球墨铸铁中碎块状石墨的形成原因及防止措施  

Reason Causing Chunk Graphite Formation in Nodular Iron and Measures to Prevent Their Formation

作　　者：程凤军 高顺 莫俊超 张俊新[2] 杨志刚 

机构地区：[1]常州南车汽车零部件有限公司,江苏常州213011 [2]南车戚墅堰机车车辆工艺研究所有限公司,江苏常州213011

出　　处：《现代铸铁》2015年第3期29-34,共6页Modern Cast Iron

摘　　要：介绍了碎块状石墨的形貌特征,详细分析了球墨铸铁中碎块状石墨的形成原因,认为碎块状石墨的形成与石墨、奥氏体的析出先后顺序有关:当铁液在凝固过程中初生石墨或共晶石墨形核能力差或已析出核心再溶解,石墨球不易形成,从而导致奥氏体在铁液中优先析出,残余液相中的w(C)量不断增加,最终过饱和C原子在残余液相中快速共晶析出石墨分支,形成碎块状石墨,并分布在奥氏体枝晶间。Ni、Si合金元素含量高、残余RE含量高、凝固时间长、孕育不良均会促进球墨铸铁碎块状石墨的形成。根据碎块状石墨的形成原因和影响因素,提出了采取强化孕育、强化冷却、控制w(RE)量等有效防止措施。The morphological characteristics of chunk graphite were introduced and the reason causing chunk graphite formation in nodular iron was analyzed in detail. It was considered that the formation of chunk graphite was relevant with the separating order of graphite and austenite：when the nucleation capability of the primary graphite or eutectic graphite during the solidification process of iron melt was relatively weak or the separated nucleus were re-dissolved,the graphite nodules formation would be not easily that would cause the austenite separate firstly in the iron melt and the carbon content of the residual melt would increase continuously and,as the result,the supersaturated carbon atoms fast separate as eutectic graphite branch which forming the graphite chunks and distributing between the dendrites. The high content of alloying element Ni,Si,high content of residual rare earth,long solidification time and non-sufficient inoculation were the factors to promote the chunk graphite formation in nodular iron. Based on the reason and influence factors of the chunk graphite,it was proposed to adopt the effective preventing measures including intensifying inoculation,intensifying cooling,controlling rare earth content.

关 键 词：球墨铸铁 碎块状石墨 奥氏体枝晶 合金元素 

分 类 号：TG255[金属学及工艺—铸造]