Production of stainless steel of AISI 4xx grade ferritic steel in an AOD converter
AssigneeSMS Siemag Aktiengesellschaft
InventorJohann Reichel
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Abstract
For the production of stainless steel of the ferritic AISI 4xx group of steels, particularly the AISI 430 group of steels, based on liquid pig iron and FeCr solids, the invention proposes the use of the AOD (Argon Oxygen Decarburization) process in which oxygen and inert gas (inactive gas) together are blown into the bath through nozzles and top-blown onto the surface of the bath by a blowing lance. The aim of the treatment is to conclude a smelting charge within an optimal time period, to achieve the intended tapping temperature and composition, and to minimize chromium losses. This is achieved by a correspondingly applied technology and by means of a metallurgic process model which observes, prognosticates and controls the treatment of the smelting charge.
Claims8
Method of production of stainless steel of ferritic AISI 4xx group of steels, particularly the AISI 430 group of steels, based on liquid pig iron and FeCr solids, wherein a liquid slag-free pig iron, after preliminary treatment in a blast furnace (1) and DDD-treatment, is heated, refined or alloyed, reduced in a ADD-converter and, finally, adaptation/adjustment of a treated molten steel in a casting ladle (5) is carried out,
- characterized in that
- the DDD-treatment of the pit iron is carried out at extremely low temperatures of about 1150° C.,
- in AOD-converter (4) the following method steps heating, refining/alloying, and reduction of the liquid pig iron are carried out by side nozzles and top blowing lance,
- after heating and subsequent deslagging, for refining of the molten metal, oxygen is blown onto the molten metal by the top blowing lance, and a mixture of oxygen and inert gas (argon or nitrogen) is blown into the molten metal through side nozzles, wherein a ratio between the oxygen and the inert gas, starting with an oxygen-rich mixture, varies during the blowing process, and a total quantity of oxygen is constantly divided during a blowing process between the top blowing lance and the side nozzles.
Dependencies are inferred from the claim text.