Evaluation Method for Low Temperature Toughness of Weld Seam of HFW Pipe Based on the Distribution of Scattered Type Penetrator

Abstract

We found the correlation between low temperature toughness of the weld seam and the echo level from a scattered-type penetrator consisting of micro oxides in high frequency welding pipes. Conventionally, the low temperature toughness is evaluated by Charpy impact test. The factors that affect the quality of the weld seam were investigated by using an ultrasonic C-scan with a focused probe and samples sliced from the weld seam. As a result, it was found a scattered-type penetrator consisting of micro oxides is a key factor affecting low temperature toughness. Absorbed energy obtained by Charpy impact test can be evaluated by the ultrasonic echo amplitude with the optimized focused beam size (about 1 mm2) to detect the scattered-type penetrators.