(Nb,Ti)C在轧后卷取中的析出及对铁素体相微观力学特征的影响  

PRECIPITATION BEHAVIOR OF(Nb, Ti)C IN COILING PROCESS AND ITS EFFECT ON MICRO-MECHANICAL CHARACTERISTICS OF FERRITE

作　　者：徐洋[1] 孙明雪[1] 周砚磊[1] 刘振宇[1] 

机构地区：[1]东北大学轧制技术及连轧自动化国家重点实验室,沈阳110819

出　　处：《金属学报》2015年第1期31-39,共9页Acta Metallurgica Sinica

基　　金：中央高校基本科研业务费专项资金项目N120807001和N110607006资助~~

摘　　要：以复合添加Nb和Ti的微合金钢为研究对象,采用热模拟、显微硬度、透射电镜以及纳米压痕技术等方法对实验钢在连续冷却条件下和卷取过程中的冷却速率对组织演变及显微硬度的影响进行观察和分析,研究了(Nb,Ti)C在卷取中的析出规律及其对铁素体相微观力学性能的影响.结果表明,连续冷却和卷取过程中的冷却速率的增加都能促进Nb-Ti实验钢从铁素体+珠光体组织向贝氏体组织转变,细化铁素体晶粒.在连续冷却条件下,实验钢的显微硬度随着冷却速率的增加逐渐升高,而在卷取过程中由于较小冷却速率能够促进(Nb,Ti)C在铁素体中的形核和长大使得铁素体中存在大量均匀弥散分布的纳米析出物,提高了基体的强度,因此随着卷取过程中冷却速率的增加实验钢的显微硬度呈现降低的趋势.Nb-Ti实验钢中铁素体相的纳米硬度为4.13 GPa,Young's模量为249.3 GPa,普通C-Si-Mn钢铁素体相的纳米硬度为2.64 GPa,Young's模量为237.4 GPa,纳米析出物对铁素体相的纳米硬度的贡献达到1.49 GPa.High strength micro-alloyed steel has been widely used in automobile and machines because of the remarkable high strength and forming property which are attributed to nano-precipitates and refinement of the organization. Since the nano-precipitates are mostly nucleated between austenite/ferrite transition and ferrite can significantly advance strength, it is important to investigate precipitate behavior in coiling process. Nanoindentation technology provides a chance to study the special influence of nano-precipitates on the micro-properties of ferrite. The effect of cooling rate during continuous cooling process and coiling process on microstructural evolution and micro-hardness of Nb-Ti micro-alloyed steel were studied by using the thermal mechanical simulator, micro-hardness instrument, TEM and nanoindentation instrument. The precipitate behaviors of（Nb,Ti）C in coiling process and its effect on nano-hardnesss of ferrite were discussed. Experiments results indicated that the increase of cooling rate in continuous cooling process and coiling process could promote the microstructure transition from ferrite and pearlite to bainite. The micro-hardness of the tested steel increased with the increase of cooling rate in continuous cool-ing process, and decreased with the cooling rate in coiling process because of the large number of the dispersive nano- precipitate in ferrite which could improve the strength of matrix. The smaller cooling rate could promote volume fraction of（Nb, Ti）C particles in ferrite because there was enough time for the nucleation and growth of（Nb,Ti）C precipitates. When the cooling rate in coiling process was 0.1 ℃/s, precipitates were dispersive in ferrite matrix with a diameter of less than 10 nm. The nanohardness and Young’s modulus of ferrite were 4.13 and 249.3 GPa for Nb-Ti micro-alloyed steel, 2.64 and 237.4 GPa for C-Si-Mn steel. The contribution of nano-precipitates to nanohardness of ferrite reached 1.49 GPa.

关 键 词：纳米析出物 冷却速率 纳米压痕 纳米硬度 Young’s模量 

分 类 号：TG142[一般工业技术—材料科学与工程]