| 摘要 |
PURPOSE:To rapidly measure residual austenite with high accuracy by a small- sized apparatus, by providing an AC magnetic field generator, a detection coil and a signal processing circuit. CONSTITUTION:An AC magnetic field generator 1 is constituted of a field coil 101 and a sine-wave oscillator 102, and the output current of the oscillator 102 is applied to the coil 101 to generate an AC magnetic field. The specimen 3 inserted in a detection coil 201 is arranged in the coil 101 or in the vicinity of the end surface thereof and the AC magnetic field is applied to the specimen 3 to constitute a magnetic circuit. The AC signal voltage due to the AC magnetic field is induced at the terminal of the coil 201 but the amplitude value of the signal voltage corresponds to the AC magnetic characteristic of the specimen 3, that is, the residual austenite quantity thereof. The AC signal voltage is applied to a signal processor 4 which in turn converts the amplitude of the AC signal voltage to DC voltage. Therefore, the absolute value component of the AC signal voltage outputted from an output amplifier 405 represents the residual austenite quantity of the specimen. By this method, residual austenite can be rapidly measured with high accuracy by a small-sized apparatus.
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