Vlastnosti a creepová odolnost svarových spojů nových typů austenitických žárupevných ocelí pro přehříváky USC bloků

Abstract

The present thesis deals with the actual topic that relates to new types of austenitic heat-resistant steels. Tubes of these steels are applied in the superheaters and reheaters of new USC power plants around the world. In this work there is analyzed the problem of phases precipitating in austenitic steels and their weldments with special attention to modern austenitic heat resistant steel makes SUPER 304H and HR3C. The thesis also summarizes methods of testing and evaluating of creep characteristics of the steels. The experimental work was focused on the evaluation of material properties including creep resistance of base material and weldment made of SUPER 304H steel in the as-received state and after post-weld heat treatment (PWHT). Evaluation of microstructure and microhardness profile was also performed for these samples before and after creep exposure. Creep properties of samples in both states (as-received and after PWHT) were evaluated by using parametric equations and the results of the base material and weldment were compared.