Microstructure and Mechanical Properties of Cast and Hot-Rolled Medium-Carbon Steels under Isothermal Heat-Treatment Conditions

In this study, the changes in microstructure and mechanical properties during isothermal heat treatment of cast steel before after hot deformation were investigated using medium-carbon with low alloy content. The microstructural characteristics hot-rolled under heat-treatment conditions examined optical microscopy scanning electron conjunction backscatter diffraction. variation was evaluated Rockwell hardness tensile tests. After maintaining an austenitizing condition at 1200 °C for 30 min, performed range 350–500 °C, followed by rapid cooling water. Both did not completely transform into bainitic ferrite treatment. partially untransformed a mixture martensite acicular ferrite. At 500 prior austenite phase changed to Widmanstätten pearlite. 450 cementite coarsened coalescence subsequent diffusive growth. increased as temperature decreased, generally higher than that steel. Hardness strength showed similar trends, overall tend decrease increases, but there are slight differences depending on complex factors such various fractions grain size.