终冷温度对高强度抗震钢筋组织和性能的影响

用Gleeble-3800热模拟机进行高强度抗震钢筋的热模拟实验，使用金相显微镜(OM)、场发射扫描电子显微镜(SEM)、高分辨透射电子显微镜(TEM)和万能拉伸试验机等手段表征其微观结构、第二相、力学性能和断口形貌，研究了终冷温度对高强度抗震钢筋的组织和性能的影响并揭示微合金元素细化晶粒的机理。结果表明：实验钢的显微组织主要为铁素体和珠光体，随着终冷温度的降低铁素体晶粒细化。终冷温度为650℃时实验钢中分布在铁素体基体上的主要析出相 (Nb, Ti, V)C和(V, Nb, Ti)C的平均粒径约为2 nm和5 nm。随着终冷温度的降低实验钢的抗拉强度和屈服强度都增加，终冷温度为650℃时其抗拉强度和屈服强度分别为638.75 MPa和467 MPa，强屈比为1.37。在不同终冷温度实验钢的拉伸断口主要为等轴韧窝，其尺寸和深度不同。

Effect of Final Temperature of Cooling on Microstructure and Properties of Aseismic High-strength Steel Rebar

The thermal simulation test of an experimental aseismic high strength steel was conducted by Gleeble-3800 thermal simulator, then its microstructure, second phase, mechanical properties and fracture morphology were characterized by metallographic microscopy (OM), field emission scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM) and universal tensile testing machine. Meanwhile, the effect of final temperature of cooling on the microstructure and properties of the steel was carefully examined, and the grain refinement mechanism induced by microalloying elements was revealed. The results show that: the microstructure of the steel consists mainly of phases ferrite and pearlite, and the ferrite grain was refined with the decrease of the final temperature of cooling. The average diameter of precipitated carbides (Nb, Ti, V) C and (V, Nb, Ti) C distributed in the ferrite matrix of the steel is about 2 nm and 5 nm respectively for the final temperature of cooling 650℃. The tensile strength and yield strength of the steel increase with the decrease of the final temperature of cooling. When the final temperature of cooling is 650℃, the corresponding tensile strength and yield strength are 638.75 MPa and 467 MPa, respectively, and the strength/yield ratio is 1.37. The tensile fractured surface of steels, which have been experienced thermal simulation tests with different final temperatures of cooling, exhibits mainly equiaxed dimples of different sizes and depths.