| 摘要 |
PROBLEM TO BE SOLVED: To provide high strength and high toughness non-heat-treated bar steel in which both of strength and toughness are increased, and the balance of the strength and toughness is excellent, and to provide its production method. SOLUTION: The bar steel contains, by mass, 0.35 to 0.50% C, 0.1 to 0.6% Si, 0.5 to 1.5% Mn, 0.005 to 0.02% Al and 0.05 to 0.50% V, and the balance iron with inevitable impurities, and has a steel structure composed of a ferrite-pearlite dual phase structure in which the fraction of ferrite is 20 to 40%, the average lamellar spacing of pearlite is 0.05 to 0.20μm, and the average grain size of the ferrite surrounded by large-angle grain boundaries having a crystal orientation difference of≥15°is 2 to 10μm. COPYRIGHT: (C)2005,JPO&NCIPI
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