Regularities of the change in the coercive force under biaxial asymmetric deformation of steel 3

The change in the coercive force under biaxial asymmetric (tension and compression in mutually perpendicular directions) cyclic deformation of cross-shaped steel 3 specimens in the elastic region of deformations was studied. Specimens were deformed beforehand under biaxial asymmetric loading to various degrees of plastic deformation. It was demonstrated that the elastic-deformation dependences of the coercive force measured along the tension and compression directions are qualitatively similar to those under uniaxial tension or compression. It was also shown that, under cyclic elastic loading, these dependences are reversible for well-annealed steel and have a hysteresis that expands with increasing degree of plastic deformation for plastically deformed steel. The possible causes of the hysteresis in the dependence of the coercive force on the elastic cyclic deformations under biaxial loading are discussed. It was supposed that the hysteresis of the coercive force was caused by the appearance of free (not bound in carbide phases) carbon atoms playing the role of interstitial impurity atoms for the α-iron lattice in plastically deformed carbon steels. The possibility of estimating the stressed-strained state of steel under biaxial loading using a magnetic method was discussed.     

Coercive force of ferromagnetic steels under the biaxial symmetrical tension of a material

Patterns of coercive force variations of Ct.3 and X70 ferromagnetic steels under biaxial symmetrical tension within both elastic and plastic ranges of deformation were studied using X-shaped specimens. It was shown that the coercive force of isotropic polycrystalline materials increased during plastic deformation under biaxial symmetrical tension and was proportional to applied stresses (loads). Plastic deformation of materials with high initial coercive-force anisotropy along the principal directions (X70 steel) leads to an abrupt decrease in anisotropy and subsequent alternation of its sign. The patterns of a material’s coercive force behavior allow the coercive force to be used for estimating the stress-strain state (from both an increase in the coercive force and its variations during loading as compared to that of the initial material) of articles made from the studied steels under biaxial symmetrical tensile deformation.     

Magnetic Properties of a Material Used to Estimate Elastic and Plastic Strains of Ferrite—Pearlite Steels

The effect of elastic and plastic strains on the magnetic properties of ferrite-pearlite steels has been studied. It has been shown that the sensitivity to elastic-tensile and bending strains is four to five times greater for remnant magnetization than for coercive force. In order to determine the degree of cold plastic deformation of high-carbon steels, a two-parametric testing technique based on the use of remnant magnetization and coercive force was suggested. An MMT-2 device was recommended for measurement of the required parameters.     

Application of magnetic and electromagnetic-acoustic methods for assessing plastic deformations under cyclic loading of annealed intermediate-carbon steel

The influence of cyclic loading of annealed steel 45 during low-cycle fatigue on changes in its magnetic characteristics, in particular, the coercive force and the residual magnetic induction, for the major and minor magnetic-hysteresis loops and on changes in the propagation velocity of a longitudinal acoustic wave is studied. The sensitivity of the considered physical characteristics to the value of plastic deformation stored under cyclic loading in the region of both large and small strains is determined. The residual mechanical properties displayed after cyclic loading are determined, and the steady-state correlations between the coercive force measured on minor hysteresis loops in weak fields (the Rayleigh region) and the remanent clongation are obtained. The possibility of monitoring the stored plastic deformation and assessing the residual life of a material during its cyclic loading from the values of its magnetic parameters is shown.     

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.     

Effect of Deviation from Coaxiality between the Directions of Magnetization and Mechanical Strain on the Results of Magnetic Testing of Elastic Strain in Steels

The magnetoelastic effect in steels that are in the states of coercive force and residual magnetization in the saturation hysteresis loop is studied. The regularities of changes in the residual magnetization and coercive force under uniaxial tensioning and compression of specimens of 30KhGSA steel magnetized along the direction of strain application are established. It is shown that a variation in the direction of magnetization and complication of the strain pattern result in considerable deviations in the character of changes in the magnetic forces determined by a ferroprobe-type coercive force meter for elastically strained plates from St3 and R6M5 steels and for an St3 beam.     

