Ultrasonic Flaw Detection Device

Abstract

To provide an ultrasonic flaw detector that can increase the ability of detecting an internal defect.SOLUTION: An ultrasonic flaw detector 1 includes: a probe block 2 having a through-hole 21 for causing a steel pipe 10 to pass through; a plurality of ultrasonic flaw detectors 3 arranged in an internal surface 21a of the through-hole 21 of the probe block 2 and emitting an ultrasonic wave to an outer peripheral surface 10c of the steel pipe 10 when the steel pipe is passing through the through-hole 21; and an adjusting unit 7 stored in the probe block 2, the adjusting unit adjusting the attitude of the ultrasonic flaw detector 3. The adjusting unit 7 can change the direction of emitting an ultrasonic wave to the steel pipe 10 along a direction perpendicular to the direction in which the steel pipe 10 passes.SELECTED DRAWING: Figure 1

Description

[[Technical Field]]

[0001] The present invention relates to an ultrasonic flaw detector, a method for adjusting an ultrasonic flaw detector, and an ultrasonic flaw detection method for a steel pipe. [[Background Art]]

[0002] An ultrasonic flaw detection method is known as a method for non-destructively detecting internal defects in steel materials. In the ultrasonic flaw detection method, an ultrasonic probe is opposed to one surface of a steel material serving as a test object, an ultrasonic wave generated by the ultrasonic probe is incident into the steel material, the ultrasonic wave propagates through the steel material, and an internal defect or a reflected wave of the ultrasonic wave from the other surface of the steel material is detected as an echo, thereby attempting to measure internal defects inside the steel material.

[0003] Fig. 12(a) is a schematic cross-sectional view when the ultrasonic flaw detection method is applied to a bar steel material. The ultrasonic wave S emitted from the ultrasonic probe 303 and incident into the bar steel material 410 is reflected inside the bar steel material 410 with the surface 410a acting as a reflecting surface when the ultrasonic wave S hits the surface 410a from the inside of the bar steel material, and the reflected wave is further reflected again on another surface. If there is an internal defect within the propagation range of the ultrasonic wave S, a part of the ultrasonic wave S is reflected at the internal defect, and the reflected wave is received by the ultrasonic probe 303, thereby detecting the internal defect.

[0004] In the case of the bar steel material 410, as shown in Fig. 12(a), the shape of the surface 410a of the bar steel material 410 is a concave curved surface with respect to the irradiation direction of the ultrasonic wave S from the inside of the bar steel material 410, so the ultrasonic wave S propagating inside the bar steel material 410 is converged every time it is reflected. Therefore, when ultrasonic flaw detection is performed on the bar steel material 410, the signal-to-noise ratio (hereinafter referred to as the S / N ratio), which is the ratio of the signal from the internal defect to the background noise level, becomes relatively high, thereby improving the flaw detection capability. When an internal defect exists in the vicinity of the surface 410a of the bar steel material 410, the distance between the internal defect and the surface 410a is short, so the S / N ratio becomes relatively low, making it difficult to detect the internal defect. However, due to the recent improvement in technical capability, even a micro defect with a depth of 0.1 mm processed on the surface 410a can be detected with a high S / N ratio.

[0005] On the other hand, Figure 12(b) shows a schematic cross-sectional view when ultrasonic testing is applied to a steel pipe 310. The ultrasonic waves S emitted from the ultrasonic flaw detector 303 and incident on the interior of the thickened portion 310a of the steel pipe 310 are reflected inside the thickened portion 310a by the inner circumferential surface 310b of the steel pipe 310, which acts as a reflective surface, and the reflected waves are re-reflected on the outer circumferential surface 310c of the steel pipe 310. In the case of a steel pipe 310, the inner circumferential surface 310b, which is the surface on which the ultrasonic waves S are first reflected, is a convex curved surface with respect to the direction of irradiation of the ultrasonic waves S, so the ultrasonic waves S propagating inside the steel pipe 310 are diverged at this convex curved surface. For this reason, when ultrasonic testing is performed on a steel pipe 310, the signal-to-noise ratio is lower compared to the case of a steel bar 410. Therefore, the ability to detect internal defects in the thickened portion 310a of the steel pipe 310 is limited to detecting artificial defects with a depth of 0.2 mm from the surface 310b and 310c. In ultrasonic testing, the signal-to-noise ratio is generally lower than that of the steel bar 410, and only relatively large defects with large reflected echoes can be detected.

