CLIAMS:CLAIMS

1. An improved process steel making for reduction of aluminium consumption
comprising the steps of:
continuing soft argon purging during changing over;
modifying the addition pattern of deoxidizers and Ferro-alloys in the melt;
adhering chemistry range of sulphur in all heat;
sequentially addition of petroleum coke along with Si-Mn; wherein
before the addition of deoxidizer and Ferro-alloys in the melt blowing of oxygen with addition of lime is carried out followed by degassing is carried out as per requirement in VOR.

2. An improved process steel making as claimed in claim 1, wherein the addition of deoxidizers and Ferro-alloys are introduced in the melt as per following order:
1st batch of Si-Mn (during degassing),
2nd batch of Al & lime;
3rd batch of Al, lime along with Fe-Si (40-60kg); and
last batch of Al & lime followed by Fe-Si as per grade requirement.

3. An improved process steel making as claimed in claim 1, wherein the sequence of addition of petroleum coke is carried out by firstly adding 10-15 kg of petroleum coke along with Si-Mn, and the remaining addition of coke, if required is done after processing and as per grade requirement.

4. An improved process steel making as claimed in claim 1, wherein the addition pattern of deoxidizers includes addition of 70 percent of the Aluminium is added in the beginning as required along with other Ferro-alloy for maximum extent of de-oxidation followed by the addition of rest 30 % of Aluminium along with lime and argon purging for 3-5 minutes for better desulphurization.

5. An improved process steel making as claimed in claim 1, further includes step of decanting slag for removing the carry over slag from converter with the help of overhead cranes in order to take care of low level of phosphorous in steel, thereby achieving a less consumption of Ferro-alloys and Aluminium.

6. An improved process steel making as claimed in claim 1, wherein the addition of Al is made by taking care of vacuum level in SSM

7. An improved process steel making for reduction of aluminium consumption comprising the steps of:
continuing soft argon purging during changing over;
modifying the addition pattern of deoxidizers and Ferro-alloys in the melt; adhering chemistry range of sulphur in all heat;
sequentially addition of petroleum coke along with Si-Mn; wherein
before the addition of deoxidizer and Ferro-alloys in the melt, initial arcing with lime for 5 – 15 minutes is carried out followed by degassing and addition of Al along with other Ferro-alloys and arcing as per requirement in VAR.
,TagSPECI:
AN IMPROVED PROCESS FOR REDUCTION OF ALUMINIUM CONSUMPTION
AT STEEL MAKING UNITS

FIELD OF INVENTION

The present invention relates to a modified process for manufacturing steel with a substantial reduction in the consumption of Aluminium metal. More particularly the present invention provides lower consumption of Aluminium by process modification at Secondary Steel Making units

BACKGROUND ART

A low silicon content of low-carbon Al-killed steel smelting method, wherein the pre-additive containing blast furnace hot metal into the steelmaking process, first through, silicon removal treatment processes, the use of steel-making process, molten steel slag the steel and oxygen, the process of adding low alloyed silicon compound pre-melting refining slag predeoxidation after LF refining molten steel into the station, do not use conventional heating electrodes made of white residue under way, instead of using the buckle cover insulation, blowing under an argon atmosphere with stirring reducing aluminium deoxidizer done quickly made white residue, and then transferred to calcium handling and soft blowing argon under the premise of quality assurance refining inhibited silicon steel back thermodynamic and kinetic conditions, the soft blowing molten steel After argon, into the casting process.

In recent years, along with our country petroleum, nuclear power and other industry the development, user's demand to the low-carbon aluminium steel was getting bigger and bigger. In the low-carbon steel includes right amount of aluminium element (to request in steel products the Al[total] content 0.020-0.050%), but the refined steel's crystal grain, enhances the steel quality and low temperature impact properties. In order to satisfy user's high request to the quality, the manufacturer used the vacuum treated method to enhance the steel pure. The molten steel processing is longer than the pure LF processing production cycle after secondary vacuum treated + LF. Moreover the dynamical condition is the improvement, the metallurgy responds greatly is ampler, if the SiO2 content in dregs is high, the loss of aluminium ingredient will increase, its aluminium ingredient controllability also becomes worse; At the same time, when vacuum treated aluminium volatilization loss one part. Therefore uses in the Secondary vacuum purified steel the aluminium ingredient to be very easy to control purely, but after using secondary vacuum treated + LF, the aluminium content in steel is extremely rambunctious.

