Isothermed ductile iron (IDI)

Isothermed ductile iron (IDI) is obtained by heat treating ferritic spheroidal graphite iron without the addition of costly alloying elements. In terms of efficiency and cost-savings, IDI is an extremely valid solution for the manufacture of very thick parts requiring high levels of static and fatigue strength, such as pump heads for hydraulic applications, steering knuckles and centre bodies for axles.

The mechanical properties of isothermed ductile iron (IDI) are intermediate between those of pearlitic ductile iron and austempered ductile iron: IDI offers higher performance than GJS ductile iron and is more cost-effective than austempered ductile iron (ADI).

The structure of the matrix in isothermed ductile iron (IDI) consists mainly of ferrite and pearlite, two elements, which, thanks to a different distribution with respect to traditional spheroidal graphite irons, increase the mechanical performance of finished castings.

Isothermed ductile iron (IDI), in particular when used for very thick castings, represents a valid technical and economic compromise for the production of parts that need to overcome technical and production limits, and the relative cost of alloying elements, pearlitic ductile irons, new high silicon ductile irons and austempered ductile irons.

IDI therefore represents a valid alternative with respect to GJS800-2, ADI800-10, GJS600-10. With machinability comparable to that of pearlitic ductile irons commonly used in mechanical machine shops, IDI is also suited to mechanical processing. It has a mixed ferritic-pearlitic structure, which means it can also be surface hardened only where necessary, thus increasing the wear resistance of parts.

benefits of isothermed ductile iron (IDI), we highlight:

• Lightness: the specific weight of IDI is 10% lower compared to steel, thus allowing vehicles to either increase their maximum load or reduce fuel consumption;
• Complex moulds: thanks to the melting technology and excellent castability, the material can be applied only where necessary;
• Fatigue strength: in terms of performance, it is comparable to that of pearlitic ductile irons;
• Cost-saving: no alloying elements are required;
• Resilience: even at low temperatures (up to -40°C), the material guarantees consistent mechanical performance in very thick cast parts or those with variable thickness.

The values reported into the table are relative to separately cast samples and having relative wall thickness 30 mm.