Modeling of Mold Filling and Solidification in Lost Foam Casting

Based on the characteristics of the lost foam casting (LFC) and the artificial neural network technique, a mathematical model for the simulation of the melt-pattern interface movement during the mold filling of LFC has been proposed and experimentally verified. The simulation results are consistent with the experiments in both the shapes of melt front and filling sequences. According to the calculated interface locations, the fluid flow and the temperature distributions during the mold filling and solidification processes were calculated, and the shrinkage defect of a lost foam ductile iron casting was predicted by considering the mold wall movement in LFC. The simulation method was applied to optimize the casting design of lost foam ductile iron castings. It is shown that the model can be used for the defects prediction and for casting design optimization in the practical LFC production.     

Effect of Process Parameters on Porosity in Aluminum Lost Foam Process

1.IntroductionLost foam casting process is still a new technology,and is gaining confidence among manufacturers[1].It isexpected to dramatically improve the competitiveness ofthe foundry industry.Many advantages like eliminatingmachining steps,making complex casting without coresand reducing environmental loads can be offered by thisprocess,because molding binder is not added into themold of the lost foam process.Aluminum alloy castings are widely used in the auto-mobile and aerospace industri…     

铸铁模消失模铸造过程数值模拟及组织性能研究

运用View cast对所设计的铸铁模消失模铸造工艺进行数值模拟,预测工艺方案所产生的缩孔、缩松的大小和位置。模拟结果显示,铸件实现了顺序凝固,无明显缩孔、缩松缺陷。此外,铸件设置加强肋保证了铸铁模在使用过程中不会因冷热交变产生挠曲变形。利用消失模铸造生产的铸铁模组织以针状铁素体和珠光体为主,加热至500℃、700℃,试样组织和硬度没有明显变化,加热至900℃时发生了铁素体向奥氏体转变,冷却后生成均匀分布的珠光体以及细小的铁素体。氧化实验分析发现,温度对试样的氧化速率有较大影响,主要是因为不同温度下试样表面生成不同的氧化膜,使试样的氧化速率有较大的差异。     

台车消失模铸造过程数值模拟及组织性能研究

运用View cast模拟软件对烧结机台车消失模铸造过程进行数值模拟,预测铸造工艺所产生的缩孔、缩松的位置和大小。模拟结果表明,铸造工艺实现了铸件的顺序凝固,铸件没有产生缩孔、缩松等缺陷,铸件组织致密,符合技术要求。观察材料的组织发现,铸态组织主要以铁素体、珠光体以及球状石墨为主,加热至500℃、700℃组织和硬度没有发生明显变化;当加热至900℃时发生相变,产生破碎状铁素体和网状铁素体,硬度显著增大。氧化实验分析发现,温度对试样的氧化速率有较大的影响,主要因为不同温度下试样表面生成不同的氧化膜,使试样的氧化速率有较大的差异。     

TMF criteria for Lost Foam Casting aluminum alloys

The purpose of this paper is to define a thermo‐mechanical fatigue criterion in order to predict the failure of aluminum alloys components issued with the lost foam casting process and used in particular in the automotive industry. The microstructure of the studied materials (A356–A319 aluminum alloys) is clearly affected by the lost foam casting process which can directly affect the mechanical properties, the damage mechanisms and the fatigue failure of specimens and components. The major problem in defining a predictive fatigue criterion in this case is the fact that it should be applicable for the component which is submitted to complex multiaxial thermo‐mechanical loadings. Since many years, energy‐based criteria have been used to predict fatigue failure of this class of materials. Then, different energy‐based criteria are tested in order to take into account different types of triaxiality and mean stress effects corrections. The fatigue lifetime results predicted by both of them show a good agreement with experimental results.     

镁合金消失模铸件表面膜成分及其结构

采用X射线光电子能谱技术(XPS)对消失模镁合金铸件的表面成分进行了测定,结果表明消失模镁合金铸件表面元素成分为Mg、Al、C、O、Si;结合对镁合金液和消失模样界面间的化学反应分析,揭示了消失模镁合金铸件表面是由MgO、Al2O3、SiO2和无定型C等组成的一层薄膜,即消失模镁合金铸件表面的Al2O3-SiO2-MgO-C复合膜;该复合膜对提高镁合金表面的防腐蚀性有很好的作用;提出了镁合金消失模表面膜的结构模型.这些结果表明,消失模技术作为镁合金零件的成形方法具有独特的优势.     

