Argon oxygen decarburization aod is a process primarily used in stainless steel making and other high grade alloys with oxidizable elements such as. The example of decarburization strategies are explained in table 2 and figure 2. Decarburization definition of decarburization by the free. Prevention of decarburization in annealing of high carbon. Argon oxygen decarburization aod converter slags are known to consist of both liquid and solid phases, but limited information on the slag characteristics has. This page was decarburisation edited on 4 octoberat during the final stage of blowing, the ratio of oxygen to argon is changed to 1. Electric arc furnaces and argonoxygen decarburization vessels constructed after august 17, 1983. More accurately, the chemical potential of carbon in the atmosphere may be lower than that in the steel being heat treated. Our applications engineers can help you determine the proper flow and pressure control needed for each gas to help you achieve consistent results and optimal tuyere life. Other articles where argonoxygen decarburization is discussed. Influence of decarburization on the fatigue behaviour of. The main targets of a bof converter are decarburisation.
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. Argon oxygen decarburization converter aod tuyer pipe. Decarburization is a loss of carbon in the surfaceadjacent zone of the material gunnarson, 1963. 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. Vodc vacuum oxygen decarburization converter process. 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. Pdf modeling of the vacuum oxygen decarburization refining. Professionals, at vaibh metallurgical solutions pvt.
In a controlled trial, 7 samples were decarburized and results measured for both low oxygenlevel atmospheres and air table 1. Mathematical modeling of the argonoxygen decarburization refining. A dynamic model for the vacuum oxygen decarburization vod refining process is presented. Referenced documents purchase separately the documents listed below are referenced within the subject standard but are not provided as part of the standard astm standards. This introduction causes significant agitation and, therefore, intimate slagmetal contact. Argonoxygen decarburisation air products offers a full line of industrial gases, including nitrogen and argon to assist with your argonoxygen decarburisation aod operations. In the argonoxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. 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 requirement on maximum depth of the decarburized layer is usually in the range 0.
If the decarburization is symmetrical this is an indication that the defect was present in billet or bloom prior to reheat and rolling. 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. Preventing decarburization in steel requires metallurgists and their customers to pay attention to the details. Heat treatment of tool steels for example, after heat treating, parts can be checked for hardness, tensile strength, and many other cracks, decarburization, and many other factors which might be affected by the treatment. Argon oxygen decarburization aod harbisonwalker international. Physical and mathematical modeling of the argonoxygen decarburization refining process of stainless steel. Pdf simulation of fluid flow and oscillation of the. Decarburization at the surface of a component corresponds to a layer of lower yield strength than the core material. E107714 standard test methods for estimating the depth of decarburization of steel specimens test specimens microindentation hardness test. Abstractthe process of deep decarburization of steel during argon or hydrogen argon mixture injection has been studied. Argonoxygen decarburization air products offers a full line of industrial gases, including nitrogen and argon to assist with your argonoxygen decarburization aod operations. Aug 29, 2017 one such risk is decarburization, which can weaken steel parts and put them at greater risk of failure during their service. A comparison study on depth of decarburization and the role.
Eaf slag electric arc furnace and aod slag argon oxygen decarburisation. Argon oxygen decarburization aod is a unique refinement process for iron, nickel, and cobalt alloys whereby huge quality and efficiency gains can be made. Electric arc furnaces and argonoxygen decarburization. Gibbs free energy for oxidation reaction of i element, jg. 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. It is inevitable that the furnace atmosphere contains oxygen. Optimization of the ao stainless steel processing cost by. The vod is often used to lower the carbon content of highalloy steels without also overoxidizing such oxidizable alloying elements as chromium. Innovations in refining process technique combined. 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 vod of stainless steel. Camgal silicates and camg oxides free cao and periclase with many. After initial melting the metal is then transferred to an aod vessel where it will be subjected to three steps of refining. High carbon steel products must frequently be annealed without decarburization.
Vacuum oxygen decarburization metallurgy britannica. E1077 01 standard test methods for estimating the depth of decarburization of steel specimens, carbon content, complete decarburization, decarburization, ferrite, microindentation hardness, partial decarburization, steels, total decarburization. E3 guide for preparation of metallographic specimens. 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. Effects of temperature and oxygen concentration on the. Both the gibbs free energy equation and the chemical. In total decarburization, the upper layer of the steel is composed primarily of ferrite materials, while in partial decarburization, a. A941 terminology relating to steel, stainless steel, related alloys, and ferroalloys.
A new method is used to calculate the oxygen distribution in the metalgas reactions. The functional layer is lined with bricks containing fused periclasechromite. 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. Measuring and preventing decarburization in steel paulo. In ambient air, the decarburization behavior can be divided roughly into five temperature ranges. Pdf the oscillation of argon oxygen decarburization aod converters is. 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. Effects of temperature and oxygen concentration on decarburization of 55sicr spring steel were investigated at the temperature range of 500c1200c by using a muffle furnace an atmosphere of ambient air and a simultaneous thermal analyzer low oxygen concentration with 2% o 2 and 98% n 2. Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the. In total decarburization, the upper layer of the steel is composed primarily of ferrite materials, while in partial decarburization, a mixture of materials may be present.
