| 摘要 |
PURPOSE: High-strength and high-toughness round steel and a method of manufacturing the same are provided to secure high strength and high toughness with a reduced amount of expensive materials. CONSTITUTION: High-strength and high-toughness round steel comprises carbon of0.1-0.4 weight%, silicon of 0.1-0.6 weight%, manganese of 0.6-2.0 weight%, phosphorus of 0.06 weight% or less, sulfur of 0.06 weight% or less, vanadium of 0.1 weight% or less, nitrogen of 200ppm or less, and iron and inevitable impurities of the remaining amount. A method for manufacturing the high-strength and high-toughness round steel comprises the steps of: heating billet at 700-1300°C in a heating furnace and forming the billet into a round steel shape through rough rolling, intermediate rolling, and finish rolling(S10), rapidly cooling the round steel through a tempcore process to 400-700°C(S20), cooling the round steel through air cooling to 600 degrees below the room temperature(S30), and forming a tempered martensite layer on the surface of the round steel by allowing the latent heat to transfer from the center to the surface of the round steel(S40). |
