Ferrous slag: a valuable raw material
for sustainable business
Ferrous slag is an industrial by-product generated during the production of hot metal and steel. For many decades, over 90 percent of the ferrous slag produced in Europe has been used in high-quality building materials and fertilisers, in other applications, and within the plants themselves. In doing so, it replaces natural resources, avoids CO2 emissions and thus makes an important contribution to resource conservation, the circular economy and climate protection.
What is ferrous slag?
Ferrous slag is as old as human iron production, which began over 4,000 years ago. However, it was not until the end of the 19th century that slag began to be used in large quantities for various purposes. Slag is a valuable metallurgical tool that is absolutely essential for the production of hot metal and steel. Without slag, there is no steel!
Ferrous slag is a largely homogeneous by-product consisting of calcium silicate compounds. With its main constituents – calcium, silicon, iron, aluminium and magnesium – each in typical mineral compounds, it resembles natural volcanic lava not only in its chemical composition but also in its mineralogy.
How is ferrous slag produced?
Depending on the production process, a distinction is made between blast furnace slag and steel furnace slag. Blast furnace slag is produced when iron ore and other technical additives are converted into hot metal. Depending on the cooling method, this results in
crystalline blast furnace slag, which cools slowly in the slag bed (air-cooled blast furnace slag – ABS) or
rapidly cooled, glassy blast furnace slag (granulated blast furnace slag – GBS)
Steel furnace slag is formed during the production of steel from hot metal, steel scrap and other materials. Depending on the processing method, a distinction is made between the following:
Basic oxygen furnace slag – BOF
Electric arc furnace slag from carbon steel production –
EAF C
Stainless steel slag from an electric arc furnace and downstream units – EAF S
Secondary metallurgical slag – SMS
Other slag, e.g. desulphurisation slag