Ultrasonic signal analyses of spot welds in thin steel sheet

The quality of spot welds in galvanized sheet metal was evaluated by using ultrasonic water immersion focusing method. The A-scan signal, B- and C-scan image features of spot welds were analyzed. The feasibility of evaluating the quality of spot welds by using the B-scan image was provided. By using the method, not only the kiss bonding and the perfect joint could be evaluated qualitatively, but also the pressure mark depth of the upper-bottom surface and the spot weld diameter could be calculated quantitatively. The accuracy of testing result was verified by contrasting the metallographs of actual spot welds cross section.