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.