FIELD OF THE INVENTION
The present invention relates to a system for control of argon flow through mono-block
stopper in tundish for continuous casting of bloom to eliminate clogging of sub-entry
nozzle (SEN). More particularly, the present invention is directed to a system and method
for achieving flow control for argon gas purging through monoblock stopper of tundish to
favour eliminating dogging of SEN in continuous bloom caster due to deposition of solid
inclusions in steel at the steel making temperature. Advantageously, the present system
and method of controlled argon flow facilitate ceaseless production of value added
aluminium killed steel in continuous caster without any human intervention. Importantly,
the system for controlled argon flow/pressure control to avoid SEN clogging is direceted to
ensure continuous production in bloom caster without interruption due to SEN clogging,
improved quality of steel at lower cost of production making such system SUitable for wide
industrial application.
BACKGROUND ART
It is commonly experienced in the existing art of continuous steel casting that sub-entry
nozzle (SEN) suffers from the problem of clogging for flow of molten metal from tundish to
mould while casting aluminum /aluminum-silicon killed steel. This lead to decreased
productivity, increased cost and low machine availability. Clogging of sub-entry nozzle
usually takes place due to deposition of solid inclusion of Ah03/AI20rMgO-Si02/ CaO-Ah03
or CaS in case of Ca-treated steel, as these types of inclusions are solid at steel making
temperature. Vacuum treated steel is more prone to clogging due to formation of AbOr
MgO-Si02 spinal in magnesia refractory ladle. Improved steel making practice can reduce
nozzle clogging to a large extent. However, it is extremely difficult to control reoxidation of
aluminum in steel, which lead to SEN clogging. In addition to improved steel making
practice, following different methods are used to control/eliminate SENclogging:
(i) Argon purging through mono-block stopper/ Slide-gate;
(ii) Using Anti-clogging refractory for SEN;
(ii) Special designed contour (step design) of SEN;

The most effective and frequently applied technique to avoid (SEN)nozzle clogging is
Argon purging through mono-block stopper in tundish. Argon forms a thin layer in
refractory surface and thereby, does not allow any deposition to take place. It flushes out
any deposits in case of deposition of inclusion. However, control of argon flow and
pressure shall be done accurately which is extremely important in bloom caster as
compared to slab caster as it can lead to other problems like meniscus freezing, powder
entrapments, and argon entrapments in solidifying shell and in extreme situation may
cause breakouts. All these happen mainly due to smaller size of the product(e.g. Bloom)
as compared to slab caster and use of bifurcated nozzle for slab casting; whereas, bloom
casters uses straight bore nozzle. In addition, nozzle clogging is more in bloom caster due
to low throughput as well as smaller SENbore diameter.
A four-strand high-speed bloom caster for production of semi-killed (Si-Mn killed)
low/medium carbon ordinary grades commissioned in one of the large integrated steel
plants of the applicants suffered problems of nozzle clogging while casting bloom product
of special grade steel in continuous caster. The size of the blooms produced having the
dimensions in the range of 210-350mmX160mm and 200mmX200mm. Dissolved oxygen
content of the steel of these grades of castings is in the range of 30-70ppm. Cast ability of
these grades is good with respect to nozzle clogging although stopper head erosion is
considerably high due to very high oxygen in steel. Attempts have been made to produce
aluminium killed value added special quality grades. But, the desired result could not be
achieved due to SEN clogging in absence of a system for precise control of flow of argon
through stopper rods.
