Excellent high-strength liquid phase diffusion bonding joint and liquid phase diffusion bonding for high-strength steel, as well as the liquid phase diffusion bonding method to the toughness of the weld

摘要

PROBLEM TO BE SOLVED: To provide a steel material having the strength/toughness of 600 MPa in which the formation of intergranular ferrite or a ferritic phase in a solidified structure can be prevented, or the production of MnS in a final isothermally solidified position can be prevented, to provide a joint, and to provide a production method therefor.;SOLUTION: Regarding the high strength steel for liquid phase diffusion welding, the material to be welded for obtaining a liquid phase diffusion welded joint which does not comprise a ferritic phase or MnS having the diameter of the equivalent sphere of 5 m on grain boundaries or at the final isothermally solidified position in the isothermally solidified structure after liquid phase diffusion welding has a chemical composition comprising 0.30 to 0.60% C, 0.01 to 0.50% Si, 0.01 to 3.00% Mn, 0 to 4.0% Ni, 0 to 2.0% Cr, 0 to 0.70% Mo, 0 to 0.005% B, 0.0005 to 0.005% Ca and 0.001 to 0.010% N, and in which the contents of Mo, Cr, Mn and Ni are 10.0 expressed in terms of PS value decided by specified formula, or the ratio between ES value as the index of an active S content at the final isothermally solidified position in the liquid phase diffusion welding and the amount of Mn to be added is 50, and it has a tensile strength of 600 MPa.;COPYRIGHT: (C)2006,JPO&NCIPI