Abstract
The brittle crack arrestability is highly important in welded joints of heavy gauge steel plates used for large container ships. From the viewpoint of material design, it is possible to intentionally change the material properties of thick plates in the thickness direction. In this research, the brittle crack arrestability of thick steel plates with heterogeneous properties in the plate thickness direction were investigated in order to clarify the optimum distribution of properties in the thickness direction, which is necessary in the development of thick steel plates with excellent brittle crack arrestability. In the heavy gauge steel plate manufactured by lower temperature rolling, texture favorable for the arrstability was developed at the center of plate thickness (1/2t), and the brittle crack arrest position displays a split-nail shaped fracture surface morphology. When compared under identical Kca conditions, steel plate which has higher arrstability at the 1/2t position than at the 1/4t position, and display the split-nail fracture surface morphology, show higher brittle crack arrest performance under a condition of no temperature gradient, in which steel materials are actually used, than plates in which arrstability is lower at the 1/2t position than at the 1/4t position. The above-mentioned phenomenon can be explained approximately if the split-nail fracture surface morphology which is characteristic of steel plates with high arrstability at the center of thickness and the decrease in the stress intensity factor at the crack tip accompanying crack progress are considered.
