ARGON OXYGEN DECARBURIZATION PROCESS PDF
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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Magnesite chromite refractories have high wear resistance but have a higher unit cost than dolomitic refractories. Lime and dolomitic lime are sometimes added before the end of the blow to cool the bath pprocess to reduce the volume of reduction additions.
Procesa can review your system and design an upgrade using: Additions of lime are made to dilute the sulphur in the liquid steel bath. Refractory costs are a significant fraction of total operating costs. Your email address will not be published.
Argon oxygen decarburization
Nitrogen control is a gas — metal reaction. Oxidation of carbon continues, but oxidation of chromium is limited.
AOD is widely used for the prodess of stainless steels and specialty alloys such as silicon steels, tool steels, nickel-base alloys and cobalt-base alloys. After sulfur levels have been achieved the slag is removed from the AOD vessel and the metal bath is ready for tapping.
Desulphurization is achieved by having a high lime concentration in the slag and a low oxygen activity in the metal bath. The addition of lime and fluorspar help with driving the reduction of Cr 2 O 3 and managing the slag, keeping the slag fluid and volume small. This argon dilution minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium. A major modification of the AOD process involves the use of top blowing lance in addition to the side blowing tuyeres.
The formation of a high basicity slag and the reduction of oxygen potential in the metal bath are good conditions for sulfur removal.
There are two basic choices of refractory type, magnesite-chromite, and dolomite. The number and relative positioning of tuyeres is determined in part by converter size, range of heat sizes, process gas flow rates and types of alloys refined. AOD provides an economical way to produce stainless steel with a minimal loss of precious elements. The next step is the reduction step, in which the reduction additions are charged and stirred with an inert gas for a desired time. There are usually between two and nine tuyeres in an AOD vessel.
Special designs exist for normalizing the flow in the annular gap. The process is so popular because it combines higher metallic yields with lower material costs. Other trimming alloy additions might be added at the end of the step.
To drive the reaction to the forming of CO, the partial pressure of CO is lowered using argon or nitrogen. If necessary, additional raw materials may be charged for small chemistry adjustments before tapping. Decarburization time ranges from 20 to 35 minutes in modern converters start from 1. Low hydrogen Short circuit. Since the blowing is done along with argon it is possible to carry out the decarburization at a lower temperature. Converters are typically zoned by thickness and brick quality to maximize lining life and minimize costs.
In other projects Wikimedia Commons. The proceds feature in the AOD converter is that oxygen for decarburization is mixed with inert gas such as argon or nitrogen and oxygem through submerged tuyeres. decarburrization
Other benefits of AOD process include pinpoint accuracy in chemistry control down to 0. Sulfur removal is a slag — metal reaction that occurs during the reduction phase of the process. The ratios can be done in any number of phases to facilitate the reaction.
In case of those steel decarburizatio which can tolerate nitrogen, a mixture of oxygen and nitrogen can also be blown. The system will be tailored to match your current operation with added features found only on the new systems.
November Learn how and when to remove this template message. Cooling gases blown through the outer annulus shroud form a metal or oxide accretion called a mushroom at the tuyere tip. If the grade to be process requires an extra low sulphur level, the bath is deslagged after the reduction step and another basic slag is added. The liquid metal is transferred from transfer ladle to AOD converter.
Argon oxygen decarburization – Wikipedia
Sidewall mounted tuyeres are submerged while processing. The length of the blow period is determined by the starting carbon and silicon levels of the hot metal charged to the AOD converter.
History of ferrous metallurgy List of steel producers. During the oxygen blow, silicon is oxidized before carbon. It is part of a duplex process in which scrap or virgin raw materials are first melted in an electric arc furnace EAF or induction furnace IF.
For more Praxair videos, please visit our YouTube channel. Side wall injection usually imparts maximum stirring energy to the bath for greatest efficiency of mixing. For example, with a start sulphur of 0. After initial melting the metal is then transferred to an AOD vessel where it will be subjected to three steps of refining; decarburizationreductionand desulphurization.
Tuyere size and number depend on specific process parameters. Converters that tap into a ladle car usually have a BOF type concentric cone top section. Designed by Elegant Themes Powered by WordPress.