Some practical aspects of nodularising treatment and methoding of ductile cast iron have been discussed in this paper. Quest for a material which can satisfy both the designer with its mechanical properties and the manufacturer for ease of manufacturing were partially fulfilled by malleable iron in the first half of 20th century. This class of material has yield strength and toughness of steel and castability of grey iron. But the high cost of annealing heat-treatment to decompose the cementite of white iron to graphite that precipitates as aggregates, restricted its application. The development of ductile iron in 1948, because of the ease of manufacturing due to elimination of costly and time-consuming annealing heat-treatment was enthusiastically accepted by the industry and gained wide-spread applications. The mechanical properties desired by the designer are achieved by treating liquid iron by adding magnesium as a result of which graphite precipitates as nodules during solidification of the casting. The resultant material has much higher elongation, hence ductility and the name "Ductile Iron".
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