The Chinese patent (application number 03113293.6) has publicized one kind "the technique of production of aluminiferous aluminium", this craft uses the electric stove and LF stove fining and continuous casting craft production aluminium content >=0.020% aluminiums, when production without vacuum treated, has not seen the aluminium ingredient to control the report of system method.

The Chinese patent (application number 200710092682.3) publicized one kind "to control the aluminium steel with LF stove refining slag", this material was compounded by the aluminium vitriol earth, lime, dolomite, limestone and wollastonite, its chemical composition weight % was: CaO60.23-67.54, SiO[2]1.90-3.86, Al[2]O[3]10.58-17.57, Mg1.84-5.57, H[2]O0.09-0.23, S0.036-0.042, other are loss by burning loss. This method belongs to the production method of one refining slag material, after is not the LF stove fining, the component control of slag. After using this fining dregs production controls the aluminium steel LF stove fining, the alkalinity of slag (%CaO)/(%SiO[2]) is the 4-6.8, FeO chemical composition (heavy quantity %) is 1.15-3.02. But controls the aluminium steel without vacuum treated, has not seen the report of aluminium ingredient concrete control method.

The Chinese patent (application number 03115465.4) has publicized one kind "including S and production method of Al continuous casting alloy steel", this method uses the direct-current electric stove, the LF stove and vacuum treated and continuous casting craft production including S and Al alloy steel, but only then a stove including S and Al alloy steel's implementation example, lies in the entire production process with emphasis, but in non-aluminium ingredient control method.

The inventors used a vacuum treated continuous casting flow production low-carbon aluminium content steel, leaves the steel to use SiAlBaCa (the Si content 50-60%) deaeration, after Secondary vacuum treated + LF, in the LF location, the basicity of slag according to 3-5 controls, the SiO[2] content in slag reaches 10-20% high, makes up feeds the aluminium wire number of times to reach 2-4 times, and only depends on the experience to control in the steel the aluminium ingredient, but after vacuum treated, in addition the full response between steel slag, causes in the molten steel SiO[2] in aluminium reducing slag to increase the silicon quantity to reach 0.05-0.09%, the loss of aluminium is big, will have slightly carelessly, will cause the aluminium and silicon ingredient exceeding the allowed figure. Aluminium ingredient control qualified rate is only 80-90%.

In summary, under the existing technological background, this domain urgently awaits to be solved the low cost to control in the steel accurate the aluminium ingredient technical question.

In the prior art, as shown in Fig 1, the conventional process in the secondary refining, the argon coupling to the steel ladle which is placed inside a tank is actuated manually and the purging took place for one minute to break the slag crust and then the valve is closed. Thereafter the temperature measurement is carried out with positioning the tank cover and the evacuation of the molten metal is made. In the deoxidizing process the addition of the deoxidizers and the ferro alloys viz Lime + Aluminium (100%), Lime, Si-Mn and Fe-Si are added with no fixed addition pattern. Thereafter the purging took place for 1-2 minutes and the vacuum is released by lifting the tank cover. In case of higher grade heats, coke is added followed by covering the tank with cover and again purging for 2-3 minutes and thereafter vacuum is released. The purging in the conventional process is intermittent.

In secondary steel making of SMS-1, the Ferro-alloy used are mainly Silico-Manganese(Si-Mn), Ferro-Silicon(Fe-Si), Aluminium(Al), High carbon Ferro-Manganese ( HC Fe-Mn) etc. for deoxidation of steel and alloying purposes. Among the lot Al is costliest metal used as deoxidiser. So without disturbing the chemistry requirement of steel, if specific Al consumption can be reduced by ~10% (i.e. from 4.07 kg/t to 3.70kg/t), the cost saving for company will be around Rs 2.2 cores per annum. In order to achieve the above target we conducted an experiment of modifying the conventional secondary steel making process as follows.

SUMMARY OF INVENTION

This invention goal are to provide one kind of steel making method which reduces the aluminium consume, under satisfying premise of craft quality requirement, conserves energy the consumption, solves the background technology to have the above problem.

In an exemplary embodiment, after placement of liquid steel ladle inside the vacuum tank, the argon flow in the ladle is ensured followed by positioning of cover over the vacuum tank for further operation.

