JPS5933226B2 - Method and device for detecting diagonal cracks in seamless pipes using ultrasonic waves - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a seamless metal pipe (hereinafter referred to as a seamless pipe).
The present invention relates to an ultrasonic flaw detection method and device for detecting diagonal cracks that occur in.

When performing ultrasonic flaw detection on metal tubes, tube circumference angle flaw detection and tube axis angle flaw detection have conventionally been generally performed. In tube circumferential angle flaw detection, defects in the tube axis direction are detected, and in tube axis angle flaw detection, defects in the tube circumferential direction are detected. A welded pipe having a welded portion in the direction of the pipe axis can be detected for flaws without any problem by such a conventional method. However, most of the defects that exist in seamless pipes are cracks that are inclined to the pipe axis direction (hereinafter referred to as diagonal cracks), and these are rarely detected by conventional pipe circumferential angle flaw detection and pipe axis angle flaw detection. I can't do it. The present invention
The purpose is to reliably detect diagonal cracks in seamless pipes, and in conventional pipe circumferential angle flaw detection, the ultrasonic beam is tilted in a plane parallel to the pipe axis, including the direction of incidence, and hits the diagonal crack at right angles. It is characterized by making it incident like this. In conventional tube circumferential angle flaw detection, the probe 3 is decentered (shifted in parallel by a distance x from the center line of the tube cross section) as shown in Fig. 1, and the ultrasonic beam is made incident on the tube 1 at an incident angle i. Let me defect 2
The probe 3 receives the reflected beam from the

At this time, the incident beam is made perpendicular to the tube axis direction, that is, as shown by the broken line in FIG. 2, the incident beam is made incident from the probe at a position of 3A at α200. In this case, the beam reflected by the diagonal crack 2 as shown in FIG. 2 deviates from the direction of the probe, so that the diagonal crack cannot be detected. In the present invention, as shown in FIG. 1, the probe 3 is decentered to make the ultrasonic beam incident obliquely in the circumferential direction of the tube, and the probe is probed in a plane parallel to the tube axis including the direction of incidence, as shown by the solid line in FIG. The child is tilted at an angle α, and the beam hits the diagonal crack 2 at an angle close to a right angle.

Note that point P in FIGS. 1 and 2 indicates the point of incidence on the seamless tube. The inclination angle α of the probe is preferably 50 or more and 200 or less. Figure 3 shows the results of flaw detection by artificially creating various diagonal slit flaws in a seamless tube and varying the inclination angle α of the probe. Incident angle i=190,
Refraction angle θ = 450, frequency 4MH2, probe diameter 1
A probe equipped with a point-focusing acoustic lens having a diameter of 0 mm and a focal length of 20.9 nm was used. As is clear from FIG. 3, the probe inclination angle α for obtaining the maximum echo height from the slit scratch is approximately 1/2 of the inclination θs of the slit scratch. Here, θs is the angle formed between the slit scratch and the tube axis direction, as shown in FIG. Inclination angle of actually existing diagonal cracks (
θs) varies depending on the manufacturing method and manufacturing conditions of the seamless pipe, but in normal seamless pipes, it can be detected with good sensitivity by adjusting the inclination angle α of the probe between 5° and 2'. can do. Regarding other flaw detection conditions, it is better to reduce the diameter of the transducer of the probe, lower the frequency, and further narrow down the ultrasonic beam to a point using an acoustic lens.

A slit wound with a width of 0.5 fins, a length of 80 fins, and a depth of 1.011 is created on a flat plate, and an ultrasonic beam is incident at an incident angle of 1 = 19° and a refraction angle of θ = 45°, and the inclination of the slit scar is determined by θs. Slit damage when changing. The echo height was measured by
Here, the θs=0 scratch is the case where the ultrasonic beam is incident on the slit scratch at right angles. As shown in FIG. 4, the smaller the diameter of the transducer, or as shown in FIG. 5, the lower the frequency, the smaller the reduction in echo height due to the inclination of the slit flaws.
In other words, it becomes less susceptible to the influence of the inclination of the scratches. Further, as shown in FIG. 6, the shorter the focal length using the point-focusing acoustic lens, the less the effect of the inclination of the scratches. Next, the diagonal crack detection device of the present invention will be explained in detail with reference to the drawings.

