Effect of yttrium on the microstructures and inclusions of EH36 shipbuilding steel

The effects of yttrium content and cooling speeds on the microstructures and inclusions of EH36 shipbuilding steels were investigated, the evolutionary processes of microstructures and inclusions were investigated using optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results showed that adding trace amounts of yttrium could promote intragranular acicular ferrite (IAF) nucleation and refine the microstructures. The proportion of IAF first increased and then decreased with increasing yttrium content, and the optimal yttrium content to obtain microstructure of IAF was 0.01%. The appropriate cooling method was the steel mould cooling. The lattice disregistry between the α-ferrite phase and Y 2 O 2 S was 4.2%, which is very small. Y 2 O 2 S could effectively facilitate the nucleation of IAF. Moreover, the appropriate size of Y 2 O 2 S inducing IAF was approximately 1∼4 μm.