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
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of limesh M
Sent: Tuesday, June 15, 2010 5:18 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:5604] RE: 5599] Silicon&Aluminium Killing
Dear All,
I have two more doubts , wether we are adding Si and Al in its pure form or some other compounds form which contains Si and AL abundantly?Are we performing killing operation after making steel(ie, First steel making ,second killing operation) or during steel making process everything happening(ie, steel making and killing happening at the same time with same process)?
Thanks and Regards
On Tue, Jun 15, 2010 at 3:19 PM, Prabhu Kumar L <l.prabhukumar@saipem-india.com> wrote:
Dear Limesh,
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.
-----Original Message-----
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of limesh M
Sent: Tuesday, June 15, 2010 2:05 PM
To: Materials & Welding
Subject: [MW:5599] Silicon&Aluminium Killing
Dear All,
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
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