TUBE STOCK OUT OF MICRO ALLOYED STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/12 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, particularly to production of tube stock with diameter from 80 to 180 mm. To facilitate upgraded level of consumer characteristics as well as weldability and higher resistance to temper brittleness the tube stock is fabricated out of steel, containing, wt %: carbon 0.10-0.20, manganese 0.50-1.70, silicon 0.10-0.60, vanadium 0.01-0.20, niobium 0.005-0.05, molybdenum 0.001-0.10, chromium 0.005-0.30, nickel 0.005-0.80, 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: (As+Sn+Pb+5×Zn)≤0.07; (Cu+Cr+Mo)≤0.45. The stock is continuous cast, hot rolled, turned and has ferrite-pearlite structure with the dimension of the actual grain of 6-9 points, surface roughness R_z is not more, than 80 mcm, macrostructure for central porosity, pointed non-uniformity, liquation square, sub-shrinking liquation is not more, than 3 points for each kind, for liquation strips is not more, than 1 point, non-metallic inclusions for sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates and non-deformed silicates are not more, than 4.0 points for each kind, tensile strength is 390-730 N/mm², yield point is not less, than 275 N/mm², specific elongation is not less, than 19%.

EFFECT: production of tube stock with upgraded level of consumer characteristics, of weldability and higher resistance to temper brittleness.

4 cl, 3 ex