Industrial silicon, also known as quasi-metallic silicon, is a commodity name that appeared in the mid-1960s. Metal silicon is the product of smelting silicon dioxide and carbonaceous reductant in submerged arc furnace. The content of silicon is about 98% (in recent years, 99.99% of silicon is also listed in metallic silicon), and the rest impurities are iron, aluminum and calcium. According to the contents of iron, aluminum and calcium, quasi-metallic silicon can be divided into 553, 44 1, 41,42 1, 3303, 3305, 2202, 2502 and150. By-products of quasi-metallic silicon include micro-silicon powder, edge-skin silicon, black-skin silicon and metallic silicon slag. Among them, micro-silica fume, also known as silica fume, is widely used in refractories and concrete industries.