AOD Furnace Refractories
AOD is the abbreviation of argon oxygen decarburization. Currently, AOD method is popularly used in stainless steel production all over the world, it is estimated 75% of stainless steel is produced by AOD furnaces. AOD method is blowing oxygen and argon mixture to steel liquid from furnace bottom, so CO gas will have very low partial pressure, vacuum degassing equipment is not required. At relatively low temperature, Cr won’t be oxidized, so carbon can de removed to very low level, meanwhile, refractory material high temperature damage can be avoided.
AOD Method Advantages
Can process steel liquid with high carbon content.
Cr recycling rate is high.
Low price high carbon ferrochrome can be processed.
Desulfurization treatment can be carried out.
Vacuum equipment is not needed, facilities investment is low, operation is convenient, economic benefit is significant.
AOD Furnace Refractory Materials
AOD furnace refractories are magnesia chrome bricks, magnesia dolomite bricks, dolomite bricks, refractory concrete and
ramming mix. Magnesia chrome bricks contain large percent of periclase spinel phase, tissue structure is stable and dense, therefore, MgO-Cr2O3 bricks have resistance to acidic slag corrosion and basic slag corrosion, and the application effect in AOD furnace is good. Dolomite bricks feature in excellent acid and alkaline slag corrosion resistance, good thermal shock resistance, won’t be reduced by reductant, low price and abundant resource, so dolomite bricks applications is wide. In low alkalinity slag, SiO2 can react with CaO in dolomite bricks and produce high melting point dicalcium silicate, which agglomerates at the surface of dolomite bricks and form protection layer. Besides, dolomite bricks also have good high temperature plasticity, thermal stress can be cushioned, lining cracking or spalling can be reduced.
In Japan,
magnesite chrome bricks are applied in AOD furnace earlier. Currently, magnesia dolomite bricks are universally used and have a better effect. Different grades of magnesia bricks can be used to mason synthesized furnace lining, sometimes, high temperature sintered direct bonded or semi rebonded magnesia bricks are applied at easy damage area.
American AOD furnace linings mainly adopt magnesia chrome bricks. Severe corrosion area mainly adopts direct bonded bricks, rebonded bricks and low porosity bricks, rest parts working lining mainly adopt direct bonded magnesia chrome bricks or dolomite bricks, containing 60% and 40% MgO, respectively. Permanent lining usually adopts ordinary burned magnesia chrome bricks, furnace body and furnace crown connection part and gas nozzle bricks side part usually adopt high alumina ramming mass, or magnesia chrome ramming mix, or refractory plastics.
In some countries, tar impregnated burned dolomite bricks and direct bonded dolomite bricks are used to line easy-damage parts, rest parts are lined by tar boned dolomite bricks or burned dolomite bricks. Unburned dolomite bricks are also used in AOD furnaces.
