A Study of Ferritic Weld Deposits in Fe-9Ni Steel

Abstract

In 1977, research was initiated at the Lawrence Berkeley Laboratory to study the factors influencing low-temperature toughness levels in ferritic gas metal-arc (GMA) weldments of 9%-Ni steel. Commercial plates of this steel have yield and tensile strengths of 938 MPa (136 ksi) and 1172 MPa (170 ksi), respectively (Table I). GMAW consumables currently used for fabrication of 9%-Ni-steel low-temperature containment vessels are of the high-nickel-chrome or modified-austenitic types [^1–6], having yield strengths of 414 to 552 MPa (60 to 80 ksi) and tensile strengths of 621 to 828 MPa (90 to 120 ksi). From both an economic and design standpoint, a matching low-nickel ferritic weld wire would be a more acceptable filler metal. So far, attempts to produce a commercially acceptable ferritic GMAW wire have been unsuccessful [⁷]. This study evaluates different ferritic gas-shielded-arc filler wires in terms of their chemistry, microstructure, toughness properties, and fracture modes.

Work supported, in part, by the Office of Materials Science, Division of Basic Energy Sciences, U. S. Department of Energy.