AOD furnace is an out-of-furnace refining technology that uses a mixed gas of argon and oxygen to refine stainless steel.
AOD Furnace Process
The process is to pour the molten steel roughly refined in the electric furnace into the AOD, blow a certain proportion of argon-oxygen mixed gas into the furnace from the lower side wall of the furnace body, and decarburize on the surface of the O2-Ar bubble.
Due to the dilution effect of argon gas on the generated CO, the CO partial pressure in the O2-Ar bubble is reduced, which can promote decarburization and prevent chromium oxidation. At the same time, as the proportion of argon-oxygen mixed gas blown into the bottom of the furnace continues to increase, stainless steel can be refined under false vacuum conditions.
The AOD method has the following advantages when smelting stainless steel
Compared with the VOD method for smelting stainless steel, the AOD method requires less equipment investment, is easy to maintain, and is simple to operate; the process is easy to master, and ultra-low carbon stainless steel can be smoothly smelted using cheap raw materials such as scrap steel and high-carbon ferrochrome.
It can smelt ultra-low sulfur stainless steel, and the quality of the steel is comparable to that of molten steel treated by vacuum.
It can improve the total recovery rate of chromium, and the recovery rate of chromium can reach 98%, and it can be alloyed with nitrogen, and the production cost is low.
After the birth of this equipment, countries around the world rushed to introduce it. At present, about 80% of the world’s total stainless steel production is produced by AOD furnaces.
The AOD equipment is mainly composed of a furnace body, a support ring, a tilting mechanism, a gas mixing modulation and blowing system, and a temperature measurement and sampling system. The furnace includes a furnace body and a furnace cap.
The lower side wall of the furnace body is inclined at an angle of about 20° with the center line of the furnace body, which helps the blown gas rise along the side wall to the furnace mouth and reduce the serious erosion of the gas on the upper area of the air gun. The shape of the furnace cap is jaw, asymmetric and symmetrical, but the symmetrical type is currently more commonly used.
This not only improves the operator’s observation of the furnace, but also simplifies the furnace roof masonry process, changing the previous castable masonry to brick masonry.
An important technical advancement of the AOD furnace is the transplantation of the converter top oxygen blowing experience and the development of the top and bottom composite blowing method. The top and bottom composite blowing method is used in the early stage of AOD furnace smelting and decarburization, which can accelerate the decarburization and temperature rise of molten steel and shorten the smelting time.
