranged at different positions in the direction of the steel pipe axis. Since the distance between the transmitter A and the receiver B is wide, the outer peripheral length of the spiral steel pipe is measured immediately after the outer surface welding. I can't do that.
When using the ultrasonic distance measuring device 120 described in Patent Document 4, if the transmitter and the receiver are arranged so that the propagation path of the surface wave does not cross the weld, the same problem as in Patent Document 3 occurs. Further, if the transmitter and receiver are arranged close to the outer surface welder in an attempt to measure the outer peripheral length of the spiral steel pipe immediately after the outer surface welding, the surface wave propagation path crosses the weld. When surface waves cross the weld, surface waves propagate along the rise of the weld bead, creating a difference between the surface wave propagation path and the outer circumference of the spiral steel pipe, and how to handle this difference. Thus, there arises a problem of determining the outer peripheral length of the spiral steel pipe.

The present invention has been made in view of such circumstances, and a method and apparatus for measuring the outer peripheral length of a spiral steel pipe capable of accurately measuring the outer peripheral length of a spiral steel pipe immediately after outer surface welding, and the outer peripheral length of the spiral steel pipe. It is an object of the present invention to provide a method and apparatus for manufacturing a spiral steel pipe capable of sequentially correcting the forming conditions of a strip according to fluctuations in the above.

The outer peripheral length measurement method of the spiral steel pipe according to claim 1, which meets the above-mentioned purpose, includes a transmitter and receiver for surface waves on the outer surface of the spiral steel pipe having an outer diameter of less than 1100 mm,
Setting the propagation path of the surface wave in a cross section substantially perpendicular to the steel pipe axis of the spiral steel pipe, and across the weld bead portion of the spiral steel pipe,
Obtain the propagation time of the surface wave from the transmitter to the receiver and calculate the path length of the propagation path using the propagation speed of the surface wave,
A method for measuring the outer peripheral length of a spiral steel pipe that calculates the outer peripheral length of the spiral steel pipe from the distance between the transmitter and the receiver and the path length,
The frequency range of the surface waves detected by the receiving element and the 0.1MHz or 10MHz or less, along the outer surface of the peaks and the weld bead portion of the waveform D corresponding to the path for straight interior of the weld bead portion The peak of the waveform D that appears first among the peaks of the waveform R corresponding to the propagation path is selected, and the propagation time of the surface wave is obtained based on the peak of the waveform D.

The propagation path of the surface wave is set through the weld bead part of the spiral steel pipe, that is, across the weld bead part, so that the transmitter and receiver are located sufficiently away from the weld bead part so that the thermal effect of the weld bead part can be ignored. Can be arranged, and the distance between the transmitter and the receiver can also be arranged close to each other. For this reason, the outer circumference length of the spiral steel pipe can be measured by arranging the transmitter and the receiver in a small area on the outer surface of the spiral steel pipe.
Further, since the propagation path of the surface wave is set in a circular cross section substantially perpendicular to the steel pipe axis of the spiral steel pipe, the difference between the propagation path length and the outer peripheral length of the spiral steel pipe can be reduced. .
Here, “substantially perpendicular to the steel pipe axis of the spiral steel pipe” means that the angle between the circular cross section formed by the line connecting the transmitter and the receiver on the outer surface of the spiral steel pipe and the steel pipe axis is 85 to 95 °. Indicates a range.

If the outer diameter of the scan Pairaru steel pipe is small and less than 1100 mm, the path length of the propagation path of the surface wave becomes shorter, it is possible to suppress the attenuation of surface waves when propagating through the surface of the spiral pipe, 0.1 MHz or more below 10MHz Preferably, a surface wave having a frequency range of 0.5 MHz to less than 10 MHz, more preferably 1 MHz to 5 MHz can be used. As a result, the propagation time of the surface wave can be measured with high accuracy from the peak position of the waveform.

The outer peripheral length measuring device for a spiral steel pipe according to claim 2, which meets the object, is arranged with a predetermined gap on the outer surface of the spiral steel pipe on a cross section substantially perpendicular to the steel pipe axis of the spiral steel pipe, A transmitter and receiver for transmitting and receiving surface waves across the weld bead of the spiral steel pipe;
First calculating means for obtaining a propagation time of the surface wave from the transmitter to the receiver and calculating a path length of the propagation path using a propagation speed of the surface wave;
An apparatus for measuring the outer peripheral length of a spiral steel pipe having a second computing means for calculating the outer peripheral length of the spiral steel pipe from the distance between the transmitter and the receiver and the path length,
When the outer diameter of the spiral steel pipe is less than 1100 mm, the frequency range of the surface wave transmitter and receiver is 0.1 MHz or more and 10 MHz or less, and 0.15 MHz or more when the outer diameter of the spiral steel pipe is 1100 mm or more. detected by follows to the receiving element, the peak of the waveform R corresponding to the path that propagates along the outer surface of the peaks and the weld bead portion of the waveform D corresponding to the path for straight interior of the weld bead portion home,
In the first calculation means, when the outer diameter of the spiral steel pipe is less than 1100 mm , the peak of the waveform D that appears first is selected, and when the outer diameter of the spiral steel pipe is 1100 mm or more , it appears with a delay. A path selection unit for selecting the peak of the waveform R is provided.

By this, it is possible to set an optimum propagation paths for spiral pipe of any outer diameter.

