Claims:We Claim:

1. A method of converting liquid Metal suitable for Open Casting from liquid metal suitable for CSP caster/Close Casting and vice versa in Secondary steel making comprising
i) tapping liquid steel from Convertor cum Arc Furnace / Primary Steel Making furnace with O potential of of 500-1000 ppm ,Tap % C 0.03 – 0.0.1 , Temp 1600-1640 Deg C;
ii) ascertaining the % Al, % S and final O ppm in liquid steel to identify its suitability for (a) CSP/Close casting with minimum 0.01 % Al, maximum 0.007 % S and maximum 25 ppm O ppm or (b) open casting with maximum 0.005 % Al, maximum 0.02 % S and 40-100 ppm O ppm ;
iii) step of converting the thus identified liquid steel suitable for CSP/Close casting to liquid steel suitable for open casting or liquid steel suitable for open casting to liquid steel suitable for CSP/Close casting at ladle furnace free of any required reprocessing at Convertor cum Arc Furnace/Primary Steel Making furnace.

2. A method as claimed in claim 1 wherein said step of converting liquid steel suitable for CSP/Close casting to liquid steel suitable for open casting is done to achieve a target liquid steel suitable for open casting having on weight basis:
%C- 0.1-0.30;
%Mn- 0.5-1.5;
%Si- 0.1-0.3;
%S- 0.025 max;
%P 0.030 max;
%Al- 0.005 max;and
N 90 ppm max.

3. A method as claimed in claim 1 wherein said step of converting liquid steel suitable for open casting to liquid steel suitable for CSP/Close casting is done to achieve a target liquid steel suitable for CSP/Close casting having on weight basis:
%C- 0.035-0.30;
%Mn- 0.5-1.5;
%Si- 0.1-0.3;
%S- 0.007 max;
%P 0.025 max;
%Al- 0.01 min;and
N 90 ppm max.

4. A method as claimed in claim 2 wherein said converting the thus identified liquid steel suitable for CSP/Close casting to liquid steel suitable for open casting comprises:
i)adding Si-Mn or Ferro-Mn if required to achieve 80% of the target chemistry;
ii)adding mill scale (Fe2O3) to oxidize ‘Al’ to ‘Al2O3’ and float into slag;
iii)removing slag into the slag pit;
iv)adding lime to make fresh slag;
v)starting arcing to increase liquid metal temp.;
vi)checking temp & slag colour;
vii)taking liquid metal sample to check chemistry and in case of Al > 0.007 %, adding more mill scale (Fe2O3) and repeating the process from step – v.
viii)adding ferro alloys to achieve target chemistry;
ix)injecting Ca wire & maintain desired Calcium ppm of 15-20 ppm to thus convert to desired heat for open casting process.

5. A method as claimed in claim 4 wherein said converting the thus identified liquid steel suitable for CSP/Close casting to liquid steel suitable for open casting comprises:
i)Adding Si-Mn or Ferro-Mn if required to achieve 80% of the target chemistry;
ii)Adding 200-400 kg of mill scale (Fe2O3) to oxidize ‘Al’ to ‘Al2O3’ and float into slag;
iii)removing slag into the slag pit;
iv)adding 300-500 kg of lime to make fresh slag;
v)starting arcing to increase liquid metal temp.;
vi)checking temp & slag colour;
vii)taking liquid metal sample to check chemistry and in case of Al > 0.007 %, adding more mill scale (Fe2O3) and repeating the process from step – v.
viii)adding ferro alloys to achieve target chemistry;
ix)injecting Ca wire & maintain desired Calcium ppm of 15-20 ppm to thus convert to desired heat for open casting process.

6. A method as claimed in claim 3 wherein said converting the thus identified liquid steel suitable for Open casting to liquid steel suitable for CSP/Close casting comprises:

i) adding Aluminum wire and calcined lime;
ii)starting arcing to increase liquid metal temp.;
iii)checking temp & slag colour;
iv)taking liquid metal sample to check chemistry and in case of %S>0.008, adding more aluminum wire and calcined lime and in case of Al < 0.015 % & S < 0.007 %, adding further aluminum wire to meet target chemistry of ‘Al’;
v)adding ferro alloys to achieve target chemistry;
vi)injecting Ca wire & maintaining desired Calcium ppm of 15-25 ppm to thus convert to desired liquid steel for CSP/Close casting process.

