电磁场对铸铁石墨生长的影响

Effect of Electromagnetic Field on Graphite Formation in Cast Iron

设计了交替换向的行波磁场,研究在铸铁凝固过程中,施加换向行波电磁场产生的脉冲作用对铸铁石墨生长及其凝固组织的影响·结果表明:在脉冲电磁场的作用下,灰铸铁凝固组织中奥氏体枝晶数量明显减少,石墨粗化;球化处理后,凝固组织中球状石墨数量减少,蠕虫状石墨增多,蠕化率显著提高,为稳定蠕墨铸铁的蠕化率提出一个新途径·讨论了电磁场对石墨生长影响的机理,认为脉冲磁场的电磁搅拌作用和感生电流的热效应破坏了石墨核心周围奥氏体壳的稳定性,促进石墨的分枝生长,形成蠕虫状石墨·只有在残留镁量和残留稀土量足够或残留量较高时,脉冲磁场的干扰能够稳定蠕化率;蠕化剂加入量不足时,磁场干扰只能促进形成片状石墨,不能形成蠕虫状石墨·

A pulse (commutative traveling wave) electromagnetic field was designed as an experimental setup for solidification, where the effect of pulse electromagnetic field on the graphite in cast iron in solidification process and its solidified microstructure was investigated. The results showed that in solidified grey cast iron the number of austenite dendrites reduced clearly with graphite coarsened. After nodulizing process, the number of nodular graphite decreases and the rate of vermicular graphite increases greatly. A new approach to stabilizing the rate of vermicular graphite of compacted graphite cast iron is thus proposed. Discuss the mechanism how the electromagnetic field affects the formation of graphite. The effect of electromagnetic stirring of electromagnetic field and thermal effect of induced current are regarded as able to damage the stability of the austenite shell around graphite cores, thus bring about the growth of branched graphite to form vermicular graphite. The interference of pulse electromagnetic field can stabilize the rate of vermicular graphite only if the residue of Mg and Re is sufficient or nearly sufficient, otherwise, the insufficient Mg and Re as additives will cause the interference to form flake graphite.