[0006] Incidentally, in recent years, due to the demand for lighter parts in the automotive sector, there has been a growing trend to replace solid components with hollow components. For example, while automobile drive shafts traditionally used solid components obtained by processing steel bars, recent demands for weight reduction have led to the increasing use of hollow components obtained by processing steel pipes. Although hollow components are lightweight, the presence of a hollow section means that the requirements for strength and fatigue characteristics are becoming increasingly stringent. Therefore, there is a need to improve the ability to detect internal defects in the thicker sections of steel pipes. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 3-289560 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention has been made in view of the above circumstances, and aims to provide an ultrasonic flaw detection device, a method for adjusting the ultrasonic flaw detection device, and a method for ultrasonic flaw detection of steel pipes, which are capable of improving the ability to detect internal defects in steel pipes. [Means for solving the problem]

[0009] To solve the above problems, the inventors of this invention conducted diligent research and found that optimizing the direction of ultrasonic irradiation on the steel pipe makes it possible to improve the ability to detect internal defects in the steel pipe. Therefore, the present invention adopts the following configuration. [1] A probe block having a through hole for passing a steel pipe, A plurality of ultrasonic flaw detectors are disposed on the inner surface of the through-hole of the probe block and capable of emitting ultrasonic waves toward the outer surface of the steel pipe as it passes through the through-hole, The probe block is equipped with an adjustment unit that is built into it to adjust the orientation of the ultrasonic flaw detector, The adjustment unit allows the direction of irradiation of the ultrasonic waves onto the steel pipe to be changed along a direction perpendicular to the direction of passage of the steel pipe, in an ultrasonic flaw detection device. [2] The ultrasonic flaw detection apparatus according to [1], wherein the ultrasonic flaw detector is arranged on the probe block such that the focal position of the ultrasonic waves emitted from the ultrasonic flaw detector is located on the inner surface of the steel pipe. [3] A probe block having a through hole for passing a steel pipe, The probe block is provided with a plurality of ultrasonic flaw detectors, which are disposed on the inner surface of the through-hole and capable of emitting ultrasonic waves toward the outer surface of the steel pipe as it passes through the through-hole. An ultrasonic flaw detection apparatus in which the ultrasonic flaw detector is arranged on the probe block such that the focal point of the ultrasonic waves emitted from the ultrasonic flaw detector is located on the inner circumferential surface of the steel pipe. [4] Guide members are provided on the entry and exit sides of the probe block in the direction of passage of the steel pipe, to fix the position of the steel pipe within the through hole. The ultrasonic flaw detection apparatus according to any one of [1] to [3], wherein at least the entry-side guide member is positioned adjacent to the through-hole of the probe block. [5] A water supply unit is further provided to supply water to the gap between the inner surface of the through hole and the steel pipe, An ultrasonic flaw detection apparatus according to any one of [1] to [4], wherein a flow straightening wall for guiding water discharged from the through hole is provided on the inlet side of the probe block in the direction of passage of the steel pipe, surrounding the inlet opening of the through hole. [6] The ultrasonic flaw detection apparatus according to [5], wherein a porous material is laminated on the surface of the rectifier wall. [7] A probe block having a through hole for passing a steel pipe, A method for adjusting an ultrasonic flaw detection apparatus comprising: a plurality of ultrasonic flaw detectors disposed on the inner surface of the through-hole of the probe block and capable of emitting ultrasonic waves toward the outer surface of the steel pipe passing through the through-hole; The steps include inserting a test piece made of a hollow cylindrical steel material having a simulated defect on its surface into the through hole of the probe block, The steps include: performing a flaw detection on the simulated defect using the ultrasonic flaw detector; A method for adjusting an ultrasonic flaw detection apparatus, comprising the step of adjusting the direction of irradiation of the ultrasonic waves to the test piece along a direction perpendicular to the longitudinal direction of the test piece so that the signal-to-noise ratio of the output signal of the ultrasonic flaw detector is maximized when inspecting the simulated defect. Using a probe block and ultrasonic flaw detector adjusted according to the adjustment method for ultrasonic flaw detection equipment described in [8] [7], An ultrasonic testing method for steel pipes, comprising passing the steel pipe through a through-hole in the probe block while using the ultrasonic flaw detector to inspect for internal defects in the steel pipe. [9] The ultrasonic flaw detection method for a steel pipe according to [8], wherein the focal position of the ultrasonic waves emitted from the ultrasonic flaw detector is positioned on the inner surface of the steel pipe, and internal defects of the steel pipe are detected. [Effects of the Invention]