7. A method as claimed in claim 6 wherein said converting the thus identified liquid steel suitable for Open casting to liquid steel suitable for CSP/Close casting comprises:

i)adding Aluminum wire and calcined lime;
ii)starting arcing to increase liquid metal temperature in the range of 1570 to 1600 Deg c
iii)increasing the purging rate to 30 to 70 NM3/HR for better slag metal reaction;
iv)checking temp & slag colour;
v)taking liquid metal sample to check chemistry and in case of %S>0.008, adding more aluminum wire and calcined lime and in case of Al < 0.015 % & S < 0.007 %, adding further aluminum wire to meet target chemistry of ‘Al’;
vi)adding ferro alloys to achieve target chemistry;
vii)injecting Ca wire & maintaining desired Calcium ppm of 15-25 ppm to thus convert to desired liquid steel for CSP/Close casting process.

8. A method as claimed in anyone of claims 4 or 5 for conversion of liquid metal for CSP caster having:

%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.03-0.07 0.1- 1.5 0.03-0.30 0.004-0.007 0.007-0.030 0.010-0.040 0.010-0.040 40-90 20-30

to liquid metal suitable for open caster comprising the steps of:

(i) adding 400 to 3500 kg of Si-Mn & 200 to 800 kg of FeSi to get the desired %MN of 0.5 to 1.5 % and %Si of 0.1 to 0.3
(ii) adding 200 to 400 kg of mill scale to reduce the Al in the range of 0.002 to 0.005% and convert it into Al2O3;
(iii) removing slag in the slag pit;
(iv) adding 200 to 600 kg of lime to generate fresh slag;
(v) ensuring temperature of the bath in the range of 1570 to 1600 °c
(vi) arcing for 05 to 15 mins to raise the temperature to 1570 to 1600 °c preferably about 1580 °c
(vii) ensuring temperature and liquid metal sample in the range of 1570 to 1600 °c and provide for the liquid metal having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1 to 0.3 0.5 to 1.5 0.1 to 0.3 0.008 to 0.020 0.007 to 0.030 0.006 to 0.010 0.005 to 0.009 40 to 90 5 to 15

(viii) adding 50 to 100 kg of mill scale to bring down further Al;
(ix) Injecting Ca wire, and providing for the converted liquid metal for open casting having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1 to 0.3 0.5 to 1.5 0.1 to 0.3 0.008 to 0.020 0.007to 0.030 0.005 max 0.005 max 40 to 90 5 to 15

9. A method as claimed in anyone of claims 4 or 5 for conversion of liquid metal for Close caster having :

%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.004-0.008 0.007-0.030 0.010-0.030 0.010-0.030 40-90 10-20

to liquid metal suitable for Open caster comprising the steps of:

(i) adding 200 to 400 kg of mill scale to reduce the Al in the range of 0.002 to 0.005% and convert it into Al2O3;
(ii) removing slag in the slag pit;
(iii)adding 200 to 600 kg of lime to make fresh slag;
(iv)taking temperature of the bath;
(v)arcing for 05 to 15 mins to raise the temperature to 1570 to 1600 °c preferably 1580 Deg C;
(vi) ensuring temperature and liquid metal sample having
%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.02 max 0.007-0.030 0.006-0.010 0.006-0.010 45-90 10-20

(vii)Inject Ca wire, and providing for the converted liquid metal for open casting having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.02 max 0.007-0.030 0.005 max 0.005 max 45-90 10-20

