Determination of Inclusions in Steel Sheet by Ultrasonic Probe in Detecting Near Surface Flaws

摘要

A new type of ultrasonic probe was developed to detect near surface flaws. The probe has a hollow center by which a leaky surface acoustic wave (LSAW) can be easily separated from longitudinal waves along the central axis. To verify applicability of the probe, a steel sheet was tested, and the inclusions it contained were detected without grinding the sheet surface. The results showed that this probe with lower frequency detected inclusions more clearly than the conventional method with high frequency. The inclusions were detected at a depth of 30 mu m below the sheet surface and had a width of 80 mu m.