In the report results of research of opportunity of application of a pulse magnetic method [1], as the least sensitive to the influence of these factors, for nondestructive testing of sheet steel are resulted.

Results of research of distribution of residual magnetization field over a surface of a sheet material are done at its pulse magnetization in non-uniform magnetic field at various modes of magnetization and various magnetic properties of the material to be magnetized.

It is shown that the value of normal component of intensity of residual magnetization field in a center of a magnetized section and in a section of a negative maximum is determined basically by the magnetic characteristics of a material of a sheet, the influence of the value of magnetizing field (in a range from 3.10⁵ up to 18.10⁵ A/m) thus is insignificant. At the same time the extent of a magnetized section in a greater degree depends on amplitude of pulses of magnetizing field, than on the magnetic characteristics of sheet (with increase of amplitude of pulses of magnetizing field and reduction of coercive force of a material the extent of magnetized section increases). For distribution of tangential component characteristically is availability of sharply expressed minimum near the center of a magnetized section and rather extended area of stability of its values.

Thus the extremums of normal and tangential components of field decrease on the exponential law with growth of distance from a surface of sheet. Simultaneously the distance from a center of magnetized section up to a point of transition of each of components of residual magnetization field increases on the law close to linear.

Influence of speed of moving of sheet during pulse magnetization on the space distribution of normal component of residual magnetization field intensity is considered. It is shown that with increase of speed of moving of sheet both the value of residual magnetization field and the form of magnetized section change. With increase of distance from a surface of a sheet on which the normal component (or its gradient in the direction of normal to the face) the influence of speed of sheet's moving on the field distribution (or gradient distribution) decreases.

The change of extent of a magnetized section with change of magnetic characteristics of a material of a sheet (at in comparison small influence of change of sheet's moving) assumes the opportunity of testing these properties along the magnetized section. However the sensitivity to controllable parameter at measurement of extent of magnetized section considerably less is than at measurement of gradient of residual magnetization field intensity in the center of the magnetized section.

These laws are taken as a basis for pulse magnetic method of testing of sheet steels in movement. The special features of this method with reference to the testing in movement are firstly separate in space and in time realization of processes of pulse magnetization and measurement of gradient of residual magnetization field intensity, secondly, realization of magnetization and measurement from both sides of moving sheet, thirdly realization of the test on the averaged values (arithmetic mean or geometric mean) of maximum values of gradient, measured from both sides of sheet.

On the basis of this method installations for pulse magnetic testing of type IMPOK-1, IMPOK-1A, IMPOK2 and IMPOK-3 are developed.

The technical decisions taken as a basis for developing of these means of testing and their functional potentials are considered.

REFERENCE

1. M. A. Melgui, The Magnetic Testing of Mechanical Properties of Steel, Minsk: Nauka I Technika, 1980 (in Russian)