Central Scientifi c and Research Institute of Ferrous Metallurgy (TsNIIchermet) named after I. P. Bardin (Moscow, Russia):

Goli-Oglu E. A., Cand. Eng., Senior Researcher
Alistaev A. N., Researcher, e-mail: Goli-Oglu@yandex.ru

Engineering Technological Center, Vyksa Steel Works (Vyksa, Russia):

Ilyinskiy V. I., Cand. Eng., Chief Specialist
Muntin A. V., Chief Specialist
Naumenko V. V., Cand. Eng., Chief Specialist

The efficiency of various routes of thermomechanical controlled process in terms of obtaining the required level and uniformity of mechanical properties along the length of the rolled plate with thickness 21–26 mm and with strength grade K56 (X65) of low carbon micro-alloyed steel was defined. The influence of conditions of thermomechanical processing and accelerated cooling (TM+AC), low temperature thermomechanical processing and accelerated cooling (LTTM+AC) and low temperature thermomechanical processing (LTTM) on microstructure and morphology of microstructural components in the studied steels was determined. Experiments have been conducted in the conditions of up-to-date heavy plate mill 5000 at Vyksa Steel Works, and it was revealed that quasi-polygonal ferrite with irregular boundaries can be considered as microstructural matrix of investigated steels at TM+AC technological route, while upper and lower bainite is the high-carbon component. Usage of LTTM+AC technological route was characterized by forming the mixture of deformed and polygonal ferrite (degenerated pearlite and upper bainite as high-carbon component) and usage of LTTM technological route finalized in forming of strongly deformed ferrite and lamellar pearlite. It is concluded that variation of morphology of microstructural matrix in high-carbon components stipulates certainly changing the level of steel properties, opening possibility of wide creative approach to development of heavy plate production technology depending on the requirements to the quality of heavy plates, required productivity and composition of the main rolling equipment.

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