Characterization of A390 aluminum alloy produced at different slow shot speeds using vacuum assisted high pressure die casting

The effects of vacuum assistance on the microstructure and mechanical properties of high pressure die cast A390alloy at different slow shot speeds were evaluated.Plate-shaped specimens of hypereutectic A390aluminum alloy were produced on a TOYO BD?350V5cold chamber die casting machine incorporated with a self-improved TOYO vacuum system.According to the results,the vacuum pressure inside the die cavity increased linearly with the increasing slow shot speed at the beginning of mold filling.Meanwhile,tensile properties of vacuum die castings were deteriorated by the porosity content.In addition,the average primary silicon size decreased from23to14μm when the slow shot speed increased from0.05to0.2m/s,which has a binary functional relationship with the slow shot speed.After heat treatment,microstructural morphologies revealed that needle-shaped and thin-flaked eutectic silicon particles became rounded while Al2Cu dissolved intoα(Al)matrix.Furthermore,the fractography revealed that the fracture mechanism has evolved from brittle transgranular fracture to a fracture mode with many dimples after heat treatment.

Microstructures and mechanical properties of AZ91D magnesium alloy processed by low pressure die casting

AZ91D alloy components were cast by low pressure die casting (LPDC) process. The mechanical properties of cast components with different microstructural features (shrinkage and distribution of Mg17Al12 second phase) were investigated under as-cast states. Compared with gravity casting, AZ91D with LPDC has much coarser grain size and second phases(Mg17Al12 and Al8Mn5). The different size and distribution of Mg17Al12 phase and shrinkage correspond to different mechanical properties. The ultimate tensile strengths and elongations are mainly decided by the content and distribution of shrinkage porosity, while the yield strengths are determined by the percentage and distribution of Mg17Al12 phase. The more and finer Mg17Al12 phase in the alloy, the relatively higher the yield strengths are. In the alloy without shrinkage, the mechanical properties are mainly determined by the size and distribution of Mg17Al12 phase. The finer Mg17Al12 phase, the better the mechanical properties are. Under optimal process, the density and mechanical properties of LPDC AZ91D are improved with fine microstructures.

Effect of vacuum on porosity and mechanical properties of high-pressure die-cast pure copper

Pure copper tensile bars were produced by conventional die casting(HPDC) and vacuum-assist die casting(VADC) processes. Porosity and mechanical properties were investigated by using optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), X-ray computed tomography(XCT) and tensile tester. Results show that porosities including gas porosity and shrinkage porosity could be observed in copper castings. Since the application of vacuum could reduce filling related gas entrapment and facilitate solidification due to the increased heat transfer between metal and die, both number and size of the entrapped gases, as well as shrinkage porosities were significantly reduced in vacuum-assist die castings of pure copper. The porosity fraction decreased from 2.243% to 0.875% compared with that of the conventional die casting. Besides, mechanical properties were improved significantly, i.e., by 15% for ultimate tensile strength and three times for elongation.

Principles and practice of low pressure-expendable pattern casting process for magnesium alloys

A newly developed low-pressure expendable pattern casting (LP-EPC) process was introduced and its basic principles or effect factors were further analyzed. According to theoretical calculation and experimental results, the major casting parameters that are of great and critical importance on the process include pressure and flux of filling gas, decomposition characteristic and density of foam pattern, thickness and permeability of coating, pouring temperature, vacuum degree and their combination. Most of casting defects can be effectively avoided by choosing the suitable parameters. The success achieved in pouring motor housing and exhaust manifold castings demonstrates the advantages of LP-EPC process in the production of high-complicated castings with high dimension accuracy.

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 parallel 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.

Characterization of the Grain Structures in Vacuum-Assist HighPressure Die Casting AM60B Alloy

The structures in vacuum-assist high-pressure die casting （HPDC） AM60B alloy were studied by using an optical microscope and a scanning electron microscope with an energy dispersive spectrometer. It was found that the HPDC under the vacuum could significantly change the morphology and distribution of the microstructure. For both conventional and vacuum-assist HPDC processes, the externally solidified crystals （ESCs） tended to aggregate in the center along the thickness direction of the castings. Besides, the aggregation was more pronounced, and the number of ESCs decreased, and the ESCs tended to become smaller and more globular, as the distance between the specimen location and runner increased. Compared with the conventional castings, the vacuum-assist HPDC can significantly reduce the size and amount of ESCs, and the ESCs tended to be more globular. For the distribution of ESCs along the thickness of the specimens, the aggregation tendency was more pronounced in vacuum-assist die castings than that in conventional castings. Besides, the distribution of ESCs at different locations was more converged in the vacuum-assist HPDC than that in the conventional HPDC.

