| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of reducing the influence of the surface layer section on the outer surface of steel pipes and rapidly and stably measuring the distribution of depths in carburization along the longitudinal direction of the steel pipes. SOLUTION: The method of measuring depth in carburization on the inner surface of steel pipes includes a first step for arranging an excitation coil 11 and a detection coil 12 so that a steel pipe P to be measured is surrounded; a second step for applying voltage at a specific frequency to the excitation coil 11; a third step for extracting harmonics at a specific frequency from a voltage waveform induced in the detection coil 12; and a fourth step for calculating depth in carburization, based on the correlation relationship between the extracted harmonics and the depth in carburization. Additionally, in the first step, the excitation coil 11 is divided into two portions along the longitudinal direction of the steel pipe P to be measured, the direction of a magnetic field through respective division coils 11a, 11b is made identical by the respective division coils 11a, 11b that are divided into two portions, and a detection coil 12 is arranged between the respective, divided coils 11a, 11b. COPYRIGHT: (C)2005,JPO&NCIPI
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