Since the discovery of ductile iron, the principal treatment methods have all been centred on the use of magnesium and its alloys. Treatment methods have had to be developed to overcome some of the obvious difficulties in adding magnesium to liquid iron. Some of these include: Magnesium is lighter than iron and tends to float to the surface and burn in air. Magnesium has high vapour pressure and low boiling point at the normal iron treatment temperatures. This causes a violent reaction. Magnesium has low solubility and is difficult to dissolve in iron. Magnesium has high affinity for sulphur and oxygen causing excessive build-up in the treatment vessels. Magnesium fades over time due to reoxidation and evaporation resulting in loss of nodularity. Magnesium in high concentrations encourages the formation of carbides.
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