押込み試験とAE法を用いた炭素鋼上の酸化スケールの破壊挙動の評価

抄録

The purpose of this study is to evaluate the fracture behavior and adhesion quality for an oxide scale on low carbon steel with different magnetite and ustyte structure. In this study, samples with different microstructure were prepared under different heat treatment conditions, and an indentation test was performed with AE technique on the oxide scale surface. Cracks were observed at outside of dent area (ring cracks) and in the oxide scale at center of dent area (vertical cracks). The vertical cracks propagated along the grain boundary between magnetite and ustyte. Delamination along the interface between the scale and substrate was also observed as AE signal was detected at last part of un-loading process. In order to estimate the stress distribution under the indentation testing, FEM was performed. Large tensile stress in radius direction was observed at both center and out-side of dent area during loading process. Vertical and ring cracks would be induced by those radius tensile stresses. Large tensile stress in thickness direction was observed at last part of un-loading process and would produce the delamination.