| 摘要 |
FIELD: ferrous metallurgy. ^ SUBSTANCE: invention provides round-profiled iron smelted from low-carbon steel composed of, wt %: carbon 0.17-0.25, manganese 0.30-0.65, silicon 0.01-0.17, sulfur 0.005-0.020, vanadium 0.005-0.07, niobium 0.005-0.02, calcium 0.001-0.010, iron and unavoidable impurities - the balance. When following relationships are fulfilled: 12/C-Mn/0.02 >= 27; 0.46 >= 6V+8Nb >= 0.22; Ca/S >= 0.065, rolled iron has following characteristics: maximum degree of pollution with nonmetal inclusions, in particular sulfides, oxides, silicates, and nitrides, does not exceed 3 points for each type of inclusions; longitudinally uniform spheroidized structure composed of at least 80% grainy perlite; effective grain size 5-10 points; diameter 10-25 mm; carbon-free layer not exceeding 1.5% of diameter; cold setting value at least 1/3 height; point of maximum load not higher than 550 MPa; relative elongation at least 20%; and relative contraction at least 60%. ^ EFFECT: ensured optimal conditions for cold die forging of high-strength geometrically complex fastening members and simultaneously ensured improved characteristics of in-process plasticity and low level of stray hardening. |
