HRB400钢筋中钒的析出行为研究.pdf

Master Dissertation of Chongqing University Study on Precipitation Behaviors of carbonitride of vanadium in HRB400 reinforced steel bars Master Candidate: Jiang Liping Supervisor: Prof. Sheng Guangmin Major: Materials Science and Engineering College of Materials Science and Engineering Chongqing University October 2007 摘 要 为充分发挥 HRB400 20MnSiV 钢筋中微量 V 的有益作用，本文主要采用应力 松驰法研究该试验材料中钒碳氮化物在奥氏体中的析出行为，绘制了相应沉淀物 百分数—温度— 时间曲线(PTT 曲线) ，使用透射电子显微镜(TEM)对应力松驰后的 试样中的钒的析出进行了观察、分析，并采用本文提出的工艺参数，在水钢生产 现场进行了轧制试验，观察结果表明，V 的析出行为得到改善。 实验结果表明，在同一压缩变形量时，钒的碳氮化物析出动力学曲线呈典型 的“C”形曲线，即存在一个最快析出的温度和时间—— 孕育期。当压缩变形量 ε=0.05(真应变 e=-0.05)时，最快析出温度约为 850℃，开始析出时间约为 6s；当压 缩变形量 ε=0.20(e=-0.22) ，最快析出温度约为 870℃，开始析出时间约 0.7s ；当压 缩变形量 ε=0.50(e=-0.69) ，最快析出温度约为 870℃，开始析出时间约为 1.2s。在 同一温度时，压缩变形量的增大，将加快钒的碳氮化物析出。用透射电子显微镜 则观察各变形量最快析出温度时的薄膜样品，发现钒的碳氮化物不仅在晶粒内部 析出，而且更多的是在位错线附近析出。对所得实验结果通过热力学、动力学计 算验证，两者基本吻合。 关键词：微合金钢，析出动力学，应力松驰，钢筋 I ABSTRACT In order to make full use of vanadium’s effect (refine grain and precipitation), the performace of carbonitride precipitating in austenite of HRB400 reinforced steel bars microalloyed with vanadium was investigated by the stress relaxation on Gleeble ther- -mal simulator in this paper. At last the curves of precipitation-temperature-time (PTT) were plotted according to the curves of stress relaxation at different temperature but at the same deformation amount. The precipitates formed in the sample during stress relaxation at different temperatures were observed under transmission electron microscope(TEM) . The results of the experiments show that the precipitation start time is relative to temperature, deformation. At