FIELD OF THE INVENTION
The present invention relates to a system for Online Purging (OLP) of Argon gas
during tapping of liquid steel from the converter to enhance mixing of ferro-alloys
during tapping and continued till the ladle reaching the position of decoupling, lifting
and transferring, in order to counter the effect of thermal stratification ensuring
homogeneous temperature and composition of molten steel sent for treatment in
Ladle Heating Furnace .(LHF) for continuous casting. The invention is further directed
to a process for such purging of Argon gas comprising range of selective pressure,
flow rate and duration during tapping, involving continuous purging of liquid steel by
argon gas. Importantly, the argon purging following se'ective parameters and the
modified addition during tapping and transferring till decoupling and lifting of liquid
steel ladle before sending to LHF for refining, helps achieving lower level of dissolved
oxygen at the beginning of LHF refining and percent of heats with oxygen content
less than 25 PPM has been 34.5% in OLP heats as compared to 27.8 for normal
heats and heats with oxygen >100 PPM has been reduced from 39.2% to 27.2%,
and thus enabling faster and improved refining of steel in LHF. Advantageoulsy also
the OLP according to the present invention is directed to further favor improved
recovery of ferro-alloys and reduced consumption of aluminium and Si-Mn per ton of
molten steel sent to caster, thus economizing cost of inputs.
BACKGROUND ART
It is a well known practice in steel melting shop (SMS) of steel plants, that after
completion of each heat in the converter, the liquid metal is tapped in a ladle for
transferring for further processing in Ladle Heating Furnace or other secondary
refining units for desired deoxidation and refining to obtain desired temperature and
composition for continuous casting. In the normal practice, all the heats after tapping
from converter is transferred to Ladle Heating Furnace (LHF) for deoxidation, refining
and final temperature and composition adjustment before dispatch to caster. Usually,
during the post-tap holding period the steel undergoes thermal stratification,
creating unfavorable temperature distribution and lack of homogeneity in
composition and temperature and the total process of conventional tapping,
transferring and refining takes more time to achieve desired result in refined molten
steel for casting.
2

After tapping from converter, iadle with liquid steel is sent to secondary refining
units like argon rinsing unit, ladle furnace, RH degasser, VAD etc for achieving
desired temperature and composition before dispatch to caster for casting in to
billets/blooms/slabs. Argon gas is always purged through bottom or top in these
processes for improving mixing characteristics. However, normally no purging
treatment by argon gas of liquid steel ladle is carried during tapping and it's transfer
to secondary refining by ladle transfer car. Also it is worth mentioning that inert gas
such as argon has been used for preventing the oxidation of melt during tapping and
teeming by supplying a protective screen of argon gas which maintains inert
atmosphere.
There has been thus a continued need to develop a method and a system to carry
out such method that would be capable to provide uniform and homogeneous
temperature and composition of the steel for treatment in Ladle heating furnace
(LHF) to be made finally ready after de-oxidizing and refining before it is sent to
caster for continuous casting of billets/blooms/slabs of desired chemistry at lesser
time and cost having improved refining and higher productivity.
OBJECTS OF THE INVENTION:
Thus according to the basic aspect of the present invention there is provided a
system for on Line Purging (OLP) for controlled Argon purging operation during
tapping of steel from converter in to ladle up to 150T capacity and transferring till
de-coupling/lifting before sending to Ladle heating Furnace (LHF), and selective
modified alloy addition practice in ladle during tapping, for improvement in refining
practice and shop productivity. The system is capable of being used in any converter
shop with modifications based on shop logistics.
A further object of the present invention is directed to on line purging system
wherein liquid steel is purged with argon gas during tapping from converter to ladle
and till de-coupling and lifting of the ladle before transfer to LHF in order to enhance
mixing of ferroalloys during tapping and to counter the effect of thermal stratification
during post-tap holding period.
3

