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. Effects of temperature and oxygen concentration on the. The chemical composition of steel m0 is approximately fe0. Argon oxygen decarburization aod converter is popularly used in the stainless steel making process. Oxidation and decarburization kinetics of iron carbon alloys in carbon dioxide carbon monoxide atmospheres by gary john billings, b. In the argon oxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. Due to the reduced co partial pressure under vacuum conditions, decarburisation of highalloyed steel grades to very low carbon contents is possible. Chemistry a thesis submitted to the faculty of graduate studies in partial fulfilment of the requirements for the degree master of science mcmaster university hamilton, ontario, canada.
Carbon will therefore be removed from the steel by the process commonly known as decarburization. Decarburization article about decarburization by the free. Argonoxygen decarburization aod engineering dictionary. Argon oxygen decarburization, frequently referred to as aod, is an advanced technology for the refinement of iron, nickel, and cobalt based alloys. Gas supply modes include pipeline, bulk deliveries, cylinders, and onsite production units operated by air liquide. A parabolic relationship was assumed between the decarburization rate and the carbon content c. 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. Using the extrel max300ig process mass spectrometer to. A comparison study on depth of decarburization and the role. More accurately, the chemical potential of carbon in the atmosphere may be lower than that in the steel being heat treated. A quantitative analysis method of fluorine in the slags produced in the stainless argon oxygen decarburization aod process by x.
Effects of temperature and oxygen concentration on the characteristics of decarburization of 55sicr spring steel yangbo liu 1. At high temperatures, the oxygen atoms in mill scale are itching to. Argon oxygen decarburization aod harbisonwalker international. It was inevitable that these furnaces contained oxygen and decarburization of the steel surface occurred. Simulation of oxygen penetration and decarburisation in. Apr 07, 2020 classically, decarburization occurs when steel is heated in an environment where oxygen is present, leading to oxidation and loss of carbon. May 08, 2017 today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair. Lower oxygen concentration results in decrease in a growth rate of the oxide scale and leads to different characteristics of decarburization. Numerical simulation of decarburization in a topblown. Optimization of the ao stainless steel processing cost by the. Oxygen is allowed to flow over the surface of the molten bath causing the oxidation of carbon which. Basic oxygen steelmaking is the process of refining hot metal obtained from blast.
Modeling of the vacuum oxygen decarburization refining. Improving low carbon steel production in specialty steel processes. Chemical analysis of argonoxygen decarburization slags in. 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. Subsequently, the liquid passes to the converter, within which the steel undergoes the refining chemical analysis through redox reactions. Control of decarburization of steel paul shefsiek introduction historically, heating steel for forming, forging or rolling, was done in electrical resistance or natural gas heated furnaces. Argon oxygen decarburization aod is a unique refinement process for iron, nickel, and cobalt alloys whereby huge quality and efficiency gains can be made. The new source performance standards nsps for steel plants. 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. Several parameters come into play deciding the outcome of the process. Argon oxygen decarburization furnace steel slag aod. Investigation on different melting parameters effect on.
Contributing factors are high temperatures and large amounts of oxygen in the atmosphere. Decarburization is not only dependent on the presence of oxygen but also the interaction with other oxidizing gases in the atmosphere, most notably water vapor and carbon dioxide. Decarburization is a classic surface degradation phenomenon in the forging and heat treating of steel. Argon oxygen decarburization aod treatment is the recognized standard for stainless steel refining worldwide. Argon oxygen decarburization for metal production praxair, inc. 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. Aod production argon oxygen decarburization in this process the merger is implemented in conventional furnace. The removal of carbon removes hard carbide phases resulting in a softening of the metal, primarily at the surfaces which are in contact with the decarburizing gas. Modeling of gas flows in steelmaking decarburization processes. May 06, 2016 decarburization is not only dependent on the presence of oxygen but also the interaction with other oxidizing gases in the atmosphere, most notably water vapor and carbon dioxide. Simulation of oxygen penetration and decarburisation in eaf using supersonic injection system francesco memoli, carlo mapelli, 1 pietro ravanelli 2 and marco corbella. The length of the blow period is determined by the starting carbon and silicon levels decarburizatoin the hot metal charged to the aod argonoxyge.
