BAR OUT OF MEDIUM CARBON CHROMIUM CONTAINING STEEL FOR COLD DIE FORGING Russian patent published in 2008 - IPC C21D8/06 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention refers to bar of 15-32 mm diameter used for fabrication of ball pins by method of cold die forging. To increase forging and cutability characteristics of parts a bar is fabricated out of steel containing wt %: C - 0.38-0.45, Mn - 0.60-0.90, Si - 0.05-0.40, Cr -0.90-1.20, S - 0.020-0.040, Mo - 0.005-0.30, Ca - 0.001-0.010, N - 0.005-0.015, O₂ - 0.001-0.015, As - 0.0001-0.03, Sn - 0.0001-0.02, Pb - 0.0001-0.01, Zn - 0.0001-0.005, iron and impurities at the ratio of (As+Sn+Pb+5×Zn)≤0.07, O₂/Ca=1÷4.5, Ca/S≥0.065, at that the bar is made continuous cast and hot-rolled, it has fine dispersed ferrite-pearlite structure and dimension of actual grain 5-9 points, the depth of carbon free layer not more, than 1.5% from diameter to the side, value of cold shrinkage not more, than 1/3 of height, non-metallic inclusions of sulphides with oxide coating, pointed oxides, stripped oxides, fragile silicates, plastic silicates, non-deformed silicates not more than 3.5 points in each kind of inclusions, on macrostructure it has central porosity, pointed non-uniformity, liquation square and sub-shrinking liquation not more, than 3 points in each kind, liquation strips not more, than 1 point. Mechanical properties are σ_t not more, than 730 Mpa, δ not less, than 14%, Ψ less, than 45%, hardenability on hardness of a sample at end hardening at the distance of 1.5 mm from the end 53-61 HRC, cutability for value of wear of back edge of cutter h₃ not more, than 0.20 mm at cutting path L-1320 m.

EFFECT: upgraded mechanical properties.

4 cl, 2 ex