METHOD FOR PRODUCING OF STEEL SHEET (VERSIONS) AND STEEL SHEET Russian patent published in 2004 - IPC

FIELD: metallurgy, in particular, production of steel sheets from high-strength, weldable, low-alloy three-phase steel with excellent toughness at cryogenic temperatures.

SUBSTANCE: method involves heating steel slab including iron and certain weight content of some or all additions of carbon, manganese, nickel, nitrogen, copper, chromium, molybdenum, silicon, niobium, vanadium, titanium, aluminum and boron; squeezing slab for forming sheet in one or several passes in temperature range, within which austenite recrystallization occurs; rolling sheet in several passes in temperature range below austenite recrystallization temperature and higher than Ar₃ transition point; providing final rolling of sheet in temperature range between Ar₃ transition point and Ar₁ transition point; quenching ready rolled sheet to predetermined quenching stop temperature (QST); finishing quenching process. Method allows steel toughness to be increased and ductile-brittle transition temperature of basic steel in cross direction and in heat-affected zone (HAZ) to be reduced to -62⁰C. Steel produced by method has excellent toughness at cryogenic temperatures in basic steel sheet and in heat-affected zone, rupture strength exceeding 830 MPa and microstructure including ferrite phase, second phase of substantially lamellar martensite and lower bainite, and retained austenite phase.

EFFECT: improved quality of steel sheets and increased efficiency of method.

27 cl, 6 dwg, 4 tbl