Abstract
Manufactured by thermo-mechanical control process acclaimed as revolutionary for turning out the 50kgf/mm^2-class high-tensile steel, what is called TMCP type 50kgf/mm^2-class high-tensile steel has come to find prevalent applications as ship hull steel. This report reviews the results of a study the authors performed on fatigue strength of welded joints produced in the TMCP type 50kgf/mm^2-class high-tensile steel, which may be encapsulated as follows. (1) The S-N_f diagrams drawn for high heat-input butt-welded joints (with reinforcement weld) and fillet-welded joints produced in the TMCP type 50kgf/mm^2-class high-tensile steel show no differences, for practical purposes, from those obtained for the similar joints in the 50kgf/mm^2-class high-tensile steel manufactured by conventional rolling process. (2) Likewise, fatigue crack propagation taking place in HAZ of high heatinput butt-welded joints produced in the TMCP type 50kgf/mm^2-class high-tensile steel shows no differences in characteristics from that which takes place in HAZ of middle and high heat-input welded joints, of the 50kgf/mm^2-class high-tensile steel manufactured by conventional rolling process.
