共查询到15条相似文献,搜索用时 156 毫秒
1.
2.
3.
实测了单向凝固过程中固液界面前沿液相的温度梯度,且研究了固液界面两温度梯度间的关系。 相似文献
4.
采用ProCAST铸造仿真软件对镍基中空叶片定向凝固过程进行仿真模拟。结果表明:当界面换热系数恒定为1 500 W/m2·K时,随着抽拉速率逐渐降低,糊状区最小宽度从66.4 mm(v=8 mm/min)降低为39.1 mm(v=2mm/min);当抽拉速率恒定为2 mm/min时,随着界面换热系数降低,糊状区最小宽度从74.5 mm(H=1 500 W/m2·K)降低为39.1 mm(500 W/m2·K);抽拉速率和界面换热系数分别为2 mm/min和1 500 W/m2·K时,中空叶片最大位移量约为0.05 mm,可获得一定的尺寸精度。 相似文献
5.
采用ProCAST铸造仿真软件对镍基中空叶片定向凝固过程进行仿真模拟。结果表明:当界面换热系数恒定为1 500 W/m2·K时,随着抽拉速率逐渐降低,糊状区最小宽度从66.4 mm(v=8 mm/min)降低为39.1 mm(v=2mm/min);当抽拉速率恒定为2 mm/min时,随着界面换热系数降低,糊状区最小宽度从74.5 mm(H=1 500 W/m2·K)降低为39.1 mm(500 W/m2·K);抽拉速率和界面换热系数分别为2 mm/min和1 500 W/m2·K时,中空叶片最大位移量约为0.05 mm,可获得一定的尺寸精度。 相似文献
6.
定向凝固技术与理论研究的进展 总被引:7,自引:5,他引:7
阐述了不同定向凝固方法的原理以及定向凝固技术的发展趋势。从定向凝固技术的演化过程看,是温度梯度不断提高、冷却速度不断加快的过程。从传统的定向凝固技术中逐渐演化出冷坩埚定向凝固技术、软接触陶瓷壳定向凝固技术、双频电磁约束成形定向凝固技术等.简述了单相合金成分过冷与界面稳定性理论,共晶合金、包晶合金以及偏品合金的相选择及组织演化等。 相似文献
7.
定向凝固ZMLMC法温度梯度的测定及其对凝固组织的影响 总被引:2,自引:0,他引:2
对定向凝固区域熔化液态金属冷却法的固液界面前沿温度梯度进行了测定。在3mm/min的凝固速率下得到的温度梯度高达813K/cm,并且发现温度梯度随着凝固速率的增加而呈减小趋势。得出这种工艺下一次枝晶间距λ1与工艺参数即温度梯度GL和凝固速率V的对应关系,在此工艺参数下获得良好的定向组织。对试验数据λ1与GL-0.5、V-0.25值进行线性回归,其线性回归关系式为:λ1=-0.0032 0.0655G-0.5V-0.25。 相似文献
8.
高温合金叶片定向凝固的微机控制 总被引:1,自引:1,他引:0
通过计算机系统对高温合金定向涡轮叶片的凝固过程实现控制,减小生产过程中随机因素波动对叶片生产质量的影响。通过实验模索出了K5和DZ38G两种材料的斯贝发动机涡轮叶片凝固过程归佳抽拉曲线。实验证明,在计算机控制系统和这种条件下,叶片的宏观和微观组织都有明显的改进和提高。 相似文献
9.
通过调整合金中Sr和Mg的加入量、温度梯度和凝固速度,对Al-12.5Si合金进行一系列定向凝固试验。结果表明,Sr可以对共晶Si进行变质,得到规则界面,也可以引起界面失稳,因为和Mg一样,其溶质分配系数k01,增加了成分过冷。随Sr或Mg含量增加,共晶界面的演化过程为平界面→胞状晶→树枝晶→等轴晶;随凝固速度增大和温度梯度减小,界面前沿成分过冷变大,界面形貌经历了从失稳到胞晶、树枝晶和等轴晶的转变。 相似文献
10.
