开冷温度对热轧F/B双相钢组织性能的影响

采用轧后空冷+超快速冷却的方式，研究了开冷温度对热轧铁素体/贝氏体(F/B)双相钢组织性能的影响。结果表明：开冷温度显著影响F/B双相钢的显微组织和性能。开冷温度由747 ℃降至700 ℃时，铁素体体积分数由17.3%增至85.7%，铁素体晶粒尺寸由3.3 μm粗化至3.6 μm，贝氏体中析出的碳化物含量增加。同时，F/B双相钢的屈服强度从594 MPa降至475 MPa，抗拉强度从648 MPa降至532 MPa，伸长率从17.7%升至34.3%，扩孔率从36.4%提高至82.8%。因此，为实现热轧F/B双相钢力学性能和扩孔性能的平衡，开冷温度应控制在730~700 ℃。

Effects of start cooling temperature on microstructure and mechanical properties of hot- rolled ferrite/bainite dual- phase steels

The process of air- cooling followed by ultra fast cooling after hot- rolled was used to investigate the effects of start cooling temperature (SCT) on the microstructure and mechanical properties of a hot- rolled ferrite/bainite (F/B) dual- phase steel. The results showed that the microstructure and properties of the F/B dual phase steels were influenced by SCT obviously. The volume fraction of ferrite phase was increased from 17.3% to 85.7% , the grain size of ferrite size was increased from 3.3 μm to 3.6 μm and the precipitated carbide in bainite was also increased with the SCT decrease from 747 ℃ to 700 ℃. At the same time, lowering SCT from 747 ℃ to 700 ℃ , the yield strength of this steel was reduced down to 475 MPa from 594 MPa, the tensile strength down to 532 MPa from 648 MPa , the elongation up to 34.3% from 17.7% and the hole expansion ratio up to 82.8% from 36.4%, respectively. So, the start cooling temperature should be in 730-700 ℃ to balance the strength and the deformation properties of the hot- rolled F/B dual phase steels.