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1.
Research on the Effect of Pouring Temperature on Hot-Tear Susceptibility of A206 Alloy by Simulation
Mohamad Reza Nasresfahani Mohamad Javad Rajabloo 《Metallurgical and Materials Transactions B》2014,45(5):1827-1833
Cast alloys with wide solidification ranges are prone to hot tearing. This study deals with prediction of hot tearing location and its intensity by computer simulation. The simulation was performed at different pouring temperatures on A206 aluminum alloy. As superheat increases, the critical fraction solid time increases which means the alloy is more susceptible to hot tearing. These theoretical predictions are in complete accordance with experimental results. 相似文献
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薄板坯连铸结晶器铜板温度及热流密度分布 总被引:5,自引:1,他引:4
薄板坯连铸结晶器的传热过程直接影响到铜板的寿命,有必要研究薄板坯连铸结晶器的传热特征。为了研究薄板坯结晶器的热流密度,通过开发的结晶器温度监测软件检测了珠钢结晶器铜板的温度。根据在线实测的铜板温度以及薄板坯连铸机冷却参数,建立了薄板坯结晶器铜板传热模型,计算并验证了结晶器热流密度的分布函数,同时通过二次回归得出了结晶器热流密度与结晶器高度的关系式。结果表明,在宽度方向上铜板温度和热流密度的分布具有相似的规律性,距离弯月面越近,热流密度和温度的波动越大。弯月面处热流密度值大于4.2MW/m^2,是造成结晶器铜板被侵蚀的主要原因。 相似文献
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通过测试溜槽中不同温度下铝熔体中氢含量,发现铝中氢含量随着铸造温度升高而升高,每升高1℃,铝中氢含量约升高0.013mL/100gAl;铸造开始时铝中氢含量高于铸造过程铝中氢含量。 相似文献
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Marcin Górny 《钢铁研究学报(英文版)》2012,19(8):52-59
It has been shown that it is possible to produce thin wall ductile iron (TWDI) castings of considerable length using an Archimedes spirals with a wall of 1, 2 or 3 mm in thickness. The fluidities for different moulding materials [(classical mould, chemically bonded silica sand and chemically bonded low-density alumina-silicate ceramic sand (LDASC)], chemical composition, and pouring temperature were estimated. There is a significant temperature drop in thin sections (contrary to typical sections) during the mould filling. A profile of real temperature drop is presented along with theoretical predictions. The high temperature drop of liquid iron results in an increased cooling rate (before the eutectic equilibrium solidification temperature), which in turn affects the solidification and microstructure of TWDI castings. Microstructures were characterized quantitatively using an image analyser. Structure parameters for different wall thicknesses and moulding materials (graphite nodule count, ferrite and cementite fraction) are plotted, which is versus distance from the entrance to the mould cavity. It has been shown that the thin wall castings have a gradient structure. Moreover, a strong influence of LDASC sand (material with low ability to absorb the heat) on the structure parameters of TWDI castings is presented. 相似文献
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罗维云 《有色金属材料与工程》1991,(2)
采用“罗90—1”表面处理涂料的结果表明:操作方便,导热性好,高温不氧化,透气性强,结合不易剥落,表面光洁,保温及润滑性好,能保证金属液应有的流动速度,不需专用工具清砂。基本上解决了原紫铜及铜合金铸件表面或表层质量差的问题,从而使铜铸件表面或表层质量在原75%的基础上再提高20%。 相似文献
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以提高结晶器使用寿命和铸坯表面质量为目标,通过建立漏斗区自有锥度、结晶器总锥度和结晶器局部锥度的计算模型,研究了漏斗区的宽度和深度、窄边铜板偏移量以及磨损对结晶器锥度沿高度方向分布的影响,提出了漏斗区自有锥度和局部锥度沿高度方向分布应与铸坯的凝固收缩相匹配的设计理念,对薄板坯连铸结晶器宽面铜板内腔形状及窄边锥度调控工艺进行了优化设计,为结晶器操作工艺及管理制度的优化提供了理论依据。基于上述研究工作,研发了适合于FTSC工艺的新型结晶器,进行了大量的工业生产试验。结果表明:在浇注宽度为1 520mm的铸坯时,窄边附加偏移量可由12mm降低到7mm,窄边铜板的使用寿命得到了大幅度的提高,过钢量为2.25万t后,窄边铜板最大磨损量由5mm降低到2mm以下;新型结晶器有效控制了铸坯窄面凹陷和表面纵裂纹的发生。 相似文献
7.
高温合金表面激光熔铸镍基合金涂层的组织与耐磨性能 总被引:8,自引:0,他引:8
研究了高温合金GH33表面激光熔铸镍基合金涂层的组织和耐磨性能。结果表明,基材对涂层合金的稀释作用较小;涂层与基材之间形成良好的冶金接合;涂层基体组织为γ-Ni枝晶,枝晶间为γ-Ni、M23(CB)6、Ni3B、Cr2B、CrB、WC等;涂层耐磨性能的平均值较基材提高4倍以上。 相似文献
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The objective of this research was to examine melt filtration of AZ91E magnesium alloy permanent mould castings using experimental trials and predict filtration using a commercial software package. Tensile specimens were prepared using a H13 tool steel permanent mould machined to ASTM-B108 standards. The mould and pouring temperatures were 500 and 720?°C, respectively. Without a filter, the average yield strength, tensile strength and elongation were 89.6, 153.9?MPa and 2.41?% respectively and these increased to 96.5, 167.0?MPa and 3.05?% respectively with the use of a steel mesh filter within the well of the mould. Filters enabled removal of MgO based oxides. Modelling using commercial software demonstrated that the use of filters reduced turbulence in the metal stream minimizing oxides, which are essentially sites for stress concentration. The results of the research are important for the development of processing methods to improve the melt cleanliness of magnesium alloys for automotive and aerospace industries. 相似文献
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薄板坯连铸结晶器的热性能和机械性能的分析 总被引:2,自引:0,他引:2
1 前 言目前 ,炼钢工业中一个最重要的发展趋势是开发近终形连铸钢坯的工艺。浇注厚度仅为几个厘米的薄板坯 ,用常规的精轧机在线进行直接热轧 ,这种先进的连铸工艺避免了使用粗轧机及其相应的投资。结晶器是薄板坯铸机中最重要的组成部分 ,因为在浇注过程中 ,结晶器铜板控制着钢液的初始凝固过程 ,决定着铸坯的表面质量。在操作过程中 ,虽然由于急剧的热梯度引起的结晶器变形较小 ,但会影响凝固坯壳和结晶器之间气隙的大小 ,从而制约着热传递。伴随的热应力可能引起结晶器弯月面附近永久的蠕变变形 ,影响结晶器的使用寿命。所以 ,在严格… 相似文献
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Flow instability in continuous thin slab casting moulds has been studied using a full scale water model with particle image visualization. The results show that jet impinging depth, circumfluence centre position and wave height are unsteady and periodical. The probabilities of jet impinging depth and circumfluence centre position seem to be Poisson distributions with the highest frequency near the average position. The flow pattern is asymmetrical for a short time and the phase difference of jet impinging depth, circumfluence centre position and wave height on the two sides of the mould centreline is half a period. The average jet impinging depth, average circumfluence centre position, average meniscus wave profile and the highest and lowest meniscus positions are generally symmetrical to the mould centreline. 相似文献
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A three‐dimensional (3D) numerical model has been employed to predict the local temperature and heat flux distribution on the funnel‐shaped Flexible Thin Slab Casting (FTSC) H2 mould plate®. The modelling was combined with in‐plant temperature measurements from thermocouples installed in the mould. For the measurements the thermocouples are arranged to be adapted to the funnel‐curved shape of the mould such that the spatial locations of measured temperature data sets from the thermocouples can be regarded to form a plane. The method divides the geometry of the mould plate into two computational domains along the measured temperature plane in order to utilize the data as the boundary condition by interpolation. The measured data are compared with those obtained by the average heat flux and