What is vacuum oxygen decarburization process answers. The development and the application of vacuum oxygen decarburization vod model which is written in ms excel spreadsheet is described. 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. Decarburization article about decarburization by the free. The plant requires an efficient vacuum pump system to meet the specific requirements of the. It is based on a stepwise comparison of the reaction free energies, and it. 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. 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. At higher temperatures, the diffusion rate of carbon is so large that longer annealing times lead to decarburization.
Modeling of the vacuum oxygen decarburization refining process. Vd and vdob tank degassers, vod vacuum oxygen decarburization units. This introduction causes significant agitation and, therefore, intimate slagmetal contact. Preventing decarburization in steel requires metallurgists and their customers to pay attention to the details. The continuous oxygen injection during the decarburization phase was then reproduced by stepwise thermodynamic calculations, increasing the amount of added o2 by 100 kg in each step.
Improving low carbon steel production in specialty steel processes. Investigation on different melting parameters effect on. Practical model to simulate and to operate vacuum oxygen decarburization vod plant for stainless steelmaking conference paper pdf available may 2012 with 1,077 reads how we measure reads. Due to the reduced co partial pressure under vacuum conditions, decarburisation of highalloyed steel grades to very low carbon contents is possible. 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. Vod production vacuum oxygen decarburization the melting of scrap practiced for vod is the same as aod. As a result, a great number of very small bubbles form in a vacuum chamber. During the primary steelmaking process, gases like oxygen o2, hydrogen h2 and nitrogen n2 dissolve in the liquid steel. 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. In sms mevacs chs treatment is slag free under inert gas atmosphere inside a refractorycoated bell immersed into the bath.
Pdf practical model to simulate and to operate vacuum oxygen. Reliable vacuum is key to the success of the iter project. May 08, 2017 today, over 75% of the worlds stainless steel is made using the argon oxygen decarburization aod process invented by praxair. 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 comparison study on depth of decarburization and the. This unit is normally used for the deep decarburization of highalloyed steel grades, usually to remove carbon without. 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.
A wide variety of vacuum oxygen decarburization furnace options are available to you. Mitigation of explosion risk in vacuum degassing plants. Figure 1 shows a typical vod stainless steel production furnace. The erosion of this zone amounted to 20 mm per heat.
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. To accelerate decarburization, a significant hydrogen volume is injected in a metal during circulation degassing up to 4 m3min in 15 min, i. Modern development tendencies of ladle vacuum treatment. Why the amount of carbon in stainless steel must be lower than that in carbon steel or lower alloy steel i. Us6190435b1 method of vacuum decarburizationrefining of. This study was done in eico to investigate effect of initial condition on results of vacuum oxygen decarburization vod process to produce low carbon steel. Aod provides an economical way to produce stainless steel with a. Manual of continuous casting, metallurgical industry. The aod process argon, oxygen, decarburization is the first production process for stainless steel. 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. 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. 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. Measuring and preventing decarburization in steel paulo. A dynamic model for the vacuum oxygen decarburization vod refining process is.
Due to higher productivity and lower cost, the aod is primarily used for stainless steel production. Vod extensive decarburiation is acievable with a vacuum oxygen decarburization vod unit. Liu 16 investigated the decarburization behaviors of ultralowcarbon steel. Ladle service under the conditions of vacuumoxygen. Aug 29, 2017 one such risk is decarburization, which can weaken steel parts and put them at greater risk of failure during their service. Metallurgical functions alloy addition under oxygen free conditions. Mar 19, 1974 united states patent 3798025 abstract. The second decarburization phase under low vacuum is timed with the final nitrogen content in mind. From this point of view, the paper presents an experimental work of decarburization of molten iron with oxygen in air under reduced pressure. Decarburization control during stainless steel making in an eaf.
