Physical Simulation of Mold-Filling Processing of Thin-Walled Castings under Traveling Magnetic Field

Mold-filling process of thin-walled castings under the condition of traveling magnetic field has been studied by physical simulation method using gallium melt and fast speed photography. Flow morphology and its formation mechanism were obtained and discussed for thin-walled casting. The influences of magnetic field density on the filling ability, filling velocity and mold filling time have been studied. The differences in filling capability between gravity casting and casting under the traveling magnetic field have been compared. The results indicate that the mold filling ability of the gallium melt increases greatly under the condition of traveling magnetic field; the filling time is shortened from 18 s under gravity field to 3 s under the traveling magnetic field and average flow rate of the melt increases from 1.6 to 8.68 cm3/s; the change law of the cross-section morphology of the gallium melt during the mold filling is that at first, the cross-section area does not change, then it decreases gradually. When the front of the melt reaches the end of the mold cavity, the front melt will backfill the mold; the wider the width of mold cavity, the better the mold filling ability. The mold filling ability of gallium melt in mold with upper magnetic conductor is better than that without upper magnetic conductor.

Eliminating shrinkage defects and improving mechanical performance of large thin-walled ZL205A alloy castings by coupling travelling magnetic fields with sequential solidification

ZL205 A alloys with large thin-walled shape were continuously processed by coupling travelling magnetic fields(TMF)with sequential solidification,to eliminate the shrinkage defects and optimize the mechanical performance.Through experiments and simulations,the parameter optimization of TMF and the influence on feeding behavior,microstructure and properties were systematically studied.The results indicate that the magnetic force maximizes at the excitation current of 20 A and frequency of 200 Hz under the experimental conditions of this study,and increases from center to side-walls,which is more convenient to process thin-walled castings.TMF can break secondary dendritic arm and dendrites overlaps,widen feeding channels,prolong the feeding time,optimize the feeding paths,eliminate shrinkage defects and improve properties.Specifically,for as-cast state,TMF with excitation current of 20 A increases ultimate tensile strength,elongation and micro-hardness from 186 MPa,7.3%and 82.1 kg/mm^(2) to 221 MPa,11.7%and 100.5 kg/mm^(2),decreases porosity from 1.71%to 0.22%,and alters brittle fracture to ductile fracture.

Numerical simulation for mold-filling of thin-walled aluminum alloy castings in traveling magnetic field

The numerical simulation for mold-filling of thin-walled aluminum alloy castings in horizontal traveling magnetic field is performed. A force model of Al alloy melt in the traveling magnetic field is founded by analyzing traveling magnetic field carefully. Numerical model of Al alloy mold-filling is founded based on N-S equation, which was suitable for traveling magnetic field. By using acryl glass mold with indium as alloy melt, the experiment testified the filling state of alloy in traveling magnetic field. The results of numerical simulation indicate that the mold-filling ability of gallium melt increases continually with the increase of the input ampere turns.

Solidified structure of thin-walled titanium parts by vertical centrifugal casting

The solidified structure of the thin-walled and complicated Ti-6AI-4V castings produced by the vertical centrifugal casting process was studied in the present work. The results show that the wall thickness of the section is featured with homogeneously distributed fine equiaxial grains, compared with the microstructure of the thick-walled section. The grain size of the castings has a tendency to decrease gradually with the increasing of the centrifugal radius. The inter-lamellar space in thick-walled casting parts is bigger than that of the thin-walled parts, and the profile of inter-lamellar space is not susceptible to the centrifugal radius.

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.

Filling mode and regularity of vertical centrifugal casting process of titanium alloy in thin-walled cylinder cavity

The mold filling process of titanium alloy in a thin-walled cylinder cavity under vertical centrifugal casting process was studied by means of the hydraulic simulation experiments. Results show that the filling mode of the melt in the cylinder cavity varies with casting wall-thickness. When the casting wall-thickness is less than or equal to the thickness of the first layer during the filling process, the melts fill the cavity from the bottom to the top.When the casting wall-thickness is greater than the thickness of the first layer during the filling process, the melts first fill the largest radius parts of the cavity with a certain thickness of the first layer from the bottom to the top of the cavity, and then they fill the cavity from the larger radius part to the smaller radius part. The melt filling ability increases with the increment of the mold rotational speed and the pouring temperature. In another aspect, the melt filling ability rises with the decrement of the melt viscosity, and the melt with the better filling ability is prone to fill the cylinder cavity layer by layer.

A STUDY ON THE EFFECT OF RADIAL INERTIA ON THE ELASTO-PLASTIC COMBINED STRESS WAVE PROPAGATION IN THIN-WALLED TUBES

An in-depth analysis of propagation characteristics ofelasto-plastic combined stress waves in circular thin-walled tubeshas been made. In obtaining the simple-wave solution, however, mostresearches have ignored the influence of the circumferential stressrelated to the radial inertial ef- fect in the tubes. In this paperthe incremental elasto-plastic constitutive relations which areconve- nient for dynamic numerical analysis are adopted, and thefinite-difference method is used to study the evolution adpropagation of elasto-plastic combined stress waves in a thin-walledtube with the radial inertial effect of the tube considered. Thecalculation results are compared with those obtained when the radialinertial effect is not considered. The calculation results show thatthe radial inertial effect of a tube has a fairly great influence onthe propagation of elasto-plastic combined stress waves.

