Carbon will therefore be removed from the steel by the process commonly known as decarburization. Ladle service under the conditions of vacuum oxygen. A dynamic model for the vacuum oxygen decarburization vod refining process is presented. Needs very high temperatures about 19000 c for decarburization requiring high cost refractories. The lining of the ladle consists o f three layers, i.
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. Astm e1077 14 standard test methods for estimating the depth of decarburization of steel specimens. The vacuum oxygen decarburization vod process thermodynamic principle of the vod tank model laboratory trials. What is called argon oxygen decarburization aod process. 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 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. The vacuum degassing process, an essential step in the secondary metallurgy of steel, allows for a more precise removal of certain gaseous elements to successfully attain even the. Vacuum oxygen decarburization vod what process for further refinement of stainless steel through reduction of carbon content. A comparison study on depth of decarburization and the. A new method is used to calculate the oxygen distribution in the 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 lining of the ladle is made of periclasechromite refractories produced by the magnezit works jsc. A dynamic model for the vacuum oxygen decarburization vod refining process. Vod extensive decarburiation is acievable with a vacuum oxygen decarburization vod unit.
Modeling of gas flows in steelmaking decarburization. In a controlled trial, 7 samples were decarburized and results measured for both low oxygenlevel atmospheres and air table 1. 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. Vod abbreviation stands for vacuum 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. The vod is often used to lower the carbon content of highalloy steels without also overoxidizing such oxidizable alloying elements as chromium. The production of corrosionresistant superlowcarbon steel in the izhstal plant is based on vacuum oxygen decarburization vod in a 30ton ladle 1. The investigation was performed in the range of 16231723k from 0120 minutes. 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. Improving low carbon steel production in specialty steel processes. This process takes place when carbon existing in metals reacts with gases containing hydrogen or oxygen during heating at 700c. Pdf modeling of the vacuum oxygen decarburization refining. Obtained 1045, and steel placed in furnace at 1700 deg. Optimization of the ao stainless steel processing cost by. Decarburization occurs when metals are subjected to high temperatures, and the carbon present on the surface reacts with oxygen or hydrogen and diffuses. The izhstal plant has created a technology for treating corrosionresistant steel by the method of vod in a 30ton ladle. With the only variation of the liquid steel is poured into a ladle, entered into a plant tank capable of creating an initial 3 mbar vacuum and then stabilize in 0. We have a wide variety to offer in order to cater to the variegated needs of our customers.
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. Vodc vacuum oxygen decarburization converter process. It is based on a stepwise comparison of the reaction free energies, and it allows the continuous calculation. Other articles where vacuum oxygen decarburization is discussed. This can be achieved by using a vacuum such as the vod vacuum oxygen decarburization or by dilution of the oxygen with an inert gas such as ar as in the aod process 14. A method for cyclically decarburizing a bath of molten metal such as steel by transferring the molten metal from a first vessel to a second vessel, evacuating the space above the molten metal in the second vessel while subjecting the metal bath. 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. Decarburization is a surface degradation phenomenon in the forging and heat treating of steels. Smajor ingredient responsible for the corrosion resistance. Inside the vacuum chamber, an oxygen lance is blown on top of the melt while argon is bubbled up from the bottom. To be carried out accurately, the process depends on the ability to measure the composition of the stream of gas leaving the furnace throughout the process. Aod argon oxygen decarburization cfc carbon fibre composites dnb diagnostic neutral beam.
Vacuum oxygen decarburization vod engineering dictionary. Electric arc furnaces and argonoxygen decarburization vessels in steel industry background information for proposed revisions to standards emission standards and engineering division u. The characteristics and classification of decarburization and denitrogenation in the vacuum vessel for stainless steel production are analyzed. Pdf practical model to simulate and to operate vacuum oxygen. 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. Astm e1077 14 standard test methods for estimating the. Jun 01, 2018 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. Steel degassing plants mtag switzerlands main expertise consists of supplying solutions for vacuum degassing of liquid steel using mechanical dry pumping systems. Argon oxygen decarburization aod harbisonwalker international. Today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair.
It is inevitable that the furnace atmosphere contains oxygen. 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. 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 an aod, metal is subjected to three steps of refining. In this process the tuyeres are submerged, resulting in high element recovery, rapid and efficient desulfurization, and good control of the slag chemistry. Environmental protection agency office of air, noise, and radiation office of air quality planning and standards research triangle park, north carolina 27711. Electric arc furnaces and argonoxygen decarburization. Due to higher productivity and lower cost, the aod is primarily used for stainless steel production.
This introduction causes significant agitation and, therefore, intimate slagmetal contact. A comparison study on depth of decarburization and the role. Decarburization is a classic surface degradation phenomenon in the forging and heat treating of steel. In accordance to some recommendations, free board reserve during vodprocess must be even more up to 1. 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. Established in the year 1996, we, pooja machines manufacturing private limited have gained immense expertise in the process of manufacturing and supplying a wide range of best quality air pollution control system the offered range has been availed to the major client base as per their requirements. More accurately, the chemical potential of carbon in the atmosphere may be lower than that in the steel being heat treated. The effect of the process parameters and lining patterns on the endurance of the ladle was studied in development of the process. Aod provides an economical way to produce stainless steel with a. The influence of oxygen flow rate, vacuum pressure. A new method is used to calculate the oxygen distribution in the metalgas reactions. The plant is basically designed as a tank degassing plant which is additionally equipped with an oxygen blowing lance and other related equipment. This ingot refining process produces steel with low carbon properties. Due to the reduced co partial pressure under vacuum conditions, decarburisation of highalloyed steel grades to very low carbon contents is possible.
