Learn more about Praxair’s Argon Oxygen Decarburization process that is used to make over 75% of the world’s stainless steel. Argon oxygen decarburization (AOD) converter is popularly used in the stainless steel making process. AOD has a top lance for oxygen injection and several.
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These additions also serve to reduce the bath temperature as carbon and chromium oxidations are exothermic.
Argon Oxygen Decarburization Process |
The molten metal is then decarburized and refined in a special AOD vessel to rpocess than 0. When the vessel is rotated, the tuyeres are above the bath.
The intimate gas — metal contact and excellent slag — metal mixing facilitate refining reactions. Oxidation of carbon continues, but oxidation of chromium is limited.
Desulphurization to very low levels is generally easier in dolomitic refractories because very basic slags can be used without detrimental effects on the bricks. Bottom blown converters have a variety of tuyere configurations depending on flow rates required. It provides an economical way to produce stainless steel with a minimum loss of precious elements.
Another modification of the AOD process involves applying vacuum on the converter to reduce the consumption of argon and silicon as well as the process time when making low carbon grades. In case of those steel grades which can tolerate nitrogen, a mixture of oxygen and nitrogen can also be blown.
As molten stainless steels do not generate foam, and most stainless steel oxjgen processes are side or bottom-blown, the dimensions of a stainless refining converter are smaller than a comparable BOF basic oxygen furnace converter.
Other benefits include pinpoint accuracy in chemistry control down to 0. During argln, additions are made for obtaining the proper final chemical composition. The formation of a high basicity slag and the reduction of oxygen potential in the metal bath are good conditions for sulfur removal.
Argon oxygen decarburization – Wikiwand
There are two basic choices of refractory type, magnesite-chromite, and dolomite. Desulphurization is achieved by having a high lime concentration in the slag and a low oxygen activity in the metal bath. Refractory costs are a significant fraction of total operating costs.
Reduction recovers the oxidized elements such as chromium from the slag. Also, aluminum or silicon may be added to remove oxygen.
The process is so popular oxtgen it combines higher metallic yields with lower material costs. The decarburization step is controlled by ratios of oxygen to argon or nitrogen to remove the carbon from the metal bath. This accretion protects the tuyere and surrounding refractory. After sulphur levels have been achieved the slag is removed from the AOD vessel and the metal bath is ready for tapping.
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The tapped bath is then either sent to a stir station for further chemistry trimming or to a caster for casting. Additional silicon addition is needed if requirement of silicon is there to meet the silicon specification of some of the stainless steels.
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Argon oxygen decarburization
Tuyere size and number depend on specific process parameters. Careful manipulation of slag, as it precipitates in the reaction, is important. The liquid metal is transferred from transfer ladle to AOD converter. In the initial stage, oxygen to argon in the ratio ranging from 5: The next step is the reduction step, in which the reduction additions are charged and stirred with an inert gas for a desired time. The key feature in the AOD converter is that oxygen for decarburization is mixed with inert gas such as argon or nitrogen and injected through submerged tuyeres.
For example, with a start sulphur of 0.
Depending on final nitrogen specification for the stainless steel grade, the inert gas during the initial stages of decarburization can be nitrogen. The molten metal is then decarburized and refined in an AOD converter to less than 0.