The Validation of solidification shrinkage models for Ductile Iron Casting

摘要

In this study, two solidification shrinkage models were validated by three feeder designs of ductile iron castings. It was found that the so called First Principle model is a model not only tracking the isolated liquid region in 3 dimension but also considering the residual liquid flowing and the volumetric expansions of spheroidal graphite during the solidification of ductile iron castings. After casting the three feeder designs of ductile iron castings, the hardness in every 5 mm distances within the central cross-section of the three castings were measured. The actual shrinkage contour and locations on the central plane of the castings were discovered. It shows that the shrinkage profile and locations predicted by the modeling are the shape and places where the residual liquid in the lowest liquid level within an isolated regions during solidification. The difference of shrinkage profiles between the actual casting and the modeling were explained. Applying the validated model (First principle model), an optimized feeder design (with a modulus of 17.84mm) for cube-shaped cast with a modulus of 16.67mm was found. In this optimized feeder design, the modulus ratio of the feeder and cast is 1.07 which is much lower than that required by short feeding range alloy. This implies that the graphite volumetric expansion somehow helps the feeding of ductile iron casting. In this feeder design, its feeding efficiency is 12.21%. In tuning carbon simulation, a precise carbon composition can be predicted by the modeling.