一种含铌新型奥氏体耐热钢组织与力学性能的研究

发布时间：2019-05-08 23:47

【摘要】：随着经济的发展和工业技术的进步,高放废物也随之大量增加。为了安全有效必须妥善处理高放废物,有学者提出将高危高放废物高温熔融后浇注到容器中密封然后做填埋处理。310S奥氏体耐热钢具有良好的加工性能和力学性能,是接收容器的首选材料,但310S钢在高温下仅依靠固溶强化,强度不足。为了提高310S钢高温力学性能,本研究提出在310S钢中的基础上添加Nb元素来提高其高温强度的思路。为此,本文首先利用Thermo-Calc热力学软件设计了一系列含Nb新型奥氏体耐热钢,对不同Nb含量的奥氏体耐热钢的显微组织、力学性能以及热加工性能进行了系统研究。论文主要研究内容和结论如下:(1)利用热力学计算软件Thermo-Calc,设计了一系列不同Nb含量的新型奥氏体耐热钢。在此基础上,通过真空感应炉和气体保护浇注制备了Nb含量为0、0.036 wt.%、0.12 wt.%、0.32wt.%和0.54 wt.%的新型奥氏体耐热钢,通过金相显微镜和扫描电镜对锻后组织观察表明热力学计算和实验结果吻合良好。(2)对不同Nb含量新型奥氏体耐热钢进行固溶处理后,测试了不同Nb含量新型奥氏体耐热钢的室温和高温力学性能。结果表明:随着Nb含量增加材料室温强度变化不大,但高温强度逐渐提高,达到了通过添加Nb元素来提高材料高温强度的目标。同时,Nb的添加会略微降低材料的室温冲击韧性。(3)采用Gleeble热模拟压缩实验,研究不同Nb含量奥氏体耐热钢的在900~1200℃温度范围内和0.001-1~10s-1应变速率下的热变形特征。根据双曲正弦模型建立Z参数与峰值应力的关系,发现随着Z值的增加,材料的峰值应力也增加,同时材料的动态再结晶也越难发生。利用Laasraoui和jonas模型建立高温应力-应变模型,发现在相同应变速率和相同温度条件下,材料的峰值应力、稳态应力以及饱和应力随着Nb含量升高而提高;同时Nb会抑制动态再结晶,提高材料热变形激活能。结合动态材料模型和连续失稳判据,绘制了不同Nb含量的奥氏体耐热钢的热加工图。(4)以0.32wt.%Nb材料为载体,研究了材料中Nb(C,N)对动态再结晶抑制机制。使用ECCI观察热压缩变形试样组织,发现Nb(C,N)析出相有效钉扎了材料在热变形中位错的运动。
[Abstract]:With the development of economy and the progress of industrial technology, the high-level radioactive waste also increases greatly. In order to be safe and effective, high-level radioactive waste must be properly treated. Some scholars have proposed that high-risk high-level radioactive waste should be melted at high temperature and then sealed in a container and then landfill. 310S austenitic heat-resistant steel has good processing and mechanical properties. It is the first choice material for receiving container, but 310S steel only depends on solid solution strengthening at high temperature, and its strength is insufficient. In order to improve the high temperature mechanical properties of 310S steel, the idea of adding Nb element to 310S steel to improve its high temperature strength is put forward in this paper. In this paper, a series of new austenitic heat-resistant steels containing Nb were designed by using Thermo-Calc thermodynamic software. The microstructure, mechanical properties and hot-working properties of austenitic heat-resistant steels with different Nb contents were studied systematically. The main contents and conclusions of this paper are as follows: (1) A series of new Austenite heat-resistant steel with different Nb content were designed by using thermodynamic calculation software Thermo-Calc,. On this basis, a new type of Austenite heat-resistant steel with Nb content of 0, 0. 036 wt.%,0.12 wt.%,0.32wt.% and 0. 54 wt.% was prepared by vacuum induction furnace and gas-protected pouring. The microstructure observation after forging by metallographic microscope and scanning electron microscope shows that the thermodynamic calculation and experimental results are in good agreement with the experimental results. (2) the new austenitic heat-resistant steels with different Nb content are treated by solid solution treatment. The mechanical properties of new austenitic heat resistant steels with different Nb content at room temperature and at high temperature were tested. The results show that the room temperature strength of the material does not change much with the increase of Nb content, but the high temperature strength increases gradually, which achieves the goal of improving the high temperature strength of the material by adding Nb element. At the same time, the addition of Nb will slightly reduce the impact toughness of the material at room temperature. (3) the Gleeble thermal simulation compression experiment is used. The thermal deformation characteristics of austenitic heat resistant steels with different Nb content at 900 鈩，

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