Internal quality of austempered ductile iron blank

The quality of ductile iron blank is the key to prepare high performance ADI material. The more graphite spheres are in the matrix of the blank, the smaller the eutectic group is, the smaller the microsegregation is, the more uniform the isothermal transformation products are, and the more stable ADI products with high strength and toughness can be obtained.

At the same time, in order to obtain high-quality nodular iron blank, the melting process of molten iron should be strictly controlled to ensure the reasonable and stable chemical composition of the blank; the molten iron should be pretreated and the inoculation technology should be adopted as many times as possible to improve the spheroidization rate of graphite (above grade 3), ensure the number of graphite balls (≥ 180 / mm2) and reduce the ball diameter (6 The number of intermetallic compounds (≤ 0.5%) and micro shrinkage porosity (≤ 1%) were decreased.