AOD slag composition

The VODC process involves decarburisation under reduced pressure. It is much less used than the AOD process. Vacuum processes (EAF/vacuum) accounted for 5.8 % of the Western World s stainless steel production in 1991, The technique consumes 1 Nm Ar per tonne of steel, shows low chromium oxidation and has a silicon consumption of 3 - 5 kg/tonne. The VODC allows the production of ultra-low-carbon and nitrogen grades. [202, TWG, 2002] 

For deoxidation, aluminium is commonly used in the form of a stick. Additions vary from 0.1% for medium carbon steel to 0.2 % for low carbon steel. Recovery is between 35 % and 80 %. Mechanical feeding of aluminiiun wire is also used. [174, Brown, 2000]. 

The efficiency, the qualitative assessment of flue-gas production and the complexity of the various nodularisation methods are compared in Table 3.20. 

Comment Easy operation Optimised sandwich but more maintenance High mainte- nance High mainte- nance Expensive installation Different design of pouring system High mainte- nance 

The use of a pure starting material and mainly electric and gas-fired heating, results in relatively low emission levels from the melting. Due to the limited concern about off-gas quality, information on the flue-gas composition is limited. 

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