Magnesium Ferro Silicon Alloys are a type of ductile iron additive that is added to molten cast iron during the nodularization process. Typical treatment methods include pour-over, sandwich and tundish. They can be used for ductile iron castings with a variety of shapes and sizes.
These additives are characterized by the presence of magnesium, rare earth elements, and a combination of silicon, calcium, and aluminum as an impurity. The chemistry of these additives is carefully formulated for each application, and the alloys are tested before being released to market.
Various ranges and types of these additives are available, ranging from 3 to 4 percent magnesium for low reactivity and high magnesium recovery, to 5 to 6 percent magnesium for normal practices. The reactivity level is dependent upon the method of treating the iron, and the magnesium addition rate.
The reactivity of these additives can be easily controlled by changing the treatment time and temperature. For example, if the treatment is carried out in an airtight reaction chamber, the dissolution of magnesium can be controlled by controlling the time of entry to the chamber and the duration of the addition.
In many cases, the reactivity of the alloy can also be controlled by altering its molecular weight. This can be achieved by either modifying the magnesium content, or increasing the concentration of silicon and calcium, or by reducing the amount of aluminum.
Different levels of magnesium can also be selected depending on the desired nodularity. The level of magnesium can be influenced by the type of ductile iron to be treated, the quality and consistency of the charge materials, and the treatment method being used.
A variety of chemistries and sizes are available in a variety of rare earth compositions and ranges to suit all types of ductile iron castings. These chemistries and sizes can be used for a variety of treatment processes, including pour-over, sandwich, tundish, flow-through and in-mold.
These alloys can be prepared by plunging solid magnesium into a nominal 75% ferrosilicon alloy. The resulting alloys can then be melted and recast in a mold. In this manner, the alloys can be readily matched to each specific casting.
Some of these alloys are referred to as "deleterious" because they contain titanium. However, it is important to understand that the titanium in these alloys does not inhibit nodularity but rather promotes nucleation of new graphite platelets in the liquid resulting in a uniform distribution of nodules in the final casting.
The reactivity of these alloys can be controlled by altering the magnesium content, or increasing the concentration of silicone and calcium, or by reducing the amount or weight of aluminum.
In many cases, the chemistry of these additives can be easily controlled by altering the magnesium content, or by increasing the concentration of silicon and calcium, or reducing the amount of aluminum.
For example, if the treatment is carried over in an airtight reaction chamber, the molecular weight of magnesium can be controlled by either modifying the magnesium content, or by increasing the concentration or size of silicon and calcium, or by reducing or eliminating the amount of aluminum.
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