JPS61201155A - Method for discriminating welding defects in automatic ultrasonic flaw detection - Google Patents

Abstract

PURPOSE:To discriminate the kinds and extent of the welding defects by executing ultrasonic flaw detection towards one and the same point from above, the oblique direction and the vertical direction to the longitudinal direction of a part to be inspected such as welding beads of large diameter pipes. CONSTITUTION:Probes 1A, 1B; 2A, 2B; and 3 are directed in the vertical direction, in the oblique direction and from above to the longitudinal direction L of the welding bead B to execute flaw detection of one point on the bead B. The longitudinal crack 4 is detected by the vertical probes 1A, 1B. The sperical defects 5 is detected by the vertical probes 1A, 1B and the oblique probes 2A, 2B. The widthwise crack 6 is detected by the probe 3 from above. Since the probes directed differently are used in combination for flaw detection, the kinds and the extent of the defects can be discriminated in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a weld defect determination method particularly effective for automatic ultrasonic flaw detection of weld beads of large diameter pipes.

<Prior art and its problems> In this type of weld bead, it is possible to avoid the occurrence of planar defects such as cracks or spherical defects due to slag insertion, which cause a decrease in strength, and the effect on the strength of the structure. The degree is different.

For example, even if small, planar defects such as cracks have a greater effect on joint strength than other large spherical defects. Therefore, to ensure the safety of welding parts.

It is important to use ultrasonic flaw detection to determine the presence or absence of defects as well as the type of defects.

In conventional manual ultrasonic flaw detection, skilled technicians can identify these defects with a high probability, but the echo intensity changes depending on the ultrasonic transmission distance, making it difficult for ordinary technicians to identify them. be.

Furthermore, when detecting various welding defects using automatic ultrasonic flaw detection, there are defects that can be detected and defects that cannot be detected depending on the direction of the ultrasonic waves.
No. 99065 has been proposed.

This ultrasonic flaw detection method is a two-probe method in which ultrasonic waves are emitted obliquely to the weld bead, and the echoes are received by two receivers.

Receiving child 岑i! It is designed to be able to detect even the most active dust, and the width of the receiver is wider than that of the transmitter to expand the detection area. , the ability to detect defects at bead edges is low, and the type of defects has not yet been automatically determined.

Furthermore, there is a frequency analysis method that performs defect discrimination using the phenomenon that the frequency distribution differs depending on the type of defect, but it takes a long processing time and is difficult to use in automatic flaw detection.

The present invention was proposed in view of the above circumstances, and its purpose is to provide a welding defect determination method in automatic ultrasonic flaw detection that can automatically determine welding defects in a short time with a relatively simple configuration. It's about doing.

Means for Solving Problems〉 The welding defect determination method according to the present invention is directed to the same location of the inspected section from the direction perpendicular to the longitudinal direction of the inspected section, from the diagonal direction, and from above the inspected section. Ultrasonic flaw detection is performed using ultrasonic flaw detection, and the type of welding defect is determined by utilizing the difference in detection ability in each direction depending on the type of welding defect.Furthermore, the size of the defect is also determined, and thereby it is possible to determine whether the defect is harmful or not. It is designed to determine the degree of

<Example> The present invention will be described below based on an illustrated embodiment.

As shown in FIG. 1, vertical probes IA and IB detect flaws from a direction perpendicular to longitudinal direction B in width direction W of weld bead B, and oblique probe 2A detects flaws from an oblique direction in width direction W. The upper probe 3, which detects flaws from diagonally above 2B and weld bead B, is attached to a holder (not shown) so that it can detect flaws at the same location on weld bead B, and flaws are detected from each direction simultaneously. Compare to determine the type of defect.

The welding defects of the weld bead B include a longitudinal crack 41, a spherical defect 51, and a width crack 6.

When confirmed by manual ultrasound, the longitudinal crack 4 has a stricter directionality than the spherical defect 5, as shown in FIG.

Therefore, as shown in the first table, the vertical probe IA,
The IB detects the longitudinal crack 4 and the spherical defect 5, the oblique probes 2A and 2B detect only the spherical defect 5, and the upper probe 3 only detects the width due to the limit of the directivity of the 1 spherical defect 5. A directional crack 6 will be detected.

Defect type and detection ability of each probe (○: Detected. ×: Not detected) Since the detection ability of each probe clearly differs depending on each defect, the type of welding defect can be determined. That is, the detection signals from each of the probes 1A to 3 are taken into the processing device 7,
Here, processing as shown in FIG. 3 may be performed. Further, in order to eliminate detection errors, a set value may be provided, and the size of the welding defect may also be determined to determine the extent to which it is harmful.

Next, in the oblique direction probes 2A and 2B, the inclination angle θ(
(See Figure 1) is important. That is, θ<20
In the case of .degree., there is a high possibility that the oblique probes 2A and 2B will detect a crack in the longitudinal direction, resulting in poor discrimination. Conversely, when θ>70°, the holder cannot be brought close to the bead due to its physical size, resulting in a large number of skips.

Defect detection ability decreases. Therefore, it is preferable to set the angle to 20° and θ<70°.

Furthermore, due to the cause of cracking in the 1-width direction (delayed cracking), cracking occurs diagonally in the wall thickness direction.

The upper probe 3 detects well. Furthermore, in order to cover the thickness direction, it is necessary to increase the number of sets.

The probe switching method is a time division method, etc.

The holder is moved using a cylinder method or the like.

In addition, although the single probe method for both transmitting and receiving has been described above, it is also possible to adopt a two-probe method, and the present invention can be applied not only to weld beads but also to other types of ultrasonic flaw detection. Needless to say, it is applicable.

<Effects of the Invention> As described above, according to the present invention, since defects are determined by comprehensive judgment by combining independent probes with different directions, the following effects are achieved.

(i) Defects can be automatically determined.

(11) The operation is the same as the conventional ultrasonic flaw detection method, and the flaw detection processing time does not increase and can be carried out in a short time.

(iii) Existing probes can be used and it is practical.

Economical.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing the outline of the invention. Figures 2 (A) and (B) are pie graphs showing the results of omnidirectional flaw detection for crack defects and spherical defects, Figure 3 is a schematic diagram showing the outline of the apparatus for the present invention, and Figure 4 is a diagram showing defect discrimination. This is a flowchart for B...welding bead, L...longitudinal direction, W...width direction, I
A, IB...Vertical probe, 2 people. 2B... Oblique probe, 3... Upward probe, 4... Longitudinal crack, 5... Spherical defect, 6... Width direction crack, 7...
processing equipment

Claims (1)

[Claims] (1) Perform ultrasonic flaw detection on the same part of the part to be inspected from perpendicular to the longitudinal direction of the part to be inspected, diagonally, and above the part to be inspected, and compare the detected amounts in each of the above directions. A method for determining welding defects in automatic ultrasonic flaw detection, characterized by determining the type of welding defects.