分段冷却模式下热轧双相钢的组织演变及力学性能

通过热模拟实验研究了分段冷却模式下变形温度、保温温度及保温时间对Nb-Ti微合金热轧双相钢组织演变及性能的影响.结果表明:降低变形温度可促进铁素体的转变，使马氏体形态由大块状过渡到岛状；保温温度从740℃逐渐降至580℃时，铁素体转变量先增加后减少，保温温度为660℃时铁素体转变量达到峰值；随保温时间延长铁素体转变量增加，且铁素体转变量与时间的关系曲线呈“S”型.采用超快冷+空冷+层流冷的冷却模式并通过调整终轧温度及空冷时间获得了630~710MPa的热轧双相钢，屈强比≤061，相应的组织为铁素体+马氏体或铁素体+马氏体+少量的贝氏体.

Microstructure Evolution and Mechanical Properties of Hot-Rolled Dual Phase Steel with Stage Cooling Pattern

The effects of deformation temperature， holding temperature and holding time on microstructure evolution and properties of Nb Ti micro alloyed hot rolled dual phase steel were researched by the thermal simulation test. The results showed that the ferrite content rises and the martensite morphology evolutes from block to island with the decreased deformation temperature. While the holding temperature drops gradually from 740℃ to 580℃， the amount of ferrite transformation firstly increases and then decreases， and reaches the largest at 660℃. The relation curve between the amount of ferrite transformation and holding time presents “S” model. The hot rolled dual phase steel is obtained by using ultra fast cooling+air cooling+laminar cooling mode， and adjusting the finish rolling temperature and air cooling time. The tensile strength is ranging between 630 and 710MPa， and yield ratio is less than or equal to 061. The microstructure of the steel is the mixture of ferrite and martensite or ferrite， martensite and a small amount of bainite.