Coercive-force hysteresis of carbon steels during elastic cyclic tensile deformation

Dependences of the coercive force and mechanical stresses on cyclic tensile in the region of elastic deformation of steel samples with various carbon contents (Armco iron, 3, 8) are investigated. It is shown that the dependence of the coercive force on cyclic elastic tensile deformation is reversible for well-annealed samples. The dependence for plastically deformed steels has a hysteresis loop that is significantly determined by the carbon content and increases with an increasing degree of plastic deformation. It is assumed that the hysteresis of the coercive force as a function of elastic cyclic tensile deformations in plastically deformed carbon steels is caused generally by the appearance “free” carbon atoms, i.e., those not bound in carbide phases, which act as interstitial impurity atoms in the lattice of α-iron.     

Effect of elastic deformation by compression,tension, and torsion on the critical magnetic field distribution in a steel 15XH4Д

Effect of deformation by compression, tension, and torsion on magnetic characteristics and critical magnetic field distribution in a high-strength economically alloyed structural steel 15XH4Д. The coercive force, residual induction, and maximum magnetic permeability vary definitely with changing stresses. This fact gives the principal possibility to use these characteristics as parameters for magnetic testing of elastic strains. Moreover, the studies of critical magnetic field distribution allow us to obtain data on the volume of the ferromagnet, which has changed its state in a given magnetic field under certain mechanical stresses.     

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.     

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.     

On controlling stresses in a complexly loaded steel construction by magnetoelastic demagnetization

Dependences of magnetic leakage field strength during magnetoelastic demagnetization of local magnetization in a steel disk (St3 steel) on the value of its biaxial deformation in the elastic domain have been studied. Deformation-induced mechanical stresses that act in radial and tangential directions have been calculated. Dependences of changes in the normal component of the magnetic leakage field of steel on the effective stress value are given. It is shown that mechanical stresses in a complexly loaded construction can be tested by the value of its magnetoelastic demagnetization.     

Magnetoelastic Acoustic Emission in Ferromagnetic Materials. II. Effect of Elastic and Plastic Strains on Parameters of Magnetoelastic Acoustic Emission

The action of tensile and compressive stresses on iron, nickel, and steel crystals of different quality in the process of magnetization is considered. A clear relation between the parameters of magnetoelastic acoustic emission (MAE) on one side and, on the other, the processes of reshaping of 90°, 71°, and 109° magnetic domains, change in their volume fraction, and mobility of the domain walls is revealed. The dependence of the behavior of the magnetic properties of ferromagnets, namely, the coercive force, longitudinal and transverse magnetostriction, and induction, on the MAE parameters is also established. It is shown that under certain conditions of magnetization the MAE parameters can be used more successfully than the coercive force of ferromagnets for testing their stressed-strained state.     

Irreversible changes in the magnetization as indicators of stressed-strained state of ferromagnetic objects

The changes in the magnetic properties of low-carbon steels connected with reversible and irreversible magnetization reversal processes under the action of elastic stresses are studied. It is shown that, on the curve of return from the coercive force, the maximal irreversible increment in the magnetization corresponds to the zero values of applied stresses. The application of compressive stresses leads to a sharp decrease in the irreversible component of the magnetization increment. Tensile stresses influence slightly the proportion between reversible and irreversible processes. New possibilities for the multiparametric quasi-static evaluation of stressed-strained states of ferromagnetic objects are revealed.     

Accounting for the statistical weights of factors used when studying the liability of rolled products to brittle fracture

The interrelationships between structure, magnetic properties, and impact strength at different temperatures were studied in a 09Γ2 steel with an unchanged chemical composition after varying the heating conditions prior to rolling, as well as the final rolling temperature. These interrelations were also studied for a number of low-alloy steels of different grades (close to steel 09Γ2), which were produced in the workflow at the Nizhni Tagil Iron and Steel Works. It was shown that the coercive force and relaxation magnetization can be used to separate the effects of ferrite grain size and shape on steel properties. The constraint equations for the impact strength and magnetic properties were obtained in terms of a multiparametric model with allowance for the impact strength test temperatures. Idealized relationships between the impact strength and magnetic properties of Ст 3сп and 09Γ2 steels were obtained for the impact strength-coercive force coordinate plane with allowance for the impact strength test temperatures and statistical weight of the studied properties.     

