METHOD FOR DETECTING SHAPE OF WELDED STEEL PIPE BUTT-SEAM, METHOD FOR WELDED STEEL PIPE QUALITY CONTROL USING SAID METHOD, AND DEVICE FOR SAME

摘要

The present invention provides a method for detecting a shape of a butt joint of a welded steel pipe, in which a step at the butt joint of the welded steel pipe can be detected with high accuracy without the need for a high-speed data processor or a complex mechanism. More specifically, a specific detection range including a butt joint 12 of a welded steel pipe 10 is scanned with a non-contact means 14 to obtain geometric coordinate data L of the specific detection range projected on a two-dimensional plane. Coordinates of a start point A and an end point D of the specific detection range, a first selected point B located between the start point A and the butt joint 12, and a second selected point C located between the butt joint 12 and the end point D are selected from the geometric coordinate data L. A first approximate circle α1 that includes the start point A, the end point D, and the first selected point B, and a second approximate circle α2 that includes the start point A, the end point D, and the second selected point C are calculated. A deviation between the first approximate circle α1 and the second approximate circle α2 is used as an index representing the shape of the butt joint 12.