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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.
The micro-alloyed steel with Nb and Ti added as the research object, the microstructure evolution of the experimental steel under the condition of continuous cooling and coiling was studied by means of thermal simulation, microhardness, transmission electron microscopy and nanoindentation technology (Nb, Ti) C during coiling and its effect on the micro-mechanical properties of the ferrite phase were investigated.The results show that during the continuous cooling and coiling process The increase of cooling rate can promote the transformation of Nb-Ti experimental steel from ferrite to pearlite to bainite and refine the ferrite grains.With continuous cooling, the microhardness of experimental steel decreases with the cooling And the increase of the rate increases gradually. However, the nucleation and growth of (Nb, Ti) C in the ferrite can be facilitated due to the small cooling rate during the coiling process, so that a large amount of nano-precipitates with uniform dispersion distribution exists in the ferrite So that the strength of the matrix increases, so with the increase of the cooling rate during the coiling process, the microhardness of the experimental steel tends to decrease.The nano-hardness of the ferrite phase in the Nb-Ti experimental steel is 4.13 GPa, Young’s modulus is 249.3 GPa, plain C-Si-Mn steel ferrite Phase nano-hardness is 2.64 GPa, Young’s modulus of 237.4 GPa, the contribution of nano-precipitates the ferrite phase of the nano-hardness reaches 1.49 GPa.