TUBING STOCK MADE FROM LOW-ALLOYED STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention concerns metallurgy field. Particularly it concerns manufacturing of tubing stock of diameter from 80 till 180 mm. For providing of increased level of consumer properties, favourable correlation between strength, flexibility and viscosity, reduced tendency to temper brittleness stock is made from steel containing mass %: carbon 0.34-0.40, manganese 1.40-1.65, silicon 0.17-0.37, vanadium 0.06-0.12, chrome 0.005-0.30, nitrogen 0.005-0.015, arsenic 0.0001-0.03, tin 0.0001-0.02, lead 0.0001-0.01, zinc 0.0001-0.005, iron and unavoidable admixtures -the rest, at fulfillment of following ratio; (As+Sn+Pb+5×Zn) ≤0.07, [C+Mn/6+(Cr+V)/5]≤0.72. In the capacity of unavoidable admixtures steel contains, mass%: niobium not more than 0.02, phosphorus not more than 0.030, sulphur not more than 0.030, nickel not more than 0.30, copper not more than 0.30, molybdenum not more than 0.10. Hot-rolled tubing stock is of lamellar ferrite-pearlitic structure. Dimension of valid grain is 6-9 points, macrostructure: center porosity, spot heterogeneity, segregation square, subshrink segregation is not more than 3 points for each kind, segregation streaks are not more than 2 points, nonmetallic inclusions: sulphides, spot oxides, stitch oxides, fragile silicates, flexible silicates, non-strained silicates are not more than 4.5 points for each kind of inclusions, tensile strength is not less than 689 N/mm², yield strength is not less than 552 N/mm², percentage elongation is not less than 13%, contraction ratio is not less 48%, impact resistance KCU+20°C is not less 60 J/mm².

EFFECT: receiving of steel tubing stock with high mechanical properties.

2 cl, 1 ex