JPS6264948A - Method for detailed flaw detection of welded part - Google Patents

Abstract

PURPOSE:To enable detailed inspection and the judgement of a flaw by certainly detecting only a harmful flaw, by arranging probes each having a narrow beam width in a mesh pattern so that the passing loci of the ultrasonic beams from the probes mutually have proper superposed flanges. CONSTITUTION:A preset area to be inspected, the positions of probes known in relative positional relation, a flaw position classified by a flaw kind, an echo height and a flaw length are preliminarily stored in the judge matrix of a signal processor 26' and, at first, an echo position 21 and and echo height 22 are obtained from a flaw detection signal 20 in a flaw detection apparatus 20'. The position 21 is corrected by the seam monitor signal 23 from a seam monitor apparatus 23'. A length measuring device 17' takes synchronous relation to the apparatus 20' and performs the measurement of a flaw length 18 and a position 19 in a longitudinal direction due to a flaw echo in a real time. The matrix 26 having taken in these signals compares the kind, size and acceptance of a flaw with preset information to evaluate the same and subsequently performs the delivery of a spray marker 24 to a material to be inspected and that of a signal to the automatic input to an on-line computer system 25.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to precise inspection in ultrasonic flaw detection of welded parts.
The present invention relates to a method for detecting welds that enables precise defect determination.

[Conventional technology]

Conventionally, when inspecting welds using ultrasonic flaw detection, a general-purpose probe with a wide ultrasonic beam width has been used to cover the necessary flaw detection range with the wide beam width.

Although FIGS. 6 and 7 are explanatory views of the conventional method, an explanation will be given below using a water gear-type automatic bevel deep wound apparatus as an example in which the method is applied from above the pipe.

FIG. 6 shows a situation in which flaws are being detected on the inner surface of a welded part of a material to be inspected. 1 is the test material, 2 is the welded part to be detected, 3 is the probe, 4 is the probe holder, and 5 is the trajectory of the ultrasonic beam.The blacked out area is used for position evaluation of defect echoes. Since only a unified flaw detection signal can be obtained from the beam path of the ultrasonic beam, the fact that it is wide as shown in the figure means that precise inspection and accurate defect determination are difficult. 6 is an electrical gate that determines the effective flaw detection range.

Figure 7 shows the conventional method of flaw detection using an ultrasonic deep flaw device.
In the figure when viewed on the T screen, 7 is the transmitted pulse and 8 is the detected and recognized defective echo.

9 is a noise echo that has been detected but is not recognized as a defect; 10 is an electrical gate that determines the effective range of flaw detection;
Reference numeral 11 is a reject level, and an echo having a height exceeding this reject level and entering inside the gate 10 is recognized as a defective echo.

Also, if we look at the patents and utility models that have been published in recent years,
The flaw detection method (Japanese Patent Laid-Open No. 56-67750) using bevel probes arranged in tandem with respect to the inspection part only has an apparent high sensitivity, and defect evaluation using signal processing equipment, etc.
1 [1tJst capability, the final evaluation cannot be performed, and re-detection using manual UST is required. Flaw detection equipment that uses the aperture synthesis method (Japanese Unexamined Patent Publication No. 156853/1982) not only cannot perform final evaluation because it does not have a defect evaluation function, but also has deep flaws due to repeated reflections and curvature of the material to be inspected. It is not effective in some cases. Even with a flaw detection device (Japanese Utility Model Application Publication No. 58-145556) which has a plurality of probes for flaw detection of the test material from multiple directions with different beam directions, final evaluation cannot be performed because it does not have a defect evaluation function.

