AGE-HARDENING STEEL

摘要

An age-hardenable steel having a chemical composition consisting of: C: 0.05 to 0.20%, Si: 0.01 to 0.50%, Mn: 1.5 to 2.5%, S: 0.005 to 0.08%, Cr: 0.03 to 0.50%, Al: 0.005 to 0.05%, V: 0.25 to 0.50%, Mo: 0 to 1.0%, Cu: 0 to 0.3%, Ni: 0 to 0.3%, Ca: 0 to 0.005%, and Bi: 0 to 0.4%, with the balance being Fe and impurities, wherein within the impurities, P ‰¤ 0.03%, Ti < 0.005%, and N < 0.0080%, and further [C + 0.3Mn + 0.25Cr + 0.6Mo ‰¥ 0.68], [C + 0.1Si + 0.2Mn + 0.15Cr + 0.35V + 0.2Mo ‰¤ 0.85], and [-4.5C + Mn + Cr - 3.5V - 0.8Mo ‰¥ 0.00]. Wherein, the hardness before aging treatment is not more than 290 HV, with a quantity of hardening by aging treatment being not less than 25 HV, and fatigue strength is not less than 350 MPa as well as absorbed energy at 20°C after aging treatment is not less than 16 J when evaluated by a Charpy impact test performed by using a standard specimen with a U-notch having a notch depth of 2 mm and a notch bottom radius of 1 mm, and therefore the age-hardenable steel is quite suitable for a starting material for mechanical parts.