Method for ultrasonically detecting position of assembled and welded structure

The invention relates to the technical field of welding positioning, and discloses a method for ultrasonically detecting the position of an assembled and welded structure, which comprises the following steps: when the thickness detected by an ultrasonic normal probe is suddenly and greatly increased, judging that the central position of the ultrasonic normal probe corresponds to the position of one side of the assembled and welded structure; when the plane plate and the assembled and welded structure are in non-penetration connection and the thickness detected by the ultrasonic normal probe is suddenly and greatly increased again, judging that the central position of the ultrasonic normal probe corresponds to the position of one side of the assembled and welded structure; when the plane plate is in full penetration welding connection with the assembled and welded structure and the thickness detected by the ultrasonic normal probe is suddenly and greatly reduced, judging that the central position of the ultras