Microstructure and Mechanical Properties of an Underwater Wet Welded Dissimilar Ferritic/Austenitic Steel Joint

Abstract

EH40 ship steel was underwater wet-welded by shielded metal-arc welding at a depth of 7 m in the open sea, using austenitic electrodes. The microstructure and mechanical properties of the joint were estimated with microhardness measurements, bending and tensile testing, optical microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The highest microhardness was recorded on the coarse-grained heat-affected zone of the base metal, which displayed a mixed bainite-martensite microstructure, while the welds possessed a fully columnar dendritic austenitic structure. The specimens exhibited higher ultimate strength and elongation in longitudinal tensile tests than in transverse ones. Moreover, the specimens satisfied face bending tests but failed in root bending ones. Hydrogen-induced microcracks, which were observed in a lath martensite layer at the fusion boundary, became the fracture initiation region both in bending and transverse tensile tests.

Control of the diffusible hydrogen content in different steel phases through the targeted use of different welding consumables in underwater wet welding

“…Besides the strategy to use induction technology to provide a heat treatment, [22][23][24] and alteration of the stick electrode's cover, [7,25,26] the use of austenite-forming welding consumables was examined. [27][28][29][30][31] The solubility of hydrogen is significantly greater in the face-centered cubic austenitic phase than in the body-centered cubic lattice of the ferritic phase. [32] At the same time, the diffusion rate of hydrogen in austenitic iron is significantly reduced as compared with ferritic iron [32] (Figure 1).…”

Fracture Assessment of the Weld–Base Metal Interface of High-Strength Steel Weld Joint

“…High-strength steel structure is composed of the components by welding to connect, which plays a structural function. Nevertheless, for large welded structure, the weld joint is found to be weak location from the previous studies owing to the highly heterogeneous material microstructure nature and physical properties (e.g., mechanical, thermal and fracture properties) across the weld joint [4,5]. Moreover, defects like welding gas pores, impurities and residual stresses will be brought into inevitably during the welding process, which significantly cause the stress concentration in the weld joints [6,7].…”

Ocena przydatności komercyjnych elektrod otulonych do spawania mokrego pod wodą z wykorzystaniem analizy skupień

“…Do spawania mokrego pod wodą stali wykorzystuje się elektrody ferrytyczne oraz austenityczne o otulinie rutylowej albo (znacznie rzadziej) utleniającej [2,4,6,10]. Wynika to z lepszej stabilności jarzenia się łuku niż przy zastosowaniu elektrod zasadowych [11].…”