Development of Offshore Steel for High Heat Input Welding
To reduce the construction cost and period of steel structure, high-efficiency welding methods applying high heat input have been widely employed. However, deterioration of the strength and toughness, especially low-temperature impact toughness, due to the coarse grains in the heat-affected zone (HAZ) of weld steels often comes along with high heat input welding. Thick offshore steel has been developed by Ti deoxidization for the use of high heat input welding. The inclusions of the steel were analysed by EPMA and SEM, and the major inclusions were identified to be Al2O3-(MgO) and Al2O3-CaO-(TiO2) types. The steel plates with different thickness over 40 mm were welded with heat input over 100 kJ/cm, and Charpy impact energies of the welding joints at −40 °C were over 75 J. The nano-sized TiN particles in HAZ were observed and were considered to retard the grain coarsening in the HAZ during high heat input welding.
KeywordsOffshore steel High heat input welding Heat-affected zone Inclusions
The authors would like to thank the financial support from HBIS Group through HBIS-UQ Innovation Centre for Sustainable Steel. The authors acknowledge the facilities, and the scientific and technical assistance, of the Australian Microscopy & Microanalysis Research Facility at the Centre for Microscopy and Microanalysis, The University of Queensland.
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