Autogenous Fiber Laser Welding of 316L Austenitic and 2304 Lean Duplex Stainless Steels

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.

Weld Metal Microstructure Prediction in Laser Beam Welding of Austenitic Stainless Steel

“…Starting from the historical works of Schaeffler and DeLong, David et al [8] investigated the effects of cooling rate, Siewert et al [9] proposed a new ferrite diagram (WRC 1988) that shows, in the austenite/ferrite zone, the ferrite percentages, or ferrite number (FN); then the diagram was modified by Kotecki and Siewert [10] by the inclusion of the solidification mode boundaries (WRC 1992), obtaining a very useful tool to predict weld microstructure on the base of the grade of dilution. This kind of diagram is still attractive for phase evaluations based on the fused zone composition, especially in the case of dissimilar welds [11,12]. Other than composition, cooling rate [13] is a non-negligible parameter in determining the solidification modalities, which in turn results from the welding conditions.…”

Laser Dissimilar Welding of AISI 430F and AISI 304 Stainless Steels

“…In addition, dissimilar joining requires extensive technical knowledge, appropriate equipment and careful selection of consumables. However, these inconveniences and risks are taken due to the many benefits that arise from combining two very different materials, reducing both production and operating costs and the improving mechanical properties of the joints [ 16 , 17 ]. In order for such a joining to be carried out without unacceptable imperfections, it is necessary to thoroughly understand the technologies and weldability of materials.…”

Microstructure and Mechanical Properties of Nickel-Based Coatings Fabricated through Laser Additive Manufacturing

“…Comparing Figure 8b to Figure 8a, the microhardness of the substrate close to the HAZ decreases slightly because of Fe dilution [4]. The HAZ of laser cladding is very small, Landowski [37] found that the HAZ of laser welded 316L SS joint is about 20 µm. Therefore, the presence of HAZ has a very limited effect on the microhardness of the substrate.…”