Abstract
This study presents results of experimental tests on quality of dissimilar welded joints between 316L austenitic and 2304 lean duplex stainless steels, welded without ceramic backing. Fiber laser welded butt joints at a thickness of 8 mm were subjected to non-destructive testing (visual and penetrant), destructive testing (static tensile test, bending test, and microhardness measurements) and structure observations (macro- and microscopic examinations, SEM, element distribution characteristics, and ferrite content measurements). Non-destructive tests and metallographic examinations showed that the welded 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, SEM and 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 root was 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.
Highlights
Lasers as a heat source have been widely applied in industrial processes [1,2]
Tests showed that no structural changes reducing mechanical properties occurred under the influence of the laser welding thermal cycle
Examined welded penetration was achieved for investigated welded joints without changing beam focusing position
Summary
Lasers as a heat source have been widely applied in industrial processes [1,2]. Currently, they are used for welding, cutting, remelting, and various processes with surface modification of materials [3,4,5,6]. Duplex ferritic-austenitic steels are becoming increasingly popular due to their specific properties They combine the advantages of other groups of high-alloy steels and the most important of them are high strength with good plasticity and corrosion resistance [25,26,27]. Compared to austenitic stainless steels, they have higher strength parameters besides plasticity and higher resistance to stress corrosion Steels from this group are characterized by good weldability, provided that the technological regime is maintained: the control of the value of heat input, the use of appropriate welding consumables dedicated to welded grade, the dilution rate, the suitable dimensions of the welding groove, the use of the appropriate type of shielding gas on the face and root side, maintaining high purity of welded components and other [29,30,31]. The present work aims to show the ability of making 316L austenitic stainless steel–2304 lean duplex stainless steel dissimilar joints using the autogenous fiber laser welding process
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