Stress and Temperature Dependence of Time to Rupture of Heat Resisting Steels

摘要

A new relation among the time to creep rupture, the stress and the temperature has been developed. Assuming the velocity of dislocations is controlled by a thermally activated process, the time to rupture, t_r is expressed as logt_r = ((Q-V_σ)/2.3RT)-C, where Q, V, σ, R, T, C are respectively the activation energy, the activation volume, the applied stress, the gas constant, the absolute temperature, and the Larson-Miller constant, i.e. abount 20. The new equation reads that the applied stress in linear function of the Larson-Miller parameter, P=T(logt_r + C). The new relation has been applied to the long term rupture data of several heat resisting steels obtained by National Research Institute for Metals. According to the equation the rupture data for each material can be classified into 2-4 groups where the deformation mechanism differs with each other. It has been found that for each group the data are excellently fitted to the equation.