Title of Invention	SYSTEM FOR DETERMINING THE EFFECTIVENESS OF A SHROUD IN TUNDISH STREAM DURING CONTINUOUS CASTING OF STEEL SO AS TO PREVENT UNDESIRED OXYGEN INTAKE FROM ATMOSPHERE.
Abstract	System for detemriining the effectiveness of a shroud in tundish stream during continuous casting of steel so as to prevent undesired oxygen intake from atmosphere is provided for all types of gas shrouds e.g., Can, Pollard and Ring shrouds as well as all mechanical shrouds. The system may be used for tundish nozzles of different diameters and also for varying lengths of the stream. The system provides a simple and inexpensive method of detemining the effectiveness of shrouds. The system comprises an upper tank (1) for holding liquid and having a nozzle (2) at the bottom for the outflow of the liquid contained therein, the shroud (15) placed below the nozzle (2) to receive liquid from the upper tank (1) and prevent intake of oxygen by the liquid from the atmosphere, a bottom tank (3) having a gas collection unit (6) for receiving liquid stream from the upper tank (1) through the shroud (15), The gas collection unit (6) is operatively connected to an oxygen meter (11) which measures the amount of oxygen in the said liquid. The shroud efficiency is determined based on the amounts of total gas and oxygen in the liquid.

Title of Invention

SYSTEM FOR DETERMINING THE EFFECTIVENESS OF A SHROUD IN TUNDISH STREAM DURING CONTINUOUS CASTING OF STEEL SO AS TO PREVENT UNDESIRED OXYGEN INTAKE FROM ATMOSPHERE.

Abstract

System for detemriining the effectiveness of a shroud in tundish stream during continuous casting of steel so as to prevent undesired oxygen intake from atmosphere is provided for all types of gas shrouds e.g., Can, Pollard and Ring shrouds as well as all mechanical shrouds. The system may be used for tundish nozzles of different diameters and also for varying lengths of the stream. The system provides a simple and inexpensive method of detemining the effectiveness of shrouds. The system comprises an upper tank (1) for holding liquid and having a nozzle (2) at the bottom for the outflow of the liquid contained therein, the shroud (15) placed below the nozzle (2) to receive liquid from the upper tank (1) and prevent intake of oxygen by the liquid from the atmosphere, a bottom tank (3) having a gas collection unit (6) for receiving liquid stream from the upper tank (1) through the shroud (15), The gas collection unit (6) is operatively connected to an oxygen meter (11) which measures the amount of oxygen in the said liquid. The shroud efficiency is determined based on the amounts of total gas and oxygen in the liquid.