Transport Phenomena in the Production and Use of Expanded Polystyrene Patterns in Lost Foam Casting

Experiments were carried out to study the effect of process and design variables on defect formation in the lost foam casting process. Emphasis was placed on the production of expanded polystyrene foam patterns and the use of these patterns to create desired castings. Spatial pattern density variation caused by varying the fill and canister pressure for molds with varying distance between injector and opposing wall was measured. The heat transfer coefficient and gas pressure in the gap between the metal front and the foam pattern were also measured. The study found a close correlation between the production of a uniform pattern and the production of a defect-free casting.     

石膏型渗流法制备低密度开孔泡沫铝工艺研究

研究用可溶石膏型预制块制备低密度开孔泡沫铝的工艺。采用不同孔径的聚氨酯网状海绵为母体材料,用石膏粉、硫酸镁、铝矾土和水为配方制备石膏型预制块,并分析了硫酸镁和铝矾土的加入量对石膏型预制块可溶性和抗压强度的影响。通过加压渗流的方法制备出低密度的开孔泡沫铝,并对渗流参数的选择做出总结。结果表明:利用石膏型渗流法制得的开孔泡沫铝相对密度在0.1以下。     

泡沫铝冶金连接及其界面结构与力学性能研究

以Zn-10Al合金作为粘结合金,采用功率超声辅助的热浸镀法进行泡沫铝板的冶金连接,采用光学显微镜(OM)和扫描电镜(SEM)观察接头组织及界面结构,采用X射线能谱仪(EDS)测定界面处元素分布,对样品进行拉伸实验和摆锤冲击实验,并与无功率超声辅助样品和胶接样品比较。功率超声辅助冶金接头密实连续,Zn、Al元素相互扩散,在界面处连续分布;无功率超声辅助接头中存在大量气孔等缺陷。功率超声辅助冶金接头的拉伸性能和冲击性能均优于无功率超声辅助接头和胶接接头。在功率超声辅助下进行连接时,其空化作用和声流能较彻底地破除泡沫铝基体表面的氧化膜,同时能够促进组织均匀化、去气除杂,有利于形成良好的冶金结合和致密的冶金接头。     

铝(镁)合金消失模铸造近净成形技术研究进展

阐述了铝(镁)合金消失模铸造技术的研究现状,着重介绍了铝(镁)合金消失模铸造在金属液充型、振动凝固、压力凝固以及消失模壳型铸造等技术方面的最新研究进展。研究表明,铝(镁)合金在消失模铸造过程中,需重点解决针孔、缩松等缺陷,提高液态合金的充型能力和铸件的力学性能;通过采用振动凝固和压力凝固的手段,可以提高金属液充型能力、细化组织、提高组织致密性,明显提高铸件力学性能。真空低压消失模壳型铸造技术,可以解决普通消失模铸造易于出现的孔洞和夹杂等缺陷以及浇不足和浇注温度高等问题,是一种生产复杂薄壁高质量铝、镁合金精密铸件的新方法。     

Die Casting Mold Design of the Thin-walled Aluminum Case by Computational Solidification Simulation

Recently, demand for the lightweight alloy in electric/electronic housings has been greatly increased. However, among the lightweight alloys, aluminum alloy thin-walled die casting is problematic because it is quite difficult to achieve sufficient fluidity and feedability to fill the thin cavity as the wall thickness becomes less than 1mm. Therefore, in this study, thin-walled die casting of aluminum （Al-Si-Cu alloy： ALDC 12） in size of notebook computer housing and thickness of 0.8 mm was investigated by solidification simulation （MAGMA soft） and actual casting experiment （Buhler Evolution B 53D）. Three different types of gating design, finger, tangential and split type with 6 vertical runners, were simulated and the results showed that sound thin-walled die casting was possible with tangential and split type gating design because those gates allowed aluminum melt to flow into the thin cavity uniformly and split type gating system was preferable gating design comparing to tangential type gating system at the point of view of soundness of casting and distortion generated after solidification. Also, the solidification simulation agreed well with the actual die-casting and the casting showed no casting defects and distortion.     

