The vod is often used to lower the carbon content of highalloy steels without also overoxidizing such oxidizable alloying elements as chromium. Modeling of gas flows in steelmaking decarburization processes. Invented in the late 1960s, praxair s proprietary argon oxygen decarburization aod process was first used exclusively for stainless steel production. 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. Theoretical models have been developed for an argon oxygen decarburization aod converter that also incorporated a thermodynamic description of the process 238. Metal refining with argon oxygen decarburization aod. Argon oxygen decarburization, frequently referred to as aod, is an advanced technology for the refinement of iron, nickel, and cobalt based alloys. 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. This argon dilution minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium. A decarburization process based on a stepwise decrease of the oxygen to inert ratio according to table 1 was gradually established. The argon oxygen decarburization aod process is one of the major stainless steel refining routes. A new method is used to calculate the oxygen distribution in the metalgas reactions.
Djustmentofchemicalcomposition aod the argon oxygen decarburization aod unit is used for extensive decarburiation of the melt. 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. Argon oxygen decarburization for metal production praxair. Argon oxygen decarburization aod is a unique refinement process for iron, nickel, and cobalt alloys whereby huge quality and efficiency gains can be made. Mathematical modeling of the argonoxygen decarburization. Pdf simulation of fluid flow and oscillation of the argon oxygen. Optimization of the ao stainless steel processing cost by the. Pdf the oscillation of argon oxygen decarburization aod converters is flow related and depends on the process parameters e. This introduction causes significant agitation and, therefore, intimate slagmetal contact. A dynamic model for the vacuum oxygen decarburization vod refining process is presented.
The term is typically used in metallurgy, describing the reduction of the content of carbon in metals usually steel. To avoid premature contact of oxygen with molten metal and ensure protection of the tuyere and the working chamber by the gas flow against. The actual situations of the aod process, including the competitive oxidation of the elements dissolved in the molten steel and the changes in the bath composition, as well as the nonisothermal nature of the process, have been analyzed. Decarburization occurs when the metal is heated to temperatures of 700 c or above when carbon in the. The oscillation of argon oxygen decarburization aod converters is flow related and depends on the process parameters e.
Argon oxygen decarburization argon oxygen decarburization aod is the most dominate process for the generation of stainless, lowalloy and superalloy steels. 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. Argon oxygen decarburization for metal production praxair, inc. Apr 06, 2020 argon oxygen decarburization aod treatment is the recognized standard for stainless steel refining worldwide. 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. Then the decarburization process based on a stepwise decrease of the oxygen with inert gas ratio strategies. 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. Mathematical modeling of the argonoxygen decarburization refining.
Aod provides an economical way to produce stainless steel with a. 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. Resco products has been and is involved in this application with its ability to supply both dolomitic as well as magnesite chrome refractory products. 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. Aod has a top lance for oxygen injection and several bottom tuyeres for blowing oxygen or inert gas during the operation. 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. Argon oxygen decarburization aod treatment is the recognized standard for stainless steel refining worldwide. No other process offers similar capabilities in the foundry.
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. 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. Argon oxygen decarburization furnace steel slag aod mineralproducts1. In the aod process, steel from the eaf is transferred into an aod vessel and gaseous mixtures containing argon and oxygen or. The latest advances made by the author with his research group have been summarized.
Blowing argon and oxygen, using sheets, maintain a continuous mixing. Mathematical modeling of the argon oxygen decarburization. Other articles where vacuum oxygen decarburization is discussed. Argon oxygen decarburization aod harbisonwalker international. Aod refining argon oxygen decarburization metaltek. Modeling of the vacuum oxygen decarburization refining process. A quantitative analysis method of fluorine in the slags produced in the stainless argonoxygen decarburization aod process by x. The argon oxygen decarburization process total materia. Aod production argon oxygen decarburization in this process the merger is implemented in conventional furnace. Today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair. Argon oxygen decarburization aod converter is popularly used in the stainless steel making process. Pdf simulation of fluid flow and oscillation of the argon.
