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) converter is popularly used in the stainless steel making process. AOD has a top lance for oxygen injection and several.
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This is due to the very low oxygen potential of the gas mixture, which minimizes chromium oxidation. Decarburization time ranges from 20 to 35 minutes in modern converters start from 1.
Argon Oxygen Decarburization for Metal Production | Praxair, Inc.
This page was last edited on 4 Octoberat 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. Views Read Edit View history. After the ladle treatment, the steel is ready to be cast. Magnesite chromite bricks are simultaneously acidic and basic and strict slag compositions must be maintained to prevent rapid wear.
The tapped bath is then either sent to a stir station for further chemistry trimming or to a caster for casting.
Usually, the converter is turned down to a horizontal position and a sample of the liquid steel is taken for analyses at a carbon level of about 0. If the grade to be produced requires an extra low sulphur level, the bath is deslagged after the reduction step and another basic slag is added. The liquid metal is transferred from transfer ladle to AOD converter. The molten metal is then decarburized and refined in an AOD converter to less than 0. The major benefit associated with the dilution process comes into play when the oxygen to inert gas ratio is 1: After the change from nitrogen to argon, nitrogen is removed from the bath both by evolved carbon monoxide and argon.
Iron and steel production. This accretion protects the tuyere and surrounding refractory. 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. Praxair can review your system and design an upgrade using: AOD provides an economical way to produce stainless steel with a minimal loss of precious elements.
The stages of blowing remove carbon by the combination of oxygen and carbon forming CO gas. History of ferrous metallurgy List of steel producers. Nitrogen control is a gas — metal reaction. The end result is a cleaner metal coupled with increased productivity.
Argon Oxygen Decarburization Process
Also, aluminum or silicon may be added to remove oxygeh. Other trimming alloy additions might be added at the end of the step. Designed by Elegant Themes Powered by WordPress. Most of the recent converter installations include the use of a top lance for blowing oxygen. Reduction recovers the oxidized elements such as chromium from the slag. Bottom injection usually improves wear characteristics in the barrel section of the converter.
Argon Oxygen Decarburization Process |
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. Annealing Low hydrogen Short circuit. Chromium pickup from the brick is possible. Tuyere size and number depend eecarburization specific process parameters. When the vessel is rotated, the tuyeres are above the bath.
Cooling gases blown through the outer annulus shroud form a metal or oxide accretion called a mushroom at the tuyere tip. Procfss AOD converter is shown in Fig 1. The ratio is lowered with the progress of the decarburization.
To drive the reaction to the forming of CO, the partial pressure of CO is lowered using argon or nitrogen. To achieve this, alloy additions are made with elements that have a higher affinity for oxygen than chromium, using either a silicon alloy or aluminum.
Argon oxygen decarburization
Since the blowing is done along with argon it is possible to carry out the decarburization at a lower temperature. In general, the bath temperature is controlled to orocess than deg C.
Phosphorus, which requires oxidizing conditions, cannot be removed in the converter processing.
Refractory costs are a significant fraction of total operating costs. The system will be tailored to match your current operation with added features found only on the new systems. This argon dilution minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium.