To measure a fraction of structure of a steel plate by accurately detecting magnetic characteristics of the steel plate even under such an environment that a distance between a measuring probe and the steel plate is varied by vibrating the steel plate being conveyed.
A method of measuring a fraction of structure in a steel plate includes using a measuring probe 2 to apply an exciting magnetic field Ho to a steel plate W in a production line of the steel plate W, thereby measuring a fraction of structure of the steel plate W. The method includes a magnetic field application step of applying, to the steel plate W, an exciting magnetic field Ho within such a range as to approximately fix a ratio of a variation of a coercive force Hc with respect to variation of a ferrite fraction, a detection step of detecting the coercive force Hc through the measuring probe 2 after the magnetic field application step and detecting a lift-off amount of the measuring probe 2 from the steel plate W, a coercive force correction step of correcting the coercive force Hc detected in the detection step on the basis of the lift-off amount detected in the detection step, and a ferrite fraction calculation step of calculating the ferrite fraction of the steel plate W on the basis of the corrected coercive force Hcr corrected in the coercive force correction step.
WASA YASUHIRO
HATAKE HIDEO
SAITO KENJI
MITANI HIROYUKI
MIYAMURA TAKEO
安田 敏雄
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