The influence of grain size on cleavage crack propagation resistance in ferritic steels

Abstract

Cleavage crack propagation in steels occurs suddenly and at high speed, and has a risk of giving structures crucial damage. Thus, it is a phenomenon to be prevented absolutely. It is well known that microstructures, for example grain size or orientation, make a substantial contribution to material resistance to cleavage fracture, but the effect of microstructures on mechanism of fracture is practically hardly elucidated at the present moment. This study firstly carried out arrest tests to evaluate the relation between cleavage crack propagation and grain size that was the most basic characteristic of microstructures, and experimented to describe the elementary process on the microscopic mechanism. The numerical analysis model was developed to express the results of these experiments, and showed that the larger grain size was, the larger cleavage crack propagation resistance was.