高中压转子铸锭凝固过程数值模拟及服役条件下组织演变研究
发布时间：2018-11-16 16:24
【摘要】：超超临界汽轮机高中压转子作为典型的大型锻件产品,其生产制造流程中大型钢锭的铸锭是最关键环节,大型铸锭质量是决定锻件产品质量的重要基础。而铸锭质量主要与凝固过程控制相关,因此,有必要对铸锭凝固过程进行系统深入研究。另一方面,高中压转子在长期服役过程中,涉及高温和应力作用下微观组织演变等组织稳定性理论问题,需要全面系统地了解高中压转子材料在高温/力作用下微观组织亚结构演变规律。这是超超临界汽轮机高中压转子产品开发和使用中面临的两个核心理论问题,必须深入开展理论研究,为制造工程提供科学支撑。针对上述两个核心问题,以高中压转子用材X12CrMoWVNbN10-1-1为例,开展了系统探究,主要的研究内容与研究结果如下:1.运用ProCast软件对大型铸锭凝固过程中温度场、流场进行模拟计算。并根据改进型Niyama判据对铸锭中心疏松分布进行预测。结果表明,中心疏松缺陷呈细长条带分布。建立了表征中心疏松区域尺度的判据函数N=H_(porosity)/H_(ingot),其中H_(porosity)为疏松带长度,H_(ingot)为铸锭高度,结果表明,锭身高径比从1.0增加至1.5,判据函数N值基本按二次多项式规律增加,其数值由0.274增加至0.509;而锭身锥度由6%增加至12%,N值基本按线性规律递减,其数值由0.378减小到0.309。2.采用CAFE(元胞有限元)法对铸锭宏观组织进行模拟计算,通过低倍组织检验对数值模拟准确性进行验证。并基于此CAFE模型,研究形核密度以及过热度对柱状晶和等轴晶分布、芯部等轴晶晶粒尺寸等几方面的影响规律。3.为缩小冒口尺寸,开发了冒口感应加热专利技术。通过数值模拟定量描述了感应加热过程中温度场及流场分布,研究了电参数(输入功率、频率)及线圈设计(熔体与线圈间距、线圈高度)对感应加热过程的影响。结果表明:冒口感应加热技术可以控制铸锭冒口的凝固过程,影响冒口区域流场分布,并且随着加热功率提高,缩孔形态由窄而深的“V字型”转变为浅而平的“碗状”,缩孔深度大大减少。以200 kg中间试验铸锭为例,通过冒口感应加热使得缩孔深度相对减小了40%。4.650℃时效结果表明,时效750 h后,开始有Laves相析出。时效10000 h后,基体α相和Laves相存在的位向关系为:{011}α∥{0001}Laves、{411}α∥{0001}Laves、{111}α∥{0001}Laves、{011}α∥{2110}Laves、{211}α∥{1101}Laves。5.650℃/300 h蠕变试验结果表明,蠕变应力促进了马氏体板条宽化程度,蠕变应力从0增至170 MPa,马氏体板条宽度由330 nm增至465 nm。M23C6尺寸由97 nm增加至130 nm,数量密度由2.55个/μm~2减少至2.08个/μm~2;而MX型析出相尺寸和数量密度相对稳定,分别为80 nm和2.8个/μm~2,蠕变应力没有对其产生明显影响。初生Laves大多沿50-60°大角度晶界析出,蠕变应力会促进Laves相沿晶界和板条界的形核长大。通过EBSD、TEM、XRD等先进手段针对高中压转子服役过程中热作用下的Laves与基体相位向关系、热-应力综合作用下组织演变理论问题所进行的深入剖析,丰富和拓展了我国超超临界高中压转子材料服役条件下的组织性能稳定性研究理论体系。高中压转子材料铸锭凝固过程的数值模拟计算研究结果深化了凝固过程所涉及的温度场、缩孔及中心疏松缺陷分布、凝固宏观组织分布等理论问题的认识,可对我国高中压转子用大型铸锭生产中钢锭模设计优化提供理论依据与技术指导,具有显著的工程实践意义。
[Abstract]:As a typical large-scale forging product, the super-supercritical steam turbine high-pressure rotor is the most critical step in the production and manufacturing process of large-scale ingot, and the quality of large-scale ingot is an important basis for determining the product quality of the forging. The quality of the ingot is mainly related to the control of the solidification process. Therefore, it is necessary to deeply study the solidification process of the ingot. On the other hand, in the process of long-term service, the high-and high-pressure rotor relates to the theory of microstructure evolution such as microstructure evolution under high temperature and stress. It is necessary to comprehensively and systematically understand the microstructure evolution of the high-and high-pressure rotor material under the action of high temperature/ force. This is the two core theoretical problems faced in the product development and use of the super-supercritical steam turbine high-pressure rotor, and the theoretical research must be carried out to provide scientific support for manufacturing engineering. In view of the above two core problems, the system inquiry is carried out with the material X12CrMoWVNbN10-1-1 for high-school pressure rotor, and the main research contents and the research results are as follows: 1. The temperature field and flow field in the solidification process of large-scale ingot were simulated by using ProCast software. and the loose distribution of the ingot center is predicted according to the modified Niyama criterion. The results show that the central loose defect is in the form of an elongated strip. The criterion function N = H _ (porsoity)/ H _ (ingot) for the scale of the central loose zone is established, where H _ (porsoity) is the length of the loose strip, and the H _ (ingot) is the height of the ingot. The results show that the height-diameter ratio of the ingot is increased from 1.0 to 1.5, and the N value of the criterion function is basically increased by the law of the quadratic polynomial, and its value is increased from 0.274 to 0.509; and the taper of the spindle body is increased from 6% to 12%, and the N value is gradually decreased by the linear rule, and the numerical value is reduced from 0.378 to 0.309. 