Fig. 7. Two bolts are formed into a large green sand mold as ram-up inserts to force faster solidification into the area.


图7、两个螺栓形成一个大型 湿砂摸样。预埋式插入，加速 这个区域的凝固。


earth metal added. Special alloys have been developed that use pure lanthanum rather than the mixture of rare earth elements. An optimized amount of lanthanum results in a high nodule count with a different nodule size distribution. The number of large, early forming nodules decreases slightly, and the number of medium and smaller nodules increases, which is an indication that graphite precipitation has been steadier through freezing, with more expansion effect during the latter stages of freezing. In a comparison of MgFeSi alloys using the tradi-


tional mischmetal and MgFeSi alloy using lanthanum, the ductile iron using lanthanum provided a struc- ture with fewer large nodules and a high population of medium and small nodules. Figure 4 shows gross shrinkage in the iron treated with mischmetal and none in the iron treated with lanthanum. Conserving the expansion effect by saving some carbon precipitation to the latter stages of freezing has a profound effect on shrinkage. A minimized tendency of iron to shrink can be somewhat correlated with a wide nodule size distribution, highly skewed to the finer sizes. This also can be achieved using a proprietary inoculant contain- ing sulfur and oxygen compounds.


土合金。已经开发了使用纯镧而不是用混合稀土的特 种合金。使用适量的镧合金，可获得大量不同的粒度 分布的石墨球。大的、初生石墨球数量略有下降， 中、小石墨球数量增加，这表明石墨在凝固过程中均 衡地析出，凝固后期石墨膨胀的作用较大。 将加有传统混合稀土的MgFeSi合金与加入镧的 MgFeSi合金加以比较，使用含镧合金的球墨铸铁 件，组织中大石墨球数量较少，中小石墨球数量较 多。图4显示了使用混合稀土处理的铸铁件中有大缩 孔，而使用镧处理的铸铁件没有问题。用保留一些 碳使其在凝固后期析出的方式，可保留膨胀作用，对 铸件收缩缺陷有深远的影响。铸件收缩倾向的最小化 在一定程度上与这样的组织相差，石墨球的粒度分布 广，而且多侧重于细粒。这一目标也可以通过使用专 利用的含硫氧复合物的孕育剂实现。


Fig. 8. Later, the designers opted for three bolts cast into the part that will be cut off and ground flat. The objective is to ensure a shrinkage-free struc- ture in that area of the casting without the use of a riser.


图8、稍后,设计师选择三个螺 栓置入该部位,并切断和磨平。 目标是确保这个部位不使用冒 口也能收缩自由。


May 2013 FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION | 35


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