TUBULAR BILLET OUT OF BALL BEARING STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/60 

FIELD: metallurgy; tubular billet production.

SUBSTANCE: tubular billet is made of steel, containing in mas.%: C (0.95- 1.05), Mn - (0.15-0.30), Si - (0.15-0.30), Al - (0.005-0.025), V - (0.005-0.03), Cr - (0.27-0.50), N - (0.005-0.010), As - (0.0001-0.03), Sn - (0.001-0.02), Pb - (0.0001-0.01), Zn - (0.0001-0.005), iron and impurities- the rest, at a following ratio of elements: As+Sn+Pb+5×Zn<0.07, impurities: phosphorus - not more, than 0.027%, sulphur - not more, than 0.20%, copper- not more, than 0.25%, molybdenum - not more, than 0.03%, oxygen - not more, than 0.0015%. The tubular billet has a structure of a grained pearlite; the dimension of a real grain is 6-9 points. Macrostructure of the tubular billet is central porosity, pointed nonuniformity, subshrinkage liquation is not more, than 2 points in each type, a liquation square and liquation strips - not more, than 0.5 points. Nonmetallics are pointed sulphides, pointed oxides, lined oxides, fragile silicates, plastic silicates, warp free silicates - not more, than 2.0 points in each type of inclusions.

EFFECT: tubular billet has a minimum level of anisotropy of mechanical properties and increased resistance to temper brittleness.

4 cl, 2 ex