Microstructure and mechanical properties of BFe10 cupronickel alloy tubes fabricated by a horizontal continuous casting with heating-cooling combined mold technology

A new horizontal continuous casting method with heating-cooling combined mold （HCCM） technology was explored for fabri- cating high-quality thin-wall cupronickel alloy tubes used for heat exchange pipes. The microstructure and mechanical properties of BFe 10 cupronickel alloy tubes fabricated by HCCM and traditional continuous casting （cooling mold casting） were comparatively investigated. The results show that the tube fabricated by HCCM has smooth internal and external surfaces without any defects, and its internal and external surface roughnesses are 0.64 μm and 0.85 μm, respectively. The tube could be used for subsequent cold processing without other treatments such as surface planning, milling and acid-washing. This indicates that HCCM can effectively reduce the process flow and improve the pro- duction efficiency of a BFel0 cupronickel alloy tube. The tube has columnar grains along its axial direction with a major casting texture of {012}〈 621 〉. Compared with cooling mold casting （6 = 36.5%）, HCCM can improve elongation （3 = 46.3%） by 10% with a slight loss of strength, which indicates that HCCM remarkably improves the cold extension performance of a BFe 10 cupronickel alloy tube.

Effect of depressurizing speed on mold filling behavior and entrainment of oxide film in vacuum suction casting of A356 alloy

The effect of depressurizing speed on mold filling behavior and entrainment of oxide film of A356 alloy was studied. Themold filling behavior and velocity fields were recorded by water simulation with particle image velocimetry. The results show thatthe gate velocity first increased dramatically, then changed with the depressurizing speed: the gate velocity increased slowly atrelatively high depressurizing speed; at reasonable depressurizing speed, the gate velocity kept unchanged; while at lowerdepressurizing speed, the gate velocity decreased firstly and then kept unchanged. High gate velocity results in melt falling backunder gravity at higher speed. The falling velocity is the main factor of oxide film entrainment in vacuum suction casting. The designcriterion of depressurizing rate was deduced, and the A356 alloy castings were poured to test the formula. The four-point bend testand Weibull probability plots were applied to assessing the fracture mechanisms of the as-cast A356 alloy. The results illuminate amethod on designing suitable depressurizing speed for mold filling in vacuum suction casting.

锌铝合金铸锭设备自动化进程研究

锌铝合金铸锭设备,是将锌和铝熔合成合金并铸造成锭的关键设备。该设备核心环节在于将阴极锌片和铝元素在熔炼装置中进行加热熔融,形成合金液体,随后将其浇铸到模具中,待冷却后形成高品质的成品锭。整个生产过程涉及加料、熔炼、合金化、浇铸、冷却、脱模、称重、标识等多个环节。鉴于锌锭市场价格疲软,而锌铝合金的高附加值及需求量的日益增长,未来锌铝合金锭有望取代锌锭,成为锌冶炼企业的主打产品。本文深入探讨了锌铝合金锭的应用场景、生产工艺流程以及国内铸锭设备的现状。同时,对国内外锌铝合金铸锭自动化设备的发展动态和自动化进程进行了系统梳理,并重点介绍了直线式和圆盘式两种高自动化程度的铸锭设备,展现了锌铝合金铸锭设备的广阔前景。

《再生铸造铝合金原料》新旧标准差异分析

本文在分析再生铸造铝合金行业政策、行业发展概况和标准实施效果的基础上,从分类差异和技术差异两个角度对GB/T 38472新旧标准进行对比。基于新版标准的主要技术变化,提出加强新标准宣贯力度、开展标准化试点示范、推动再利用工艺升级、营造社会再利用氛围等对策建议,助力新版标准全面实施。

北京奥运会自行车馆双层球面网壳结构的设计与施工方法

北京奥运会老山自行车馆屋盖采用带环梁的双层球面网壳结构,网壳支承于倾斜的人字型钢柱之上,覆盖直径达149.536m,建成后将成为我国跨度最大的双层球面网壳结构之一。该结构跨度大,矢跨比小,网格杆件较多,设计、施工存在着较大的难度。因此采取何种结构体系,如何进行合理的计算模型分析与施工都需要进行深入的分析与有效的论证。本文对该结构的设计与施工进行了较为全面的介绍与分析。