A further object of the present invention is directed to On Line purging system
wherein liquid steel is purged with argon gas during tapping wherein argon gas is
bubbled in to the bath of steel to help generate enough bath turbulence to produce
thermal and chemical homogeneity in steel before treating in LHF and sending to
caster.
A still further object of the present invention is directed to On Line purging system
wherein liquid steel is purged with argon gas during tapping wherein the Argon
purging is carried out by controlling the parameters in terms of pressure, flow rate
and duration of purging such as to achieve the objective of desired thermal and
chemical homogeneity, avoiding effect of thermal stratification during post tap
holding period, for a particular steel composition prior to casting after treatment in
LHF.
A still further object of the present invention is directed to On Line purging system
wherein liquid steel is purged with argon gas during tapping involving selective alloy
addition e.g. of Aluminium in addition to normal addition of Ferrosilicon and Silico-
manganese such as to achieve improved recovery of ferroalloys and reduced
consumption of Aluminium and Si-Mn for OLP heats by 0.1 kg/t and 0.53 kg/t
respectively.
A still further object of the present invention is directed to On Line purging system
wherein liquid steel could be purged with argon gas during tapping wherein the
dissolved oxygen content over 100 PPM at the beginning of LHF refining, could be
reduced to 27.2% from the conventional level of 39.2% and thus enabling faster and
improved refining in LHF.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a
system for on-line purging for purging liquid steel during tapping and transfer to LHF
comprising:
4

a converter in steel making means a vessel where hot metal (Liquid pig iron)
is converted in to steel by removal of carbon;
a iadle is adapted for receiving and holding the liquid steel that is tapped
from the converter before it's transfer to Ladle Heating Furnace (LHF);
a pipeline operatively connected at one end to a source of Argon gas and at
its other end adapted for coupling with respect to the ladle bottom for
continuous purging of the liquid steel in the ladle by said Argon gas thereby
favouring enhanced mixing of the ferroalloys during tapping and counter the
effect of thermal stratification of the steel melt in the ladle prior to its transfer
in said Ladle heating Furnace.
Another aspect of the present invention directed to a system for on-line purging for
purging liquid steel during tapping and transfer to LHF comprising said Argon gas
pipeline the pipeline preferably suitably protected and covered with angles and/or
channels and comprising a flexible hose operatively connected through a stall torque
motor operated hose reeling drum with instrumentation for flow control and
measurement. (
A further aspect of the present invention directed to said system for on-line purging
for purging liquid steel during tapping and transfer to LHF, adapted for bubbling of
the Argon gas in to the steel bath such as to generate enough turbulence to produce
thermal and chemical homogeneity.
A still further aspect of the present invention directed to a system for on-line purging
for purging liquid stee1 during tapping and transfer to LHF wherein, said ladle is
disposed on ladle transfer cars for transposing teeming ladle from BOF to LHF.
5

A still further aspect of the present invention directed to said system for on-line
purging for purging liquid steel during tapping and transfer to LHF wherein, said hose
reeling drum comprise rotary joint/coupling for the incoming pipeline, with the
torque provided by the motor calculated to match the hosepipe weight per unit
length for desired winding and unwinding torque.
A still further aspect of the present invention directed to a system for on-line purging
for purging liquid steel during tapping and transfer to LHF comprising control panel
installed on the structural platform for the hose reeling drum for operation in
auto/local mode with selection switches for selection of auto or local mode of
operation.
According to yet another aspect of the present invention directed to a system for on-
line purging for purging liquid steel during tapping and transfer to LHF wherein, said
control panel comprise visual indication for purging cycle ON/OFF condition for safety
during coupling and decoupling operations.
A still further aspect of the present invention directed to said system for on-line
purging for purging liquid steel during tapping and transfer to LHF wherein the
instrumentation means selectively comprise pressure regulator, solenoid valves,
isolation valves rotameter, and pressure gauge.
Another important aspect of the present invention is directed to a method of on-line
purging of liquid steel during tapping and transfer till the position of decoupling
before lifting the ladle for treatment in LHF using the system comprising:
6

a) positioning the ladle for the purging treatment; and
b) selectively treating the liquid steel with Argon gas purging at a
pressure of 6-8 Kg/Cm2 with a flow rate of 200-400 LPM through ladle
bottom, followed by aluminum addition 0.6-1.3 Kg/t alongwith normal
ferro-alloys additions; and
c) turning off the purging gas preferably by shutting off the solenoid
valve before decoupling.
A still further aspect of the present invention directed to a method of on-line purging
of liquid steel as claimed in claim 9 wherein the portion of the pipeline after the
solenoid valve is de-pressurized before decoupling preferably using separate solenoid
valve for such purpose and thereafter the ladle is lifted for further treatment in LHF.
The present invention directed to the system for on-line purging for purging liquid
steel during tapping and transfer to LHF and a method of on-line purging for purging
liquid steel during tapping and transfer to LHF using said system, is described in
greater details with reference to the accompanying non limiting illustrative drawing.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1: is the illustration of the schematic arrangement of the online purging (OLP)
system during tapping and till transferring to LHF, according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS
The present invention is directed to an online purging (OLP) system during tapping
and till decoupling position before transfer to LHF by argon gas and a method
7

