试样壁厚对振动消失模铸造球墨铸铁组织的影响

采用振动消失模铸造的方法制得阶梯形球墨铸铁,利用光学显微镜对球墨铸铁中的石墨形态及基体组织进行观察,借助图像分析软件对石墨球的数量进行定量分析。通过比较分析的方法,研究了试样壁厚对球墨铸铁的石墨形态及基体组织的影响。结果表明,随着试样壁厚的增大,石墨球的个数先减少后增多,基体组织则先变得粗大,尔后变得细小,并且在壁厚为60mm的试样中石墨球数较30mm厚的试样增加了69.5%。石墨形态及基体组织的变化主要应归因于试样壁厚的增大降低了试样的冷却 速度,延长了振动对凝固组织的作用时间,增强了振动力对结晶组织的“黏性剪切”作用。

Effect of Wall Thickness on Microstructure of Ductile Iron Using Lost Foam Casting with Vibration

A ladder specimen of ductile iron was made by LFC with vibration.Graphite morphology and matrix microstructure were observed by means of optical microscope,and the numbers of spheroidal graphite were analyzed by image analysis software.Effect of wall thickness on the graphite morphology and matrix microstructure was investigated.The results show that the numbers of spheroidal graphite first decrease and then increase,and the matrix microstructure first becomes larger and then gets refiner in the thicker specimens than in thin ones.In addition,the number of spheroidal graphite in the 60mm thickness specimen increases by 69.5% compared with the 30mm thickness specimen.The main reason of  the graphite morphology and matrix microstructure changing is that the cooling rate of the specimen is lower and active time of vibration on the solidification microstructure is prolonged with increasing of wall thickness.Besides,vibration force increases the role of  “viscous shear” on crystallization structure.