10. A method as claimed in anyone of claims 6 or 7 for conversion of liquid metal for open caster having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.02 max 0.007-0.030 0.001-0.005 0.001-0.005 45-90 10-20

to liquid metal suitable for Close caster comprising the steps of:

i)Arcing for 02 to 10 mins preferably 5 mins to raise the temperature to 1570 to 1600 °c preferably to 1580 Deg C;
ii)Adding 200 to 600 kg of lime and aluminum wire 50 to 200 mtr for desulphurization and Aluminum build up;
iii)Increasing the Ar purging rate to 30 to 70 NM3/hr preferably 60 NM3/Hr for mixing of slag metal reaction and desulphurization;
iv)Taking slag sample and checking for color for desulphurization;
v)ensuring temperature of the bath and liquid metal sample having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.008 max 0.007-0.030 0.010 min 0.010 min 45-90 10-20

vi)Injecting Ca wire, and providing for the converted liquid metal for Close casting having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.008 max 0.007-0.030 0.010 min 0.010 min 45-90 15-25

Dated this the 31st day of January, 2017
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

, Description:FIELD OF THE INVENTION

The present invention relates to a method for producing as well as converting liquid metal suitable for Compact Strip Production (CSP) caster/close casting (Billet) and or open casting ( Billet) and vice versa in secondary steel making in a fast and cost effective manner without interrupting production. More particularly, the present invention is directed to a method for converting liquid Metal suitable for Open Casting from liquid metal suitable for CSP caster/Close Casting and vice versa in Secondary steel making in Ladle Refining Furnace (LRF) itself without the need for further reprocessing in CONARC(Convertor cum Arc Furnace – Primary Steel Making) furnace for adjusting steel chemistry to suit a either open or CSP caster/close casting, thus reducing cost and time for steel produced and eliminating loss of productivity avoiding situations to restrict production of Steel Melt Shop as well as some time Blast Furnace (Liquid Iron) also.

BACKGROUND OF THE INVENTION

At the applicants manufacturing facility at JSW Steel Limited, Dolvi works, there is 1 unit of Steel Melt Shop, 2 nos. of thin slab caster and 1 continuous casting billet machine. Steel Melt Shop and Ladle Furnace is supplying liquid steel to both Slab as well as Billet casting machines. In thin slab casting process there is stringent requirement of liquid metal chemical composition such as low level of Oxygen, low level of Carbon, high Aluminum and calcium treatment. In continuous casting billet machine, there is provision of both open casting and close casting. Apart from the distinguished difference between the open casting and close casting principles such as use of submerged entry nozzle (SEN), lubrication used (Oil/Powder) etc. there is requirement of liquid steel quality in terms chemical composition such as %Al and O ppm. Liquid steel suitable for CSP caster / close casting billet cannot be processed through open casting and vice versa unless it is reprocessed. So for if any reason liquid steel prepared in ladle furnace for CSP Caster/ close casting process is not casted, liquid steel needs to be reprocessed in the CONARC(Convertor cum Arc Furnace – Primary Steel Making). This will add cost and hamper productivity as well as we have to restrict production of Steel Melt Shop as well as some time Blast Furnace (Liquid Iron) also.

Thus the deficiencies of the conventional process for producing liquid steel for close/open casting and converting one form to other are as follows:
1. Reprocessing of heats.
2. Productivity Loss.
3. Add production cost.

There has been thus a need in the related field for producing liquid steel suitable for CSP caster/close casting and or open casting and conversion of composition thereof as per requirement of plant according to availability of casting facility in a fast, reliable and cost effective manner to avoid any loss of productivity.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to a method to convert liquid metal suitable for CSP caster/ close casting into liquid metal suitable for open casting and vice versa at ladle furnace itself without reprocessed at CONARC(Convertor cum Arc Furnace – Primary Steel Making) furnace.

A further object of the present invention is directed to said method of converting liquid metal suitable for CSP caster/close casting into liquid metal suitable for open casting and vice versa which would reduce the reprocessing cost and time at CONARC (Convertor cum Arc Furnace – Primary Steel Making) furnace and hence would reduce the reprocess cost of the liquid metal.

A still further object of the present invention is directed to said method of converting liquid metal suitable for CSP caster/close casting into liquid metal suitable for open casting and vice versa which would favour reducing the productivity loss due to any interruption in CSP caster/ close casting or open casting.

