Ferrosilicon and silicon slag are often mentioned together, but they are not the same product. One is a deliberately produced alloy. The other is a by-product. Knowing the difference helps buyers decide which material fits their process and budget.

Silicon slag is a by-product of smelting metallic silicon or ferrosilicon. It floats to the surface of the molten charge as a scum and still carries a meaningful amount of recoverable silicon. That residual silicon is why it is not treated as waste. For many steel mills and foundries, it is a practical, lower-cost raw material.