MANUFACTURING METHOD OF STRIPS OF LOW-ALLOYED WELD STEEL Russian patent published in 2016 - IPC C22C38/50 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to low alloyed steel used for making welded oil and gas pipelines, metal structures, suitable for use in far North conditions, for construction of marine structures and structures operated in aggressive media. Production of steel containing, WT%: carbon 0.05-0.13, Silicon 0.10-0.40, manganese 0.30-0.70, vanadium 0.04-0.12, niobium ≤0.01, aluminium 0.02-0.06, titanium ≤ 0.01, molybdenum ≤ 0.25, nitrogen ≤ 0.008, chrome 0.30-1.0, nickel ≤ 0.30, copper ≤ 0.30, sulphur ≤ 0.004, phosphorus ≤ 0.018, calcium 0.001-0.006, iron and impurities - the rest. Produced steel is subject to off-furnace treatment, vacuum, continuous casting into slabs and hot rolling. Hot rolling of strips is carried out in roughing stands to roll thickness not less than 4.3 units from nominal thickness of finished strip at rolling end temperature determined by expression RFT black = Ar₃(calc) + C×2350, [°C], and finishing stands at rolling end temperature determined by formula RFT = (960-806×C)±15, [°C], where C is the mass fraction of carbon in WT%. Strip is cooled at collecting roller table at a rate of not less than 10 °C/s and wound at temperature in range 530÷600 °C to obtain in the band banding of not more than 2 points and structure with the number of not more than 9 points without inclusions based on niobium and titanium carbonitrides particles.

EFFECT: higher corrosion resistance, cold resistance and yield ratio of hot-rolled strip.

3 cl, 3 tbl, 1 ex