Controlled cooling of an aluminum alloy casting based on 3D printed rib reinforced shell mold

3D printing technology has been used for sand molding and core printing, but they simply substitute the traditional molding and core making method without changing the shape or size of the sand mold(core) and their dense structure. In this study, a new type of hollow mold based on 3D printing is presented. The new type of mold is a rib reinforced thickness-varying shell mold. This mold design can realize the controlled cooling of castings, i.e., different cooling rates at different areas, and improve the temperature uniformity of a casting after its solidifi cation. Therefore, the performance of castings can be improved and their residual stress and deformation can be reduced. This kind of new mold was applied to a stress frame of A356 aluminum alloy. The 3D printed rib reinforced thickness-varying shell mold was compared with the traditional dense mold, and the castings obtained by these two kinds of molds were also compared. The experimental results showed that the rib reinforced shell mold increased the cooling rate of the casting by 30%, tensile strength by 17%, yield strength by 11%, elongation by 67%, and decreased its deformation by 43%, while sand consumption was greatly reduced by 90%.     

两种不同约束条件下发动机缸体铸件热应力场的数值模拟

采用FDM/FEM集成热应力分析系统(其中采用铸造之星FT-STAR进行温度场计算,ANSYS进行热应力场计算,采用FT-STRESS进行有限差分网格向有限元网格转换和有限差分/有限元温度载荷转换),对某厂柴油机发动机缸体铸件进行从浇注到冷却至室温全过程的温度场、热应力场数值模拟,得到冷却变形情况及残余应力分布,并研究比较了将气缸处砂芯考虑为部分刚性,和将砂芯考虑为完全退让性的两种不同约束模拟方案对计算结果的影响。前者应力值和变形值远远大于后者的结果。     

铸态曲轴壳型背丸工艺

根据铸件的技术要求,采用壳型背丸工艺生产铸态曲轴。分析了曲轴壳型背丸的铸造过程,设计了铸件浇冒口系统,从铁水熔炼工艺、化学成分和球化孕育工艺对铸件内在质量进行控制。生产实践表明,采用壳型背丸工艺生产的铸态曲轴表面光洁、尺寸精度高、内部组织致密。     

基于 Magma 差速器壳体铸造工艺解析与应用

针对一种轿车差速器壳体零件,应用 Magma 软件对其砂型铸造方式下的垂直造型浇注工艺和水平造型浇注工艺分别进行了设计模拟运算,并对两种方案的优劣进行对比解析,从而确定在现有条件下的最优铸造工艺,并投入模具开发和生产应用,生产出内部质量合格的铸件。     

Inference of optimal speed for sound centrifugal casting of Al-12Si alloys

True centrifugal casting is a standard casting technique for the manufacture of hollow, intricate and sound castings without the use of cores. The molten metal or alloy poured into the rotating mold forms a hollow casting as the centrifugal forces lift the liquid along the mold inner surface. When a mold is rotated at low and very high speeds defects are found in the final castings. Obtaining the critical speed for sound castings should not be a matter of guess or based on experience. The defects in the casting are mainly due to the behavior of the molten metal during the teeming and solidification process. Motion of molten metal at various speeds and its effect during casting are addressed in this paper. Eutectic Al-12Si alloy is taken as an experiment fluid and its performance during various rotational speeds is discussed.     

Cooling control for castings by adopting skeletal sand mold design

The cooling control of the melt during the casting process is of great significance. A comprehensive closed-loop cooling control of castings by adopting a skeletal sand mold design was proposed. The skeletal sand mold consisting of an adaptive shell, functional cavities and a support was designed and created based on the finite difference meshes of a casting. It was applied to a round wall test casting. Two kinds of skeletal sand molds, one with lattice support and the other with enforcing ribs for this casting were designed and printed out by the 3 D printing(3 DP) method. Aluminum alloy A356 was cast by using these two sand molds. The first mold was cooled by natural convection, the other one by water spray cooling. Two sound castings were obtained. The sand mold temperature, cooling curves, microstructures, mechanical properties, residual stress and deformation were measured, compared and discussed. Water spray cooling hastened the cooling rate by 62%, increased the content of Mg and Cu in the α-Al matrix, improved the mechanical properties, and altered the surface residual stress state.     