The spiral steel pipe manufacturing method according to claim 3 , wherein the spiral steel pipe is formed in a spiral shape with a molding machine, and the outer surface side of the strip is welded with an outer surface welding machine. In the manufacturing method of
The outer peripheral length of the spiral steel pipe was measured at a position within 10m from the outer surface welding machine using the circumferential length measurement method of the spiral steel pipe according to claim 1 Symbol placement, correct the forming conditions of the molding machine based on the measurement result To do.
Thereby, when the outer peripheral length of the spiral steel pipe fluctuates, the molding conditions of the molding machine can be corrected immediately.
Here, the measurement position of the outer peripheral length of the spiral steel pipe is within 10 m from the outer surface welding machine, but is preferably set within 5 m, more preferably within 2 m. Moreover, the molding conditions of the molding machine refer to, for example, the angle in the conveying direction of the strip transported to the molding machine, the amount of reduction of the entry side inner and outer surface forming rolls, and the amount of outer surface pressing roll reduction.

The manufacturing equipment for a spiral steel pipe according to claim 4, which meets the above-mentioned purpose, includes a molding machine for forming a strip into a spiral shape,
An outer surface welding machine for forming a spiral steel pipe by welding the outer surface side of the strip formed into a spiral shape;
It has a peripheral length measuring device of spiral steel pipe according to claim 2 ,
The outer peripheral length measuring device of the spiral steel pipe is installed within 10 m from the outer surface welding machine, and corrects the molding condition of the molding machine based on the measurement result of the outer peripheral length of the spiral steel pipe.

In the outer peripheral length measuring method of spiral pipe as claimed in claim 1 Symbol placement, so setting the surface wave propagation path across the weld bead portion of the spiral pipe, the outgoing terminal and the receiving terminal on the outer surface of the spiral pipe small The outer circumferential length of the spiral steel pipe can be measured by arranging in the region, and for example, the transmitter and the receiver can be arranged close to the outer surface welder side. As a result, it becomes possible to detect the fluctuation of the outer peripheral length of the spiral steel pipe at an early stage.
In addition, since the transmitter and receiver are arranged on the outer periphery of the cross section substantially perpendicular to the steel pipe axis of the spiral steel pipe to set the propagation path of the surface wave, the distance between the transmitter and the receiver and the propagation path The difference between the measurement length obtained as the sum of the path length and the outer peripheral length of the spiral steel pipe can be reduced, and errors in performing geometric calculations on the measurement length are reduced, resulting in a highly accurate spiral steel pipe. It is possible to measure the outer peripheral length of the.

Moreover , in the outer peripheral length measuring method of the spiral steel pipe according to claim 1, when the outer diameter of the spiral steel pipe is less than 1100 mm and the frequency range of the surface wave is 0.1 MHz or more and 10 MHz or less, the propagation path is set. Since a path that goes straight through the inside of the weld bead is adopted, it is possible to measure the propagation time of the surface wave from the peak position of the waveform with high accuracy, and to measure the outer circumference of the spiral steel pipe with high accuracy. .

3. The outer peripheral length measuring apparatus for a spiral steel pipe according to claim 2 , wherein the surface wave transmitter and receiver are arranged on the outer surface of the spiral steel pipe so that a propagation path of the surface wave is formed across the weld bead portion of the spiral steel pipe. Therefore, the distance between the transmitter and the receiver can be reduced. For example, the transmitter and the receiver can be arranged close to the outer surface welder side. As a result, it becomes possible to detect the fluctuation of the outer peripheral length of the spiral steel pipe at an early stage.
In addition, since the propagation path of the surface wave is set on a cross section substantially perpendicular to the pipe axis of the spiral steel pipe, the error in performing geometric calculation on the path length of the propagation path is reduced. It becomes possible to measure the outer peripheral length of a spiral steel pipe with high accuracy.

In particular, the frequency range of the transmitting terminal and receiving terminal of the front surface waves, the outer diameter of the spiral pipe is 0.1MHz or 10MHz or less in the case of less than 1100 mm, the outer diameter of the spiral pipe is more than 0.1MHz in the case of more than 1100 mm 2MHz The first calculation means adopts a path that goes straight through the inside of the weld bead as a propagation path when the outer diameter of the spiral steel pipe is less than 1100 mm, and propagates when the outer diameter of the spiral steel pipe is 1100 mm or more. Since a path selection unit that employs a path that propagates along the outer surface of the weld bead as a path is provided, an optimal propagation path can be set for a spiral steel pipe of any outer diameter, It becomes possible to measure the propagation time of the surface wave reliably and accurately in the outer diameter spiral steel pipe.

In the method for producing a spiral pipe of claim 3, wherein the outer peripheral length of the spiral steel pipe was measured at a position within 10m from the outer surface welding machine using the circumferential length measurement method of the spiral steel pipe according to claim 1 Symbol placement, results of the measurement Therefore, the molding condition of the molding machine can be corrected by detecting the fluctuation of the outer peripheral length of the formed spiral steel pipe at an early stage. As a result, it becomes possible to prevent the manufacture of a spiral steel pipe whose outer peripheral length is out of specification.

