高强贝氏体非调质钢的奥氏体连续冷却相变

Continuous cooling transformation of austenite for high strength bainitic non-quenched and tempered steel

采用DIL805L热膨胀仪,研究了Si-Mn-Mo系贝氏体非调质钢奥氏体连续冷却转变过程(CCT曲线),分析其显微组织及硬度、强度的变化。结果表明,试验钢在小于7℃/s较宽冷速范围内均可获得贝氏体+铁素体组织,且贝氏体以粒状贝氏体+板条贝氏体2种形态存在。随着冷却速度增加,显微组织逐渐转变为以马氏体为主,同时晶粒细化作用增强,硬度及抗拉强度增加。可以通过对转变组织的控制,得到综合力学性能良好的贝氏体钢。

Continuous cooling transformation curves( CCT) of a Si-Mn-Mo bainitic non-quenched and tempered steel were studied on a DIL805 L thermal dilatometer. The evolution of microstructure,hardness and intensity was analyzed. The result shows that bainite and ferrite can be both obtained when the cooling rate is under 7 ℃/s,and the bainite is composed of granular bainite + lath bainite. As the cooling rate increasing,the microstructure is changed to martensite mainly,and the grain refinement effect is enhanced,which makes the hardness and tensile strength increase. Thus,bainite steel with good comprehensive mechanical properties can be obtained by controlling the microstructure transformation.