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Study on Numerical Simulation of Mold Filling and Solidification Processes under Pressure Conditions
The mold filling and solidification simulation for the high pressure die casting (HPDC) and low pressure die casting (LPDC) processes were studied.A mathematical model considering the turbulent flow and heat transfer phenomenon during the HPDC process has been established and paralled computation technique was used for the mold filling simulation of the process.The laminar flow characteristics of the LPDC process were studied and a simplified model for the mold filling process of wheel castings has been developed.For the solidification simulation under pressure conditions,the cyclic characteristics and the complicated boundary conditions were considered and techniques to improve the computational efficiency are discussed.A new criterion for predicting shrinkage porosity of Al alloy under low pressure condition has been developed in the solidification simulation process. 相似文献
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液态模锻作为一种精密成型技术应用范围不断扩大,液锻件正在不断替代普通铸件和固态锻件用于各行各业。但液态模锻的材料范围不够明晰,导致铸造合金液态模锻研究与应用很多,而各种变形合金的液态模锻却鲜有报道。如果定义适于液态模锻技术成型的材料统称为液态模锻材料,并用流变充型能力、流变补缩能力以及开裂敏感性定量表征液锻材料的工艺性能,则各种合金钢、球墨铸铁、铝合金、镁合金、锌合金、铜合金、生物材料及金属基复合材料都属于液锻材料,且都具有较好的液锻工艺性能。目前只有液锻铝合金、液锻镁合金、液锻锌合金和一些液锻合金钢研究应用活跃,并取得了工业应用。建议今后加强液锻材料的工艺性能预报、变形合金特别是宽结晶温度范围合金的液态模锻以及金属基复合材料的研究开发。 相似文献
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目的 保证铸旋车轮短流程制造工艺的实现,提高旋压模具与同一轮型不同铸造毛坯的配合能力,防止因旋压后毛坯尺寸变化过大,造成车轮机加成品率下降的现象。方法 以某款车轮旋压模具为研究对象,对其旋压模具结构进行重新设计,增加定位滑块、垫板等设计,提高毛坯与模具的定位与配合,增强模具对毛坯的自适应性。结果 对改进后的旋压模具进行试验验证,新结构的旋压模具能够满足不同铸造毛坯的旋压,且控制上模压力在4.5 MPa内,毛坯尺寸合格,性能无影响。结论 该旋压模具设计的方法已经应用到了其他铸旋车轮的设计中。 相似文献
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《材料科学技术学报》2020,(4)
The pressure-driven mold filling ability of aluminum alloy melt/semi-solid slurry is of great significance in pressure casting processes, and the rheological behavior of the alloy has a crucial effect on the mold filling ability according to fluid dynamics. In this work, a pressure-driven mold filling model is first proposed based on the rheological behavior of the alloys. A356 alloy is employed as an example to clarify the rheological behavior of aluminum alloys, which obeys the power law model and is affected by temperature. The rheological behavior of the alloy in semi-solid state is modelled with the coupling of shear rate and temperature. The stop of mold filling attributes to the pressure loss which is caused by the viscosity during the flow of the melt/semi-solid slurry. Pressure loss caused by viscous flow and heat transfer between the alloy and the mold are calculated and coupled during the mold filling of the melt/semi-solid slurry. A pressure-driven mold filling model of aluminum alloy melt/semi-solid slurry is established based on steady-state rheological behavior. The model successfully predicts the filling length of melt/semi-solid slurry in pressure casting processes. Compared with the experimental results,the model can provide a quantitative approach to characterize the pressure-driven mold filling ability of aluminum alloy melt. The model is capable of describing the stop filling behavior of other aluminum alloys in pressure casting processes with corresponding rheological parameters and heat transfer coefficient. 相似文献
