Plasma needs good electrical conductivity since the process is an arc generated at the point of cutting. The silicon is probably added for altering the magnetic characteristics (to prevent magnetic saturation) but the effect would be to lower the conductivity and that would cause problems in plasma cutting. It would depend on the thickness or material and being able to change the cut current to match the nedia and the distance from the workclamp to the actual cut.. Plasma is a pretty non-precision cutting process to begin with and gets worse if the media changes during a cut. OXy fuel has limitations as well. It won't cut non-Ferris metals but rather just melts them in ugly clumps. Waterjet works to cut just about anything from cakes to steel depending on what is added as an abrasive and it is pretty precise and it leaves no slag like plasma can. Only problem is that AWJ are expensive, take lots of power and cut slower than some other types. You have to figure out what to do with the contaminated sand/water and the consumables are pricey/