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VACUUM DEGASSING : Processing in VD shall produce high
quality of cleaner steel billets /blooms .
The main process high lights is as under :
After placing the ladle the VD Vessel and sealing the
cover processing starts .
Vacuum is achieved by operating different ejectors with
the help of super saturated steam .
Under vacuum following “Severts low” the gaseous content
in in liquid steel decreases depending on to their
partiol pressure and longevity of treatment .
Due to Argon Purging under vacuum the non globular shaped
inclusions are arrested to the active basic slag .
AOD (Argon Oxygen Decarburization ): In
decarburization process is being carried out which is
being basically done for further refinement of steel
through reduction of carbon content . The process is
required because the amount of carbon in stainless steel
must be lower than that in carbon steel or lower alloy
steel (i.e., steel with alloying element content below 5%)
. While electric are furnaces (EAF) are the conventional
means of melting steel ,AOD is an economical supplement
for refining the same .In addition ,using AOD for refining
stainless steel increases the availability of the EAF for
melting purposes. The scrap, hot metal / pig Iron and DRI
are processed in an electric are furnace and subsequently
decarburizaed and refined in a special AOD vessel through
submerged tuyeres or top lance decarburizes the molten
molten metal with a minimum of unwanted metallic oxidation
.De oxidation is to be done to produce a clean and uniform
product .The clean steel is cast through continuous
casting machine .
Benefits of the AOD process
High metallic yields
considerably lower material cast due to the ability to use
less –expensive high –carbon Ferro alloy ,sulphur –bearing
scrap and alloys low aquality scrap ,and returns as raw
materials .
Pinpoint process control accuracy in achieving desired
aim chemistries with precise control to 0.01 percent and
lower .
Rapid desulphurization to less than 0.01 percent .
Lead removal to less than 0.01 percent
Cleaner metal ,with residual oxygen ,nitrogen ,and
hydrogen comparable to those achieved in vacuum degassing
.
Raw material savings .Use of least –cost raw materials (
in both the EAF and the AOD ) with regard to content of
carbon ,sulphur, nitrogen or lead
productivity increases because of the followings.
EAF is used only for melting –not for refining
Shorter heat times
Lower refractory consumption
Lower electrode consumption
Quality improvements
Very low levels of dissolved oxygen ,nitrogen ,hydrogen
and sulphur attainable
Cleaner steel
Improved mechanical properties .
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