In the spiral steel pipe manufacturing facility according to the fourth aspect , since the outer peripheral length measuring device is installed within 10 m from the outer surface welding machine, it becomes possible to quickly detect the fluctuation of the outer peripheral length of the spiral steel pipe. And when the outer periphery length of a spiral steel pipe fluctuates, the molding conditions of a molding machine can be corrected immediately, and it becomes possible to prevent the manufacture of a spiral steel pipe whose outer periphery length is out of specification.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is an explanatory view of a manufacturing facility for a spiral steel pipe according to an embodiment of the present invention, FIG. 2 is an explanatory view of an outer peripheral length measuring device for a spiral steel pipe used in the manufacturing facility for the spiral steel pipe, and FIG. Explanatory drawing which shows the propagation path of the surface wave which propagates the weld bead part in the outer peripheral length measuring method of the spiral steel pipe applied to the manufacturing method of the spiral steel pipe concerning one embodiment of the present invention, FIG. 4 is transmitted in a large diameter spiral steel pipe FIG. 5 is an explanatory diagram showing a received signal waveform obtained when a receiver receives a surface wave having a frequency of 0.1 MHz transmitted from a child. FIG. 5 shows a receiver having a surface wave having a frequency of 5 MHz transmitted from the transmitter in a large-diameter spiral steel pipe. FIG. 6 is an explanatory diagram showing a received signal waveform obtained when receiving the signal at FIG. 6. FIG. 6 shows the reception of the surface wave having a frequency of 0.1 MHz transmitted from the transmitter in the small-diameter spiral steel pipe. Explanatory view showing a reception signal waveform obtained, FIG. 7 is an explanatory diagram showing a received signal waveform obtained when received by the receiving transducer surface wave of frequency 5MHz transmitted from the originating terminal in diameter spiral pipe.

As shown in FIG. 1, a spiral steel pipe manufacturing facility 10 according to an embodiment of the present invention includes a forming machine 12 for forming a strip 11 into a spiral shape, and an outer surface of the strip 11 formed into a spiral shape. It has an outer surface welder 13 that welds the sides to form a spiral steel pipe 18, and an outer peripheral length measuring device (hereinafter simply referred to as an outer peripheral length measuring device) 14 of the spiral steel pipe. These will be described in detail below.
The forming machine 12 is transported from the pre-processing unit 15 and the pre-processing unit 15 that gradually pulls out the strip 11 wound in a coil shape and sends out the transport direction according to the outer diameter of the spiral steel pipe 18 to be manufactured. The strip 11 is formed with a plurality of inlet-side inner / outer surface forming rolls 16 so as to be formed into a spiral shape while being reduced according to the outer diameter of the spiral steel pipe 18. The outer surface welder 13 welds and integrates the outer peripheral side of the contact portion formed continuously between adjacent spiral strips 11 to form a spiral steel pipe 18. For example, a submerged arc welder is used. can do.

As shown in FIG. 2, the outer peripheral length measuring device 14 is substantially perpendicular to the steel pipe axis of the spiral steel pipe 18 that is assumed to be located within 10 m, preferably within 5 m, more preferably within 2 m from the outer surface welding machine 13 ( A predetermined gap (a distance M between the center of the transmitter 19 and the receiver 20 is 100 to 400 mm, for example) is arranged on the outer periphery of the cross section (85 to 95 °) (on the outer surface of the spiral steel pipe 18). It has a transmitter 19 and a receiver 20 for transmitting and receiving surface waves.
As described above, when the outer peripheral length of the spiral steel pipe 18 is measured at a position close to the outer surface welding machine 13, when the outer peripheral length of the manufactured spiral steel pipe 18 fluctuates, the molding conditions of the molding machine 12 are corrected immediately. can do.
Here, as the transmitter 19 and the receiver 20, those having a function of transmitting a surface wave in a specific direction and receiving a surface wave from the specific direction are used. As a result, when the transmitter 19 and the receiver 20 are arranged on the outer surface of the spiral steel pipe 18, the transmitter 19 travels on the outer circumference of the cross section substantially perpendicular to the steel pipe axis of the spiral steel pipe 18. A surface wave can be transmitted, and a surface wave traveling in a detour can be received by the receiver 20.

When the outer diameter of the spiral steel pipe 18 is less than 1100 mm, the surface wave transmitter 19 and the receiver 20 are 0.1 MHz to 10 MHz, preferably 0.5 MHz to less than 10 MHz, more preferably 1 MHz to 5 MHz. An ultrasonic transmitter having a frequency range of 0.1 MHz to 2 MHz, preferably 0.5 MHz to 1 MHz when the outer diameter of the spiral steel pipe 18 is 1100 mm or more using an ultrasonic transmitter or ultrasonic receiver in the range. Use an ultrasonic receiver.
As a result, when the outer diameter of the spiral steel pipe 18 is as small as less than 1100 mm, the propagation time of the surface wave can be measured with high accuracy. Further, when the outer diameter of the spiral steel pipe 18 is as large as 1100 mm or more, even if the path length of the surface wave propagation path is increased, the surface wave propagation time is reduced from the peak position of the waveform by suppressing the attenuation of the surface wave. It can be measured with high accuracy.
When the outer diameter of the spiral steel pipe is as large as 1100 mm or more, the path length of the propagation path of the surface wave becomes long, and the attenuation of the surface wave when propagating on the surface of the spiral steel pipe becomes remarkable. For this reason, a surface wave having a frequency range of 0.1 MHz to 2 MHz, preferably 0.5 MHz to 1 MHz is used. Accordingly, the surface wave can be reliably received while suppressing the attenuation of the surface wave, and the propagation time of the surface wave can be accurately measured from the peak position of the waveform.
In addition, when the frequency of the surface wave is reduced, the reception signal wave of the surface wave is spread and an error occurs in the measurement of the propagation time. However, when the outer diameter of the spiral steel pipe is 1100 mm or more, the outer peripheral length of the spiral steel pipe is increased. The influence of errors in the measurement of the outer peripheral length of the spiral steel pipe can be reduced.