It was inevitable that these furnaces contained oxygen and decarburization of the steel surface occurred. From this point of view, the paper presents an experimental work of decarburization of molten iron with oxygen in air under reduced pressure. Several parameters come into play deciding the outcome of the. At higher temperatures, the diffusion rate of carbon is so large that longer annealing times lead to decarburization.
Decarburization article about decarburization by the. Our soudoxar lance heads are equipped with laminar flow technology and are the fruit of advanced design and highquality production, to improve. Innovations in refining process technique combined. Vacuum oxygen decarburization metallurgy britannica. Pdf the development and the application of vacuum oxygen decarburization vod model which is written in ms excel spreadsheet is described. Investigation on different melting parameters effect on vacuum. 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. 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. Kinetic model of decarburization and denitrogenation in. During heat treatment of metals, decarburization happens as a side effect, which is undesirable.
Ladle service under the conditions of vacuumoxygen. Vacuum treatment the vacuum oxygen decarburizer vod, which has an oxygen lance in the centre of the tank lid to enhance carbon removal under vacuum. The functional layer is lined with bricks containing fused periclasechromite. Why the amount of carbon in stainless steel must be lower than that in carbon steel or lower alloy steel i. Vod vacuum oxygen decarburization meltshop365 vod intelligent process automation for vod systems meltshop365 for vod plant ensures reproducible and documented quality and efficient and ergonomic use of resources through intelligent process automation. It is normally used for deep decarburization of ighalloy steel grades usually to remove carbon without. 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. The aod process argon, oxygen, decarburization is the first production process for stainless steel. 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. The processes can be combitype such as duplex or triplex ones.
Modeling of the vacuum oxygen decarburization refining. 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. Hardening of steel removal of carbon from the surface of iron carbon compounds done by heating materials to 40 50% of their melting temperature time and heat dependent reaction. May 08, 2017 today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair. There are various vessel stirring methods for making stainless steels aiming at usage of least cost charge materials, significant alloy. Aod, argon oxygen decarburization, refining provides tight chemistry control and high levels of metal purity for your application. What is the abbreviation for vacuum oxygen decarburization. After initial melting the metal is then transferred to an aod vessel where it will be subjected to three steps of refining. Aug 29, 2017 one such risk is decarburization, which can weaken steel parts and put them at greater risk of failure during their service. Vacuum oxygen decarburization vod vod, a manufacturing process that ensures the quality of stainless steel, relies heavily on fast and precise measurements of stream compositions during various stages of the process.
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. Aod refining argon oxygen decarburization metaltek. Optimization of the ao stainless steel processing cost by the. Based on the analysis of movements of the liquid steel and bubbles, the kinetics of decarburization and denitrogenation in the vacuum oxygen decarburization vod process has been studied. 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. Contributing factors are high temperatures and large amounts of oxygen in the atmosphere. The vacuumoxygen decarburization process is used in the making of stainless steels. Vod production vacuumoxygendecarburization the melting of scrap practiced for vod is the same as aod. While, commercial grade of stainless steel is preferred in aod process, high quality steel with low carbon, low oxygen, low nitrogen is produced with vod process. By using only eaf for the production of stainless steel the following difficulties were arise. Blowing oxygen into molten steel under vacuum conditions. Argon oxygen decarburization aod is a process primarily used in steelmaking foundries and other highgrade alloys with oxidizable elements such as chrome and aluminum. Vod vacuum arc decarburization vqc vacuum classification system.
Mar 19, 1974 vacuum decarburization in rh and dh type degassing systems. The calculated final metal composition and temperature are in reasonable agreement with the production data. Modeling of gas flows in steelmaking decarburization processes. Decarburization is a loss of carbon in the surfaceadjacent zone of the material gunnarson, 1963. Several parameters come into play deciding the outcome of the process. Desulfurizing slag treatments can be added after the degassing. Decarburization may be eliminated by heating in furnaces with a protective atmosphere or under vacuum. Preventing decarburization in steel requires metallurgists and their customers to pay attention to the details. Carbon from the interior diffuses towards the surface, moving from high to low concentration and continues until the maximum depth of decarburization is established. The vacuum oxygen decarburization vod process can be used to produce. Modeling of the vacuum oxygen decarburization refining process. Pdf practical model to simulate and to operate vacuum. Decarburization article about decarburization by the free. Vacuum oxygen decarburization vod vacuum oxygen decarburization vod is the manufacturing process by which the quality of stainless steel is assured.
Decarburization in open furnaces is minimized by reducing the residence time of metal at high temperatures for example, in walkingbeam furnaces or by. 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. 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. Measuring and preventing decarburization in steel paulo. The reaction between carbon and the atmospheric gases usually begins around 700c 1292f. Vacuum degasser, vacuum oxygen decarburization vdvod the ladle is put into the vacuum tank to stir the melting steel in the vacuum to conduct degasification of hydrogen, and nitrogen decarbonization, and removal of nonmetal enclosures.
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