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Quality Steel Castings Start Here!
There are two choices for producing alloy and stainless steel castings: 1) melt and refine your own material, 2) purchase virgin stock in pre-determined chemistries, or 3) combine master alloy with your own material. A larger number of casters are foregoing the
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| capital, time, energy and overhead necessary to maintain a refining melt shop and opting for purchasing the metal in ingot form. Although there are a number of casters continuing to pour alloy and stainless steel directly from refining vessels, few can optimize these operations in conjunction with casting schedules
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Metal Charging an AOD |
Example of small ingot |
and workforce. Successful businesses in mature industries such as specialty steel must reduce their costs and look for market niches where they can dominate with a unique product. The past 10 years have witnessed good stainless steel shipment growth--despite record import levels. Widespread adoption of argon/oxygen decarburization (AOD) by stainless producers has lowered the cost of production for stainless and opened a vast array of possibilities for new products. R&D has produced products such as ultra-low carbon ferritic grades, high alloy austenitics and duplex stainless steels with better stress corrosion cracking resistance than austenitic and better
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formability than the super-ferritics. Competitive pressures on the U.S. specialty steel will not diminish. Improved consistency and quality are key elements in success. Modern AOD systems, like those installed at Alloy Resources, Inc., are computer linked to allow vessel operations and calculations for optimizing refining and least cost additions for each grade produced. The (IRS Praxair) control system provides true integration and control of the AOD process, modeling carbon and temperature during decarburization and controlling reduction temperature and chemistry with more accuracy than through previous manual methods. The “AOD Wizard” program sequences and performs tasks and calculations including automatic vessel positioning, process gas
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selection and proper gas ratio selection, and alloying requirements. Computer-controlled, standardized operating procedures allow consistency and control of the three AOD refining steps,
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| Decarburization, Reduction, Final Chemistry, and Terperature trim. There are good reasons why over 150 AOD vessels are in operation worldwide.The AOD furnace developed by Union Carbide Corporation (subsequently Linde, Praxair) in the 1950s and placed into production in the 60s was developed to improve ferroalloy yields in alloyed and stainless steel production evolving into the standard for producing a majority of the world's stainless steel. It is energy efficient, material efficient, and is part of the reason why a pound of stainless
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steel costs less in constant dollars today than it did thirty years ago. The AOD furnace is supplied with liquid metal from scrap and raw materials melted in arc or induction furnaces. Liquid metal is charged into the AOD for refining, degassing, and chemistry homogenization through the combination of Oxygen, Nitrogen, Argon gases blown through submerged tuyeres and lance at sonic velocities.The stirring and refining action provides chemical heat generation and dilution of oxygen. A slag layer consisting of
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molten flux and impurities from the melt forms on top of the molten furnace charge.This slag layer protects the molten metal from the air and removes impurities. The result is the ability to |
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| control desulphurization, removal of carbon, reduced metallic oxidation and provide an environment promoting excellent recovery of alloying elements. All accomplished with low amounts of residual oxygen, nitrogen and hydrogen without additional processing or expensive degassing equipment and excellent chemistry control. In addition, the AOD process effectively removes low volatility trace elements with its high vapors pressures.
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| For information about ARI Metal products offered through BuyCASTINGS.com go to: http://www.ingot.us. To discuss availability of AOD quality ingots call Lee Morris at: (937)259-1316 or email to: lmorris@buycastings.com Visit buyCASTINGS.com at the ICI show at Booth #19, Nove 7-8, 2005 in Dearborn, MI. |
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