[0010] The ultrasonic flaw detection apparatus of the present invention is equipped with an adjustment unit for adjusting the orientation of the ultrasonic flaw detector. The adjustment unit allows the irradiation position of the ultrasonic waves onto the steel pipe to be changed along a direction perpendicular to the direction of passage of the steel pipe. This makes it possible to set the irradiation direction of the ultrasonic waves onto the outer surface of the steel pipe to an appropriate direction, thereby improving the flaw detection capability of the ultrasonic flaw detection apparatus. Furthermore, according to the ultrasonic flaw detection apparatus of the present invention, the ultrasonic flaw detector is arranged in the probe block such that the focal point of the ultrasonic waves emitted from the ultrasonic flaw detector is located on the inner surface of the steel pipe. As a result, the divergence of ultrasonic waves incident on the inside of the thickened portion of the steel pipe is suppressed, which increases the signal-to-noise ratio (S / N ratio) of the output signal when detecting internal defects, thereby improving the internal defect detection capability of the ultrasonic flaw detection apparatus. Furthermore, according to the ultrasonic flaw detection apparatus of the present invention, guide members are provided on the entry and exit sides of the probe block in the direction through which the steel pipe passes, and at least the entry-side guide member is positioned adjacent to the through-hole of the probe block. As a result, the amount of deflection due to the weight of the tip of the steel pipe when passing through the through-hole is reduced, allowing the steel pipe to pass through the probe block stably. This improves the signal intensity of internal defects and further improves the signal-to-noise ratio. Furthermore, the ultrasonic flaw detection apparatus of the present invention is equipped with a water supply unit that supplies water to the gap between the inner surface of the through-hole and the steel pipe. In addition, a flow straightening wall is provided on the inlet side of the probe block in the direction of passage of the steel pipe, surrounding the opening on the inlet side of the through-hole to guide the water discharged from the through-hole, so that the water discharged from the through-hole is collected by flowing along the flow straightening wall. As a result, when multiple steel pipes are continuously supplied to the ultrasonic flaw detection apparatus, the risk of water entering the hollow part of the subsequent steel pipe is reduced, noise is reduced, and the signal-to-noise ratio can be further improved. Furthermore, according to the ultrasonic flaw detection device of the present invention, since a porous material is laminated on the surface of the flow straightening wall, water discharged from the through hole is collected along the flow straightening wall and held in the porous material, so the risk of water entering the hollow part of the subsequent steel pipe is greatly reduced, noise is reduced and the signal-to-noise ratio can be further improved.

[0011] Next, according to the adjustment method for the ultrasonic flaw detection apparatus of the present invention, a test piece made of a hollow cylindrical steel material with a simulated defect on its surface is inserted into a through-hole of the probe block, and the direction of ultrasonic irradiation to the test piece is adjusted along a direction perpendicular to the longitudinal direction of the test piece so that the signal-to-noise ratio of the output signal of the ultrasonic flaw detector is maximized when inspecting the simulated defect, thereby improving the ability to detect internal defects in the ultrasonic flaw detection apparatus.

[0012] Next, according to the ultrasonic flaw detection method for steel pipes of the present invention, by using a probe block and ultrasonic flaw detector adjusted by the ultrasonic flaw detection device adjustment method described above, the internal defects of the steel pipe are detected by the ultrasonic flaw detector while passing the steel pipe through the through-hole of the probe block, thereby improving the ability to detect internal defects. In particular, in the conventional method, the size of artificial defects that could be detected in a steel pipe under conditions with a relatively good S / N ratio was a relatively deep artificial defect with a depth of 0.2 mm. However, according to the present invention, it is possible to detect shallow (minor) artificial defects with a depth of 0.1 mm with a high S / N ratio at a similar level, thereby significantly improving the performance of detecting internal defects in steel pipes. Furthermore, according to the ultrasonic flaw detection method for steel pipes of the present invention, since the focal point of the ultrasonic waves emitted from the ultrasonic flaw detector is positioned on the inner surface of the steel pipe, internal defects in the steel pipe are detected. This suppresses the divergence of ultrasonic waves incident on the thicker parts of the steel pipe, increases the signal-to-noise ratio of the output signal when internal defects are detected, and improves the flaw detection capability. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic side view showing an ultrasonic flaw detection apparatus, which is an embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view showing a probe block provided in an ultrasonic flaw detection device according to an embodiment of the present invention. [Figure 3] Figure 3 shows a probe block, where (a) is a schematic front view, (b) is a schematic cross-sectional view corresponding to line A-A' in Figure 2, and (c) is a schematic cross-sectional view showing the ultrasonic flaw detector arranged within the probe block. [Figure 4] Figure 4 is an enlarged schematic cross-sectional view showing an ultrasonic flaw detector disposed in a probe block. [Figure 5] Figure 5 is a schematic cross-sectional view illustrating the relationship between a steel pipe and the focal position of ultrasonic waves. [Figure 6] Figure 6 is a diagram illustrating a method for adjusting an ultrasonic flaw detector according to an embodiment of the present invention, wherein (a) is an overall view of a test piece, and (b) is a schematic cross-sectional view showing a state where the test piece is inserted into a through-hole of a probe block. [Figure 7] Figure 7 is a cross-sectional view corresponding to line B-B' of Figure 6(b), and is a schematic cross-sectional view showing a state where a test piece is inserted into a through-hole of a probe block. [Figure 8] Figure 8 is a schematic cross-sectional view illustrating a state where the orientation of the ultrasonic flaw detector is adjusted with a test piece inserted into a through-hole of the probe block. [Figure 9] Figure 9 is a schematic side view showing another example of the ultrasonic flaw detector according to an embodiment of the present invention. [Figure 10] Figure 10 is a schematic side view showing still another example of the ultrasonic flaw detector according to an embodiment of the present invention. [Figure 11] Figure 11 is a schematic cross-sectional view showing a probe block provided in the ultrasonic flaw detector shown in Figure 10. [Figure 12] Figure 12 is a schematic diagram illustrating how ultrasonic waves propagate inside a steel material, wherein (a) is a schematic cross-sectional view showing a case where the steel material is a bar / wire rod, and (b) is a schematic cross-sectional view showing a case where the steel material is a steel pipe. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an ultrasonic flaw detector, a method for adjusting an ultrasonic flaw detector, and an ultrasonic flaw detection method for a steel pipe according to embodiments of the present invention will be described.

