终轧温度对Ti-V-Mo复合微合金钢组织演变和硬度的影响

采用Gleeble3800热模拟试验机、OM、EBSD、TEM及Vickers硬度计等研究终轧温度对Ti-V-Mo复合微合金钢的组织转变、析出相和硬度的影响,并阐明了组织演变和硬度变化的原因。结果表明,不同终轧温度的Ti-V-Mo钢其组织均为多边形铁素体;随着终轧温度由1000℃降低到800℃,Ti-V-Mo钢的硬度由400HV提高到427HV;铁素体晶粒的平均尺寸由3.44μm减小到3.05μm;(Ti, V, Mo)C粒子的析出数量增加,其平均尺寸由8.38 nm减小到6.25 nm。随着终轧温度的降低,铁素体平均晶粒尺寸的减小和纳米级(Ti, V, Mo)C粒子的增多及细化是硬度增大的主要因素。在980℃以下,降低终轧温度(Ti, V, Mo)C在奥氏体中的形核率不断减小,使得其在铁素体中析出的10 nm以下的(Ti, V, Mo)C粒子不断增多,促进了硬度的提高。

Effect of Finish Rolling Temperature on Microstructure Evolution and Hardness of Ti-V-Mo Complex Microalloyed Steel

The effect of finish rolling temperature on microstructure, precipitates, hardness of Ti-V-Mo microalloyed steel was investigated by means of Gleeble3800 thermal-mechanical simulator, OM, SEM, TEM and Vickers-hardness tester. The results show that the microstructures of Ti-V-Mo microalloyed steel, which was finish-rolled at different temperatures, consist of all polygonal ferrite, and the finish rolling temperature has a major impact on the precipitates and hardness. When the finish rolling temperature decreases from 1000^oC to 800^oC, the hardness increases from 400 HV to 427 HV. Meanwhile, the average grain size of ferrite in Ti-V-Mo microalloyed steel decreases gradually from 3.44 μm to 3.05 μm and the amount of (Ti, V, Mo)C particles increase monotonously, while their mean size reduces from 8.38 nm to 6.25 nm. The main factors responsible to the enhancement of hardness are the refinement of average ferrite grain size as well as the increasing amount and further refinement of nano-sized (Ti, V, Mo)C particles as the finish rolling temperature decreases. The nucleation rate of (Ti, V, Mo)C carbides in austenite decreased when the finish rolling temperature below 980^oC, while more tiny particles precipitated from ferrite matrix, which promotes the increase of hardness.