Study in Ultrasonic Flaw Detection for Small-Diameter Steel Pipe with Thick Wall

Abstract

In this paper, the detective method, using ultrasonic immersion method with focusing probe, was presented. Based on analyzing and solving the reflection and refraction coefficients of ultrasonic waves at the interface between two different media, the transmission paths were chosen, which were based on selected thick steel pipe (t/D ≥ 0.3), this is so-called converted shear wave testing method of ultrasonic detection of flaws. Moreover, the theory of flaw detection of the pipes was studied. The sound pressure of echo of flaws detected by converted shear wave was deduced, as was verified by independently developed automatic ultrasonic flaw detection equipment for the pipe. Experimental results revealed that it was feasible to detect the flaw by converted shear wave testing method. Echo was clear, the SNR was perfect, and the sensitivity was 4.3dB higher than one detected by refracted transverse wave. Detected-flaw speed was improved resulting in the test time dramatically shortening, which was especially beneficial for overall-length and all-round detection.