FATIGUE CRACK RESISTANT STEEL SHEET FOR WELDING HAVING EXCELLENT JOINT FATIGUE STRENGTH

摘要

PROBLEM TO BE SOLVED: To provide a fatigue crack resistant steel sheet for welding having excellent fatigue strength in a welded joint.;SOLUTION: The fatigue crack resistant steel sheet for welding has a composition comprising, by mass, 0.01 to 0.10% C, 0.04 to 0.6% Si, 0.50 to 2.0% Mn, ≤0.006% P, ≤0.003% S, 0.003 to 0.06% Al, 0.001 to 0.10% Ti and 0.0020 to 0.0120% N, and the balance Fe with impurities wherein the content of B is ≤0.0007% and the content of O (oxygen) is ≤0.0030%, and in which the value of a carbon equivalent (Ceq) is 0.28 to 0.65%, and the cleanliness defined by formula; (the cleanliness of A based inclusions)×1+(the cleanliness of B based inclusions)×3+(the cleanliness of C based inclusions)×1.5 in a region to a depth of 2 mm in the sheet thickness direction from the surface of the steel sheet is 0.005 to 0.1%. The steel sheet may further comprise one or more kinds selected from ≤1.5% Cu, ≤1.5% Ni, ≤1.2% Cr, ≤1.0% Mo, ≤0.1% V, ≤0.10% Nb, ≤0.0010% REM and ≤0.0010% Mg.;COPYRIGHT: (C)2008,JPO&INPIT