ROLLED SECTION MADE OF SPRING STEEL WITH SPECIAL SURFACE FINISHING Russian patent published in 2008 - IPC C21D8/06 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, particularly to production of rolled sections in bars with diameters from 12 to 34 mm. To upgrade the level of commercial characteristics the rolled section is produced from steel containing mass %: C-(0.58-0.63), Mn-(0.60-0.90), Si-(1.60-2.0). Cr-(0.20-0,40), Ni-(0.005-0.15), Cu-(0.005-0.15), S-(0.005-0.015), N-(0.005-0.01), As-(0.0001-0.03), Sn-(0.0001-0.02), Pb-(0.0001-0.01), Zn-(0.0001-0.005), the rest being iron and impurities - the rest, at the ratio: (As+Sn+Pb+5×Zn)-≤0.07, 0.73≤(C+Mn/6+Cr/5)<0.85. Steel additionally contains P not more than 0.20%. The bar is made hot rolled round and annealed; it has ferritic pearlight structure without sections of graphite, martensite, bainite and Widmanstatten patterns with the size of actual grain of 6-12 points. The curvature of the bar is not more than 1.0 mm per meter, maximum deviations on diameter being not more than 0.110 mm at the diameter of the bar of up to 20 mm and not more than 0.130 mm at the diameter of the bar from 20 to 34 mm. The macrostructure of the bar is central porosity, pointed nonuniformity, a liquation square is not more than 3 points per each kind, subshrinkage liquation is not more than 3 points per each kind, liquation strips are not more than 1 point. Nonmetallic inclusions are pointed sulphides, pointed oxides, lined oxides, fragile silicates, plastic silicates, undistorted silicates not more than 2.5 per each kind of inclusions. Mechanical properties after annealing are the following: tensile strength of not more than 850 H/mm², yield stress of not less than 500 H/mm², hardness of 192-269 HB, modulus of elongation of not less than 200000 H/mm², shear modulus of not less than 80000 H/mm².

EFFECT: upgraded level of commercial characteristics.

2 cl, 1 ex