微量元素偏析对厚大断面球铁石墨形态的影响

分析了厚大断面球铁件石墨畸变的形成原因及影响因素,浇注了400mm×400mm×450mm的试块研究微量元素偏析对石墨形态的影响。结果表明：开花状石墨的中心部存在Mg、Al、La、Ca、S等元素的富集,这些元素的富集破坏了石墨生长的稳定性;而晶界上V、Ti的偏析和球化元素Mg或RE等氧化形成的氧化夹杂,破坏了奥氏体壳的稳定性,造成石墨畸变;在铁液中添加微量Sb,凝固过程中Sb偏析于石墨—奥氏体界面上,可有效抑制或减缓C向石墨球扩散,限制石墨球生长,抑制石墨球畸变。

Influence of Trace Elements Segregation on Graphite Morphology of Heavy Section Nodualr Iron

The reasons causing graphite degeneration of heavy-section nodular iron castings and degeration-influencing factors were analyzed,and test blocks with dimensions of 400 mm× 400 mm×450 mm were cast to investigate the influence of the trace elements segregation on graphite morphology. The results showed that there is the enrichment of elements such as Mg,Al,La,Ca,S etc. at the central area of the exploded graphite which destroyed the growth stability of graphite;the segregation of V and Ti,as well as the oxide inclusions formed from nodularizing element Mg or RE, et. on the grain boundaries destroyed stability of austenite shells causing graphite degeneration. However,it’s possible by adding trace amount of Sb,to restrain or effectively delay carbon diffusing onto the graphite so that it’s possible to restrict the graphite nodule growth and restrain degeneration of graphite.