Further, the outer peripheral length measuring device 14 obtains the propagation time of the surface wave from the transmitter 19 to the receiver 20 and uses the propagation speed of the surface wave to determine the path length L of the propagation path (from the center of the transmitter 19 to the spiral steel pipe 18. A distance between the transmitter 19 and the receiver 20; a first calculator 21 that calculates the distance from the outer periphery of the cross section substantially perpendicular to the steel pipe axis to the far side and the center of the receiver 20; Second calculation means 22 for calculating the outer peripheral length (L + M) of the spiral steel pipe 18 from the center distance M and the path length L.
Here, since the transmitter 19 and the receiver 20 are arranged on the outer periphery of the cross section substantially perpendicular to the steel pipe axis of the spiral steel pipe 18, the surface transmitted from the transmitter 19 as shown in FIG. The wave travels across the weld bead 23 of the spiral steel pipe 18 and reaches the receiver 20. When the surface wave crosses the weld bead part 23, a part of the surface wave travels along the path DP that travels straight inside the weld bead part 23, and the remaining surface wave propagates along the outer surface of the weld bead part 23. Proceed with RP. Since the path DP is shorter than the path RP, but both are smaller than the path length L, the receiver 20 detects the surface wave that has passed through the path RP with a slight delay after the surface wave that has passed through the path DP is detected. The As a result, when the receiver 20 receives the surface wave, the reception signal waveform D of the surface wave traveling on the path DP and the reception signal waveform R of the surface wave traveling on the path RP are closely observed.

In general, when the relationship between the surface wave frequency and the received signal waveform when a surface wave of a certain intensity is propagated to the surface layer of the material and received, the received signal waveform is sharp and the peak is observed when the surface wave frequency is high. Although the position can be easily found, the amplitude (peak height) becomes small because of the characteristic of being easily attenuated. On the other hand, if the frequency of the surface wave is low, the received new signal waveform becomes wide and it is difficult to find the peak position, but the amplitude (peak height) increases.
Here, in a large-diameter spiral steel pipe 18 having an outer diameter of 1100 mm or more, when a surface wave having a frequency of less than 0.1 MHz is transmitted from the transmitter 19 and received by the receiver 20, reception of the surface wave traveling on the path DP is received. Since both the signal waveform D and the received signal waveform R of the surface wave that has traveled along the path RP are wide, they are observed to overlap each other, and the peak position cannot be detected.
On the other hand, when a surface wave having a frequency of 0.1 MHz or more and 2 MHz or less is transmitted from the transmitter 19 and received by the receiver 20, the received signal waveforms D and R are overlapped, but the waveforms are sharply separated and observed. . Since the path DP is a path that passes through the inside of the spiral steel pipe 18, the surface wave is greatly attenuated when traveling along the path DP, and the peak height of the received signal waveform D is lowered. FIG. 4 shows an example of a received signal waveform when a surface wave having a frequency of 0.1 MHz is transmitted from the transmitter 19 onto the large-diameter spiral steel pipe 18 and received by the receiver 20.

In addition, in a large-diameter spiral steel pipe 18 having an outer diameter of 1100 mm or more, when a surface wave having a frequency exceeding 2 MHz is transmitted from the transmitter 19 and received by the receiver 20, the surface wave has a high frequency, and thus attenuation during propagation. And the attenuation of the surface wave traveling along the path DP that travels straight inside the weld bead becomes very significant. This makes it difficult to detect the received signal waveforms R and D.
When a surface wave having a frequency of 5 MHz or more is transmitted and received by the receiver 20, the surface wave is severely attenuated, and in particular, it is very difficult to detect the received signal waveform D. FIG. 5 shows an example of a received signal waveform when a surface wave having a frequency of 5 MHz is transmitted from the transmitter 19 onto the large diameter spiral steel pipe 18 and received by the receiver 20.

In the spiral steel pipe 18 having a small outer diameter of less than 1100 mm, when a surface wave having a frequency of less than 0.1 MHz is transmitted from the transmitter 19 and received by the receiver 20, the received signal waveform D of the surface wave that has traveled the path DP Since the received signal waveforms R of the surface waves that have traveled along the path RP are wide, they are observed in an overlapping manner, and the peak position cannot be detected.
On the other hand, when a surface wave having a frequency of 0.1 MHz or more and less than 1 MHz is transmitted and received by the receiver 20, the received signal waveform D of the surface wave that has traveled the path DP and the received signal waveform R of the surface wave that has traveled the path RP are Although they overlap, the waveforms become sharp and separated. However, since the surface wave traveling along the path DP is greatly attenuated, the peak height of the received signal waveform D does not become as high as the received signal waveform R even when the path length L is shortened. For this reason, although the received signal waveforms D and R can be separated, it becomes somewhat difficult. FIG. 6 shows an example of a received signal waveform when a surface wave having a frequency of 0.1 MHz is transmitted from the transmitter 19 onto the small-diameter spiral steel pipe 18 and received by the receiver 20.

