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建立变壁厚回字形结构多材质复合铸型,首先,通过对A356铝合金在多材质复合铸型的充型、凝固过程模拟仿真,获得多材质复合铸型铸件充型时间和温度场结果,锆英砂与石英砂、铬铁矿砂与石英砂过渡处凝固时间呈阶梯状递减;且锆英砂与石英砂过渡处及铬铁矿砂与石英砂过渡处铸件凝固时间更短,金属液凝固速度更快。其次,采用电子背散射衍射(EBSD)分析、电子显微探针(EPMA)分析对石英砂、铬铁矿砂、锆英砂复合铸型在重力铸造下A356铝合金铸件断口进行分析并进行抗拉强度测试。结果表明:在相同壁厚时,铬铁矿砂、锆英砂型铸件的晶粒尺寸细小,Al、Mg、Si等元素分布均匀、力学性能提高,断口呈现韧性断裂的特征;同时随着壁厚减小,同种材质砂型铸件晶粒细化、元素分布均匀、力学性能提高,断口呈韧性断裂特征。 相似文献
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消失模铸造生产的铸件具有尺寸精度高、表面光洁度好、铸件重量轻等优点,但对于形状较长、壁厚变化较大的壳体类铸件常存在铸件扭曲变形、壁厚不均匀等缺陷。以主离合器壳体为例,介绍了通过选用合适的粘接组合工艺及造型工艺生产出尺寸性能合格铸件的消失模铸造方法。 相似文献
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AbstractThis investigation was carried out to identify the major factors and their degree of influence on the dimensional accuracy of spheroidal-graphite iron castings produced in chemically- bonded sand moulds. Test castings were poured into furan-resin-bonded zircon sand and silica sand moulds and sodium silicate/ CO2 bonded silica sand moulds. A comparison of casting sizes with those of the mould cavity into which they were poured showed considerable scatter and overlap. From these data the size that each casting would have had, had it solidified without graphite formation, was calculated and found to depend on mould cavity size for each type of mould. By isolating the differences in casting size due to graphite it was possible to identify the influencing factors. Thus castings poured into furan-resin-bonded zircon sand have the highest contraction and their size depends primarily on the amount of graphite present. The dimensions of castings poured into silica sand moulds show more variation and depend not only on the amount of graphite present and the structure of the metal but also on the thermal expansion of the silica sand moulds. 相似文献
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简述了硅砂的高温膨胀过程,分析了其对铸铁件壁厚的影响,提出在浇注过程中砂芯的高温膨胀会使铸件的非加工壁厚减小。通过气缸体曲轴箱的浇注试验,证明了硅砂高温膨胀的存在,在工艺设计过程中增加壁厚补正量可以抵消砂芯表面的热变形,进而控制砂芯高温膨胀对缸体曲轴箱隔板非加工壁厚的影响。 相似文献
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研究在消失模铸造条件下,不同激冷能力的型砂对铝合金铸件组织和性能的影响,采用阶梯泡沫模试样在石英砂、铬铁矿砂、锆英砂等3种激冷砂型中浇注试验。结果表明,锆英砂和铬铁矿砂具有较好的激冷效果,得到的铝合金铸件组织细小,强度、硬度有较大的提高,为薄壁随型、质量优异的铝合金消失模模具制造提供了技术依据。 相似文献
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新型铬铁矿粉铸钢复合涂料的研究与应用 总被引:1,自引:0,他引:1
介绍了新型铬铁矿粉水基和醇基铸钢复合涂料的组成结构、生产工艺、性能特点和应用实例.新型铬铁矿粉复合涂料生产成本仅约锆英粉涂料的二分之一,可代替价格昂贵的锆英粉涂料生产无粘砂、气孔等缺陷,表面光洁的合金钢和碳钢铸件. 相似文献
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M Górny M Kawalec G Sikora H Lopez 《International Journal of Cast Metals Research》2016,29(1-2):68-73
This article addresses the effect of cooling rate and of titanium additions on the exhibited microstructure of thin-walled compacted graphite iron (TWCI) castings as determined by changing moulding media, section size and ferrotitanium. Various moulding materials were employed (silica sand and insulating sand ‘‘LDASC’’) to achieve different cooling rates. This study shows that the cooling rates exhibited in the TWCI castings varies widely (70–14 °C/s) when the wall thickness is changed from 2 to 5 mm. In turn, this is accompanied by a significant variation in the compacted graphite fraction. The resultant cooling rates were effectively reduced by applying an insulating sand in order to obtain the desired graphite compactness. Ti additions in combination with LDASC sand moulds were highly effective in promoting the development of over 80% compacted graphite in castings with wall thicknesses of 2–3 mm as evidenced by quantitative metallographic analyses. 相似文献
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N. W. Rasmussen R. Aagaard P. N. Hansen 《International Journal of Cast Metals Research》2013,26(6):355-363
The high number of successful green sand foundries working with vertical moulding equipment is the best proof of the advantages of this technology. It provides high productivity and accurate positioning of cores. It offers the freedom to design and produce with optimal functioning gating systems to secure good casting quality.The aim of the paper is to look into new ways of improving this successful casting technology. First a short introduction to the advantages of vertical moulding will be presented.The next subject is the advantages of utilising casting process simulation to optimise casting layout, gating and risering. Focus is on castings produced in the conventional way as well as on castings that are produced using the newly developed active feeding and active bottom filling technique.The last subject is to investigate if this new active feeding technique could be used for iron castings too. Experimental casting trials, as well as numerical simulation results, indicate that it is also functioning for iron castings; so the limiting factor will be the availability of robust equipment, which can keep up with the very fast vertical moulding machines. 相似文献