Desphosphorization in ironmaking and oxygen steel making page 4 of 42 nomenclature symbolabbreviation significance aod argon oxygen decarburization ass aircooled steel slag bf blast furnace bof basic oxygen furnace bos basic oxygen steelmaking casob composition adjustment by sealed argon bubbling with oxygen blowing crk chromium converter. Argon oxygen decarburization furnace steel slag aod. Decarburization control during stainless steel making in. Because of the limited oxygen concentration it is possible that the condensed dust particles are not fully oxidised and, therefore, retain. Us6468467b1 method and apparatus for vacuum decarburization. A new method is used to calculate the oxygen distribution in the metalgas reactions. The use of metallurgical modeling, offgas analysis, and offgas flow control, have been used to find results for the vacuum oxygen decarburization vod process for stainless steel production and. 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. Vacuum pump system provides the required pressure for degassingdecarburization purposes. The izhstal plant has created a technology for treating corrosionresistant steel by the method of vod in a 30ton ladle. This process permits the production of high chromium steels and alloys in a technically and commercially advantageous way extremely low carbon contents together with high chromium recovery, with minimal consumption. Reactions involving oxygen in the presence of oxygen, steel will oxidize.
It was inevitable that these furnaces contained oxygen and decarburization of the steel surface occurred. Using oxygen blowing simultaneously with vacuum treatment gives ability getting special lowcarbon steel electric steel, stainless steel, automobilebody sheet with ability of deep extract, etc. 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. Vacuum degassing processes for liquid steel ispatguru. High costs for vacuum generation and maintenance can be overcome by replacing steam ejector pumps with mechanical vacuum pumps, initially for the vacuum degassing vd process but later also for the vacuum oxygen decarburization vod process. It is based on a stepwise comparison of the reaction free. Decarburization may be eliminated by heating in furnaces with a protective atmosphere or under vacuum. Due to the pervasive nature of vacuum in the iter machine, there are very few iter systems which will not have. The converter metallurgy includes melt refinement in argon oxygen decarburization aod vessels and vacuum oxygen decarburization vodc in a converter vessel. The charge is melted in an arc furnace and the molten metal with around 0.
The vod is often used to lower the carbon content of highalloy steels without also overoxidizing such oxidizable alloying elements as chromium. Oxidation of liquid steel components under vacuum differs from that at normal pressure. The research of lowoxygen control and oxygen behavior. 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. Vacuum oxygen decarburization vod method is used for manufacturing stainless steels. The aluminothermal process ensures extra high heating rates. Factsage database a free energy data file for the used set of elements and their corresponding phases were generated. The effect of the process parameters and lining patterns on the endurance of the ladle was studied in development of the process. Prepared by technical team summary vacuum degassing vd and vacuum oxygen decarburisation vod are the main processes in secondary steel making. The vod vacuum oxygen decarburisation process is used for production of high chromium steels with lowest carbon contents. Step 2either argon oxygen decarburization aod vacuum oxygen. Step 3either electroslag remelting esr, electroflux remelting efr or vacuum arc remelting var. The invention relates to a fixture of a vod vacuum oxygen decarburization oxygen lance nozzle. Desphosphorization in ironmaking and oxygen steelmaking.
A comparison study on depth of decarburization and the role. The investigation was performed in the range of 16231723k from 0. D this process is mainly used for making stainless steel only of 304l, 316l grade to achieve extra low carbon content in stainless steel. A method for vacuum decarburization refining of a molten steel includes providing a vacuum tank having a onelegged, straight barrel snorkel as a lower portion of the vacuum tank. Pdf modeling of the vacuum oxygen decarburization refining. Dry mechanical vacuum pumps in use for vod and vdob. 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. 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. Mathematical model for decarburization process in rh. Mechanical vacuum systems for secondary metallurgy steel degassing bicom 12751. The process injects oxygen and inert gas argon or nitrogen. Decarburization control during stainless steel making in an eaf thomas echterhof1, victor yuardi risonarta1,3.
