HIGH-STRENGTH AND DUCTILITY STEEL SHEET FOR MAKING MAIN PIPE, AND METHOD OF STEEL SHEET FABRICATION Russian patent published in 2013 - IPC C22C38/12 C21D8/02 C21D8/10 C22C38/48 

FIELD: metallurgy.

SUBSTANCE: proposed composition contains the following substances, in wt %: C - 0.04-0.15, Si - 0.05-0.60, Mn - 0.80-1.80, P - 0.020 or less, S - 0.010 or less, Nb - 0.01 - 0.08, Al - 0.003-0.08, iron and unavoidable impurities making the rest. Note here that quantity C_eq defined by the following formula C_eq = C + Mn/6 + (Cu + Ni)/15 + (Cr + Mo + Nb + V + Ti)/5 + 5B, makes 0.48 or less. Note also that steel structure is a combined structure consisting of ferrite and perlite, or ferrite and perlite partially beating bainite. Note that ferrite content in said structure makes 60% to 95%, its yield point makes 450 MPa and higher, while hydrogen content in steel makes 0.1 ppm or less.

EFFECT: increased strength and ductility.

3 tbl, 1 dwg