A. N. Stashkov

Portable instruments for multiparameter magnetic evaluation of material structures

The principles of operation and capabilities of portable computerized testing facilities of the MMT and SIMTEST series, which are intended for multiparameter magnetic evaluation of the structure of ferromagnetic articles of different dimensions, are described.

Possibilities of magnetic inspection of plastic deformations preceding failures of low-carbon steels constructions

The possibility of magnetic inspection of plastic deformations preceding the failure of strained steel constructions was studied by locally magnetizing them with an attachable electromagnet. Field dependences of the differential magnetic permeability of a plate made of steel 09Γ2 on the applied and residual stresses were determined. Critical fields of 90° and 180° domain-wall motion at different degrees of deformation were calculated using a model taking into account the contribution of these domain walls to magnetization reversal processes. Dependences of the coercive force and residual magnetization of the plate on the applied and residual stresses, which were measured using a SIMTEST portable magnetic measuring system, are reported.

Multiparameter Methods for Structural Analysis of Steel Articles Using the Magnetic Properties of Substances

The potentialities of multiparameter testing for the determination of the physical and mechanical properties of steel articles based on measurements of the magnetic characteristics of the substance have been shown. The most likely testing parameters have been determined. Information about a small portable MMT-2 magnetic multitester, which allows rapid measurements of the relative magnitudes of the magnetic properties of a substance to be taken, is presented.

Multipurpose Use of Magnetic Properties of Steels in Nondestructive Testing of the Quality of Heat-Treated Workpieces

The paper is devoted to calculation of expressions relating the hardness both of a series of low-alloyed steels and of high-chromium steels 14Kh17N2A, 20Kh13, 30Kh13, and 40Kh13 with their magnetic properties after quenching and subsequent tempering over a wide temperature range. Expressions relating the hardness of 60S2A, 50G, and U8 steels with reading of a MS-2 magnetic structuroscope are also calculated. A table containing tempering temperature intervals on which the coercive force, the relaxation magnetization, and the magnetic susceptibility vary monotonically is given for a series of steel grades. Limits of variation of the above-mentioned quantities and the hardness are also given.

The effect of plastic strain and the orthogonal bias field on the processes of magnetization of low-carbon steel

The field dependences of the differential magnetic permeability on the magnetization curves of annealed and plastically strained specimens from low-carbon 20 steel were investigated. The measurements were performed with the simultaneous action of the magnetizing field and perpendicular bias fields of different magnitudes. The results were obtained for non-strained and pre-strained specimens. It was revealed that application of an orthogonal bias field allowed the separation of the contributions of different domain boundaries (the 180° and 90° boundaries) into the processes of magnetization and remagnetization. The critical fields of 90° transitions will be determined not only by the induced magnetic anisotropy that is due to strain, but also by the magnitude of the applied bias field.

Induced magnetic anisotropy in low-carbon steel plates subjected to plastic deformation by stretching

Experimental studies of induced magnetic anisotropy in plastically deformed low-carbon steel were carried out. The measurements were performed on samples in the form of discs. The maximum energy of the induced magnetic anisotropy was observed at a relative elongation of ~12% upon an increase in the plastic deformation of samples. At higher degrees of deformation the energy of the induced magnetic anisotropy is reduced, which indicates a decrease in the residual mechanical stresses in the material.

An experimental method for evaluating the critical fields of moving domain boundaries in plastically tension-deformed low-carbon wires

Changes in the magnetization projection on the axis of wire specimens of low-carbon CΤ1ΚΠ steel during their magnetization reversal by a circular field were experimentally determined as a function of the polarizing-field value in a solenoid. Measurements were performed on annealed and plastically tension-deformed specimens. It was shown that the proposed experimental technique allows evaluation of the critical fields of displacements of 90° domain boundaries. The parameter that is related to the induced magnetic-anisotropy field and allows evaluation of the level of residual stresses in the deformed metal is determined.

Functional Possibilities of SM-401 Magnetic Structuroscope

The possibilities of nondestructive testing the quality of product hardening using an SM-401 magnetic structuroscope with an H-shaped attached electromagnet are shown with references for ShKh15 and EI928 steels. Possibilities of the device for testing the quality of tempering products made from 40KhN2MA and wheel-tire steels are demonstrated.

Nondestructive Method for Testing Stress-Strain Properties of Oil Pipes

The results of study and statistical processing of the magnetic properties, namely, the coercive force and the relaxation magnetization, as well as the strength, plastic, and tensile properties of the 32G2S, 36G2S, and 38KhNM steels, used in fabricating oil pipes, as functions of the heating temperatures in quenching and tempering are given. Relations between the stress-strain and magnetic properties are estimated using the multiple correlation method. The introduction of the multiparameter nondestructive method for testing finished oil pipes at the Sinarsk Pipe Factory is described with reference to a plane-carbon steel of the D strength group and the 38KhNM low-alloyed steel of the E strength group.

Testing residual compression stresses caused by plastic deformation of steels by means of remanence

The possibilities for testing residual compression stresses caused by plastic deformation ɛ of low-carbon steels by means of residual magnetic induction and inductions in various magnetic states are considered. A new control parameter was determined that correlates well with the relative value of residual compression stresses in the range of 0% ≤ ɛ ≤ 10%.