METHOD FOR DEMAGNETIZING LARGE-SIZED FERROMAGNETIC PRODUCT Russian patent published in 2017 - IPC H01F13/00 

FIELD: electricity.

SUBSTANCE: method for demagnetizing a large-sized ferromagnetic product is based on the creation of a stepwisely decreasing alternating magnetic field of low frequency with a change in the voltage polarity feeding the coil and the current magnitude. The components of the geomagnetic field are compensated. The product is influenced by alternating magnetic field with the maximum value of tension. The value of the current in the coil for each pulse is reduced in accordance with the exponential law with a constant damping rate. At the end of the demagnetization cycle, the external residual induction of the product is monitored after the current is turned off for each subsequent pulse until the induction value reaches the required minimum value. With demagnetization, the number of pulses of the alternating magnetic field is not less than 80-120. A decrease in the value of field strength is carried out with a constant damping rate of about 1.03-1.05 for two adjacent pulses with the opposite direction of the field in absolute value. The control of the external residual induction of the product is carried out at the end of the demagnetization cycle, beginning with a field strength equal to 0.3% of the maximum value which exceeds the value of the coercive force of structural steel tenfold.

EFFECT: improving quality, reducing labour intensity and ensuring the stability of the demagnetized state of the product in relation to the operational mechanical loads.

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