METHOD FOR JUDGING MOLTEN SOLID OF WELD PART WITH USING ULTRASONIC FLAW DETECTION APPARATUS

PROBLEM TO BE SOLVED: To judge whether or not a molten solid (nugget (n)) is formed at a welded part by a nondestructive inspection. SOLUTION: According to this judgment method, a joint member formed by welding two metallic members m1, m2 is used as a material M to be inspected, ultrasonic waves are emitted from a probe 10 and an attenuation state of the ultrasonic waves passing a weld part and reflected at a lower face M2 is observed, whereby it is judged whether a molten solid (nugget (n)) is formed or whether the material M is cold jointed. The molten solid generated by the welding increases a crystal particle size due to the re-solidification, and the ultrasonic waves propagating the part are attenuated larger than a cold joint without the molten solid. Whether it is the molten solid or cold joint can be surely judged by observing and evaluating a state of the attenuation.