On the other hand, when a surface wave having a frequency of 1 MHz or more and 5 MHz or less is transmitted from the transmitter 19 and received by the receiver 20 in the small-diameter spiral steel pipe 18 having an outer diameter of less than 1100 mm, each of the received signal waveforms D and R is However, since the waveform is sharp and the path length L of the surface wave from the transmitter 19 to the receiver 20 is short, the attenuation is small and the peak height of each of the received signal waveforms D and R is also high. Therefore, the received signal waveforms D and R are observed separately. FIG. 7 shows an example of a received signal waveform when a surface wave having a frequency of 5 MHz is transmitted from the transmitter 19 onto the small-diameter spiral steel pipe 18 and received by the receiver 20.
Further, when a surface wave having a frequency exceeding 5 MHz and less than 10 MHz is transmitted from the transmitter 19 and received by the receiver 20, the attenuation of the surface wave is increased, and the peak positions of the received signal waveforms D and R can be detected. When a surface wave having a frequency exceeding 10 MHz is transmitted and received by the receiver 20, the attenuation of the surface wave is severe and the reception signal waveforms D and R having a sufficiently large size cannot be detected.

From the above, in order to receive surface waves with the receiver 20 in the large-diameter spiral steel pipe 18 having an outer diameter of 1100 mm or more, along the outer surface of the weld bead 23 using surface waves on the low frequency side. It is advantageous to receive surface waves that have passed through the propagation path RP.
On the other hand, even when the surface wave is received by the receiver 20 in the small-diameter spiral steel pipe 18 having an outer diameter of less than 1100 mm, the path RP propagates along the outer surface of the weld bead portion 23 using the surface wave on the low frequency side. However, since the obtained received signal waveform R is wide, the detection accuracy of the peak position is lowered, and the measurement accuracy of the outer circumferential length of the spiral steel pipe 18 is also lowered.

Here, the manufacturing control standard of the small diameter spiral steel pipe 18 is accurate because, for example, when the outer diameter is 600 mm or more, the allowable range of the outer peripheral length is within 0.4% + 3 mm, and when less than 600 mm, the outer peripheral length is within 6 mm. When the outer peripheral length is determined, the measurement accuracy of the outer peripheral length is problematic. For this reason, when surface waves are received by the receiver 20 in the small-diameter spiral steel pipe 18 having an outer diameter of less than 1100 mm, surface waves on the high frequency side are used in order to increase the detection accuracy of the peak position, and the accuracy of the spiral steel pipe 18 is increased. It is preferable to receive the surface wave that has passed through the path DP that goes straight through the inside of the weld bead portion 23 corresponding to a long outer peripheral length.
From the above, as shown in FIG. 3, the first computing means 21 employs a path DP that travels straight inside the weld bead portion 23 as a propagation path when the outer diameter of the spiral steel pipe 18 is less than 1100 mm. When the outer diameter of the spiral steel pipe 18 is 1100 mm or more, a path selection unit 24 that employs a path RP that propagates along the outer surface of the weld bead part 23 is provided as a propagation path.
In addition, since each range of the outer peripheral length of the spiral steel pipe 18 to be measured, the path DP length, and the path RP length can be estimated in advance, the propagation time t _D of the surface wave passing through the path DP can be calculated from the propagation speed of the surface wave. The propagation time t _R of the surface wave passing through the path RP can be predicted. For this reason, as the route selection unit 24, for example, a gate that detects only the surface wave on the front side of the peak detected within a certain time width provided before and after the propagation time t _D or the propagation time t _{R is used} . A circuit can be used.

Next, the manufacturing method of the spiral steel pipe which concerns on one embodiment of this invention is demonstrated.
The strip 11 wound in a coil shape is supplied to the forming section 17 via the pretreatment section 15, and the strip 11 is formed into a spiral shape while being reduced by a plurality of entrance-side inner and outer surface forming rolls 16. Then, the outer peripheral side of the contact portion formed continuously between the adjacent strips 11 formed in a spiral shape is welded and integrated with the outer surface welding machine 13 to form a spiral steel pipe 18.
Here, on the outer periphery of the cross section substantially perpendicular (85 to 95 °) to the steel pipe axis of the spiral steel pipe 18 assumed within a position within 10 m, preferably within 5 m, more preferably within 2 m from the outer surface welder 13 ( On the outer surface of the spiral steel pipe 18, the transmitter 19 and the receiver 20 of the outer peripheral length measuring device 14 of the spiral steel pipe are propagated across the weld bead 23 of the spiral steel pipe 18 with a predetermined gap. Arrange so that the route is set. Note that the center-to-center distance M between the transmitter 19 and the receiver 20 is input to the second computing means 22 in advance.

At this time, when the outer diameter of the manufactured spiral steel pipe 18 is less than 1100 mm, the transmitter 19 having a frequency range of 0.1 MHz to 10 MHz, preferably 0.5 MHz to less than 10 MHz, more preferably 1 MHz to 5 MHz. And the receiver 20 are used. When the outer diameter of the spiral steel pipe is 1100 mm or more, the transmitter 19 and the receiver 20 having a frequency range of 0.1 MHz to 2 MHz, preferably 0.5 MHz to 1 MHz are used.
Further, by operating the path selector 24 provided in the first calculation means 21 of the outer peripheral length measuring device 14 of the spiral steel pipe, as shown in FIG. 3, when the outer diameter of the spiral steel pipe 18 is less than 1100 mm, welding is performed. A propagation path having a path DP that goes straight inside the bead portion 23 is selected. When the outer diameter of the spiral steel pipe 18 is 1100 mm or more, a propagation path having a path RP that propagates along the outer surface of the weld bead portion 23 is selected. Keep it.

