Ultrasonic flaw detection technology for qualitative evaluation method

Currently the most widely used is the A-scan display type ultrasonic pulse reflection detector. After a long practice of ultrasonic testing, ultrasonic testing of many of its large number of personnel contact materials, products and manufacturing processes have a full understanding and verified through a lot of anatomical analysis, has accumulated rich experience in the detection through A-scan display type ultrasonic pulse echo flaw detector, according to the defect appears on the oscilloscope screen echo waveform shape, such as a video display or radio show, from the wave velocity, echo echo the forefront of the trailing edge of a steep decline in the extent and speed (down slope) , wave shape as well as echo Zhankuan flaw echo when moving the probe changes (amplitude, position, quantity, shape, dynamic envelope, etc.), but also the end of wave based on the observed multiple times, the end of wave height losses , defects are detected according to the location member, the distribution, the equivalent defect size (the reflectance of), extended, combined with the specific product, material characteristics and manufacturing processes make comprehensive judgment, evaluation of the type and nature of the defect . And sometimes also by changing the frequency of the ultrasonic pulse transmitted to change the beam diameter of the (take the focus of the probe or a different diameter, etc.) to observe the variation of defect echo, thereby identifying the material of the reflection metallurgical defects or organization.

In this regard there are a lot of lessons learned and information reports, for example, determine the white point of steel forgings, inclusions, residual shrinkage, coarse-grained, center porosity, box-shaped segregation and porosity in the weld, slag, incomplete penetration, lack of fusion, cracks and so on. Must be noted that this judgment ultrasonic testing method relies heavily on the experience, skill level and on specific products, materials and manufacturing processes to fully understand its limitations is great, difficult to promote a common evaluation method. Further, as the flaw echo A-scan display defect information displayed is extremely limited, mainly shows the volatility of size, position and shape of the echo envelope and the phase response of the ultrasonic defect, spectral and other important information will not be displayed , but the latter two with the nature and type of defect has a close relationship, which is currently the majority of ultrasonic testing personnel committed to research to explore the issue.