Argon oxygen decarburization

The AOD process ( argon oxygen decarburization of English, German argon - oxygen decarburization ) is a converter refining process for the production of stainless steel and other high alloy steels.

The procedure in 1954 was developed by the U.S. company Praxair. In 2007, about 130 AOD converter with capacities 1-160 tons in use worldwide.

Process

Of the crude to be treated is usually obtained from scrap in an arc furnace and then filled to carry out the process in a so-called AOD converter. The process is similar to the Linz- Donawitz process, differs from this however, is that pure oxygen, but an argon -oxygen mixture is injected into the molten steel. The oxygen content in the gas mixture is continuously reduced during the hour-long blow - usually from about 80 percent to 20 percent. Which is supplied through nozzles in the bottom and in the side walls of the converter.

By the addition of argon as the inert gas, the partial pressure of oxygen is reduced. Which promotes the oxidation of the carbon while the undesired slagging of alloying metals such as chromium and manganese, is suppressed.

Completely prevent these slagging can not however.

Thereby to recover the oxidized metals, the slag is reduced by refining by the addition of lime and silicates. The melt with burnt lime is desulfurized.

For a better mixing of the melt is blown during the reduction and desulfurization of pure argon.

Consumption values

At the end of the process, the carbon content in the steel is only about 0.015 percent. About two percent chromium lost. 25 cubic meters of oxygen and 20 cubic meters of argon are consumed per ton of steel. To reduce costs, argon is sometimes replaced by the start of the process, nitrogen or compressed air. Up to 7 tons of lime are consumed