Service Performance of Welded Duplex Stainless Steel Castings and Wrought Materials
Welding can impair the corrosion performance of both wrought and cast materials. It requires that the specifiers must consider the fabrication aspects of the materials and not just rely on published values for the base materials alone. The corrosion performance is most egregiously degraded by welding processes, which leave behind a fusion zone containing melted base material. This melted base metal zone, which is termed the “unmixed zone” in the filler metal added processes, is the region responsible for the degraded corrosion pitting resistance. Further, the phase balance in this zone is influenced by solidification and this phase balance must be restored either by heat treatment or by the selection of filler metals richer in austenite formers such as nickel and nitrogen. However, a paucity of data exists upon which the specifier/engineer can base service performance. Hence, there is the need for a more comprehensive study of the behavior of welded components.
The project will develop a suitable database to provide detailed fabrication and service performance guidelines including welding and heat treatment procedures for duplex stainless steel and wrought materials.
The database will enable the industry to reduce wastes resulting from improper fabrication and heat treatment methods, to reduce fabrication time due to undocumented fabrication procedures, and to improve service performance of components fabricated from duplex stainless steels, comparing to conventional materials.
It is expected that the following types of manufacturing plats are affected: oil refineries, ethylene furnaces, and reformer furnaces. There are 187 oil refineries in the U.S, and it is estimated that there are 450 ethylene furnaces, and 700 reformer furnaces in the U.S.