Aluminum in Steels

Aluminum in Steels  Aluminum (Al) is used for deoxidizing and grain refining in steels. It is a strong deoxidizer. It is also used as nitride former and as an alloying agent. Its ability to scavenge nitrogen (N) from steel makes it a useful addition in drawing quality steels, especially for automotive applications. Aluminum (Al) is being used as a deoxidizing element in steels for more than 100 years. Deoxidation of steel with Al is common practice today. Al plays an important role in secondary metallurgy. It forms aluminum oxide or alumina (Al2O3) alumina and decreases the amount of oxygen in the steel during the production of killed steels. Metallic Al is the most common addition agent. It is usually done in the form of notched bars, shots, pigs, small ingots, chopped wire, briquettes and other convenient forms such as coiled machine fed wire. Purity of deoxidation grade of Al is normally over 95 % with the main tramp elements being zinc, tin, copper, magnesium, lead and manganese. Coiled aluminum wire is usually made to 99 % minimum specification. A wire feeding machine is shown in Fig 1. Fig 1 Wire feeding machine Al is also added as ferro-aluminum which is a dense and highly efficient form of aluminum addition. Ferro-aluminum contains 30 % to 40 % Al and normally added in lump form. Al may be added to the steel making furnace, teeming ladle, Ladle furnace, continuous casting tundish or ingot mould. Each type of addition has its specific purpose, and each addition produces its own characteristic results. Al is a very powerful deoxidizer, but has a disadvantage because of its low density. The density of liquid aluminum at steelmaking temperatures (1600 deg C) is about 2.0 tons/cum while the density of steel at...