TUBE STOCK OUT OF BORON CONTAINING STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/32 

FIELD: metallurgy.

SUBSTANCE: tube stock with diameter from 80 to 180 mm is produced out of steel containing elements, wt %: carbon 0.19-0.24, manganese 0.40-0.60, silicon 0.17-0.30, chromium 0.40-0.60, nitrogen 0.003-0.010, vanadium 0.020-0.040, aluminium 0.020-0.040, titanium 0.020-0.040, boron 0.001-0.003, iron and unavoidable impurities - the rest at maintaining conditions: 500-(Ti/24-N/7)+2.2≥0; 30≥C/0.01+B/0.001≥13, at that stock is hot rolled and has ferrite-pearlite structure, dimension of actual grain is 5-8 points, its macrostructure for central porosity, pointed non-uniformity, liquation square, sub-shrinking liquation - not more than 2 points in each kind, liquation strips - not more than 1 point, non-metallic inclusions - sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates, non-deformed silicates - not more than 4.5 points for each kind of inclusions. As impurities steel contains wt %: niobium not more than 0.020, molybdenum not more than 0.02, copper not more than 0.10, nickel not more than 0.10, sulphur not more than 0.012, phosphorus not more than 0.15. Stock possesses tensile strength of 480-650 H/mm², yield strength not less than 360 H/mm², specific elongation not less than 16%, contraction ratio not less than 50%, hardenability in water with critical diameter of Dcr=35mm, hardness at end tempering 40 HRC.

EFFECT: upgraded level of consumer characteristics_.

2 cl, 1 ex