TUBULAR BILLET OUT OF CHROMIUM STEEL OF UPGRADED CUTABILITY Russian patent published in 2008 - IPC C21D8/10 C22C38/58 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: tubular billet is made out of steel, containing in wt %: carbon 0.12-0.17; manganese 0.30-0.60; silicon 0.17-0.37; chromium 0.30-0.60; sulphur 0.025-0.035; nitrogen 0.005-0.010; calcium 0.001-0.006; arsenic 0.0001-0.03; tin 0.0001-0.02; lead 0.0001-0.01; zinc 0.0001-0.005; iron and unavoidable impurities - the rest. At maintaining the ratio: (As+Sn+Pb+5×Zn)≤0.07, Ca/S≥0.055. As impurities steel contains in wt %: phosphorus not more, than 0.035; nickel not more, than 0.25; copper not more, than 0.30. The billet has ferrito-pearlite structure, dimension of an actual grain 5-10 points, macrostructure on central porosity, pointed nonuniformity and liquating square is not more, than 3 points in each kind, subshrinking liquation is not more, than 3 points, liquation strips are not more, than 1 point, nonmetal inclusions on sulphides, pointed oxides, strip oxides, fragile silicates, plastic silicates, undistorted silicates, sulphides and oxy sulphides of a globular shape are not more, than 4.5 points for each kind. The billet has ultimate tensile strength not less, than 687 N/mm², yield point is not less, than 491 N/mm², specific elongation - not less, than 12%, impact elasticity at an ambient temperature - not less, than 78.4 J/cm².

EFFECT: upgraded level of consumer properties of billet.

2 cl, 1 ex