涂料性能对干砂消失模铸造铝合金充填能力影响的研究

本文研究了涂料的保温性和透气性对铝合金千砂消失模铸造充填能力的影响。涂料的保温性和透气性均严重影响铝合金的有效充填能力;仅有高保温性或高透气性的涂料不能提高合金的有效充填能力;只有当涂料的保温性和透气性有恰当匹配关系时,才可以获得良好的有效充填能力。     

泡沫铝合金渗流铸造工艺的试验分析EI

采用正交实验方法 ,选择三种不同粒径的填料 ,系统研究了粒子预热温度、金属液浇注温度和充型压力对渗流铸造泡沫铝合金成型工艺的影响 ,并对试验结果作了理论分析。认为 ,合理选择粒子预热温度是生产泡沫金属铸件的前提 ,适当提高浇注温度是保证泡沫组织均匀良好的关键 ,保持适度的充型压力有利于提高材质通孔率和工艺稳定性。     

显微共晶偏析对ZL205A合金力学性能的影响

对ZL205A合金中显微共晶偏析按轻重程度进行了分级,研究了各级偏析对试样室温力学性能的影响,并对试样断口进行了分析.结果表明:ZL205A合金Ⅰ级偏析对该合金试样室温力学性能无明显影响,满足一般力学性能(切取)设计使用要求;与Ⅰ级偏析相比,Ⅱ级偏析对合金试样室温力学性能有影响,其合金σb,σ0.2和δ5值分别下降了1%,3%和52%,主要表现为对延伸率影响程度较大.     

Microstructure and Mechanical Properties of Hyper-eutectic Al-Si Alloys Fabricated by Spray Casting

Microstructure and mechanical properties of hyper-eutectic Al-Si alloy fabricated by spray casting were in- vestigated and then these results were compared with those by squeeze cast.The spray-cast specimen was found to have finer Si particles （～5μm） compared to the squeeze-cast specimen （10-25μm）.The tensile strength and elongation of the spray-cast specimen are also higher than those of the squeeze cast one.It was considered that the increased mechanical properties of the spray-cast specimen were mainly due to finer size of the Si particles distributed in Al matrix.     

微量 Sc 对高强铝合金铸态组织性能的影响

目的研究Sc对某7系铝合金铸态组织性能以及对合金主要元素分布情况的影响。方法在某7系铝合金中添加微量Sc,采用金相显微镜、硬度测试等实验方法,研究了合金铸态组织与性能;通过SEM和EDS分析了合金主要元素分布情况。结果添加0.2%的Sc的合金,晶粒尺寸从106μm细化到41μm;Sc的添加使硬度得到了一定程度的改善,增大了Cu元素的枝晶偏析,而对合金基体中Zn和Mg等合金元素枝晶偏析影响不大。结论添加微量Sc,可以得到细小、圆整、均匀的铸态组织,合金主要元素的分布也得到改善。     

固化条件对热塑增韧环氧树脂的固化动力学和相分离的影响EI

采用砂型和金属型两种不同铸造方法对铸态、固溶态和时效态ZL210A合金性能及断口形貌的影响进行研究.结果表明:对ZL210A铸造合金而言,金属型铸造方法优于砂型铸造方法,其常规力学性能σb,σ0.2和δ5均高于砂型铸造,从断口形貌上看,试样断口形貌均呈现典型的穿晶断裂,且韧窝较深.其中,金属型固溶态试样的断口韧窝最为明显,呈现出较好的韧性.     

相对密度对球体开孔泡沫铝压缩及吸能性能的影响

目的研究球体开孔泡沫铝的相对密度在准静态压缩过程中对球体开孔泡沫铝压缩性能和吸能性能的影响。方法对准备的3种不同相对密度的泡沫铝试样进行准静态压缩试验。结果利用相关软件绘制出不同相对密度球体开孔泡沫铝试样的实验曲线,由分析试验曲线可知,当泡沫铝的相对密度从0.35提升到0.392时,球体开孔泡沫铝的屈服强度虽增加了3.2MPa,但吸能效率的最大值下降了近2.4%。结论随着泡沫铝相对密度的提高,其压缩性能越高、抗压强度越高。在同等应变下,高密度泡沫铝比低密度泡沫铝的吸能性能好。泡沫铝相对密度越大,吸能效率的最大值越小,理想吸能效率的最大值也越小。     

闭孔泡沫铝压缩性能研究

闭孔泡沫铝作为一种新型多孔金属材料,被应用于各个领域,但其压缩力学性能受到孔隙率、孔洞结构参数、相对密度及材料基本力学性能等的影响,因此针对某闭孔泡沫铝企业研究出的一款新型产品,在确定其相关参数后进行10组试样的压缩力学试验,确定其应力-应变曲线,分析各段曲线意义和产生机理,并针对其特有的压缩力学性能,研究在外力作用下的吸能表现,为该型号的闭孔泡沫铝材料在各个行业中的应用提供技术支持和参考依据。