WELDING JOINT HAVING EXCELLENT IN TOUGHNESS OF HIGH HEAT INPUT WELDED ZONE

• Main Authors: AN, YOUNG HO, JEONG, HONG CHUL, PARK, YOUNG HWAN
• Format: Patent
• Language: English
• Published: 27.05.2008
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; METALLURGY; TREATMENT OF ALLOYS OR NON-FERROUS METALS

A welding joint comprising Fe, C, Si, Mn, Ni, Mo, Ti, B, 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 TiO oxide and TiO-TiN-MnS composite oxides. A 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, 0.005 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, N, B, Mn, and S satisfy 1.3<=Ti/O<=3.0, 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 TiO oxide and TiO-TiN-MnS composite oxides with a particle size of 0.01 to 0.1 mum distributed therein in the number of 1.0x10^7 to 4.6x10^8/mm^2 of the joint.