There has thus been a persistent need in the art of continuous casting of blooms to
developing a system for accurate pressure as well as flow control of argon gas in argon
purging system through mono-block stopper, that is adapted for four strand bloom caster
configured to be fed through two tundishes. The argon purging system is designed,
fabricated and installed in bloom caster to produce special quality blooms completely
eliminating SEN clogging. The system and method for continuous bloom casting in the
continuous casters as of the present invention on one hand would provide uninterrupted
production with higher productivity and yield, avoiding operational problems like meniscus
freezing and breakouts without human intervention and on the other hand improve plant
availability and quality of castings reducing waste of castings and resultantly the cost of
production. The unique configuration of sets of valves, regulators and rotameters of

variety of precIsion and construction ensure the performance reliability of the argon
purging system according to the invention to provide precise control of flow and pressure
of argon without any humane intervention favoring large-scale industrial application in
steel plants.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to prOVidea system for precise control
of pressure and flow of argon purging through mono~block stopper of tundish for
eliminating clogging of the sub-entry nozzle(SEN) for passage of liquid metal from tundish
to mold for continuous bloom caster to produce special quality blooms without any
interruption even when the pressure varies in the inlet header of the argon gas, without
any human intervention.
A further object of the present invention is directed to a system for precise and controlled
pressure and flow of argon purging for eliminating clogging of SEN from tundish to mold
for continuous bloom casting wherein said system comprised valves of different precision
and construction, pressure regulator of high precision and required through put, DP
regulator with appropriate range, pressure drop etc., rotameter of desired accuracy for
flow measurement, high precision pressure gauges, pipes, hoses, and other fittings
adapted to control accurately the pressure and the flow rate of argon for continuous
purging at constant volume and pressure, installed with minimum space requirements.
A still further object of the present invention is directed to a system for precise and
controlled pressure and flow of argon purging for eliminating clogging of SENfrom tundish
to mold suitable for casting of value added aluminum killed steel at lower cost.
A still further object of the present invention is directed to a system for precise and
controlled pressure and flow of argon purging for eliminating clogging of SEN in continuous
bloom caster directed to avoid air ingress during transfer of metal from Tundish to Mould.

A still further object of the present invention is directed to a system for precise and
controlled pressure and flow of argon purging for eliminating clogging of SEN in continuous
bloom caster adapted to solve problems relating to meniscus freezing, powder
entrapments, and argon entrapments in solidifying shell and breakouts under extreme
situation.
A still further object of the present invention is directed to a system for precise and
controlled pressure and flow of argon purging for eliminating clogging of SEN in continuous
bloom caster adapted to produce high quality blooms from aluminium killed steel with
higher machine availability, improved productivity and yield, reduced rejection and thus
reducing the cost of production.
A still further object of the present invention is directed to a system for precise and
controlled pressure and flow of argon purging for eliminating clogging of SEN in continuous
bloom caster using straight bore nozzle subjected to clogging due to low throughput as
well as smaller SEN bore diameter.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is prOVidedan argon
purging system through mono-block stopper of tundish comprising:
means for supply of Argon gas through the said stopper rod;
a pressure regulator means operatively connected adapted to control any variation at the
inlet header of the Argon gas;
a flow measurement rotameter adapted for controlled flow of Argon gas at required set
values.
A further aspect of the present invention is directed to said argon purging system,
comprising
mono-block stopper through which the constant flow of argon is carried to SEN;

argon gas manifold receiving gas supply from an inlet header through isolating ball valve
and a high precision argon pressure regulator adapted to maintain constant supply
pressure and flow of argon even with variation in inlet gas pressure at header;
a distribution manifold connected to said argon gas inlet manifold by means of flexible
hose and suitable connector/fittings;
said distribution manifold having said rotameter with inbuiltadjustable valve as well as DP
regulator of proper range! pressure drop selectively disposed, adapted to supply controlled
measured constant argon gas flow rate at required set value to SEN through each said
mono-bock stopper, in case of variation of pressure from any side;
flexible hose connection through quick release coupling and flow adjusting needle valve
allowing the flow of argon gas at desired constant pressure and volume flow rate through
the central bore of said monoblock stopper for each of the respective SEN installed in
preferred numbers in a tundish, to thereby completely eliminating SENclogging.
A still further aspect of the present Invention is directed to said argon purging system,
wherein said precise control of pressure as well as flow of argon gas through mono-block
stopper of tundish is automatised.
