超快冷工艺对超高强钢组织性能的影响

Effects of Ultra-fast Cooling on Properties and Microstructure of Ultra-high Strength Steel

研究了常规TMCP工艺和超快冷工艺对1 200 MPa级超高强钢的影响规律,通过光学显微镜、扫描电镜及透射电子显微镜等分析手段,研究分析了不同工艺的显微组织特征与力学性能的关系。结果表明,运用超快冷技术并合理控制开冷及终冷温度,能够获得强度和韧性指标达到1 200 MPa级别标准的钢板。性能提高的原因是微观组织的改变:晶粒明显细化并具有一系列亚结构,大量位错缠结使得抗拉强度提高;低碳含量使得韧性改善;钢中含有软硬相复合组织,保证了较低的屈强比;析出粒子更加细化,尺寸平均在10nm,析出弥散程度明显增大。

Effects of nomal TMCP and ultra-fast cooling technologies on properties and microstructure of ultra-high strength steel have been investigated.Microstructural characteristics and mechanical properties of different processes were investigated by means of optical microscopy,scanning electron microscope（SEM）and transmission electron microscope（ТЕМ）.Results indicate that the high strength and toughness of the tested steel can come up to 1200 MPa by way of ultra-fast cooling with optimization of start cooling temperature and finish cooling temperature.The cause of such improvement in mechanical properties of the test steel is correlated with changes in microstructure,i.e.ferrite grain refinement,a large number of subgrains and high dislocation density.The low carbon contents exhibited by test steel cause evident improvement in their toughness.Furthermore,the composite microstructure of soft phase and hard phase ensured the low yield ratio.Finally,carbonitride particles were obsiously refined,average size were 10 nm and distributed uniformly.