Tverdokhvalov V. Non-destructive magnetic control of structural and mechanical properties of castings from steels and cast-iron

In the dissertation work the interconnection of structure, hardness and residual magnetization of samples from iron, carbon steels and pig iron with different carbon content (and graphite form for cast iron), in casting state and after various types of heat treatment is investigated. The main purpose of the study is due to the need for the development of non-destructive methods for controlling the structural-phase state and the hardness of ferromagnetic alloys, which, according to the reliability of direct methods for controlling their hardness, are based on the physical sensitivity of the magnetic characteristic to the structural changes in the alloy. The known methods of direct and indirect non-destructive control of the structural-phase state and hardness of steels and cast-iron are analyzed. The principle of magnetic control by means of measuring the characteristics of residual local magnetization of casting in the field of magnetic scattering over the surface of the magnetization zone is substantiated and chosen. The topography of the distribution of components of the residual magnetization vector over this zone is investigated and a unique structural-sensitive magnetic characteristic of the field of local magnetic dispersion is selected. The information about the results of experimental and industrial verification of research results and recommendations for their practical use is given. The results of the dissertation work contribute to the solution of various practical problems of non-destructive control in the field of foundry and metallurgy of steels and cast-iron, and the simplicity, convenience of measurement and wide functional capabilities of the investigated magnetic characteristics allow to develop several variants of mobile electronic devices. The measurement speed, as well as the lack of the need for surface preparation for measurement, make such devices a convenient means of control for technologists, especially when working out the technology of casting and the choice of thermal processing modes.