Metal Preparation

A. Important elements of steel:

i) Carbon:

Carbon is the major alloying element in steel

- Increase in C increases Tensile Strength and Hardness, but decreases

Ductility and Impact Strength.

- Optimum properties of Tensile Strength, Hardness and Impact Strength

are obtained with C in the range of 0.45-0.55%.

- The properties of steel can be altered with heat treatment.

- Carbon content as per IRS-R-19 Part-III Specification is 0.47-0.57% for

Class-A metal & 0.57-0.67% for Class-B metal.

ii) Manganese:

- In presence of C, Mn forms Mn3C and hardens the steel.

- Increases the hardenability of steel.

- It combines with S to form MnS well distributed in steel, reducing the bad

effect of Sulphur.

- Manganese content as per IRS-R-19 Part-III Spec. is 0.6-0.8%

iii) Silicon:

- Si dissolves in steel and strengthens the steel.

- Up to 0.2%, it does not have any appreciable effect on steel.

- It increases tensile strength of steel without decreasing the ductility

between 0.2-0.4%.

- IRS-R-19 Part-III Spec. permits Si range of 0.15-0.70%.

1

iv) Phosphorus:

- It dissolves in steel to form Iron Phosphide and makes steel hard and

brittle.

- It creates crack defects during cold working of steel termed as Cold

Shortness. It is considered as impurity in steel and should be minimized.

- IRS-R-19 Part-III Spec. permits Phosphorus 0.030% max.

v) Sulphur:

- Sulphur forms Iron Sulphide (FeS) in steel.

- It is a low melting point compound and gets segregated along the grain

boundaries during solidification. FeS is a brittle compound and makes

steel brittle at high temp. applications termed as Hot Shortness.

- Presence of Manganese neutralizes this effect to a certain extent, but

Mechanical properties are affected.

- IRS-R-19 Part-III Spec. permits Sulphur content 0.030% max.

- Combined percentage of Phosphorus & Sulphur is to be maintained at

<0.05%

vi) Tramp elements:

- They are usually present in very small quantities.

- Chromium and Nickel: should not exceed 0.25%. They make steel hard

and brittle.

- Copper: should not exceed 0.15%. It increases the propensity to crack.

B. Amount of Calcined Lime in the charge:

a) Calcined Lime (CaO) is used as flux in RWF steel making. It melts during

initial melting of scrap and forms liquid slag. It acts as reservoir for oxides of

Silicon, Manganese, Phosphorus, Sulphur etc. Carbon escapes as CO/CO2 gas.

Main objective of flux addition is to reduce Phosphorus and Sulphur in the

liquid to as low level as possible.

2

First element to get oxidized is Silicon which gets oxidized to SiO2, goes into

slag, reacts with CaO and gets fixed into slag as CaO.2SiO2. Phosphorus gets

oxidized to P2O5 goes in to a slag and gets fixed as {(CaO)4P2O5}.

It is only after reacting with Silicon, balance quantity of CaO will react with

Phosphorus, to remove Phosphorus from the metal. So Lime content should

be over and above required by Silicon available in the scrap.

The ratio of CaO/SiO2 is termed as basicity ratio and should be preferably 2.5-

3.0 for effective dephosphorisation.

b) Calculation:

Silicon content in the RWF scrap = about 0.5%

Hence Si content in 23500 Kgs of steel = 23500x0.5/100 = 117.5 Kgs

As Si+2[O]= SiO2

i.e., 28 Kgs Si forms 60 Kgs SiO2

Hence 117.5 Kgs Si gets converted in to = 117.5x60/28=251.78Kgs SiO2

CaO required = 251.78x3 Kg =755 Kgs.

Cal Lime contains 90% CaO and 2% SiO2

Hence effective CaO present in 100Kgs Lime to maintain basicity of

3 = 90-2x3 Kg =84Kgs

Therefore Calcined Lime required = 775x100/84Kg = 899 Kgs.

In RWF 1100Kgs Calcined Lime is charged as flux.

