Then the decarburization process based on a stepwise decrease of the oxygen with inert gas ratio strategies. Aod process uses dilution technique for the decarburization of steel bath. Several parameters come into play deciding the outcome of the process. Argon oxygen decarburization process argon oxygen decarburization aod is a process primarily used in production of stainless steel and other high grade alloys such as silicon steels, tool steels, nickelbase alloys and cobaltbase alloys with oxidizable elements such as chromium and aluminum. The aod vessel is a brick lined steel shell with provision for introduction of oxygen and inert gas argon. Pdf simulation of fluid flow and oscillation of the argon oxygen. Apr 06, 2020 argon oxygen decarburization aod treatment is the recognized standard for stainless steel refining worldwide. Dec 05, 2017 by 1960, more efficient vacuum degassing methods such as the dortmund hoerder dh and ruhrstahlheraeus rh methods became popular. Pdf the oscillation of argon oxygen decarburization aod converters is flow related and depends on the process parameters e. Argon oxygen decarburization process 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.
Learn more about praxairs argon oxygen decarburization process that is used to make over 75% of the worlds stainless steel. An aspect of the present disclosure may provide an argon oxygen decarburization aod refining method for molten austenitic stainless steel and, more particularly, to an argon oxygen decarburization aod refining method capable of reducing carbon and nitrogen in molten austenitic stainless steel in aod refinement. Physical and mathematical modeling of the argonoxygen. To avoid premature contact of oxygen with molten metal and ensure protection of the tuyere and the working chamber by the gas flow against. Two industrial vod nozzles were numerically studied and compared at different temperatures and ambient pressures. The key feature in the aod vessel is that oxygen for decarburization is mixed with argon or nitrogen inert gases and injected through submerged tuyeres. By 1960, more efficient vacuum degassing methods such as the dortmund hoerder dh and ruhrstahlheraeus rh methods became popular. Us5220797a argon recovery from argonoxygendecarburization. No other process offers similar capabilities in the foundry. Decarburization or decarbonization is the process opposite to carburization, namely the reduction of carbon content the term is typically used in metallurgy, describing the reduction of the content of carbon in metals usually steel. In the argon oxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. The aod vessel is a brick lined steel shell with provision for introduction of oxygen and inert gas argon or nitrogen below the surface of the molten metal. The liquid steel, which contains most of the chromium and nickel needed to meet the final procsss composition, is tapped at a temperature of to deg c from the eaf or.
Theoretical models have been developed for an argonoxygen decarburization aod converter that also incorporated a thermodynamic description of the process 238. This research investigated the separate quantification of calcium fluoride and calcium oxide contained in aod slags. Argon oxygen decarburization aod is a process primarily used in production of stainless steel and other high grade alloys such as silicon steels, tool steels, nickelbase alloys and cobaltbase alloys with oxidizable elements such as chromium and aluminum. Metal refining with argon oxygen decarburization aod. In this process the tuyeres are submerged, resulting in high element recovery, rapid and efficient desulfurization, and good control of the slag chemistry. A process usually carried out in a controlled furnace atmosphere so that surface oxidation is reduced to a minimum and the surface remains relatively bright. They were followed in the mid1960s by additional processes such as vacuum arc degassing, the aseaskf process, and the vacuum oxygen decarburization process for high chromium steels. It brings the tightest chemistry control to deliver the highest levels of metal purity. The argon oxygen decarburization process total materia. Blowing argon and oxygen, using sheets, maintain a continuous mixing.
Modeling of the vacuum oxygen decarburization refining process. Argon oxygen decarburization aod converter is popularly used in the stainless steel making process. The decarburization in an aod converter is made in a series of steps with distinct. Graham lewis, thermo fisher scientific, winsford, cheshire, united kingdom keywords low carbon steel stainless steel argon oxygen decarburization aod vacuum degassing vacuum oxygen decarburization vod. Rita khanna, veena sahajwalla, in treatise on process metallurgy. Mathematical modeling of the argon oxygen decarburization. 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.
Decarburization or decarbonization is the process opposite to carburization, namely the reduction of carbon content. Subsequently, the liquid passes to the converter, within which the steel undergoes the refining chemical analysis through redox reactions. Aod provides an economical way to produce stainless steel with a minimal loss of precious elements. Other articles where argonoxygen decarburization is discussed. This ingot refining process produces steel with low carbon properties. Modeling of gas flows in steelmaking decarburization. Aod, argon oxygen decarburization, refining provides tight chemistry control and high levels of metal purity for your application. Chemical analysis of argonoxygen decarburization slags in.
Pdf simulation of fluid flow and oscillation of the. Argon oxygen decarburization, frequently referred to as aod, is an advanced technology for the refinement of iron, nickel, and cobalt based alloys. The present invention is directed to a method for recovering argon from a feed mixture comprising argon, carbon monoxide, carbon dioxide, nitrogen, and hydrogen which comprises the steps of a purifying the feed mixture to remove contaminants, b compressing the purified feed mixture to a separation pressure, and c passing the compressed purified feed mixture through a pressure swing. Modeling of gas flows in steelmaking decarburization processes. Mathematical modeling of the argonoxygen decarburization refining. Electric arc furnaces and argon oxygen decarburization vessels were proposed on october 21, 1974, promulgated on september 23, 1975, and mostrecently amended on february 22, 2005. Aod has a top lance for oxygen injection and several bottom tuyeres for blowing oxygen or inert gas during the operation.
