Learn more about Praxair’s Argon Oxygen Decarburization process that is used to make over 75% of the world’s stainless steel. Argon Oxygen Decarburization (AOD) Treatment is the recognized standard for stainless steel refining worldwide. Whether you are producing castings, wrought . Argon Oxygen Decarburization, frequently referred to as “AOD”, is an advanced technology for the refinement of iron, nickel, and cobalt based alloys. By.
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The length of the blow period is determined by the starting carbon and silicon levels of the hot metal charged to the AOD converter. Praxair can review your system and design an upgrade using: These are achieved by having a high lime concentration in the slag and a low oxygen activity in the metal bath. Magnesite chromite bricks are simultaneously acidic and basic and strict slag compositions must be maintained to prevent rapid wear.
For example, with a start sulphur of 0. During decarburization, additions are made for obtaining the proper final chemical composition. Donate Grateful for your donation! The number and relative positioning of tuyeres is determined in part by converter size, range of heat sizes, process gas flow rates and types of alloys refined. Special designs exist for argon-oxyyen the flow in the annular gap. Send a question or comment. The system will be tailored to match your current operation with added features found only on the new systems.
Bloomery produces sponge iron Blast xecarburization produces pig iron Cold blast Hot blast Anthracite iron Direct reduced iron. The reduction mix also includes lime CaO and fluorspar CaF 2.
Leave a Reply Cancel reply Your email address will not be published. After a certain carbon level is achieved, the nitrogen gas is replaced by argon.
Modern instrumentation has been developed which can take melt samples as well as steel temperatures using a specially designed sub lance with the converter in the upright position. Ideally at this stage of the process, the chemistry of the liquid steel should meet the final specifications so that the heat can be tapped. This page was last edited on 4 Octoberat Also, aluminum or silicon may be added to remove oxygen. This is done in a ladle equipped with stirring facilities with or without the use of a ladle furnace.
Another modification of the AOD process involves applying vacuum on the converter to reduce the consumption of argon and silicon as well as the process time when making low carbon grades. After tapping, the ladle is often stirred for composition homogenization and temperature uniformity along with flotation of inclusions. It is part of a duplex process in which scrap or virgin raw materials are first melted in an electric arc furnace EAF or induction furnace.
The blow is continued to attain 0. The desire to increase the productivity has led to continuous charging of raw materials during the blow period as well as reduction period. This is due to the very low oxygen potential of the gas mixture, which minimizes chromium oxidation.
Your email address will not be published. Depending on final nitrogen specification for the stainless steel grade, argon-ixygen inert gas during the initial stages of decarburization can be nitrogen. Additional silicon addition is needed if requirement of silicon is there to meet the silicon specification of some of the stainless steels. To achieve this, alloy additions are made with elements that have a higher affinity for decarbugization than chromium, using either a silicon alloy or aluminum.
November Learn how and when to remove this template message. Bottom injection usually improves wear characteristics in the barrel section of the converter. During the oxygen blow, silicon is oxidized before carbon. The stages decarburizstion blowing remove carbon by the combination of dwcarburization and carbon forming CO gas. While typical BOF refractory campaigns are months or years long, stainless converter campaigns are several days or weeks long. Magnesite chromite refractories have high wear resistance but have a higher unit cost than dolomitic refractories.
Argon Oxygen Decarburization Process |
As molten stainless steels do not generate foam, and most stainless steel refining processes are side or bottom-blown, the dimensions of a stainless refining converter are smaller than a comparable BOF basic oxygen furnace converter.
An AOD converter is shown in Fig 1. The tapped bath is then either sent to a stir station for further chemistry trimming or to a caster for casting.
Low hydrogen Short circuit. Chromium pickup from the brick is possible.
Argon oxygen decarburization
In the initial stage, oxygen to argon in the ratio ranging from 5: Process gases are injected through submerged tuyeres that are installed in the side wall or bottom of the converter.
Bottom blown converters have a variety of tuyere configurations depending on flow rates required.
Please help decarburiation this article by adding citations to reliable sources. In general, the bath temperature is controlled to less than deg C. Cooling gases blown through the outer annulus shroud form a metal or oxide accretion called a mushroom at the tuyere tip. Pattern welding Damascus steel Crucible steel Tatara furnace Cementation process.