消除碳素钢精密铸件表面渣、气孔的措施

精密铸造生产中,碳素钢精密铸件因含碳量高,浇注过程中吸气、氧化严重,铸件表面容易出现渣、气孔,主要集中在组树方案中铸件的上表面,影响铸件的外观及质量.在常规方法不能完全解决的情况下,引入砂模铸造工艺设计方法,通过外加直浇道,钢水从外加直浇道中注入型壳,使钢水在型壳内平稳上升,产生的气及渣随同钢水通过内浇道顺利浮出铸件,避免组树方案中铸件上表面产生渣气孔,改善铸件表面质量,减少铸件后期的修补成本.     

Application of 3-D numerical simulation software SRIFCAST to produce ductile iron castings

1. IntroductionSince the 1960's, there have been 3 progressive periodsfor modeling and simulation of the technological processof castings. In 1988, 3-D temperature fields were calculatedsuccessfully during the solidification process of steelcastings in many countries [1-4]. In 1995, 3-D velocityfields calculations of metal flow in mold filling were alsoachieved by advanced researchers [5-8]. From 1990 untilnow, the new task has been to model and simulate themicrostructure and morphology of cr…     

镁合金副车架压铸过程计算机仿真与工艺优化

基于AnyCasting软件,采用正交试验研究了压铸过程中冲头速率、模具温度、浇注温度对镁合金副车架铸件气孔含量、氧化倾向、冷隔和缩松等缺陷的影响,并得到了优化的压铸工艺参数:冲头速率为7m/s、模具温度为250℃、浇注温度为700℃。在该工艺参数条件下,获得了表面和内部品质良好的镁合金副车架压铸件,同时验证了通过模拟仿真优化压铸工艺参数方法的有效性。     

DZ0309轮毂铸件的工艺改进

DZ0309轮毂铸件原采用Z1410AS造型机生产,每型2件,内孔由手工制作的油砂芯形成。生产结果显示:(1)内孔尺寸精度差,单件铸件型砂用量大;(2)每型件数过少,型板面积利用率低;(3)铸件工艺出品率较低;(4)铸件顶面夹渣、石墨漂浮缺陷严重。对缺陷原因进行了分析后,采用了如下改进措施:(1)对原工艺进行了改进;(2)采用静压造型线生产铸件;(3)取消砂芯,铸件内孔改为由吊砂形成;(4)采用陶瓷网挡渣。结果铸件表面质量明显改善,经济效益也相应得到提高。     

14英寸显像管玻壳锥凸模铸造工艺的优化设计

计算机模拟技术为铸造工艺的设计提供了一种能大幅度地节约时间和降低费用生产铸件的途径,也为预测铸造缺陷提供了手段。详细介绍了通过铸造ＣＡＤ技术预测玻壳模具铸造缺陷进而优化工艺方案的方法,提出了运用Ｇ／ＶＣ判据与临界固相率法相结合的方法对缩孔及缩松进行预测。确定了相应的判据临界值。     

铸态高强度球铁曲轴铸造工艺及材料的研究

介绍了曲轴的壳型铸造工艺：垂直分型,每型2件曲轴,每箱装5个壳型,立置底注,横浇道放置过滤网,壳型外侧充填铁丸,并进行15~20 s的震实。通过曲轴冒口、浇口杯、过滤网、型壳涂胶工艺的优化选择,以及曲轴冷却条件的改善,炉料的调整,球化和孕育处理工艺的优化,Cu、Sn、Mn、Bi合金元素的添加,得到了高强度铸态球墨铸铁曲轴。几年来,生产高强度球墨铸铁曲轴近10万件。     

重力铸造铝合金压壳的顶浇工艺实践

压壳的金属型顶浇工艺最主要的是解决落差冲击造成的乱流卷渣问题,以及指向性凝固问题。本文从浇铸落差与浇口大小对压壳渣孔的影响进行了计算分析,借助模流分析软件Anycasting对下模底部不同高度冷却柱的铝液充型进行了模拟,并且将模拟与计算分析结果与生产实践验证。结果表明,解决与改善了常见的渣孔问题。     

铸件充型凝固过程数值模拟发展现状

铸件内在质量很大程度上取决于铸件的充型和凝固过程。将计算流体力学、计算传热传质学和计算机可视化技术应用于铸造工艺设计 ,可以使铸造技术人员更清楚地了解铸件形成过程 ,快捷地确定较为合理的铸造工艺参数。本文对铸件充型和凝固过程的数学模型、计算方法及商品化软件方面的发展现状进行了综合评述 ,并展望了该领域的发展前景。     

