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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In general, the bath temperature is controlled to less than deg C. The amount of stirring energy from the gas blown through the subsurface tuyeres and the formation of the carbon monoxide deep within the metal bath results in the converter processes being among the most intensely stirred metallurgical reactors.
If the grade to be produced requires an extra low sulphur level, the argo-noxygen is deslagged after the reduction step and another basic slag is added. Retrieved from ” https: After the change from nitrogen to argon, nitrogen is removed from the bath both by evolved carbon monoxide and argon.
The formation of a high basicity slag and the reduction of oxygen potential in decarburizagion metal bath are good conditions for sulfur removal. Since the AOD vessel isn’t externally heated, the blowing stages are also used for temperature control.
Most of the recent converter installations include the use of a top lance for blowing oxygen. Haynes International Case Study Video. In modern practices a sulphur level of 0. Annealing Low hydrogen Short circuit.
The bath is then stirred with inert gas, typically for around five to eight minutes. In the initial stage, oxygen to argon in the ratio ranging from 5: Special designs exist for normalizing the flow in the annular gap.
Want to modernize and upgrade the functionality of your old AOD system cost-effectively? Such an approach is usually practiced by steelmakers to reduce argon usage and costs and still achieve a desired nitrogen specification. During decarburization, additions are made for obtaining the proper final chemical composition.
For converters that tap into a ladle held by a crane, a sliced cone top section is often used.
For example, with a start sulphur of 0. The converter in the trunnion ring typically can be replaced with a preheated converter in less than an hour. The process zrgon-oxygen very popular because it combines higher metallic yields with lower material costs. To drive the reaction to the forming of CO, the partial pressure of CO is lowered using argon or nitrogen.
There are two basic choices of refractory type, magnesite-chromite, and dolomite. When the vessel is rotated, the tuyeres are above the bath. Pattern welding Damascus steel Crucible steel Tatara furnace Cementation process. The liquid metal is transferred from transfer ladle to AOD converter.
Argon Oxygen Decarburization for Metal Production | Praxair, Inc.
After a certain carbon level is achieved, the nitrogen gas is replaced by argon. After initial melting the metal is then transferred to an AOD vessel where it will be subjected to three steps of refining; decarburizationreductionand desulphurization. Would like to more details of how to increase vessel life and to reduce refractory wear near tuyers. The transfer of sulphur to slag takes place as per the following reaction.
Ideally at this stage of the process, the chemistry of the liquid steel should meet the final specifications so that the heat can be tapped. Converters that tap into a ladle car usually have a BOF type concentric cone top section.
Tuyere size and number depend on specific process parameters. Lime and dolomitic lime are sometimes added before the end of the blow to cool the bath and to reduce the volume of reduction additions. It provides an economical way to produce stainless steel with a minimum loss of precious elements.
Decarburization occurs on the surface of rising bubbles that form from either the inert gas that is injected or on the surface of chromium oxide particles that are being reduced and generating carbon mono oxide CO.
Posted by Satyendra on Apr 28, in Technical 1 comment. So, additions of lime are added to dilute sulfur in the metal bath. The top lance can also be designed for blowing mixed gases such as inert gas — oxygen mixtures.
These additions also serve to reduce the bath temperature as carbon and chromium oxidations are exothermic. The AOD converter can be rotated downwards so that the side mounted tuyeres are above the bath level during charging of the liquid steel. In the early days of the AOD process, the converter was tilted for raw material additions as well as for taking samples and for measurement of temperature using immersion thermocouples.
This is done in a ladle equipped with stirring facilities with or without the use of a ladle furnace. After a desired carbon and temperature level have been reached the process moves to reduction. For example, with starting sulphur of 0.
Argon Oxygen Decarburization Process
Other benefits include pinpoint accuracy in chemistry control down to 0. This argon dilution of oxygen minimizes decarburiztion oxidation of precious elements contained in specialty steels, such as chromium. Argon oxygen decarburization for metal production Share Print. The installation of a lance and introduction of oxygen in the early stages of decarburization can reduce the time for a heat. The slice portion allows the crane to come close to the converter decarburzation.
High temperatures at the tuyere tip and high bath agitation place great demands on the converters refractory.