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Evaluation of the nature of internal defects, causes of defects and preventive measures ③

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Incomplete penetration



The reflectivity is high and the wave amplitude is also high. When the ultrasonic flaw detector probe is translated, the waveform is relatively stable, and roughly the same reflected wave amplitude can be obtained when detecting flaws on both sides of the weld. Such defects not only reduce the mechanical properties of welded joints, but also form stress concentration points in the gaps and ends of the incomplete penetration, which often cause cracks after loading, which is a dangerous defect.



The reasons for this are generally: the pure edge gap of the groove is too small, the welding current is too small or the speed of the strip is too fast, the angle of the groove is small, the angle of the strip is wrong, and the arc blows.



Preventive measures include: reasonable selection of groove type, assembly clearance and correct welding process.