A still further aspect of the present invention is directed to said argon purging system
comprising said pressure and flow control system for a four strand bloom caster having
two tundish cars comprised instrumentation for desired precise control of pressure and
flow of argon gas involving two pressure regulators, two numbers precision pressure
gauges, eight numbers rota meters, eight numbers DP regulators and necessary pipe,
flexible hose and other fittings, selectively disposed in argon inlet and distribution
manifold connecting between the argon inlet header to the respective SEN in a tundish
through the mono-block stopper.
According to yet another aspect of the present invention is directed to said argon purging
system for continuous bloom caster wherein said sub entry nozzle(SEN) is a straight
stepless nozzle with smaller SEN bore diameter having low through put for bloom casting.
6
Yet another aspect of the present invention is directed to a method for achieving precisely
controlled constant pressure and flow for argon purging of SEN during continuous casting
of bloom from aluminium killed special grade of steel using said argon puging system of
the invention, comprising the steps of
providing constant argon gas pressure and volume flow from the inlet header
through and by means of a high precision pressure regulator even when the inlet
header pressure variation is present or variation in molten metal level in mold
exist;
providing the desired supply argon gas pressure measured by said precision
pressure gauge;
providing controlled flow of argon to the required set value measured and
controlled by a rotameter with DP regulator of proper range and inbuilt adjuster
valve, sent through the central core of each mono-block stopper, in case of
variation of pressure from any side;
providing precisely measured and controlled constant pressure and flow of argon
gas through SENto thereby laying a thin continuous film of argon gas on refractory
surface of SEN such as not to allow any solid inclusion in melt to deposit on nozzle
surface to thereby completely eliminate clogging during continuous bloom casting
and also avoiding the problems relating to air ingress during metal transfer from
tundish to mold, meniscus freezing, entrapments in solidifying shell and breakout.
molten steel flow through Nozzle of Tundish being controlled by using said stopper
rod by changing diameter of clear space at the mouth of nozzle hole, by modulating
stopper rod's position according to molten steel level at Mould to achieve desired
quality of bloom casting free of entrapments/defects.
The present invention and its objectives and advantages are described in greater details
with reference to the folloWing non limiting illustrative embodiment of Figure 1.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE
Figure 1: is the schematic illustration an embodiment of the system for precisely
controlled argon flow according to the present invention for four-strand bloom caster
haVing two tundish cars, directed to eliminate clogging of SEN, showing the location of the
control instrumentation in the network of piping for constantly controlled pressure and
volume flow rate of argon through the mono-block stopper rods of tundish.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURE:
The present invention is directed to a system for argon purging through mono-block
stopper which is configured, fabricated and installed in bloom caster to produce special
quality blooms and to eliminate SENclogging completely, without any human intervention.
Such a system is able to improve quality and productivity of bloom caster with reliability
and without interruption and is also able to avoid conventional operational problems argon
purging based nozzle cleaning systems like meniscus freeZing and breakouts. The argon
purging system according to the invention is adapted to precisely control flow and
pressure of argon to avoid choking/clogging of nozzle hole by purging of Argon Gas at
constant volume and pressure that is required even in case of variation of input Argon gas
pressure as well as variation of molten metal level inside the mould.
Reference is now invited to the accompanying Figure 1 that schematically illustrate a
system of argon gas purging through mono-block stopper for eliminating clogging of SEN
from tundish to mold using selective deployment of control instrumentation and measuring
instruments as well as the distribution manifold comprising pipes, hose and other fittings.
It may be noted that for such argon purging system, constant purging means constant
flow of Argon gas through the center hole of Stopper Rod at constant pressure. This argon
gas flow at selective pressure and volume flow rate is directed to reach inside liquid steel
at mould along with liquid steel through the hollow space of nozzle and bubbling out
through the top surface of liquid steel inside the Mould. Stopper Rod is used by convention
to control desired flow of molten steel through Nozzle of Tundish by changing diameter of
clear space at the mouth of nozzle hole. This is carried out by adjusting the stopper rod's
position to required hole opening of the nozzle according to molten steel level at Mould in
order to maintain desired flow rate to mold during continuous casting of blooms/slabs.
