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) Treatment is the recognized standard for stainless steel refining worldwide. Whether you are producing castings, wrought . Argon Oxygen Decarburization, frequently referred to as “AOD”, is an advanced technology for the refinement of iron, nickel, and cobalt based alloys. By.
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Converters that tap into a ladle car usually have a BOF type concentric cone top section. Most of the recent argon-oxygej installations include the use of a top lance for blowing oxygen. Dolomitic refractories are usually less costly than magnesite chromite refractories and chromium pickup is not a factor.
Since the AOD vessel isn’t externally heated, the blowing stages are also used for temperature control.
Argon Oxygen Decarburization for Metal Production | Praxair, Inc.
It has a removable, conical cover in place. The next step is the reduction step, in which the reduction additions are charged and stirred with an inert gas for a desired time.
To achieve this, alloy additions argon-pxygen made with elements that have a higher affinity for oxygen than chromium, using either a silicon alloy or aluminum.
Another modification of the AOD process involves applying vacuum on the decarbuirzation to reduce the consumption of argon and silicon as well as the process time when making low carbon grades. The transfer of sulphur to slag takes place as per the following reaction. Views Read Edit View history.
Argon oxygen decarburization – Wikipedia
The top lance can also be designed for blowing mixed gases such as inert gas — oxygen mixtures. November Learn how and when to remove this template message.
Leave a Reply Cancel reply Your email address will not be published. Low hydrogen Short circuit. If the grade to be produced requires an extra low secarburization level, the bath is deslagged after the reduction step and another basic slag is added. This argon dilution of oxygen minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium.
The decarburization step is controlled by ratios of oxygen to argon or nitrogen to remove the carbon from the metal bath.
The choice of refractory is dependent on the vessel operation pattern, final product specifications, and economics.
Want to modernize and upgrade the functionality of your old AOD system cost-effectively? Since the blowing is done along with argon it is possible to carry out the decarburization at a lower temperature. So, additions of lime are added to dilute sulfur in the metal bath.
Also, aluminum or silicon arggon-oxygen be added to remove oxygen. High wear areas of the converter, usually the tuyere wall, slag line, and transfer pad are zoned thicker and with dearburization quality refractory than other parts of the converter. The molten metal is then decarburized and refined in an AOD converter to less than 0. The installation of a lance and introduction of oxygen argon-oxyge the early stages of decarburization can reduce the time for a heat. The process is so popular because it combines higher metallic yields with lower material costs.
AOD provides an economical way to produce argon-oxygeb steel with a minimal loss of precious argon-oxyven.
After initial melting the metal is then transferred to an AOD vessel where it will be subjected to three steps of refining; decarburizationreductionand desulphurization. The intimate gas — metal contact and excellent slag — metal mixing facilitate refining reactions. Any chromium oxide not reduced by carbon ends up in the slag, which can form a complex spinel. If necessary, additional raw materials may be charged for small chemistry adjustments before tapping. 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. Usually, the converter is turned down to a horizontal position and a sample of the liquid steel is taken for analyses at a carbon level of about 0.
The tapped bath is then either sent to a stir station for further chemistry trimming or to a caster for casting. In deecarburization of those steel grades which can tolerate nitrogen, a mixture of oxygen and nitrogen decarburizatiob also be blown.
Would like to more details of how to increase vessel life and to reduce refractory wear near tuyers. Other trimming alloy additions might be added at the end of the step.
Desulphurization is achieved by having a high lime concentration in the slag and a low oxygen activity in the metal bath. This argon dilution minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium.
Magnesite chromite bricks are simultaneously acidic and basic and strict slag compositions must be maintained to prevent rapid wear. Your email address will not be published. After the change from nitrogen to argon, nitrogen is decarburizatuon from the bath both by evolved carbon monoxide and argon.
The important feature of an AOD converter is that it is normally side blown. The formation of a high basicity slag and the reduction of oxygen potential in the metal bath are good conditions for sulfur removal.
Additional silicon addition is needed if requirement of silicon is there to meet the silicon specification of some of the stainless steels. The decarburization reactions are as follow. Annealing Low argon–oxygen Short circuit. Decarburization occurs when dissolved carbon reduces the chromium and iron oxides that form. This page was last edited on 4 Octoberdeecarburization Bloomery produces sponge iron Blast furnace produces pig iron Cold blast Hot blast Anthracite iron Direct reduced iron.