ROUND MILLED BAR WITH SPECIAL TREATED SURFACE OUT OF MEDIUM CARBON STEEL Russian patent published in 2008 - IPC C21D8/06 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: in production of bar with diameter up to 20 mm and with upgraded characteristics of machinability like cutting there is melted steel containing, mas.%: C (0.37-0.50); Mn (0.50-0.80); Si (0.17-0.37); Cr (0.15-0.25); S (0.20-0.040); V (0.005-0.02); Al (0.03-0.05); Ca (0.01-0.010); 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 - the rest at a ratio of As+Sn+Pb+5×Zn≤0.07; O₂/Ca=1÷4.5; Ca/S≥0.065; impurities Ni not more, than 0.30; Cu not more than 0.30; Mo not more, than 0.10; P not more, than 0.030. Bar has the following mechanical characteristics: hardness - not less, than 187HB, σ_t not less, than 600 MPa, δ not less, than 6%, ψ not less, than 30%; a medium mark of pointed sulphides with an oxide coat, pointed oxides, lined oxides, fragile silicates, plastic silicates, and non deformed silicates - not more, than 3.5 for each type of inclusions; than it has ferrite-pearlite structure; the dimension of an actual grain 5-9 points; curvature not more, than 1.0 mm per meter; maximum deviations for diameter not more, than 0.110 mm at the diameter of bar up to 20 mm and not more, than 0.130 mm at the diameter of bar from 20 to 34 mm; macrostructure is central porosity, pointed non uniformity, liquating square - not more, than 3 points for each type, sub shrinking liquation not more, than 3 points, liquating strips not more, than 1 point.

EFFECT: upgraded characteristics at cutting.

3 cl, 2 ex