Effects of thermomechanical processing on microstructure and properties of bainitic work hardening steel

The thermomechanical processing (TMP) of a bainitic work hardening steel was carried out on a Gleeble3500 simulator. The microstructure of processed specimens was investigated by means of optical and electron microscopy, and tensile tests were performed in a ZwickRoell tensile tester. The deformation temperatures of austenite varied from 800 °C to 900 °C. The cooling methods include single rate cooling method and two-stage cooling method. The two-stage cooling method includes fast cooling rates ranging from 4 °C/s to 12 °C/s and slow cooling rates ranging from 1 °C/s to 2 °C/s. It is shown that, within the range of parameters tested, the obtained microstructures are granular bainite, the tensile strength of the steel can be adjusted from 897.8 MPa to 1083.2 MPa, and good plasticity can be obtained at different strength levels.