Andrzej Gazda

Determination of the optimal austempering parameters of Ni-Cu (Mo,Mn) ductile iron based on CCT and TTT diagrams


In the research, a complex procedure was performed to determine the optimal parameters of thermal treatment of ductile iron with Ni, Cu, Mo and Mn additions which underwent austempering in order to obtain the ADI cast iron. Based on the constructed CCT and TTT diagrams, the basic heat treatment parameters were determined, i.e. the austenitizing temperature and time, the critical rate of cooling down to the isothermal transformation temperature and - for the selected values of the austempering temperature - the austempering times. It was established that, for the isothermal transformation temperature above 400°C, the processing window is closed.
The analysis of the TTT diagram makes it possible to select the time of the isothermal transformation in complex cyclic variants of the ADI thermal treatment.

Keywords: ADI, ausferrite, CCT diagram, TTT diagram,
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