WELDED TRANSITION JOINT BETWEEN 2-1/4% Cr 1% Mo STEEL AND TYPE 316 STAINLESS STEEL. SODIUM COMPONENTS DESIGN PROJECT RESEARCH AND DEVELOPMENT PROGRAM-FINAL REPORT

Abstract

A steam generator, wherein the boiler, steam drum, and superheater are integrated into one single unit, requires the welding of a transition joint between the 2 1/4% Cr-1% Mo steel of the steam drum and the type 316 stainless steel of the superheater. A practicable procedure was developed for the welding of this transition joint and the properties of the weld were evaluated by mechanical testing and metallurgical evaluation. After evaluating the technical aspects of the project and their relation to the fabrication of the generator, it was considered desirable to overlay the welding edge of the 2 1/4% Cr-1% Mo steel with a suitable austenitic weld metul which would subsequently be welded to the type 316 stainless steel of the superheater. Austenitic stainless steel and high-nickel alloy weld metals were evaluated for the overlay; whereas only austenitic stainless steel weld metals were evaluated for the final weld joining the components. It was concluded that type 309 stainless steel weld metal deposited automatically by the submergedarc process is completely satisfactory for cladding the 2 1/4% Cr-1% Mo base metal and for making the final transition weld joining the steam drum and superheater sections of the generator. Supplementary mechanical tests, metallographic examinations, and hardness surveys further attested to the adequacy of the quality of the transition joint resulting from the procedures developed by this program. A detailed fabrication and thermal treatment specification is included for the welding of a transition joint between