E. Yu. Sazhina

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.

Measurements of Relative Magnetic Parameters of Materials in Tested Components Incorporated in Closed Circuits

The paper is dedicated to the feasibility of measurements of magnetic parameters of tested components incorporated in closed circuits with ferromagnetic transducers in the capacity of magnetic flux meters and the technique based on the conversion of the measured flux to a magnetic field intensity in an opening of a certain configuration made in the magnetic conductor of an applied electromagnet.

Choice of the parameters and algorithm for the magnetic hardness testing of thermally treated carbon steels by the method of regression modeling

The possibility of testing the hardness of quenched and tempered medium-carbon steels using their magnetic properties is studied. It is shown that the two-parameter method should be applied for the reliable estimation of the hardness. The coercive return magnetization (induction) and the coercive force must be used as the basic and subsidiary parameters of testing, respectively. It is established that the content of carbon in steel influences the sensitivity of testing. It is shown that the suggested magnetic hardness testing method can be practically implemented with the use of the modernized SIMTEST-2.10 system.

On the influence of plastic deformations of low-carbon ferromagnetic steels on the changes in the shapes of their hysteresis loops and the field dependences of the differential permeability

It is shown that inflections in the hysteresis loops of Ст3 low-carbon steel after its plastic deformation are determined by the appearance of a magnetic state of the easy-plane type in a part of the grains. The residual compressive stresses were found at which the maximum possible number of jumps of 90° domain boundaries (DBs) are observed. An expression for the energy of a domain with a 90° DB was obtained. It depends only on the field, the residual stresses, and the angle between the field and the chosen easy axis (EA) of a grain that is located in the easy plane (EP). This made it possible to find the conditions for the onset of irreversible jumps of the 90° DBs to the EP and back. As a result of the proposed theoretical model, the values of the fields of the differential permeability μd(H) peaks were determined, which are observed in positive and negative magnetic fields on the descending hysteresis-loop back. The ratios of the magnitudes of these peak were also found.

A magnetic method for determining the concentration of residual austenite in maraging steels

The results of measurements of magnetic properties of maraging steel 08Kh15N5D2T subjected to different types of thermal treatment, namely annealing, hardening, and aging, are presented. The required concentration of residual austenite during specimen preparation was obtained by varying the temperature of thermal treatment, the time of exposure, and the heating rate in the case of annealing. The new magnetic parameter N*, which linearly correlates with the concentration of residual austenite, is proposed. An algorithm for previously developed equipment and software, which is intended for the determination of this parameter, is offered.

Magnetic properties and hardness of maraging steel 08X15H5Д2T and nondestructive testing of retained austenite in parts

Dependences of the coercive force, saturation magnetization, residual induction, relaxation magnetization and magnetic susceptibility, maximum magnetic permeability and associated magnetic field, electrical resistivity, and hardness of maraging steel 08X15H5Д2T on the conditions of preliminary heat treatments, hardening, and subsequent aging have been studied. The content of rtained austenite in specially prepared specimens was determined. These specimens were subsequently used to calibrate a differential magnetic instrument. Such an instrument is also used to determine the content of retained austenite in aircraft bolts.

The Effect of Cold Plastic Deformation and Subsequent Annealing on the Magnetic Properties of Metals with Different Initial Structures

The effect of the degree of cold plastic deformation (CPD) and the temperature of subsequent annealing on the coercive force, relaxation magnetization, and relaxation magnetic susceptibility of iron and nickel is studied. The effect of the degree of CPD on steels with different initial structures in the annealed state (such as ferrite (M 10 steel), pearlite (шX15 steel), and ferrite-pearlite (50г steel) structure), as well as on 50гsteel with different initial structures obtained after quenching and tempering at different temperatures, is also studied. The dependences obtained are analyzed based on modern theories of magnetic hysteresis for magnetically soft materials. Recommendations for the use of nondestructive testing of the degree of CPD of articles (semifinished items) made from steels with different initial structures are given.

Magnetic and acoustic techniques for determining the phase composition and destruction dynamics of plastically deformed cobalt-free martensite-aging steel

The results of investigating the magnetic properties and phase composition (using the X-ray diffraction method) of specimens of cobalt-free ChS5VI (03N18M3TU) martensite-aging (maraging) steel that were subjected to a plastic tensile deformation are presented. It was established that all of the studied specimens can be divided into two groups depending on their heat treatment: specimens that were aged at T < 550°C, in which the saturation induction, the magnetic parameter N′, and the phase composition remain virtually constant under a tensile deformation up to their destruction and specimens that were aged at T > 550°C, in which the magnetic properties and the phase composition abruptly change at the initial deformation stages (up to 4–6%). The phase composition (the content of the residual austenite) in specimens of both groups, regardless of their degree of deformation, can be tested on the basis of the saturation induction and the N′ parameter, which correlates with the internal demagnetization factor. The acoustic-microscopy method showed that in specimens with the highest content of residual austenite, microflaws with minimum dimensions occurred during deformation, and cracks were not observed up to the specimen rupture. The location of the future neck nucleation at early deformation stages was predicted on the basis of acoustic images of subsurface layers for a specimen that was aged at T = 580°C.

The magnetic properties of grade BHC-2УШ maraging steel subjected to plastic deformation

The results of the measurements of the magnetic properties of plastically tensile-deformed samples of grade 08X15H5д2T maraging steel are represented. Preliminary the samples were subjected to annealing, quenching, and ageing with a variation in temperature and holding time for obtaining of the various initial contents of retained austenite. It was found that the testing of the content of retained austenite in the deformed state is possible by saturation induction Bs. The use of the structural-sensitive parameter N′ (an analogue of the internal demagnetization factors) allows one to determine the content of retained austenite in the undeformed state and in the prerupture state and the qualitative separation of plastically deformed and undeformed products of grade BHC-2УШ steel.

Improving Reliability of Magnetic Testing Data on Strength Properties of Hot-Rolled Pipes from 37G2S Steel

Two-parameter tests using the coercive force and residual magnetic induction yield more accurate estimates of strength parameters of metal products.