Full Text	Field of Invention The present invention relates to a system for measurement of effectiveness of shrouding in tundish stream during continuous casting of steel so as to prevent undesired oxygen intake from atmosphere. Background of the invention During continuous casting of steel, the liquid steel is tapped from the ladle into a tundish. From the tundish, steel stream falls through a nozzle and finally enters the mould. This steel stream during casting operation, picks up oxygen from the atmosphere resulting in reoxidation of the steel and nullifying considerably the effect of deoxidation upstream In order to reduce the oxidation of the steel stream coming out of the tundish, suitable shroud systems are introduced. Both mechanical and gas shrouding systems are in vogue. These help in reduction of reoxidation of steel and in improving the quality of steel by lowering non-metallic inclusion. Shrouds also help in improving sequence length of casting Shroud systems like Can shroud, Potlard shroud, Ring shroud and Bellow shroud are commonly used. Each shroud system has its own merits and demerits. For example, Ring shroud is cheap and easy to use while Bellow shroud is difficult to operate. On the other hand, Bellow shroud requires very little inert gas compared to a Ring shroud while the gas requirement of a Pollard shroud is intermediate. These different shroud systems have to be carefully studied keeping in mind the logistics of the shop and the cleanliness requirement of the final steel Presently, no standard technique to measure the effectiveness of shrouding is known other than to measure the cleanliness of steel by looking at the microstructure of the cast steel The drawback of this technique is that one does not actually know the exact location where the oxygen was picked up. The other method is to actually measure oxygen of liquid steel at various places. This method is not only cumbersome but also expensive. 2 Objects of the invention Therefore the primary object of the present invention is to provide a system for measuring the effectiveness of a shroud in cutting down oxygen pick-up Another object of the present invention is to provide a system which is simple and economic and provides a less cumbersome method for measuring the effectiveness of shrouding. Summary of the invention Accordingly the present invention relates to a system for determining the effectiveness of a shroud in tundish stream during continuous casting of steel so as to prevent undesired oxygen intake from atmosphere, the system comprising: an upper tank for holding liquid and having a nozzle at the bottom for the outflow of the liquid contained therein; a shroud placed below said nozzle in liquid communication to receive liquid from the upper tank and prevent intake of oxygen by the liquid from the atmosphere; a bottom tank having a gas collection unit for receiving liquid stream from the upper tank through the shroud, said gas collection unit being operatively connected to an oxygen meter which measures the amount of oxygen in the said liquid; and means for determining the shroud efficiency based on the amounts of total gas and oxygen in said liquid. Detailed description of the invention The system of the present invention is a water model that measures effectiveness of shrouding. In the system the Reynolds number of the liquid metal stream leaving through the nozzle of the tundish is simulated so as to keep the flow characteristics of water stream in the system similar to that of actual liquid metal flowing from tundish to mould. The amount of oxygen pick-up is measured by a gas collection unit and an oxygen meter 3 The system comprises an upper tank having a nozzle at the bottom, a bottom tank having a gas collection unit for receiving liquid stream from the upper tank and shrouding means placed below the nozzle at the bottom of the upper tank wherein the gas collection unit is operatively connected to an oxygen meter. The gas collection unit preferably comprises a U-tube and an Inverted container, preferably a bell jar. The gas collection means is preferably connected to oxygen meter by a tube having at least one needle valve. The system also comprises means to create vacuum in the inverted container. Preferably a vacuum pump is used for the purpose. The vacuum pump may be connected to the inverted container through an overflow water collector to collect any excess water that may be drawn while creating vacuum in the inverted container. The shrouding means is connected to an inert gas source. If the operative gas used Is argon then the shroud is connected to an argon gas cylinder. A rotameter may be present in between the shroud and the gas source for measuring the gas flow rate. The system of the invention will now be described with respect to a preferred embodiment and accompanying drawings in which figure 1 shows a schematic drawing of the system of the present invention and figure 2 shows a graph of the efficiency of shroud for different gas flow rates. Description of the preferred embodiment The system illustrated measures effectiveness of argon shrouding. The system is fabricated using 8 mm Perspex sheet. The main components of the system are a upper tank or tundish (1) with nozzle (2) at the bottom. The bottom tank (3) is placed below the tundish representing mould. The tank has a gas collection unit (4) which comprises a U tube (5) and an inverted bell jar (6) for gas collection with a top outlet (7). The bell jar has a Perspex tube (8) with a needle valve (9) at the top. The upper end of the Perspex tube is connected to an overflow water collector (10) and also to an oxygen meter (11) through a needle valve (12). The overflow collector is connected to a vacuum pump (13) through a valve (14). 