Steel wool is an alloy of iron (Fe) with carbon (C) rather than a chemical compound, thus it does not have a chemical formula. The steel from which steel wool is made is called low-carbon steel and contains between 0.1 and 0.3 percent carbon by mass.
An alloy like steel wool is a mixture of metals that results when two or more metals are melted and combined. Steel wool has a density of 7.84 g/cm3 and an average molecular weight of 55.7 g/mole. It is manufactured by shaving thin strips from steel wire and is sold by grade, or the thickness of each wool fiber.