Microstructure and Mechanical Properties of Simulated Heat-affected Zones of EP-823 Steel for ADS/LFR

EP-823 steel is one of the candidate materials for accelerator-driven systems/lead-cooled fast reactors (ADS/LFR). Its weldability was investigated by mechanical property tests and microstructure analysis on the enlarged heat-affected zones (HAZs) made by numerical and physical simulation. The finite element numerical simulation could simulate the welding thermal cycle of the characteristic regions in HAZs with extremely high accuracy. The physical simulation performed on a Gleeble simulator could enlarge the characteristic regions to easily investigate the relationship between the microstructure evolution and the mechanical properties of the HAZs. The results showed that the simulated partially normalized zone comprising tempered martensite, newly formed martensite and more tiny carbides has the highest impact energy. The fully normalized zone exhibits the highest hardness because of the quenched martensite and large carbides. The ductile property of the overheated zone is poor for the residual delta-ferrite phases and the quenched martensite.