A still further object of the present invention is directed to said method of converting liquid metal suitable for CSP caster/close casting into liquid metal suitable for open casting and vice versa involving fast conversion of liquid metal having high Al into low aluminum using waste material like mill scale(waste product of hot strip mill) in Secondary Refining.

A still further object of the present invention is directed to said method of converting liquid metal suitable for CSP caster/close casting into liquid metal suitable for open casting and vice versa wherein there would be no yield loss due to FeO generation as liquid metal is processed in Ladle Furnace only and there is no reblow of oxygen.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a method of converting liquid Metal suitable for Open Casting from liquid metal suitable for CSP caster/Close Casting and vice versa in Secondary steel making comprising
i) tapping liquid steel from Convertor cum Arc Furnace/ Primary Steel Making furnace with O potential of of 500-1000 ppm ,Tap % C 0.03 – 0.0.1 , Temp 1600-1640 Deg C;
ii) ascertaining the % Al, % S and final O ppm in liquid steel to identify its suitability for (a) CSP/Close casting with minimum 0.01 % Al, maximum 0.007 % S and maximum 25 ppm O ppm or (b) open casting with maximum 0.005 % Al, maximum 0.02 % S and 40-100 ppm O ppm ;
iii) step of converting the thus identified liquid steel suitable for CSP/Close casting to liquid steel suitable for open casting or liquid steel suitable for open casting to liquid steel suitable for CSP/Close casting at ladle furnace free of any required reprocessing at Convertor cum Arc Furnace/Primary Steel Making furnace.

A further aspect of the present invention is directed to said method wherein said step of converting liquid steel suitable for CSP/Close casting to liquid steel suitable for open casting is done to achieve a target liquid steel suitable for open casting having on weight basis:
%C- 0.1-0.30;
%Mn- 0.5-1.5;
%Si- 0.1-0.3;
%S- 0.025 max;
%P 0.030 max;
%Al- 0.005 max; and
N 90 ppm max.

A still further aspect of the present invention is directed to said method wherein said step of converting liquid steel suitable for open casting to liquid steel suitable for CSP/Close casting is done to achieve a target liquid steel suitable for CSP/Close casting having on weight basis:
%C- 0.035-0.30;
%Mn- 0.5-1.5;
%Si- 0.1-0.3;
%S- 0.007 max;
%P 0.025 max;
%Al- 0.01 min; and
N 90 ppm max.

A still further aspect of the present invention is directed to said method wherein said converting the thus identified liquid steel suitable for CSP/Close casting to liquid steel suitable for open casting comprises:
i) adding Si-Mn or Ferro-Mn if required to achieve 80% of the target chemistry;
ii) adding mill scale (Fe2O3) to oxidize ‘Al’ to ‘Al2O3’ and float into slag;
iii) removing slag into the slag pit;
iv) adding lime to make fresh slag;
v) starting arcing to increase liquid metal temp.;
vi) checking temp & slag colour;
vii) taking liquid metal sample to check chemistry and in case of Al > 0.007 %, adding more mill scale (Fe2O3) and repeating the process from step – v.
viii) adding ferro alloys to achieve target chemistry;
ix) injecting Ca wire & maintain desired Calcium ppm of 15-20 ppm to thus convert to desired heat for open casting process.

Another aspect of the present invention is directed to said method wherein said converting the thus identified liquid steel suitable for CSP/Close casting to liquid steel suitable for open casting comprises:
i) Adding Si-Mn or Ferro-Mn if required to achieve 80% of the target chemistry;
ii) Adding 200-400 kg of mill scale (Fe2O3) to oxidize ‘Al’ to ‘Al2O3’ and float into slag;
iii) removing slag into the slag pit;
iv) adding 300-500 kg of lime to make fresh slag;
v) starting arcing to increase liquid metal temp.;
vi) checking temp & slag colour;
vii) taking liquid metal sample to check chemistry and in case of Al > 0.007 %, adding more mill scale (Fe2O3) and repeating the process from step – v.
viii) adding ferro alloys to achieve target chemistry;
ix) injecting Ca wire & maintain desired Calcium ppm of 15-20 ppm to thus convert to desired heat for open casting process.

