S. Yu. Mitropol’skaya

Correlation between the stress-strain state parameters and magnetic characteristics of carbon steels

A method for reconstruction of the stress-strain diagrams of steel objects from their magnetic characteristics determined directly during tension has been suggested. The coercive force, residual induction in the major hysteresis loops, and the maximum magnetic permeability are recommended as parameters for nondestructive testing of stresses and strains.

Evolution of magnetic properties of Fe-Mn and Fe-Mn-Cr steels with different stability of austenite during plastic deformation

A complex of magnetic parameters of two-phase (γ+ε) and austenitic Fe-Mn and Fe-Mn-Cr steels subjected to elastic deformation by uniaxial tension and torsion at room temperature has been studied. Regularities of changes in both the magnetic properties of the steels with different composition and the deformation stability of austenite depending on the accumulated degree of deformation have been revealed.

Variation of magnetic properties of two-layer carbon-steel products under tension

Evolution of magnetic properties during tension of multilayer products have been studied on two-layer specimens composed of low-carbon and medium-carbon steel plates with different values of magnetic hardness. The magnetic properties were measured in a loaded state. A model of the stress-strain state of a two-layer specimen has been designed. A technique for restoring stress-strain curves of multicomponent steel products from magnetic characteristics of its components determined directly during tension has been suggested. The values of the field of the maximum magnetic permeability of the components have been recommended as a parameter for nondestructive testing of stresses and strains, namely, at small deformations, the field of the maximum magnetic permeability of the magnetically soft component and at higher deformations, the field of the maximum magnetic permeability of the magnetically hard component. The results obtained are of considerable interest for technical diagnostics of loaded two-layer elements of constructions, including surface-hardened, welded, and bimetallic ones.

Influence of uniaxial tension on magnetic characteristics of the 12ΓБ pipe steel exposed to hydrogen sulfide

The results of measurements of the magnetic characteristics of specimens of the 12ΓБ pipe steel subjected to treatment with hydrogen sulfide for 96–384 h and also in the initial state, which were performed directly under the conditions of applied uniaxial tensile stresses to the point of specimen failure, are presented. The influence of hydrogen sulfide for 96 h has almost no effect on the mechanical and magnetic properties of the 12ΓБ steel, whereas a longer exposure leads to an appreciable decrease in the metal plasticity and an increase in its strength characteristics and the coercive force. The dependences of the magnetic characteristics on the degree of deformation are qualitatively similar to the stress-strain diagram except for the initial region of loading, where the effect of induced magnetoelastic anisotropy is displayed. At the stage of elastic strains, an unambiguous correlation between the coercive force measured on a minor hysteresis loop in weak fields and tensile stresses was discovered, thereby allowing the use of this parameter for evaluating the elastic stresses in articles from the 12ΓБ pipe steel, including in conditions of the influence of a hydrogen sulfide medium on this steel.

Effect of laser surface hardening on magnetic characteristics of a carbon steel under loading

Comparative studies of the structure and mechanical and magnetic characteristics of a Steel 45 subjected to laser treatment and the same steel subjected to hot rolling and volume hardening were performed. Staging changes in magnetic characteristics during tension were shown to reflect the order of involvement of individual structural components into the plastic deformation of the material.

Effect of elastoplastic deformation on magnetic characteristics of a powder structural steel having different residual porosities

The effect of porosity on the evolution of magnetic characteristics of a powder structural steel during deformation up to failure is shown by an example of steel 50H2M. The selection of a magnetic field such that the coercive force in a minor magnetic hysteresis loop weakly depends on the porosity is shown to be possible. It is supposed that the applied stress at which the minimum coercive force of such a minor hysteresis is observed corresponds to internal stresses of the porous material.

Model of the state of stress in a bilayer steel workpiece during uniaxial tension

A model for the state of stress in a planar bilayer workpiece under uniaxial tension conditions is proposed, and a method for the calculation of its stress-strain diagram from the experimentally obtained tensile curves of its components is developed. This method can be used to solve the inverse problem: using the stress-strain diagrams of one of the components and the entire workpiece, one can calculate the tensile curve of the second component. Since stress-strain diagrams can be obtained by nondestructive magnetic methods directly during loading, the results obtained are important for the diagnostics of loaded bilayer steel construction members.

Peculiarities of deformation behavior of magnetic parameters of a maraging steel characterized by different degrees of precipitation hardening

The deformation behavior of the magnetic characteristics of maraging steel 03X11H10M2T (ЭП678), which is subjected to hardening followed by aging at temperatures of 400–580°C, is studied. Nonmonotonic variations of the coercive force in the elastic region are shown to result from two factors: the positive magnetoelastic effect and the presence of second-phase particles whose geometric size increases substantially with increasing aging temperature. Two-parameter nomograms are constructed that allow the current states of loaded structural elements made of the steel under study to be estimated from their magnetic characteristics.

Certification of hardened surface layers by magnetic and electromagnetic methods

The possibilities of certification of hardened surface layers by measurement of coercive force, eddy current inspection and analysis of the field dependence of differential magnetic permeability μd(H) are considered. The advantages of analysis of the pattern of peaks on the μd(H) dependence for estimating the state of surface-hardened steels subjected to subsequent force loading are shown.

Influence of structural features of welded joints of low-alloy steels on magnetic and micromagnetic properties

Variations of magnetic (coercive force Hc, residual induction Br, maximum magnetic permeability μmax, maximum magnetic-permeability field Hμmax, saturation magnetization Jmax) and micromagnetic (number of pulses N and RMS Barkhausen-noise amplitude U) characteristics along the parent metal-welded joint direction were studied for welds of steels 10XCHД, 15XCHД, 09Γ2C, and X70.