铸铁一次结晶时球状石墨生成的机理

通过采用液淬——热分析方法得出：1.球墨不仅可以从液相中直接析出，而且还可以保持完好的现状（当球化处理充分时）独立长大；在过共晶铸铁中，奥氏体是在共晶转变时才从液相中析出，并优先在石墨球表面生长。2.当球化处理不充分时，石墨球还处在液相中自由生长阶段，在无其它固相的参予情况下就会自行产生畸变。3.在未经球化处理的低S铁水中，石墨首先以小球状（3～5）微米析出，而后在其表面开始生“角”，随硫量的增高这一现象加剧，在液相中长成“爪”状石墨。本工作用过饱和析出法，揭示出石墨表面的螺旋晶及其台阶；经球化处理的石墨呈球状，其表面为取向不同的螺旋晶。本工作还用液淬——热分析法揭示出，在亚共晶铸铁中石墨球是在由于球化、孕育处理所导致的不平衡状态下，以过共晶形式从液相中析出。用插硅及微区光谱分析方法确定了这一成分起伏的存在。在实验结果分析的基础上，笔者试提出铸铁一次结晶时石墨成核、生长（球、畸变、片）的模型、对球化元素作用及反球化元素作用机理提出论点并对孕育机理提出新的看法。

The mechanism of spheroidal graphite formation during primary crystallization of cast iron

Following results were obtained in present work by using thermal and structural methods: 1.Graphite spheroid was formed directly from liquid phase, and was grown independently keeping complete spheres when modification was optimum. In hypereutectic cast iron austenite was formed only during eutectic trasformation and primarily was grown on the surface of the graphite sphere. 2.When modification was not optimum the graphite spheres (being on the stage of free growth) distorted themeslf when there were not any other solid phases. 3.In the low S iron melt which didn't have modification the graphite was formed at first in the shape of small spheres (3-5micron), and then the graphite grows "horn" on it's surface. This phenomenon became stronger in consequence of the increase of S, and the graphite grows in the shape of "paw". By using oversaturated formation method it was found on the graphite surface the appearance of screw crystal and it's steps. The graphite which had been modificated kept spheroidal in shape and on it's surface screw crystals with different orientations could been seen. By using thermal and structural methods this work discovered that in hypoeutectic iron which was in non-equilibrium state the graphite spheres were formed from the hypereutectic liquid phase. The non-equilibrium state was caused by modification and inoculation. By putting in the silicon and using local-spectroscopic analysis determined the occurrence of local fluctuation of compositions. On the basis of the analysis of the experimental results the author proposed the models of the embryo and of the growth of the graphite during primary crystallization of cast iron. In this paper the author expressed his opinions on effect of the sphericized elements and the anti-sphericized elements and propounded the mechanism of inoculation.