[Problem that the invention seeks to solve]

Conventional ultrasonic flaw detection methods for welding defects have the following drawbacks. In other words, although it has the advantage of being able to inspect with a small number of probes, the wide beam makes it possible to detect multiple defects at the same time, making it impossible to distinguish between harmful large defects and harmless microscopic defects, as well as bead echoes, water echoes, etc. This method has the disadvantage that precise inspection and precise defect determination cannot be performed by detecting noise echoes (echoes other than the defect echo to be detected). Therefore, even if automatic flaw detection equipment is introduced to improve the efficiency of ultrasonic flaw detection of welded parts, there are significant overmarks, so manual UST is applied to erase the overmarks, and the defect marks after automatic flaw detection are re-examined. I was forced to go through the trouble twice: flaw detection, precise inspection, and precise defect determination. In a specific example,
The edge of the gate 1O in FIG. 7 fluctuates due to the physical behavior of the test material that occurs because it cannot be completely suppressed even with the addition of a copying function, causing the noise echo 9 near the gate edge to become a defective echo. This is a misunderstanding.

[Purpose of the invention]

The present invention improves the above-mentioned drawbacks, and allows for accurate inspection by identifying multiple defects even when they are adjacent to each other or when there are noise echoes. The purpose is to enable precise defect determination.

[Means for solving problems]

Conventionally, ultrasonic flaw detection has adopted a primary judgment method in which all suspicious items are punished, and the final judgment is made by X-ray transmission inspection, and those that cannot be determined by X-ray transmission inspection (those that pass) are judged. Although it requires a lot of time and effort, it was said that it could be done by using a precision manual UST. Therefore, ultrasonic flaw detection equipment generally has simple functions, such as reducing the number of probes by using probes with as wide an ultrasonic beam width as possible, and intentionally ignoring the spread of the ultrasonic beam when evaluating defect echoes. Since it is an evaluation function that monitors the beam path and echo height of only the main beam, it has become widely popular due to its simple configuration, such as requiring a simple signal processing system. These factors have been a major cause of delaying the technological progress necessary to achieve the elliptical detection (1! It is something.

The method of the present invention will be explained in detail below.

The flaw detection method may be water immersion method, water gap method, etc.
Also, the direction of flaw detection (upward or downward) does not matter. If there is one probe that satisfies the present invention, that probe may be used, but generally, a plurality of probes are required to satisfy the present invention. For convenience, the case where a plurality of probes are used will be described below. Probes with sufficiently narrow beam widths are arranged so that the passing trajectories of their ultrasonic beams have an appropriate amount of overlap with each other and become like a fine line. FIG. 1 and FIG. 2 are explanatory diagrams according to the present invention.

Figure 1 shows the trajectory of the ultrasonic beam as it travels like a net through multiple probes with narrow beam widths, where 12 is the material to be inspected, 13 is the probe, and 14 is the trajectory of the ultrasonic beam.
1 is a probe holder, 15 is a trajectory of the ultrasonic beam, and 16 is an electric gate that determines the effective flaw detection range.

Fig. 2 shows the signal flow in the evaluation function of the signal processing device, where 17 is a measurement signal of the defect length, 18 is the defect length, 19 is the longitudinal position, 20 is the flaw detection signal, and 21 is the defect length measurement signal. 22 is the echo height, 23 is the seam tracing signal, 24 is the spray marking of the part to be inspected, 25 is the automatic input signal to the online computer system,
26 is a determination matrix. Table 1 shows an example of the determination matrix in the present invention.

According to the present invention, it is possible to distinguish noise echoes, which were problematic in the conventional method, from real defective echoes. That is,
The narrower the ultrasonic beam width of the probe, the more precise inspection and more precise defect determination become possible. 2 to 3 dragons is optimal for this. When selecting a probe, check the effective beam width of the ultrasound beam, as well as the parallel length of the effective beam width (the length of the narrow beam section of the ultrasound beam continuing in parallel along the beam path). It is necessary to keep it.

The number of probes is determined based on the thickness of the material to be inspected, the flaw detection range, the degree of precision in detailed inspection and defect determination, and the selection results of the ultrasonic beam width of the probes.
As a guide, if the thickness of the plate to be inspected is 50 m and the entire welded area is to be detected, the appropriate number of probes is about 5 Qch. The probe holder 14 is appropriately selected according to the adopted flaw detection method.

