La对800H镍基耐蚀合金组织和力学性能的影响

发布时间：2018-04-23 08:59

本文选题：800H镍基耐蚀合金 + La　；参考：《太原理工大学》2017年硕士论文

【摘要】：随着科学技术及工业生产的快速发展,800H镍基耐蚀合金在航空航天、石油化工、核工业等领域的应用越来越广泛。传统的800H镍基合金的生产工艺为模铸、电渣重熔等,但这种工艺成材率和生产效率低下,成本较高。采用立式板坯连铸新工艺可大规模生产800H合金,提高生产效率,但生产的连铸坯初始凝固组织晶粒粗大,恶化合金的强/韧性。为此,本研究以宝钢生产的800H镍基合金为研究对象,用真空感应炉冶炼四组不同La含量的800H试验合金。研究、分析La含量对凝固组织细化、夹杂物特征、力学性能的影响及其作用机理。为细化800H合金连铸坯凝固组织晶,开发低成本的800H合金生产技术提供基础实验数据,对解决生产过程中存在的表面缺陷和废品率较高的问题,调整我国钢铁产业结构,具有潜在的应用价值和指导意义。其研究方法和内容包括:(1)用真空感应炉在MgO坩埚内冶炼制备四组不同La含量的800H合金试样,进行化学成分检测,结合现代冶金理论,分析、探讨La元素对钢液洁净化、细晶化的作用机理;(2)用现代的检测技术手段,如金相显微镜(OM)、扫描电镜(SEM)、能谱仪(EDS),表征实验数据,通过热力学计算与动力学分析,描述亚微米级夹杂物在钢液精炼过程中的演变机制;(3)用二维晶格错配度公式,计算不同夹杂物与800h合金的晶格错配度,定性描述含la亚微米级夹杂物细化凝固组织的机理;(4)用800h合金试样的力学性能随la含量变化的实验数据,分析、探讨亚微米级夹杂物对800h镍基合金综合力学性能的作用机理。通过试验研究,本文得出以下结论:(1)800h合金中[la]由0%增加到0.047%时,[o]由0.013%降低到0.007%,[s]由0.003%降低到0.001%,说明la具有很强的脱硫、脱氧和钢液净化能力。(2)la可显著细化800h合金的凝固组织,当[la]由0增加到0.047%时,等轴晶比例由0增加到75%,等轴晶晶粒尺寸由6.0μm减小到3.2μm,枝晶组织变细变短,一次枝晶间距由77.5μm降低到43.8μm,二次枝晶间距基本没变。(3)la可以显著细化800h合金的奥氏体晶粒,当合金中[la]含量由0增加到0.047%时,奥氏体晶粒尺寸由121.32μm变为42.57μm。(4)800h合金中添加la后,大尺寸的al2o3夹杂物与长条状、大体积的mns夹杂物被改性为小尺寸、类球状的含la夹杂物,并生成大量高熔点的la2o3和la2o2s颗粒。错配度结果表明,800h合金(111)面/la2o3的(0001)面之间的错配度为6.7%,800h合金的(100)面/la2o2s的(0001)面之间的错配度为5.42%,因其错配度较低,能够提供大量的非均质形核有效核心,是细化800h镍基耐蚀合金合金的凝固组织得到显著细化。(5)随着800h合金中la含量的增加,800h合金的力学性能呈现明显升高的趋势,当[la]含量由0增加到0.047%时,试样的屈服强度、抗拉强度、延伸率、和冲击功分别提高46.9%、22.3%、21.1%和23%。La改善800H合金的凝固组织,细化奥氏体晶粒及La对夹杂物的改性是提高800H合金力学性能的主要原因
[Abstract]:With the rapid development of science and technology and industrial production, 800H nickel base corrosion resistant alloys are widely used in aerospace, petrochemical, nuclear industry and other fields. The traditional production process of 800H nickel-base alloy is mold casting, electroslag remelting, etc. However, the production efficiency and efficiency of this process are low and the cost is high. The new process of vertical slab continuous casting can produce 800H alloy in large scale and improve the production efficiency. However, the grain size of the initial solidification of the continuous casting billet is coarse, and the strength / toughness of the alloy is deteriorated. Therefore, the 800H nickel-base alloy produced by Baosteel was used to smelt four groups of 800H alloys with different La content in vacuum induction furnace. The effect of La content on solidification microstructure, inclusions, mechanical properties and its mechanism were studied and analyzed. In order to refine solidified microstructure of 800H alloy continuous casting billet and develop low cost 800H alloy production technology, the basic experimental data can be provided to solve the problems of surface defects and high scrap rate in the production process and to adjust the structure of China's iron and steel industry. It has potential application value and guiding significance. The research methods and contents include: using vacuum induction furnace to smelt in MgO crucible four groups of samples of 800H alloy with different La content were prepared. The chemical composition of 800H alloy samples was tested. Combined with modern metallurgical theory, the purification of molten steel by La element was discussed. The mechanism of fine crystallization is characterized by modern detection techniques, such as metallographic microscope, scanning electron microscope (SEM), energy spectrometer (EDS), and thermodynamic calculation and kinetic analysis. The evolution mechanism of submicron inclusions in the refining process of molten steel is described. The lattice mismatch between different inclusions and 800h alloys is calculated by using the two-dimensional lattice mismatch formula. Qualitative description of the mechanism of refining solidified microstructure containing la submicron inclusions) with the experimental data of the change of mechanical properties of 800h alloy samples with la content, the mechanism of the effect of submicron inclusions on the comprehensive mechanical properties of 800h nickel-based alloys is discussed. Through experimental study, the following conclusions are drawn: when [la] increases from 0% to 0.047%, [o] decreases from 0.013% to 0.007% and [s] from 0.003% to 0.001. It shows that la has strong desulfurization, deoxidation and purification ability of molten steel. When [la] increases from 0 to 0.047, the proportion of equiaxed grains increases from 0 to 75, the grain size of equiaxed grains decreases from 6.0 渭 m to 3.2 渭 m, and the dendrite structure becomes thinner and shorter. The primary dendritic spacing was reduced from 77.5 渭 m to 43.8 渭 m, and the secondary dendrite spacing was basically unchanged. The austenitic grain size of 800h alloy could be significantly refined when the content of [la] in the alloy increased from 0 to 0.0477.The austenite grain size changed from 121.32 渭 m to 42.57 渭 m / 4800h alloy. Large size al2o3 inclusions and long stripe, large volume mns inclusions were modified into small size, globular inclusions containing la, and a large number of la2o3 and la2o2s particles with high melting point were formed. The mismatch results show that the mismatch between the / / la2o3 / la0001) faces of the alloy / la2o3 has a mismatch of 5.42) between the / / /'/ /'/\% /\% /\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\% of the mismatch of the alloy / / /\%\%\% la2o3 /\%\%\%\%\%\%\%\%\ It was found that the solidification microstructure of 800 h nickel base corrosion resistant alloy was significantly refined. (5) with the increase of la content in 800 h alloy, the mechanical properties of the alloy increased obviously. When the content of [la] increased from 0 to 0.047, the yield strength of the specimen was increased. Tensile strength, elongation and impact work were increased by 46.9% and 22.1%, respectively, and 23%.La was used to improve solidification microstructure of 800H alloy. Refinement of austenite grain and modification of inclusion by La were the main reasons for improving mechanical properties of 800H alloy.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG133.4

【参考文献】