ROUND BAR OUT OF SPRING STEEL WITH SPECIAL TREATMENT OF SURFACE Russian patent published in 2008 - IPC C21D8/06 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, particularly to production of round bar in rods with diameter from 12 to 34 mm for further fabricating of heavy loaded springs of various applications. To facilitate upgraded level of consumer characteristics a rod is made out of steel, containing, wt % : C (0.55-0.65), Mn (0.70-1.00), Si (1.70-2.0), Cr (0.20-0.40), Ni (0.005-0.15), S (0.005-0.015), P (0.005-0.020), N (0.005-0.01), As (0.0001-0.03), Sn (0.0001-0.002), Pb (0.0001-0.01), Zn (0.0001-0.005), iron and unavoidable impurities - the rest, at ratio: (As+Sn+Pb+5×Zn)≤0.07; it has ferrite-pearlite structure without sections of graphite, martensite, bainite and Widmanstatte, the dimension of actual grain is 6-12 points, curvature is not more, than 1.0 mm per meter, ultimate deviations on diameter are not more, than 0.110 mm at the diameter of rolling to 20 mm, and not more, than 0.130 mm at the diameter of rolling from 20 to 34 mm, macrostructure for central porosity, pointed nonuniformity, liquation square, sub-shrinking liquation - not more, than 3 points in each kind, liquation strips - not more, than 1 point, non metallic inclusions on pointed sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates, non deformed silicates - not more, than 2.5 points for each kind of inclusions; tensile strength is not more, than 850 N/mm², yield point is not more, than 500^{N/mm2, hardness is 192-269 HB. Modulus of elongation is not less, than 200 000 N/ mm2, shear modulus is not less, than 80 000 N/mm2.}

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

2 cl, 1 ex