The effect of electron beam welding on various properties of three austenitic stainless steels

Abstract

The influence of electron beam welding on various properties of semistable austenitic stainless steels: 304L, 316 (low nitrogen), and 21-6-9 were investigated. Tensile tests performed on transverse butt joints gave joint efficiences approaching 95% of theoretical efficiencies. The joint ductility for all steels, however, was 50 to 70% that of unwelded samples. Hardness testing revealed that the parent matrix was harder than the heat affected zone (HAZ) which in turn was harder than the fusion zone. Microstructural examination showed that the residual 11% cold-working had induced a partial martensitic transformation in the HAZ. The formation of (Fe, Cr)23(C, N)6 precipitate is responsible for the observed change in mechanical properties in the fusion zone. Electron microprobe analysis showed that a redistribution of the metallic elements (Ni, Cr, Mo) occurred in the fusion zone but that the nonmetals (P, S, Si) were relatively unaffected by the fusion process. Corrosion sensitivity tests showed that only the 304L steel was susceptible to corrosion cracking. Microstructural observations of failed surfaces of this steel reveal that fracture begins in a semi-brittle mode at the weld root and continues through the HAZ in a ductile manner.