SECTION IRON MADE OF LOW-CARBON CHROME-BEARING STEEL FOR COLD EXTRUSION Russian patent published in 2008 - IPC C21D8/06 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention concerns metallurgy field. Particularly it concerns production pf section iron of diameter 20-50 mm for manufacturing piston pins by method of cold extrusion. For providing of rational conditions for piston pins upset forging at simultaneous increasing of processing plasticity and low level of strain hardening section iron is received from steel, containing wt %: C 0.12-0.18, Mn 0.40-0.60, Si 0.15-0.25, Cr 0.70-1.15, N 0.005-0.010, S 0.005-0.035, O₂ 0.001-0.010, As 0.0001-0.03, Sn 0.0001-0.02, Pb 0.0001-0.01, Zn 0.0001-0.005, iron and admixtures at ratios: As+Sn+Pb+5×Zn<0.07; 0.19<(C+Mn/6)<0.27, at that rolled iron has lamellar ferrite - pearlite structure, size of effective grain is 5-9 points, cold yielding not less then 1/3 of its height, nonmetallic by dotted sulfides, dotted oxides, stitch oxides, frail silicates, plastic silicates, silicates by non-straining with point not more then 3.0 for each kind, macrostructure by center porosity, spot inhomogeneity, liquation square, sweat is not more than 3 points for every kind, liquating strip is not more than 1 point, hardness is not more then 207 HB, σ_B not more than 500 MPa, δ not less than 18%, ψ not less than 55%.

EFFECT: providing of rational upset forging conditions of piston pins at simultaneous increasing of processing plasticity and low level of strain hardening.

4 cl, 1 ex