Since calcined lime reacts with moisture in the air to form CaO+H2O=Ca(OH)2

(slaked lime) and loses its potency, it must been ensured that lime bags are not

damaged and lime charged is in lump shape.

3

C. Furnace Charging:

Furnace charging has been discussed in OM-1. After charging following steps are

followed:-

i) The charge is leveled with magnet

ii) If limestone is on top and at the centre, the scrap is lifted by magnet and

adjusted. This operation is continued few times till the limestone goes down.

Boring chips are added on top for crushing.

iii) The bezel ring is cleaned. Roof is swung, lowered and locked.

iv) All the inter-locks are checked at the time of roof raise, roof lower, roof

swing-out, and roof swing-in operation. Any of these inter-locks should not

be by passed.

D. Melting:

i) The initial arcing of the furnace is started on low tap (Tap-6) to protect the

roof. This is done for one minute. Then VCB (Vaccum Circuit Breaker) is

tripped with all the electrodes resting on the scrap.

ii) Electrodes are adjusted, clamps cleaned with compressed air while adjusting.

iii) Not to over adjust or under adjust the electrodes since this will damage the

furnace hearth portion or cause bridging.

iv) After adjusting the electrodes, the electrodes are lifted well above the scrap

level before closing the VCB to avoid heavy overload of VCB.

v) VCB is closed and arced for 3 or 4 minutes till the electrodes bore and go

down.

vi) Now maximum power should be injected in to the furnace to melt the scrap

and form liquid slag. Hence the tap is changed to the highest tap. Generally

Tap 2 is selected. Initial arcing is with longer arcs so that the side scrap will

melt fast. To achieve this, the rheostat is adjusted in such a way that the load

on individual electrode ranges from 19-20 KA.

4

vii) O2 lancing pipe is inserted in the furnace through the hole in the closed slag

door after about 20 minutes of arcing and Oxygen is partially injected at

moderate pressure (5 to 6 kgf/cm2) into the furnace for oxy-assisted melting.

When the scrap melts during initial period of arcing, Carbon in the charge and

liquid metal reacts with Oxygen, forms CO and tries to escape from the

furnace. If excess O2 is supplied to this CO, it gets converted into CO2

releasing heat. This released heat helps in heating the balance scrap and early

meltdown.

viii) Electrodes should not be raised or lowered manually unless humming is

observed.

ix) 4 or 5 degree angle is provided to the Furnace for easy collapsing of scrap.

x) Over-tilt of the Furnace should be avoided since this may cause Electrode

breakages at the time of scrap collapse or may burn the panels.

xi) If the arcing is healthy throughout (continuous heavy cracking sound indicates

a healthy melting inside the Furnace), clearing the door with Oxygen (O2

pressure is 8-10 kgf/cm2) should be started after 45 or 50 minutes of power on.

xii) The side scrap from the door is cleared first.

xiii) Same tap is continued while cutting the scrap through slag door by O2 lancing.

The current is adjusted if necessary, to ensure that the bath temp does not go

beyond 1540-1560OC till 90% scrap is melted.

xiv) First sample is taken at 1540-1560OC. By this time, majority of the scrap will

have collapsed and the sidewalls are exposed. To prevent side wall refractory

erosion, shorter arc lengths are preferred. By changing to lower taps, furnace

current can be increased, so that arc length is reduced and temp of the bath can

be raised faster. So tap is changed to 4/5. Full current is kept and Carbon boil

started by injecting O2 through the bath. Slag will become foamy and starts

flowing through slag door. Oxidising slag should be removed thoroughly by

C-boil. Maximum slag has to be removed between 1550-1630OC. This will

ensure Phosphorus removal from metal. Second sample is taken after slag off.

-- Slag should not be removed before proper slag volume is formed, and

proper temperature is reached. Improper slag formation and temperature will

5

cause slag metal jam on the door. All the slag metal jam should be cleared

from the door before tilting the Furnace for removal of slag. A shovel of

Dolomite is spread on the slag door to avoid slag metal sticking.

