Assistance prof. of Metallurgy, Islamic Azad University-Karaj Branch, Karaj, Iran
The proportional relationships between the Charpy absorbed energy (CVN) and the KIC values have been established for a wide variety of steels. Several formulae have been proposed that predict KIC from CVN. The purpose of this study is to investigate, by means of compact testing fracture toughness specimens, the effective role of microstructure for estimation of the fracture toughness (KIC) of rotor steel using Charpy absorbed energy (CVN). To achieve this objective, a number of rotor steel samples were heat treated by step quenching procedure, and the fracture toughness and impact energy were measured. It was found that the calculated fracture toughness values, which were derived using a developed CVN-KIC relationship, disagreed with the experimental results.