Experimental Determination of the S-N Diagrams of Butt Welded Joints of Austenitic AISI 316 L Stainless Steel

Kleber Eduardo Bianchi¹; Fabio Brongar Milech¹

¹ Federal University of Rio Grande

doi:10.20906/CPS/COB-2015-1564

Resumo

Nowadays, the use of stainless steels as base metal of engineering structures is increasing, because of the availability in the market of easy-to-find alloys, which combine good weldability, mechanical strength and oxidation resistance. The critical spots of these structures usually are the joints and the main failure mechanism is fatigue. In the case of welded joints, the methodology of assessment is a matter of great concern to the designer, because these joints are sites of defects and high residual stresses, emerged from the welding process itself. The present study aimed to obtain the S-N fatigue curves of a butt welded joint under transversal loading, adopting specimens made of AISI 316L austenitic stainless steel, which were divided in three different groups: a) specimens with raw weld beads - no machining of bead reinforcement; b) specimens with machined weld beads in order to remove the face and root reinforcements, and c) specimens for base metal evaluation (no weld). Subsequently, the results were compared with data taken from Eurocode and American Welding Society Standards: Eurocode 3 - part 1.9 (2003) and AWS D1.1 (2010), as well as the Recommendations of IIW (International Institute of Welding) (HOBBACHER, 2008). In this context, plates of AISI 316 L stainless steel with a thickness of 6 mm were robot welded in a single pass, with bead transversal to rolling direction, and subsequently machined to give the final shape to the specimens. Metallographic and tensile tests were conducted to evaluate the weld joint quality. No significant defects were found and the mechanical strength of welded specimens was superior to that of base metal specimens. After that, the specimens were tested using cyclic loads in a servo hydraulic machine, in order to obtain the S-N diagrams. For the three tested groups of specimens, the fatigue life exceeded the values suggested by the cited standard guidelines and recommendations in cases of medium or low stress range values. However, when the specimens were subjected to hig

Palavras-chave: Welded Joints; Fatigue; Stainless steel AISI316L