The sandwich method for nodularisation

After treatment, the metal has to be poured into the mould within a specific time, as the Mg effect tends to fade quickly, necessitating a new treatment if a certain time limit (10 to 15 min) is exceeded. 

The presence of coarse shaped graphite in a metal matrix leads to poor mechanical properties of the material. In order to get a fine crystalline metallurgical structure, inoculation of the melt is necessary prior to casting. This process introduces seeds for crystal growth into the metal melt. Usually FeSi alloys are used for this purpose. Ca, A1 and rare earth materials are often included in the inoculant. 

several techniques can be used to inoculate the molten metal  

Injection during tapping Here the inoculant is injected directly into the metal flow during tapping 

There are three main metal treatment (or refining) operations carried out in aluminium melting 

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