2018 年 104 巻 3 号 p. 145-154
Brittle crack arrest toughness in high strength steel plates with a thickness of 25 mm containing various amounts of C, Mn and Ni manufactured by several controlled-rolling (CR) conditions in a laboratory was investigated using ESSO tests to quantitatively clarify the metallurgical factors affecting arrest property. Arrest toughness of the steel plates was improved by low temperature and high reduction of CR. Optical and scanning electron microscopies revealed that arrest toughness correlates with the refinement of the effective grain size. The addition of Ni was confirmed to improve arrest toughness. Since grain refinement is not recognized in Ni bearing steels, it is attributed to the intrinsic effect of Ni, which is probably manifested as the increase in ductile fracture surface and randomness of crack propagation directions. Considering these effects, a simple equation predicting TKca4000 was derived by linearly combining the effects of the Ni content and the effective grain size.
