Abstract
Allowable tensile stress at the elevated temperatures used for design of high temperature structural components is determined based on a long-term creep strength, such as 100,000 hours creep rupture strength. Aim of the Creep Data Sheet project conducted in National Research Institute for Metals and National Institute for Materials Science is to obtain long-term creep strength data of engineering creep resistant steels and alloys. A time-temperature parameter method is applied for creep rupture life prediction, and several parameters are proposed. A wide variety of equations are examined to describe and to predict a long-term creep deformation behavior. Creep strength of ferritic creep resistant steels after very long-term exposure at the elevated temperatures is controlled by an inherent creep strength that is almost the same independent of chemical composition, heat treatment, initial microstructure and short-term creep strength. A region splitting analysis method was proposed as accurate life prediction method of ferritic creep resistant steels by consideration of 50% of 0.2% offset yield stress. Allowable tensile stress of some ferritic steels was revised according to reevaluation of long-term creep strength by means of region splitting analysis method.
