Magnetic quality control of hardened and tempered parts made of carbon and low-alloyed steels (review)

The physical essence of the nondestructive quality control of mediate-and high-temperature tempering of parts made of carbon and low-alloyed steels containing more than 0.3% carbon, which is performed on the basis of measurements of the secondary residual magnetic inductance (magnetization) and relaxation coercive force of a body, is considered. Examples of the inspection of the hardness of tempered parts made of a number of steels of different grades are reported.     

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.     

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.     

On the efficiency of application of magnetic and electrical parameters for nondestructive testing of crystal-lattice microdistortions in heat-treated carbon steels

The effect of crystal-lattice microdistortions that characterize residual stresses in heat-treated steels that contain 0.36, 0.62, and 0.75% carbon on their magnetic characteristics, in particular, magnetic Barkhausen noise parameters, electrical resistivity, and elastic wave propagation velocity, which was determined by the electromagnetic acoustic transformation (EMAT) method, was studied. The coercive force and number of Barkhausen jumps for hardened steels are shown to correlate, to a great extent, with the average grain size rather than with crystal-lattice mirodistortions. Crystal-lattice microdistortions induced in steels upon hardening from different temperatures correlate adequately with the root-mean-square magnetic Barkhausen noise (RMS BN) voltage. When estimating crystallattice microdistortions in articles made from carbon steels subjected to marquenching and subsequent tempering, the combined use of the coercive force (for steels after low- and medium-temperature tempering) and RMS BN voltage (for steels after high-temperature tempering) is most efficient. Such parameters as the number of Barkhausen jumps, electrical resistivity, and elastic wave propagation velocity are less sensitive to changes in crystal-lattice microdistortions (CLMs) in heat-treated carbon steels.     

Magnetic Properties of Steels after Quenching and Tempering. I. General. Carbon Steels

The publication is composed of three parts. The first describes characteristics that are used in nondestructive tests of ferromagnetic components and assemblies, and the classification of these characteristics with structure- and phase-sensitive ones. Physical processes during quenching and tempering of carbon and low-alloyed steels are discussed, alongside their effect on the coercive force, saturation magnetization, electric resistivity, and hardness of the 30Kh3MFA, 40KhFA, and ShKh15 steels. These parameters are given as functions of the heating temperature in the processes of quenching and tempering of these steels.     

Magnetic Properties of Steels after Quenching and Tempering. II. Low-Alloyed Steels

The paper reports on the coercive force, saturation magnetization, relaxation magnetization and magnetic susceptibility, electric resistivity, and hardness of low-alloyed steels from a wide range as functions of the heating temperature for quenching and tempering.     

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.     

The influence of biaxial elastic deformation on the coercive force and local remanent magnetization of construction steels

The influence of biaxial elastic tension-compression and tension-tension deformation on the coercive force and remanent magnetization of Cτ3 steel and 09Γ2C pipe steel cross-shaped specimens is studied. It is shown that coercive force grows monotonically with increasing load in the direction of compression under elastic tension-compression deformation and almost does not change under elastic tension-tension deformation. The local remanent magnetization decreases for all the considered types of biaxial elastic deformation. The possibility of using these methods for the evaluation of the stressed state of complexly deformed carbon steel products is discussed.     

Effect of friction-induced hardening on the features of magnetic and eddy-current behavior of an annealed structural steel under cyclic loading conditions

The effect of friction processing on the mechanical properties in uniaxial tension, the magnetic properties, and the electromagnetic characteristics of an annealed Steel 3 (St3) grade structural steel has been studied. It is established that the coercive force, residual magnetic induction, initial magnetic permeability, and eddy-current characteristics can serve as parameters for monitoring the quality of steel hardened by friction processing. Features of friction-induced changes in the strength, magnetic properties, and electromagnetic characteristics of St3 grade steel loaded in the region of low-cycle fatigue are revealed. It is shown that magnetic and eddy-current techniques can be used for monitoring the state of a friction-hardened surface layer of steel samples in the course of their cyclic loading.     

Differential Magnetic Method of Nondestructive Testing and Phase Analysis

In tests of roller-bearing, tool, and other sorts of alloyed steels, two magnetic char-acteristics must be measured in nondestructive tests of quenched structures, namely, the saturation magnetization and coercive force. In industrial conditions, a differential method is used in measuring these parameters with the help of an instrument built around an H-shaped applied electromagnet. The paper considers utilization of this magnet in nondestructive measurements of hardness of bearing components manufactured from the ShKh15, ShKh15SG, and 95Kh18 steels, pump elements from the ShKh15 steel, and components manufactured by sintering. A technique for estimating the content of residual austenite in the mentioned sorts of steel and martensite in steels of transitional sorts, in particular, Kh16N6, is described.     

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.     

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.     

A setup for measuring the magnetic characteristics of soft magnetic materials and articles

An automated setup for measuring the normal magnetization curve, the major and minor magnetic-hysteresis loops, and the main (initial permeability, maximum permeability, residual magnetic induction, induction coercive force, and saturation induction) and additional (the permeability at a field equal to the coercive force, the field strength at which the saturation induction is reached, and the induction at fields equal to the coercive force and the double coercive force) magnetic parameters of soft magnetic materials and articles produced from them is described. Measurements are performed in an open or closed magnetic circuit at a magnetization-reversal frequency of 0.05–0.5 Hz. The block diagram of the setup and its main parameters and characteristics are presented. The operation of the setup and the possibilities of its application are considered.     

Modeling relations between physical properties and chemical composition of steels in quenched state

Linear statistical models with multiple parameters have been developed for predicting the magnitudes of the coercive force, saturation magnetization, electric conductivity, and hardness of highcarbon and alloyed steels of various chemical compositions quenched in the normal regimes.     

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.     

Measurement of the hysteresis characteristics of pipe steels under elastic and plastic tensile strain

The changes in the shape and characteristics of the major and asymmetric hysteresis loops of low-carbon pipe steels under the action of elastic and plastic tensile strains were studied. The hysteresis loop segments that experienced the most considerable transformations under the tension of a material were determined. The possibilities of the inspection of tensile strains by the coercive return magnetization and the magnetic field corresponding to a fixed magnetization on the descending branch of a hysteresis loop were shown.     

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

Variations of magnetic (coercive force H _c , residual induction B _r , maximum magnetic permeability μ_max, maximum magnetic-permeability field H _μmax, saturation magnetization J _max) 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.     

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.     

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.     

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.