therefore, in order to ennance mixing of ferroalloys during tapping and to counter
the effect of thermal stratification and also reduce consumption of aluminium, Si-Mn
etc. In this system argon gas is bubbled in to the bath of steel to help generate
enough bath turbulence to produce thermal and chemical homogeneity. More
importantly, coupled with the controlled Argon flow during purging through liquid
steel during tapping, selective Aluminium addition during purging further favor
improved recovery of ferro-alloys and reduced consumption of aluminium and Si-Mn,
improved refining of steel in LHF in the next step and higher productivity in SMS
plant. Present OLP system is adapted for operation during tapping in the converters
up to 150 ton capacity.
The method for purging using such a system directed to faster and improved steel
refining, reduced dissolved oxygen level in LHF obtained by favored incorporation of
the appropriate process parameters viz the selective ranges for argon gas supply
pressure, argon gas flow rate and time duration for purging of liquid steel with argon
gas and in association with a modification in ladle addition practice during tapping.
Reference is first invited to the accompanying Figure 1, wherein an embodiment of
the present system of online purging (OLP) during tapping of liquid metal from the
converter has been schematically illustrated.
Design of such a system is adapted for desired On Line Purging of liquid steel during
tapping and transfer till the position of decoupling before lifting the ladle for
treatment in LHF.
The schematic arrangement of OLP system as illustrated in Figure 1, comprises stall
torque motor operated hose reeling drum and instrumentation for flow control and
measurement. The system is adapted for continuous purging of liquid steel by argon
gas through ladle bottom for a duration from after one minute of start of tapping to
continued up to the de-coupling station where ladle is lifted for transfer to LHF for
further treatment, the total OLP system may be described with respect to the
following subsystems forming part of and operatively performing exclusive
independent function to obtain the desired objective in combination with the others
in the system.
8

The Hose reeling drum assembly of the system comprising the stall torque motor
operated hose reeling drum(3) has been installed for the ladle (2) to receive liquid
steel at the tapping point from the LD converter(l) up to 150 T capacity, placed on
the transfer cars transporting teeming ladle from BOF to LHF. The hose reeling
drum(3) has rotary joint / coupling for the incoming pipeline. The torque provided by
the motor has been calculated to match the hosepipe weight per unit length for
providing the appropriate winding and unwinding torque. The system is designed for
carrying argon gas through interconnection of Hose having ID(Internal diameter) of
20mm NB and pipe connections of 20mm NB. The distance traveled by the ladle on
transfer car (2) from drum mounting to tapping location is 30 meters approx and the
total travel from end to end is 50 meters max., the average speed of travel being 30
m/min.
The suitably configured control panel has been installed on the structural platform for
the hose reeling drum and its drive motor for operation in auto / local mode. The
panel has selection switch with lock for selection of local / auto operation. The panel
is operated in local mode during maintenance or hose replacement. The control panel
is also adapted to provide visual indication for purging cycle ON / OFF condition to
the operator for safety during coupling and decoupling of the quick couplings (5) at
the ladle bottom.
For distribution of Argon gas in the system of argon purging during tapping according
to the present invention, a network of fixed pipeline from Argon mains to valve stand
is installed from valve stand to flexible hose through a pressure reducing valve (6) to
SS wire embedded flexible hose(4) wound on reeling drum and also from flexible
hose to quick coupling (5) on the Ladle Car. The fixed pipelines from the argon mains
to different locations has been laid through appropriate route. Necessary supports
and clamps have been provided.
The fixed pipe line on the ladle car has been routed such that it is protected from any
falling molten slag / metal from the ladle and has been suitably covered with angles /
channels to protect it from falling slag/metal, wherever required. The pipeline is
firmly clamped to the ladle car structure. The hose pipe fixing location on the ladle
car is such that the hose dispensing is run at a safe distance of 1000mm away from
the rail track to eliminate chances of interference / entanglement of the hose with
9

the steel transfer car. A number of fittings like sockets, tee, reducer bends have
been mounted as per requirement of the piping layout on board. The broad
specification/operating parameters of pipe line installed on car body/near hose
reeling drum is as under:

Working medium Argon
Operating Pressure 5-10 kg/cm2
Diameter 3/4" (20 mm NB)
Material Hot finish seamless, Medium Duty, conforming to
IS : 1239 (Part 1) : 2004
Length of pipeline 300 m (approx)
Lagging Asbestos rope where required
The instrumentation part of the system for controlled use of argon purging during
tapping to achieve desired result of faster and improved refining of steel in LHF and
reduced consumption of input deoxidisers and lesser dissolved oxygen in steel before
casting are achieved through the following elements used in the system :
i) Pressure Regulator : 3 nos
ii) Solenoid Valve : 3 nos.
Direct acting, 2 way,
Normally Closed (NC) type
iii) Solenoid Valve : 3 nos.
Direct acting, 2 way,
Normally Open (NO) type, with silencer
iv) Isolation Valve : 8 nos.
Type Ball valve (Full bore)
v) Isolation Valve : 3 nos.
Type Globe (Forged Steel Bolted Bonnet)
vi) Rotameter (On-line) : 2 sets
vii) Pressure gauge : 3 nos.
(Bourdon Type, Accuracy +. 1% of F.S.D)
The present system is a simple and operator friendly one, with all the controls
conveniently available to the operator for controlling the purging gas flow. Practice of
O'.P and COHLIOI on process parameters during purging involve keeping the steel
10

ladle on the steel transfer car (STC) by crane. The trailing hose from Hose Reeling
Drum(HRD) is permanently coupled to the steel transfer car on the same side as the
HRD and is mounted on a mast on STC to prevent damage / wear out by sliding on
the floor. The operator manually connects the coupling between the ladle car pipeline
and ladle pipeline after placing the empty ladle on STC. The ladle car is moved on
track and placed at the tapping position with desired accuracy to favor matched
connection of tapping point of Converter and ladle and quick-coupling of flexible hose
/ fixed pipe line for bottom purging of Argon gas.
The purging is started after one minute of start of tapping of liquid steel and
continue till the end of tapping and transfer to up to the de-coupling station. The
flow of purging gas is started from the tapping pulpit (at 9.5m level) with the help of
solenoid valve for each converter. The flow control of purging gas i.e. argon is done
by a manual ball valve. Argon gas is purged utilizing OLP system at a pressure of 6-8
Kg/Cm2 with a flow rate of 200-400 LPM through ladle bottom.
Aluminium addition (0.6 - 1.3Kg/t) is done along with normal ferro-alloys additions.
In the normal practice without OLP system no aluminium addition is done during
tapping. The purging gas is turned OFF before decoupling by shutting off the solenoid
valve with the help of a push button switch near.decoupling point However, it is also
ensured that the portion of pipeline after the solenoid valve is de-pressurised before
decoupling with the help of separate solenoid valve (NO type). Ladle is then lifted for
further treatment in LHF.
It is thus possible by way of the present invention directed to a system of On Line
Purging (OLP) of molten steel during tapping from converter in ladle placed on
transfer car, wherein the liquid steel is purged with argon gas during tapping such
that the argon gas is bubbled in to the bath of steel to help generate enough bath
turbulence to produce thermal and chemical homogeneity in steel before treating in
LHF , eliminating thermal stratification and sending to caster. The method of the
present invention further incorporates modified addition practice wherein aluminium
in selective weight percent is added to the molten steel in ladle during purging in
order to achieve on one hand faster and improved refining of steel during treatment
in LHF and on the other hand further favor improved recovery of ferro-alloys and
reduced consumption of aluminium and Si-Mn and higher productivity in SMS plant.
11

WE CLAIM:
1. A system for online purging (OLP) during tapping and till decoupling position
before transfer to LHF by argon gas comprising:
a converter in steel making means a vessel where hot metal (Liquid pig iron)
is converted in to steel by removal of carbon;
a ladle is adapted for receiving and holding liquid steel tapped from the
converter before its transfer to Ladle Heating Furnace (LHF);
a pipeline operatively connected at one end to a source of Argon gas and at
its other end adapted for coupling with respect to the ladle bottom for
continuous purging of the liquid steel in the ladle by said Argon gas thereby
favouring enhanced mixing of the ferroalloys during tapping and counter the
effect of thermal stratification of the steel melt in the ladle prior to its transfer
to said Ladle heating Furnace.
2. A system for on-line purging for purging liquid steel during tapping and before
transfer to LHF as claimed in claim 1 comprising said Argon gas pipeline
which is suitably protected and covered with angles and/or channels and
comprising a flexible hose operatively connected through a stall torque motor
operated hose reeling drum with instrumentation for flow control and
measurement.
12.

3. A system for on-iine purging for purging liquid steel during tapping and
before transfer to LHF as claimed in anyone of claims 1 or 2 adapted for
bubbling of the Argon gas in to the steel bath such as to generate enough
turbulence to produce thermal and chemical homogeneity.
4. A system for on-line purging for purging liquid steel during tapping and
transfer to LHF as claimed in anyone of claims 1 to 3 wherein said ladle is
disposed on ladle transfer cars for transporting teeming ladle from BOF to
LHF.
5. A system for on-line purging for purging liquid steel during tapping and
transfer to LHF as claimed in anyone of claims 1 to 4 wherein said hose
reeling drum comprise rotary joint/coupling for the incoming pipeline, with
the torque provided by the motor calculated to match the hosepipe weight per
unit length for desired winding and unwinding torque.
6. A system for on-line purging for purging liquid steel during tapping and
transfer to LHF as claimed in anyone of claims 1 to 5 comprising control
panel installed on the structural platform for the hose reeling drum for
operation in auto/local mode with selection switches for selection of auto or
local mode of operation.
7. A system for on-line purging for purging liquid steel during tapping and
transfer to LHF as claimed in claim 6 wherein said control panel comprise
visual indication for purging cycle ON/OFF condition for safety during coupling
and decoupling operations.
8. A system for on-line purging for purging liquid steel during tapping and
transfer to LHF as claimed in anyone of claims 1 to 7 wherein the
instrumentation means selectively comprise pressure regulator, solenoid
valves isolation valves rotameter, and pressure gauge.
13

9. A method of on-line purging of liquid steel during tapping and transfer till the
position of decoupling before lifting the ladle for treatment in LHF using the
system as claimed in anyone of claims 1 to 8 comprising:
a. positioning the ladle for the purging treatment; and
b. selectively treating the liquid steel with Argon gas purging at a
pressure of 6-8 Kg/Cm2 with a flow rate of 200-400 LPM through ladle
bottom, followed by aluminum addition 0.6-1.3 Kg/t alongwith normal
ferro-alloys additions; and
c. turning off the purging gas preferably by shutting off the solenoid
valve before decoupling.
10. A method of on-line purging of liquid steel as claimed in claim 9 wherein the
portion of the pipeline after the solenoid valve is de-pressurized before
decoupling preferably using separate solenoid valve for such purpose and
thereafter the ladle is lifted for further treatment in LHF.
11. A system for on-line purging for purging liquid steel during tapping, and
transfer to LHF and a method of on-line purging for purging liquid steel
during tapping and transfer to LHF using the same substantially as
hereindescribed and illustrated with reference to the accompanying
illustrations and figures.

Dated this 29th day of February,2008
14

A system for Online Purging (OLP) of Argon gas during tapping of liquid metal and transfer
to LHF, to enhance mixing of ferro-alloys during tapping and to counter the effect of
thermal stratification ensuring homogeneous composition of molten steel sent for
continuous casting. The purging process during tapping using the system, Argon gas is
bubbled in to the bath of liquid steel to generate enough bath turbulence resulting thermal
and chemical homogeneity in liquid metal, wherein process parameters comprising
selective argon pressure, flow rate and duration. The method used in OLP system involves
aluminium addition selectively in the range of 0.6-1.3 Kg/t in addition to normal addition
of Ferrosilicon and Silico-manganese for favored improved refining in LHF, lower level of
dissolved oxygen at the beginning of LHF refining, favored lower percent of heats with
lower oxygen content , enabling faster, improved refining of steel in LHF , improved
recovery of ferro-alloys and reduced consumption of aluminium and Si-Mn per ton of
molten steel sent to caster, thus economizing cost of inputs.