Influence of decarburization on the fatigue behaviour of shot. One possible implication of relying on slagdri interactions for decarburization is that if the reactions are not fast enough, the refining primarily decarburization may not proceed to meet the product specifications. The decarburization in an aod converter is made in a series of steps with distinct. 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. Physical and mathematical modeling of the argonoxygen. Metals free fulltext methods to determine characteristics of. Decarburization is a classic surface degradation phenomenon in the forging and heat treating of steel. Astm e1077 01 standard test methods for estimating the. An argon oxygen decarburization aod refining method for molten austenitic stainless steel.
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. Aod provides an economical way to produce stainless steel with a. Rita khanna, veena sahajwalla, in treatise on process metallurgy. Due to the reduced co partial pressure under vacuum conditions, decarburisation of highalloyed steel grades to very low carbon contents is possible. A comparison study on depth of decarburization and the. In the argon oxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel.
It was inevitable that these furnaces contained oxygen and decarburization of the steel surface occurred. Argon oxygen decarburization, frequently referred to as aod, is an advanced technology for the refinement of iron, nickel, and cobalt based alloys. Other articles where vacuum oxygen decarburization is discussed. The influence of oxygen flow rate, vacuum pressure, and argon flow rate on process. Decarburization and melting behavior of directreduced. Ladle service under the conditions of vacuumoxygen. Today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair. If decarburization is occurring, then a continuous surface layer of soft ferrite is being produced together with ferrite formation around austenite grains further away from the surface. 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. Apr 07, 2020 decarburization is a change in the structure and content of steel in which some of the carbon in the surface layer or layers of the steel is lost. Decarburization synonyms, decarburization antonyms. Electric arc furnaces and argonoxygen decarburization vessels in steel industry background information for proposed revisions to standards emission standards and engineering division u.
Theoretical models have been developed for an argonoxygen decarburization aod converter that also incorporated a thermodynamic description of the process 238. 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. Slag reduction it is inevitable that cr, together with some mn and fe are oxidized during oxygen blow. In complete decarburization, the top layer of steel consists mainly of ferrite materials, while partial decarburization presents a combination of materials. It is based on a stepwise comparison of the reaction free energies, and it allows the continuous. Decarburization is the change in content and structure of steel wherein some surface layers of steel and carbon are lost. Carbon will therefore be removed from the steel by the process commonly known as decarburization. Physicochemical and mineralogical properties of stainless steel. Microscopy is one of the techniques to determine carbon loss. Sulphur removal in ironmaking and oxygen steelmaking. 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. Astm e1077 14 standard test methods for estimating the.
The lining of the ladle consists o f three layers, i. Modeling of the vacuum oxygen decarburization refining process. Jun 01, 2018 decarburization is the change in content and structure of steel wherein some surface layers of steel and carbon are lost. 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. At annealing temperatures, co2 and h2o readily react with carbon in the steel to form co and h2. The argon oxygen decarburization process total materia article. The plant is basically designed as a tank degassing plant which is additionally equipped with an oxygen blowing lance and other related equipment. Limited, are having twenty five years of experience in producing stainless steel both in designing the. Pdf a dynamic model for the vacuum oxygen decarburization vod refining process is presented. Depending on temperature, the carbon in the steel can be present as cementite or as solute in the. Specifically, the oxygen used for decarburization as predicted by 2. 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 occurs if carbon atoms in the heated steel component have both a a mechanism for migrating and b a desire to migrate to the surface. Some available mathematical models for the argonoxygen decarburization aod stainless. The mathematical model proposed and presented in part i of the present work has been used to deal with and analyze the austenitic stainless steel making i. The chemical composition of steel m0 is approximately fe0. May 08, 2017 today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair. It is based on a stepwise comparison of the reaction free energies, and it allows the.
Boilingoff oxygen blowing is carried out only to the point where dissolved oxygen can be used to perform the final decarburization, typically from 0. Prevention of decarburization in annealing of high carbon steel. Argon oxygen decarburization aod treatment is the recognized standard for stainless steel refining worldwide. In a controlled trial, 7 samples were decarburized and results measured for both low oxygen level atmospheres and air table 1. Decarburization is a surface degradation phenomenon in the forging and heat treating of steels. 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. Pdf simulation of fluid flow and oscillation of the argon oxygen. 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. The production of corrosionresistant superlowcarbon steel in the izhstal plant is based on vacuumoxygen decarburization vod in a 30ton ladle 1. To avoid premature contact of oxygen with molten metal and ensure protection of the tuyere and the working chamber by the gas flow against. Modeling of gas flows in steelmaking decarburization. The production of corrosionresistant superlowcarbon steel in the izhstal plant is based on vacuum oxygen decarburization vod in a 30ton ladle 1.
The aod process argon, oxygen, decarburization is the first production process for stainless steel. The oxygen required for decarburization is supplied to the slag by addition of iron oxide as ore lump, pellet or mill scale. Our soudoxar lance heads are equipped with laminar flow technology and are the fruit of advanced design and highquality production, to improve. It was found that for crack free coatings, the drying temperature needs to be. Environmental protection agency office of air, noise, and radiation office of air quality planning and standards research triangle park, north carolina 27711. Desulphurization to very low levels is generally easier in dolomitic refractories because very basic slags can be used without detrimental effects on the bricks. You may do so in any reasonable manner, but not in. 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. Free surface was assumed to be flat and gas bubbles were allowed to leave the. Experimental heats show that the gasmixture injection into a melt is a very effective way to increase the degree and rate of decarburization. Theres even an industry standard astm e1077 dedicated to decarburization depth measurement. Optimization of the ao stainless steel processing cost by the. The list of acronyms and abbreviations related to aod argon oxygen decarburization.