Argon oxygen decarburization: Difference between revisions

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Revision as of 14:56, 4 June 2019

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{{Refimprove|date=November 2010}}

[[File:AOD (Argon, oxygen decarburisation) vessel.jpg|thumb|Refining of a 9.5%CrMoWVNbN steel in an argon, oxygen decarburisation (AOD) vessel]]

'''Argon oxygen decarburization''' ('''AOD''') is a process primarily used in [[stainless steel]] [[steel making|making]] and other high grade alloys with oxidizable elements such as [[chromium]] and [[aluminum]]. After initial melting the metal is then transferred to an AOD vessel where it will be subjected to three steps of refining; [[decarburization]], [[Reduction (chemistry)|reduction]], and [[desulphurizationdesulfurization]]. AOD was invented in 1954 by the Lindé Division of The Union Carbide Corporation <ref>{{cite journal | doi = 10.1007/BF02667991| bibcode = 1973MT......4.1439K| title = The linde argon-oxygen process for stainless steel; A case study of major innovation in a basic industry| journal = Metallurgical Transactions|year=1973| volume = 4| issue = 6| pages =1439–1447 1439|author last1 = Krivsky,| first1 = W. A.|url year =https://link.springer.com/article/10.1007%2FBF02667991 1973| doi=<!-broken-date broken= 2019-06-> 04}}</ref> (which became known as [[Praxair]] in 1992).<ref>[http://www.unioncarbide.com/History History]. Unioncarbide.com (1917-11-01). Retrieved on 2013-12-28.</ref>

==Process==

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After a desired carbon and temperature level have been reached the process moves to reduction. Reduction recovers the oxidized elements such as chromium from the slag. To achieve this, alloy additions are made with elements that have a higher affinity for oxygen than chromium, using either a silicon alloy or aluminum. The reduction mix also includes lime (CaO) and fluorspar (CaF₂). The addition of lime and fluorspar help with driving the reduction of Cr₂O₃ and managing the slag, keeping the slag fluid and volume small.

=== DesulphurizationDesulfurization ===

DesulphurizationDesulfurization is achieved by having a high lime concentration in the slag and a low oxygen activity in the metal bath.

:S_(bath) + CaO_(slag) → CaS_(slag) + O_(bath)