4 The shroud (15) is placed below the nozzle of the tundish in the path of the water stream. The shroud (15) is connected to argon gas cylinders (17) via a rotameter (16). Method of measurement of effectiveness of shrouding Water is first filled in the upper tank or tundish (1) which has nozzle (2) at the bottom. The nozzle is kept closed while water is being filled. Height of water filled in the tundish depends on the diameter of the nozzle so that the water coming out of the nozzle will have the same Reynolds number as the steel stream coming out of the tundish nozzle in actual steel plant in practice. This is necessary so as to keep the flow characteristics of the water and the steel same. The height of the water in the upper tank is kept fixed throughout with the help of a pump. The lower tank (3) which resembles the mould is also filled with water to a level so that the bottom of the inverted bell jar (6) is below the water level in the tank (3). At the beginning of the measurement procedure, the needle valve (9) above the bell jar is kept open and the valve connected to the oxygen meter (12) is kept closed. The vacuum pump (13) is then started. Water from the lower tank (3) is sucked into the bell jar (6) till it is completely filled At this point the needle valve (9) above the bell jar is closed and the vacuum pump (13) is shut off. The valve (12) in front of oxygen meter is opened and the valve (14) connecting the over flow water collector is closed. The shroud (15) is then placed below the tundish nozzle (2) and its distance from the mould measured. Argon gas is allowed to flow to the shroud and the gas flow rate is noted in the rotameter (16) The nozzle IS opened and the water stream starts flowing into the mould. The gas that is picked up by the stream is directed to the bell jar using the U-tube The gas is collected in the bell jar. The oxygen of the collected gas in the bell jar is measured by the oxygen meter. A low percentage of oxygen in the collected gas indicates better shrouding. The amount of air entrapped is known from the percentage oxygen in the gas and the volume of the collected gas. The following calculations are carried out to measure the shrouding efficiency. Let Vi = Initial amount of gas present in bell jar Let Vf = Final volume of total gas in the bell jar 5 ) The system as described above was used to measure the shroud efficiency at different argon slow rates and the results have been plotted in a graph shown in figure 2. The procedure was carried out for shroud to mould distance of 0 cm and 2 cm Advantages of the present invention The shroud efficiency measurement system of the invention may be used for measuring effectives of all types of gas shrouds e.g., Can, Pollard and Ring shrouds as well as all mechanical shrouds. The system may be used for tundish nozzles of different diameters and also for varying lengths of the stream. The system provides a simple and inexpensive method of testing of the effectiveness of shrouds. 6 We claim A system for determining the effectiveness of a shroud in tundish stream during continuous casting of steel so as to prevent undesired oxygen intake from atmosphere, the system comprising: an upper tank for holding liquid and having a nozzle at the bottom for the outflow of the liquid contained therein; a shroud placed below said nozzle in liquid communication to receive liquid from the upper tank and prevent intake of oxygen by the liquid from the atmosphere; a bottom tank having a gas collection unit for receiving liquid stream from the upper tank through the shroud, said gas collection unit being operatively connected to an oxygen meter which measures the amount of oxygen in the said liquid; and means for determining the shroud efficiency based on the amounts of total gas and oxygen in said liquid. A system as claimed in claim 1, wherein said liquid is water. A system as claimed in claim 1, wherein said gas collection unit comprises a U-tube and an inverted container. A system as claimed in claim 3, wherein said container Is a Perspex bell jar. A system as claimed in claim 1, wherein said gas collection means is connected to oxygen meter by a tube having at least one needle valve. A system as claimed in claim 5, wherein said tube is Perspex tube. A system as claimed in any of the preceding claims, comprising means for creating vacuum operatively connected to said inverted container. A system as claimed in claim 7, wherein said means for creating vacuum is a vacuum pump. 7 9. A system as claimed in any of the preceding claims, wherein said means for creating vacuum is operatively connected to said inverted container via an overflow water collector. 10.A system as claimed in any of the preceding claims, wherein said shrouding means is operatively connected to inert gas source. 11. A system as claimed in any of the preceding claims, wherein said shrouding means is operatively connected to inert gas source via means for measuring the gas flow rate. 12. A system as claimed in any of the preceding claims, wherein said means for measuring gas flow rate is a rotameter. 13. A system as claimed in any of the preceding claims, wherein said inert gas is argon. System for detemriining the effectiveness of a shroud in tundish stream during continuous casting of steel so as to prevent undesired oxygen intake from atmosphere is provided for all types of gas shrouds e.g., Can, Pollard and Ring shrouds as well as all mechanical shrouds. The system may be used for tundish nozzles of different diameters and also for varying lengths of the stream. The system provides a simple and inexpensive method of detemining the effectiveness of shrouds. The system comprises an upper tank (1) for holding liquid and having a nozzle (2) at the bottom for the outflow of the liquid contained therein, the shroud (15) placed below the nozzle (2) to receive liquid from the upper tank (1) and prevent intake of oxygen by the liquid from the atmosphere, a bottom tank (3) having a gas collection unit (6) for receiving liquid stream from the upper tank (1) through the shroud (15), The gas collection unit (6) is operatively connected to an oxygen meter (11) which measures the amount of oxygen in the said liquid. The shroud efficiency is determined based on the amounts of total gas and oxygen in the liquid.

