Abstract: The hook structure at the subsurface of low carbon steel and ultra-low carbon steel continuous casting slab was studied, the typical morphology of hook was obtained. The entrapment of bubbles and inclusions by hooks was observed, and the location relationship between oscillation marks and inclusions was obtained. The influence of different casting parameters on hook depth was compared through the experimental method and numerical simulation, and the regression formula was fitted to calculate the hook depth. It was found that types of hooks included whole leaf-like type, bent type, double-hook type and truncated type. The entrapment tendency of over 20 μm inclusions by hooks was larger. The depth of hooks was mainly below 3.0 mm from the surface of the continuous casting slab, and the increase of casting speed and casting superheat, the application of EMBr and the decrease of water flow rate in the mold could lead to the decrease of hook depth at the subsurface of continuous casting slab, which then improved the surface quality of the slab.

Key words: continuous casting slab；ultra-low carbon steel；hooks；inclusions；casting , parameters