本文選題：低碳馬氏體 + 納米析出相��； 參考：《云南大學》2015年碩士論文

【摘要】：低碳馬氏體鋼具有板條馬氏體的組織,經(jīng)過熱處理低碳馬氏體具有相當高的強度,很好的塑性和韌性,同時還有較低的缺口敏感性、過熱敏感性、優(yōu)良的冷加工性、良好的可焊性等優(yōu)點。目前,隨著應用領域?qū)︿撹F材料要求的逐步提高,低碳馬氏體鋼的強度與韌性的匹配問題顯得尤為突出。晶粒細化是同時提高鋼鐵材料強度與韌性的有效方法。微合金化是細化晶粒的重要手段,微合金元素的析出行為在細化晶粒的過程中起到關鍵作用。由于低碳馬氏體組織具有復雜的多層次結構,控制其強度與韌性的有效晶粒尺寸包括原奧氏體晶粒尺寸、板條束尺寸和板條塊尺寸。但是,關于低碳馬氏體鋼中的析出相是如何分別影響這三種組織控制單元至今仍不十分清楚。本文設計了不同Ti、Mo含量的實驗鋼,采用直接淬火+回火+再加熱淬火熱處理工藝,通過金相顯微鏡、掃描電鏡、電子背散射衍射技術(EBSD)以及萃取相分析方法,研究低碳馬氏體鋼中析出相的析出行為,揭示析出相對有效晶粒尺寸的影響機制。 利用萃取相分析方法定量測定實驗鋼中的析出相發(fā)現(xiàn),在經(jīng)過直接淬火+回火+再加熱淬火熱處理后,單獨添加Ti元素的實驗鋼,Ti元素的析出量與鋼中添加Ti元素的含量成正比關系,鋼中添加的Ti元素幾乎完全析出,回火溫度變化對TiC析出量的影響不大；Ti、Mo復合添加的實驗鋼,在鋼中析出了(Ti,Mo)C,使析出量增多,析出相中Ti/Mo比隨Mo元素的添加快速減小。當回火溫度升高,鋼中析出相開始長大,在700℃進行回火的實驗鋼析出相中Ti/Mo比約為1,這時可以獲得6μ m左右的原奧氏體晶粒、5.92μ m馬氏體板條束和2.94μm的馬氏體板條塊,晶界強化效果明顯。 通過析出相粒度大小與有效晶粒尺寸變化規(guī)律研究發(fā)現(xiàn),析出相對有效晶粒的細化具有選擇性,1-10nm尺寸的析出相可以有效細化原奧氏體晶粒和半條束尺寸,10-20nm尺寸的析出相則細化板條塊尺寸。
[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，

本文編號：1972950