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Fig. 2. Minor shrinkage was predicted in the three areas under the risers.


图2:预测到冒口下方三 个部位有小缩孔。


Overcoming Obstacles in Simulation When working with the 200 series of aluminum alloys,


chemistry control is more important than with 300 series aluminums. Iron and silicon levels need to be minimized to achieve the expected properties. Impurities from insuf- ficiently cleaned crucibles or improperly mixed alloys can lead to unsuitable results. Metalcasters must ensure tools and ladles are clean. Process controls to minimize changes in chemistry also are essential. In 200-series alloys, mechanical properties depend on


controlling the iron and silicon levels in the alloy. In A206, iron levels need to be controlled to less than 0.1% and silicon levels to less than 0.05%. Castings made with specified chemistries and solidification rates typical of the permanent mold process can develop yield strengths of 50 ksi coupled with double digit elongation. To research the ability to cast A206 in permanent mold,


a case study on a mounting bracket casting used in medical equipment was conducted. Te component, shown in Fig. 1, is currently produced in A356 in a 4140 steel permanent mold. Te current design ensures the A356 alloy can be cast without hot tearing. Te A356 component also needed to pass grade C radiographic quality. Te team’s key objectives were to establish and refine cast-


ing processing parameters, including: • Initial mold preheating temperature. • Pouring temperature. • Mold fill time.


300系列铝硅合金更严格。铁和硅的含量须降到最低, 才能达到预期的产品性能。因坩埚中清洁不彻底或合金 混配不当而产生的杂质可以产生不良后果。因此,铸造 厂必须保证模具和浇包清洁。为了将化学成分的变化降 到最小程度,过程控制也是重要的。


200系列铝铜合金的力学性能取决于控制合金中铁 和硅的含量。A206合金中,铁的含量须控制在0.1%以 内,硅的含量应控制在0.05%以内。采用金属型工艺, 化学成分符合要求,以适于金属型铸造工艺制成的铸 件,屈服强度可达50 ksi(345MPa),且伸长率可达 两位数。


为了探讨金属型工艺铸造A206合金的特性,我们 以医疗设备的支架铸件为例进行了分析研究。图1所 示的铸件,材质为A356合金,目前用4140钢制金属 型制造。现在的设计可保证A356合金铸件不出现热 裂。A356合金铸件也需要通过C级射线探伤检测。 该研究项目组的主要目标是确立并完善铸造工艺参 数,包括: • 铸型初始预热温度; • 浇注温度; • 充型时间;


Fig. 3. The simulation showed po- tential hot tearing in the top cross bar and journal areas.


图3:模拟试验显示出上横臂和 轴颈部位可能出现热裂。


42 | FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION March 2015


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