Fracture toughness of the cast low alloyed CrNiMo bainitic steel

Enhanced demands on the traffic components operation require using new materials satisfying these specific requirements. The resistance against brittle fracture of cast bainitic steel is being assessed on the base of fracture toughness measurement at quasistatic loading in temperature range from -60 to +20 degreesC in this contribution. An attention is being paid to variability of mechanical characteristics quantification determined on the experimental castings of frogs from two melts and comparison of mechanical properties of bainitic steel with respect to mechanical properties of wrought rails made from pearlitic steel. At the same time the nature of higher level of fracture toughness of bainitic steel is explained when compared to the level of fracture toughness of steel with pearlitic structure. Critical fracture stress conception was applied for these purposes as a material characteristic indicating the resistance of given microstructure against the cleavage fracture initiation.