Fading effect

The effect of inoculation and also the effect of magnesium treatment in production of ductile cast iron is temperature-related and of a temporary nature; this phenomenon is referred to as fading effect.

Above all, inoculation causes an imbalance in silicon distribution within the melt, i.e. occurrence of a “Si cloud”, which additionally promotes formation of the austenite / graphite eutectic. Slow and even distribution of the “Si particle cloud” within the melt causes the quieting or fading effects. These effects are manifested by reduction of the particle count on the one hand, and by the “Si particle cloud” disappearing as a result of diffusion, on the other hand, with the latter being the more important of the two consequences.

The driving force for diffusion is virtually zero and the particles are (although present) ineffective due to their small sizes.

Additional references:
Magnesium fading