Structure of AOD furnace and working principle of argon-oxygen decarburization refining method

In 1991, 75.6% of the world's total stainless steel production was produced by the AOD process (8 million tons of stainless steel). The proportion of AOD refining technology is increasing at home and abroad. Ladle nozzle seat brick

AOD furnace type is similar to LD converter, from the offset type to the easy bricklaying straight mouth development. The support trunnion of the furnace body can be tilted at any Angle. The AOD furnace is housed in a rotating support shaft ring connected to the tilting shaft, and the vessel can be rotated 180° forward and 80° backward with variable speeds.

AOD equipment is mainly composed of furnace body, supporting ring, tilting mechanism, gas mixed charging system, temperature measurement and sampling system. The AOD furnace is lined with magnesia chromium and other refractory materials, and the lower part is designed as a cone with a 20° inclination Angle. The purpose is to make the gas sent into the furnace wall and rise, to avoid the erosion of the top of the tuyere wall, the furnace at the bottom side of the two or more tuyere, in order to be ready to blow gas into the molten pool, when loading and steel, the furnace body tilt forward, the tuyere exposed to the ladle surface, the tuyere buried deep in the molten pool during normal blowing.

The amount of refining gas is gradually reduced with the process of decarbonization in operation, and only 0.5 is reached in the low carbon range. At the end of decarbonization, ferrosilicon alloy is added for argon stirring, chromium in slag is recovered, desulfurization is carried out if necessary, and steel is produced after adjusting the composition and temperature of molten steel. In the process of decompression and inert gas stirring, the gas content of steel is lower than that of arc steelmaking. From the shape of AOD furnace body determines that the amount of gas blown into the unit time per ton of molten steel is large, so the decarbonization speed is large, and the processing time is short, which is one of the characteristics of AOD method, and the equipment cost is low.

The basic principle of the AOD method is similar to decarbonization under vacuum, the latter is to use vacuum to reduce the carbon monoxide partial pressure of the decarbonized product, and the AOD method is to use gas dilution method to reduce the carbon monoxide partial pressure, without the need for equipment expensive vacuum facilities. When smelting stainless steel, for the crude molten steel containing both carbon and chromium, oxygen must be blown into the molten steel to oxidize the carbon without producing too much chromium. Then, mixed argon and oxygen are sent into the molten steel through the side-blowing oxygen gun, and carbon dioxide is diluted with argon to reduce its partial pressure, thus achieving the purpose of decarbonization and chromium preservation. Due to the blowing of high pressure argon-oxygen mixed gas, The contact chance between molten steel and bubbles and slag is increased, which is convenient for rapid decarbonization, and conducive to rapid desulfurization and degassing and non-metallic inclusions, which is the holding point of AOD furnace refining process.