Investigation of the possibility of direct welding of X10CrMoVNb9-1 steel tubes with austenitic filler material without post-weld heat treatment

Abstract

The idea for this paper was motivated by a practical problem encountered during the replacement of a boiler reheater coils made of X10CrMoVNb9-1 steel tubes with dimensions 32x4mm. Specifically, welding this material requires post-weld heat treatment (PWHT). Welding the site joints between the header tube ends and the coil tube ends, within a confined space, presents a particular challenge because there are to many. This is more demanding when the welding sequence is not arbitrary but must be strictly followed. Under these conditions, post-weld heat treatment of every welded joint significantly complicates the reheater assembly procedure, and substantially extends the downtime required for job completion. Therefore, the study examines whether the joint could be made via direct welding, using austenitic filler material based on Ni, to avoid post-weld heat treatment, especially considering the small diameter and wall thickness used in the coil tubes.