METHOD OF PRODUCING HOT-ROLLED SHEETS OF LOW-ALLOYED STEEL OF K65 STRENGTH GRADE FOR LONGITUDINAL ELECTRIC-WELDED PIPES Russian patent published in 2017 - IPC C21D8/02 C22C38/00 

FIELD: metallurgy.

SUBSTANCE: incessantly-cast subproduct of steel containing, wt %: carbon 0.04-0.07, silicon 0.15-0.35, manganese 1.45-1.60, chromium 0.22-0.30, nickel 0.24-0.30, copper not more than 0.15, titanium 0.015-0.030, vanadium 0.050-0.065, niobium 0.035-0.050, molybdenum 0.23-0.30, nitrogen not more than 0.007, aluminium 0.020-0.060, sulfur not more than 0.002, phosphorus not more than 0.012, iron and unavoidable impurities are the rest, is heated to a temperature of 1190±10 °C, subjected to rough rolling with specified reduction into an intermediate thickness, multiple of 4- thickness of the finished sheet, roll is cooled down, finish rolling is carried out at the start temperature of 720-745°C and the finish temperature of 755-770°C, rapidly cooled down into the controlled cooling set to temperature of 510-550°C, and then in the air with sheet structure mainly consisting of ferrite and bainite.

EFFECT: provision of satisfactory fracture strength of steel at a temperature of minus 5 degrees.

4 cl, 3 tbl