遅れ破壊特性の異なる高強度マルテンサイト鋼のAFM組織解析

概要

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Tempered martensitic microstructures were quantitatively evaluated by AFM and delayed fracture properties were obtained for an induction-heating-quenched and induction-heating-tempered (IHT) specimen and an induction-heating-quenched and furnace-heating-tempered (FHT) specimen of prestressed steel (mass\% of 0.36 C, 1.63 Si and 0.72 Mn). The strength levels of both specimens were controlled so that the tensile strength was 1470 MPa. The critical diffusible hydrogen content for delayed fracture was 0.4 and 0.1 mass ppm for the IHT and FHT specimens, respectively. Cementite particles were smaller in the IHT specimen than in the FHT specimen, particularly on prior austenite ($\gamma$) grain boundaries. These results demonstrate that delayed fracture property is correlated with cementite particle size on prior $\gamma$ grain boundaries.
九州大学の論文