Development of an Improved Stainless Steel to Ferritic Steel Transition Joint

Abstract

The objective of this study was to develop an improved transition weld joint between stainless steel and ferritic steel piping to circumvent the failures and concerns with joints made by existing technology. The primary concern of mismatch in coefficients of thermal expansion between the ferritic and austenitic steels and the high stresses that it imposes at the interface between ferritic steel and weld metal led to an extensive elastic stress analysis involving base metal combinations, filler metals, and weld joint geometries. This analysis indicated that, for pipe welds, joint stress could be reduced considerably by using a transition material with an intermediate coefficient of thermal expansion between the 2 1/4 Cr-1 Mo ferritic steel and the austenitic stainless steel. Alloy 800H was selected as an appropriate intermediate material for this application.