Silicon slag 1. Silicon slag(off grade silicon) is a by-product when making silicon metal. 2. The silicon content is from 45% to95%,Website:http://www.ferrousalloy.com, and the rest are C, S, P, Al, SiO2, Fe, Ca etc. 3. The silicon slag is much cheaper than purity silicon metal, and has many industrial applications.Application 1. It is a good substitute for ferro silicon in steel making which has ...