Argon Oxygen Decarburization (AOD) Treatment is the recognized standard for stainless steel refining worldwide. Whether you are producing castings, wrought . Argon-oxygen decarburization: stainless steel: In the argon-oxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. 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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Special designs exist for normalizing the flow in the annular gap. For more Praxair videos, please visit our YouTube channel. Desulphurization is achieved by having a high lime concentration in the slag and a low oxygen activity in the metal bath.
The intimate gas — metal contact and excellent slag — metal mixing facilitate refining reactions. 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.
The converter in the trunnion ring typically can be replaced with a preheated converter in less than an hour. Careful manipulation of slag, as it precipitates in the reaction, is important. The formation of high basic slag and the reduction of oxygen potential in the liquid steel bath are good conditions for sulphur removal. Cooling gases blown through the outer annulus shroud form a metal or oxide accretion called a mushroom at the tuyere tip.
An AOD converter is shown in Fig 1.
Argon oxygen decarburization for metal production
The end result is a cleaner metal coupled with increased productivity. While typical BOF refractory campaigns are months aryon years long, stainless converter campaigns are several days or weeks long. Typical internal volumes of AOD converters are in the range 0. AOD provides an economical way to produce stainless steel with a minimal loss of precious elements.
Smelting Bloomery oxyggen sponge iron Blast furnace produces pig iron Cold blast Hot blast Anthracite iron Direct reduced iron. Since the blowing is done along with argon it is possible to carry out the decarburization at a lower temperature.
The blow is continued to attain 0. Converters are typically zoned by thickness and brick quality to maximize lining life and minimize costs. In case of those steel grades which can tolerate nitrogen, a mixture of oxygen and nitrogen can also be blown.
Your email address will decarburisation be published. In the initial stage, oxygen to argon in the ratio ranging from 5: The liquid steel and the fluxes are then mixed to complete the desulfurization reaction. The decarburization reactions are as follow. It has a removable, conical cover in place. So, additions of lime are added to dilute sulfur in the metal bath.
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. Praxair can quote a server-only option for these systems.
When the vessel is rotated, the tuyeres are above the bath. The molten metal is then decarburized and refined in a special AOD argom to less than 0. As molten stainless steels do not generate foam, and most argoon steel refining processes are side or bottom-blown, the dimensions of a stainless refining converter are smaller than a comparable BOF basic oxygen dfcarburization converter.
Posted by Satyendra on Apr 28, in Technical 1 comment. The molten metal is then decarburized and refined in an AOD converter to less than 0.
Metal Refining with Argon Oxygen Decarburization (AOD) Refining Systems – Inductotherm Corp.
For example, with starting sulphur of 0. After tapping, the ladle is often stirred for composition homogenization and temperature uniformity along with flotation of inclusions.
The top lance can also be designed for blowing mixed gases such as inert gas — oxygen mixtures. Depending on final nitrogen specification for the stainless steel grade, the inert gas during the initial stages of decarburization can be nitrogen.
The next step is the reduction step, in which the reduction additions are charged and stirred with an inert gas for a desired time. For example, with a start sulphur of 0.
Oxidation of carbon continues, but oxidation of chromium is limited. After initial melting the metal is then transferred to an AOD vessel where it will be subjected to three steps of refining; decarburizationreductionand desulphurization.
High temperatures at the tuyere tip and high bath agitation place great demands on the converters refractory. Argon oxygen decarburization AOD is a process primarily used in stainless steel making and other high grade alloys with oxidizable elements such as chromium and aluminum.
Leave a Reply Cancel reply Your email address will not be published. Other trimming alloy additions might be added at the end of the step. The AOD converter has tuyeres mounted in the sidewall or in the bottom. If necessary, additional raw materials may be charged for small chemistry adjustments before tapping. Nitrogen control is a gas — metal reaction.
Chromium pickup from the brick is possible. The decarburization step is controlled by ratios of oxygen argpn argon or nitrogen to remove the carbon from the metal bath.
After sulphur levels have been achieved the slag is removed from the AOD vessel and the metal bath is ready for tapping. The important feature of an AOD converter is that it is normally side blown.