The surface wave reception signal received by the receiver 20 through the selected propagation path is input to the first computing means 21 to obtain the propagation time, and the propagation length of the propagation path is determined using the propagation speed of the surface wave. Is calculated. Then, the calculated path length L is input to the second calculating means 22, and the outer peripheral length (L + M) of the spiral steel pipe 18 using the center-to-center distance M between the transmitter 19 and the receiver 20 input in advance. Is calculated.
Next, in the second calculation means 22, the calculated outer peripheral length (L + M) of the spiral steel pipe 18 is compared with the target outer peripheral length of the spiral steel pipe 18 to be manufactured (for example, the theoretical outer peripheral length obtained from the outer diameter of the spiral steel pipe 18). For example, a deviation amount between the outer peripheral length target value and the outer peripheral length (L + M) is calculated and sequentially input to the control device of the molding machine 12. The molding machine 12 corrects the amount of reduction of the entry-side inner / outer surface molding roll 16 of the molding unit 17 and / or the transport direction of the strip 11 in the pretreatment unit 15 according to the deviation amount sequentially input. Thereby, it is possible to sequentially correct the molding conditions of the molding machine 12 while detecting the fluctuation of the outer peripheral length of the spiral steel pipe 18 to be formed, and to prevent the manufacture of the spiral steel pipe 18 whose outer peripheral length is out of specification. it can.
The manufactured spiral steel pipe 18 is subjected to flaw detection on the weld bead 23 with the ultrasonic flaw detector 25 and is checked for the presence or absence of defects, and then cut into a predetermined length with the traveling cutting device 26 and passed to the next process via the conveying roller group 27. Transport.

Next, examples carried out for confirming the effects of the present invention will be described. Here, FIG. 8 shows the influence of the surface wave on the detection accuracy of the received signal waveform obtained when the surface wave transmitted from the transmitter is received by the receiver in the outer circumferential length measuring method of the spiral steel pipe according to the first embodiment of the present invention. FIG. 9 is an explanatory diagram showing the relationship between the frequency and the outer diameter of the spiral steel pipe, FIG. 9 is an explanatory diagram of a received signal waveform when a low-frequency surface wave is used, and FIG. 10 is a case where a low-frequency (high frequency side) surface wave is used FIG. 11 is a graph showing the change behavior of the outer peripheral length of the spiral steel pipe when the forming conditions are corrected in the manufacturing method of the spiral steel pipe according to Example 2 of the present invention, and FIG. 12 is a comparison. It is a graph which shows the change behavior of the perimeter length of a spiral steel pipe at the time of correcting the forming conditions in the manufacturing method of the spiral steel pipe concerning an example.

Example 1
Transmitter and receiver on the outer surface of a spiral steel pipe having an outer diameter of 400 to 1800 mm so that the propagation path of the surface wave is set in a cross section substantially perpendicular to the pipe axis and across the weld bead. The surface wave transmitted from the transmitter was received by the receiver. The used surface wave has a frequency range of 0.05 to 20 MHz.
At this time, when the outer diameter of the spiral steel pipe is less than 1100 mm, a path that goes straight inside the weld bead is adopted as the propagation path of the surface wave. When the outer diameter of the spiral steel pipe is 1100 mm or more, the propagation path of the surface wave is adopted. We adopted a path that propagates along the outer surface of the weld bead, and studied the measurement accuracy and ease of measurement of the propagation time of the surface wave from the received signal waveform received by the receiver. The result is shown in FIG. In FIG. 8, the case where the propagation time can be measured with high accuracy from the received signal waveform to be measured is ◯, the case where the measurement is difficult but the measurement is difficult, the case where the measurement is difficult, and the measurement accuracy cannot be used. The relationship between the frequency of the surface wave and the outer diameter of the spiral steel pipe is shown with x as the case.

In the area A _{1 in} FIG. 8, the peak position of the received signal waveform corresponding to the propagation path adopting the path that propagates along the outer surface of the weld bead portion must be detected. Therefore, the received signal waveform becomes wider as shown in FIG. 9, and the peak position of the waveform cannot be accurately detected. In the region A ₂ where the frequency of the surface wave is on the high frequency side, as shown in FIG. 10, the received signal waveform becomes sharp, and it becomes possible to detect the peak position of the waveform.
In the area B _{1 of} FIG. 8, the peak position of the received signal waveform corresponding to the propagation path adopting the path that goes straight inside the weld bead portion must be detected. However, the reception is performed because the surface wave having a low frequency is used. Since the signal waveform becomes wider, it overlaps with the received signal waveform corresponding to the propagation path adopting the path that propagates along the outer surface of the weld bead portion, and the received signal waveform to be measured cannot be accurately separated. In the region B ₂ where the frequency of the surface wave is on the high frequency side, the received signal waveform becomes sharp, so that the received signal waveform to be measured can be separated, and detection of the peak position of the waveform is possible. .

