Molten steel holds dissolved oxygen that would cause gas porosity and inclusions on solidification. Aluminium reacts strongly with oxygen, so steel plants add it in the ladle or tundish to "kill" the steel, forming alumina that floats into the slag. Aluminium is supplied as notch bars, ingots, cubes, cones, shots, granules or cored wire. Its purity can vary by application, and some deoxidiser grades are made from scrap or dross recovery.
Why it matters when buying
- Specify Al purity % or metal content, form, weight per piece and size, since dissolution rate and recovery in the steel depend on them.
- Ask for a spectro report; elements such as zinc, copper or magnesium may be restricted for certain steels.
- Moisture and oxide coating reduce effectiveness and can be a safety risk; insist on dry, clean material.
- Consistency matters more than absolute purity for many plants, because dosing is calculated per heat.
Typical uses
Ladle deoxidation in induction furnace, electric arc furnace and integrated steel plants, and in some ferroalloy and foundry operations. Many grades are cut from primary or secondary ingot. See aluminium deoxidiser for steel plants and primary ingots.