Snizhnoi G. Scientific basis of the influence of magnetic state of the structure on the properties of austenitic steels

The object of research - the processes of influence of the structural-magnetic state (specific paramagnetic susceptibility) of austenite onthe beginning of the martensitic transformation, mechanical and corrosion properties of austenitic nickel-chromium, high-manganese and manganese-chromium steels. The subject of research - stability of austenite, temperature (gamma - alpha) and deformation (gamma - alpha, gamma - epsilon - alpha) martensitic transformations, physicomechanical and corrosion properties of austenitic steels and alloys. The purpose of research - solve the scientific-practical problem of predicting the mechanical and corrosion properties of austenitic steels by studying the changes in the structural-magnetic states and the austenite transformations as a result of temperature and deformation. Methods and techniques of research: theoretical work studies are based on the fundamental positions of classical thermodynamics; experimental methods: magnetometry, metallography, electron microscopy, X-ray diffraction and energy dispersion analysis of the distribution of elements, standard methods of estimating corrosion and mechanical properties; the experiment (automated equipment type Faraday weighing) and the processing of results was performed with the use of computers and related software (Excel, Statistica, Matlab). The obtained results - a new approach to the investigation of austenitic steels from the point of view of the atomic-magnetic state of austenite is proposed. The magnetometric method for determining the actual deformation martensitic point is proposed. The classification of the austenite stability states and thermodynamic schemes for the change in the specific free energies of austenite and martensite is proposed and experimentally confirmed. The paramagnetic epsilon phase, which occurs in plastic deformation of austenitic steels, is identified by the magnetometric method. A magnetometric diagram of stability of austenite of chromium-nickel steels has been developed. A specific paramagnetic susceptibility of austenite as index of stability to martensitic transformation is proposed. The influence of low ferrite content (<0.5%) on the corrosion properties of austenitic steels was determined. The correlation between the mechanical and corrosion properties of austenitic steels with the atomic-magnetic state of the austenite has been experimentally discovered. An express method of valuation of these properties is proposed, which is implemented at the enterprises of Ukraine: PrJSC "Dneprospetsstal", "Metinvest Mariupol machining and repair plant" LLC, "Ukrspetsmash" LLC and "Progress Mashbud" Ltd. Scope of application - mechanical engineering.