In the area C _{1 of} FIG. 8, the peak position of the received signal waveform corresponding to the propagation path that employs the path that propagates along the outer surface of the weld bead must be detected. Therefore, the attenuation of the surface wave is large and a sufficiently large received signal waveform cannot be detected. In the region C ₂ where the frequency of the surface wave is on the low frequency side, the attenuation of the surface wave is small, and it becomes possible to detect the peak position of the received signal waveform although it is difficult.
In the region D _{1 in} FIG. 8, the peak position of the received signal waveform corresponding to the propagation path adopting a path that goes straight inside the weld bead portion must be detected. However, the attenuation of the surface wave is large and the peak is sufficiently large. The received signal waveform cannot be detected. In the region D ₂ where the frequency of the surface wave is on the low frequency side, the attenuation of the surface wave becomes large, and it becomes possible to detect the peak position of the received signal waveform although it is difficult.

(Example 2)
A transmitter and receiver for a surface wave with a frequency of 1 MHz are arranged on the outer surface of a spiral steel pipe on a cross section substantially perpendicular to the steel pipe axis at a position 3 m along the steel pipe axis from the outer surface welding machine, respectively. A spiral steel pipe having an outer diameter of 1000 mm was manufactured while correcting the molding conditions of the molding machine based on the measurement result of the outer peripheral length. FIG. 11 shows the change behavior of the outer peripheral length of the manufactured spiral steel pipe. The target outer peripheral length of the spiral steel pipe having an outer diameter of 1000 mm is 3141.5 mm, the acceptable lower limit value of the outer circumferential length is 3132.1 mm, the acceptable upper limit value of the outer circumferential length is 3150.9 mm, the production control lower limit value is 312.7 mm, The management upper limit is 3150.3 mm.
As shown in FIG. 11, the spiral steel pipe having a value close to the target outer peripheral length has been manufactured since the start of the production of the spiral steel pipe, but the outer peripheral length of the spiral steel pipe tends to increase at the time T _1. It has become. However, since the outer peripheral length was measured at a position 3 m from the outer surface welder and the molding conditions of the molding machine were corrected based on the measurement result, the increase in the outer peripheral length was the upper limit of production control at time T _2. to prevent increased but thereafter increased to a value, from the point of time T ₃ has enabled the production of spiral pipe having a value close to the target circumferential length gradually reduces the circumferential length.
In this way, in order to measure the outer peripheral length of the spiral steel pipe in the early stage after it is formed and to correct the molding conditions of the molding machine based on the measurement result, the spiral steel pipe is adjusted so that the outer peripheral length is kept within the acceptable range. It was confirmed that it could be manufactured.

(Comparative example)
A transmitter and receiver for a surface wave with a frequency of 1 MHz are respectively arranged on the outer surface of the spiral steel pipe on a cross section substantially perpendicular to the steel pipe axis at a position of 11 m along the steel pipe axis from the outer surface welding machine. A spiral steel pipe having an outer diameter of 1000 mm was manufactured while correcting the molding conditions of the molding machine based on the measurement result of the outer peripheral length. The change behavior of the outer peripheral length of the manufactured spiral steel pipe is shown in FIG.
As shown in FIG. 12, the outer peripheral length of the spiral steel pipe tends to increase at the time S ₁ after starting the production of the spiral steel pipe. However, since the outer peripheral length was measured at a position 11 m from the outer surface welding machine and the molding conditions of the molding machine were corrected based on the measurement results, the time for correcting the molding conditions of the molding machine was delayed, After reaching the production control upper limit at time S ₂ and further increasing to time S ₃ , the effect of the correction appears and the outer peripheral length gradually decreases, and at time S ₄ , the production control upper limit is restored. After that, it was further reduced and it became possible to manufacture spiral steel pipes having values close to the target outer peripheral length.
As described above, when the time for performing the determination for correcting the molding conditions of the spiral steel pipe molding machine is delayed, a portion where the outer peripheral length is rejected is generated.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, The change in the range which does not change the summary of invention is possible, Each above-mentioned embodiment is possible. The case where the outer peripheral length measuring method and apparatus for the spiral steel pipe of the present invention and the spiral steel pipe manufacturing method and equipment thereof are configured by combining some or all of the forms and modifications are also included in the scope of the present invention.
For example, although the transmitter and the receiver are arranged separately with a predetermined gap, they may be arranged and integrated so that the transmission direction of the transmitter and the reception direction of the receiver are opposite. In the embodiment, the transmitter and the receiver are arranged at a position 3 m along the steel pipe axis from the outer surface welder. However, if the position is within 10 m along the steel pipe axis from the outer surface welder, the spiral steel pipe It can be installed according to the situation of manufacturing equipment.

