改良型CrMoV鍛鋼の多軸応力下における定量的クリープ損傷評価法

抄録

Recently, a modified CrMoV forging steel was developed with superior creep strength property by adding tungsten to conventional CrMoV forging steels. Generally, creep damage proceeds at stress concentration portion under multiaxial stress gradient. It is important to clarify creep rupture property and damage evolution process under the multiaxial stress states for the modified CrMoV forging steels. In this study, creep tests were conducted using plain and four kinds of circular notch specimens of the modified CrMoV forging steels. It was found that creep rupture times of the modified CrMoV forging steel are three times longer than those of the conventional one. Rupture times of the notch specimens of the modified one are longer as the tip radius decreases. The distribution tendency of creep void number density at the notch root sections corresponds to the distribution tendency of the maximum principal stress. The void growth simulation procedure was applied to predict creep damage. It was indicated that the initiation and growth of void under both uniaxial and multiaxial stress conditions quantitatively predicted by the void growth simulation.