It is main used in foundries. As you know the cast iron contain C: 2-4%, Si: 1-3%, and Carbon and silicon are the main elements affecting the microstructure of cast iron.High Carbon Silicon has made carbon alloyed in it, so it can provide the two elements effectively. Lately it also be used in steel making, especially steel scraps melting. It serves as deoxidizer and efficient heating agent (Si&C: 6.58kcal/g, 1.24kcal/g each) and recarburizer. With Si&C at least 90%, the impurity is very less, so the input is easy to control.