Spheroidal graphite cast iron property enhancement by heat treatment

Ductile iron, popularly known as spherodized graphite iron (SGI), is a special variety of cast iron having carbon content more than 3 wt.% and has graphite present in compact, spherical shapes. These compact spheroids hamper the continuity of the matrix much less than graphite flakes, which results in higher strength and toughness with a structure that resembles gray cast iron, thus imparting superior mechanical properties. The high ratio of performance to cost which they offer to the designer and end user makes them used extensively for industrial applications. The basic chemical elements such as carbon, silicon, manganese, magnesium, copper etc. play an important role in the SGI casting process. The behavior of these elements in molten metal of the ductile iron varies because of their different mechanical and chemical properties. However, to extend the consistency and range of properties of SGI castings beyond its properties in the as-cast condition, heat treatment is a necessary operation. In this research specimens are prepared with different combinations of alloying elements. On these specimens studies are performed with various tests to understand the effect of heat treatment operations such as tempering and austempering to transform the brittle behavior to ductile behavior.