Alloy for the production of nodular graphite cast iron (s. Magnesium treatment). Due to its high steam pressure it is not easily possible to add pure magnesium to the liquid iron. For this reason, so-called master alloys which, in addition to magnesium, contain specific heavy metals are used. Some examples are given in the following:
In practice, treatment alloys on the basis of FeSiMg containing calcium are used predominantly. The calcium addition in the FeSiMg treatment alloys is required because the calcium decreases the steam pressure of the magnesium and thus mitigates the reaction with the cast iron melt. Moreover, these alloys may also contain cerium or cerium mixed metal and/or rare earths in contents of 0.25 to 2.50%. This has certain advantages as cerium and rare earths reduce the influence of interfering elements (mainly lead, bismuth, titanium) on the graphite nodularization.
Leading manufacturers of magnesium master alloys are, amont others, ASK Chemicals Metallurgy GmbH, Unterneukirchen; ELKEM Foundry Products, Oslo, Norway; GfM Fesil, Duisburg; Foseco Foundry Division Vesuvius GmbH, Borken Germany.