Microstructure of welded austenitic stainless steel after annealing at 900°C

Abstract

In this work the results of microstructure analysis for welded sheet from austenitic stainless steel AISI 316L before and after annealing at 900 °C/2 hours are shown. Steel sheet dimensions 500x200x15 mm is prepared in the form of V-join. The welding was carried out with shielded metal arc welding (SMAW) technique. For welding was used rutile electrode Böhler FOX SAS-4A. Analysis of weld joint microstructure consisted of a microscopic examination, phase identification and a measurement of the ferrite content using a ferritoscope. Microscopic examination was performed with optical and scanning electron microscopy (equipped with energy dispersive spectroscopy- DS). For the phase identification of microstructural constituents the XRD analysis was used. Before annealing the microstructure of the base material consisted of 96.6% austenite and 3.4% ferrite, while ferrite content in weld metal was 14.3%. The ferrite content decreased after annealing at 900 °C. After annealing, the content of ferrite in base material was 0.7 (decomposition ratio 79.4%) while in weld metal was 0.5 (decomposition ratio 96.5%). After annealing at 900 °C in the microstructure of weld metal was observed the sigma phase particles. The EDS analysis showed that sigma phase particles consist of 22.72 %Cr, 66.65 % Fe, 7.45 %Ni, 2.22 % Mo and 0.96 % Mn.