Vacuum Degassing VOD AOD

During vacuum treatment the carbon, oxygen, nitrogen, hydrogen, and sulfur contents are reduced in different process steps depending on the melt composition. A vacuum alloy hopper system allows for compositional adjustments. Good homogenization and high alloy yields are characteristic features of this process. Depending on the metallurgical reactions in the ladle, a freeboard of 600–1,200 mm is required. In order to increase productivity, the VD system can also be designed as (or extended to) a twin-vessel system.The VOD system is a tank degassing unit which is additionally equipped with an oxygen blowing lance. This additional oxygen supply can be used for the production of extra-low carbon stainless steel grade (forced decarburization)or for chemical heating of the melt in conjunction with aluminum/silicon additions (VD-OB process). The vacuum pump is designed accordingly, having a higher capacity in order to cope with the increased offgas volume.

The VD system is one of the widest used degassing systems in commercial use. In that system a ladle is placed in a vacuum tank and sealed with a vacuum cover for an operation under vacuum conditions. The ladle has to be equipped with a porous plug for inert gas stirring. Vacuum will be created by the steam ejector- or dry mechanical vacuum pumps. During the vacuum treatment carbon, oxygen, nitrogen and hydrogen can be reduced in various steps depending on the melt conditions. Additionally, the VD system can be equipped with vacuum alloy hoppers so that an analysis correction and adjustment can be executed during vacuum treatment. Advantages of this system include good homogenization as well as higher alloys yields.

For the VOD treatment, one can take advantage of the fact that, under vacuum, decarburization with oxygen occurs before oxidation of chromium thus attaining very low carbon contents with a slight loss of chromium. For that operation an oxygen blowing lance is installed on top of the vacuum cover.

Our Design takes care of

• Single or twin operation stand
• Heat sizes up to 100 t
• Steam ejector vacuum system
• Dry mechanical vacuum pumps ( New Trend)
• Alloying under vacuum conditions
• Complete in house design
• VOD-ladle cover with flat inner surface (steel plates or copper plated)
• Automatic gas coupling system (TBR)
• Wire feeding machines
• All auxiliary equipment out of one hand