| 摘要 |
<p>Provided is a high-strength bolt having a tensile strength of 1200 MPa or more, which further has excellent ductility and delayed fracture property, and excellent impact resistance which could not be obtained before. The high-strength bolt has a tensile strength of 1.2 GPa or more, and has a threaded portion and a neck cylindrical portion. In the high-strength bolt, if the effective section area of the neck cylindrical portion having a diameter larger than that of the threaded portion is represented by Ao, the hardness of a portion at which Ao is measured is represented by Ho, the effective section area of the threaded portion is represented by As, and the hardness of the threaded portion is represented by Hs, K=(Ao x Ho)/(As x Hs) is 0.8 or more, and Ho < Hs is satisfied.</p> |
