TUBE STOCK OUT OF MICRO ALLOYED STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/12 C22C38/42 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, particularly to production of tube stock with diameter from 80 to 180 mm designed for fabricating of seamless tubes of various applications. The tube stock is made out of steel, containing, wt %:_{carbon 0.16-0.27, manganese 0.34-1.00, silicon 0.17-0.37, chromium 0.005-0.20, molybdenum 0.001-0.10, copper 0.005-0.20, nickel 0.005-0.20; nitrogen 0.005 -0.008, niobium 0.005-0.010, vanadium 0.005-0.020, titanium 0.005-0.040, iron and unavoidable impurities - the rest, at maintaining the following conditions:V+Nb≤0.02; C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15≤0.43. As impurities steel contains (wt. %): aluminium not more, than 0.50, sulphur not more, than 0.025, phosphorus not more, than 0.025. The stock is made continuous cast, hot rolled, it has ferrite-pearlite structure, the dimension of the actual grain is 5-8 points, macrostructure for central porosity, pointed non-uniformity, liquation square, subshrinking liquation is not more, than 2 points for each kind, liquation strips not more, than 1 point, non-metallic inclusions for sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates, non-deformed silicates not more, than 2.5 for each kind. Tensile strength is not less, than 415 N/mm², yield point is not less, than 241 N/mm², specific elongation is not less, than 24%.}

EFFECT: facilitating optimal combination of hardness, plasticity and viscosity of tube stock.

2 cl, 1 ex