Vliv nízkoteplotního žíhání na mikrostrukturu a vlastnosti homogenních svarů z oceli T24

Abstract

This master thesis aims to examine steels for membrane walls for modern fossil power plants. Special attention is paid to the steel T24 (7CrMoVTiB10-10) as this steel is the primary object of interest in the practical part of the thesis. Furthermore, there is a description and characterization of weldability and characterization of the structure of welded joints. The experimental part is focused on the characterization of the homogeneous weld of the T24 steel in the state after welding, annealing at 450°C/48 hours and after annealing at 450 °C/48 hours + 530 °C/10 hours. The examination is based on hardness and microhardness measurements, microstructure analysis and evaluation of internal stresses. In conclusion, it is shown that annealing of components at 450 °C is not sufficient to prevent significant precipitation hardening during the commissioning of components and does not lower internal stresses sufficiently. Results are indicating that secondary hardening can be an important factor in the formation of cracks in the homogeneous welds of T24 steel.