It is explanatory drawing of the manufacturing equipment of the spiral steel pipe which concerns on one embodiment of this invention. It is explanatory drawing of the outer periphery length measuring apparatus of the spiral steel pipe used for the manufacturing equipment of the spiral steel pipe. It is explanatory drawing which shows the propagation path of the surface wave which propagates the weld bead part in the outer peripheral length measuring method of the spiral steel pipe applied to the manufacturing method of the spiral steel pipe which concerns on one embodiment of this invention. It is explanatory drawing which shows the received signal waveform obtained when the surface wave of the frequency of 0.1 MHz transmitted from the transmitter in the large diameter spiral steel pipe is received by the receiver. It is explanatory drawing which shows the received signal waveform obtained when the surface wave of frequency 5MHz transmitted from the transmitter in the large diameter spiral steel pipe is received by the receiver. It is explanatory drawing which shows the received signal waveform obtained when the surface wave of the frequency 0.1MHz transmitted from the transmitter in the small diameter spiral steel pipe is received by the receiver. It is explanatory drawing which shows the received signal waveform obtained when the surface wave of frequency 5MHz transmitted from the transmitter in the small diameter spiral steel pipe is received by the receiver. The influence of the surface wave frequency and the outside of the spiral steel pipe on the detection accuracy of the received signal waveform obtained when the surface wave transmitted from the transmitter is received by the receiver in the method for measuring the outer peripheral length of the spiral steel pipe according to the first embodiment of the present invention. It is explanatory drawing which shows the relationship of a diameter. It is explanatory drawing of a received signal waveform at the time of using a surface wave with a low frequency. It is explanatory drawing of a received signal waveform at the time of using a surface wave with a low frequency. It is a graph which shows the change behavior of the perimeter length of a spiral steel pipe at the time of correcting the forming conditions in the manufacturing method of the spiral steel pipe concerning Example 2 of the present invention. It is a graph which shows the change behavior of the perimeter length of a spiral steel pipe at the time of correcting the forming conditions in the manufacturing method of the spiral steel pipe concerning a comparative example. It is explanatory drawing of the outer periphery length measuring apparatus of the steel pipe which concerns on a prior art example. It is explanatory drawing of the outer peripheral length measuring apparatus of the steel pipe which concerns on another prior art example. It is explanatory drawing of the outer periphery length measuring method of the spiral steel pipe which concerns on a prior art example. It is explanatory drawing at the time of measuring pipe circumference using the ultrasonic distance measuring device which concerns on a prior art example.

Explanation of symbols

10: Manufacturing equipment for spiral steel pipe, 11: Strip plate, 12: Molding machine, 13: Outer surface welding machine, 14: Peripheral length measuring device for spiral steel pipe, 15: Pretreatment section, 16: Inner inner / outer surface molding roll, 17 : Forming part, 18: spiral steel pipe, 19: transmitter, 20: receiver, 21: first calculation means, 22: second calculation means, 23: weld bead part, 24: path selection part, 25: super Sonic flaw detector 26: traveling cutting device 27: transport roller group

Claims (4)

A surface wave transmitter and receiver are arranged on the outer surface of a spiral steel pipe having an outer diameter of less than 1100 mm,
Setting the propagation path of the surface wave in a cross section substantially perpendicular to the steel pipe axis of the spiral steel pipe, and across the weld bead portion of the spiral steel pipe,
Obtain the propagation time of the surface wave from the transmitter to the receiver and calculate the path length of the propagation path using the propagation speed of the surface wave,
A method for measuring the outer peripheral length of a spiral steel pipe that calculates the outer peripheral length of the spiral steel pipe from the distance between the transmitter and the receiver and the path length,
The frequency range of the surface waves detected by the receiving element and the 0.1MHz or 10MHz or less, along the outer surface of the peaks and the weld bead portion of the waveform D corresponding to the path for straight interior of the weld bead portion The peak of the waveform D that appears first among the peaks of the waveform R corresponding to the path of propagation is selected, and the propagation time of the surface wave is obtained based on the peak of the waveform D. Perimeter length measurement method. It is arranged on the outer surface of the spiral steel pipe with a predetermined gap on a cross section substantially perpendicular to the steel pipe axis of the spiral steel pipe, and transmits and receives surface waves across the weld bead portion of the spiral steel pipe. A transmitter and receiver;
First calculating means for obtaining a propagation time of the surface wave from the transmitter to the receiver and calculating a path length of the propagation path using a propagation speed of the surface wave;
An apparatus for measuring the outer peripheral length of a spiral steel pipe having a second computing means for calculating the outer peripheral length of the spiral steel pipe from the distance between the transmitter and the receiver and the path length,
When the outer diameter of the spiral steel pipe is less than 1100 mm, the frequency range of the surface wave transmitter and receiver is 0.1 MHz or more and 10 MHz or less, and 0.15 MHz or more when the outer diameter of the spiral steel pipe is 1100 mm or more. detected by follows to the receiving element, the peak of the waveform R corresponding to the path that propagates along the outer surface of the peaks and the weld bead portion of the waveform D corresponding to the path for straight interior of the weld bead portion home,
In the first calculation means, when the outer diameter of the spiral steel pipe is less than 1100 mm , the peak of the waveform D that appears first is selected, and when the outer diameter of the spiral steel pipe is 1100 mm or more , it appears with a delay. An apparatus for measuring the outer peripheral length of a spiral steel pipe, wherein a path selection unit for selecting a peak of the waveform R is provided. In a method for manufacturing a spiral steel pipe, a band plate is formed into a spiral shape with a molding machine, and the outer surface side of the band plate is welded with an outer surface welding machine to form a spiral steel pipe.
The outer peripheral length of the spiral steel pipe was measured at a position within 10m from the outer surface welding machine using the circumferential length measurement method of the spiral steel pipe according to claim 1 Symbol placement, correct the forming conditions of the molding machine based on the measurement result A method of manufacturing a spiral steel pipe, characterized in that: A molding machine for forming a strip into a spiral shape;
An outer surface welding machine for forming a spiral steel pipe by welding the outer surface side of the strip formed into a spiral shape;
It has a peripheral length measuring device of spiral steel pipe according to claim 2 ,
The outer peripheral length measuring device of the spiral steel pipe is installed within 10 m from the outer surface welding machine, and the forming condition of the molding machine is corrected based on the measurement result of the outer peripheral length of the spiral steel pipe. Facility.

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