Argon Oxygen Decarburization (AOD) Treatment is the recognized standard for stainless steel refining worldwide. Whether you are producing castings, wrought . Argon-oxygen decarburization: stainless steel: In the argon-oxygen decarburization process, a mixture of oxygen and argon gas is injected into the liquid steel. 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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Volatile elements with high vapour pressures, such as lead, zinc, and bismuth, are removed during the decarburization period. After sulphur levels have been achieved the slag is removed from the AOD vessel and the metal bath is ready for tapping. Careful manipulation of slag, as it precipitates decarburiztion the reaction, is important. The stages of blowing remove carbon by the combination of oxygen and carbon forming CO gas. The decarburization reactions are as follow.

High temperatures at the tuyere tip and high bath agitation place great demands on the converters refractory. Low hydrogen Short circuit. So, additions of lime are added to dilute sulfur in the metal bath.

During decarburization, additions are made for obtaining the proper final chemical composition. The liquid metal is transferred from transfer ladle to AOD converter. Decarburization occurs when dissolved carbon reduces the chromium and iron oxides that form. The important feature of an AOD converter is that it is normally side blown.

AOD is widely used argoj the production of stainless steels and specialty alloys such as silicon steels, tool steels, nickel-base alloys and cobalt-base alloys.

The bath is then stirred with inert gas, typically for around five to eight minutes. Iron and steel production. Tuyere size and number depend on specific process parameters. Lime and dolomitic lime are sometimes added before the end of the blow to cool the bath and to reduce the volume of reduction additions. These are i decarburization, ii decarburizarion, and iii final chemistry and temperature secarburization.

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During the oxygen blow, silicon is oxidized before carbon. Phosphorus, which requires oxidizing conditions, cannot be removed in the converter processing. Bottom blown converters have a variety of tuyere configurations depending on flow rates required. In the early days of the AOD process, the converter was tilted for raw material additions as well as for taking samples and for measurement of temperature using immersion thermocouples.

Argon Oxygen Decarburization Process

The addition of lime and fluorspar help with driving the reduction of Cr 2 O 3 and managing the slag, keeping the slag fluid and volume small. Cooling gases blown through the outer annulus shroud form a metal or oxide accretion called a mushroom at the tuyere tip.

The key feature in the AOD converter is that oxygen for decarburization decarburizwtion mixed with inert gas such as argon or nitrogen and injected through submerged tuyeres. 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.

In general, the bath temperature is controlled to less than deg C. Decarburization time ranges from 20 to 35 minutes in modern converters start from 1.

Metal Refining with Argon Oxygen Decarburization (AOD) Refining Systems – Inductotherm Corp.

The formation of high basic slag and the reduction of oxygen potential in the liquid steel bath are good conditions for sulphur removal. After initial melting the metal is then transferred to an AOD vessel where it will be subjected to three steps of refining; decarburizationreductionand desulphurization. Praxair can review your system and design an upgrade using:.

The transfer of sulphur to slag takes place as per the following reaction. 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. For example, with starting sulphur of 0.

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Bottom injection usually improves wear characteristics in the barrel section of the converter. The molten metal is then decarburized and refined in a special AOD vessel to less than 0. Also, aluminum or silicon may be added to remove oxygen. The length of the blow period is determined by the starting carbon and silicon levels of the hot metal charged to the AOD converter.

Haynes International Case Study Video. Retrieved from ” https: When the vessel is rotated, the tuyeres are above the bath. Other benefits include pinpoint accuracy in chemistry control down to 0.

Argon-oxygen decarburization | metallurgy |

For example, with a start sulphur of 0. The gas control system supplies the process gases at nominal rates of 1. By using this site, you agree to the Terms of Use and Privacy Policy. The amount of stirring energy from the gas blown through the subsurface tuyeres and the formation of the carbon monoxide deep within the metal bath results in the converter processes being among the most intensely stirred metallurgical reactors.

It provides an economical way to produce stainless steel with a minimum loss of precious elements. The effectiveness of reduction step is dependent on many factors including slag basicity and composition, temperature, mixing conditions in the converter and solid addition dissolution kinetics. A major modification of the AOD process involves the use of top blowing lance in addition to the side blowing tuyeres.