HOT ROLLED STEEL SHEET OF HIGH TOUGHNESS AT ULTRALOW TEMPERATURE AND METHOD FOR PRODUCTION THEREOF Russian patent published in 2006 - IPC C21D8/02 C22C38/48 C21C5/28 

FIELD: metallurgy, in particular production of hot rolled steel sheet for main pipelines.

SUBSTANCE: claimed sheet is made of steel containing (mass %) 0.04-0.07 C; 1.5-1.65 Mn; 0.15-0.25 Si; at most 0.010 P; at most 0.003 S; 0.040-0.060 Nb; 0.040-0.060 V; 0.010-0.020 Ti; 0.10-0.30 Mo; 0.10-0.30 Ni; and balance: Fe and inevitable impurities. Method for steel sheet production includes spheroidization of non-metal enclosures using Ca-Si in process of secondary refining under slug of molten steel having abovementioned composition; heating of spheroidizied steel workpiece at 1150-1180°C; roughing down of heated workpiece at reduction ratio of 25-30 % and temperature of 900-930°C during the last gate; finishing rolling obtained steel workpiece at 790-830°C to provide acilular ferrite; and coiling of steel workpiece obtained by finishing rolling at 540-580°C after fast cooling.

EFFECT: steel of high strength, high toughness at low temperature and prolonged durability at extreme environmental conditions.

2 cl, 3 dwg, 5 tbl, 2 ex