Y和Sb对厚大断面球墨铸铁石墨形态的影响

通过采用重稀土钇基稀土镁球化剂处理铁液,浇注厚大断面球铁试块,研究了重稀土Y和微量Sb对厚大断面球铁的石墨形态的影响,分析了石墨结晶的核心,并探讨了石墨畸变的原因。试验结果表明,重稀土Y在铁液中形成高熔点氧化物,残存时间长,作为石墨核心,有利于提高抗衰退性能;Sb具有细化石墨球、增加石墨球数、提高石墨圆整度的作用;在厚大断面球铁中,晶界上Ti的偏析和球化元素Mg或稀土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。

Effects of Y and Sb on Graphite Morphology of Heavy Section Nodular Iron

By treating the iron melt with Y-based REMg nodularizing alloy and pouring heavy section nodular iron testblocks, the effects of heavy rare earth Y and trace amount of Sb on the graphite morphology of heavy section nodular cast ironwere investigated. The crystallization nucleus of graphite were analyzed, and the reason causing graphite degeneration wasdiscussed. Test results showed that heavy rare earth element Y formed high melting point oxides which could exist for a longtime in the melt and could be as the nucleus of graphite so that it is beneficial to increase the anti-degeneration property ofthe nodular iron. Sb has the effect to reduce graphite size, increase nodule count and improve roundness of the graphitenodules. The Ti segregating at grain boundaries together with the oxide inclusions of nodulizing elements Mg and REdestroyed stability of the austenite shells and so that the graphite degeneration was caused.