球墨铸铁件微观组织的数值模拟

根据凝固动力学理论，建立和完善了球墨凝固过程中各阶段组织形成的数学模型。用试验试件进行了验证，并对实际生产球墨铸铁件的球墨数量和大小、珠光体和铁素体数量、硬度等进行了模拟，与定量金相分析结果进行了比较。结果表明模拟结果与分析结果吻合较好，同时，共析模型尚有待进一步改进以更准确地预测珠光体和铁素体数量。研究表明：球墨的形核与生长主要与过冷有关，共析阶段产生的珠光体与铁素体体积分数则由过冷度与球墨个数两者所决定。

NUMERLCAL SLMULATION OF MICROSTRUCTURE OF SPHEROIDAL GRAPHITE IRON CASTINGS

On the basis of solidification kinetics, the mathematical model of microstructure formation formation of spheroidal graphite cast iron is established, improved and verified with the sample castings. In addition, nodular counts and diameters, contents of pearlite and ferrite, and hardness of practical automotive spheroidal graphite iron castings are simulated with the model and compared with results of quantitative experiment analysis. The comparison indicates that both simulated results and experimental results agree well with each other and the model of eutectoid transformation should be improved to predict contents of pearlite and ferrite more accurately. Besides, it is concluded that the nucleation and growth of graphite spheres are mainly determined by cooling rate during eutectic transformation while the contents of ferrite and pearlite are governed by both the super-cooling of eutectoid period and nodular counts of eutectic solidification.