MICROSTRUCTURE RESEARCH OF FERRITE-AUSTENITIC CR-NI-NB WELDING JOINTS CONTAINING SI
The results of research and modernization of steel type EP-302 (10Cr15Ni9Si3Nb1) and welding materials (electrode wire 03Cr14Ni8Si3Nb) are presented in this article. These materials assimilated in industrial applications and effectually used for facility production for atomic power plants with lead-bismuth coolant with operational temperature under 450°C. Investigated steels alloyed with Si, that is an effective way of heat resistance improving and resistance to attack by hot metal. We have done the microstructure research of ferrite-austenitic Cr-Ni-Nb welding joints containing silicon with a wide specter of SEM, TEM and X-ray phase analysis methods. The study of the content of ferrite phase is of special interest because of 2-5% limit that is one of the requirement for processibility improvement of semimanufactured material while welding. The transformation from delta ferrite to sigma-phase is discovered in joint metal in specimens after aging treatment at 500-600°C.