| 摘要 |
PURPOSE:To determine the crystal particle size of a steel plate, by dividing a Barkhausen noise signal by the power function of a permeability signal on the basis of the difference in steel plate speed dependence between the signal due to the Barkhausen noise generated at the time of the magnetization of the stele plate and the signal caused by permeability. CONSTITUTION:An electromagnet 2 and a sensor 3 are arranged so as to hold a running steel plate 1 therebetween and an AC current is allowed to flow to the electromagnet 2. When the output of the sensor 3 is allowed to pass through a low-pass filter (LPF) 6, a signal S1 is caused by permeability. When said output is allowed to pass through a high-pass filter (HPF), a signal S2 is caused by Barkhausen noise. The signals S1, S2 are respectively operationally processed by an operator 11 through a voltmeter 8, an amplifier 9 and a counter 10 and transmitted flux quantity Bt is raised to m-th power to divide the Barkhausen noise BNV. By this method, the particle size number dependence possessed by both factors can be still more developed and, when an m-value is selected, the moving speed dependence of the steel plate becomes unchangeable and, even when the material quality of the steel plate is altered, the alteration of the m-value is made unnecessary. By this constitution, a crystal particle size can be continuously measured on-line in a steel plate manufacturing process in a non- destructive manner.
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