TUBULAR PILLET MADE FROM LOW-CARBON MICROALLOYED STEEL Russian patent published in 2009 - IPC C21D8/10 C22C38/20 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: tubular billet of diameter from 80 till 160 mm is made from steel containing following ratio of components, wt %: carbon 0.13-0.17, manganese 0.45-0.65, silicon 0.17-0.37, chrome 0.5-0.70, vanadium 0.050-0.090, aluminium 0.02-0.05, calcium 0.001-0.05, niobium 0.005-0.030, nitrogen not more than 0.008, copper not more than 0.25, iron is the rest and unavoidable admixtures, at fulfillment of conditions; C+(Mn+Cr+Cu)/20+Si/20+N/60+V/10≤0.26, at that it has ferrite - pearlite structure, effective grain size 5-8 points, macroscopic structure by center porosity, point heterogeneity, liquation square, undershrinked liquation is not more than 2 points for each kind, liquation strips not more than 1 point, nonmetallics by sulphides, point oxides, stitch oxides, fragile silicates, flexible silicates, unstrained silicates not more than 4.0 points for each kind, tensile strength not less than 415 N/mm², yield strength not less than 241 N/mm², percent elongation not less than 20%, contraction ratio not less than 50%, impact strength KCU⁺²⁰ not less than 25 J/cm².

EFFECT: increased level of consumer properties at providing of favourable ratio of strength, ductility and toughness at minimal level of mechanical anisotropy.

2 cl, 1 ex