This presentation will cover the topics & concepts of Ladle Metallurgy in a detailed manner.

1. LADLE
METALLURGY
Chennai
02/07/2021

2. Outline
Importance of Steel
Secondary steel making – What, When, Why and How?
Objectives of Ladle metallurgy
Reheating / Stirring
Ladle Furnace
Deoxidation
Desulphurization
Degassing
AOD
CAS – OB process

3. Worldwide steel production and India's position
■ In CY 2019, the world crude steel production reached 1869 million tones (MT)
and showed a growth of 3% over CY 2018.
■ China - World’s largest crude steel producer in 2019 (996 MT)
■ India (111 MT) is World’s second largest crude steel, followed by Japan (99 MT)
and the USA (88 MT) - based on rankings released by the World Steel Association
■ India is 2nd largest finished steel consumer in the world after China & USA in
2019,

4. What is
Ladle Metallurgy?
• Metallurgical reactions happening in a Ladle - Ladle Metallurgy
• After taping from converter or electric furnace, molten steel for
high quality or special applications is subjected to further refining
in a number of alternative processes collectively called as Ladle
metallurgy or Secondary steel making
• Cost-efficient to operate the primary furnace as a high-speed
melter and to adjust the final chemical composition and
temperature of the steel after tapping.
• Equipment design and operation of ladle helps certain
metallurgical reactions to be more efficiently performed
• Ladle – An open-topped cylindrical container made of heavy steel
plates and lined with refractory
- Used for holding and transporting liquid steel.

5. Process flow – Iron and Steel making

6. Purpose of ladle metallurgy

7. Objectives of ladle metallurgy
1. Homogenization
2. Deoxidation
3. Desulphurization
4. Decarburization
5. Degassing
6. Inclusion modification & Cleanliness
7. Alloying

8.  VD – Vacuum Degassing
 VOD – Vacuum Oxygen Decarburization
 IGP – Inert gas purging
 IM – Injection Metallurgy
 VAD – Vacuum Argon Decarburization
 LF – Ladle Furnace
Objectives and Processes

9. Reheating / Stirring
Ladle stirring is an essential operation during secondary steelmaking in order to:
■ homogenize bath composition;
■ homogenize bath temperature;
■ Fasten deoxidation
■ facilitate slag-metal interactions essential for processes such as desulfurization;
■ accelerate the removal of inclusions in the steel
- Argon is purged through the liquid steel, either via a submerged lance, or by porous
plugs in the bottom of the ladle (Inert Gas purging)

10. Ladle Furnace
• The ladle with liquid steel is brought to the LF
station, where a top cover is placed on the
ladle and graphite electrodes are introduced.
• In the LF, deoxidation and composition
adjustments are carried out by additions, and
the temperature of the melt is adjusted by arc
heating (graphite elecrodes)
• Bath stirring is achieved by means of argon
purging from the bottom
•Formation of slag layer that protects refractory from arc
damage, concentrates and transfer heat to the liquid steel,
trap inclusions and metal oxides, and provides means for
desulphurization.
• Additions of ferro alloys to provide for bulk or trim
chemical control.
• Cored wire addition for trimming and morphology control.
• Provide a means for deep desulphurization &
dephosphorization
• Act as a buffer for downstream equipment and process. Ref: Iron and steel making Book, Ahindra
Ghosh & Amit chatterjee

11. Deoxidation
 Lowering of dissolved oxygen levels in molten steel by the addition of strong oxide
formers such as Mn, Si, Al, Ca (as ferromanganese, ferrosilicon, silico-manganese,
aluminum, calcium silicide) in the ladle is known as deoxidation.
 Solubility of oxygen in solid steel is negligibly small. Therefore, during solidification of
liquid steel, the excess oxygen is rejected by the solidifying metal.
 This excess oxygen causes defects by reacting with C, Mn, Si, etc. resulting in the
formation of blowholes (primarily CO) and oxide inclusions (FeO–MnO, SiO2, Al2O3, etc.).
 Strong to weak deoxidizers Ca > Al > Si > Mn

12. Desulphurization
■ Reduction of sulfur concentrations as
low as 0.002%
■ Injection of desulphurization reagents -
Lime, calcium carbide, soda ash,
magnesium or calcium-
silicon alloy containing 30 percent
calcium (effective desulfurizer).
■ Metallic calcium desulfurizes by forming
the very stable compound calcium
sulfide (CaS), and it is alloyed
with silicon because pure calcium reacts
instantaneously with water and is
therefore difficult to handle.
■ Inclusion shape control – CaS inclusions
are formed instead of MnS.

13. ■ Removal of gases like N and H from the molten steel is referred as Degassing
■ When liquid steel solidifies, excess nitrogen forms stable nitrides of Al, Si, Cr,
etc. Dissolved nitrogen affects:
- Toughness and ageing characteristics of steel
- Tendency towards stress corrosion cracking
- Strain hardening effect
Dissolved hydrogen causes a loss of ductility of steel
Degassing is effective under Vacuum. Types:
■ Ladle degassing processes (VD, VOD, VAD)
■ Stream degassing processes
■ Circulation degassing processes (DH and RH).
Degassing

14. RH Degassing (Ruhrstahl Heraus)
• Molten steel is contained in the ladle. The
two legs of the vacuum chamber are
immersed into the melt.
• Argon is injected into the upleg. Rising and
expanding argon bubbles provide pumping
action and lift the liquid into the vacuum
chamber, where it disintegrates into fine
droplets, gets degassed and comes down
through the downleg snorkel, causing melt
circulation.
• Provisions are available for argon injection
from the bottom, heating, alloy additions,
sampling
Ref: Iron and steel making Book, Ahindra
Ghosh & Amit chatterjee

15. Vacuum Treatment
VOD – Vacuum Oxygen Decarburization
• VOD is often used to lower the carbon
content of high-alloy steels without also
over oxidizing such oxidizable alloying
elements as chromium
• A modification of the tank degassers is
the vacuum oxygen decarburizer (VOD),
which has an oxygen lance in the centre
of the tank lid to enhance carbon
removal under vacuum.
• Tank degassers that have electrodes
installed like a ladle furnace, thus
permitting arc heating under vacuum -
Vacuum arc degassing, or VAD
.

16. • Argon oxygen decarburization (AOD) is a process primarily used in stainless steel
making and other high-grade alloys with oxidizable elements such as chromium and
aluminum.
• After initial melting, the metal is then transferred to an AOD vessel where it will be
subjected to three steps of refining namely (i) decarburization, (ii) reduction, and (iii)
desulphurization.
• The key feature in the AOD vessel is that oxygen for decarburization is mixed with argon
or nitrogen inert gases and injected through submerged tuyeres. This argon dilution
minimizes unwanted oxidation of precious elements contained in specialty steels, such
as chromium.
AOD Process

17. CAS - OB
■ CAS-OB stands for Composition Adjustment by Sealed Argon Bubbling with Oxygen
Blowing)process
■ Developed in by Nippon Steel Corporation in 1980’s
■ The process allows alloy additions to be made under an inert argon environment. It allows
simultaneous addition of Al and O2 gas blown through a top lance. These react to form
Al2O3 and generate a considerable amount of heat due to exothermic nature of the
reaction. The CAS-OB process, therefore results into chemical heating of the liquid steel.

18. “The best way to predict future is to
create it”
Thanks!!