TUBE STOCK OUT OF MICRO-ALLOYED STEEL Russian patent published in 2009 - IPC C21D8/10 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, particularly to production of tube stocks of 80...180 mm diameter. To facilitate upgraded level of consumer properties the tube stock is made out of steel containing in wt %: carbon 0.060-0.20, manganese 0.30-1.40, silicon 0.10-0.40, vanadium 0.01-0.020, niobium 0.005-0.01, molybdenum 0.001-0.08, chromium 0.005-0.30, nickel 0.005-0.30, copper 0.005-0.30, titanium 0.001-0.04, aluminium 0.020-0.060, sulphur 0.005-0.020, phosphorus 0.005-0.025, nitrogen 0.005-0.020, 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: (arsenic+tin+lead+5×zinc)≤0.07. The tube stock is made continuous cast, hot rolled, normalised and turned, it has ferrite-pearlite structure, the dimension of actual grain is 6-9 points, the macro-structure on central porosity, pointed non-uniformity, liquation square, sub-shrinking liquation are not more, than 3 points in each kind, liquation strips -not more, than 1 point, non-metallic inclusions of sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates, and non-deformed silicates are not more, than 4.0 points in each kind of inclusions. Surface roughness R_z is not more, than 80 mcm, tensile strength is not less, than 300 N/mm², yield point is not less, than 190 N/mm², specific elongation is not less, than 24%, brittle shelf energy KV is (-10°C)≥28 J, KV (0°C)≥40 J.

EFFECT: facilitating upgraded level of consumer properties of tube stock.

4 cl, 3 ex