压铸技术与装备的新发展

综述了压铸技术及其发展现状、镁合金及其成形技术、铝锌合金挤压成形技术、计算机在压铸领域中的应用、压铸新装备。     

铝合金零件半固态压铸技术应用研究

以水泵盖为目标零件,使用A357合金和新型铝合金Al-6Si-2Mg研究了半固态触变压铸过程中的工艺参数对零件最终性能的影响.通过对普通液态压铸机的改进和相关工艺参数的调整,进行了半固态触变压铸试验研究,得到了充型完好、组织均匀的水泵盖零件.     

镁合金真空低压消失模铸造新技术

介绍了一种新的铸造技术--真空低压消失模铸造的工作原理.建立了其在充型过程中的物理模型与数学模型,分析了其铸造工艺的特点及影响因素,以及在铸造高精度、复杂镁合金铸件方面的优势.作为压力铸造、低压铸造的补充,真空低压消失模铸造新技术在铸造高质量和高精度的镁合金铸件中具有广泛的应用前景,另外还可用于铸造高精度、复杂的铝合金铸件.展示了用该新技术铸造成形的复杂的电机壳体、排气管等镁合金铸件.     

压铸技术及压铸合金的发展与应用

简述了压铸发展的历史及压铸技术的发展状况。叙述了压铸铝合金、镁合金、锌和锌铝合金的研究开发与应用状况,分析了压铸合金有待进一步研究开发的问题     

Design and Verification of an Auxiliary System for High Vacuum Die Casting

Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this research.The model has an aggregate unit consisted of "vacuum pump + buffer tank" and a cylindrical container(including the shot sleeve,cavity and exhaust channel).The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume models.An auxiliary system for high vacuum die casting is designed based on the above analysis.This system is composed of a vacuum control machine and a new vacuum stop valve.The machine has a human-computer control mode with "programmable logic controller(PLC) + touch screen" and a real-time monitoring function of vacuum degree for buffer tank and die cavity.The vacuum stop valve with the "compressed gas + piston rod + labyrinth groove" structure can realize the function of whole-process vacuum venting.The new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly decreased.The systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.     

A study on manufacturing of aluminum automotive piston by thixoforging

The manufacture of many products related to the automobile and airplane industries by semi-solid forming is nowadays increasing from environmental and economical points of view. Especially in the automobile industry, to upgrade engine capability and reduce engine weight, the aluminum engine piston has already been developed by researchers and industrial technicians. Currently, forming methods to manufacture engine piston are casting, squeeze casting and hot forging. These methods, however, include several casting defects and need post machining as well. In this study, aluminum engine piston will be manufactured by thixoforging according to forming variables. In addition, it is very important to find the effects of forming variables on the final product by thixoforging. In order to determine the effects, however, researchers and industrial technicians have depended upon many experimental trials. In this study, a statistical approach for thixoforging has been adopted to improve experimental efficiency. Forming variables such as initial solid fraction, die temperature, and compression holding time were considered for manufacturing aluminum engine piston by thixoforging. Hardness and microstructure characterization were carried out so that the optimal forming condition could be found by the statistical approach. The experiment to make aluminum engine piston was performed under the optimal condition found by the statistical approach.     

Numerical simulation of mold filling and deformation behavior in rheology forming process

Rheology forming is a novel semi-solid processing method, which is different from traditional mold forging and conventional casting processes. The rheological behavior of metallic alloys containing both solid and liquid phases investigated the low and high solid fraction ranges. Rheology forming has several obvious advantages including its excellent forming ability resulting in the easier production of complex work pieces, more flexibility in shaping pieces, and more compact inner quality because of its high pressure. This research paper presents the theory of the rheology forming process and the results of a finite element simulation of rheology forming for aluminum alloys. The algorithms for both a single- and two-phase flow model, developed for this study, gives the die filling patterns, velocities, temperatures and solid fractions of the rheology material during the rheology process. To calculate the velocity and temperature fields, the respective governing equations corresponding to the liquid and solid regions were used. Therefore, the respective numerical models that take the co-existing solid and liquid phases within the rheology material into consideration have been developed to predict the defects of parts manufactured by the rheology process. This study compares of the velocity, temperature, and solid fraction between the single- and two-phase flow models. And, to predict the liquid segregation in the parts, the deviation of velocity between the liquid and solid regions in the two-phase flow model was analyzed.     

