ROUND BAR OUT OF BORON CONTAINING STEEL FOR COLD DIE FORGING Russian patent published in 2008 - IPC C21D8/06 C22C38/60 C22C38/54 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, particularly to production of bar. To facilitate rational conditions of cold die forging of complex profile high tensile mounting units a bar is produced out of steel containing wt %: C 0.06-0.35, Mn 0.60-1.40, Si 0.001-0.37, S 0.005-0.020, Cr 0.001-0.35, V 0.001-0.05, Nb 0.005-0.02, Ti 0.01-0.04, B 0.0005-0.0050, Al 0.02-0.06, N 0.005-0.015, As 0.0001-0.03, Sn 0.0001-0.02, Pb 0.0001-0.01, Zn 0.0001-0.005, iron and impurities, at ratios: (As+Sn+Pb+5Zn)≤0.07; [3000×(Ti/24-N/7)+2.2]≥0. As impurities steel contains: phosphorus not more, than 0.25, copper not more, than 0.15, oxygen not more, than 0.004, molybdenum not more, than 0.10, nickel not more, than 0.10. The bar has metallic inclusions of sulphides, oxides, silicates, and nitrides not more, than 3 points in each kind, it has a ferrite-pearlite structure, the dimension of the actual grain is 5-10 points, the diameter is from 10 to 25 mm, a decarbonised layer is not less, than 1.5% from the bar diameter, the value of cold yielding is not less, than 1/3 of the height, tensile strength is not more, than 580 N/mm², yield point is not more, than 540 N/mm², specific elongation is not less, than 18%, contraction ratio is not less, than 55%, the cutoff diameter at oil quenching is not less, than 15 mm.

EFFECT: production of round bar with upgraded level of consumer characteristics.

9 cl, 7 ex