In another embodiment the addition of deoxidizers and ferro alloys are introduced in the melt as 1st batch of Si-Mn (during degassing), 2nd batch of Al & lime then 3rd batch of Al, lime along with Fe-Si (40-60kg) then last batch of Al & lime followed by Fe-Si as per grade requirement

In yet another embodiment the addition of petroleum coke has been introduced for processing of high grade heat (Carbon > 0.10% and Mn. > 0.70%) for de-oxidation as well as alloying purpose. For this purpose a bunker has been modified and made it operational. The sequence of addition is 10-15 kg. of petroleum coke along with Si-Mn, thereby reduced aluminium consumption. The remaining addition of coke, if required is done after processing and as per grade requirement.

In another embodiment of the present invention, in the modified process in VOR, first Oxygen is blown with lime, thereafter degassing is carried out then addition of Al along with other Ferro-alloys is done, as per requirement in VOR. In VAR initial arcing with lime is carried out for 5 – 15 minutes followed by degassing and addition of Al along with other Ferro-alloys and arcing.

In another embodiment of the present invention, in the beginning of process 70 percent of the Aluminium is added as required along with other Ferro-alloy for maximum extent of de-oxidation followed by the addition of rest 30 % of Aluminium along with lime and argon purging for 3-5 minutes for better desulphurization.

As per yet another embodiment of the present invention, in order to take care of low level of phosphorous in steel, slag decanting is done to remove the carry over slag from converter with the help of overhead cranes. This helps in achieving a cleaner steel w.r.t. phosphorous

As per yet another embodiment of the present invention, the addition of Al is made by taking care of vacuum level in SSM

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

Fig. 1 illustrates a flowchart for the conventional process as prior art;

Fig. 2 illustrates a flowchart for the modified process in accordance with the present invention.

DETAILED DESCRIPTION

Technical question that this invention solves is to provide one kind may in the accurate and stable control steel the aluminium ingredient method, particularly controls the aluminium ingredient in the making of low-carbon steel

Craft route of steel-making is: converter smelting ->Secondary refining under vacuum-->LF refining -> continuous casting; Or after the Secondary refining under vacuum ,LF refining, namely the craft route is: converter smelting --> vacuum refining+LF -> continuous casting. This invention solution technical question is to approve the following technique plan realizes, it including the following step:

A) Converter smelting, after initially steel-making tapping, uses the aluminium deaeration;

B) vacuum refining + LF working procedure:

C) Continuous casting;

The committed step lies in: LF fining working procedure that step B stated: When slag formation the dregs material joined quantity is the 20 – 22 Kg/t steel; And, the major targets or quotas of dregs material are: In every 100 weight shares, CaO: 45 - 50 weight share and Al2O3: 25 - 30 weight share, SiO2: 10 - 12 weight share, MgO: 2 - 3 weight share and CaF2: Nil weight share; Namely the major targets or quotas of dregs material are CaO: 45-50 %, Al2O3: 25 – 30 %, SiO2: 10 - 12%, MgO: 2 – 3 % and CaF2: Nil

In order to improve the metallurgy quality of steel, may use the vacuum treated (VD) + LF refining working procedure: Namely processes for 15-20 minutes in the 67Pa following vacuum, the argon current capacity is 50-100L/min; the function removes in the steel almost fully the gas.

In the above method, to enhance the aluminium ingredient accuracy control may further use the following point wise steps and parameters as shown in Fig 2 and as described below:

i. After placement of liquid steel ladle inside the vacuum tank, argon flow in the ladle is carried out followed by positioning of cover over the vacuum tank for further operation. In conventional process after ensuring argon flow in manual mode argon valve remain closed for 5-6 minutes for activities like temperature measurement positioning of cover and sample (if required) and then shifted to auto mode. In modified process Instead of closing the argon purging while changing over from manual to auto mode / changing lid, the soft argon purging is continued which helps in reducing the oxygen ppm of Steel from about 60 to 100ppm resulting lesser consumption of de-oxidizers.

ii. Al, Fe-Si, Si-Mn, and Petroleum Coke etc. used at Secondary Steel making unit as deoxidizers and alloying purposes. In conventional process Al is used entirely for de-oxidation purposes. In order to reduce the Al Consumption a partial fulfillment of Al is done through use of Fe-Si, Si-Mn. So a modification in conventional process has been adopted by changing the addition pattern as follows:
Conventional addition pattern: Three batches of Al & lime followed by Si-Mn and Fe-Si as per grade requirement.
Modified addition pattern: 1st batch of Si-Mn (during degassing), 2nd batch of Al & lime then 3rd batch of Al, lime along with Fe-Si (40-60kg) then last batch of Al & lime followed by Fe-Si as per grade requirement.

