| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high strength bolt having satisfactory delayed fracture resistance and having a strength of≥1,500 MPa, and to provide a method for improving its delayed fracture resistance. <P>SOLUTION: The high strength bolt having excellent delayed fracture resistance is composed of a steel having a composition comprising, by mass, 0.65 to 1.1% C, 0.05 to 2% Si, 0.2 to 2% Mn and 0.002 to 0.1% Al, and the balance Fe with inevitable impurities, and having a tensile strength of≥1,500 MPa, and in which the compressive residual stress in the surface layer of the under head part in the bolt is 20 to 90% of the tensile strength in the steel. The method for improving its delayed fracture resistance is further provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
