The results presented in this paper are a continuation of the previously published studies. The results of hest treatment of ductile iron with content 3,66%Si and 3,80% Si were produced. The experimental castings were subjected to austempering process for time 30, 60 and 90 minutes at temperature 300o C. The mechanical properties of heat treated specimens were studied using tensile testing and hardness measurement, while microstructures were evaluated with conventional metallographic observations. It was again stated that austempering of high silicone ferritic matrix ductile iron allowed producing ADI-type cast iron with mechanical properties comparable with standard ADI.
Ductile iron casts with a higher silicone content were produced. The austempering process of high silicone ductile iron involving different austempering times was studied and the results presented. The results of metallographical observations and tensile strength tests were offered. The obtained results point to the fact that the silicone content which is considered as acceptable in the literature may in fact be exceeded. The issue is viewed as requiring further research.