11.
《中国铸造》2016,(6):402-413
Numerical heat-transfer and turbulent lfow model for an industrial high-pressure gas quenching vacuum furnace was established to simulate the heating, holding and gas fan quenching of a low rhenium-bearing Ni-based single crystal turbine blade. The mesh of simpliifed furnace model was built using ifnite volume method and the boundary conditions were set up according to the practical process. Simulation results show that the turbine blade geometry and the mutual shielding among blades have signiifcant inlfuence on the uniformity of the temperature distribution. The temperature distribution at sharp corner, thin wal and corner part is higher than that at thick wal part of blade during heating, and the isotherms show a toroidal line to the center of thick wal. The temperature of sheltered units is lower than that of the remaining part of blade. When there is no shelteration among multiple blades, the temperature distribution for al blades is almost identical. The lfuid velocity ifeld, temperature ifeld and cooling curves of the single and multiple turbine blades during gas fan quenching were also simulated. Modeling results indicate that the loading tray, free outlet and the location of turbine blades have important inlfuences on the lfow ifeld. The high-speed gas lfows out from the nozzle is divided by loading tray, and the free outlet enhanced the two vortex lfow at the end of the furnace door. The closer the blade is to the exhaust outlet and the nozzle, the greater the lfow velocity is and the more adequate the lfow is. The blade geometry has an effect on the cooling for single blade and multiple blades during gas fan quenching, and the effects in double layers differs from that in single layer. For single blade, the cooing rate at thin-waled part is lower than that at thick-waled part, the cooling rate at sharp corner is greater than that at tenon and blade platform, and the temperature at regions close to the internal position is decreased more slowly than that close to the surface. For multiple blades in single layer, the temperature at sharp corner or thin wal in the blade that close to the nozzles is much lower, and the temperature distribution of blades is almost paralel. The cooling rate inside the air current channel is lower than that of at the position near blade platform and tenon, and the effect of blade location to the nozzles on the temperature ifeld inside the blade is lower than that on the blade surface. For multiple blades in double layers, the lfow velocity is low, and the lfow is not uniform for blades in the second-layer due to the shielding of blades in the ifrst-layer. the cooling rate of blades in the second-layer is lower than that in the ifrst-layer. The cooling rate of blade close to the nozzles in the ifrst-layer is the higher than that of blade away from the nozzles in the second-layer, and the temperature distribution on blades in the same layer is almost paralel. The cooling rate in thin wal position of blade away from the nozzles is larger than that in tenon of the blade closer to the nozzles in the same layer. The cooling rate for blades in the second-layer is much lower both in thin wal and tenon for blades away from the nozzles. 相似文献
12.
13.
1 Introduction Commonly, a numerical model should be validated before application. Whether a simulation model for dendritic grain growth is reliable strongly depends on two aspects. 1) The model can effectively describe the anisotropy of grain growth. Th… 相似文献
14.
In this paper, delamination and delamination growth in a glass fiber composite used for the spar webs in wind turbine blades is investigated by optical coherence tomography (OCT). The cross-sectional and volumetric images clearly showed the microstructure and the crack within the specimen. After applying an optimized signal processing algorithm, 3D crack growth measured using OCT were demonstrated for the first time to the best of our knowledge. The crack structures inside the composite material at different stages during the delamination growth were revealed. 相似文献
15.
Steam generator (SG) tubing of pressurized water reactor in nuclear plants must be rapidly and accurately checked in order to detect defects in their early stages. In this paper, the authors present a multi-coil eddy current (EC) probe allowing both high speed inspection and circumferential localization of defects in the tube wall. A method of multi-coil EC signal processing, based on a continuous wavelet transform combined with a maximum likelihood diagnosis, is elaborated in order to enhance the detection performances and to provide automatic localization of defects. The inspection of SG tube samples shows good localization performances for defects as small as 10% deep, 15 mm long and 100 μm wide outer diameter notches, of both circumferential and axial orientations. 相似文献