Argon oxygen decarburization aod is used during the refining process to produce steel with low carbon. The decarburization in an aod converter is made in a series of steps with distinct oxygen inert gas ratio, which is progressively decreased with increasing decarburization. Metal refining with argon oxygen decarburization aod refining systems allow precise gas manipulation to achieve the desired end result. By varying the ratio of oxygen and argon, it is possible to remove carbon to controlled levels by oxidizing it to carbon monoxide without also oxidizing and losing expensive. The argon oxygen decarburization process total materia article. The injection of inert gas argon or nitrogen lowers the partial pressure. In the aod process, steel from the eaf is transferred into an aod vessel and gaseous mixtures containing argon and oxygen or. It is part of a duplex process in which scrap or virgin raw. Invented in the late 1960s, praxair s proprietary argon oxygen decarburization aod process was first used exclusively for stainless steel production.
The argon oxygen decarburization aod process is used to make stainless steel and specialty grades of steel, including tool steels, silicon steels, lowalloy steels, and lowcarbon steels. Optimization of the ao stainless steel processing cost by the. Since stainless steels need to be further refined, oxygen, gradually replaced by argon, is blown through the molten steel to eliminate impurities. Argon oxygen decarburization aod is used during the refining process to produce steel with low carbon properties and low silicon levels, while creating a metal more weldable and more corrosion and heat resistant. Aod has a top lance for oxygen injection and several. By loading the furnace charge into the aod vessel the impurities in the charge can be significantly reduced and at the same time improvements can be made relating to the properties of the. The latest advances made by the author with his research group have been summarized. After initial melting the metal is then transferred to an aod vessel where it will be subjected to three steps of refining.
Aod production argonoxygendecarburization in this process the merger is implemented in conventional furnace. The argon oxygen decarburization aod process is one of the major stainless steel refining routes. Today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair. Aod provides an economical way to produce stainless steel with a. This argon dilution minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium. Prima pro process mass spectrometer improving low carbon steel production in specialty steel processes author. Decarburization occurs when the metal is heated to temperatures of 700 c or above when carbon in the. Argon oxygen decarburization converter aod tuyer pipe. Argon oxygen decarburization for metal production praxair, inc. Argon oxygen decarburization argon oxygen decarburization aod is the most dominate process for the generation of stainless, lowalloy and superalloy steels. Argon oxygen decarburization furnace steel slag aod mineralproducts1. Mathematical modeling of the argonoxygen decarburization.
In the aod process, steel from the eaf is transferred into an aod vessel and gaseous mixtures containing argon and oxygen or nitrogen are blown into the vessel to reduce the carbon. Invesitigation of air entrapment into an argon oxygen decarburization converter at the reduction stage yong tang timo fabritius and jouko harkki laboratory of process metallurgy, university of oulu, fin90014, finland abstract some argon oxygen decarburization aod converter workers found the nitrogen content in the low nitrogen. Kth optimization of the ao stainless steel processing cost by the ut as system chay tauar 800521t290 the argon oxygen decarburization aod process is one. Vacuum oxygen decarburization metallurgy britannica. A new method is used to calculate the oxygen distribution in the metalgas reactions. The new source performance standards nsps for steel plants. Aod refining argon oxygen decarburization metaltek. Aug 31, 2019 argon oxygen decarburization aod treatment is the recognized standard for stainless steel refining worldwide. Resco products has been and is involved in this application with its ability to supply both dolomitic as well as magnesite chrome refractory products. Djustmentofchemicalcomposition aod the argon oxygen decarburization aod unit is used for extensive decarburiation of the melt. In the argonoxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. A quantitative analysis method of fluorine in the slags produced in the stainless argonoxygen decarburization aod process by x. This work led to the first commercial aod installation in joslyn, usa 1968 1. Optimization of the ao stainless steel processing cost by.
The aod process argon, oxygen, decarburization is the first production process for stainless steel grades in which the treatment time in a converter under atmospheric conditions corresponds to the casting time of a slab caster for many steel grades. Theoretical models have been developed for an argon oxygen decarburization aod converter that also incorporated a thermodynamic description of the process 238. Argon oxygen decarburization aod is a process used to further refine the steel outside the eaf during the production of certain stainless and specialty steels. To limit oxidation, the water vapor concentration must be limited. Argon oxygen decarburization for metal production praxair. This introduction causes significant agitation and, therefore, intimate slagmetal contact. Argon oxygen decarburization aod harbisonwalker international. Decarburization is a serious problem because surface properties are infe rior to core properties, resulting in poor wear resistance and low fatigue life.
Argonoxygen decarburization aod magnesia chrome and. The aod process argon, oxygen, decarburization is the first production process for stainless steel grades in which the treatment time in a converter under. Through the management of an additional high oxygen partial pressure gas mix and argon, the metal is refined and can reduce carbon levels to 0. The vod is often used to lower the carbon content of highalloy steels without also overoxidizing such oxidizable alloying elements as chromium. Other articles where vacuum oxygen decarburization is discussed. Aod production argon oxygen decarburization in this process the merger is implemented in conventional furnace. The task focuses on studying an optimized processing in an aod converter using the uhts converter automation system utcas process control program. A dynamic model for the vacuum oxygen decarburization vod refining process is presented. The example of decarburization strategies are explained in table 2 and figure 2. The term is typically used in metallurgy, describing the reduction of the content of carbon in metals usually steel. Argon oxygen decarburization furnace steel slag aod.
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