TUBE STOCK OUT OF MEDIUM CARBON LOW ALLOYED STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, particularly to production of tube stock with diameter from 100 to 180 mm designed for fabricating of seamless tubes. To facilitate upgraded level of consumer characteristics at a minimal level of anisotropy of mechanical properties the stock is made out of steel, containing elements, wt %: carbon 0.41-0.48, manganese 0.30-0.60, silicon 0.17-0.37, chromium 0.05-0.30, sulphur 0.005-0.045, 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, calcium 0.001-0.005, iron and unavoidable impurities - the rest, at a following ratio: (As+Sn+Pb+5×Zn)≤0.07, 0.50≤ (C+Mn/6+Cr/5) ≤0.69. Impurities are, wt %: phosphorus not more, than 0.45, nickel not more, than 0.30, copper not more, than 0.25. The stock is subject to hardening and low tempering; it has ferrite-pearlite structure and the dimension of the actual grain is 5-10 points, macrostructure for central porosity, pointed non-uniformity, liquation square is not more, than 2.0 points, sub-shrinking liquation and liquation strips are not more, than 1 point, non metallic inclusions of pointed sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates, non deformed silicates are not more, than 2.5 points, tensile strength is 639 N/mm², yield point is not more, than 373^{N/mm2, specific elongation is not less, than 16%, contraction ratio is not less, than 40%.}

EFFECT: production of tube stock with upgraded level of consumer characteristics.

4 cl, 2 ex