Microstructure and Properties of T24 Homogeneous Welds

Abstract

The T24 heat resistant steel represents an advanced material for construction of membrane waterwalls in modern blocks of power plants. This low alloy steel has been originally developed for welding without both preheating and post weld heat treatment. However, weldments made of this steel can suffer from cracking. In the frame of this thesis a detailed characterization of microstructure, inclusive minor phase analysis, and microhardness of T24 homogeneous welds has been carried out. Investigations have been performed on samples in the as-welded state, after annealing 575 °C/ 10 hours and after annealing 740 °C/ 1 hour. Furthermore, impact energy of thermally simulated sample of the CG HAZ which was tempered 575 °C/10 hour, has been carried out. Experimental results prove the importance of post weld heat treatment for prevention of unacceptable hardening (above 350 HV1) of the CG HAZ in T24 homogeneous welds.