轧后冷速对低碳贝氏体钢组织性能影响

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

模拟两阶段控轧控冷工艺,进行了低碳贝氏体钢轧制实验,分析了轧后快速水冷和空冷对低碳贝氏体钢组织及性能的影响。结果显示,钢轧后,在两种冷速下得到的组织形貌差别较大,快速水冷得到强度较高的板条贝氏体组织,缓冷得到强度较低的粒状贝氏体组织,粒状贝氏体的形成温度较高,没有明显板条特征;板条贝氏体屈服强度比粒状贝氏体高出278MPa,抗拉强度高出307MPa;而粒状贝氏体的塑性和韧性指标明显优于板条贝氏体,延伸率和-20℃低温冲击功指标是板条贝氏体的近3倍。

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 elon- gation rate and impact work at -20℃ are nearly 3 times to that of bainite ferrite.