ROUND MERCHANT SHAPES MADE FROM LOW-CARBON HIGH-DUCTILITY STEEL FOR COLD DIE FORGING OF INTRICATE-SHAPE FASTENING PARTS Russian patent published in 2005 - IPC

FIELD: metallurgy; manufacture of round merchant shapes from low-carbon high-ductility steel for cold die forging of intricate-shape fastening parts.

SUBSTANCE: merchant shapes are molten from low-carbon high-ductility steel containing the following constituents, mass-%: carbon, 0.07-0.15; manganese, 0.90-1.40; silicon, 0.01-0.20; chromium, 0.005-0.40; vanadium, 0.005-0.07; niobium, 0.005-0.02; sulfur, 0.005-0.020; aluminum, 0.001-0.006; calcium, 0.001-0.010; nitrogen, 0.005-0.015; the remainder being iron and unavoidable admixtures. At satisfaction of ratios 12/C-Mn/0.009≥50 and Ca/S≥0.065, maximum number of impurity of steel by non-metallic inclusions in sulfides, oxides, silicates and nitrides does not exceed 3 for each kind of inclusions; shapes have spheroidizing structure in length which contains no less than 80% of grain perlite, size of actual grain is number 5-10; diameter of wire ranges from 10 to 25 mm; provision is made for decarbonized layer not exceeding 1.5% of diameter; amount of cold heading is no less than 1/3 of height; tensile strength does not exceed 520 Mpa; relative elongation is no less than 22%; relative reduction of area is no less than 65%.

EFFECT: enhanced efficiency of cold die forging; improved ductility characteristics; low level of strain hardening.