Abstract: To understand the reasons behind edge cracks of large-scale cast ingot during hot deformation, this paper compared the compositions, phase ratios at different temperatures, and differences in the hardness of two phases in the middle and edges of cast ingots. The microstructure and fracture morphology of the samples were observed by optical microscopy, scanning electron microscopy, and electron back-scattered diffraction. The results indicate the presence of smaller grains and larger ferrite content in the edge portion than in the middle. However, edge cracking is also more serious than middle cracking, which indicates that grain size and phase proportion are not the main factors influencing the side cracking of ingots. Compared with that of the middle portion, the hardness difference between the two phases of the ingot edge is larger. Thus, the strain distribution of the two phases varies during hot deformation, and stress concentration occurs along the phase boundary. More precipitates are observed in the phase boundary of the ingot edge than in that of the middle specimens, and these precipitates are believed to destroy the continuity of the matrix, leading to microcracks.