| 摘要 |
PROBLEM TO BE SOLVED: To provide a welded joint capable of using a steel product requiring no special control as a base material upon production, further having excellent working efficiency upon welding and further having excellent fatigue properties.SOLUTION: In a welded joint, a steel product includes a desired componential composition, 90% or more of the metallic structure of the steel product is composed of ferrite and bainite by an area ratio, also, the componential composition of the steel member satisfies formulae of Kp=[Mn]+1.5[Cr]+2[Mo]=2.4 to 4.5 and [Ti]/[N]=1.5 to 4.0, and further, the hardness gradient of the HAZ portion satisfies formula of &Dgr;Hv/L<150. |
