Structure characteristic of subsurface hooks in continuous cast LCAK steel head slabs

The characteristics of subsurface hooks in continuous cast LCAK steel head slabs were investigated.The results show that the hook characteristics have significant correlations with each other,e.g.the mean hook length,thickness and depth increase with the rise of hook angle.The hook characteristics increase when the oscillation mark depth increases and the casting speed decreases.With the increase of casting length,the mean hook length,depth and thickness decrease,and when the casting length exceeds 7.9 m the hook characteristics remain stable.However the mold heat extraction has a reverse trend,thus with the increase of heat extraction the hooks become shorter.Finally a hook formation mechanism was proposed.It is suggested that meniscus freezing occurred during two stages,the late stage of the positive strip period and the earlier stage of the negative strip period.The mechanism could explain the phenomena that the hook root deviates from the valley of the oscillation mark,and then the main factors affecting hook characteristics were discussed.