[0015] (Ultrasonic Flaw Detector and Ultrasonic Flaw Detection Method for Steel Pipe) Figure 1 shows a schematic side view of the ultrasonic flaw detection apparatus 1 of this embodiment, and Figures 2 and 3 show the probe block 2 provided in the ultrasonic flaw detection apparatus 1. As shown in Figure 1, the ultrasonic flaw detection apparatus 1 of this embodiment includes a probe block 2 having a through hole 21, a plurality of ultrasonic flaw detectors 3 arranged on the inner surface 21a of the through hole 21 of the probe block 2, an inlet-side transport roll 4 that transports the steel pipe 10 to the probe block 2, and an outlet-side transport roll 5 that transports the steel pipe 10 after it has passed through the probe block 2. Furthermore, guide members 6 are arranged on the inlet and outlet sides of the probe block 2. Figure 1(a) shows the stage before the steel pipe 10 passes through the probe block 2, and Figure 1(b) shows the stage while the steel pipe 10 is passing through the probe block 2.

[0016] As shown in Figure 1, the probe block 2 is rotatable around an axis L that passes through the center of the through-hole 21. Water is supplied to the through-hole 21 of the probe block 2 from a water supply unit (not shown).

[0017] As shown in Figures 2 and 3, the probe block 2 has, for example, a cylindrical outer shape, and a through-hole 21 is provided inside along its longitudinal direction. The steel pipe 10 to be measured passes through the through-hole 21. A recess 21b is provided on the inner surface 21a of the through-hole 21, and an ultrasonic flaw detector 3 is arranged in the recess 21b. In the example shown in Figure 3, four ultrasonic flaw detectors 3 are arranged along the circumferential direction of the inner surface 21a of the through-hole 21. The number of ultrasonic flaw detectors 3 can be any number and is not limited to four.

[0018] Furthermore, as shown in Figures 2 and 3, the probe block 2 is provided with a water conduit 21c. The water conduit 21c penetrates between the outer surface 2a of the probe block 2 and the inner surface 21a of the through hole 21. Water is supplied to the through hole 21 via a water supply unit (not shown) and the water conduit 21c, which are installed outside the probe block 2.

[0019] Furthermore, the probe block 2, along with the ultrasonic flaw detector 3 provided on the probe block 2, is detachably attached to the ultrasonic flaw detection device 1 in order to perform the adjustment method described later.

[0020] Each ultrasonic flaw detector 3 emits ultrasonic waves toward the steel pipe 10 passing through the through hole 21, and receives echoes reflected from the steel pipe 10, outputting the received signal as an output signal. When an internal defect is detected, a peak originating from the internal defect appears in the output signal. By analyzing this peak, the location of the internal defect in the thickened portion 10a of the steel pipe 10 can be determined. The ultrasonic flaw detector 3 is equipped with an ultrasonic wave emitter and a receiving unit (not shown), and these emitter and receiving units are directed toward the through hole 21.

[0021] Furthermore, as shown in Figures 2 and 3, the probe block 2 incorporates an adjustment unit 7 for adjusting the orientation of the ultrasonic flaw detector 3. The adjustment unit 7 adjusts the mounting angle of the ultrasonic flaw detector 3. Specifically, as shown in Figures 2 and 3, the adjustment unit 7 consists of a long rod 7a that penetrates the probe block 2 along the through hole 21, and an operating unit 7c provided at one end 7b of the rod 7a. The rod 7a is positioned, for example, parallel to the axis L of the through hole 21. Both the operating unit 7c and the rod 7a are rotatable around the axis of the rod 7a. The ultrasonic flaw detector 3 is connected to the other end 7d of the rod 7a, and the ultrasonic flaw detector 3 is also rotatable in conjunction with the rotation of the rod 7a. This makes it possible to change the angle of ultrasonic irradiation of the steel pipe passing through the through hole 21 by the ultrasonic flaw detector 3. Figure 4 shows how the orientation of the ultrasonic flaw detector 3 is changed by the adjustment unit 7. By rotating the operating unit 7c, the ultrasonic flaw detector 3 is rotated, thereby changing the direction of ultrasonic irradiation onto the steel pipe 10 to a direction perpendicular to the direction of passage of the steel pipe 10.

