Hypereutectoid cementite morphology and mechanical properties of Cr-Ni-Mo cast steel

Purpose: The paper presents evaluation of the influence of grain normalization (refinement as a result of repeated austenitizing), cooling rate after repeated austenitizing on the morphology of hypereutectoid cementite and fracture toughness of G200CrMoNi4-6-3 cast steel. Moreover, the elimination of hypereutectoid cementite in structure of Widmannstätten type precipitates from the structure of investigated cast steel has been undertaken. Design/methodology/approach: Basic research of G200CrMoNi4-6-3 cast steel included metallographic analysis and fracture toughness research (impact strength, stress intensity factor KIc). The heat treatment has been planned on the basis of CCT diagram prepared for that cast steel. Findings: Heat treatment of investigated cast steel allows to refine the grain and eliminate from it’s structure the hypereutectoid cementite in structure of Widmannstätten type. At very low cooling rate the precipitates of hypereutectoid cementite become partially coagulated. The study of the influence of cooling rate on the mechanical properties of G200CrMoNi4-6-3 cast steel had proven that elimination of hypereutectoid cementite in structure of Widmannstätten type from the investigated cast steel structure to small degree increases it’s fracture toughness. Research limitations/implications: Research financed by the Ministry of Scientific Research and Information Technology, grant No. 3 T08B 057 29. Practical implications: G200CrMoNi4-6-3 cast steel of ledeburite class is used mainly for rolls production. Any data related to the structure and mechanical properties of that cast steel are precious for the manufacturers and users of the mill rolls. Originality/value: The new heat treatment of G200CrMoNi4-6-3 cast steel.