| 摘要 |
PROBLEM TO BE SOLVED: To provide steel for a high-strength bolt which can form a bolt head header by cold working even without conducting spheroidizing, has a tensile strength after tempering higher than 1,300 MPa, and is excellent in resistance to delayed fracture; a high-strength bolt excellent in resistance to delayed fracture; and a method for producing the bolt. SOLUTION: This steel for a high-strength bolt, excellent in workability and resistance to delayed fracture, comprises 0.32-0.42 mass% C, 0.15 mass% or lower Si, 0.40 mass% or lower Mn, 0.015 mass% or lower P, 0.008 mass% or lower S, 0.35-1.20 mass% Cr, 0.70-1.00 mass% Mo, 0.05-0.25 mass% V, 0.12-0.22 mass% Ti, 0.005-0.035 mass% Al, 0.010 mass% or lower N, 0.0005-0.0030 mass% B, 0.10 mass% or lower Nb if necessary, and the balance being Fe and unavoidable impurities. COPYRIGHT: (C)2003,JPO
|