Argon Gas purging at constant volume and pressure is essentially required in order to
avoid choking of Sub-entry Nozzle hole from tundish to mold, even in case of variation of
input Argon gas pressure as well as variation of molten metal level inside the mould.
The accompanying Figure 1 is a schematic illustration of an embodiment according to the
invention showing a system for argon purging for four strand bloom caster having two
tundishes in continuous bloom casting plant. The figure shows the arrangement/scheme of

control instrumentation and supply line corresponding to each such tundish with four
outlet/sub entry nozzles to molds.
It is clearly apparent from the accompanying Figure 1, that argon gas supply is received
from an inlet header through pipe line through a Ball Valve for isolation(BV) and an argon
Pressure Regulator(PR) to the supply manifold line from which argon is fed through the
Stopper Rods(SR) to the different SEN mounted in a tundish(TD). The argon pressure
regulator(PR) is a high precision regulator, configured to precisely and accurately control
the required throughput to the system, even in case the flow of argon is subjected to
variation consequent upon any variation in pressure at the inlet header of argon gas,
without any human intervention. The line pressure is accurately measured by means of a
Pressure Gauge(PG) of ± 0.5% accuracy in order to maintain the supply pressure of the
argon gas for purging in the constant operating pressure range of 0 to 6 k9,fcrrf" .The inlet
argon supply pipe line from the header is connected to the distribution pipe line through a
flexible hose and suitable connectors. The argon distribution line is equipped with four
numbers of Rotameter with DP(differential pressure) regulator(RDP) and inbuilt needle
valve, adapted to sense very minute pressure drop and precislely controls the desire
constant volume flow rate of argon in the operating range of 0 to 10 I/min with an
accuracy of ± 1.0 % by said rotameter. Each of the Rotameter with DP regulator(RDP) is
connected to each of said four numbers stopper rods' central bore through which the gas
flows to the nozzle and to the molten steel metal in mold and has been used to get
controlled flow at required set value in the case of variation of pressure from any side.
The argon gas supply line to each of the stopper rod(SR) central bore from the outlet of
Rotameter with DP Regulator(RDP) is connected by means of flexible hose through a Quick
release Coupling(QRC) and a Needle Valve for flow adjustment(NDV). The Quick Release
coupling (QRC) is adapted to favor easy and fast detachability for alternate supply to other
tundish in the four strand caster with two tundishes(TD) for successive batches of bloom
casting in the continuous caster. The needle valves precisely maintain the pressure at the
entry of stopper and SENto desired level to favor eliminating nozzle clogging. The present
system for precise argon purging for elimination of nozzle clogging in continuous bloom
caster is thus a reliable and low cost solution requiring less space for its installation and
enable continuous production of special quality value added aluminium killed steel blooms,
without the operational problems of meniscus freezing or breakouts. The precise control on
constant flow and pressure of argon gas flow also favor avoiding air ingress during transfer

of metal from tundish to mold. The system and method of controlled flow of argon at
constant pressure thus helps eliminating the limitations in continuous bloom casting due to
low throughput and use of straight bore stepless nozzle having relatively smaller SEN
diameter making the process prone to nozzle clogging. The system and method of
precisely controlled argon gas purging through the central hole of the mono-block stopper
for adjustment of nozzle hole opening favor forming desired continuous argon film/layer on
the refractory surface of the nozzle to thereby avoiding deposition of any undesired
inclusion on nozzle surface from molten steel leading to clogging.
It is thus possible by way of the present invention to developing a system for precisely
controlled and accurately measured desired constant pressure and volume flow rate for
argon purging through the mono-block stopper in continuous bloom casting, in spite of
variation in inlet header pressure of argon gas, for achieving complete elimination of
nozzle clogging even with straight narrow bore SEN, without any human intervention. The
system and method of the present invention further facilitates eliminating problems
relating to meniscus freezing, powder/argon entrapments in solidifying shells or breakouts,
avoiding air ingress during transfer of metal from the tundish to mold, ensuring
uninterrupted production of special quality value added aluminium killed or other grades
of steel, with higher productiVity, low cost, needing less space for installation of such
systems and thus favoring wide scale industrial application in continuous caster plants.
