Ductile Iron Thermal Analysis Sample Solidification Process And Melt State Assessment

The melt condition of the cast iron is one of the most important factors in determining the solidification microstructure and mechanical properties of the casting; it is significant to assess the melt condition exactly in foundry. Due to the nodularization and inoculation, the melt quality of ductile cast iron is extremely complex and difficult to assess. Characteristic temperatures of cooling curves thermal analysis is a familiar method in assessing the melt quality of ductile cast iron. However, there are still some questions which were neglected. Such as the effects of the characteristic temperatures by pouring temperatures and the weight of pouring, the relationships between characteristic temperatures of cooling curves and the graphite morphology of the thermal analysis sample and so on.In this paper, the solidification process of the samples was confirmed, and the physical significance of the characteristic temperatures of the thermal analysis curves was determined. With the method of variables controlled, the effects of the pouring temperature and pouring quality of the samples on the characteristic temperatures were studied, which were useful to determine the characteristic temperatures exactly. The results showed that both the pouring temperature Tmax and the pouring quality of the samples affected the value of△TE and TLN、obviously, but affected others characteristic temperatures less; the bigger value of Tmax, the bigger△TE and TLN; with the pouring quality increasing, the value of△TE increased, but the value of TLN decreased. So, it is important to pay attention to Tmax and the pouring quality in order to making the assessment results more exactly.The correspondences between the characteristic temperatures of cooling curve and graphite morphology were studied. The results showed that there were statistical laws between the characteristic temperatures, such as Tmax、TLN、TEU、TER、TE and△TE, and graphite morphology of the thermal analysis samples, but not linear relation. Therefore, characteristic temperatures cooling curves thermal analysis can be used in assessing the melt quality qualitative, but can not be used in quantitative analysis.In the end, with the method of holding temperature experiment, the fading process of ductile iron was studied systematically. These results indicate that characteristic temperatures of cooling curves could evaluate the melt quality and predict the graphite morphology of ductile cast iron qualitatively.