The signal processing device is a device that uses a large number of flaw detection signals received from the probe to perform final inspection and defect determination precisely. A decision matrix method is optimal as an evaluation function to be provided in a signal processing device. In other words, when a certain defect is detected by all the placed probes,
defect position evaluation in each probe of that defect;
Defect echo height evaluation and defect length evaluation are performed on a determination matrix, and correspondence is established with an actual defect pattern stored in advance. In addition, when introducing only the method of the present invention for flaw detection, it is necessary to arrange the probes so that no dead zone of the ultrasonic beam occurs and prepare a corresponding number of probes, but it is necessary to prepare a corresponding number of probes. This does not apply to cases where it is desired to perform a localized precise inspection of a welded part or a precise defect determination.

Table 1 Next, regarding the defect determination matrix 26, major welding defects are shown in a cross section of a welded part in FIG.

In FIG. 9, 28 is a welded portion, and 29 to 38 are welded defects occurring in the welded portion and in the vicinity of the welded portion. 2 of these
9 is an inner bead crack, 30 is an outer bead crack, 31 is an outer right toe crack, 32 is an inner right tow crack, 33 is an inner left tow crack, 34 is an outer left tow crack, 35 is a right inclusion, 3
6 is a left-side inclusion, 37 is a blowhole, and 38 is a slag entrainment defect. Each of these defects has its own characteristics, and the position, direction, and shape where they occur are determined. By passing the beam from different positions with multiple probes, we can accurately capture the characteristics of each defect and identify it. Determine whether a defect is harmful or harmless.

FIG. 3 shows the defect determination flow in the method of the present invention. Table 1 is an example of a judgment matrix for ml inside the signal processing device, which shows the types of defects and their echoes.
In the table, the echo position is calculated and determined from the beam path of the defective echo, and the echo height unit is expressed in dB. First, in Fig. 3, determine whether the defect is A (cracks, undercuts) or something other than defect A (cracks, undercuts) using probe No. 1.
.

No., 2... is determined from the echo height and echo position, and if it is other than A, it is defect B (blowhole, slag inclusion) or defect C (not listed in Table 1). laminations, inclusions).

Furthermore, if the defect is B, it is determined whether it is a blowhole or a slag R, depending on whether it is spherical or elongated, and finally it is determined whether it is a harmful defect.

〔Effect of the invention〕

FIGS. 4 and 5 quantitatively show the effects of the present invention. In these figures, A is for the conventional method;
The graph shown above is for the method of the present invention, but with conventional automatic ultrasonic flaw detection equipment, the average number of defect marks is 20% and the average defect overmark rate is 85%, but by introducing the method of the present invention. As a result, they can be drastically reduced to an average of 3% and 5%, respectively, allowing precise inspection and accurate defect determination.

However, the overmark rate is It is.

Figure 8 shows the flaw detection status of the ultrasonic flaw detection device according to the present invention.
It is a diagram when viewed through the defect evaluation function by the signal processing device on the R7 screen. 7 is a transmitted pulse, 8 is an echo that has been detected and recognized, and since it is passed through a defect evaluation function, only defective echoes are displayed. 10 is an electrical gate that determines the effective range of flaw detection, and 11 is a reject level.

As explained above, according to the present invention, only harmful defects can be reliably detected. Note that the present invention is not limited to angle flaw detection, and can also be applied to the welding field, not only for completely seepage welds, but also for narrowing the beam width of the ultrasonic beam and increasing the number of probes. By increasing the degree of precision of inspection and judgment, it can also be applied to incompletely welded parts.