Yet another aspect of the present invention is directed to said method wherein said converting the thus identified liquid steel suitable for Open casting to liquid steel suitable for CSP/Close casting comprises:

(i) adding Aluminum wire and calcined lime;
(ii) starting arcing to increase liquid metal temp.;
(iii) checking temp & slag colour;
(iv) taking liquid metal sample to check chemistry and in case of %S>0.008, adding more aluminum wire and calcined lime and in case of Al < 0.015 % & S < 0.007 %, adding further aluminum wire to meet target chemistry of ‘Al’;
(v) adding ferro alloys to achieve target chemistry;
(vi) injecting Ca wire & maintaining desired Calcium ppm of 15-25 ppm to thus convert to desired liquid steel for CSP/Close casting process.

A still further aspect of the present invention is directed to said method wherein said converting the thus identified liquid steel suitable for Open casting to liquid steel suitable for CSP/Close casting comprises:

i) adding Aluminum wire and calcined lime;
ii) starting arcing to increase liquid metal temperature in the range of 1570 to 1600 °c;
iii) increasing the purging rate 30 to 70 NM3/hr for better slag metal reaction;
iv) checking temp & slag colour;
v) taking liquid metal sample to check chemistry and in case of %S>0.008, adding more aluminum wire and calcined lime and in case of Al < 0.015 % & S < 0.007 %, adding further aluminum wire to meet target chemistry of ‘Al’;
vi) adding ferro alloys to achieve target chemistry;
vii) injecting Ca wire & maintaining desired Calcium ppm of 15-25 ppm to thus convert to desired liquid steel for CSP/Close casting process.

A still further aspect of the present invention is directed to said method for conversion of liquid metal for CSP caster having :

%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.03-0.07 0.1- 1.5 0.03-0.30 0.004-0.007 0.007-0.030 0.010-0.040 0.010-0.040 40-90 20-30

to liquid metal suitable for open caster comprising the steps of:

(i) adding 400 to 3500 kg of Si-Mn & 200 to 800 kg of FeSi to get the desired %MN of 0.5 to 1.5 % and %Si of 0.1 to 0.3
(ii) adding 200 to 400 kg of mill scale to reduce the Al in the range of 0.002 to 0.005% and convert it into Al2O3;
(iii) removing slag in the slag pit;
(iv) adding 200 to 600 kg of lime to generate fresh slag;
(v) ensuring temperature of the bath in the range of 1570 to 1600 °c
(vi) arcing for 05 to 15 mins to raise the temperature to 1570 to 1600 °c preferably about 1580 °c
(vii) ensuring temperature and liquid metal sample in the range of 1570 to 1600 °c and provide for the liquid metal having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1 to 0.3 0.5 to 1.5 0.1 to 0.3 0.008 to 0.020 0.007 to 0.030 0.006 to 0.010 0.005 to 0.009 40 to 90 5 to 15

(viii) adding 50 to 100 kg of mill scale to bring down further Al;
(ix) Injecting Ca wire, and providing for the converted liquid metal for open casting having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1 to 0.3 0.5 to 1.5 0.1 to 0.3 0.008 to 0.020 0.007to 0.030 0.005 max 0.005 max 40 to 90 5 to 15

A still further aspect of the present invention is directed to said method for conversion of liquid metal for Close caster having

%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.004-0.008 0.007-0.030 0.010-0.030 0.010-0.030 40-90 10-20

to liquid metal suitable for Open caster comprising the steps of:

(i) adding 200 to 400 kg of mill scale to reduce the Al in the range of 0.002 to 0.005% and convert it into Al2O3;
(ii) removing slag in the slag pit;
(iii)adding 200 to 600 kg of lime to make fresh slag;
(iv)taking temperature of the bath;
(v)arcing for 05 to 15 mins to raise the temperature to 1570 to 1600 °c preferably 1580 Deg C;
(vi) ensuring temperature and liquid metal sample having
%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.02 max 0.007-0.030 0.006-0.010 0.006-0.010 45-90 10-20