A characteristic of high vacuum is that the functionally of a whole system can be lost by not appreciating and paying attention to the effect of small details. In a controlled trial, 7 samples were decarburized and results measured for both low oxygen level atmospheres and air table 1. Step 2either argon oxygen decarburization aod, vacuum oxygen decarburization vod or vacuum degassing. Improving low carbon steel production in specialty steel. The argon oxygen decarburization aod unit is used for extensive decarburiation of the melt. The large volumes of dissolved contaminant gases arising and the generation of metallic fines and oxide dust require robust, high capacity pumping equipment.
Vod process extensive decarburization is achievable with a vacuum oxygen decarburization vod unit. Vodc vacuum oxygen decarburization converter process. The initial carbon content of the melt and the selected oxygen blow rate determine the duration of the refining treatment. This results in minimized gas pickup from ambient air and a high yield of alloy additions. These gases have a harmful effect on the mechanical and physical properties of 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. This tendency increases in severity as the temperature is raised. Mechanical vacuum systems for secondary metallurgy steel.
Decarburization is a loss of carbon in the surfaceadjacent zone of the material gunnarson, 1963. 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 vacuum. Overall this means that oxygen flow can be controlled, so contaminating carbon can be released as carbon monoxide and carbon dioxide. Prepared by technical team summary the need for advanced. Also, certain metallurgical reactions, for reasons of equipment design and. Vacuum oxygen decarburization vod vacuum oxygen decarburization vod is the manufacturing process by which the quality of stainless steel is assured. Vod abbreviation stands for vacuum oxygen decarburization. A dynamic model for the vacuum oxygen decarburization vod refining process is presented. Vacuum oxygen decarburization vod of stainless steel. Contributing factors are high temperatures and large amounts of oxygen in the atmosphere. 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. The carrying out of metallurgical reactions in the ladle is a common practice in practically all steelmaking shops, because it is costefficient to operate the primary furnace as a highspeed melter and to adjust the final chemical composition and.
Other articles where vacuum oxygen decarburization is discussed. The lining of the ladle is made of periclasechromite refractories produced by the magnezit works jsc. Compared to the previous decarburization strategy the oxygen consumption could be decreased by up to 24 % for single heats 8 minutes of injection time. 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. In a straight barrel type vacuum refining apparatus, use is made of a combination of.
Pressure required of 30200 mbar in case of oxygen blowing and around 1 mbar for degassingnatural decarburization processes three types of vacuum pumps steam ejectors dry mechanical pumps waterliquid ring pumps only for gross vacuum. The carrying out of metallurgical reactions in the ladle is a common practice in practically all steelmaking shops, because it is costefficient to operate the primary furnace as a highspeed melter and to adjust the final chemical composition and temperature of the steel after tapping. 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 process primarily used in stainless steel making and. The foregoing cycle is repeated while the pressure within the second vessel is progressively reduced and the oxygen introduced into the second vessel varied to decarburize the molten metal bath in steps without substantial oxidation of metal constituents therein. The plant is basically designed as a tank degassing plant which is additionally equipped with an oxygen blowing lance and other related equipment. This process takes place when carbon existing in metals reacts with gases containing hydrogen or oxygen during heating at 700c. Vacuum oxygen decarburization vod engineering dictionary.
After initial melting the metal is then transferred to an aod vessel where it will be subjected to three steps of refining. Vacuum oxygen decarburization vod what process for further refinement of stainless steel through reduction of carbon content. Pdf practical model to simulate and to operate vacuum. Innovations in refining process technique combined. 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. After 3 4 heats, through slots formed in the joints of the bricks as well as ovalshaped washouts through which the metal leaked between the functional and the intermediate layer. The blowing of oxygen under vacuum conditions offers a time and cost saving.
Product program for efficient secondary metallurgy. At last time combine equipment vdvod or vd vacuum degassing oxygen blowing gets important spread. Step 2either argon oxygen decarburization aod vacuum. Dec 05, 2017 by 1960, more efficient vacuum degassing methods such as the dortmund hoerder dh and ruhrstahlheraeus rh methods became popular. Vacuum oxygen decarburization metallurgy britannica. The ladle metallurgy includes vacuum induction degassing, vacuum oxygen decarburization, and vacuum ladle degassing.
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