Effect of Austempering on the Structures and Performances of Cast High Carbon Si‐Mn Steel

The effects of austempering on the microstructures and mechanical performances of cast high carbon silicon and manganese steel (HCSMS) containing 1.0 wt.%C‐2.5 wt.%Si‐1.5 wt.%Mn‐1.0 wt.%Cr‐0.5 wt.%Cu were studied. The test results show a plate‐like morphology of bainitic ferrite. Each plate of the ferrite is surrounded by a thin layer of retained austenite when the austempering temperature is low, whereas large blocky areas of retained austenite are observed when the temperature is higher. The amount of retained austenite in the bainitic structure increases with increasing isothermal quenching temperature. Austempering results in a significant improvement in the mechanical performances of HCSMS. The main effect of the austempering temperature on the mechanical performances is that hardness and strength are decreased and elongation, impact toughness and fracture toughness are increased with increasing temperature. Cast HCSMS has excellent comprehensive mechanical performance when austenized at 593K.