Modeling of the vacuum oxygen decarburization refining process article pdf available in metallurgical and materials transactions b 311. Pdf simulation of fluid flow and oscillation of the. 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. Why the amount of carbon in stainless steel must be lower than that in carbon steel or lower alloy steel i. During heat treatment of metals, decarburization happens as a side effect, which is undesirable. Influence of decarburization on the fatigue behaviour of shot. Argon oxygen decarburization aod air liquide supplies industrial gases and related equipment and services to steel manufacturers for argon oxygen decarburization aod. At higher temperatures, the diffusion rate of carbon is so large that longer annealing times lead to decarburization. Optimization of the ao stainless steel processing cost by the ut as system chay tauar 800521t290 the argon oxygen decarburization aod process is one of the major stainless steel refining routes.
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. Obtained 1045, and steel placed in furnace at 1700 deg. Decarburization basics arburization occurs when cardec bon atoms at the steel surface interact with the furnace atmosphere and are removed from the steel as a gaseous phase18. In this study different parameters such as initial analysis of melt, weight of melt, temperature of melt before delivery to vacuum vessel and oxygen gas blowing rate were employed. The argonoxygen decarburization aod process is the most common process for refining stainless. Classically, decarburization occurs when steel is heated in an environment where oxygen is present, leading to oxidation and loss of carbon. Argon oxygen decarburization aod what a process for further refinement of stainless steel through reduction of carbon content. The decarburization step is controlled by ratios of oxygen to argon or nitrogen to remove the carbon from the metal bath. The molten metal is then decarburized and refined in a special aod vessel to less than 0. Decarburization may be described as a metallurgical process in which the surface of steel is depleted of carbon, by heating above the lower critical temperature or by chemical action. Oxidation and decarburization kinetics of ironcarbon alloys. Jul 10, 2017 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. Decarburization may be eliminated by heating in furnaces with a protective atmosphere or under vacuum. Simulation of oxygen penetration and decarburisation in eaf.
The invention relates to a fixture of a vod vacuum oxygen decarburization oxygen lance nozzle. Overall this means that oxygen flow can be controlled, so contaminating carbon can be released as carbon monoxide and carbon dioxide. A dynamic model for the vacuum oxygen decarburization vod refining process is presented. Kinetics of decarburization reaction in oxygen steelmaking.
A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Review on cfd simulation and modeling of decarburization. It is inevitable that the furnace atmosphere contains oxygen. In this process the tuyeres are submerged, resulting in high element recovery, rapid and efficient desulfurization, and good control of the slag chemistry. Mill scale forms on the steel surface which is basically solid iron oxide. After initial melting the metal is then transferred to an aod vessel where it will be subjected to three steps of refining. Astm e107714, standard test methods for estimating the depth of decarburization of steel specimens, astm international, west conshohocken, pa, 2014. Electric arc furnaces and argonoxygen decarburization vessels in. Modeling of the vacuum oxygen decarburization refining process. Download fulltext pdf simulation of fluid flow and oscillation of the argon oxygen decarburization aod process article pdf available in metallurgical and materials transactions b 412. Argon oxygen decarburization furnace steel slag aod youtube. A new method is used to calculate the oxygen distribution in the metalgas 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. It brings the tightest chemistry control to deliver the highest levels of metal purity.
As a result of decarburization, the metal loses some of its strength and ductility, and it may develop cracks which make it vulnerable to breaking. Learn more about praxairs argon oxygen decarburization process that is used to make over 75% of the worlds stainless steel. Aod argon oxygen decarburization soudobeam has developed a range of oxygen and inert gas topblowing products in stainless steelmaking, for aod argon oxygen decarburization converters. Decarburization occurs when metals are subjected to high temperatures, and the carbon present on the surface reacts with oxygen or hydrogen and diffuses. Vacuum oxygen decarburization vod of stainless steel optimization of the process with mechanical vacuum pumps anke teeuwsen 1 introduction 2 process overview decarburization decarburization of stainless steels under vacuum comprises two steps. Modeling of gas flows in steelmaking decarburization. Our soudoxar lance heads are equipped with laminar flow technology and are the fruit of advanced design and highquality production, to improve. By using only eaf for the production of stainless steel the following difficulties were arise.