1. An argon purging system through mono-block stopper of tundish comprising:
means for supply of Argon gas through the said stopper rod;
a pressure regulator means operatively connected adapted to control any variation at the
inlet header of the Argon gas;
a flow measurement rotameter adapted for controlled flow of Argon gas at required set
values.
2. A system as claimed in claim 1 comprising
mono-block stopper through which the constant flow of argon is carried to SEN;
argon gas manifold receiving gas supply from an inlet header through isolating ball valve
and a high precision argon pressure regulator adapted to maintain constant supply
pressure and flow of argon even with variation in inlet gas pressure at header;
a distribution manifold connected to said argon gas inlet manifold by means of flexible
hose and suitable connector/fittings;
said distribution manifold having said rotameter with inbuilt adjustable valve as well as DP
regulator of proper range/ pressure drop selectively disposed, adapted to supply controlled
measured constant argon gas flow rate at required set value to SEN through each said
mono-bock stopper, in case of variation of pressure from any side;
flexible hose connection through qUick release coupling and flow adjusting needle valve
allowing the flow of argon gas at desired constant pressure and volume flow rate through
the central bore of said monoblock stopper for each of the respective SEN installed in
preferred numbers in a tundish, to thereby eliminating SENclogging.

3. A system as claimed in anyone of claims 1 or 2, wherein said precise control of pressure
as well as flow of argon gas through mono-block stopper of tundish is automatised.
4. A system as claimed in anyone of claims 1 to 3 comprising said pressure and flow
control system for a four strand bloom caster having two tundish cars comprised
instrumentation for desired precise control of pressure and flow of argon gas involving two
pressure regulators, two numbers precision pressure gauges, eight numbers rotameters,
eight numbers DP regulators and necessary pipe, flexible hose and other fittings,
selectively disposed in argon inlet and distribution manifold connecting between the argon
inlet header to the respective SENin a tundish through the mono-block stopper.
5. A system as claimed in anyone of claims 1 to 4 wherein said sub entry nozzle(SEN) is a
straight stepless nozzle with smaller SEN bore diameter and low through put for bloom
casting.
6. A method for achieving precisely controlled constant pressure and flow for argon
purging of SEN during continuous casting of bloom aluminium killed special grade of steel
using the system as claimed in claims 1 to 5, comprising the steps of
providing constant argon gas pressure and volume flow from the inlet header
through and by means of a high precision pressure regulator even when the inlet
header pressure variation is present or variation in molten metal level in mold
eXist;
providing the desired supply argon gas pressure measured by said precision
pressure gauge;
providing controlled flow of argon to the required set value measured and
controlled by a rotameter with DP regulator of proper range and inbuilt adjuster
valve, sent through the central core of each mono-block stopper, in case of
variation of pressure from any side;
providing precisely measured and controlled constant pressure and flow of argon
gas through SENto thereby laying a thin continuous film of argon gas on refractory
surface of SENsuch as not to allow any solid inclusion in melt to deposit on nozzle
surface to thereby completely eliminate clogging during continuous bloom casting
and also avoiding the problems relating to air ingress during metal transfer from
tundish to mold, meniscus freezing, entrapments in solidifying shell and breakout.

molten steel flow through Nozzle of Tundish being controlled by using said stopper
rod by changing diameter of clear space at the mouth of nozzle hole, by modulating
stopper rod's position according to molten steel level at Mould to achieve desired
quality of bloom casting free of entrapments/defects.
7. A system for precise pressure and flow control for argon purging of Sub-entry nozzle
(SEN) from tundish to mold adapted to eliminate clogging in continuous bloom caster and
a method for such casting as hereindescribed with reference to the accompanying non
limiting illustrative embodiments.