Strength and structure of heat resisting steels at high temperatures

The heat resistant steel is a structural material for the high temperature of thermal power generation etc. As mechanical property for the heat resistant steel, high temperature strength should be high, and the rupture time be long. But, the structure of the steel remarkably change during long time creep deformation because diffusion easily occurs at the high temperature. Therefore, it is necessary to control the structural change during creep deformation to maintain strength for a long time at the high temperature. In this paper, at first the origin of high temperature strength of the heat resistant steel is described in view point of high-temperature deformation mechanism. Next, the grain boundaries in martensitic structure which are the fundamental structure of the heat resistant steel is described, and the change of these boundaries during creep deformation is described. The structure control of a further making of the heat resisting steel to high strength is described by using these findings.