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镁合金压力充型与凝固过程的研究 总被引:18,自引:0,他引:18
研究了镁合金ZA91HP、AM50HP,AM20HP和铝合金AlSi9Cu3在高压力下的充型与凝固过程,结果表明,镁合金的充型能力比铝合金约低25%-50%;随铝含量的递减,三种镁合金的充型能力依次降低。数值模拟结果显示,镁合金在凝固发生之前具有与铝合金相同的充型能力。 相似文献
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目的 研究不同挤压铸造压力下所制备的6082铝合金的高温应力应变关系。方法 对100 MPa和50 MPa挤压铸造压力下制备的6082铝合金进行高温压缩实验,建立了相应的本构模型,并分析了挤压铸造压力和变形参数对流变行为和变形激活能的影响。结果 相同变形条件下,挤压铸造压力为100 MPa时,6082铝合金流变应力更高。当温度较高和应变速率较低时,两种不同的6082铝合金流变应力值差距明显缩小。挤压铸造6082铝合金的激活能随着变形温度和应变速率的增加而降低。结论 高挤压铸造压力下制备的6082铝合金变形激活能更大,变形更困难,但高温中低应变速率时,挤压铸造6082铝合金的变形难易程度相近。 相似文献
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为满足某发动机曲轴后端盖铸件高质量的外观与密封要求,针对该铝合金零件进行了高压铸造模具的浇注与排溢系统优化设计。首先根据铸件形貌和尺寸特征进行浇道、内浇口和排溢槽的理论设计,随后采用ProCAST软件模拟高压铸造充型、凝固过程,对铸件的卷气、缩松、缩孔及组织进行预测分析。研究发现,方案1的平直型横浇道浇注方案,金属液冲击型芯容易产生紊流和飞溅,且设置在铸件中间和下部的排溢系统不能减少紊流,易形成裹气和大的缩孔缺陷;而方案2为钳形浇道,去除方案1铸件中部的溢流槽并将下部连通溢流槽改为两个,明显改善铸件内裹气和缩孔现象,确定方案2为最终方案。试模铸件外观质量良好,经X射线探伤发现铸件无裂纹,厚大缩孔位置与缺陷仿真预测良好吻合;金相显微镜(OM)、扫描电镜(SEM)和电子背散射衍射(EBSD)观察组织发现,铸件晶粒细小、组织致密,晶粒取向差小,内部应力小,与组织和应力仿真结果一致;能谱分析(EDS)、X射线衍射(XRD)分析表明,铸件成分均匀,组织内部无杂质。本研究可为端盖类铝合金压铸件模具及工艺开发提供参考。 相似文献
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In the squeeze casting process, loaded high pressure (over approximately 200 MPa) and high temperature influence the thermo-mechanical behavior and performance of the used metal mold. Therefore, to safely maintain the metal molds, the thermo-mechanical characteristics (temperature and thermal stress) of metal mold in the squeeze casting must be investigated. In this paper, temperature and thermal stress distribution of steel mold in squeeze casting process were investigated by using a three-dimensional non-steady heat conduction analysis and a three-dimensional thermal elastic-plastic analysis considering temperature-dependent thermophysical and mechanical properties of the steel mold. 相似文献
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Squeeze casting of magnesium alloys and their composites 总被引:8,自引:0,他引:8
H. Hu 《Journal of Materials Science》1998,33(6):1579-1589
Squeeze casting, also known as liquid metal forging, extrusion casting and pressure crystallization, is a process in which molten metal soldifies in a die under an applied high pressure. The concept of squeeze casting was invented in Russia over 100 years ago. Later the process was exploited in North America, Japan and Europe to produce various automotive components. With the rapid expansion of magnesium applications in the automotive industry, the development of squeeze casting technology for magnesium alloys and their composites has been motivated by incentives to produce high-quality components. The present paper reviews recent progress in squeeze casting, and the effects of process variables on the cast structure and properties of magnesium alloys and magnesium-based composites. Approaches to optimization of the squeeze-casting process are discussed. The significant advantages of squeeze-cast magnesium alloys and magnesium-based composites are highlighted. The on-going research work at ITM is presented. 相似文献
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W. T. Carter Jr. R. M. Forbes Jones R. S. Minisandram 《Journal of Materials Science》2004,39(24):7253-7258
