High strength welding joint having excellent in toughness of high heat input welded zone

文件类型：PDF文档
文件大小：341K
PURPOSE : A welding joint comprising Fe, C, Si, Mn, Ni, Mo, Ti, B, Mg, Al, N, P, S, O, and other inevitable impurities is provided to secure high toughness in a high heat input welded zone of at least 500 kJ/cm by promoting the intragranular acicular ferrite transformation by using fine composite oxides (Mg, Ti)O and (Mg, Ti)O-(Ti, B)N-MnS. CONSTITUTION : A high strength welding joint having excellent toughness of a high heat input welded zone comprises, by weight percent, 0.01 to 0.2%% of C, 0.1 to 0.5%% of Si, 1.0 to 3.0%% of Mn, 0.5 to 3.0%% of Ni, 0.5%% or less of Mo, 0.01 to 0.1%% of Ti, 0.0003 to 0.01%% of B, 0.0005 to 0.005%% of Mg, 0.005 to 0.05%% of Al, 0.004 to 0.008%% of N, 0.03%% or less of P, 0.03%% or less of S, and 0.03%% or less of O with the balance being Fe and other inevitable impurities, wherein the Ti, O, Mg, N, B, Mn, and S satisfy 1.3<=Ti/O<=3.0, 8<=O/Mg<=20, 7<=Ti/N<=12, 0.8<=N/B<=1.5, 220<=Mn/S<=400, and 11<=(Ti+4B)/N<=16, and the joint has an acicular ferrite fraction of at least 85%%. The joint further comprises at least one of 0.0001 to 0.1%% of Nb, 0.005 to 0.1%% of V, 0.01 to 2.0%% of Cu, 0.05 to 1.0%% of Cr, 0.05 to 0.5%% of W, and 0.005 to 0.5%% of Zr. The joint further comprises at least one of 0.0005 to 0.005%% of Ca and 0.005 to 0.05%% of a rare earth metal. The joint has composite oxides (Mg, Ti)O and (Mg, Ti)O-(Ti, B)N-MnS with a particle size of 0.01 to 0.1 μm distributed therein in the number of 1.0×10^7 to 6.4×10^8/mm^2 of the joint. © KIPO 2008