MEDIUM CARBON STEEL ROUND PROFILE CHARACTERISED BY INCREASED CUTTING MACHINABILITY Russian patent published in 2008 - IPC C21D8/06 C22C38/60 

FIELD: metallurgy; profile.

SUBSTANCE: profile is produced as steel bars, containing in mas.%: C (0.36-0.44), Mn (0.60-0.90), Si (0.15-0.30), Cr (0.80-1.10), S (0.040-0.75), 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 unavoidable impurities - the rest, at a ratio: (As+Sn+Pb+5xZn)<0.07, O₂/Ca=(1-4.5); Ca/S>0.020. Profile has not less than 75% of oxy sulfides with a sulfide coat of a medium dimension not less than 3 points, the rest are oxides pointed, oxides lined, silicates fragile, silicates plastic, silicates warp-free with a dimension in total of not more than 2.0 points, it has laminar ferrite-pearlite structure, and the dimension of an actual grain of 5-9 points, it also has macrostructure as a central porosity, a liquating square has not more than 3 points in each type, subshrinkage liquation is not more, than 3 points, liquation strips -not more, than 1 point, and mechanical characteristics in annealed or thermo refined condition are: hardness 180-220 HB, ultimate tensile strength -not less, than 950 MPa, yield point - not less, than 800MPa, S- not less, than 12%, a_"н" - KCU⁺²⁰ not less, than 60 J/cm².

EFFECT: facilitating of rational conditions for cutting machining with simultaneous upgrading of strength, viscosity and plasticity.

2 cl, 1 ex