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One Minute Mentor: Normalizing ductile iron

February 06, 2019
Source: ASM International

Normalizing (air cooling following austenitizing) can result in a considerable improvement in tensile strength and may be used in the production of ductile iron of ASTM grade 100-70-03, which is shown in the figure. The microstructure obtained by normalizing depends on the composition of the castings and the cooling rate. The graph shows hardness versus strength and ductilityof ductile iron.


The composition of the casting dictates its hardenability, that is, the relative position of the fields in the time-temperature CCT diagram. The cooling rate depends on the mass of the casting, but it also may be influenced by the temperature and movement of the surrounding air during cooling. Normalizing generally produces a homogeneous structure of fine pearlite, if the iron is not too high in silicon content and has at least a moderate manganese content (0.3 to 0.5% or higher).


Subject Classifications

Materials Processing and Treatment | Heat Treating

Metals and Alloys | Cast Irons

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