Silicon&Aluminium Killing
limesh M
What is meant by Silicon&Aluminium killing of steel?Is there any
significant difference between both process and resulting quality of
material like grain size and other metallurgical property?
Thanks and Regards
Prabhu Kumar L
Silicon & Aluminum are called as deoxidizing elements, which will be
added during steel making process for deoxiding and grain refining
purpose. Based on the need for end product it can be added together or
individual element.
Killed steel: De-oxidation or killing is a process by which strong
deoxidizing element is added to the steel to react with the remaining
oxygen (oxygen used of melting purpose) in the liquid bath to prevent
any further reaction between carbon and oxygen. Si & Al are high
affinity for oxygen and hence produce oxides such as Al2O3 & SiO2 which
will be removed from top of the steel ingot. This would eliminate the
carbon boil (CO2, CO) and killing the heat and hence the required % of
Cabon is retained in the steel.
Basically pure Oxygen is used for purpose of steel making process which
is called basic oxygen furnace.
Si Killed steel: This type of steel shall have coarse grain structure
(grain no. 1 to 5) and will not react for grain refinement.
Al Killed steel: This will act as deoxidizing and grain refinement as
well and then the structure will be fine grain ie. grain no. 6 & above.
Al will react with Nitrogen to form aluminum nitride to initiate the new
grains at grain boundaries and hence more grains will be formed ie. fine
grains. For notch toughness requirements, steel shall have fine grain
size and hence it will be treated with Al.
Si & Al killed steels: This type of steel called silicon killed, fine
grain. The later is achieved by addition of Al.
Hope it clarifies.
Regards,
L. Prabhu kumar,
Sr. Principal Engineer,
Equipments & Materials Dept.,
Saipem India Projects Limited,
Nungambakkam High Road, Chennai - 600 034, India.
Tel:+91 44 43906588, Ext.: 588, Fax:+91 44 66840345,
Mobile Ph. No.: +91 9003010978.
Dear All,
Thanks and Regards
--
To post to this group, send email to material...@googlegroups.com
To unsubscribe from this group, send email to
materials-weld...@googlegroups.com
For more options, visit this group's bolg at
http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views
and meant for educational purposes only, Users must take their own
decisions w.r.t. applicable code/standard/contract documents.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
DISCLAIMER: The information contained in this communication is intended solely for the use of the individual or
entity to whom it is addressed and others authorized to receive it. It may contain confidential or legally privileged
information. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution
or taking any action in reliance on the contents of this information is strictly prohibited and may be unlawful. If
you have received this communication in error, please notify us immediately by responding to this email and then
delete it from your system. Saipem India Projects Limited (SIPL) is neither liable for the proper and complete
transmission of the information contained in this communication nor for any delay in its receipt.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
limesh M
John Henning
Limesh,
The following excerpted from “The Making, Shaping and Treating of Steel” , 10th Edition, in Part V, Ladle Treatment of Steel, pages 481 and 482:
“Deoxidation is the last stage of steel making. In all types of steel making practices, the steel bath at the time of tapping contains 400 to 800 ppm of oxygen. Deoxidation is carried out during tapping by adding into the tap-ladle appropriate amounts of ferromanganese, ferrosilicon, and /or aluminium or other special deoxidizers. . . . Killed steel is deoxidized to such an extent that there is no gas evolution during solidification. Aluminum is used for deoxidation, together with ferroalloys of manganese and silicon, in certain cases calcium silicides or other special strong deoidizers are used (ladle practice). . . . It has long been recognized from the early days of the continuous-casting operation nearly three decades ago that casting difficulties and poor surface conditions are often experienced with aluminum-killed steels. It is for these reasons that other forms of deoxidation are often preferred in a number of steel processing operations, e.g. silico-manganese deoxidation and/ or vacuum-carbon deoxidation. . . .”
Does this answer your questions?
John
Sunil
The following is an abstract from the book of Mr. David A. Hansen
"Raw steel is saturated with oxygen in the form of both
dissolved gas and as iron oxides.The oxygen can combine with
carbon,also dissolved in liquid steel to form carbon monoxide.The
reaction causing violent boiling during the pouring and solidification
process.By adding an oxygen scavenger such as silicon to the liquid
steel before it is poured,the excess oxygen can be removed as slag.The
resulting material doesnot boil during pouring and cooling,thereby
producing a more homogeneous"killed" steel.Such steels are cleaner and
contain fewer defects than "unkilled" or "wild" steels.ASTM A106
Pipe,A105 forgings and A516 plate are examples of killed carbon steel
products.Cast carbon steel products are also killed,eventhough typical
ASTM specifications for casting do not mention the requirement.
Killing with an oxygen scavenger such as silicon is the
primary method of deoxidation.A less common method is vaccum
degassing,which is usually a secondary measure,employed when very
clean steels are required.Vaccum degassing not only assists in
controlling oxidising gases such as oxygen and carbon dioxide,but will
help to limit non-oxidising gases such as Nitrogen and Hydrogen.
Steels killed with a combination of silicon and aluminum or
aluminium alone leave a fine austenitic grain size.They are preferred
for applications requiring low temperature toughness;ASTM A 516
(plate) is an example.Such steels are usually described in ASTM
specifications as being made to "fine grain practice".Although ASTM
specifications for steel products usually do not indicate a
requirement for aluminium content.Steels killed with aluminium will
have aluminium perecentage in the range of 0.02 to 0.05 wt.
perecentage."
Regards,
Sunil
> > solely for the use of the individual or
> > entity to whom it is addressed and others authorized to receive it. It may
> > contain confidential or legally privileged
> > information. If you are not the intended recipient, you are hereby notified
> > that any disclosure, copying, distribution
> > or taking any action in reliance on the contents of this information is
> > strictly prohibited and may be unlawful. If
> > you have received this communication in error, please notify us immediately
> > by responding to this email and then
> > delete it from your system. Saipem India Projects Limited (SIPL) is neither
> > liable for the proper and complete
> > transmission of the information contained in this communication nor for any
> > delay in its receipt.
>
> > --
> > To post to this group, send email to material...@googlegroups.com
> > To unsubscribe from this group, send email to
> > materials-weld...@googlegroups.com
> > For more options, visit this group's bolg at
> >http://materials-welding.blogspot.com/
> > The views expressed/exchnaged in this group are members personel views and
> > meant for educational purposes only, Users must take their own decisions
>
> - Show quoted text -