(vii)Inject Ca wire, and providing for the converted liquid metal for open casting having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.02 max 0.007-0.030 0.005 max 0.005 max 45-90 10-20

A still further aspect of the present invention is directed to said method for conversion of liquid metal for open caster having
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.02 max 0.007-0.030 0.001-0.005 0.001-0.005 45-90 10-20

to liquid metal suitable for Close caster comprising the steps of:

(i) Arcing for 02 to 10 mins preferably 5 mins to raise the temperature to 1570 to 1600 °c preferably to 1580 Deg C;
(ii) Adding 200 to 600 kg of lime and aluminum wire 50 to 200 mtr for desulphurization and Aluminum build up;
(iii) Increasing the Ar purging rate to 30 to 70 NM3/hr preferably 60 NM3/Hr for mixing of slag metal reaction and desulphurization;
(iv) Taking slag sample and checking for color for desulphurization;
(v) ensuring temperature of the bath and liquid metal sample having

%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.008 max 0.007-0.030 0.010 min 0.010 min 45-90 10-20

(vi) Injecting Ca wire, and providing for the converted liquid metal for Close casting having

%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.1-0.3 0.5-1.5 0.1-0.3 0.008 max 0.007-0.030 0.010 min 0.010 min 45-90 15-25

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to accompanying non limiting illustrative examples.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING EXAMPLES

The present invention is directed to a method of converting liquid Metal suitable for Open Casting from liquid metal suitable for CSP caster / Close Casting and vice versa in Secondary steel making in Ladle Refining Furnace (LRF) itself without the need for further reprocessing in CONARC furnace for adjusting steel chemistry to suit a either open or CSP caster/close casting, thus reducing cost and time for steel produced and eliminating loss of productivity

It should be noted that liquid steel suitable for CSP caster / close casting billet cannot be processed through open casting and vice versa unless it is reprocessed. So conventionally, if for any reason liquid steel prepared in ladle furnace for CSP Caster/ close casting process is not casted, liquid steel needs to be reprocessed in the CONARC(Convertor cum Arc Furnace – Primary Steel Making).

The present invention thus provides a fast and cost effective method to convert the chemical composition of one type of liquid steel to the other and vice versa, by adjusting the chemical composition by involving selective addition and processing steps in ladle refining furnace itself without reprocessing at CONARC (Convertor cum Arc Furnace – Primary Steel Making). Importantly, the method involves fast conversion of liquid metal having high Al into low aluminum using waste material like mill scale in Secondary Refining. The method thus saves time and cost and avoids restriction on production of Steel Melt Shop as well as some time Blast Furnace (Liquid Iron) when any of the casting facility, CSP/close casting or open casting, is not functionally operable for any reason.

A. The distinguished difference between the quality of two steel i.e. for CSP/Close casting and for open casting are as follows:

1. %Al in the final product- for CSP/Close casting, minimum 0.01 % whereas for open casting it is 0.005% maximum
2. %S in the final product- for CSP/Close casting, maximum 0.007% whereas for open casting it is maximum 0.02%
3. Final O ppm in the liquid steel- for CSP/Close casting, maximum 25 ppm whereas for open casting it is 40-100 ppm

B. The sequence of operations for making liquid steel for thin slab casting / close casting according to process of the invention are as follows:
1. Tapping the liquid steel from CONARC (Convertor cum Arc Furnace – Primary Steel Making) furnace with O potential of 500-1000 ppm, Tap %C 0.03-0.0.1, Temp 1600-1640 Deg C
2. Add 200-400 kg of Aluminum ingot, Calcined Lime 600-1000kg and Silico Mn & other relevant ferro alloys to achieve 80% of the desired final chemistry
3. Start Ar purging for homogenization of temperature and chemical composition
4. Bring it to Ladle Refining Furnace (LRF) for processing
5. Arcing for 2-5 minutes to increase the temperature
6. Take liquid metal sample for analysis.
7. Depending upon the opening %S, add aluminum wire, and calcined lime.
8. Increase Ar purging rate for mixing of slag metal reaction to enable fast desulpharization.
9. Take liquid metal sample for checking final chemistry. Take temperature of the liquid metal
10. In final chemistry, %S to be aimed at less than 0.007, %Al 0.01-0.04, %C, %Mn and other alloying elements as per the customer requirement. Final O ppm to be maintained less than 25 ppm.
11. If temperature is less, arcing for few minutes to bring the desired temperature.
12. Inject Pure Ca / CaFeAl wire to maintain Ca ppm 15-25 ppm.
13. Lift the ladle for casting

