核心形状对石墨球化的影响

研究了低碳球铁中球状石墨的内部结构及核心形状，探讨了核心形状对石墨球化的影响规律。研究表明。核心的存在是石墨形核长大的基础，而核心形状对石墨的最终形状起着至关重要的影响；球形或接近球形的石墨核心长大后大多都能保持原来的球状，形状不规则的核心，则很难长大成为圆整的球状石墨。但是，铁水中如果只有气泡或球形核心存在，而没有足够的粘度、压力、过冷度和较高的表面能以及吸附等其它充分条件的配合，这些核心仍然很难长大成为球状石墨。也就是说，凡是有利于铁水中形成球形核心，并有利于这种核心在各个方向均匀生长的因素。都可看作是促进石墨球化的因素，反之亦然。研究还表明，表面活性元素的球化和反球化作用不是绝对的，在一定条件下它们可能会相互转化。传统理论中认定的球化和反球化元素，实际上并非在各种不同条件下都能促进或破坏球化。因此。有必要根据实际情况对球化元素与反球化元素进行重新界定。

The Influence of the nucleus' shape on the graphite spheroidizing

Through the study on both the internal structure and the nucleus shape in low carbon ductile iron, influencing regularity of the nucleus shape on the graphite spheroidization has been discussed. The study indicates that existence of the nuclei is the basis of nucleation and the growing of the graphite, the nucleus shape has great influence on final shape of the graphite. Most nuclei with spherical or near spherical shape can grow up into spherical graphite, while nuclei with no regular shape can hardly grow up into spherical graphite. However,if there are only bubbles or spherical nuclei, but no suitable stickiness, pressure, under cooling, surface energy and adsorption in the iron melt, it is still very difficult for the nuclei growing into the spherical graphite. That is, all factors favorite in both forming spherical nuclei and growing in all directions in the iron melt can be regarded as factors promoting graphite spheroidization.The study also shows that surface activated elements have actions both in spheroidizing and anti spheroidizing, however such actions are not absolute, they can be converted mutually in certain condition. In fact, not all the traditional spheroidizing or anti spheroidizing elements can promote or destroy the spheroidizaton process in all conditions, therefore, it is necessary to re recognize the spheroidizing and anti spheroidizing elements according to the solidification condition.