G. V. Bida

Coercive force measurements in nondestructive testing

The paper considers applications of coercive force meters with external electromagnets to nondestructive measurements of strength, plastic, and viscous properties of rolled high-carbon and low-alloyed steels, characterization of annealed high-carbon, predominantly chromium-doped, steels, testing of the quality of quenched and tempered steels, measurements of the depth and hardness of surface hardened layers on metallic components, and their use in sorting out different steels.

Feasibility of NDT of ferromagnetic steel structures based on measurements of residual magnetization as a function of elastic stress

Algorithms for estimating elastic stress in ferromagnetic steel structures are based on measurements of the residual magnetization Mr as a function of tensile and compressive stress σ0 after quenching and tempering at different temperatures Ttem. The suggested testing technique is highly sensitive because the range of Mr(σ0) is fairly wide (for the interval 0.6σy ≥ σ0 ≥ –0.6σy, where σy is the yield limit, the range is 600–800 kA/m). The necessary condition for using this testing technique is the availability of calibration curves for the selected testing algorithm measured on samples of steels to be tested (i.e., of the same sort of steel tempered at the same temperature). All the testing algorithms suggested in the paper enable one to determine both the magnitude and sign of the stress in the material.

SM-401 Magnetic Structuroscope

The SM-401 magnetic structuroscope is described. Operations carried out by means of the structuroscope and technical characteristics of the device are described. Factors determining the error in measurement of the coercive force are considered. The parameters of transducer of the magnetic structuroscope are estimated and the measurement results are outlined.

Magnetic Properties of Steels after Quenching and Tempering. III. High-Chromium Steels.

The paper describes effects of quenching and tempering processes on the magnetic properties, electric resistivity, and hardness of steels with the chromium content higher than 10%. These parameters have been measured as functions of the heating temperature for quenching and tempering of high-chromium steels with different carbon contents.

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.

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.

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.

Multiparameter methods in magnetic structuroscopy and nondestructive testing of mechanical properties of steels

Methods of nondestructive testing of the quality of metal in hot-rolled, thermally treated, and other states are considered for the cases when structural changes are diversified, one of such structural transformations having an opposite effect on the sensitivity of a particular characteristic to the accompanying transformation, and when one-parameter inspection according to the coercive force is either inefficient or impossible. The natures of the structural and phase sensitivity of the coercive force, the saturation magnetization, and the magnetic permeability are analyzed. Examples of the practical application of multiparameter magnetic structuroscopy are considered.

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.

Increasing the reliability of the multiparametric method for nondestructive testing of mechanical properties of articles

It is suggested that the corrected least squares procedure be applied in order to improve the results obtained during nondestructive testing of the service properties of articles by the multiparametric method. The result of the statistical manipulation, which is given in the form of a correlation between the calculated and experimental magnitudes of a tested property, improves the pair correlation in use of a procedure developed earlier [1]. The conditions of the expediency of applying such improvement are studied.