Nucleated casting is a method of casting metal below its liquidus temperature, casting as a semisolid rather than as a liquid. In nucleated casting, a stream of liquid metal is directed into a gas atomizer, which converts it into a spray and accelerates the spray droplets from the atomization zone toward a collection mold. Because of the high surface-to-volume ratio, high relative velocity, and a large temperature difference between the gas and droplets, the droplets lose heat very efficiently to the surrounding gas.Droplet diameter and process parameters such as gas-to-metal flow ratio, process rate, and spray distance have significant impact on the solid fraction of the metal at the collection zone. Small particles lose all of their heat of fusion and are fully solid when they strike; they will likely remelt in the semi-solid pool. Large particles are fully liquid when they strike. Medium-size particles are partially solid. When the particles strike the surface of the pool, a large number of nucleation sites are available for further solidification. Each nucleation site grows until it strikes an adjacent site and all local liquid is consumed and a fine-grained metallurgical structure results. When operated at high gas-to-metal ratio the semisolid will have small (<30%) fraction liquid, and free-form casting is possible. This process is commonly called spray forming. When operated at low gas-to-metal ratio the semisolid will have a high (>75%) fraction liquid, and a mold is required to contain the metal as it continues to solidify. This process is termed nucleated casting.Alloy 718 metal has been cast in a prototype nucleated casting system for demonstrating the feasibility of the new process. Metallographic examination shows that the as-cast material possesses a uniform, equiaxed 0.075 mm (ASTM 4.5) grain structure. Macrosegregation-related defects were not found in the casting or in forgings that were obtained from the ingots. 相似文献
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Young-Chan Kim Chang-Seog Kang Jae-Ik Cho Chang-Yeol Jeong Se-Weon Choi Sung-Kil Hong 《材料科学技术学报》2008,24(3):383-388
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. 相似文献
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运用有限元分析软件ANSYS对薄壁铝合金压铸件的压铸过程进行温度场数值模拟分析,研究了浇注温度、模具预热温度对温度场分布的影响,分析了热应力集中的位置,从而有效控制了铸件因热应力引起的体积收缩,保证了铸件质量及其精度,优化了压铸工艺参数,为压铸模具的热应力分析奠定了基础。 相似文献
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目的 对某铝合金汽车转向节的精密铸造工艺进行设计与优化研究,以得到合格的铝合金汽车转向节的精密铸造工艺方案。方法 结合铝合金转向节铸件的结构特征、铸件材料特性和铸造经验,在转向节铸件主体部和鹅颈部各开设一个内浇口,设计了铝合金转向节初始浇注方案;通过在初始工艺方案中铸件缺陷较严重的区域设置补缩冒口、在铸件顶部增设排气道等措施给出了铝合金汽车转向节的优化浇注方案,基于ProCAST软件建立了铝合金转向节精密铸造2种浇注方案的有限元模型,对铝合金转向节精密铸造的充型过程、凝固过程及缩孔缩松特性进行了数值模拟与分析。结果 铝合金转向节铸件初始浇注方案的充型过程相对稳定流畅,铸件在凝固过程中有孤立液相区的形成,完全凝固后铸件中间部位存在大面积缩松缩孔缺陷;优化浇注方案能够控制金属液的流动、充型顺序及凝固特性,铸件的整个凝固过程基本呈中间对称分布,最后凝固区域位于补缩冒口内部,最大缩孔缩松率控制在2%以下。结论 优化浇注方案的设计合理且有效,能够有效地消除铝合金转向节铸件的缺陷。 相似文献
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目的 针对铝铜合金热裂敏感性高、难以进行金属型铸造的难题,研究其合金成分、铸造工艺、组织与性能的关系。方法 首先充分分析铸造铝铜合金的凝固机制与特点,在ZL205A合金基础上,设计了新型合金成分以及两种铸造试样模,经过熔炼、铸造与热处理,获得砂型铸造与金属型铸造试样,进行力学性能测试、组织分析,并观察试样的抗热裂性。结果 两种铸造试样都获得了较高的力学性能,铸态及T6态全部为等轴晶组织,成功避免了热裂问题,并提高了合金的力学性能;金属型铸造试制了油马达铸件。结论 证明了通过铝铜合金的成分优化设计,以及含钪复合细化剂的合理匹配,采用金属型铸造获得等轴晶组织,进而避免粗大枝晶组织,是克服热裂问题的关键,从而实现金属型铸造高强度铝铜合金。 相似文献