[0022] Furthermore, as shown in Figure 5(b), it is preferable that the ultrasonic flaw detector 3 is positioned on the probe block 2 such that the focal point F of the ultrasonic waves emitted from the ultrasonic flaw detector 3 is located on the inner circumferential surface 10b of the steel pipe 10. Specifically, the ultrasonic flaw detector 3 should be positioned in the recess 21b of the probe block 2 such that the distance from the emitter of the ultrasonic flaw detector 3 to the inner circumferential surface 10b of the steel pipe 10 matches the focal length of the ultrasonic waves in the ultrasonic flaw detector 3.

[0023] As shown in Figure 1, the guide members 6 are positioned on the inlet and outlet sides of the probe block 2, respectively, and have guide holes 6a for guiding the steel pipe 10. When the steel pipe 10 passes through the through hole 21 of the probe block 2, its position within the through hole 21 is positioned by the inlet and outlet guide members 6. This makes it possible to maintain a constant distance between the steel pipe 10 and the ultrasonic flaw detector 3 during transport, enabling stable detection of internal defects.

[0024] Next, the ultrasonic flaw detection method for steel pipes according to this embodiment will be described. As shown in Figure 1(a), a steel pipe 10 is placed on the inlet side of the probe block 2, and the steel pipe 10 is brought closer to the probe block 2 by the transport roll 4 on the inlet side. The orientation of the ultrasonic flaw detector 3 in the probe block 2 is adjusted in advance using a test piece 31. The method for adjusting the ultrasonic flaw detector 3 using the test piece 31 will be described later.

[0025] Next, the steel pipe 10 is guided by the guide member 6 on the entry side and inserted into the through hole 21 of the probe block 2. Water is also supplied to the through hole 21 via the water conduit 21c, forming a layer of water in the gap between the inner surface 21a of the through hole 21 and the outer surface 10c of the steel pipe 10. Then, while rotating the probe block 2 around axis L, flaw detection with the ultrasonic flaw detector 3 is started. The ultrasonic waves emitted from the ultrasonic flaw detector 3 are incident on the thickened portion 10a of the steel pipe 10 through the layer of water, and internal defects are detected. By rotating the probe block 2 while moving the steel pipe 10, the trajectory of the ultrasonic flaw detector 3 on the outer surface 10c of the steel pipe 10 becomes a spiral trajectory, and flaw detection with the ultrasonic flaw detector 3 is performed on the entire thickened portion 10a of the steel pipe 10.

[0026] The position of the ultrasonic flaw detector 3, which is mounted on the probe block 2, is adjusted in advance by the test piece 31 to the optimal angle, making it possible to inspect the steel pipe 10 under conditions where the signal-to-noise ratio of internal defects is high.

[0027] Furthermore, as shown in Figure 5(b), it is preferable to perform flaw detection of internal defects in the steel pipe 10 with the focal point F of the ultrasonic waves emitted from the ultrasonic flaw detector 3 positioned on the inner circumferential surface 10b of the steel pipe 10. When ultrasonic waves are incident on the thickened portion 10a of the steel pipe 10, the inner circumferential surface 10b of the steel pipe 10 becomes the first reflective surface and reflects the ultrasonic waves. However, since this inner circumferential surface 10b is a convex curved surface with respect to the direction of ultrasonic wave irradiation, the ultrasonic waves tend to diverge at the inner circumferential surface 10b. Conventionally, as shown in Figure 5(a), the focal point F of the ultrasonic waves was positioned on the outer circumferential surface 10c of the steel pipe 10, so by the time the ultrasonic waves reached the inner circumferential surface 10b, they had spread out and were diverged more widely by the inner circumferential surface 10b. However, as in this embodiment shown in Figure 5(b), by positioning the focal point F of the ultrasonic waves on the inner circumferential surface 10b of the steel pipe 10, the irradiation range of the ultrasonic waves on the inner circumferential surface 10b is reduced, and divergence due to ultrasonic wave reflection is suppressed. This improves the signal-to-noise ratio of the output signal of the ultrasonic flaw detector 3, thereby further enhancing its ability to detect internal defects.

[0028] Next, we will explain how to adjust the orientation of the ultrasonic flaw detector 3 in the probe block 2. The adjustment method for the ultrasonic flaw detection apparatus 1 of this embodiment includes the steps of: inserting a test piece 31 made of a hollow cylindrical steel material having a simulated defect portion 31a on its surface into a through hole 21 of the probe block 2; performing flaw detection on the simulated defect portion 31a with the ultrasonic flaw detector 3; and adjusting the direction of ultrasonic irradiation to the test piece 31 along a direction perpendicular to the longitudinal direction of the test piece 31 so that the signal-to-noise ratio of the output signal of the ultrasonic flaw detector 3 when the simulated defect portion 31a is detected is maximized. The details are explained below.

