Abstract: According to the nature of the periodic bending deformation of solid-liquid interface in the solidification process of continuous casting slab，The nucleation and extension of crack was analyzed by the variation of temperature gradient and dendritic spacing in the front edge of solid-liquid interface. The results indicate that the bending deformation of interface makes temperature field change in the front edge of solid-liquid interface; the occurrence of temperature gradient along drawing direction provides the condition for the growth of secondary dendrites; The crack source formed during the middle and final stage of solidification may extend to the surface of casting slab and become internal crack. The theoretical analysis is basically agreement with the experimental results.

Key words: continuous casting, dendritic spacing, internal crack