含Ti马氏体钢中析出相对有效晶粒尺寸的影响规律研究

发布时间：2018-06-03 13:29

  本文选题：低碳马氏体 + 纳米析出相　； 参考：《云南大学》2015年硕士论文

【摘要】：低碳马氏体钢具有板条马氏体的组织,经过热处理低碳马氏体具有相当高的强度,很好的塑性和韧性,同时还有较低的缺口敏感性、过热敏感性、优良的冷加工性、良好的可焊性等优点。目前,随着应用领域对钢铁材料要求的逐步提高,低碳马氏体钢的强度与韧性的匹配问题显得尤为突出。晶粒细化是同时提高钢铁材料强度与韧性的有效方法。微合金化是细化晶粒的重要手段,微合金元素的析出行为在细化晶粒的过程中起到关键作用。由于低碳马氏体组织具有复杂的多层次结构,控制其强度与韧性的有效晶粒尺寸包括原奥氏体晶粒尺寸、板条束尺寸和板条块尺寸。但是,关于低碳马氏体钢中的析出相是如何分别影响这三种组织控制单元至今仍不十分清楚。本文设计了不同Ti、Mo含量的实验钢,采用直接淬火+回火+再加热淬火热处理工艺,通过金相显微镜、扫描电镜、电子背散射衍射技术(EBSD)以及萃取相分析方法,研究低碳马氏体钢中析出相的析出行为,揭示析出相对有效晶粒尺寸的影响机制。 利用萃取相分析方法定量测定实验钢中的析出相发现,在经过直接淬火+回火+再加热淬火热处理后,单独添加Ti元素的实验钢,Ti元素的析出量与钢中添加Ti元素的含量成正比关系,钢中添加的Ti元素几乎完全析出,回火温度变化对TiC析出量的影响不大；Ti、Mo复合添加的实验钢,在钢中析出了(Ti,Mo)C,使析出量增多,析出相中Ti/Mo比随Mo元素的添加快速减小。当回火温度升高,钢中析出相开始长大,在700℃进行回火的实验钢析出相中Ti/Mo比约为1,这时可以获得6μ m左右的原奥氏体晶粒、5.92μ m马氏体板条束和2.94μm的马氏体板条块,晶界强化效果明显。 通过析出相粒度大小与有效晶粒尺寸变化规律研究发现,析出相对有效晶粒的细化具有选择性,1-10nm尺寸的析出相可以有效细化原奥氏体晶粒和半条束尺寸,10-20nm尺寸的析出相则细化板条块尺寸。
[Abstract]:Low carbon martensite steel has lath martensite structure, heat treated low carbon martensite has quite high strength, good plasticity and toughness, at the same time, it also has low notch sensitivity, overheating sensitivity, excellent cold working property. Good weldability and other advantages. At present, the matching of strength and toughness of low carbon martensite steel is becoming more and more important with the increasing requirement of steel materials in application field. Grain refinement is an effective method to improve both strength and toughness of iron and steel materials. Microalloying is an important means of grain refinement, and the precipitation behavior of microalloying elements plays a key role in the process of grain refinement. Due to the complex multi-layer structure of low carbon martensite, the effective grain size controlling its strength and toughness includes austenite grain size, lath beam size and lath size. However, it is not clear how the precipitates in low carbon martensite steel affect these three microstructures separately. In this paper, experimental steels with different Ti-Mo content were designed. The process of direct quenching and tempering and reheating quenching and quenching was adopted, and the extraction phase was analyzed by metallographic microscope, scanning electron microscope, electron backscatter diffraction (EBSD) and extraction phase analysis. The precipitation behavior of precipitated phase in low carbon martensite steel was studied and the influence mechanism of relative effective grain size was revealed. Quantitative determination of precipitate phase in experimental steel by extraction phase analysis method shows that after direct quenching and tempering and reheating quenching heat treatment, The amount of Ti precipitated in the experimental steel added alone with Ti element is proportional to the content of Ti element in the steel, and the Ti element added in the steel is almost completely precipitated. The effect of tempering temperature on the amount of TiC precipitation is not significant. The Ti/Mo ratio in the precipitated phase decreases rapidly with the addition of Mo elements. When the tempering temperature increases, the precipitated phase begins to grow and the Ti/Mo ratio in the precipitated phase of the experimental steel tempered at 700 鈩，

本文编号：1972950