Solidification cracking in duplex stainless steel flux-cored arc welds Part 1—cracking in 30-mm-thick material welded under high restraint

Duplex stainless steels show fully ferritic solidification and are thus considered generally resistant to hot cracking. The few published cases where welds have been subject to solidification cracking could mostly be correlated to fairly high ferrite contents and an unfavorable weld shape. A recent literature review suggests that all welding methods can to some extent cause hot cracking and the risk increases in applications where heavy-wall material is welded under highly restrained conditions. This paper collects three cases where solidification cracking has occurred with duplex flux-cored wires in 30-mm-thick material welded under full restraint. Sidewall bend testing together with examination of fracture surfaces proved efficient to detect and inspect cracks. The hot cracks were observed in primary ferrite grain boundaries enveloped by austenite, but no clear correlation with the ferrite content could be found. Auger electron spectroscopy, light optical, scanning and transmission electron microscopy were used to characterize cracks. The fracture surface showed a clear transition of solidification mode from dendritic-flat to flat and particles were detected in the crack tip of the last solidified material. The weld metal chemical composition and source of raw materials were identified to affect the cracking susceptibility. The results indicate that the resistance may possibly be improved by optimization of the composition and slag concept.