Every foundry is different on what nodulariser they want to use. Magnesium Ferrosilicon (MgFeSi) is used to make nodular/spheroidal graphite, aka ductile iron. Magnesium promotes the nodularization of graphite in iron. Low residual magnesium of .01-.025 in your casting will result in some flake graphite along with your nodular graphite. You want to target magnesium residuals of .035 to .055 for acceptable nodularity. If you get too high of residual magnesium in your castings, .06 or higher, especially on heavy section parts, you will end up with shrink. On thin-section castings, you can get carbides because magnesium is a carbide stabilizer.
The industry seems to be pushing foundries to lower magnesium content material to 4-5%, which results in a less violent reaction. The higher the mag content, the more violent reaction of a reaction you will get, typically 6-7% magnesium. The more violent reaction gives you less magnesium recovery, and the less violent reaction will result in better recovery. More calcium helps to suppress the reaction. However, iron only can absorb so much calcium so too much, and it acts as a slag generator.
Rare Earths (RE) can be critical to making quality ductile iron. Typical rare earths in MgFeSi’s are cerium, lanthanum, neodymium, and praseodymium. Rare Earths are used to tie up tramp elements such as antimony, lead, bismuth, or titanium that can occur in charge materials. These tramp elements can prevent the formation of nodular graphite by magnesium. Thus small amounts of RE are added to MgFeSi treatments as insurance against any occasional contamination. The typical rare earth in MgFeSi depends on the casting size. For heavy section castings, you will want a lower RE to prevent chunky graphite. Typical RE in MgFeSi is about 1%, and you will want to move to about 0.5% for heavy section castings.
Carpenter Brothers can help you select a proper nodulariser for your process. From a technical standpoint, Carpenter Brothers can help you determine what type of nodulariser fits your application depending on the type of castings you are pouring, the treatment temperature, and various other variables. Give us a call today.