Injection metallurgy and lf

INJECTION METALLURGYINJECTION METALLURGY
AND LADLE FURNACEAND LADLE FURNACE
N. PRAKASAN
ME METALLURGY

Injection methods effectively reduce sulphur
content.
In this method, a strong desulphurizing
reagent in the form of fine powder is injected
(through a lance) in the refined steel bath
along with an inert gas (Argon) as carrier.
Injection reagent may be Metallic like Calcium,
Magnesium or the other form like Lime,
Calcium carbide, Calcium silicide and
Magnesium coke.

Ladle Capacity:
• 40 T – 300 T
Cycle time:
• About 20-50 minutes depending upon the
aim and final chemistry.
Injection rate:
• The injection rate varies between 2 -4 kg/ton
of melt

A ladle with deoxidized (killed) molten steel is
transported to the injection stand and placed
under a cover, through which the injection
lance is lowered and immersed into the melt.
Desulfurization agents are injected in argon
stream. Argon bubbles produce stirring of
the molten steel and the slag promotes
desulfurization.
Stirring also provides thermal and chemical
homogenization of the melt.

The more interfacial area of contact of particles
with the steel bath leads to very efficient
interaction of the reagent with the bath.
The treated steel is covered by a layer of
desulfurizing slag having high solubility of
sulfur and capable to absorb sulfides formed
as a result of active agents injection.
Desulphurization takes place in a short time of
about 8 – 10 minutes and the bath looses
30 – 35o
C temperature.

When the desulphurizing agents are injected
into molten steel in form of a cored wire
containing powder of desulphurizing agent
stirring by argon bubbling from the porous plug
mounted in the ladle bottom is used.
Fumes formed during the operation are
extracted through the cover.
TN (Thyssen Niederrhein) injection system is
more popular.

Benefits of Ladle desulphurization by injection
of active agents:
• Sulphur removal (desulfurization);
• Temperature and chemical homogenizing;
• Non-metallic inclusions removal.
• The effective desulphurization allows to
achieve ultra-low concentrations of sulfur in
steel (0.0002%) and decreases sulphide
inclusions, thereby improves Toughness and
Elongation of the Steel.

Ladle Furnace (LF)Ladle Furnace (LF)

Molten steel in a ladle is treated (refined) in a
device called Ladle Furnace (LF).
It is capable of carrying out Vacuum treatment,
slag refining, Injection etc,
Primary functions of LF are:
• Reheating of liquid steel through electric
power conducted by graphite electrodes.
• Homogenization of steel temperature and
chemistry through inert gas stirring

• Formation of a slag layer that
• Protects refractory from arc damage,
• Concentrates and transfers heat to the
liquid steel,
• Trap inclusions and metal oxides,
• Provide the means for desulphurization by
synthetic slag or by injection metallurgy.

• The slag is primarily modified by the addition
of CaO or CaF2.
• The slag is basic and its typical composition
range is CaO: 50-56%, MgO: 7-9%,
SiO2: 6-12%, Al2O3: 20-25%.
• LF has the ability to make alloying additions.
• LF Provide a means for dephosphorization.

Capacity:
• 10 T - 25 T - DC Ladle Furnace
• 15 T - 150 T - AC Ladle Furnace
Cycle time:
• About 40-50minutes depending upon the aim
and final chemistry and desired temperature
rise.

Slag forming materials used for injection:

The ladle is transferred to the Ladle Furnace
stand where it is placed under a cover
equipped with three graphite electrodes
connected to a three-phase arc transformer.
The ladle bottom has a porous refractory plug,
which is connected to the argon supply pipe at
the Ladle Furnace stand.
The LF stand is also equipped with an addition
hopper mounted on the cover and a lance for
injection of desulfurizing agents.

During the treatment process argon is blown
through the bottom plug for continuous metal
stirring.
Molten steel treated in Ladle Furnace is
covered by a layer of desulphurizing slag.
When the graphite electrodes are submerged
into the ladle, the slag protects the ladle lining
from overheating produced by the electric arcs.
The arcs are capable to heat the steel at the
rate about 3°C/min.

Stirring results in,
• distribution of heat produced by the arcs,
• chemical homogenization
• desulfurization of the steel by the slag.
Fumes formed during the operation are
extracted through the cover.
Alloying elements may be added through the
addition hopper.
Besides refining operations Ladle Furnace (LF)
may serve as a buffer station before
Continuous casting.

Advantages of Ladle Furnace (LF):
• Increase productivity
• Decreasing refining time of EAF
• Decreasing tapping temperature at EAF
• Precise temperature control
• Improved inclusions control and cleanliness
of the steel.

Benefits of Ladle Furnace (LF):
• Sulfur removal (desulfurization);
• Controllable reheating by electric power;
• Alloying;
• Temperature and chemical homogenizing;
• Non-metallic inclusions removal (Oxygent
content upto 30ppm can be attained).

 Introduction to Modern Steel Making
by Dr.R H Tupkary
 Iron Making and Steel Making
by Ahindra Ghosh, Amit Chatterjee
 Lecture 23 : Injection Ladle Metallurgy _
Class notes IIT Madras.
 Ladle Refining_ www.substech.com
REFERENCES :REFERENCES :

Injection metallurgy and lf

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