The effects of multiple repair welds on a quenched and tempered steel for naval vessels

Significant cost and time savings may be realised if multiple weld repairs are undertaken at the same location during the long-term maintenance of naval vessels. Consequently, this investigation simulates full-thickness hull welds, which are required to facilitate the removal and subsequent replacem...

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Bibliographic Details
Published in:	Welding in the world Vol. 65; no. 10; pp. 1997 - 2012
Main Authors:	Carpenter, Kristin R., Dissanayaka, Pragathi, Sterjovski, Zoran, Li, Huijun, Donato, Joe, Gazder, Azdiar A., van Duin, Stephen, Miller, Dan, Johansson, Mikael
Format:	Journal Article
Language:	English
Published:	Berlin/Heidelberg Springer Berlin Heidelberg 01-10-2021 Springer Nature B.V
Subjects:	Chemistry and Materials Science Crack initiation Electron backscatter diffraction Fracture mechanics Grain boundaries Heat affected zone Heat treating Impact strength Impact tests Materials Science Metallic Materials Metallography Microstructure Naval vessels Quenching and tempering Repair welding Research Paper Simulation Solid Mechanics Steel Tear tests Theoretical and Applied Mechanics Transformation temperature Martensite-austenite constituent Prior austenite grain size Charpy impact toughness Quenched and tempered steel Intercritical heat-affected zone Thermal simulation
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Summary:	Significant cost and time savings may be realised if multiple weld repairs are undertaken at the same location during the long-term maintenance of naval vessels. Consequently, this investigation simulates full-thickness hull welds, which are required to facilitate the removal and subsequent replacement of hull sections, by assessing the effects of 4 reoccurring weld repairs on a propriety quenched and tempered steel used for naval applications. Optical metallography, electron backscattering diffraction (EBSD), hardness maps, Charpy impact, and dynamic tear tests were conducted. A combination of real weld repairs and Gleeble heat-affected zone (HAZ) simulations were undertaken to characterise the effects of repeated thermal cycles on the microstructure and toughness of different sub-HAZ regions. When the intercritical reheat temperature was just above the A C1 lower critical transformation temperature, the impact toughness was substantially reduced. This includes the fine-grained HAZ where high toughness is typically expected. The low toughness was attributed to the promotion of fracture initiation via debonding between the matrix and second phase which formed at prior austenite grain boundaries. Compared to the original toughness, the application of multiple repeat welds or multiple simulations of the same sub-HAZ thermal cycle did not deteriorate toughness nor noticeably alter the final microstructure.
ISSN:	0043-2288 1878-6669
DOI:	10.1007/s40194-021-01150-y