添加钛、铌、锰、硫及镁对亚共晶灰铸铁初生奥氏体形核及生长的影响

Effects of Addition of Ti,Nb,Mn,S and Mg on Nucleation and Growth of Primary Austenite in Hypo-Eutectic Cast Iron

共晶铸铁在共晶凝固时,熔体中碳的状态,即"C的微小集合体"已经被深入研究。然而对于与初生奥氏体密切相关的铁原子的状态,即"铁的微小集合体"却缺乏研究。本文作者提出,在亚共晶灰铸铁熔体中,初晶γ的形核受"Fe的富集部"的影响,而"Fe的富集部"的形成及消失与"C的微小集合体"有关。研究表明,初生奥氏体的形核过冷度、形核数和晶核生长形貌随工艺条件如过热度、保温时间和冷却速率而变化。本文讨论了在熔体的过热度、保温时间和冷却速率固定的条件下,钛、铌、锰、硫和镁这五种添加元素对亚共晶灰铸铁初晶γ的凝固过程的影响。

As a part of studies on the eutectic solidification from cast iron melts of eutectic composition,the state of carbon in melts,or ＂the carbon-microgroup＂,has so far been investigated considerably.However,little has been mentioned on the state of iron atoms as solvent for primary austenite,or ＂an enriched region in Fe＂.The present authors have suggested that in melts of hypo-eutectic gray cast iron melts the ability of primary γ nucleation is affected by the state of ＂an enriched region in Fe＂ that appears and disappears according to the formation of ＂the carbon-microgroup＂.They have shown that the degree of undercooling for nucleation,nucleation number and nucleation-growth morphology of primary γ crystals vary with fundamental experimental conditions such as superheating temperature,holding time,and cooling rate of cast iron melts of hypo-eutectic composition.In the present study,the effect of addition of titanium（Ti）,niobium（Nb）,manganese（Mn）,sulfur（S） and magnesium（Mg） on the solidification of primary γ crystals have been investigated,fixing the fundamental conditions（superheating temperature,holding time and cooling rate） for cast iron melts.