TECHNOLOGICAL FEATURES OF WELDING DISSIMILAR AUSTENITIC STEELS 12Х18Н10Т AND AISI 316 FOR PIPELINE SYSTEMS OF HIGH-TEMPERATURE INSTALLATIONS

Abstract

The paper considers the technological features of welding dissimilar austenitic corrosion-resistant steels 12Х18Н10Т and AISI 316 used in the equipment of a sodium loop facility being developed within the framework of the international SAIGA program for studies of advanced sodium-cooled fast nuclear reactors. It is shown that the operating conditions of the loop equipment, characterized by exposure to elevated temperatures, a chemically active liquid sodium environment, and radiation loads, impose increased requirements on the structural and phase state of welded joints. An analysis of the influence of the chemical composition of the base materials and filler metals on the weld metal structure was carried out using the Schaeffler diagram. The choice of ER316L filler wire is substantiated, as it обеспечивает the formation of a two-phase austenitic–ferritic structure with a controlled δ-ferrite content and a reduced tendency to hot cracking and intergranular corrosion. The temperature–time conditions of sensitization of austenitic steels are considered, and technological approaches to preventing intergranular corrosion in welded joints of sodium loop equipment are presented. The expediency of using TIG welding with controlled heat input and limited interpass temperature is demonstrated.