C. The sequence of operation for making liquid steel for open casting according to process of the invention are as follows:
1. Tapping the liquid steel from CONARC (Convertor cum Arc Furnace – Primary Steel Making) furnace with O potential of 500-600 ppm, Tap %C 0.05-0.0.1, Temp 1600-1640 Deg C;
2. Add Calcined Lime 300-500 kg and Silico Mn to achieve desired final chemistry. No addition of Aluminum ingot as %Al requirement in final steel is very low.
3. Start Ar purging for homogenization of temperature and chemical composition;
4. Bring it to Laddle Refining Furnace (LRF) for processing;
5. Arcing for 2-5 minutes to increase the temperature;
6. Take liquid metal sample for analysis.
7. Depending upon the opening %S, add little amount of aluminum wire, and calcined lime.
8. Take liquid metal sample for checking final chemistry. Take temperature of the liquid metal.
9. In final chemistry, %S to be aimed at less than 0.02, %Al <0.005, %C, %Mn and other alloying elements as per the customer requirement. Final O ppm to be maintained 40-100 ppm.
10. If temperature is less arcing for few minutes to bring the desired temperature.
11. Inject Pure Ca wire to maintain Ca ppm 10-15 ppm.
12. Lift the ladle for casting.

D. After liquid metal is made ready for CSP casting/ Close Billet casting : but for any reason, CSP / Close Billet Caster is not ready and heat is to be cast in Open Billet Casting, following method is adopted to convert the liquid metal for Open Billet Casting in Ladle Furnace itself :-
1. Add Si-Mn or Ferro-Mn if required to achieve 80% of the target chemistry
2. Add 200-400 kg of mill scale (Fe2O3) to oxidize ‘Al’ to ‘Al2O3’ and float into slag. The reaction takes place are as follows :
Al(S)+ Fe2O3 = Al2O3+Fe
3. Remove slag into the slag pit
4. Add 300-500 kg of lime to make fresh slag
5. Start arcing to increase liquid metal temp.
6. Check temp & slag colour
7. Take liquid metal sample to check chemistry
8. In case of Al > 0.007 %, add more mill scale (Fe2O3) and repeat the process from step – 5.
9. Add ferro alloys to achieve target chemistry
10. Inject Ca wire & maintain desired Calcium ppm of 15-20 ppm.
11. Lift the heat for open casting process.

E. When liquid metal is prepared for Open casting and for any reason, it is not possible to cast the liquid steel in open casting mode of billet caster, following method is adopted to convert the liquid metal to that for CSP/Closed caster, in Ladle Furnace only:

1. Add Aluminum wire and calcined lime.
2. Start arcing to increase liquid metal temp.
3. Increase the purging rate for better slag metal reaction.
4. Check temp & slag colour
5. Take liquid metal sample to check chemistry
6. If %S>0.008, add more aluminum wire and calcined lime.
7. In case of Al < 0.015 % & S < 0.007 %, add further aluminum wire to meet target chemistry of ‘Al’.
8. Add ferro alloys to achieve target chemistry
9. Inject Ca wire & maintain desired Calcium ppm of 15-25 ppm.
10. Lift the heat for CSP/Close casting process

The above processing steps of the method according to present invention and their manner of implementation are illustrated with the help of following examples:

Example-1: Conversion of CSP caster heat to Open caster heat:

a. Actual Chemical composition of liquid metal prepared for CSP caster as follows:
%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.05 0.12 0.02 0.006 0.012 0.025 0.023 50 25

b. Sequence of operation done to convert it to liquid metal suitable for open casting
1. Add 2100 kg of Si-Mn & 200 kg of FeSi to get the desired %MN and %Si
2. Add 500 kg of mill scale to reduce the Al and convert it into Al2O3
3. Remove slag in the slag pit
4. Add 500 kg of lime to make fresh slag
5. Take temperature of the bath
6. Arcing for 4 mins to raise the temperature to 1580 Deg C
7. Take temperature and liquid metal sample
%C %Mn %Si %S %P %Al(t) %Al(s) N
ppm Ca ppm
0.19 0.74 0.23 0.009 0.012 0.007 0.005 60 10

8. Add 100 kg more mill scale to bring down %Al further
9. Inject Ca wire, take final sample.
10. Lift the heat for Open casting of billets.
Final chemical composition of liquid metal prepared for open casting

%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.20 0.75 0.21 0.01 0.012 0.004 0.003 65 18

Example-2: Conversion of Close caster heat to open caster heat

a. Actual Chemical composition of liquid metal prepared for close casting of billets as follows:
%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.19 0.73 0.22 0.007 0.013 0.015 0.014 54 23

b. Sequence of operation done to convert it to liquid metal suitable for open casting
1. Add 300 - 500 kg of mill scale to reduce the Al and convert it into Al2O3
2. Remove slag in the slag pit
3. Add 500 kg of lime to make fresh slag
4. Take temperature of the bath
5. Arcing for 3 mins to raise the temperature to 1580 Deg C
6. Take temperature and liquid metal sample
%C %Mn %Si %S %P %Al(t) %Al(s) N ppm Ca ppm
0.18 0.74 0.23 0.008 0.012 0.005 0.004 65 16

7. Inject Ca wire, take final sample.
8. Lift the heat for Open casting of billets.
Final chemical composition of liquid metal prepared for open casting
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.18 0.74 0.23 0.009 0.012 0.004 0.003 68 19

Example-3: Conversion of open caster heat to close caster heat

a. Actual Chemical composition of liquid metal prepared for open casting of billets as follows:
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.21 0.70 0.21 0.015 0.013 0.005 0.003 55 18

b. Sequence of operation done to convert it to liquid metal suitable for close casting
1. Arcing for 4 mins to raise the temperature to 1580 Deg C
2. Add 500 kg of lime and aluminum wire 150 mtrs for desulphurization and Aluminum build up.
3. Increase the Ar purging rate to 60 NM3/Hr for mixing of slag metal reaction and desulphurization.
4. Take slag sample and check for color for desulphurization
5. Take temperature of the bath and liquid metal sample.

%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.20 0.71 0.20 0.008 0.013 0.012 0.011 65 12

6. Inject Ca wire, take final sample.
7. Lift the heat for close casting of billets.
Final chemical composition of liquid metal prepared for open casting
%C %Mn %Si %S %P %Al(t) %Al(s) Nppm Ca ppm
0.19 0.70 0.20 0.007 0.013 0.009 0.008 68 22

It is thus possible by way of the present invention to provide a method of converting liquid Metal suitable for Open Casting from liquid metal suitable for CSP caster/Close Casting and vice versa in Secondary steel making wherein fast conversion of liquid metal having high Al into low aluminum is achieved using waste material like mill scale in Secondary Refining, offering the following Technological and Techno-economic advantages:

1. No yield loss due to FeO generation as liquid metal is processed in Ladle Furnace only and there is no reblow of oxygen.
2. No reprocessing of liquid steel in CONARC (Convertor cum Arc Furnace – Primary Steel Making) furnace.
3. Conversion is done using mill scale (waste product of hot strip mill).
4. No productivity loss.
5. No loss of Ferro Alloys.

The method according to the present invention thus helps maintaining continuity in production with avoidance of restriction on production chain right from Blast Furnace (BF) to Steel Melt Shop (SMS) while also saving of Reprocessing cost and time.