Full Text

Field of Invention
The present invention relates to a system for measurement of effectiveness of shrouding in tundish stream during continuous casting of steel so as to prevent undesired oxygen intake from atmosphere.
Background of the invention
During continuous casting of steel, the liquid steel is tapped from the ladle into a tundish. From the tundish, steel stream falls through a nozzle and finally enters the mould. This steel stream during casting operation, picks up oxygen from the atmosphere resulting in reoxidation of the steel and nullifying considerably the effect of deoxidation upstream In order to reduce the oxidation of the steel stream coming out of the tundish, suitable shroud systems are introduced. Both mechanical and gas shrouding systems are in vogue. These help in reduction of reoxidation of steel and in improving the quality of steel by lowering non-metallic inclusion. Shrouds also help in improving sequence length of casting
Shroud systems like Can shroud, Potlard shroud, Ring shroud and Bellow shroud are commonly used. Each shroud system has its own merits and demerits. For example, Ring shroud is cheap and easy to use while Bellow shroud is difficult to operate. On the other hand, Bellow shroud requires very little inert gas compared to a Ring shroud while the gas requirement of a Pollard shroud is intermediate.
These different shroud systems have to be carefully studied keeping in mind the logistics of the shop and the cleanliness requirement of the final steel
Presently, no standard technique to measure the effectiveness of shrouding is known other than to measure the cleanliness of steel by looking at the microstructure of the cast steel The drawback of this technique is that one does not actually know the exact location where the oxygen was picked up. The other method is to actually measure oxygen of liquid steel at various places. This method is not only cumbersome but also expensive.
2
Objects of the invention
Therefore the primary object of the present invention is to provide a system for measuring the effectiveness of a shroud in cutting down oxygen pick-up
Another object of the present invention is to provide a system which is simple and economic and provides a less cumbersome method for measuring the effectiveness of shrouding.
Summary of the invention
Accordingly the present invention relates to a system for determining the effectiveness of a shroud in tundish stream during continuous casting of steel so as to prevent undesired oxygen intake from atmosphere, the system comprising:
an upper tank for holding liquid and having a nozzle at the bottom for the outflow
of the liquid contained therein;
a shroud placed below said nozzle in liquid communication to receive liquid from
the upper tank and prevent intake of oxygen by the liquid from the atmosphere;
a bottom tank having a gas collection unit for receiving liquid stream from the
upper tank through the shroud, said gas collection unit being operatively
connected to an oxygen meter which measures the amount of oxygen in the said
liquid; and
means for determining the shroud efficiency based on the amounts of total gas
and oxygen in said liquid.
Detailed description of the invention
The system of the present invention is a water model that measures effectiveness of shrouding. In the system the Reynolds number of the liquid metal stream leaving through the nozzle of the tundish is simulated so as to keep the flow characteristics of water stream in the system similar to that of actual liquid metal flowing from tundish to mould. The amount of oxygen pick-up is measured by a gas collection unit and an oxygen meter
3
The system comprises an upper tank having a nozzle at the bottom, a bottom tank having a gas collection unit for receiving liquid stream from the upper tank and shrouding means placed below the nozzle at the bottom of the upper tank wherein the gas collection unit is operatively connected to an oxygen meter.
The gas collection unit preferably comprises a U-tube and an Inverted container, preferably a bell jar. The gas collection means is preferably connected to oxygen meter by a tube having at least one needle valve. The system also comprises means to create vacuum in the inverted container. Preferably a vacuum pump is used for the purpose. The vacuum pump may be connected to the inverted container through an overflow water collector to collect any excess water that may be drawn while creating vacuum in the inverted container.
The shrouding means is connected to an inert gas source. If the operative gas used Is argon then the shroud is connected to an argon gas cylinder. A rotameter may be present in between the shroud and the gas source for measuring the gas flow rate.
The system of the invention will now be described with respect to a preferred embodiment and accompanying drawings in which figure 1 shows a schematic drawing of the system of the present invention and figure 2 shows a graph of the efficiency of shroud for different gas flow rates.
Description of the preferred embodiment
