| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of a high-strength electric resistance welded steel pipe having a yield strength YS of 450 MPa or more and excellent in creep characteristics at a medium temperature region (300-400°C) of an electric resistance welded part, which are suitable as steam transport piping.SOLUTION: A manufacturing method of an electric resistance welded pipe is provided, in which a hot-rolled steel strip is continuously roll-formed into an open pipe having an approximately circular cross-section, thereafter, electric resistance welding is performed in which a vicinity of an abutting part of the open pipe is heated to the melting point or more and is brought into press-contact by a squeeze roll, and thereby forming an electric resistance welded pipe, and then at a manufacturing line, heat treatment is performed on the electric resistance welded pipe. In the method, after the heat treatment, the electric resistance welded part is processed through continuous flaw detection by using a phased array ultrasonic flaw detector having a sensitivity increased by 20 dB than a sensitivity where a reference echo with a penetration hole of φ1.6 mm is set to 80%, and the steel pipes having a detected echo height of 80% or less are used as products.SELECTED DRAWING: Figure 1 |
