Identification and determination of defect types in ultrasonic flaw detection

During ultrasonic flaw detection, while finding defects may be relatively easy, accurately determining the type of defect is a major challenge. This requires not only an in-depth understanding of the production process, flaw detection techniques, and instrument operation, but also extensive practical flaw detection experience.
Conventional ultrasonic scanning results provide key information through defect echoes and two-dimensional images. From these results, we can roughly determine the shape of the defect, such as a point, line, bar, flake or volume shape. However, in order to more accurately determine the type of defect, a combination of low magnification inspections, metallographic inspections, and SEM inspections are also required.
In order to help you identify the type of defects more quickly, the following summarizes the waveform characteristics of various types of defects:
1. White point defects: defective wave is forest-like, the wave peak is clear and sharp, the location of the injury wave corresponds to the distribution of defects. When lowering the sensitivity of flaw detection, the injury wave decreases more slowly.

2. internal cracks: divided into transverse, center and longitudinal internal cracks. Among them, transverse internal cracks in the straight probe probing, the sound velocity parallel to the crack when neither the bottom wave nor the injury wave; and longitudinal internal cracks in the straight probe circumferential probing, the sound beam parallel to the crack when the same neither the bottom wave nor the injury wave.
3. Shrinkage hole and shrinkage hole residue: the reflection of the injury wave is strong and the wave bottom is wide, which has serious influence on the bottom wave and often makes the bottom wave disappear. Wound wave of shrinkage residue appears in the center of the workpiece and has continuity.
4. inclusions: divided into a single and decentralized inclusions. A single inclusions for a single pulse, and decentralized inclusions for more than one injury wave, sometimes presenting Lin-shaped wave.
5. Loose material: at low sensitivity, the waveform may be very low or no waveform, and when the sensitivity is increased, a typical loose material waveform is observed. Loose in the casting on the sound wave absorption and scattering effect, often make the bottom wave significantly reduced. 6.
6. Sequencing: It is divided into ingot-type segregation and point segregation. Ingot-type segregation in the usual flaw detection sensitivity without injury wave, increase the sensitivity of the ring distribution of the injury wave.
7. coarse grain: its waveform is typical grass wave injury wave clusters, injury wave fuzzy unclear, moving the probe when the injury wave jumping rapidly.