Development of scientific ideas on phase and structural transformations in steels for different application

Abstract

Purposeful control of structural state of steel at every stage of technological chain of steel goods production is necessary for elaboration of effective metallurgical technologies. The purpose of the complex of research and theoretical studies was development of ideas on peculiarities of structure formation of various steel grades. Current conceptions about phase and structural transformations in steels with different contents of carbon and alloying elements considered. For carbon and alloyed steels, the results of the study of the structure of perlite formed at different temperatures summarized; morphology, crystallography and defects of crystalline structure of cementite, processes of its fragmentation, coagulation and spheroidization; crystallography of austenite degradation products; evolution of the structure during cold and hot plastic deformation; carbon redistribution processes prior to and during diffusion-controlled austenite decay presented. For low-carbon low-and sparingly alloyed cold-resistant weldable steels generalized results of investigation of structure-formation processes, alloying relationships, temperature-deformation rolling conditions, parameters of quenching and high-temperature tempering with structure, mechanical properties and performance characteristics of steel plates presented. The elaborated complex of scientific and technical solutions based on the studies enabled to master and digitize production technologies at PJSC “Magnitogorsk steel-works” of new generation steel rolled products intended for ship-building, oil and gas industries, automobile, hardware and construction industries. The new systems of alloying steels of various application, methods of the new generation steels production and automated control of technological processes protected by 27 patents of RF, are widely used in the production activity of PJSC “Magnitogorsk steel-works”.

Rationale for signs of transformation in iron near 200°C

“…The maximum is reached after tempering at 200°C not only by the impact strength associated with the movement of dislocations, but also by the critical stress during stress corrosion not associated with this movement [37,38,39], since the fracture is macro-brittle.…”