铸造增压压力对汽车用AlSi9Mg铝合金组织和力学性能的影响

通过改变低压铸造过程中不同增压压力来研究其对AlSi9Mg合金显微组织与力学性能的影响。结果表明,在高增压压力制备的AlSi9Mg合金样品具有更加致密的显微组织及更接近球形的共晶Si颗粒。同时,由于具有更好的填充能力,高增压压力下合金的气孔缺陷大大减少,合金具有更优异的力学性能。在90、150、210 kPa3种不同级别的增压压力下,晶粒尺寸呈逐渐减小的趋势,对应的合金晶粒尺寸和二次枝晶臂间距分别为246、197、149μm,44.9、37.3、31.1μm;3种增压压力对应的密度和孔隙率分别为2.656、2.659、2.674 g/cm^(3),0.96%、0.79%、0.38%;AlSi9Mg合金的抗拉强度、屈服强度和伸长率分别为238.76、174.68 MPa和3.14%;252.43、177.47 MPa和4.61%;256.10、178.81 MPa和6.85%,分别提高了7.26%、2.36%、118.15%。

铝车轮铸造模具水冷界面换热系数反算求解

铝车轮低压铸造过程中,模具温度场是影响铝液凝固的重要因素。水冷作为铸造模具的主要冷却方式,对模具温度场的影响机理仍不明晰,有待深入研究。本文以铝车轮铸造模具的边模水冷模块为研究对象,设计水冷降温实验并采集水冷过程中的模具温度数据。通过ProCAST及ANSYS分析冷却水流动状态,以实测温度数据为基础进行软件反求解,基于Beck非线性估算法,建立界面换热数值模型。通过对比分析两种界面换热系数求解方式,并正向求解以验证两种求解方式的准确性,以期为铝车轮低压铸造模拟验证提供数据支撑,有望获取冷却水与模具的真实换热系数,并揭示其传热行为和换热机理。

基于正交试验的铝合金减速机壳体低压铸造工艺优化

利用数值模拟方法对铝合金蜗轮减速机壳体低压铸造过程进行分析,预测壳体中可能产生的缩松缩孔缺陷及位置分布,并分析其形成原因。在此基础上,通过改进冷却方案,并基于正交试验对工艺参数进行了多目标优化。得到的最优工艺参数为:浇注温度740℃、模具预热温度240℃、冷却水温度20℃。结果表明,优化后的壳体无缩松缩孔缺陷。通过生产试制和金相分析,验证了此优化工艺的可行性。

车身真空高压压铸技术研究

铝合金真空高压压铸技术在汽车行业逐步得到应用,研究分析了真空高压压铸材料、工艺、产品及现阶段重点问题。概括了热处理和免热处理材料的物理特点、化学成分及机械性能;介绍了真空高压压铸工艺流程和产线、工艺设计、工艺参数、成形性能;分析了产品性能、厚度、尺寸、连接、维修、模具寿命现阶段的主要问题;总结了真空高压压铸技术的优势并展望其发展前景。

乘用车车身大型压铸件设计与研究

为实现乘用车车身大型压铸件设计,从压铸工艺种类和特点出发,分析了高真空压铸在乘用车车身大型压铸件中的应用,并针对关键接头、重要梁系、主要加强件、减振器塔座、A柱模块、后地板总成、前舱总成等常见压铸件应用部位,从壁厚、加强筋和顶针布局方面分析了压铸件的设计原则和要求。

低压铸造铝合金后副车架结构设计与工艺开发

介绍了某车型低压铸造铝合金后副车架轻量化设计及工艺开发过程。首先依据客户输入的硬点坐标、环境数据及边界间隙设计产品外形,并对结构进行拓普优化轻量化设计,通过产品的疲劳、耐久性、强度、刚度及模态等仿真分析,使产品结构和性能满足设计要求;同时结合产品结构和低压铸造工艺要求,基于分型面和起模斜度的确定、增加内芯定位点和排砂口以及优化合金成分和热处理等措施,设计浇注系统和工艺方案,再对铸件充型和凝固过程模拟分析进一步优化方案,经试制铸件结构和性能均满足要求。

铝合金低压铸造过程数值模拟

铝合金密度小、比强度高,常作为汽车轻量化材料。低压铸造充型平稳,能成形复杂薄壁铸件,广泛应用于汽车典型零部件的制造。为优化低压铸造工艺、减少铸件缺陷、获得优良组织性能的铸件,运用集成计算材料工程与多尺度数值模拟方法对铝合金低压铸造过程开展研究,具有重要的科学意义与工程价值。本文全面综述了低压铸造铝合金凝固过程数值模拟技术的发展,分析了充型过程和凝固过程的宏观数值模拟及其常用算法,归纳总结了元胞自动机模拟铝合金初生相和共晶相的微观组织演变的研究现状,展望了铝合金低压铸造过程数值模拟的未来发展方向。

