Relation of the internal demagnetization coefficient of a ferromagnetic material to the parameters of its saturation magnetic hysteresis loop: application to magnetic structuroscopy.

Changes in the structural parameters and physical and mechanical properties of a ferromagnetic material are reliably monitored using its intrinsic demagnetization coefficient, which arises due to mechanical stresses, inhomogeneities in the structure and anisotropy of the material. However, the determination of the internal demagnetization coefficient of a material requires a cycle of anhysteretic magnetization of thermally demagnetized material with precision measurements of its magnetization and subsequent statistical processing of the measurement results, which reduces the reliability and complicates the use of this coefficient in magnetic structuroscopy. When analyzing the relationship between the internal demagnetization coefficient of a ferromagnetic material and the parameters of the limiting loop of its magnetic hysteresis, the formula for indirect determination of the internal demagnetization coefficient of a ferromagnetic material by its coercivity, residual magnetization and technical saturation magnetization, derived earlier by the author, was used. The influence of heat treatment modes, chemical composition of steels and the ratio between their magnetic parameters on the structural heterogeneity of the studied materials is analyzed. The influence of heat treatment modes, chemical composition of steels and the ratio between their magnetic parameters on the structural heterogeneity of the studied materials is analyzed. An example of analysis of functional dependences and the range of possible changes in the internal demagnetization coefficient of a material at changes in its magnetic parameters in practically important ranges is given. The influence of carbon content in carbon steels on their internal demagnetization coefficient is studied. For the heat-resistant medium-carbon alloyed steel of 34CrMo4 grade, widely used in machine-building in the manufacture of forgings and fasteners, the range of quenching temperature variation, which provides the maximum structural heterogeneity of the quenched steel, has been established. It is shown that in the whole range of changes in tempering temperature of 34CrMo4 steel after quenching, the dependence of the internal demagnetization coefficient on these changes is monotonic. As a result of this study, the indirect determination of the internal demagnetization coefficient according to the proposed formula can be recommended for non-destructive control of tempering temperature of 34CrMo4 steel.