[0029] In the adjustment method of the ultrasonic flaw detection apparatus 1 of this embodiment, the test piece 31 shown in Figure 6(a) is used. The test piece 31 consists of a hollow cylindrical steel material 32, a fixing rod 33 attached to the lower end of the steel material 32, and an operating rod 34 attached to the upper end. The hollow cylindrical steel material 32 simulates the steel pipe 10 to be measured, and simulated defect portions 31a are provided on the outer and inner surfaces, respectively. The simulated defect portions 31a are recesses with a depth of 0.1 mm, and there are two types of recesses: recesses extending in the longitudinal direction (L direction) of the steel material 32 and recesses extending in the circumferential direction (C direction). This makes it possible to simulate internal defects of the steel pipe 10 that extend in the L direction or the C direction. The position of the simulated defect portions 31a is predetermined so that they face the ultrasonic flaw detector 3 when the test piece 31 is inserted into the probe block 2.

[0030] Next, the test piece 31 is inserted into the through-hole 21 of the probe block 2. The probe block 2 has been removed from the ultrasonic flaw detection device 1 beforehand. As shown in Figures 6(b) and 7, the probe block 2 is placed in a predetermined position on the base 30 such that the axis L of the through-hole 21 of the probe block 2 is oriented vertically and the operating part 7c of the adjustment unit 7 is facing upwards. Then, the test piece 31 is inserted into the through-hole 21 from above the probe block 2, and the tip of the fixing rod 33 of the test piece 31 is inserted into the recess 30a of the base 30. This positions the test piece 31 within the through-hole 21 relative to the probe block 2. Figure 7 shows a cross-sectional view along the line B-B' in Figure 6(b). By positioning the probe block 2 so that the axis L of the through-hole 21 is oriented vertically, and inserting the test piece 31 so that its longitudinal direction is oriented vertically, the test piece 31 can be stably held in the center of the through-hole 21 without bending, making it possible to properly align all ultrasonic flaw detectors 3.

[0031] Next, the through-hole 21 is filled with water, forming a water layer between the inner surface 21a of the through-hole 21 of the probe block 2 and the outer surface of the steel material 32 of the test piece 31.

[0032] Next, as shown in Figure 8(a), the ultrasonic flaw detector 3(3a) is activated to inspect the simulated defect 31a and output a signal. A peak originating from the simulated defect 31a appears in the output signal of the ultrasonic flaw detector 3a. The signal-to-noise ratio (S / N ratio) is determined from the height of this peak and the background noise level.

[0033] Here, if the mounting angle of the ultrasonic flaw detector 3 is not appropriate, and the orientation of the ultrasonic flaw detector 3 is not facing the correct direction, the signal-to-noise ratio (S / N ratio) of the output signal will decrease. Therefore, it is necessary to adjust the orientation of the ultrasonic flaw detector 3a to the correct direction while monitoring the S / N ratio. In this case, by operating the operating section 7c of the probe block 2, the direction of ultrasonic irradiation onto the test piece 31 by the ultrasonic flaw detector 3a is adjusted along a direction perpendicular to the longitudinal direction of the test piece 31. Then, the mounting angle of the ultrasonic flaw detector 3a is adjusted to the angle that maximizes the S / N ratio of the output signal, and the ultrasonic flaw detector 3a is fixed in place. This operation is performed for all ultrasonic flaw detectors 3. Figure 8(b) shows the process of adjusting the position of another ultrasonic flaw detector 3b.

[0034] As described above, by adjusting the direction of ultrasonic irradiation from the ultrasonic flaw detector 3 to the test piece 31 so that the signal-to-noise ratio of the output signal of the ultrasonic flaw detector 3 is maximized when inspecting the simulated defect 31a, the ultrasonic flaw detector 3 can be positioned in the optimal location.

[0035] Furthermore, it is preferable to adjust the position of the ultrasonic flaw detector 3 each time a predetermined number of steel pipes 10 are inspected, or at predetermined intervals. This ensures that the ultrasonic flaw detector 3 is always positioned in the optimal location.

[0036] As described above, the ultrasonic flaw detection device 1 of this embodiment is equipped with an adjustment unit 7 for adjusting the orientation of the ultrasonic flaw detector 3. This adjustment unit 7 allows the irradiation position of the ultrasonic waves onto the steel pipe 10 to be changed along a direction perpendicular to the direction of passage of the steel pipe 10. Therefore, it becomes possible to set the irradiation direction of the ultrasonic waves onto the outer surface of the steel pipe 10 to an appropriate direction, thereby improving the flaw detection capability of the ultrasonic flaw detection device 1.

[0037] Furthermore, according to the ultrasonic flaw detection device 1 of this embodiment, the ultrasonic flaw detector 3 is positioned on the probe block 2 such that the focal point of the ultrasonic waves emitted from the ultrasonic flaw detector 3 is located on the inner circumferential surface 10b of the steel pipe 10. This suppresses the divergence of ultrasonic waves incident on the inside of the thickened portion 10a of the steel pipe 10, thereby increasing the signal-to-noise ratio of the output signal when detecting internal defects and improving the internal defect detection capability of the ultrasonic flaw detection device 1.