7 to 10 are diagrams showing specific examples of the device of the present invention, in which FIG. 7 is a side view, FIG. 8 is a front view, FIG. 9 is a plan view, and FIG.
Figure 0 is an enlarged perspective view of the probe head. The seamless pipe 1 immersed in water 4 is conveyed in the length direction while being rotated by a rotating and conveying device (not shown). A probe holder 5 is provided above the seamless tube 1, and various mechanisms for adjusting the probe are attached to it. A guide roller 6 made of rubber is attached via an arm 7 to make the ultrasonic beam stably enter the seamless tube 1. The probe 3 is attached to a probe head 8, and the probe head 8 is attached via a support arm 9 to a holding plate 13 (FIG. 9). The holding plate 13 is the ninth
As shown in the figure, it is slidably attached to part 56 of the probe holder 5. In order to adjust the horizontal distance y between the probe 3 and the seamless tube 1, the shaft 11 is adjusted using a micrometer screw 10.
The worm 12 is rotated through the rack, and the retaining plate 13, which is engaged with the rack, is moved. In order to adjust the eccentricity x of the probe 3, the probe head 8 is moved up and down by the micrometer screw 14. In order to adjust the inclination angle α of the probe 3, a gear 15 is fixed to the support arm 9 of the probe head 8 with a fixing screw 16, and a worm 19 is rotated via a shaft 18 with a micrometer screw 17. Let me do it. At this time, the angle scale 20 provided on the holding plate is read and adjusted. In addition, although this drawing shows an example in which two probes 3 are arranged in the length direction of the seamless tube 1, in order to adjust the distance u of the probes shown in FIG. The probe head 8 and the support arm 9 are slid by the adjustment screw 21 shown. Examples of the present invention will be shown below.

A stainless steel seamless tube with an outer diameter of 25.411 mm and a wall thickness of 2.3 m1 was tested for flaws using the apparatus shown in FIGS. 7 to 10.
The flaw detection conditions are: horizontal distance between the probe and the seamless tube y = 291t1t, eccentricity x = 4.3cm, probe inclination angle α = 1001, frequency 4MHz, 1 transducer diameter D = 101
11 The vibrator material was barium titanate-based porcelain, and a point-focusing acoustic lens F=20 mm was used. As a result of flaw detection, the inclination with the pipe length direction was 5° to 3', depth 0.2U1 or more, length 21
One or more natural defects could be reliably detected with a good S/N ratio. The apparatus of the present invention shown in FIGS. 7 to 9 shows an example in which two probes are arranged symmetrically on the left and right sides of the seamless tube, but if the conveyance speed of the seamless tube is lowered, one probe can be placed on each side. You can.

Moreover, if three or more of each type are arranged, the conveyance speed can be further improved. Furthermore, if the diagonal crack is inclined on both sides with respect to the pipe axis direction, it is necessary to place probes on both sides of the seamless pipe, as in the examples shown in Figures 7 to 9.
Depending on the manufacturing method of seamless pipes, in the direction of the pipe axis,
There may be only diagonal cracks tilted to one side,
In such a case, the probe may only be placed on one side of the seamless tube. As described above, according to the method and apparatus of the present invention, it becomes possible to effectively detect diagonal cracks in seamless pipes, which were previously undetectable, and are effective in controlling the quality of products.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing oblique angle flaw detection on the pipe circumference, Fig. 2 is an explanatory diagram of the inclination angle α of the ultrasonic beam in the present invention, and Fig. 3 is a diagram showing the ability to detect diagonal cracks by the inclination angle α of the probe. Figures shown in Figure 4~
Fig. 6 is a diagram showing preferred flaw detection conditions, Fig. 7 is a side view showing an example of the device of the present invention, Fig. 8 is a front view, Fig. 9 is a plan view, and Fig. 10 is a diagram of the device of the present invention. FIG. 3 is a perspective view of a part of the probe head. 1...Tube, 2...Defect, 3...
・Probe, 4...Water, 5...Holder,
6...Guide roller 7...Arm, 8
...Head, 9...Support arm, 10
Micrometer screw, 11...shaft, 12...
... Worm, 13... Holding plate, 14...
... Micrometer screw, 15 ... Gear, 1
6...Fixing screw, 17...Micrometer screw, 18...Shaft, 19...Worm, 20...Angle scale.

Claims (1)

[Scope of Claims] 1. An ultrasonic test method in which an ultrasonic beam is incident at an angle of 5° or more and 20° or less in a plane parallel to the tube axis including the direction of incidence in circumferential angle ultrasonic flaw detection of a metal tube. Method for detecting diagonal cracks in seamless pipes using sound waves. 2. In circumferential angle ultrasonic flaw detection of metal tubes, a probe holder is provided at the top of the liquid tank in which the metal tube to be inspected is immersed, and the height of the probe, the probe and the object to be inspected are set on the holder. An apparatus for detecting diagonal cracks in seamless pipes using ultrasonic waves, characterized by being equipped with micrometer screws that adjust the distance to the metal pipe and the inclination angle of the ultrasonic beam.