| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength PC (prestressed concrete) steel bar in which the delayed fracture resistance of a spot-weld zone is satisfactory, and which has a strength of≥1,400 MPa, and to provide a method for improving its delayed fracture resistance. SOLUTION: The high strength PC steel bar having excellent delayed fracture resistance is composed of a steel having a composition comprising, by mass, 0.2 to 0.6% C, 0.05 to 3% Si, 0.3 to 2% Mn and 0.002 to 0.1% Al, and, if required, comprising one or more kinds selected from 0.05 to 3% Ni, 0.05 to 2% Cr, 0.05 to 2% Mo, 0.02 to 1% V, 0.005 to 0.5% Nb, 0.003 to 0.5% Ti and 0.003 to 0.005% B, and the balance Fe with inevitable impurities, and having a tensile strength of≥1,400 Mpa, and in which the residual stress in the surface layer of the spot-weld zone joined with a reinforcing bar is 10 to 90% of the tensile strength. The method for improving its delayed fracture resistance is further provided. COPYRIGHT: (C)2006,JPO&NCIPI
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