[0038] Furthermore, according to the adjustment method of the ultrasonic flaw detection device 1 of this embodiment, a test piece 31 made of a hollow cylindrical steel material 32 having a simulated defect portion 31a on its surface is inserted into the through hole 21 of the probe block 2, and the direction of irradiation of ultrasonic waves to the test piece 31 is adjusted along a direction perpendicular to the longitudinal direction of the test piece 31 so that the signal-to-noise ratio of the output signal of the ultrasonic flaw detector 3 is maximized when inspecting the simulated defect portion 31a. This improves the ability of the ultrasonic flaw detection device 1 to detect internal defects.

[0039] Furthermore, according to the ultrasonic flaw detection method for steel pipes of this embodiment, the probe block 2 and ultrasonic flaw detector 3, which have been adjusted by the adjustment method for the ultrasonic flaw detection device 1 described above, are used to inspect for internal defects in the steel pipe 10 by passing the steel pipe 10 through the through-hole 21 of the probe block 2 with the ultrasonic flaw detector 3, thereby improving the flaw detection capability. In particular, in the conventional method, the size of artificial defects that could be inspected in a steel pipe under conditions with a relatively good S / N ratio was a relatively deep artificial defect with a depth of 0.2 mm. However, according to the present invention, it is possible to inspect shallow (minor) artificial defects with a depth of 0.1 mm with a similar S / N ratio, thereby significantly improving the flaw detection capability for internal defects in steel pipes.

[0040] Furthermore, according to the ultrasonic flaw detection method for steel pipes of this embodiment, the focal point F of the ultrasonic waves emitted from the ultrasonic flaw detector 3 is positioned on the inner circumferential surface 10b of the steel pipe 10, and since the internal defects of the steel pipe 10 are detected, the divergence of ultrasonic waves incident into the thickened portion 10a of the steel pipe 10 is suppressed, the signal-to-noise ratio of the output signal when detecting internal defects is increased, and the ability to detect internal defects is further improved.

[0041] In fact, when the ultrasonic flaw detection method for steel pipes according to this embodiment was implemented for two months on an actual steel pipe inspection line, the signal-to-noise ratio (S / N ratio) of the output signal when detecting an artificial defect with a depth of 0.1 mm processed on the surface of the steel pipe was 10 dB or more. Furthermore, when detecting an artificial defect with a depth of 0.2 mm processed on the surface of the steel pipe, the S / N ratio of the output signal was 10 dB when the adjustment method of the present invention was not applied, but when the adjustment method of the present invention was applied, the S / N ratio was 15 dB or more, showing a significant improvement in flaw detection performance.

[0042] Next, a modified example of the ultrasonic flaw detection apparatus of this embodiment will be described with reference to Figures 9 to 11. Figure 9 shows another example of an ultrasonic flaw detection apparatus 101. The difference between the ultrasonic flaw detection apparatus 1 shown in Figure 1 and the ultrasonic flaw detection apparatus 101 in Figure 9 is that the shape of the entry-side guide member 106 has been changed and the guide member 106 has been positioned adjacent to the probe block 2.

[0043] The entry-side guide member 106 shown in Figure 9 has a ring-shaped main body portion 106b having a guide hole 106a, and a protruding portion 106c that extends from the main body portion 106b. The guide hole 106a is also in communication with the protruding portion 106c. The protruding portion 106c is directed toward the probe block 2. The protruding portion 106c is positioned near the entry-side through hole 21 of the probe block 2, thereby positioning the guide member 106 adjacent to the probe block 2.

[0044] Furthermore, the exit-side guide member 107 shown in Figure 9 also has a ring-shaped main body portion 107b having a guide hole 107a, and a protruding portion 107c that protrudes from the main body portion 107b. The guide hole 107a is also in communication with the protruding portion 107c. The protruding portion 107c is directed toward the probe block 2. The exit-side guide member 107 is located slightly further from the probe block 2 than the inlet-side guide member 106, but it may be positioned adjacent to the probe block 2, similar to the inlet-side guide member 106.

[0045] By positioning the entry-side guide member 106 adjacent to the through-hole 21 of the probe block 2, the amount of deflection at the tip of the steel pipe 10 due to its own weight as it passes through the through-hole 21 is reduced, allowing the steel pipe 10 to pass stably through the probe block 2. This improves the signal intensity of internal defects and further enhances the signal-to-noise ratio. Furthermore, by providing a protrusion 106c on the guide member 106, the tip of the steel pipe 10 just before insertion into the probe block 2 can be shielded by the protrusion 106c. This prevents water droplets discharged from the through hole 21 from entering the hollow part of the steel pipe 10, thereby reducing noise and improving the signal-to-noise ratio.

[0046] Figure 10 shows yet another example of an ultrasonic flaw detection apparatus 201. Figure 11 shows the probe block 202 provided in the ultrasonic flaw detection apparatus 201 of Figure 10. The difference between the ultrasonic flaw detection apparatus 1, 101 shown in Figure 1 or Figure 9 and the ultrasonic flaw detection apparatus 201 of Figure 10 is that the probe block 202 is equipped with a flow straightening wall 41 and a porous material 42.

