| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a high-strength bolt which is superior in delayed fracture resistance and has a tensile strength of 1,400 MPa or higher, and to provide a manufacturing method therefor. <P>SOLUTION: The bolt comprises, by mass%, 0.15-0.6% C, 0.05-2% Si, 0.1-2% Mn, and 0.002-0.1% Al, further one or more elements of 0.05-2% Cr, 0.05-3% Mo, 0.05-1% V, 0.01-0.1% Ti and 0.01-0.1% Nb, and the balance Fe with unavoidable impurities; has the tensile strength of 1,400 MPa or higher; has a compressive residual stress in an amount of 20 to 95% of the tensile strength; and has the surface with ten points average height of irregularities of 10μm or less. The manufacturing method comprises the steps of: immersing the bolt adjusted to possess predetermined strength into a liquid; or forming a liquid film on the surface of the bolt; and condensing a pulsed laser beam onto the surface of the bolt and irradiating the surface with the laser beam to generate the compressive residual stress in an amount of 20 to 95% of the tensile strength in the surface of the bolt. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
