Vorkonditionierung von Sonder-Gusseisen zur Erhöhung der eutektischen Graphitausscheidungen

The main purpose of the investigations was to compare the amount of graphite produced by different preconditioning agents with respect to the suitability for the production of highly-alloyed indefinite cast iron. The highly-alloyed indefinite cast iron belongs to the type of mottled cast iron. Graphite as a microstructural component of mottled cast iron can positively influence its feeding, as well as ist dry wear properties in addition to other properties. The adjustment of graphite components in mottled cast iron requires special measures in order to produce graphite in the rapidly cooled, or even high-alloyed indefinite cast iron by means of a suitable inoculation method. This work investigates the effects of preconditioning and ladle inoculation on highly-alloyed indefinite cast iron. An induction furnace was used to produce cast samples. The melt was preconditioned in the induction furnace, the inoculation was carried out in the ladle after casting. Combinations of 5 preconditioning additives and 3 inoculants were tested in two series of experiments. For sample preparation, segments were removed from the mould and processed to obtain metallographic cross sections. The results show a remarkable increase in the amount of graphite compared to casting methods without preconditioning agent considering the cementite matrix. The preconditioning also has a positive effect on the increase in „graphite nodule count“ and „graphite area“. Especially Zr- or Ce- containing master alloys as well as higher amounts of SiC produced an increase in graphit area in the highly alloyed indefinite iron in form of vermicular graphite.