The system illustrated measures effectiveness of argon shrouding. The system is fabricated using 8 mm Perspex sheet. The main components of the system are a upper tank or tundish (1) with nozzle (2) at the bottom. The bottom tank (3) is placed below the tundish representing mould. The tank has a gas collection unit (4) which comprises a U tube (5) and an inverted bell jar (6) for gas collection with a top outlet (7). The bell jar has a Perspex tube (8) with a needle valve (9) at the top. The upper end of the Perspex tube is connected to an overflow water collector (10) and also to an oxygen meter (11) through a needle valve (12). The overflow collector is connected to a vacuum pump (13) through a valve (14).
4
The shroud (15) is placed below the nozzle of the tundish in the path of the water stream. The shroud (15) is connected to argon gas cylinders (17) via a rotameter (16).
Method of measurement of effectiveness of shrouding
Water is first filled in the upper tank or tundish (1) which has nozzle (2) at the bottom. The nozzle is kept closed while water is being filled. Height of water filled in the tundish depends on the diameter of the nozzle so that the water coming out of the nozzle will have the same Reynolds number as the steel stream coming out of the tundish nozzle in actual steel plant in practice. This is necessary so as to keep the flow characteristics of the water and the steel same. The height of the water in the upper tank is kept fixed throughout with the help of a pump.
The lower tank (3) which resembles the mould is also filled with water to a level so that the bottom of the inverted bell jar (6) is below the water level in the tank (3). At the beginning of the measurement procedure, the needle valve (9) above the bell jar is kept open and the valve connected to the oxygen meter (12) is kept closed. The vacuum pump (13) is then started. Water from the lower tank (3) is sucked into the bell jar (6) till it is completely filled At this point the needle valve (9) above the bell jar is closed and the vacuum pump (13) is shut off. The valve (12) in front of oxygen meter is opened and the valve (14) connecting the over flow water collector is closed. The shroud (15) is then placed below the tundish nozzle (2) and its distance from the mould measured. Argon gas is allowed to flow to the shroud and the gas flow rate is noted in the rotameter (16) The nozzle IS opened and the water stream starts flowing into the mould. The gas that is picked up by the stream is directed to the bell jar using the U-tube The gas is collected in the bell jar. The oxygen of the collected gas in the bell jar is measured by the oxygen meter. A low percentage of oxygen in the collected gas indicates better shrouding. The amount of air entrapped is known from the percentage oxygen in the gas and the volume of the collected gas. The following calculations are carried out to measure the shrouding efficiency.
Let Vi = Initial amount of gas present in bell jar Let Vf = Final volume of total gas in the bell jar
5
)
The system as described above was used to measure the shroud efficiency at different argon slow rates and the results have been plotted in a graph shown in figure 2. The procedure was carried out for shroud to mould distance of 0 cm and 2 cm
Advantages of the present invention
The shroud efficiency measurement system of the invention may be used for measuring effectives of all types of gas shrouds e.g., Can, Pollard and Ring shrouds as well as all mechanical shrouds. The system may be used for tundish nozzles of different diameters and also for varying lengths of the stream. The system provides a simple and inexpensive method of testing of the effectiveness of shrouds.
6
We claim
A system for determining the effectiveness of a shroud in tundish stream during
continuous casting of steel so as to prevent undesired oxygen intake from atmosphere,
the system comprising:
an upper tank for holding liquid and having a nozzle at the bottom for the outflow of the
liquid contained therein;
a shroud placed below said nozzle in liquid communication to receive liquid from the
upper tank and prevent intake of oxygen by the liquid from the atmosphere;
a bottom tank having a gas collection unit for receiving liquid stream from the upper tank
through the shroud, said gas collection unit being operatively connected to an oxygen
meter which measures the amount of oxygen in the said liquid; and
means for determining the shroud efficiency based on the amounts of total gas and
oxygen in said liquid.
A system as claimed in claim 1, wherein said liquid is water.
A system as claimed in claim 1, wherein said gas collection unit comprises a U-tube and an inverted container.
A system as claimed in claim 3, wherein said container Is a Perspex bell jar.
A system as claimed in claim 1, wherein said gas collection means is connected to oxygen meter by a tube having at least one needle valve.
A system as claimed in claim 5, wherein said tube is Perspex tube.
A system as claimed in any of the preceding claims, comprising means for creating vacuum operatively connected to said inverted container.
A system as claimed in claim 7, wherein said means for creating vacuum is a vacuum pump.

