灰铸铁和球墨铸铁凝固过程中的几个问题

Some Problems with Solidification Processes of Gray Iron and Nodular Iron

详细介绍了灰铸铁和球墨铸铁的凝固过程,包括生核过程、初生奥氏体枝晶的析出过程以及亚共晶铸铁、过共晶铸铁、共晶铸铁的形成过程。阐述了初生奥氏体枝晶的形态和初生奥氏体枝晶对铸铁性能的影响以及对初生奥氏体枝晶的控制。分析了灰铸铁和球墨铸铁的共晶转变过程以及石墨的晶核。最终得出：（1）对于灰铸铁,组织中枝晶所占的体积分数提高,铸铁的强度随之提高;（2）对于球墨铸铁,初生奥氏体枝晶的数量和枝晶间距,对石墨球的形态、尺寸和分布状况有重要的影响;（3）将w（Al）量控制在0.005%~0.01%,既促进灰铸铁石墨生核,又不会诱发针孔缺陷;（4）采用含S、O的孕育剂可以使球化率提高、石墨球数增多、石墨球尺寸减小,从而提高球墨铸铁质量。

The solidification processes of gray iron and nodular iron were introduced in detail including：nucleation process,separating process of primary austenite dendrites,as well as the formation processes of sub-eutectic cast iron,super-eutectic cast iron,eutectic cast iron. The influences of the morphology of the primary austenite dendrite and primary eutectic dendrite on the properties of cast irons,as well as the control of the primary austenite dendrite were described. The eutectic transformation processes of gray cast iron and nodular cast iron and nucleus of graphite were analyzed. The following conclusions were obtained finally：（1）for the gray iron,with the volume fraction increasing of dendrites in the structure,strength of cast iron would increase;（2）for the nodular cast iron,amount of primary austenite dendrites and space between dendrites had important influence on morphology,dimension and distribution of graphite nodules;（3）it could promote graphite nucleation of the gray iron as well as will not cause pinhole defect to control the Al content in the range of 0.005%~0.01%;（4）using S and O-containing inoculant could improve nodularity,increase graphite nodule count,reduce nodule size and thereby improve quality of nodular cast iron.