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The influence of the use of moulding sand with furan resin, prepared both with fresh sand and reclaimed matrix, on the formation of a flake graphite formation at the surface layer of ductile iron castings has been investigated. A series of experimental heats of ductile iron cast in moulds made of moulding sand characterised by different levels of surface active elements (sulphur, oxygen) were performed. The effect of the wall thickness and the initial temperature of the metal in the mould cavity on the formation of flake graphite in the surface layer of the casting is shown in the paper. Investigations carried out by means of scanning electron microscopy (energy dispersive X-ray spectroscopy and wavelength dispersive X-ray spectroscopy) showed concentration of gradient profiles of surface active elements in the castings surface layer, which are responsible for their quality. Finally, it has been shown that there exists a significant effect of the quality of the sand on the formation of the flake graphite layer and the surface characteristics of ductile iron castings. 相似文献
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In the present study, a processing technique for recycling investment casting ceramic shel waste was proposed to separate valuable refractory aggregate zircon sand. The microstructure and phase constituents of the shel waste and separation process were investigated. The results show that the characteristics of microstructure and phase constituents of the shel waste can meet the conditions for preferentialy separating zircon sand, and zircon sand can be separated by gravity separation on a shaking table. The separated zircon sand has good shape and high purity, and can be used for the production of castings and other applications. 相似文献
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This article addresses the effect of cooling rate on microstructure and mechanical properties as determined by changing molding media and section size. The research was conducted for thin-walled iron castings with 2-5-mm wall thickness and for the reference casting with 13-mm wall thickness, using different molding materials (silica sand and insulating sand “LDASC”) to achieve various cooling rates. Thermal analysis was performed to determine the real cooling rate at the beginning of the graphite eutectic solidification. In general, it was found that the predictions based on theoretical analysis of the solidification process of ductile iron are in good agreement with the experimental outcomes. Finally, the present study provides insights into the effect of cooling rate on the graphite nodule count, the ferrite fraction and mechanical properties of thin-walled ductile iron castings. The study shows that the cooling rate of thin-walled castings varies in a wide range (80-15 °C/s) when changing the wall thickness from 2 to 5 mm, accompanied by significantly changing the mechanical properties of ductile iron. The cooling rate can be effectively reduced by applying an insulating sand to obtain the desired properties of thin-walled castings practically in the whole range of ductile iron grades in accordance with the ASTM Standard. 相似文献
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在硅溶胶制壳工艺中面层耐火材料采用高铝钒土精铸砂(粉),粉液比控制在2.5~2.8之间时,生产的碳素钢、低合金钢精铸件表面粗糙度和尺寸精度可以与锆英砂(粉)结壳面层的铸件相当,而且可以大幅降低成本,节约资源. 相似文献
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对采用呋喃树脂自硬铬矿砂生产高铬不锈钢水轮机叶片铸件表面易出现"釉化"涂料层、界面型砂"釉化"烧结和粘砂缺陷进行了研究,并提出了解决措施.铸件粘砂的主要原因为钢液透过涂料层渗入铬矿砂,在界面发生氧化还原反应,将铬铁矿砂的铁还原出来,还原出的铁和砂粒形成致密混合物,并附着在铸件表面形成"釉化"烧结层.还原出的铁和铬渣以及砂粒中的未反应物,形成了致密的机械混合物,和铸件金属直接相连,附着在铸件的表面,形成粘砂.锆英粉涂料本身也和高铬钢发生微弱的化学反应.用新型添加剂及复合涂料改进型砂和替代锆英粉涂料,提高了钢液和铬矿砂界面涂料层的致密度、化学稳定性和耐火性,可以有效地解决这类问题. 相似文献
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根据壳型生产线十几年运行和各类覆膜砂应用的经验,对壳型铸造用覆膜砂的一些技术问题进行探讨。详细介绍适用于吹砂式多工位壳型机的湿态覆膜砂性能;高强度低树脂量覆膜砂的研制;湿态壳型覆膜砂的成形性指数与调湿工艺;翻斗法制壳时的脱壳问题分析和解决办法;覆膜砂脱壳性检测方法;高镍球铁件壳型铸造表面针孔原因分析与抗针孔覆膜砂的应用。 相似文献