高碳钢连铸保护渣的性能

为了研究高碳钢保护渣在连铸过程中的匹配性,对典型工业高碳钢保护渣的熔化、润湿、黏度、渣膜分布,以及传热性能进行研究。结果表明,4个高碳钢保护渣的开始熔化温度范围为1 110~1 129 ℃,润湿角范围为30.1°~37.8°,黏度范围为0.210~0.312 Pa·s,转折温度范围为1 046~1 130 ℃,渣膜的液态层比例为14.7%~18.9%。其中,1号高碳钢保护渣熔化温度较低(熔化区间1 110～1 345 ℃)、黏度较低(0.264 Pa·s)、渣膜液态层较高(比例为18.9%)、转折温度(1 059 ℃)和控热能力均适宜,表明该渣在高碳钢连铸结晶器中可以迅速熔化,形成足够的液态渣,并从弯月面渗入渣道,形成均匀的渣膜,从而润滑铸坯,避免黏结漏钢和裂纹等缺陷,保障高碳钢连铸的顺行。     

铝合金真空低压消失模壳型铸造工艺参数研究

研究了铝合金真空低压消失模壳型铸造工艺参数与铸件充型能力、内部质量的关系。结果表明,铸件的充型能力与浇注温度、充气流量、真空度、充气压力成正比;相比真空度和充气压力,充气流量与浇注温度对铸件充型能力的影响更为显著。工艺参数对薄壁铸件充型能力的影响要大于厚壁铸件;铸件孔隙率随浇注温度的提高先降低后升高,随着充气流量、充气压力、真空度的增大而降低,而密度则随各工艺参数的增大而增大。真空低压消失模壳型优化的工艺参数:浇注温度为720~750℃,充气流量为12~19m3/h,真空度为-0.03~-0.04MPa,充气压力为0.03~0.04MPa。     

A numerical analysis of fluid flow, heat transfer and solidification in the bending-type square billet continuous casting process

A numerical modeling system was developed which can simulate the transport phenomena of a bending type square billet continuous casting process. Fluid flow and heat transfer were analyzed with a 3-dimensional finite volume method (FVM) with the aid of an effective heat capacity algorithm for the solidification. For a complex geometry of the bending type billet caster, a body-fitted-coordinate (BFC) system was employed. The bent structure of the caster allows a recirculating flow to develop in the upper and outer-radius region and the main stream to shift toward inner radius. This causes the thinner solid shell in the inner radius region than in the outer one. Besides standard operation conditions, we have analyzed the results when casting speed, caster shape, and tundish superheat changes. Lower casting speed makes the solid shell thicker by reducing heat flux from the mold. In the vertical caster, solid shell thickness are more uniform than that in the bending-type in entire region. When superheat increases by 5°C, solid shell thickness at the mold exit becomes thinner by 1 mm.     

我国精铸原辅材料的现状和发展

论述了精铸原辅材料的发展现状和存在的不足,以及解决的措施。模料焙烧后形成的碳渣会导致铸件夹杂和反应性气孔出现,通过多层过滤和离心分离能消除这些缺陷。介绍了不同型壳材料的性能,及其存在问题和国内外的改进方法。对粘结剂和合金材料的应用,进行了简述,并对未来的发展作了说明。     

单轴线挤压铸造凝固组织形态和塑性变形缺陷分析

分析了单轴线挤压铸造凝固体内部正向和径向压力存在的差异。结果表明,正向压力沿轴线分布同样不均匀,压力差异使得界面传热系数、结晶前沿熔体温度梯度、晶体生长速度以及塑性变形出现差异,产生单轴线挤压铸造件凝固组织形态不一致、致密度不均匀等缺陷。提出了一种满足组织性能均匀、高致密等要求的高性能铸件的多向挤压铸造工艺方法。     

连铸板坯表面纵裂纹的形成原因及控制

连铸坯表面纵裂形成于结晶器内,由于凝固前沿树枝晶间富集液相导致的枝晶间脆性及结晶器中γ晶粒粗大导致的晶界脆性。在结晶器5种复杂应力的作用下,在结晶器内初生坯壳的薄弱处形成纵裂纹。坯壳出结晶器后,二冷段上部过强的冷却或对弧不良等各种应力都会促进纵裂纹的进一步扩展和延伸。为了防止纵裂纹萌生,首先要控制好结晶器保护渣及结晶器冷却工艺使结晶器传热均匀,防止坯壳凹陷变形;其次尽量降低钢中S、P等杂质元素含量,C含量避开包晶区。