The effect of cooling rate after rolling on the microstructure and properties of low carbon bainite steel

The rolling experiments of low carbon bainite steel are carried to simulate two-stage controlled rolling and controlled cooling process.The effects of accelerated cooling and air cooling after rolling on the microstructure and properties of low carbon bainite steel are analyzed.It is shown that there are different microstructures under two kinds of cooling rate of as rolled steel,and bainite ferrite microstructure obtained by accelerated cooling has higher strength than granular bainite microstructure after air cooling.Granular bainite has higher transformation temperature than lath bainite,and has not obvious lath characteristic.The yield strength of bainite ferrite is 278MPa higher than that of granular bainite,and the tensile strength of bainite ferrite is 307MPa higher than that of granular bainite.Meanwhile,granular bainite has outstanding ductility and toughness,and its elongation rate and impact work at -20℃ are nearly 3 times to that of bainite ferrite.