Abstract: Ultrasonic C-scan of spot weld on galvanized sheet is carried out by using ultrasonic water immersion focusing method. The A-scan signals of the specific parts of the ultrasonic C-scan image are analyzed. C-scan can be adopted to measure the diameter of the spot weld and discover the inner flaws of the spot weld such as splash, crack, void and inclusion. Besides, C-scan can detect the appearance of the spot weld too. In order to acquire the more accurate information of the inner structure of the spot weld, the characteristic C-scan image and the characteristic A-scan signals which can be used to distinguish the shape and type of inner defects are also obtained. The ultrasonic C-scan image method not only can evaluate the quality of spot weld but also can be a kind of important auxiliary method for spot weld research.

Key words: Flaws, Spot weld, Ultrasonic C scan