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Argon-oxygen decarburisation

After its invention in the 1950’s and subsequent commercialisation in the late 1960’s, the AOD process has become the most common unit process for refining of stainless steel. A key feature of this process is that the blowing mixture is diluted with inert (argon) or partially inert (nitrogen) gases in order to reduce oxidation of chromium and other alloying elements. Modern vessels are equipped with both tuyères and a top lance for gas injection.

The AOD process can be divided into three main stages. The combined-blowing decarburisation stage constitutes the first part of decarburisation. The combined-blowing decarburisation stage is followed by the side-blowing decarburisation stage, which is continued until the target carbon content is obtained. The final stage of the process is the reduction stage, during which oxidised alloying elements are reduced back to the steel bath by to addition of reductants (typically ferrosilicon or aluminium) and simultaneous argon stirring.



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