The development of high heat input welded EH40 ship steel plate

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The development of high heat input welded EH40 ship steel plate

Huang, Ching-Yuan / Chiu, Fon-Jen / Yang, Jer-Ren

Large thickness, high strength with excellent low temperature toughness EH40 steel plates are applied to construct 8000 TEU container ship. In order to improve the construction efficiency of the huge ship, the high heat-input welding process was developed. In China Steel Corporation, a new grade of EH40 ship steel plate is developed to accommodate the requirement of the high heat-input welding. In this steel plate, the particle size and distribution of TiN are further controlled by adjusting Ti/N ratio. These stable TiN particles can prevent the abnormal growth of the austenite grains on high temperature in the heat affected zone during the process of welding. Boron is added to catch free nitrogen and promote the acicular ferrite transformation in the coarsened region. This newly developed steel has a very narrow coarsened grain zone with the microstructure of acicular ferrite. Therefore, this newly developed steel has excellent low temperature toughness compared with the traditional steel after high heat input welding. This steel plate can be used for single pass high heat welding during ship construction.