Incremental forming of Mg alloy sheet at elevated temperatures

In the present study, incremental forming of Mg alloy sheet at elevated temperatures was attempted with local heating apparatus. The device is composed of several halogen lamps and designed to move with forming tool for local heating in deformation zone. In order to investigate the influences of process parameters to incremental formability of AZ31 alloy sheet, a series of incremental forming tests of AZ31 for cone and pyramid type of simple models were carried out under various process conditions. Experiments were performed under various temperatures, feeding depth per cycle and inclination angles and the results were analysed.     

Magnesium and its alloys applications in automotive industry

The objective of this study is to review and evaluate the applications of magnesium in the automotive industry that can significantly contribute to greater fuel economy and environmental conservation. In the study, the current advantages, limitations, technological barriers and future prospects of Mg alloys in the automotive industry are given. The usage of magnesium in automotive applications is also assessed for the impact on environmental conservation. Recent developments in coating and alloying of Mg improved the creep and corrosion resistance properties of magnesium alloys for elevated temperature and corrosive environments. The results of the study conclude that reasonable prices and improved properties of Mg and its alloys will lead to massive use of magnesium. Compared to using alternative materials, using Mg alloys results in a 22% to 70% weight reduction. Lastly, the use of magnesium in automotive components is increasing as knowledge of forming processes of Mg alloys increases.     

半固态铸造技术研究的进展

半固态铸造是一种新的材料成形技术 ,采用半固态铸造技术成形可以实现产品的低成本、高产出及高质量。本文着重介绍了半固态铸造合金的坯料制备和成形方法 ,同时分析了搅拌速度和金属液冷却速度对一次相的影响 ,还对半固态合金微观组织的形成和演化以及充型过程数值模拟等进行了分析 ,提出了发展半固态铸造技术值得重视的问题     

A Study on Development of a Die Design System for Diecasting

Diecasting is one of the forming methods for manufacturing a large number of products with short lead time and a good surface by high injection pressure of cast alloy. Die design is composed of selection of cast alloy, design of product, runner and gate design, etc. In reality, however, die design for diecasting has been performed by a trial and error method, which causes economic and time loss. This paper describes the development of the computer-aided design of product and die design. The CAD system has been written in AutoLISP on the AutoCAD with a personal computer. In this study, the die design system for the die casting process has been developed and a flowchart is presented for the automation of die design, especially of the runner–gate system. As the generation process and die design system using 3D geometry handling are integrated with the technology of process planning, die design can be automated. In addition, specific rules and equations for the runner–gate system have been presented to avoid too much trial and error with expensive equipment. It is thus possible for engineers to make automatic and efficient die design for diecasting which will result in a reduction of the required cost and time. An example of a cap-shaped product, i.e. a motor pulley, is given using the proposed flowchart.     

压铸镁合金AZ91D摩擦磨损性能的研究

采用MM-200型磨损试验机，研究了干滑动摩擦条件下载荷和磨损时间对液态压铸成形镁合金AZ91D摩擦磨损性能的影响，借助扫描电镜探讨了材料的磨损机理。试验结果表明：当滑动速率为0．618m／s、载荷为20～250N时，液态压铸镁合金的磨损速率和摩擦因数均随着载荷的增大而增大，当载荷增大到250N之后，试样的磨损质量反而减小；随着磨损时间的增加，压铸镁合金的磨损质量损失呈线性比例增大，其摩擦因数在0．220～0．235范围内波动；T4和T6热处理对高载荷下镁合金材料的耐磨性能有一定的影响；随着载荷的增大，各种状态下镁合金材料的磨损机制均发生了由氧化磨损、剥层磨损、粘着磨损到熔化磨损的转变。     

电机零部件压铸成型质量控制方法研究

针对电机零部件压铸成形质量不高的问题,在分析主要成形缺陷来源的基础上,讨论了包括结合有限元数值模拟与现代优化理论进行的成形工艺参数优化,针对特定产品改进模具结构,提高铸件成形质量;并且,提出了应使用三维参数化设计,避免了重复的劳动,提高了生产效率。     

Machining parameters optimization on the die casting process of magnesium alloy using the grey-based fuzzy algorithm

