Autogenous fiber laser welding of 316L austenitic and 2304 lean duplex stainless steels

Abstract

This study presents results of experimental tests on quality of dissimilarwelded joints between 316L austenitic and 2304 lean duplex stainless steels, welded without ceramic backing. Fiber laser welded butt joints at a thickness of 8mmwere subjected to non-destructive testing (visual and penetrant), destructive testing (static tensile test, bending test, and microhardness measurements) and structure observations (macro-andmicroscopic examinations, SEM, element distribution characteristics, and ferrite contentmeasurements). Non-destructive tests andmetallographic examinations showed that thewelded joints meet the acceptance criteria for B level in accordance with EN ISO 13919-1 standard. Also the results of the destructive tests confirmed the high quality of the joints: specimens were fractured in base material with lower strength-316L austenitic stainless steel and a 180° bending angle was obtained confirming the high plasticity of the joints. Microscopic examination, SEMand EDS analysis showed the distribution of alloying elements in joints. The microhardness of the autogenous weld metal was higher by about 20 HV0.2 than that of the lean duplex steel. Ferrite content in the rootwas about 37% higher than in the face of the weld. The Schaeffler phase diagram was used to predict the phase composition of the welded joints and sufficient compliance with the magnetic method was found. The presented procedure can be used for welding of 316L-2304 stainless steels dissimilar welded joints of 8 mm thickness without ceramic backing.