2. In this paper, the CAFE method is used to calculate the macrostructure of the ingot, and the accuracy of the numerical simulation is verified by the low-time tissue test. Based on the CAFE model, the influence of the shape core density and the degree of superheat on the crystal grain size of the equiaxed grain and the equiaxed grain, the core part and the like is studied. In order to reduce the size of the riser, the technology of riser induction heating is developed. The influence of the electric parameters (input power, frequency) and coil design (the distance between the melt and the coil and the height of the coil) on the induction heating process is studied by means of numerical simulation. The results show that the riser induction heating technology can control the solidification process of the riser and influence the distribution of the flow field in the riser region, and the shrinkage cavity form is changed from the narrow and deep 鈥淰-type鈥，
本文编号：2336010
[Abstract]:As a typical large-scale forging product, the super-supercritical steam turbine high-pressure rotor is the most critical step in the production and manufacturing process of large-scale ingot, and the quality of large-scale ingot is an important basis for determining the product quality of the forging. The quality of the ingot is mainly related to the control of the solidification process. Therefore, it is necessary to deeply study the solidification process of the ingot. On the other hand, in the process of long-term service, the high-and high-pressure rotor relates to the theory of microstructure evolution such as microstructure evolution under high temperature and stress. It is necessary to comprehensively and systematically understand the microstructure evolution of the high-and high-pressure rotor material under the action of high temperature/ force. This is the two core theoretical problems faced in the product development and use of the super-supercritical steam turbine high-pressure rotor, and the theoretical research must be carried out to provide scientific support for manufacturing engineering. In view of the above two core problems, the system inquiry is carried out with the material X12CrMoWVNbN10-1-1 for high-school pressure rotor, and the main research contents and the research results are as follows: 1. The temperature field and flow field in the solidification process of large-scale ingot were simulated by using ProCast software. and the loose distribution of the ingot center is predicted according to the modified Niyama criterion. The results show that the central loose defect is in the form of an elongated strip. The criterion function N = H _ (porsoity)/ H _ (ingot) for the scale of the central loose zone is established, where H _ (porsoity) is the length of the loose strip, and the H _ (ingot) is the height of the ingot. The results show that the height-diameter ratio of the ingot is increased from 1.0 to 1.5, and the N value of the criterion function is basically increased by the law of the quadratic polynomial, and its value is increased from 0.274 to 0.509; and the taper of the spindle body is increased from 6% to 12%, and the N value is gradually decreased by the linear rule, and the numerical value is reduced from 0.378 to 0.309. 2. In this paper, the CAFE method is used to calculate the macrostructure of the ingot, and the accuracy of the numerical simulation is verified by the low-time tissue test. Based on the CAFE model, the influence of the shape core density and the degree of superheat on the crystal grain size of the equiaxed grain and the equiaxed grain, the core part and the like is studied. In order to reduce the size of the riser, the technology of riser induction heating is developed. The influence of the electric parameters (input power, frequency) and coil design (the distance between the melt and the coil and the height of the coil) on the induction heating process is studied by means of numerical simulation. The results show that the riser induction heating technology can control the solidification process of the riser and influence the distribution of the flow field in the riser region, and the shrinkage cavity form is changed from the narrow and deep 鈥淰-type鈥，
本文编号：2336010
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