The argon oxygen decarburization process total materia article. Argon oxygen decarburization aod converter is popularly used in the stainless steel making process. Argon oxygen decarburization furnace steel slag aod duration. Aod production argon oxygen decarburization in this process the merger is implemented in conventional furnace. This argon dilution of oxygen minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium. Aod has a top lance for oxygen injection and several. The key feature in the aod converter is that oxygen for decarburization is mixed with inert gas such as argon or nitrogen and injected through submerged tuyeres.
The argon oxygen decarburization aod process is one of the major stainless steel refining routes. In the initial stage, oxygen to argon in the ratio ranging from 5. Gibbs free energy for oxidation reaction of i element, jg. The ratio is lowered with the progress of the decarburization. Argon oxygen decarburization aod vacuum degassing vacuum oxygen decarburization vod ruhrstahl heraeus rh hit ratio variable pressure inlet introduction world crude steel production reached 1,691 million tonnes in 2017, up by 5. 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. In the aod process, steel from the eaf is transferred into an aod vessel and gaseous mixtures containing argon and oxygen or. 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. Argon oxygen decarburization aod is a process primarily used in stainless steel making and other high grade alloys with oxidizable elements such as chromium, aluminum, etc. Argon oxygen decarburization, frequently referred to as aod, is an advanced technology. Decarburization during heat treatment or during heating prior to rolling or forging extends into the.
The task focuses on studying an optimized processing in an aod converter using the uhts converter automation system utcasprocess control program. Pdf the oscillation of argon oxygen decarburization aod converters is flow related and depends on. Decarburization is a loss of carbon in the surfaceadjacent zone of the material gunnarson, 1963. Argon oxygen decarburization aod treatment is the recognized standard for stainless steel refining worldwide. A dynamic model for the vacuum oxygen decarburization vod refining process is presented. Decarburization of steel and alloys may produce both harmful and beneficial effects. Other articles where argonoxygen decarburization is discussed. Aod provides an economical way to produce stainless steel with a. Argon oxygen decarburization furnace steel slag aod. Process gases are injected through submerged tuyeres that are installed in the side wall or bottom of the converter. Pdf simulation of fluid flow and oscillation of the. Decarburization the reduction of the carbon concentration in steels and alloys that takes place upon heating in oxidizing media, as well as in hydrogen dry or wet. In the argonoxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. Argon oxygen decarburization aod is a process primarily used in stainless steel making and.
Pdf the major issue in stainless steelmaking is the difficulty of oxidising carbon from molten. Modeling of gas flows in steelmaking decarburization. Pdf simulation of fluid flow and oscillation of the argon oxygen. Since the blowing is done along with argon it is possible to carry out the decarburization at a lower temperature.
Subsequently, the liquid passes to the converter, within which the steel undergoes the refining chemical analysis through redox reactions. It is based on a stepwise comparison of the reaction free energies, and it allows the continuous calculation of the change of the metal, slag, and gas composition throughout the duration of the vod process. The new source performance standards nsps for steel plants. Argon oxygen decarburization furnace steel slag aod youtube. O emissions from each stationary fuel combustion unit. Djustmentofchemicalcomposition aod the argon oxygen decarburization aod unit is used for extensive decarburiation of the melt. No other process offers similar capabilities in the foundry. Then the decarburization process based on a stepwise decrease of the oxygen with inert gas ratio strategies. Desulphurization to very low levels is generally easier in dolomitic refractories because very basic slags can be used without detrimental effects on the bricks. Aod provides an economical way to produce stainless steel with a minimal loss of precious elements. Argon oxygen decarburization, frequently referred to as aod, is an advanced technology for the refinement of iron, nickel, and cobalt based alloys. It brings the tightest chemistry control to deliver the highest levels of metal purity. The oscillation of argon oxygen decarburization aod converters is flow related and depends on the process parameters e.
Method this work compares the stepwise decarburization practice according to table 1 with two alternative practices based on the theory as described above. After initial melting the metal is then transferred to an aod vessel where it will be subjected to three steps of refining. Contributing factors are high temperatures and large amounts of oxygen in the atmosphere. States are free under section 116 of the act to establish even more stringent emission limits than those established under section 111 or than. 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. By using only eaf for the production of stainless steel the following difficulties were arise. Argon oxygen decarburization aod continuous casting 4500ton forge press sx65 rotary forge sx32 rotary forge inline cogging mills ho tr o llin g wire rolling mills bar rolling mills custom lotmills handmills tocarpenter servicecenters directlyto customers millorders distributio n cold finishing largebar finishing bar finishing wire. Metal refining konverters aod electrotherm youtube. Mathematical modeling of the argonoxygen decarburization refining. The example of decarburization strategies are explained in table 2 and figure 2. 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. 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.
A new method is used to calculate the oxygen distribution in the metalgas reactions. Free ferrite layer depth ffd, when present and partial decarburization depth pdd, when free ferrite is understanding and measuring decarburization understanding the forces behind decarburization is the first step toward minimizing its detrimental effects. Some available mathematical models for the argonoxygen decarburization aod stainless. Optimization of the ao stainless steel processing cost by. Theoretical models have been developed for an argon oxygen decarburization aod converter that also incorporated a thermodynamic description of the process 238. Modeling of the vacuum oxygen decarburization refining.
Mathematical modeling of the argonoxygen decarburization refining process of. 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. 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. At higher temperatures, the diffusion rate of carbon is so large that longer annealing times lead to decarburization. Invented in the late 1960s, praxair s proprietary argon oxygen decarburization aod process was first used exclusively for stainless steel production. Argon oxygen decarburization wikipedia republished wiki 2. Argonoxygen decarburization aod what a process for further refinement of stainless steel through reduction of carbon content. In the aod process, steel from the eaf is transferred into an aod vessel and gaseous mixtures containing argon and. Decarburization article about decarburization by the. Two industrial vod nozzles were numerically studied and compared at different temperatures and ambient pressures. The decarburization in an aod converter is made in a series of steps with distinct oxygen.
Metal refining with argon oxygen decarburization aod. Blowing argon and oxygen, using sheets, maintain a continuous mixing. Pdf understanding stainless steelmaking through computational. 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. Metal refining with argon oxygen decarburization aod refining systems allow precise gas manipulation to achieve the desired end result. Modeling of the vacuum oxygen decarburization refining process. In this process the tuyeres are submerged, resulting in high element recovery, rapid and efficient desulfurization, and good control of the slag chemistry. An argon oxygen decarburization aod refining method for molten austenitic stainless steel includes, preparing molten austenitic stainless. The argon oxygen decarburization process total materia.
Decarburization synonyms, decarburization antonyms. Media in category aod converter the following 2 files are in this category, out of 2 total. Bottom pouring reduces surface and subsurface ingot defects. Why the amount of carbon in stainless steel must be lower than that in carbon steel or lower alloy steel i. 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. Electric arc furnaces and argonoxygen decarburization vessels in. Carpenters modern testing facilities help the melt shops produce alloys that meet stringent requirements for chemistry and purity. Today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair. Learn more about praxairs argon oxygen decarburization process that is used to make over 75% of the worlds stainless steel. Needs very high temperatures about 19000 c for decarburization requiring high cost refractories. Since stainless steels need to be further refined, oxygen, gradually replaced by argon, is blown through the molten steel to eliminate impurities. Rita khanna, veena sahajwalla, in treatise on process metallurgy. This introduction causes significant agitation and, therefore, intimate slagmetal contact.
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