This may contribute to the understanding of the mechanisms of the refining procedure in the argon. 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. In this process the tuyeres are submerged, resulting in high element recovery, rapid and efficient desulfurization, and good control of the slag chemistry. Vacuum oxygen decarburization metallurgy britannica. In the argonoxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. Modeling of gas flows in steelmaking decarburization. Carbon diffusion rates in ferrite and austenite are different, and are influenced by both temperature and composition.
Decarburization is a serious problem because surface properties are infe rior to core properties, resulting in poor wear resistance and low fatigue life. In the argon oxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. Prima pro process mass spectrometer improving low carbon steel production in specialty steel processes author. Two industrial vod nozzles were numerically studied and compared at different temperatures and ambient pressures. Argon oxygen decarburization furnace steel slag aod. 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. The aod process argon, oxygen, decarburization is the first production process for stainless steel grades in which the treatment time in a converter under. The new source performance standards nsps for steel plants. Aod process uses dilution technique for the decarburization of steel bath. Dec 05, 2017 by 1960, more efficient vacuum degassing methods such as the dortmund hoerder dh and ruhrstahlheraeus rh methods became popular. 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. Several parameters come into play deciding the outcome of the process.
This work led to the first commercial aod installation in joslyn, usa 1968 1. Aod has a top lance for oxygen injection and several. 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. Argon oxygen decarburization aod is used during the refining process to produce steel with low carbon. Argon oxygen decarburization aod is a process primarily used in stainless steel making and other high grade alloys with oxidizable elements such as. Learn more about praxairs argon oxygen decarburization process that is used to make over 75% of the worlds stainless steel. This research investigated the separate quantification of calcium fluoride and calcium oxide contained in aod slags. To limit oxidation, the water vapor concentration must be limited. Subsequently, the liquid passes to the converter, within which the steel undergoes the refining chemical analysis through redox reactions. 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. Chemical analysis of argonoxygen decarburization slags in.
Aug 31, 2019 argon oxygen decarburization aod treatment is the recognized standard for stainless steel refining worldwide. Argonoxygen decarburization aod magnesia chrome and. 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 aod vessel is a brick lined steel shell with provision for introduction of oxygen and inert gas argon. 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.
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. Water modeling was used to investigate the fluid flow and mixing characteristics in the bath of an 18 t aod vessel, as well as the backattack. Rita khanna, veena sahajwalla, in treatise on process metallurgy. Pdf simulation of fluid flow and oscillation of the. By 1960, more efficient vacuum degassing methods such as the dortmund hoerder dh and ruhrstahlheraeus rh methods became popular. Other articles where argonoxygen decarburization is discussed. The task focuses on studying an optimized processing in an aod converter using the uhts converter automation system utcas process control program. The argon oxygen decarburization process total materia article. Us5125934a argon recovery from argonoxygendecarburization. The decarburization in an aod converter is made in a series of steps with distinct. It brings the tightest chemistry control to deliver the highest levels of metal purity. 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 a process used to further refine the steel outside the eaf during the production of certain stainless and specialty steels.
After initial melting the metal is then transferred to an aod vessel where it will be subjected to three steps of refining. The example of decarburization strategies are explained in table 2 and figure 2. The injection of inert gas argon or nitrogen lowers the partial pressure. Decarburization or decarbonization is the process opposite to carburization, namely the reduction of carbon content. Aod, argon oxygen decarburization, refining provides tight chemistry control and high levels of metal purity for your application. 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. 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. This ingot refining process produces steel with low carbon properties. Argon oxygen decarburization converter aod tuyer pipe. Us5220797a argon recovery from argonoxygendecarburization. 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. Physical and mathematical modeling of the argonoxygen. Aod provides an economical way to produce stainless steel with a minimal loss of precious elements. Optimization of the ao stainless steel processing cost by.
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. Theoretical models have been developed for an argonoxygen decarburization aod converter that also incorporated a thermodynamic description of the process 238. 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. Aod production argonoxygendecarburization in this process the merger is implemented in conventional furnace.
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