| Abstract Scope |
Welding of creep strength enhanced ferritic (CSEF) steels like grade 91 can be a challenging procedure. A successful CSEF welding requires careful consideration on filler material selection, preheating and post weld heat treatment (PWHT), and using appropriate welding technique. The tensile and creep strength properties of these materials may be significantly degraded if the appropriate welding and heat treatment requirements are not followed per ASME Sec I PW-10. Furthermore, it becomes more sensitive when grade 91 material is welded to other materials like nickel alloys or stainless steels. The most important step in dissimilar welding is to select a filler metal that can withstand high operating temperature and having similar physical properties to the grade 91 at elevated temperature. Filler metal selection is based on operating temperature and the other part chemical composition in the joint. Dissimilar welding has to follow welding requirements of grade 91 as well as the other alloy. Heat treatments like post baking and PWHT is as important as welding. PWHT temperature and duration is a function of composition of both joining alloys. In any case the hardness of weldment and base metal has to be kept within the acceptable limit required for grade 91 material. In this presentation, welding, and post weld heat treatment of dissimilar weld between grade 91 and the most common alloys like Inconel X750 and austenitic Stainless steel will be discussed. |