what is slag

Slag is a by-product of smelting ores and recycled metals. It is mainly a mixture of metal oxides and silicon dioxide. Broadly, it can be classified as ferrous, ferroalloy, or non-ferrous/base metals. Slag has various applications, including its use in the manufacture of high-performance concretes, road materials, ballast, and as a source of available phosphate fertilizer. It is also used to create fibers for insulation materials called slag wool. In welding, slag is the stony waste separated from metals during the smelting or refining of ore. It is formed during welding from flux and is used in various welding processes to prevent defects caused by inclement weather and to ensure the quality of the weld.