STEEL SHEET AND STEEL PIPE FOR PIPELINES Russian patent published in 2013 - IPC C22C38/14 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: sheet is made of steel containing in wt %: C - 0.02 - 0.06, Si - 0.5 or less, Mn - 0.8 - 1.6, P - 0.008 or less, S - 0.0008 or less, Al - 0.08 or less, Nb - 0.005 -0.035, Ti - 0.005 - 0.025, and Ca - 0.0005 - 0.0035, Fe and unavoidable impurities making the rest. Additionally steel may contain one or several following elements, in wt %: Cu - 0.5 or less, Ni - 1 or less, Cr - 0.5 or less, Mo - 0.5 or less, and V - 0.1 or less. Index CP describing hardness in the zone of axial segregation makes 0.95 or less while steel carbon equivalent C_eq makes 0.30 or larger. Note here that C_P and C_eq are defined by: C_P=4.46C(%)+2.37Mn(%)/6+{1.18Cr(%)+1.95Mo(%)+1.74V(%)}/5+{1.74Cu(%)+1.7Ni(%)}/15+22.36P(%), while C_eq=C(%)+Mn(%)/6+{Cr(%)+Mo(%)+V(%)}/5+{Cu(%)+Ni(%)}/15.

EFFECT: higher resistance to hydrogen cracking.

9 cl, 2 dwg, 3 tbl, 1 ex