The present investigation focuses on finding the optimal machining parameters’ setting for the die casting process of magnesium alloy using the grey-based fuzzy algorithm. This proposed algorithm, coupling the grey relational analysis with the fuzzy logic, obtains a grey-fuzzy reasoning grade to evaluate the multiple performance characteristics according to the grey relational coefficient of each performance characteristic. One of the real case studies performed in the die casting process, thin-walled cover components of liquid crystal display (LCD) panel, verifies that the proposed optimum procedure is feasible and effective. The casting density, warpage and flow mark of finished product are adopted to evaluate the machiniablity performances. Various die casting parameters, such as the die temperature, the pressure of injection, the plunger velocity (first and second stage) and the filling time are explored in the experiment. The table of orthogonal array is used in the experimental design. The response table, response graph and analysis of variance (ANOVA) are used to find the optimal setting and the influence of machining parameters on the multiple performance characteristics. Under the circumstances of the optimal machining parameters, the confirmation tests indicate the effectiveness of the proposed algorithm. Experimental results have shown that the required performance characteristics in the die casting process have great improvements by using this proposed algorithm.     

智能控制在模具温控成形中的应用

模具的温度控制和调节是高效而经济地生产高质量成形零件的必不可少的条件.介绍了智能控制在模具温控成形过程中的应用现状,指出数值模拟对温控成形过程温度场的研究有助于控制成形过程,实现对模具温度的智能控制,使零件的质量得到充分保证.     

大型注塑模浇注系统设计研究

大型模具在制造设计等方面与普通的中小注塑模具相比没有很大的区别，而且用CAE分析可以很好地解决模具制造中遇到的一些如成本高等问题，并且提高了大型注塑模具开发的成功率。     

铸辗复合成形法兰坯高温变形行为及加工图

环件铸辗复合成形工艺具有缩短工艺流程、高效和节能节材等优点,研究铸态环坯在铸辗复合成形工艺下的高温变形行为,揭示其组织演变机理,是实现材料在该成形工艺中成形与成性的关键。在不同变形条件下对砂型铸造和离心铸造Q235B法兰坯进行高温压缩试验,分析其流变应力的变化,推导出二者的本构方程。综合变形温度和应变速率对材料微观结构与性能的影响,建立基于动态材料模型的加工图。试验结果表明:二者的流变应力随着应变速率的增加和变形温度的降低而增大。离心铸造法兰坯的流变应力较低,动态再结晶易于发生,且功耗效率值及其变化幅度都要大于砂型铸造,表明了其显微组织变化剧烈,演变更加充分。结合二者的热加工图及其识别出的典型区域显微组织,获得了适合该法兰坯辗扩工艺的热力参数范围,离心铸造可为法兰坯铸辗复合成形工艺提供高质量的铸坯。     

压铸模具结构优选与设计系统开发

介绍了压力铸造成形原理及其工艺过程、剖析了压力铸造成形工艺的优点和存在的缺陷;总结了压力铸造技术的发展历史、应用范围及中国压力铸造生产产品应用领域的多元性,展示了中国压力铸造业发展的广阔前景。     

Novel technologies for the lost foam casting process

Lost foam casting (LFC) is a green precision casting process categorized as a near net forming technology. Yet, despite its popularity, it still suffers from some technological problems, such as poor filling ability of the castings, coarse and non-dense microstructure, low mechanical properties for the Al and Mg LFC processes, and defective carburization for the low carbon steel LFC process. These drawbacks restrict the development and widespread application of the LFC process. To solve these problems, the present study developed several novel LFC technologies, namely, LFC technologies under vacuum and low pressure, vibration solidification, and pressure solidification conditions; expendable shell casting technology; and preparation technology of bimetallic castings based on the LFC process. The results showed that the LFC under vacuum and low pressure evidently improved the filling ability and solved the oxidization problem of the alloys, which is suitable for producing complex and thinwall castings. The vibration and pressure solidifications increased the compactness of the castings and refined the microstructure, significantly improving the mechanical properties of the castings. The expendable shell casting technology could solve the pore, carburization, and inclusion defects of the traditional LFC method, obtaining castings with acceptable surface quality. Moreover, the Al/Mg and Al/Al bimetallic castings with acceptable metallurgical bonding were successfully fabricated using the LFC process. These proposed novel LFC technologies can solve the current technological issues and promote the technological progress of the LFC process.     

镁铝基耐热铸造镁合金的进展

总结了镁合金的蠕变特点和提高镁合金高温蠕变性能的措施,分析了现有Mg-Al基镁合金耐热性差的原因,综述了当前AZ,AS,AE,Mg-Al-Ca系耐热铸造镁合金的研究和应用状况并指出了以后的发展方向。