双金属复合管固-液铸轧复合轧制力模型研究

以传统双辊铸轧技术为基础,提出一种双金属复合管固-液铸轧复合近终成形工艺,利用专门的环形布流器,将液态覆层组元金属均匀地注入铸轧辊圆孔型与芯管基材所构成的环形结晶器内,利用快速凝固与轧制复合技术,将覆层金属均匀包覆于芯管基材表面。为揭示铸轧区内铸轧辊-覆层金属-芯管基材间的相互作用力学行为,利用Fluent软件对环形结晶器内覆层金属凝固过程进行热-流耦合分析,确定固相轧制复合变形计算区域。假设芯管基材为刚性体,可将固相轧制复合变形阶段视为纯减壁的带芯棒轧管过程,并依此推导固-液铸轧复合过程的轧制力工程计算公式,给出各参数的取值方法。在实验室条件下成功制备了外径38 mm、基层与覆层厚度均为4 mm的不锈钢/铝复合管,轧制力实测值与模型计算结果基本吻合,验证了工程计算公式的可靠性。研究成果对复合管固-液铸轧复合装备及工艺设计提供了理论依据。

大型圆柱形铸件浇冒口切除与打磨一体化设备总体设计

针对当前大型圆柱形铝铸件浇冒口的清除主要采用手工清除、清除效率低、对工人身体危害大的情况,研发一种大型圆柱形铝铸件浇冒口自动切割和打磨机床。介绍机床的工艺方案和总体布局,对切割装置、打磨装置、废料夹持装置的机械结构进行介绍,重点阐述切割装置的设计。采用环形切割和打磨的方案,大大提高浇冒口的清除效率;更换定位元件,可以适用不同型号的圆柱形铸件,设备的适用性高,对其他类似产品的设计有一定的参考价值。

滑块-齿轴块-齿环压铸模圆弧抽芯机构的设计

铸件带有圆弧形孔时,其孔的抽芯和成形是压铸模具设计与制造的难点之一。圆弧形孔型芯的抽芯轨迹为曲线,抽芯过程中孔容易变形,引起孔的形状和尺寸不能满足要求,且抽芯机构容易出现故障。文中设计出新颖的滑块-齿轴块-齿环抽芯机构,借助开模力提供抽芯动力。实际生产应用表明,设计的抽芯机构可以保证圆弧形孔成形质量的同时,模具结构简单、制造成本低、传动效率高、抽芯平稳可靠。

罗茨真空泵圆弧型转子型线设计及加工

罗茨泵转子型线的研究是罗茨泵设计的核心部分,圆弧型转子型线为广泛应用的罗茨泵转子型线之一。圆弧转子型线的设计中,首先实现转子理论型线的设计,然后基于理论型线,设计转子的实际型线和铸造毛坯型线。本文在实际型线和铸件毛坯型线的设计过程中,提出基于共轭特性的圆弧线实际型线和铸件毛坯型线设计方法,大幅简化了分析设计过程,并以此为基础,设计了70L/s罗茨泵圆弧转子型线及其粗加工和精加工方法。

圆环零件液态模锻研究

通过圆环零件的液态模锻成形实验,对在不同比压和浇铸温度条件下,锻件的微观组织形貌和力学性能进行了分析研究。结果发现,在不同比压下,随着比压值的增加,α枝晶长度随之减小,枝晶被破碎,锻件力学性能也随之升高;在不同浇铸温度条件下,锻件微观组织也有着较大的差异,且随着浇铸温度的升高,粗大树枝晶被打断、破碎细化现象较为明显,锻件组织致密,力学性能逐渐上升。

大型圆板类铸件试验模态分析

利用试验模态技术对锡林墙板进行模态分析,通过建立合理的网格模型,采用脉冲激励的方式获得传递函数,进而得到其低阶模态各种典型振型,为大型圆板类铸件振动时效工艺参数的制订提供了参考。

基于中国美国欧盟标准的圆形灌注桩配筋计算系统开发研究

运用微分原理并基于Mathcad分析平台,对中国标准、欧盟标准和美国标准钢筋混凝土圆柱结构的极限承载力分别进行程序编写,得到圆形截面的承载力曲线进行灌注桩设计,形成一套圆形灌注桩设计计算系统,达到计算标准化的目的。该计算系统采用图形一体化,输入和输出直观、易懂,并且采用微分手段可得出结构的承载能力曲线及灌注桩配筋标准化文件,更适合设计人员根据需要进行选择使用。

深圳大运会篮球馆结构设计

对深圳市坪山体育馆的结构选型,受力特点及结构设计进行介绍。针对上述问题进行计算分析,包括:弦支穹顶体系整体受力性能和屈曲稳定性影响分析;荷载取值分析;施工全过程模拟计算分析;单体上部钢结构、单体下部混凝土结构初步分析基础上的整体结构总装分析;根据深圳本地气温统计资料,合理选取计算温差,分析温差效应对结构安全的影响;关键复杂节点实体有限元计算分析,确保其可靠安全。计算分析表明:1)弦支体系不仅有效地提高了屋盖结构刚度,还大大提高了单层网壳结构稳定性;2)大跨空间结构设计进行总装分析至关重要;3)大跨结构温差收缩效应影响存在,温差效应施工模拟计算十分必要;4)复杂空间结构的节点十分关键,应通过有限元分析,精心设计。