孕育剂对铸态可锻铸铁组织及退火工艺的影响

Effect of Inoculant on Microstructure and Annealing Process of As-cast Malleable Cast Iron

对铸态可锻铸铁的孕育机理及石墨化退火工艺进行了研究。结果表明:微量元素Bi、Sb、B的加入,增加了凝固过程中石墨的形核率,促进珠光体形成,并使石墨化退火过程中共析渗碳体分解速度加快;合理选择铁液成分,并经Bi、Sb孕育及Sb-B和Sb-B-RE复合孕育处理,可获得基体基本为珠光体的铸态可锻铸铁;采用Sb-B-RE和Sb-B复合孕育处理石墨更为细小;复合孕育处理的铸态可锻铸铁经740℃保温4 h的石墨化退火处理,可得到铁素体基可锻铸铁;若铸态组织中存在少量莱氏体,应770℃保温1 h,以消除渗碳体,再进行740℃保温3 h的石墨化退火处理。

The study has been made of the inoculation mechanism and the graphitizing annealing process of ascast malleable cast iron, of which results indicated that as the microelements-Bi, Sb,B added, the nucleating rate of graphite in solidification process increased; the formation of pearlite promoted and the decomposition of eutectoid cementite in the graphitizing annealing process accelerated. As selecting suitably compositions in melted iron; adopting the inoculation treatment with Bi,Sb and the compound inoculation treatment with Sb-B and Sb-B-RE. the as-cast malleable cast iron was obtained, of which the pearlite is as matrix basically, especially the graphite slices was finer in the latter process, the as-cast malleable cast iron with the ferrite as matrix was obtained after the graphitizing annealing 4 hours at 740℃ on the compound inoculated as-cast malleable cast iron. as a little ledeburite in the cast structure existed, it was heated to eliminate the cementite 1 hour at 770℃, following the graphitizing annealing 3 hours at 740℃.