[0047] As shown in Figures 10 and 11, a ring-shaped flow straightening wall 41 is provided on the inlet side of the steel pipe 10 of the probe block 202 to guide the water discharged from the through hole 21. The flow straightening wall 41 protrudes from the outer edge of the inlet side surface 202b of the probe block 202 so as to surround the through hole 21. The flow straightening wall 41 protrudes from the inlet side surface 202b of the probe block 202 toward the inlet side conveying roll 4. As a result, the through hole 21 is surrounded by the flow straightening wall 41. Furthermore, a porous material 42 is laminated on the inner surface of the flow straightening wall 41. As an example of the porous material 42, a resin material can be used, and more specifically, a foamed resin can be used. Also, the porous material 42 is not limited to resin and may be made of metal.

[0048] In the ultrasonic flaw detection device 201 shown in Figure 10, a flow straightening wall 41 is provided on the inlet side of the probe block 202 to guide the water discharged from the through hole 21, surrounding the opening on the inlet side of the through hole 21. As shown by arrow C in Figure 11, the water discharged from the through hole 21 is collected along the flow straightening wall 41 and flows downward from the lowest point of the flow straightening wall 41. This reduces the risk of water entering the hollow portion of subsequent steel pipes 10 when multiple steel pipes 10 are continuously supplied to the ultrasonic flaw detection device 201, thereby reducing noise in the steel pipes 10 and further improving the signal-to-noise ratio.

[0049] Furthermore, by laminating porous material 42 on the surface of the rectifier wall 41, water discharged from the through-hole 21 is collected along the rectifier wall 41 and held in the porous material 42, significantly reducing the risk of water entering the hollow portion of the subsequent steel pipe 10, thereby reducing noise in the steel pipe 10 and further improving the signal-to-noise ratio. [Explanation of Symbols]

[0050] 1, 101, 201... Ultrasonic flaw detection device, 2, 202... Probe block, 3... Ultrasonic flaw detector, 6, 106, 107... Guide member, 7... Adjustment unit, 10... Steel pipe, 10a... Thick wall portion of steel pipe, 10b... Inner surface of steel pipe, 10c... Outer surface of steel pipe, 21... Through hole, 21a... Inner surface of through hole, 31... Test piece, 31a... Simulated defect portion, 32... Hollow cylindrical steel material, 41... Rectifying wall, 42... Porous material, F... Focal point of the ultrasound.

Claims

1. A probe block having a through hole for passing a steel pipe, A plurality of ultrasonic flaw detectors are disposed on the inner surface of the through-hole of the probe block and capable of emitting ultrasonic waves toward the outer surface of the steel pipe as it passes through the through-hole, The probe block is equipped with an adjustment unit that is built into it to adjust the orientation of the ultrasonic flaw detector, The adjustment unit allows the direction of irradiation of the ultrasonic waves onto the steel pipe to be changed along a direction perpendicular to the direction of passage of the steel pipe. A water supply unit is further provided to supply water to the gap between the inner surface of the through hole and the steel pipe. An ultrasonic flaw detection device, wherein a flow-straightening wall is provided on the inlet side of the steel pipe in the direction of passage of the probe block to guide water discharged from the through hole, and the inlet opening of the through hole is surrounded by the flow-straightening wall.

2. The ultrasonic flaw detection apparatus according to claim 1, wherein the ultrasonic flaw detector is arranged on the probe block such that the focal position of the ultrasonic waves emitted from the ultrasonic flaw detector is located on the inner circumferential surface of the steel pipe.

3. A probe block having a through hole for passing a steel pipe, A plurality of ultrasonic flaw detectors are disposed on the inner surface of the through-hole of the probe block and capable of emitting ultrasonic waves toward the outer surface of the steel pipe as it passes through the through-hole, The probe block is equipped with an adjustment unit that is built into it to adjust the orientation of the ultrasonic flaw detector, The adjustment unit allows the direction of irradiation of the ultrasonic waves onto the steel pipe to be changed along a direction perpendicular to the direction of passage of the steel pipe. The ultrasonic flaw detector is positioned on the probe block such that the focal point of the ultrasonic waves emitted from the ultrasonic flaw detector is located on the inner circumferential surface of the steel pipe. A water supply unit is further provided to supply water to the gap between the inner surface of the through hole and the steel pipe. An ultrasonic flaw detection device, wherein a flow-straightening wall is provided on the inlet side of the steel pipe in the direction of passage of the probe block to guide water discharged from the through hole, and the inlet opening of the through hole is surrounded by the flow-straightening wall.

4. Guide members are provided on the entry and exit sides of the probe block in the direction of passage of the steel pipe, for fixing the position of the steel pipe within the through hole. The ultrasonic flaw detection apparatus according to any one of claims 1 to 3, wherein at least the guide member on the entry side is positioned adjacent to the through hole of the probe block.

5. The ultrasonic flaw detection apparatus according to any one of claims 1 to 4, wherein a porous material is laminated on the surface of the rectifying wall.

Images