低压铸造升液管的安装、维护及检测

低压铸造是一种被广泛应用的铸造工艺,而升液管是其中重要的一个工艺装备。本文主要介绍了陶瓷升液管的连接方式和正确的安装方法,金属法兰升液管的具体安装方法和要求以及升液管的日常维护重点和漏气检测方法。

A356铝合金轮毂低压铸造数值模拟以及组织与力学性能

采用轻质铝合金构件是实现汽车轻量化的重要策略,轮毂作为典型车用铝合金零件,其成形质量与低压铸造工艺参数密切相关。本文采用ProCAST有限元软件对A356铝合金轮毂低压铸造过程进行模拟仿真,研究了浇注温度及保压时间对轮毂成形质量的影响。并利用优化参数对轮毂进行铸造,对其成形质量及组织性能进行分析;同时,对轮毂不同部位进行微观组织及力学性能分析;对轮辋部位进行拉伸性能测试。结果表明:在浇注温度为700℃、保压时间为80 s时,铝液充型平稳,凝固符合顺序凝固原则,其铸造缺陷产生的概率最低;轮毂由内至外晶粒尺寸逐渐减小,由轮毂中心部位的58μm减小至外轮缘的23μm;轮辋部位抗拉强度可达228 MPa,屈服强度为170 MPa,断后伸长率为6%。

低压铸造铝合金轮毂模具热变形的数值模拟

目的针对模具高温变形影响低压铸造铝合金轮毂尺寸精度的问题,通过数值模拟和实验相结合的方式,揭示低压铸造过程中模具的变形规律。方法建立了低压铸造过程中描述模具热力学行为的数学模型以及铸造多循环计算方法,进行了轮毂低压铸造实时蓝光扫描验证,通过模拟与实验结果的对比验证,研究了轮毂低压铸造过程中的模具温度、应力及变形规律。结果模拟与实测温度对比结果表明,两者变化趋势基本一致,侧模和下模在开模时刻的最高温度分别为486℃和512℃。侧模的模拟与实测温度峰值的相对误差为2%,下模模拟与实测温度最大相差23℃。变形模拟与实时扫描结果均表明,侧模热变形呈曲率减小趋势,按变形大小划分,侧模型腔表面存在小变形(-0.04-0.16mm)、过渡(0.16-0.48mm)和大变形(0.48-0.89mm)3个变形区域,侧模变形的模拟精度约80%;下模平面沿轮毂轴向下沉0.4mm,变形模拟精度约75%。结论所建立的热变形模拟方法可以较好地计算铝合金铸造模具热变形,阐明铝轮毂低压铸造模具变形规律,为后续模具反变形设计、提高轮毂尺寸精度提供研究基础。

基于田口法的铝合金空心控制臂低压铸造工艺优化

为优化低压铸造A356铝合金空心控制臂的工艺参数,通过田口法,以凝固时间、缩松、缩孔体积值和二次枝晶臂间距为评价指标,利用均值与极差分析和方差分析的方法,分析了温度参数与时间参数对铸件成形质量及力学性能的影响。结果表明:模具预热温度及充型时间对铸件力学性能、生产效率均有显著影响。

厚壁ZL205A铝合金铸件铸造工艺研究

基于FEM(Finite Element Methods)开发的理论模拟对研究铝合金材料铸造成形有重要意义。采用理论模拟研究ZL205A铝合金筒体铸件低压铸造、重力铸造工艺,根据对应工艺获得铸件的实际质量,确定适合产品的理想工艺。研究结果表明,采用浇注系统截面比1:4:5开放式重力浇注工艺,产品外观荧光检查、内部X光探伤检查均满足产品技术需求,且工艺出品率达到55%以上。

低压铸造铝合金车轮模具水冷结构设计

低压铸造模具冷却结构由风/水雾冷改为水冷,研究了冷却对模具铸造的影响。结果表明,水冷结构不同,作用位置不同,冷却效果不同。根据模具结构特点,合理布置水冷结构、分布,有效提高了铸造效率和铸件产品力学性能。

基于MAGMA的铝合金发动机缸体低压铸造工艺优化

以铝合金发动机缸体的低压铸造过程为研究对象,应用MAGMA铸造模拟软件对充型及凝固过程进行模拟,将固相分数、充型温度、虚拟实验设计以及非热平衡状态的模拟结果和实际生产情况相结合,制定工艺参数,预测缺陷产生的位置,确定最佳工艺参数组合,优化生产工艺,保证质量稳定。