[Brief explanation of drawings]

Fig. 1 is a diagram of the state of flaw detection by introducing the present invention in water gear type deep flaws, Fig. 2 is a block diagram of a signal processing device equipped with an evaluation function according to the present invention, and Fig. 3 is a weld defect detection state by the method of the present invention. Fig. 4 is a graph of the change in defective mark number rate between the conventional method and the present invention, Fig. 5 is a graph of change in the defective overmark rate between the conventional method and the present invention.
Figure 6 is a water gap type flaw detection status diagram using the conventional method.
The figure is an explanatory diagram of a CRT screen showing the flaw detection status in the conventional method, and Figure 8 is an explanatory diagram of the CRT screen showing the flaw detection status in the method of the present invention.
FIG. 9 is an explanatory diagram showing welding defects within the bead cross section. DESCRIPTION OF SYMBOLS 1... Test material, 2... Welded part, 3... Probe, 4... Probe holder, 5... Trajectory of ultrasonic beam, 6... Electricity that determines the effective range of flaw detection Target gate, 7... Transmission pulse, 8... Defect echo, 9... Noise echo, 10... Electrical gate that determines the effective flaw detection range, 11... Reject level, 12... Target Inspection material, 13... probed material,
14... Probe holder, 15... Passage locus of ultrasonic beam, 16... Electrical gate that determines the effective flaw detection range, 17... Length measurement signal of defect length,
18... Defect length, 19... Longitudinal position,
20...Flaw detection signal, 21...Echo position 122...
Echo height, 23... Seam tracing signal, 24...
Spray marking on the material to be inspected, 25... Automatic impingement/nodding to the online computer system,
26... Judgment matrix, 29-38... Welding defect. Applicant Nippon Steel Corporation Patent Attorney Minoru Aoyagi Figure 1 Figure 2 Same period → Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Procedural amendment (voluntary) L case Indication of 1985 Patent Application No. 204971, Name of the invention Precision flaw detection method for welded parts 1 Relationship to the case of the person making the amendment Patent applicant address 2-6-3 Otemachi, Chiyoda-ku, Tokyo Name (
665) Nippon Steel Corporation Representative Takeshi 1) Yutaka 4, Agent 101 Address No. 4-5 Iwamoto-cho 3-chome, Chiyoda-ku, Tokyo - Higashi Building Name (7017) Patent attorney Aoyagi
; Minoru・-421°8, Contents of the Amendment The phrase "Figure 2..." on page 7, lines 5-12 of Illustrated III is corrected as follows. [FIG. 2 is a block diagram illustrating the signal flow in the evaluation function of the signal processing device, and the signal flow can be roughly classified into four types of equipment configurations. The determination matrix 26 as the signal processing device 26' includes each probe position whose relative positional relationship is known with respect to the inspection target site that has been briskened in advance, the defect position for each type of defect Iv1, the echo height,
and defect length are memorized in advance, and first, an echo position 21 and an echo height 22 are obtained as a flaw detection signal 20 from the flaw detection device 20'. The echo position 21 is corrected by a seam monitoring signal 23 from a seam monitoring device 23'. Length measurement bag r! t1? ' is an electrical flaw detection device 20
', and measures the longitudinal defect length 18 and position 19 using defect echoes in real time during flaw detection. The determination matrix 26 that continuously captures all of the above signals compares and evaluates the type, size, and pass/fail of the defect with preset defect information, and then displays the spray marker on the test material 24, and (2) Insert the following sentence after "Disconnect." on page 12, line 8. "In the figure, LP has insufficient penetration, Si has slag rolled in, and BH
is an abbreviation for blowhole. (3) Figures 2 and 3 of the drawings are corrected as shown in the attached sheet.

Claims (1)

[Claims] In ultrasonic flaw detection of welded parts of steel materials, in order to know the mutual incident positions of the ultrasonic beams with respect to the flaw detection part of the test material,
In addition, flaw detection is performed by injecting multiple ultrasonic beams with narrow beam widths so that a passing locus is created like a mesh with an appropriate amount of overlap between each other, and the number of obtained ultrasonic beams is equivalent to the number of incident ultrasonic beams. The flaw detection signal obtained by detecting flaws that occur or may occur in the weld is input into a signal processing device that is equipped with a defect evaluation function and stores in advance the defect information obtained by detecting flaws that occur or are likely to occur in the weld. A precision flaw detection method for a welded part characterized by distinguishing echoes from echoes other than the defective echoes.