Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Improved knowledge of ductile iron

Improved knowledge regarding micro-alloying of ductile iron:
Ductile iron has traditionally been classified and standardised according to its strength and ductility. In general the different strength and ductility levels has been achieved by alloying to control the ferrite/pearlite balance in the iron. Alloying has mainly been based on elements that alter the transformation behaviour in the material, typically due to retarding the diffusibility of carbon in the matrix.

In addition large amount of work has been done to increase the number of graphite nodules per unit volume and to control the size and shape of the graphite nodules. In the later years very high strength ductile irons have been produced after a long and very expensive heat treatment. The current project aims at establishing micro-alloying as an alternate route to strength enhancement in ductile iron.

The main advantages include significant strength enhancement in the as-cast condition, with no or very little heat treatment, by utilising micro-alloying. Initial results have shown that micro-alloying of ductile iron provides an iron with increased as-cast mechanical performance. Yield strength of higher than 520MPa has been achieved in as-cast ferritic ductile iron. Models to explain the underlying mechanisms are being developed to provide tools to control the microstructure evolution and the resulting mechanical properties.

FEM-based mathematical model that can accurately predict microstructure and mechanical properties in ductile iron:

A FEM-based software code is being developed to accurately predict the microstructure evolution in micro-alloyed ductile cast iron. The applied microstructure model draws together established knowledge of thermodynamic and kinetic theory with experimental data to describe the microstructure evolution during casting. The microstructure predictions are connected to mechanical property predictions using empirical equations that take into account the chemical composition, volume fraction of the different microstructural components and the actual cooling rate.

Reported by

The SINTEF Group
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