Optimization of Mechanical Properties of Low Carbon Bainitic Steel Using TMCP and Accelerated Cooling

The recent increased severity in service conditions, such as frequent earthquakes, have further promoted the development of steel production technologies for many types of microstructural control. In the present paper, two-stage thermomechanical control process (TMCP) combined with accelerated cooling was employed to control the microstructural evolution and to study the microstructure-property relationship of low carbon bainitic steel. The main microstructure of hot rolled steel plates changed from granular bainite to lath bainite (or bainitic ferrite) when the final accelerated cooling temperature decreased from about 530 to 430 °C, accompanied with a notable increase in yield strength at the expense of slightly decreasing toughness. The strengthening mechanism was mainly attributed to dislocation strengthening and precipitation strengthening for this low carbon microalloyed steel. In addition, if the strain hardening exponent of hot rolled steel plate with the thickness of 13 mm is expected to be higher than 0.1, the final cooling temperature range should be maintained above 500 °C.