The steam explosion accidents frequently occur in the metallurgical industry, causing significant personal injury and property damage. In this paper, the experiments on the interaction of a molten copper column with water were carried out under different temperatures and masses of the molten copper column. Five fragmentation phenomena of the copper column can be observed. The fragmentation probability is significantly large when the temperature of molten copper falls in the range of 1200-1400 degrees C. As the mass of molten copper increases, the fragmentation probability of the copper column in water decreases, while the fragmentation probability at the vessel bottom increases. Two fragmentation models are proposed based upon the morphological structures of molten copper and fluid instability. The instability is the main reason for the fragmentation of the copper column with the streamline structure, while the rapid evaporation of cooling water inside the concave structure is the dominant mechanism for the fragmentation of a copper column with a concave structure.