TUBING STOCK MADE OF LOW-ALLOY STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/14 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: tubing stock of diameter from 80 till 180 mm is implemented of steel containing wt %: carbon 0.18-0.23, manganese 0.45-0.65, silicon 0.17-0.37, chrome 0.005-0.70, vanadium 0.050-0.090, aluminium 0.020-0.050, calcium 0.001-0.05, niobium 0.005-0.030, copper is not more than 0.25, nickel is not more than 0.25, iron and unavoidable admixtures - the rest, at fulfillment of conditions: C+Mn/6+(Cr+V)/5+(Ni+Cu)/15≤0.43, at that it has ferrite - pearlite structure, effective grain size 5-8 points, macrostructure by center porosity, dotted nonuniformity, undershrinked gathering, segregate square is not more than 2 points for each kind, segregate strips is not more than 1 point, nonmetallics by sulfides, dotted oxides, stitch oxides, fragile silicates, plastic silicates, unstrained silicates not more than 4.0 points by each kind. In the capacity of unavoidable admixtures steel contains in wt %: arsenic is not more than 0.03, tin is not more than 0.02, lead is not more than 0.01, zinc is not more than 0.005, nitrogen is not more than 0.008, sulphur is not more than 0.010, phosphorus is not more than 0.015. Mechanical properties after normalising: tensile strength is not less than 500 N/mm², yield strength is not less than 390 N/mm², tensile strain is not less than 16%, contraction ratio is not less than 45%, and impact viscosity at room temperature KCU is not less than 20 J/cm².

EFFECT: favorable ratio of strength, flexibility and viscosity.

2 cl, 1 ex