one‐dimensional (1D) heat conductivity model in the thermal analysis of the mould plate. It is found that the assumption of average heat flux only along the longitudinal direction, used in conventional billet or slab moulds, is not satisfactory to describe the heat transfer of the complex funnel‐shaped mould in the longitudinal and transverse direction. The heat flux values and hot face temperature in funnel‐shaped mould plates obtained by the 3D model are lower in comparison to the 1D model. The structure of cooling water channels has a significant influence on the uniformity of the heat flux. Some fluctuations of heat flux and temperature occur in the junction between the parallel‐curved and funnel‐curved zone along the longitudinal and transverse direction for the present case. It is expected that by utilizing the measured temperature data, the present model can be helpful to understand the thermal behaviour and define the thermal boundary condition of the funnel‐type mould plate. 相似文献
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通过对不同助熔剂加入量下连铸保护渣熔化温度的研究,得出助熔剂对保护渣熔化温度的影响规律,对其机理也进行了深入的讨论。 相似文献
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通过热丝法得出保护渣连续冷却转变(CCT)和时间-温度转变(TTT)曲线,并用偏光显微分析和X-射线衍射分析方法研究了萤石含量(8%~16%)对碱度1.0的薄板坯连铸结晶器保护渣结晶性能的影响。结果表明,萤石含量每增加2%,保护渣的临界冷却速度平均增加2.5℃;同一冷却速度下,随保护渣中萤石含量的增加,结晶温度升高,结晶率增大,有利于提高界面热阻,控制渣膜传热,减少铸坯表面裂纹产生;因萤石含量超过14%时,渣膜中大量生成结晶矿物枪晶石,对连铸润滑要求较高的钢种,应控制萤石含量≤14%。 相似文献
18.
《Canadian Metallurgical Quarterly》2013,52(5):387-396
AbstractIn semi-continuously cast slabs of precipitation-hardened copper alloy, internal cracks are often observed after homogenization, although those defects can not be found out after casting. It is considered that, before stress relief takes place during homogenization, thermal stresses generated in the slab during casting will exceed the fracture stress. It is of interest to understand how internal stresses of slabs will affect the fracture during homogenization. Fracture temperatures of the material under static tensile stresses are investigated in an attempt to demonstrate the fracture evolved during homogenization. © 2000 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved. Résumé Dans les brames d'alliage de cuivre durci par précipitation et coulées en semi-continu, on observe souvent des fissures internes après homogénéisation, bien qu'on ne trouve pas ces défauts après la coulée. On considère que les ontraintes thermiques générées dans la brame lors de la coulée vont excéder la contrainte de rupture lors de l'homogénéisation, avant que l'effet de relaxation puisse se produire. Il est intéressant de comprendre de quelle manière les contraintes internes des brames affecteront la rupture lors de l'homogeneisation. On a etudie les températures de rupture du matériel sous contraintes statiques en traction dans une tentative de démontrer que la rupture a évolué lors de l'homogénéisation. © 2000 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved. 相似文献
19.
利用COMSOL对TC4表面激光熔覆制备CoCrNiMox及CoCrNi(WC)x高熵合金涂层的熔化与凝固过程的温度场进行模拟,建立了三维多物理场并存的瞬态模型,同时考虑了传热、流体传热、对流以及表面熔覆层生长过程,分析对比了扫描速度、激光功率等参数对添加不同含量Mo及WC的CoCrNi基合金温度场的影响。通过模拟结果可以得知,激光熔覆过程中熔池的主要驱动力为马兰戈尼力,提高Mo含量时会使涂层温度场的最大值降低,但同时速度场和压力场的最大值会上升。此外,使用CoCrNiMo2作为涂层粉末相比于熔覆CoCrNi(WC)2,会在温度场、速度场和压力场均观察到较低的数值;激光功率逐渐升高,激光熔覆产生的熔池的中心温度也随之升高,且熔池的宽度、深度也将有所升高;扫描速度逐渐升高时,熔池中心最高温度显著降低,熔覆层起始位置明显推迟,熔覆层厚度明显减少,熔池的几何尺寸变小且熔池底部形貌对称性变差。 相似文献