Weld heat-affected zone of toughness in excellent steel and welded joints , method of manufacturing the welded joints .

摘要

PROBLEM TO BE SOLVED: To provide a steel material which has excellent weld heat-affected zone toughness and is applicable as a steel for large structures, a welded joint, and a method for producing the welded joint.;SOLUTION: The steel material contains, by mass, 0.03 to 0.16% C, 0.3 to 2.0% Mn, 0.016 to 0.030% Ti, 0.025 to 0.100% V, 0.0016 to 0.0050% B and 0.0050 to 0.0200% N, and satisfies 0.3[Ti]+1.35[B]-0.0016≤[N]≤0.3[Ti]+0.12[V]+0.0035 and Y-0.02≤X≤Y+0.02: here, X=[C]+[Mn]/6+([Cu]+[Ni])/15+([Cr]+[Mo]+[V])/5+2[Nb], and Y=1.71×10^-4×H+0.32; wherein [M] denotes the content [mass%] of each element M; and H denotes assumed welding heat input [kJ/cm], and the effective crystal grain size in the weld heat-affected zone when welding is performed at the assumed welding heat input H is ≤35 μm.;COPYRIGHT: (C)2013,JPO&INPIT