7
9. A system as claimed in any of the preceding claims, wherein said means for creating vacuum is operatively connected to said inverted container via an overflow water collector.
10.A system as claimed in any of the preceding claims, wherein said shrouding means is operatively connected to inert gas source.
11. A system as claimed in any of the preceding claims, wherein said shrouding means is operatively connected to inert gas source via means for measuring the gas flow rate.
12. A system as claimed in any of the preceding claims, wherein said means for measuring gas flow rate is a rotameter.
13. A system as claimed in any of the preceding claims, wherein said inert gas is argon.
System for detemriining the effectiveness of a shroud in tundish stream during continuous casting of steel so as to prevent undesired oxygen intake from atmosphere is provided for all types of gas shrouds e.g., Can, Pollard and Ring shrouds as well as all mechanical shrouds. The system may be used for tundish nozzles of different diameters and also for varying lengths of the stream. The system provides a simple and inexpensive method of detemining the effectiveness of shrouds. The system comprises an upper tank (1) for holding liquid and having a nozzle (2) at the bottom for the outflow of the liquid contained therein, the shroud (15) placed below the nozzle (2) to receive liquid from the upper tank (1) and prevent intake of oxygen by the liquid from the atmosphere, a bottom tank (3) having a gas collection unit (6) for receiving liquid stream from the upper tank (1) through the shroud (15), The gas collection unit (6) is operatively connected to an oxygen meter (11) which measures the amount of oxygen in the said liquid. The shroud efficiency is determined based on the amounts of total gas and oxygen in the liquid.

Documents:

00562-kol-2003-abstract.pdf

00562-kol-2003-claims.pdf

00562-kol-2003-correspondence.pdf

00562-kol-2003-description(complete).pdf

00562-kol-2003-drawings.pdf

00562-kol-2003-form-1.pdf

00562-kol-2003-form-18.pdf

00562-kol-2003-form-2.pdf

00562-kol-2003-form-3.pdf

00562-kol-2003-letters patent.pdf

00562-kol-2003-p.a.pdf

00562-kol-2003-reply f.e.r.pdf

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Patent Number

206868

Indian Patent Application Number

562/KOL/2003

PG Journal Number

20/2007

Publication Date

18-May-2007

Grant Date

15-May-2007

Date of Filing

29-Oct-2003

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED.

Applicant Address

RESEARCH AND DEVELOPMENT CENTER FOCR IRON AND STEEL,DORANDA,RANCHI-834002

Inventors:

#	Inventor's Name	Inventor's Address
1	NILADRI SEN	RESEARCH AND DEVELOPMENT CENTER FOR IRON AND STEEL,DORANDA,RANCHI-834002
2	RADHESHYAM SAU	RESEARCH AND DEVELOPMENT CENTER FOR IRON AND STEEL,DORANDA,RANCHI-834002
3	BALAKRISHNA BIRUDAVELU REDDY	RESEARCH AND DEVELOPMENT CENTER FOR IRON AND STEEL,DORANDA,RANCHI-834002

PCT International Classification Number

B22D 11/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA