An unusual structure existing in the segregated position of the continuously casting plate or of the ingot steelmaking plate has been studied by metallurgical observations and EPMA analysis. The unusual structure is martensite or bainite transformed at low-temperatures. The occurrence of such transformed structure is closely related to the segregation of solute elements and mainly attributable to the segregation of manganese and phosphorus. The unusual structure consists of both martensite and bainite structure in the high strength steels of 50kg/mmmm2 tensile strength class containing high manganese contents, while only bainite structure in the steels of 40kg/mmmm2 class containing lower manganese contents. The appearance of this unusual structure has good relation to the segregated pattern obtained by micro-etching.
