Components of the Creep Strength of Welds

摘要

Modern power plant steels and welding alloys, designed to resist creep deformation at high temperatures, contain a myriad of alloying elements and a microstructure which has six or more phases. It has not therefore been possible to identify the precise role of each chemical and microstructural component in determining the ultimate creep properties. In this work, we have used a combination of models and a knowledge of the mechanical properties and microstructure, to factorise the long-term creep rupture strength into individual contributions, for example due to solution strengthening, precipitate strengthening etc. The factorisation is non-linear and relies on thermo-dynamic and mechanical property models. The work is general in the sense that it covers all c ommon ferritic steels and welding alloys of the type used in the construction of power plant. An assessment is included of some of the most modern alloys with interesting conclusions on the factors making major contributions to the long-term creep rupture strength.