Specific Features of the Behavior of the Coercive Force in Low-Carbon Plastically Deformed Steels

The relationship between the coercive force in low-carbon steels under plastic extension and compression and the values of deformation and actual and residual stresses are studied. This relationship is investigated for both “ slow” loading (when an equilibrium deformation is attained for each load value) and “fast” loading (when such equilibrium is not attained). It is shown that (i) a comparatively small increase in the coercive force in a loaded condition is due only to an increase in the density of dislocations in the process of plastic extension; (ii) a significant steep increase in the coercive force accompanying removal of the load from a plastically stretched specimen is fully due to residual compression stresses; (iii) the values of the coercive force under “slow” and “fast” loading are significantly different in the region of small deformations less than 2.5%; (iv) these values are close to each other in the loaded state for all deformations up to 10%; (v) a relief of the compression stress that creates plastic deformations causes a steep decrease in the coercive force that is as large as its increase following relief of plastic extension; this is explained by the emergence of a significant residual tension stress. The obtained results are of importance for the use of the method based on measuring the coercive force to test steel structures under the conditions when plastic deformations develop.__________Translated from Defektoskopiya, Vol. 41, No. 5, 2005, pp. 24–38.Original Russian Text Copyright © 2005 by Kuleev, Tsar’kova, Nichipuruk.     

The role of cementite in the formation of magnetic hysteresis properties of plastically deformed high-carbon steels: III. Magnetic properties of patented wire made of steel 25

Temperature dependences of the coercive force of mechanically alloyed cementite and wires made of patented steel 25 that were subjected to plastic deformation and subsequent annealing are presented. As is shown, cementite can be in both low-and high-coercivity states, for which the coercive force measured at room temperature is 80 and 240 A/cm, respectively; the coercive force measured at liquid-nitrogen temperature (?196°C) is 190 and 530 A/cm, respectively. Based on an analysis of the temperature dependences of the coercive force of deformed wires made of patented steel 25, the role of cementite in the formation of the coercive force of low-carbon steels was determined. It is shown that, in spite of a relatively small amount of pearlite, the contribution due to the magnetic hardness of cementite to the coercive force should be taken into account. In this case, the contribution due to the interaction of ferrite domain walls with weakly magnetic cementite inclusions is substantially lower.     

Relationship between the structure and physical-mechanical properties of U8A steel subjected to cold plastic deformation by hydrostatic extrusion

The structure and physical-mechanical properties of U8A high-carbon steel subjected to cold plastic deformation by hydrostatic extrusion have been investigated in a wide range of strain extents. Cold plastic deformation by hydrostatic extrusion has been shown to lead to the dispersion of the structure of U8A high-carbon steel. As the degree of true deformation increases, the ultimate strength and conventional yield limit of U8A steel monotonically grow by 2 and 3.6 times, respectively. Such parameters as coercive force, the number of jumps in magnetic Barkhausen noises, maximum magnetic permeability, residual induction, and the speed of elastic waves are more sensitive to changes in the dislocation density than in the dispersion of the grain and subgrain structure of extruded U8A steel. It has been established that at least two informative testing parameters are needed for nondestructive evaluation of the level of strength properties in extruded U8A steel. Those are coercive force (or maximum magnetic permeability, residual induction, the number of Barkhausen jumps, the speed of elastic waves) for a true deformation of up to 1.62 and the root-mean-square voltage of magnetic Barkhausen noises for true deformations above 1.62.     

Effect of aging and plastic deformation on the mechanical,magnetic, and thermal properties of cobalt-containing invars

The mechanical, magnetic, and thermal properties of water-quenched (from 1150°C) alloys, such as H36K10T3, H36K10X5T2, and H36K5T2, which were strengthened by aging (at 650°C) and high-temperature deformation (1100–800°C) followed by aging, are studied. The decomposition of a supersaturated solid solution in the Invar alloys under study was shown to increase the strength properties and coercive force but to decrease the plasticity and saturation magnetization. In this case, the aging ambiguously affects thermal expansion coefficient α of the different alloys; the temperature range of invariance decreases. The plastic deformation of Invars was found to increase the ultimate strength, yield strength, and coercive force. The additional aging of deformed materials increases the strength and decreases the plastic properties; among the magnetic parameters, the saturation magnetization exhibits the most adequate correlation with the mechanical properties. The thermal properties (the α coefficient and invariance range) resulting from the complex heat treatment differ slightly from those resulting from the single aging.     

Magnetic method for estimating uniaxial compressive and tensile elastic stresses

It is shown that uniaxial compressive and tensile elastic stresses can be controlled based on the coercive force, relaxation magnetization, and magnetic susceptibility in a multifactor model.     

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.