WALL THICKNESS MEASURING METHOD AND STEEL PIPE MANUFACTURING METHOD USING THIS METHOD

PROBLEM TO BE SOLVED: To provide a wall thickness measuring method for measuring a wall thickness with high accuracy by reducing the effect of lift-off variation of a probe coil. SOLUTION: This wall thickness measuring method comprises a calibration step and a measurement step. In the calibration step, signals Vx and Vy are collected while an actual lift-off of a probe coil is suitably changed with respect to each of a plurality of specimens of different actual thicknesses (S1) to previously calculate a first approximate expression (S2) for expressing a relation between the lift-off and the signal Vy as a continuous function, a second approximate expression (S3) for expressing a relation between a yet-to-be corrected wall thickness and the signal Vx as a continuous function, and a third approximate expression (S6) expressed as a continuous function for calculating measured wall thickness values with the yet-to-be corrected wall thickness and the lift-off used as variables. In the measurement step, the thickness values of a measuring object are calculated by applying the first to third approximate expressions to the signals Vx and Vy collected on the measuring object. COPYRIGHT: (C)2005,JPO&NCIPI