HIGH-STRENGTH TWO-PHASE STEEL PLATE WITH INCREASED RIGIDITY AND WELDING SUITABILITY Russian patent published in 2000 - IPC

FIELD: production of high-strength steel used in construction and manufacture of pipes. SUBSTANCE: invention deals with provision of microstructure uniform over thickness of plate having thickness of 10.0 mm as minimum and with growth of customary fraction of bainite/martensite to approximately 75% and higher. High-strength steel composition carrying ferrite phase and martensite/bainite phase in which ferrite phase has initial formation of carbide or carbonitride of vanadium and niobium is produced by way of first rolling at temperature above that of austenite recrystallization, by way of second rolling at temperature below that of austenite recrystallization, by way of cooling to temperature between transformation point Ar₃ and 500 C and by way of cooling in water to temperature below 400 C approximately. EFFECT: provision of microstructure uniform over thickness of steel plate. 11 cl, 5 dwg, 5 tbl