Rhamdhani swinburne university of technology, hawthorn, vic 3122 australia key words. Surface escape of carbon atoms a hotworking during a hotworking operation, such as hotrolling, exposure to oxygen in the air is unavoidable. 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. The effect of flow rate of oxygen on decarburization rate, decarburization time, and total oxygen consumption was determined. Decarburization is a surface degradation phenomenon in the forging and heat treating of steels. Vacuum oxygen decarburization process modeling vod is a proven method for converting low quality, high carbon, scrap and iron into marketable, high quality steel. Decarburization occurs when the metal is heated to temperatures of 700 c or above when carbon in the metal reacts with gases containing oxygen or hydrogen. Argon oxygen decarburization aod is a process used in stainless steel making. Astm e1077 14 standard test methods for estimating the. 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 argon oxygen decarburization process total materia article. A mathematical model for reactions during topblowing in. In the production of stainless steel and other highalloy grades that contain highly oxidizable elements such as chromium, lowering the levels of carbon by regular oxygen injection has the undesirable consequence of oxidizing the alloying elements as well. 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 in open furnaces is minimized by reducing the residence time of metal at high temperatures for example, in walkingbeam furnaces or by using rapid electrical contact heating of the metal. This process takes place when carbon existing in metals reacts with gases containing hydrogen or oxygen during heating at 700c. Other articles where vacuum oxygen decarburization is discussed. The plant is basically designed as a tank degassing plant which is additionally equipped with an oxygen blowing lance and other related equipment.
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. What is vacuum oxygen decarburization process answers. Carbon from the interior diffuses towards the surface, moving from high to low concentration and continues until the maximum depth of decarburization is established. Needs very high temperatures about 19000 c for decarburization requiring high cost refractories. Argon oxygen decarburization aod is a process primarily used in stainless steel making and. Aod has a top lance for oxygen injection and several. It is normally used for deep decarburization of ighalloy steel grades usually to remove carbon without affecting chromium content in the production of. Decarburization is a loss of carbon in the surfaceadjacent zone of the material gunnarson, 1963. The material studied was a quenched and tempered carbon steel 0. This program has measured the decarburization of 300m alloy steel, as a function of temperature and oxygen concentration, and evaluated the results by way of models based on diffusion of carbon and on the effects of oxidation. Today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair. Pdf modeling of the vacuum oxygen decarburization refining. This introduction causes significant agitation and, therefore, intimate slagmetal contact.
The fixture comprises a base, a first upper cover, a baffle and a second upper cover, wherein the base is formed by welding steel plates. The vod is often used to lower the carbon content of highalloy steels without also overoxidizing such oxidizable alloying elements as chromium. Modeling of decarburization in metal droplet in basic oxygen steelmaking. Aod provides an economical way to produce stainless steel with a. 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. A comparison study on depth of decarburization and the. Electric arc furnaces eafs and argonoxygen decarburization. Blowing argon and oxygen, using sheets, maintain a continuous mixing. Decarburization normally takes place when steel goes through the heating process in an environment where oxygen is present, resulting in loss of carbon and oxidation. Vacuum oxygen decarburization metallurgy britannica. Mathematical modeling of the argonoxygen decarburization.
The reaction between carbon and the atmospheric gases usually begins around 700c 1292f. Modeling of decarburization in metal droplet in basic oxygen. Vacuum oxygen decarburization vod of stainless steel. Therefore, it is valuable to study not only the effect of temperature on depth of decarburization, but also the affect that stable carbide forming and additional alloying elements have on the decarburization response of a particular alloy. More specifically, two delaval nozzles from a vod vaccum oxygen decarburization process, which is used for producing stainless steels with ultralow carbon grades, was investigated for different vessel pressures. It also means that once the contaminants are converted, the oxygen flow can be halted to allow for increased gas removal from liquid steel via a. This research investigated the separate quantification of calcium fluoride and calcium oxide contained in aod slags. In the aod process, steel from the eaf is transferred into an aod vessel and gaseous mixtures containing argon and oxygen or. 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. Simulation of oxygen penetration and decarburisation in eaf using supersonic injection system francesco memoli, carlo mapelli,1 pietro ravanelli2 and marco corbella techint s. What is called argon oxygen decarburization aod process. Mathematical model the fast decarburization rates in the bof are due to the large surface area available for the chemical reactions.