SU1374293A1 - Method of demagnetizing a workpiece - Google Patents

Abstract

The invention relates to electrical engineering and can be used in the demagnetization of shipboard parts after magnetic flaw detection. The aim of the invention is to increase the reliability of demagnetization and the stability of the demagnetized state with respect to mechanical effects. the amplitudes of the steady state current, the magnitude of which is changed at each stage in accordance with the required values of the residual the magnetization, determined by, based on the amount of operational changes of the magnetic state of the part according to the formula I ,; / I ,, 1-2 p. I & I ,, 2, where I, and I; - respectively, the maximum and current measured values of the residual magnetization of the part for the i-th stage; L1 - the value of permissible operational changes in residual magnetization under the action of mechanical effects; n is the number of the i-th step. with (L

Description

00

SD CO

WITH

The invention relates to electrical engineering and can be used in the demagnetization of ferromagnetic parts of marine engineering after magnetic flaw detection.

The aim of the invention is to increase the reliability of the demagnetization and the stability of the demagnetized state in relation to mechanical effects.

The quality of the demagnetized state depends on the degree of compensation of the residual magnetization vector of the phases, which can be achieved with the least labor intensity with a uniform decrease in the magnetization at each step. This is in the formula

2 п; Уа1гг. / 1

R | n

1 jxm

2V7i77 / i

 fm

50-30% amplitude of the steady-state current steps.

For a part of a cylindrical shape (with a length to diameter ratio of 50) made of a material with a coercive force of 0.6 kA / m, it is specified that operational changes of its magnetic state (residual magnetization due to mechanical stresses (b) after demagnetization should not exceed 0.0025 1 (0.25% with respect to maximum magnetization 1). The calculation by the formula shows that this requirement is met with the number of steps 10 and the following relative values of magnetization (starting with the maximum): yyyy-1; 0.89 ;

- - rm

0.78; 0.67; 0.44; 0.33; 0.22; 0.11; 0.

de i

h Yu

D1

ri

P

that can

- respectively, the maximum and current for the i-th step the value of the residual Hia-magnetization of the part;

-the value of the allowable operational changes in the residual magnetization under the action of mechanical effects;

-number of the i-th stage, presented as

 Us.

- P;

Rm

where Pr is the total number of steps.

The level of instability of the demagnetized state substantially depends on the magnitude of the magnetization of the phases and, consequently, on the number of steps. Consider the relative changes in residual magnetization under the action of mechanical stresses using the Neel diagram; obtained next1 rzGT-

blowing dependency:

 ji ir.

gy

The proposed method of demagnetization of parts is based on the creation in it

stepwise decreasing alternating-ss m, turn on the current in the coil, across its low frequency field. The alternating field is obtained by switching the polarity of the voltage supplying the razmazhnik11 coil, with a decrease in the face corresponding to the maximum magnetic field strength, reduce its value, measure the residual magnetization of the part

The part is affected by a field with a maximum amplitude, the value of the maximum residual magnetization is measured with the current turned off, and this value is memorized. Then the amplitude of the demagnetizing current is reduced by 50-30% and the polarity is switched. The step current is increased, the residual magnetization is measured, and, comparing its value with the calculated value, it is set to 0.89 of the maximum 1g. After that, the magnitude of the current amplitude is reduced by 50-30%, the polarity is switched, and then the values are sequentially set. After exposure to the last pulse (at I f. O), the stability of the demagnetized state is checked by subjecting the part to mechanical loads.

Formula and

3 o

rete n i

45

50

The method of demagnetization of the part, based on the creation in it of a stepwise decreasing alternating low frequency field with a change in the polarity of the voltage supplying the coil, and a current value that is different in order to increase the demagnetization reliability and stability of the demagnetized state relative to the mechanical affecting the magnitude of the magnetic field corresponding to the maximum intensity, reduce its value, measure the residual magnetization of the part when the current is off, and remember this value, then changed by the polarity of the voltage of the supply spool, incrementally increase the amplitude of the current measured remanence with the off current, and comparing these values with those calculated by the formula

Iri

2 n

1g & J- Gt

 rm

where 1 and 1 are respectively maxi-15 steps, determined by the formula

Maximum and current measured values for the i-th stage

kb

fine magnetization of the part; the magnitude of the allowable operational changes in residual magnetization under the action of mechanical effects; P; - the number of the i-th stage, and when the measured and calculated values are equal, the current is reduced, the polarity of the voltage is switched, and the operations are repeated.

P. g

Claims (1)

Claim A method for demagnetizing a part based on creating a stepwise decreasing alternating low-frequency field with a change in the polarity of the voltage supplying the coil and the magnitude of the current, characterized in that, in order to increase the reliability of demagnetization and the stability of the demagnetized state with respect to mechanical stresses, include the current in the coil, the value corresponding to the maximum magnetic field strength, reduce its value, measure the residual magnetization of the part with the current turned off and 1374293 ominayut this value, then changing the voltage polarity of the supply spool, incrementally increasing the current amplitude, measured remanence magnetization tatochnoy items; 4I _έ is the value of permissible operational changes in the residual with the current turned off and ¹ compares these values with those calculated by the formula G-1 where I and R gp - respectively, the maximum and current values measured for the ith magnetization under the action of mechanical influences; P; - the number of the i-th stage, and if the measured and calculated values are equal, they reduce the current, switch the voltage polarity and repeat the operations. Within the number of stages determined by the formula of the stage, the values of