| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength rolled PC steel bar having YS (0.2% proof stress) of >=1,200 MPa, TS of >=1,400 MPa and elongation of >=4.5%. SOLUTION: This steel bar consists of steel containing, by mass, 0.8 to 1.3% C, in which the area ratio of pearlite is >=80%, and further, whose surface is subjected to indenting and has YS (0.2% proof stress) of >=1,200 MPa, TS of <=1,400 MPa and elongation of >=4.5%. The steel bar moreover contains 0.10 to 2.5% Si and 0.25 to 2.0% Mn and suitably contains one or more kinds of Al, Ti, Ca, rare earth metals, V and Nb and/or one or more kinds of B, Cr, Cu, Ni and Mo. A wire rod having the composition is isothermally transformed at 450 to 650 deg.C, is subjected to indent machining, is imparted with strain of 1 to 4% thereto, and then is subjected to blueing treatment at 200 to 500 deg.C for 5 to 600 sec, thereby obtaining the objective steel bar.
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