JPS6057250A - Discriminating method of welding defect - Google Patents

Abstract

PURPOSE:To detect easily and exactly a welding defect by converting a welding defect of a corner part of T-joint, etc. provided with a backing strip, executing an inspection by using a surface wave-probe method altering to an angle beam- probe method. CONSTITUTION:A probe 1 to be used is a wide band surface wave probe whose frequency is 2MHz, placed on the lower face of a beam 2, and an ultrasonic pulse is transmitted toward a welding part 5. As a result, a surface wave M generated from the probe 1 is propagated along the surface under the beam, passes through a gap to a backing strip 4, and reflected from a corner part 6 of a defect first. Also, the surface wave M propagated toward a welding part 5 from the corner part 6 is reflected from a defect tip part 7. They are displayed as a reflected wave F1 from the corner part 6 and a reflected wave F2 from the defect tip part 7, respectively, in a receiving waveform figure shown on an oscilloscope. Accordingly, it will do that an existence of the reflected wave F1 from the corner part 6 of the defect is discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for determining welding defects using ultrasonic flaw detection.

Traditionally, the pulse reflection method, which is one of the ultrasonic flaw detection methods, uses pulse transmission and The oblique-angle probe method (refraction angle 7θ0), which belongs to the one-probe method and also belongs to the oblique angle method, is widely used as being optimal. This angle-angle probe method applies ultrasonic pulses with a refraction angle of 700 degrees from the probe to the inside of the member or the welding inspection area, and displays the reflected waves from there as a received waveform diagram on the oscilloscope. υ, ultrasonic traveling distance 1! ! [! (beam path length) and reflected wave strength (echo height), and uses trigonometric functions to calculate the position of the reflection source. This means that an estimated position can be obtained.

However, in this method, since the estimated position of the reflection source is used as the defect discrimination criterion, the defect discrimination accuracy is insufficient with the above-mentioned estimation accuracy. Although it is relatively easy to determine the length of a defect by scanning the probe, there are problems in that it requires skill to confirm the height of the defect in the thickness direction. Particularly in the case of a T-joint with a backing metal, which is the object of the present invention, it is difficult to distinguish between waves reflected from a corner and waves reflected from a flat surface, and there is a risk that a serious defect may be overlooked.

For example, as shown in FIG. 1, using the probe 11,
When welding the beam 12- and the column 13 with the backing metal 14 and inspecting the welded parts 15 shown as P part and Q part, respectively, there is no weld penetration like the P part shown in (A). There is a problem in that it is difficult to distinguish between a defective part and a normal welded part showing sagging like part (B) without K and with sag. That is, the probe 11
When inspecting the defective weld penetration part P and the sagging part Q using the oblique probe method, the received waveforms of both the P and Q parts are displayed as echoes at approximately the same location and at approximately the same height. Therefore, it is difficult to distinguish.

This invention was made in view of the above circumstances, and it can easily eliminate melt penetration defects that occur at the corners of T-joints with backing metals, etc.
It provides a flaw detection method that can be performed quickly and reliably, and is characterized by the adoption of a surface wave probe method instead of the conventional angle probe method. It is.

Embodiments of the present invention will be described below with reference to the drawings.

In Figure 2, the probe l used has a frequency of 2Mk
A broadband surface wave probe is suitable, and these are placed on the lower surface of the beam 2 in (2) and on the outside of the column 3 in (2), and ultrasonic pulses are emitted toward the welded part 5. In case (4), the surface wave M emitted by the probe 1 propagates along the lower surface of the beam 2, passes through the gap with the backing metal 4, and is first reflected by the corner 6 of the defect. . Further, the surface wave M propagated from the corner 6 toward the weld 5 is reflected from the defect tip 7.

These are respectively displayed as a reflected wave Fl from the corner 6 and a reflected wave F2 from the defect tip 7 in the received waveform diagram shown on the oscilloscope in FIG.

Therefore, the defect determination according to FIG. 3 (5) in the case of FIG. 2 (2) only requires identifying the presence or absence of the reflected wave F1 from the corner 6 of the defect. Since is approximately equal to the probe distance X, it is possible to omit the calculation of trigonometric functions required in the conventional method.

In addition, in the case of Fig. 2 (2), the surface wave emitted from the probe 1 is reflected from the defective tip 7 of the MFi welding part 5, so the received waveform shown in Fig. 3 (B) K As shown in the figure, the reflection source position is estimated from the beam path of the reflected wave F2, and by comparing this with the probe distance X, it is easy to determine whether the welding condition is poor penetration or sagging. Become Ruin.

In view of the above, according to the defect discrimination method using the surface wave method of the present invention, by simply obtaining the reflected wave of the inspection part as a received waveform diagram and comparing the beam path with the probe position, This makes it possible to easily determine whether the weld is a poorly penetrated part or a sagging part. Furthermore, in this defect discrimination method, at the same time as the defect discrimination described above, each beam path (Y, W) and the probe position (X
), it is possible to directly read the defect height. That is, in FIG. 2(A), the value of W-Y shown in FIG. 3(A), and in FIG. 2(B)K, the value of W-Y shown in FIG. 3(B)K. The value of X indicates the height of each defect. This defect height measurement is a feature not found in conventional methods.

The present invention is applicable not only to the flaw detection of welds at the corners of T-joints with backing metals as described above, but also to the flaw detection of weld defects at corners such as the sealing welds of box-shaped columns, for which no effective inspection method has been available so far. It can also be widely applied.

As explained above, the method for determining weld defects at corners of T-joints with backing metal, etc. of the present invention uses the surface wave-probe method instead of the bevel-probe method (refraction angle 7o0). By using it, we have made it possible to easily, quickly and reliably identify welding defects at corners, which was difficult in the past. This makes it extremely easy to measure the defect height in the thickness direction of the plate. This improves the reliability of ultrasonic flaw detection tests on the corners of T-joints with backing metals, and increases safety, especially in steel structures where this type of joint is often used. It is a matter of fact. It also has the effect of reducing welding repair work at construction sites, particularly for the joints where working postures are difficult.

[Brief explanation of drawings]

FIG. 7 is a schematic diagram showing a conventional flaw detection method, FIG. 2 is a schematic diagram showing an embodiment of the flaw detection method of the present invention, and FIG. 3 is a schematic diagram of a received waveform obtained from the flaw detection method of FIG. 1... Probe, 2... Curved, 3... Curved, Pillar, 4...
... Backing metal, 5 ... Welded part, 6 ... Curved corner, 7 ... Tip of defective part, X ... Probe distance, Fl ... ... corner reflected wave, F2... defect tip reflected wave, M... double surface wave. ,'', to agent patent attorney Tadashi Shiga Hon'ito ((A) (B) Figure 2 Figure 3

Claims (1)

[Claims] A method for determining welding defects, characterized in that a surface wave method among ultrasonic flaw detection methods is used to inspect a welded part of a corner of a T-joint with a backing metal, etc.