iii. Restriction of the sulphur level of steel as per grade requirements. The said restriction helps in reducing further consumption of Al. In conventional operation a general mindset was to reduce the sulphur level of steel as low as possible irrespective of grade requirement resulting a higher Al consumption. In the modified process, the chemistry range particularly sulphur in all heat is adhered to. As example CRNO (50C700 grade) the required sulphur is <0.025, therefore there is no need to bring it to <0.010 or less by cost of aluminium.

iv. In the conventional process the petroleum coke addition done manually after all additions resulting the following: -
(a) Poor carbon recovery hence a higher aluminium consumption.
(b) Very unsafe to use in open condition due to a high flame shooting resulting a frequent cable burnout and more prone to equipment failure
(c) Not environment friendly due to a high smoke generation in open condition
In modified process addition of petroleum coke has been introduced for processing of high grade heat (Carbon > 0.10% and Mn > 0.70%) for de-oxidation as well as alloying purpose. For this purpose a bunker has been modified and made it operational. The sequence of addition is 10-15 kg. of petroleum coke along with Si-Mn, thereby reduced aluminium consumption. The remaining addition of coke, if required was done after processing and as per grade requirement.

v. In conventional operating practice of VOR or VAR, the addition of Al along with other Ferro-alloys were made at the beginning of the process followed by immediate oxygen blowing or arcing. This was resulted a high Aluminium loss/ fading thereby increased consumption of aluminium.
In modified process first Oxygen is blown with lime, degassing then addition of Al along with other Ferro alloys is carried out as per requirement in VOR. In VAR initial arcing with lime for 5 – 15 minutes is done followed by degassing and addition of Al along with other Ferro -alloys and arcing.

vi. Aluminium is a strong deoxidiser and controls the oxygen activity in liquid steel indicated by following chemical reaction:
2 [Al] + 3 [O] Al2O3 + Heat energy

So the aluminium deoxidizes the steel to a very low extent of oxygen. If the steel contains higher oxygen activity, the aluminium will react preferably with oxygen. After the aluminium deoxidizes the steel to a very low oxygen activity, then the following reaction takes place for desulphurization:
3(CaO) + 2 [Al] + 3 [S] 3(CaS) + (Al2O3)

As per modified process, in the beginning of process 70 percent of the Aluminium is added as required along with other Ferro-alloy for maximum extent of de-oxidation followed by the addition of rest 30 % of Aluminium along with lime and argon purging for 3-5 minutes for better desulphurization.

vii. Presently the shop produces about 50% of special steel which requires low level of sulphur and phosphorous (0.025% max. each) so in order to take care of low level of phosphorous in steel, slag decanting done to remove the carry over slag from converter with the help of overhead cranes. This helps in achieving a less consumption of Ferro-alloys and Aluminium.

viii. In conventional process addition of Al were made without taking care of vacuum level but in modified process the addition of Al were made by taking care of vacuum level in SSM

ix. By implementing above mentioned technical measures a trial were conducted form the month of August onwards, the results are shown in the following tables

Table1: Specific Aluminium Consumption for 2011-12 & 2012-13:
Year Sp. Aluminium Cons. (Kg/T) CRNO/Non CRNO (LG+HG)
2011-12 4.07 1315/620+3343
2012-13 4.03 1435/841 + 3325

Table 2: Specific Aluminium Consumption for 2013-14:

Month Sp. Cons. Of Aluminium (Kg/T) Sp. Cons. Of Aluminium in CRNO (Kg/T) CRNO/Non CRNO (LG+HG)
Apr 4.29 5.23 133/48+256
May 4.11 5.34 104/39+266
Jun 4.04 5.23 110/91+191
Jul 4.14 4.94 141/23+233
Aug 3.69 4.32 141/24+271
Sep 3.33 4.49 101/115+277
Oct 3.21 3.96 94/69+436
Nov 3.22 4.02 119/101+359

Table 3: Month wise special heats for 2013-14:

Month
(2013-14) Total heats/Spl. Heats (excluding CRNO) %, Spl. Heats
May’2013 407/92 22.60
June’13 391/101 25.83
July’13 392/89 22.70
Aug’13 437/106 24.37
Sept’13 493/138 28.00
Oct’13 599/149 25.00
Nov’13 575/144 25.00

