新型高Cr铁素体耐热钢的相变研究

发布时间：2018-01-03 14:23

本文关键词：新型高Cr铁素体耐热钢的相变研究　出处：《山东理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：对9%-12%Cr铁素体耐热钢进行降低C含量、增加Cr含量及添加Co、Mo、W组元的优化调整,经真空感应熔炼炉熔炼并浇注成型,利用差热分析(DTA)、扫描电镜(SEM)、X射线衍射(XRD)以及电子蠕变试验等分析手段研究了加热温度、冷却速度以及回火等热处理工艺对高Cr铁素体耐热钢显微组织和力学性能的影响,得到如下结论:试验钢加热时在600-1100℃之间依次发生磁性转变、奥氏体形成、M23C6型碳化物溶解和奥氏体向δ-铁素体转变,奥氏体开始形成温度为853℃,空冷或以40℃/min的速度冷却时发生马氏体转变,马氏体开始转变温度为382℃;含铌的MC型碳化物非常稳定,在试验加热温度范围不能完全溶解到奥氏体中。1050℃×1h固溶处理后的扫描电镜显示试验钢组织为典型板条状马氏体,在马氏体板条界及原奥氏体晶界上分布着颗粒状碳化物,以不同冷却速度处理后试样的显微组织显示随着冷却速度的降低,马氏体板条逐渐变粗,碳化物的析出相逐渐增多,并在晶界处发生了聚集长大,X射线衍射分析表明碳化物为M23C6型碳化物,随着冷却速度的增大,硬度呈现逐渐升高的趋势。经过1100℃×1h空冷后的组织为典型板条马氏体和少量δ铁素体,有MX型未溶碳化物NbC分布在基体中。经过1100℃×1h空冷+780℃×2h空冷处理试样的组织为典型回火马氏体,基体中主要析出相为M23C6型碳化物。马氏体-δ铁素体晶界处的碳化物较粗大成连续状分布,马氏体板条界的析出相较细小。经过1100℃×1h空冷+780℃×2h空冷处理后的试验钢具有较高蠕变强度,650℃/200MPa的持久寿命为411.4h,650℃/170MPa的持久寿命为1499.1h,持久性能较NIMS公布的T/P92、P/T122耐热钢有较大提升。
[Abstract]:The 9%-12%Cr ferritic heat resistant steel for reducing the content of C, increase the content of Cr and Co added, Mo, W group optimization element, by vacuum induction melting furnace smelting and casting, using differential thermal analysis (DTA), scanning electron microscopy (SEM), X ray diffraction (XRD) and electronic creep test the analysis means of heating temperature of heat treatment, cooling rate and tempering process of steel microstructure and mechanical properties of Cr heat resistant high iron, we get the following conclusions: the test steel is heated in the magnetic transition in 600-1100 DEG M23C6 type carbide Austenite Formation, dissolution and austenite to ferrite transformation Austenitic, began to form a temperature of 853 DEG C, air cooling or cooling speed to 40 DEG /min when the martensite transformation occurs, the martensite start temperature is 382 DEG C; MC type carbide containing niobium is very stable in the test temperature range does not dissolve to Scanning electron microscopy.1050 c * 1h after solution treatment of austenitic steel is shown in the test typical lath martensite and granular carbides distributed in martensite lath boundaries and the grain boundaries, the microstructure of the specimens with different cooling rates after the treatment showed that with the decrease of cooling rate, the martensite becomes thick, carbide the precipitates gradually increased, and the coarsening occurs at the grain boundaries, X ray diffraction analysis showed that the M23C6 type carbide carbide, with the increase of cooling rate, the hardness increased gradually. After 1100 DEG C * 1H air cooling after the organization is typical of lath martensite and less ferrite, MX undissolved carbide NbC distributed in the matrix. After 1100 DEG C * 1H air-cooled +780 c * 2H air cooling treatment the microstructure of typical martensite matrix, the main precipitation phase was M23C6 type martensite - Delta iron carbide. The ferrite grain boundary carbide coarsening into a continuous distribution, precipitation of martensite lath boundaries compared to small. After testing steel 1100 c * 1H air cooling +780 c * 2H air cooling after treatment with high creep strength, creep rupture life at 650 for /200MPa 411.4h, lasting life at 650 for /170MPa 1499.1h, durable the performance is published by NIMS T/P92, has greatly improved P/T122 heat resistant steel.

【学位授予单位】：山东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG142.73

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