product news/產品新聞
BMW’s Inorganic Core Drying Simulated With Flow-3D 采用FLOW-3D模拟宝马的无机砂芯的干燥过程
Te BMW metalcasting facility in Landshut, Germany, uses an inorganic, environmentall7 friendly coremaking process that is healthier for the workers on the shop floor because it uses water-based binders. Te inorganic process also offers potential improved
casting quality due to reduced core gas production and lower tool temperatures. In the process, the mold is heated while the sand is shot into the mold and as it’s drying. As a consequence, the core dries and hardens first in a thin layer adjacent to the wall. After the shooting process, the core is vented with hot pressurized air. Te water in the core is vaporized by the hot air, and the air- vapor mixture leaves the core through the bottom venting nozzles. Removal of the water results in the hardening of the core by a chemical reaction of the binder. Flow Science Inc., Santa Fe, N.M., USA, developed
a simulation of the inorganic core drying process to help predict and correct some core defects that were occurring in production. Te new core drying model considers porous sand cores
of arbitrary shapes with variable properties, such as moisture content, temperature and vapor concentration. By simulating transient conditions throughout a core, engineers can make detailed investigations of non-uniform initial conditions, as well as a variety of drying techniques. Flow Science first conducted a set of experiments on a
simple, generic core to validate its core drying simulation model before testing it on a core for a production part. Te core, which had not yet been finalized, was exhibit- ing two minor imperfections as a consequence of excess residual moisture. Te geometry of the core and the nozzles by which the
core is vented were set up in a CAD system and imported into the Flow-3D simulation program in .STL format. Te
宝马在德国Landshut的铸造厂应用了一种环保的无 机砂制芯，因为使用的是水基粘结剂，有利于工人的 健康。
由于砂芯发气量小、模具温度低，因此，无机砂具 有改善铸件质量的潜力。在这个工艺中，射砂的同时 完成砂子的加热。因此，砂芯首先在靠近型壁的地方 干燥硬化。射砂后，用高压热空气对砂芯吹风，砂芯 中的水分被蒸干，水气混合物从底部的通风口排出。 去除水分，粘结剂发生化学反应，使砂芯硬化。 美国圣达菲的Flow Science公司开发了一项无机砂 芯干燥过程的模拟技术，以预测和克服生产中砂芯出 现的缺陷。
新的砂砂干燥计算模型考虑了各种形状和性能的砂 芯，比如不同的水份含量、温度和蒸汽浓度。通过对 砂芯过度状态的模拟，工程师可以详细了解非均匀的 初始条件以及各种干燥技术
在实际砂芯测试之前，Flow Science首先在一个普 通简单砂芯上做了一系列试验，以验证砂芯干燥的计 算模型。由于残余水分过高，尚未完全固化的砂芯表 现出两种轻微瑕疵。
在CAD系统中进行砂芯及排气孔的几何造型，转成 STL格式，将其导入Flow-3D模拟程序。模拟出的有残 余水份的区域与实际生产中的缺陷位置一致。
A core for an upcoming production part was exhib- iting imperfections due to residual moisture.
一个将要生产零件的砂 芯由于残余水份造成的 瑕疵。
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FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION Spring 2012
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