Table 4: Sulphur distribution for CRNO grades (2013-14):

Months (2013-14) Total CRNO (Nos) < 0.05 0.06 – 0.010 0.011 – 0.015 0.016 – 0.020 0.021 – 0.025 0.026 – 0.030
June’13 110 05 61 21 12 03 02
July’13 141 13 66 35 17 06 02
Aug’13 141 07 56 37 21 05 00
Sept’13 101 05 16 34 31 12 03
Oct’13 94 00 29 28 27 08 02
Nov 119 18 45 23 19 09 05

Financial benefits:

Aluminium consumption (Kg/T)
Fy 2011-12 was 4.07 Kg/T
Fy 2012-13 was 4.03 Kg/T
Fy 2013-14 APP is 4.07 Kg/T
For the last 4(Four) months (Aug. to Nov. 2013, trial period) the average Aluminium consumption is 3.36 Kg/T.
*(Projected annual cons. Of Al for FY 2013-14 is taken as 3.70 Kg/T)
So the saving is 4.07 – 3.70* = 0.37 Kg/T.
As the APP for 2013-14 is 4, 21, 000 TCS
Hence the Total quantity of Aluminium saved is:0.37 X 4, 21,000 = 1, 55, 770 Kg.
The cost saving by the above project, works out to be (@Rs 141.00/Kg of Al):
141 X 1, 55, 770 = Rs 2, 19, 63, 570 (~2.20 Crores)

Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

CLAIMS

1. An improved process steel making for reduction of aluminium consumption
comprising the steps of:
continuing soft argon purging during changing over;
modifying the addition pattern of deoxidizers and Ferro-alloys in the melt;
adhering chemistry range of sulphur in all heat;
sequentially addition of petroleum coke along with Si-Mn; wherein
before the addition of deoxidizer and Ferro-alloys in the melt blowing of oxygen with addition of lime is carried out followed by degassing is carried out as per requirement in VOR.

2. An improved process steel making as claimed in claim 1, wherein the addition of deoxidizers and Ferro-alloys are introduced in the melt as per following order:
1st batch of Si-Mn (during degassing),
2nd batch of Al & lime;
3rd batch of Al, lime along with Fe-Si (40-60kg); and
last batch of Al & lime followed by Fe-Si as per grade requirement.

3. An improved process steel making as claimed in claim 1, wherein the sequence of addition of petroleum coke is carried out by firstly adding 10-15 kg of petroleum coke along with Si-Mn, and the remaining addition of coke, if required is done after processing and as per grade requirement.

4. An improved process steel making as claimed in claim 1, wherein the addition pattern of deoxidizers includes addition of 70 percent of the Aluminium is added in the beginning as required along with other Ferro-alloy for maximum extent of de-oxidation followed by the addition of rest 30 % of Aluminium along with lime and argon purging for 3-5 minutes for better desulphurization.

5. An improved process steel making as claimed in claim 1, further includes step of decanting slag for removing the carry over slag from converter with the help of overhead cranes in order to take care of low level of phosphorous in steel, thereby achieving a less consumption of Ferro-alloys and Aluminium.

6. An improved process steel making as claimed in claim 1, wherein the addition of Al is made by taking care of vacuum level in SSM

7. An improved process steel making for reduction of aluminium consumption comprising the steps of:
continuing soft argon purging during changing over;
modifying the addition pattern of deoxidizers and Ferro-alloys in the melt;
adhering chemistry range of sulphur in all heat;
sequentially addition of petroleum coke along with Si-Mn; wherein
before the addition of deoxidizer and Ferro-alloys in the melt, initial arcing with lime for 5 – 15 minutes is carried out followed by degassing and addition of Al along with other Ferro-alloys and arcing as per requirement in VAR.

Dated: this day of , 2014.

(N. K. Gupta)
Patent Agent,
Of NICHE,
For SAIL

To,
The Controller of Patents,
The Patent Office, Kolkata.

ABSTRACT

AN IMPROVED PROCESS FOR REDUCTION OF ALUMINIUM CONSUMPTION
AT STEEL MAKING UNITS
The present invention relates to a modified process for manufacturing steel with a substantial reduction in the consumption of Aluminium metal. More particularly the present invention provides lower consumption of Aluminium by process modification at Secondary Steel Making units