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一些工厂在生产中磷铸铁厚大件时遇到缩松严重、机械性能差等问题。其原因是铸件越厚,冷速就越慢,晶粒和石墨片就更粗大,晶间缩松也更严重,这样就使晶界减少,晶粒间联系受到破坏,从而导致铸件强度的下降。而这种厚大件的缩松在生产上使用较大的冒口也难以消除。那么是否可以用其它办法消除缩松,提高铸件的强度呢?我们为此做了十次试验,其结果说明利用铸铁的“自补缩”作用(具体措施就是提高铸型刚度)就可以达到在粗晶的情况下消除缩松,提高铸铁强度的目的。甚至还能做到在成分相同(同一包铁水)的情况下,粗晶试棒比细晶试棒(晶粒大小相差9.5倍)
Some factories encounter severe shrinkage and poor mechanical properties in the production of large castings of phosphorus cast iron. The reason is that the thicker the casting, the slower the cooling rate, the coarser the grains and the graphite sheets and the more severe the intergranular shrinkage, so that the grain boundaries are reduced and the intergranular connection is destroyed, resulting in a decrease in the strength of the casting . And this thick piece of shrinkage in the production of larger riser is difficult to eliminate. So can we use other methods to eliminate shrinkage and improve the strength of the cast? We did ten tests for this, the results show that the use of cast iron “self-shrinkage” effect (specific measures is to increase the mold stiffness) can be achieved in The case of coarse grain eliminate shrinkage, improve the strength of cast iron purposes. Even in the case of the same composition (same hot metal), the coarse-grained test bars are 9.5 times larger than the fine-grained test bars (grain size)