TUBE STOCK OUT OF ALLOYED BORON CONTAINING STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: tube stock with diameter from 80 to 180 mm is produced out of steel, containing wt %: carbon 0.26-0.30, manganese 1.20-1.40, silicon 0.17-0.37, chromium 0.40-0.65, nickel 0.005-0.25, copper 0.005-0.35, aluminium 0.02-0.06, titanium 0.02-0.05, boron 0.001-0.004, nitrogen 0.005-0.010, arsenic 0.0001-0.03, tin 0.0001-0.02, lead 0.0001-0.01, zinc 0.0001-0.005, sulphur not more, than 0.025 and phosphorus not more, than 0.025, iron the rest at maintaining: (As+Sn+Pb+5×Zn)≤0.07; (Ti/48+Al/27)+N/14)≥(0.6×10^-3); at that the stock has ferrite-pearlite structure, dimension of actual grain is 6-9 points, its macrostructure for central porosity, pointed non-uniformity, liquation square, sub-shrinking liquation - not more than 3 points in each kind, liquation strips - not more than 2 point, non-metallic inclusions - sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates, non-deformed silicates - not more than 4.0 points for each kind of inclusions, tensile strength is not less than 862 H/mm², yield stress is not less than 758 H/mm², specific elongation is not less than 11.5%, contraction ratio is not less than 34%.

EFFECT: upgraded level of consumer characteristics at minimal level of anisotropy of mechanical properties.

2 cl, 1 ex