Producing light weight ductile iron casting by reducing the thickness of casting to approximately (2-3mm) withhigh strength/weight ratio and better mechanical properties make thin wall ductile iron casting (TWDI) an economical alternative to cast aluminum components. It also makes possible the conversion of many steel assemblies to ductile iron due to its higher yield stress/cost ratio. Inoculation treatment is very important because it improves the homogeneity of the cast iron structure. It helps to eliminate the formation of carbides into thin parts and promote the formation of graphite during eutectic solidification. It also direct the solidification towards graphite precipitation, refine the structure (higher cells count, finer grains in the microstructure. The amount of pearlite is influenced by both alloying elements and cooling rate.The brinell hardness increases exponentially as the pearlite content is increased. Faster cooling rate results in higher nodule count. In other words, thinner sections will have higher nodule count.Austempering heat treatment was generally done by heating the sample slightly above the austenitizing temperature and holding it in the austenitizing range for sufficient time and then the sample is quenched in proper medium maintained at austempering temperature and holding it for sufficient time for the isothermal transformation, and further cooled in air to room temperature.
The hardness remains more or less same with slight variation with change in the austempering time at each austempering temperatures. This shows that even 2 minutes austempering time is sufficient for transform the structures.
The yield strength and ultimate tensile strength (UTS) of thin wall austempered ductile iron (TWADI) inoculated by Ce-Ca-Al-S-O-FeSi at 0.4 % inoculation are higher and ductility and impact strength are
lower than that of as-cast thin wall ductile iron (TWDI) plates. This may be attributed to the change in the structure change from ferrite-pearlite to austenite-bainite.
The hardness value remains more with austempering temperature at 4000 C for 2 min., for 2 mm thick plate compare to 3 mm thick plate with austempering temperature at 350 C and 450 C for 2 min. This may result due to comparatively finer baintic structure.