The role of cementite in the formation of magnetic hysteresis properties of plastically deformed high-carbon steels: II. Magnetic properties of patented wire made of steel 70

It is shown that, during discussion of the mechanism reliable for formation of the coercive force in high-carbon steel, in addition to the interaction between the domain walls and weakly magnetic cementite inclusions, the contribution from the cementite’s magnetic hardness should be considered. With the use of the temperature dependence of the coercive force in deformed and annealed specimens, the contribution of each of the considered mechanisms to the specimens’ coercive force is estimated.     

Magnetic inspection of the hardness of cast-iron milling rolls

The effects of the chemical composition and parameters of the cast-iron smelting and teeming process on the coercive force have been studied. It is shown that only chromium and carbon appreciably affect the coercive force. For rolls with cylindrical surfaces cast from ТПХН-60 iron, a reliable correlation has been established between the hardness and readings of a coercimeter with an attachable electromagnet. For flanges and blooming passes of sizing rolls made from ТШХН-50 cast iron, equations for the relation between the hardness and readings of a coercimeter have been obtained and analyzed. These equations can be used in nondestructive testing of hardness.     

Magnetic Properties of a Body as Nondestructive Testing Parameters of Tempering Quality of Quenched Steels (a Review)

The paper considers a nondestructive method for the monitoring of middle- and high-temperature tempering quality of steel workpieces with the carbon content higher than 0.3%. The method is based on measurements of the relaxation coercive force and the secondary residual magnetic induction of the body when remagnetization of the workpieces is carried out by means of permanent and alternating magnetic fields or by their superposition. It is shown that the possibility of this monitoring is ensured by the structural susceptibility of magnetic properties due to reversible displacements of domain walls, namely, the relaxation magnetization and magnetic susceptibility. The secondary residual magnetic induction of the matter and the relaxation coercive force of the matter cannot be used for this testing. The limiting workpiece shape factor below which this testing is possible is determined.     

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.     

Influence of the sintering agglomeration regime on the magnetic properties and hardness of specimens made of powder steels 30NM and 30N2M

The dependences of the magnetic properties and hardness of powder-sintered steels 30NM and 30N2M with different densities on the sintering temperature are studied. It is shown that, for specimens with the studied compositions, there is a correlation between the combined parameter produced by the coercive force and saturation magnetization and the steel tempering temperature and hardness.     

Magnetic properties of cementite and the coercive force of a Fe-5 at % C alloy after hardening and tempering

The role of cementite in the mechanisms of formation of H _c for specimens of a model high-carbon Fe-5 at % C alloy after hardening and tempering is determined from the analysis of the temperature dependences of the coercive force measured in the range from the temperature of liquid nitrogen to the Curie point for cementite. This analysis is based on the different characters of the temperature dependences of the contributions to H _c due to cementite as weakly magnetic inclusions at which the matrix’s domain walls are decelerated and cementite as a hard magnetic phase. It is shown that the magnetic hardness of cementite makes the main contribution to the formation of the coercive force in the region of medium and high tempering temperatures.     

The Structure and the Magnetic and Mechanical Properties of Steel M74 and the Possibility of Nondestructive Testing of Heat-Treatment-Hardened Rails

Dependences of the coercive force, the relaxation magnetization, the hardness, and the strength and plastic properties of steel M74, intended for manufacturing railroad rails, on its tempering temperature were studied. Hardened specimens have the martensite structure as well as the sorbite structure of different dispersity. Analogous dependences of critical fields, which correspond to the displacement of 180° and 90° domain walls during the magnetization reversal, and of the induced magnetic-anisotropy field were also analyzed. An MC-ИФМ magnetic structure analyzer was shown to be suitable for the nondestructive testing of the mechanical properties of finished rails. The correlation model is two-parameter; i.e., analyzer readings are used that were recorded after successive magnetization reversals of inspected sections of rails to magnetic fields corresponding to two different currents in the electromagnetic coils.     

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.     

Coercive Force and Distribution of Critical Fields in Two-Layered Ferromagnets of Various Hardness. I. Toroidal Samples

The paper reports on a calculation of coercive forces in two-layered toroidal samples composed of rings with various magnetic hardness on the base of magnetic hysteresis loops characterizing materials of each component. Secondary spectra of magnetic hardness of two-layered samples, characterizing distributions of critical fields in the process of cyclic magnetization, have been investigated. A suggested method for estimating the fractions of harder and softer components in composite samples uses the secondary spectra of magnetic hardness.     

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.     

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.     

Magnetic testing of hardness of cast railcar steel 32Х06Л after quenching and high-temperature tempering

The structure and strength and the magnetic properties of 32Х06Л steel subjected to quenching and tempering at different temperatures are studied. Based on statistical-modeling and experimental results, it has been established that coercive-return induction is a suitable parameter for controlling hardness. Another parameter, coercive force, can be used for estimating the phase composition of material. Local measurements of suggested testing parameters are possible with portable magnetic-measurement hardware–software systems of the SIMTEST-2 type.     

Decrease in the effect of a gap on coercimetry results when taking the properties of an attachable transducer into account

A method that allows the effect of a gap on the results of coercimetric quality control of articles to be decreased that is based on taking properties of an attachable transducer into account is proposed. The properties of a transducer are taken into account using a preliminary recorded demagnetization line of an attachable electromagnet whose magnetic circuit is not closed by an article. It is shown that the tangential component of the magnetic field of an inspected article during magnetization reversal along this line equals the coercive force of the article if its cross section does not exceed the electromagnet cross section.     

Non-destructive testing of residual stresses by magnetic methods under conditions of simple stressing

We have shown how crucial it is to determine the residual stresses (RS) at the stages of the product life cycle by means of the non-destructive testing (NDT) magnetic methods and to create computational algorithms and models. The experimental results of the RS in rod-shaped specimens after the 3-point-bending by magnetic-noise analysis and coercive force measurement are proved as being topical. The interrelations between the value of the change undergone by magnetic characteristics that are measured by the NDT magnetic methods and the value of the axial RS resulted from modeling by finite element method are revealed.     

Magnetic tests of hardness and structure of rail steel

The correlation between the coercive force on the one side, and the structure and hardness of the rail steel on the other has been studied. A technique for testing rails quenched in oil based on measurements of the coercive force has been developed. The technique can be used in acceptance tests of rails by stages of main rail-roads.     

Evaluation of the Current Condition and the Residual Lifetime of Forming Rolls Using the Magnetic Method of Nondestructive Testing Based on the Coercive Force

The magnetic method on the basis of the coercive force H_c is proposed to use for estimating the current condition and the residual lifetime of forming rolls. Sixty rolls have been tested. It is shown that H_c increases almost twice in exploiting the roll from the beginning of the operation to reaching the limit of its lifetime. Results of observation of the degree of nonuniformity of the H_c distribution over the roll surface in the operation process are given. The results of investigation make it possible to optimize the path of each roll through the mill stands in order to avoid the stress concentration at the same depth of the roll operating (magnetic) coating in the roll change process. Using the magnetic testing method based on H_c makes it possible effectively to estimate the current condition of accumulation of the fatigue in the roll operating (magnetic) coating.     

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.     

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 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.     

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.