Creep-rupture properties and microstructure of AISI type 316L submerged arc weld metals

Abstract

A series of submerged-arc butt welds has been produced in AISI type 316L steel plate using different commercial consumables. These consumables produce only small changes in the as-deposited analyses, but significant differences in the δ-ferrite content. The stress rupture, minimum creep rate, and creep ductility of these welds have been measured at 600°C and stress levels between 170 and 240 M N m⁻². The creep-rupture values were comparable with those for manual metal arc welds, and fall within the lower limits of the scatter observed for wrought materials. The proportion of δ-ferrite was found to have little influence on creep ductility, with the exception of the weld containing 20% which consistently showed lower ductility. The nature and extent of the δ-ferrite transformation on aging at 600°C varied between the weld metals, but generally followed the sequence δ-ferrite → M₂₃ C₆ → intermetallic σ- and χ-phases.