HIGH-STRENGTH WELDABLE STEEL AND ITS VERSIONS Russian patent published in 1999 - IPC

FIELD: metallurgy, more specifically, high-strength weldable steels. SUBSTANCE: steel with lower content of carbon and high content of Mn-Ni-Mo-Ti traces, contains also such elements as Cu,B,Cr,Ca,V, etc. Steel has tempered martensite/bainite mixed structure containing, at least, 60 vol.% of tempered martensite in form of microstructure produced from nonrecrystallized austenite having average size of austenite grains not in excess of 10 mcm. Sum of fraction of said martensite and fraction of bainite amounts up to, at least, 90%. Design formula are offered for determination of hardenability index in steel hardening depending on steel chemical composition and ranging from 2.5 to 4.0. Claimed steel is ultrahigh strength steel featuring tensile strength of, at least, 950 MPa (not below 100 to AMI standard) and high low- temperature impact strength and weldability under field conditions in cold regions. EFFECT: higher efficiency. 8 cl, 1 dwg, 6 tbl