-- Only slag should be removed and not metal. When metal comes out from

the slag door, it will give continuous sparks. While observing the slag flow

through safety glasses, metal sparks cannot be seen. Hence, slag metal flow

should be observed once in-between without the safety goggles, so that metal

flow through door can be identified and stopped.

-- Slag should be taken off as much completely as possible between 15500 to

16300C, because keeping the slag over bath and raising the temperature,

working the heat, deoxidizing with Ferro Manganese, addition of RSM etc.,

will favour Phosphorus reversal from slag to metal.

xv) Samples are air cooled before immersing it in water. This will avoid internal

hair line cracks and wrong chemical analysis.

xvi) The above is Oxidation Period in the bath:-

a) Purpose: To remove Phosphorus from the metal. Phosphorus reacts with

O2. It is oxidized to P2O5 (Phosphoric acid), neutralized by FeO and gets fixed

in the slag as Calcium Phosphate in presence of CaO.

Sources of Oxygen for Phosphorus Oxidation:

- Rusty scrap in the charge

- O2 from the furnace atmosphere

- O2 injection directly from O2 lancing pipe

- The oxidation starts at around 1550-15700C after complete meltdown and

it completes by around 1620-16300C when all oxidizing slag is removed.

b) Main reactions:

[Si] + 2 [O] = (SiO2)

(CaO) + (SiO2) = (CaO.2SiO2)

[Mn] + [O] = (MnO)

(MnO)+(SiO2) = (MnO.SiO2)

4P+5O2= 2P2O5

4(CaO) + (P2O5) = {(CaO)4P2O5}

6

2[P] + 4(CaO) + 5(FeO) = {(CaO)4P2O5}+[Fe]

2C+O2 = 2CO

c) Conditions for effective dephosphorisation:

- Slag should be highly basic in nature

- CaO to SiO2 ratio to be preferably 2.5 to 3.0

- Slag should be oxidizing in nature

- Rate of temperature increase should be slow

- Sufficient bath boil for intermixing of bath and slag to be achieved by

Carbon Boil.

d) Carbon Boil:

- O2 injected in to the bath by lancing.

- Temp 1570-15800C

- CO bubbles generated at the bottom of the hearth rise to the top of the

bath generating heavy boil, termed as Carbon Boil.

- Increases fluidity of slag and makes it to flow out of slag door.

- Oxidation Period.

Advantages of Carbon Boil:

- Nonmetallic inclusions and gases mainly Hydrogen and Nitrogen are

brought to the surface of slag along with CO bubbles.

- Intermixing of slag & metal is ensured for effective dephosphorisation

- Metal composition and temperatures become more uniform through

out the bath.

xvii) Now tap is changed to 4/5. At 16400C electrodes are raised and furnace is

checked for scrap skicking.

xviii) Second sample is taken after slag off. Depending on carbon percentage (if

more than 0.6%) decarborisation is done by providing O2 through lancing

pipe. Slag coated lancing pipe is immersed into metal to burn carbon. One

more sample is taken.

7

xix) Next the bath is deoxidized and reducing slag is made. The purpose of this

phase is :

- To reduce O2 level in steel to as low as possible.

- To clean the steel of any inclusions due to Deoxidation products.

- To reduce Sulphur content of the steel

Sulphur can be removed from the metal only after metal is deoxidised

and all the oxidizing slag is removed at approx 1620-16300C. Sulphur

removal is favoured by

- Low oxygen potential in the bath and slag.

- High basicity of slag >3

- High temperature ( > 16400C)

xx) Heat is blocked by adding Ferro Manganese, a mild deoxidiser. 100 kg of

FeMn is added in the furnace.

xxi) Depending on the opening carbon (If less than 0.5%) bath is recarborised.

Thumb rule is 3.3 kg graphite granules is added in furnace for each hundredth

of percentage point (0.01%). Target is to have 0.55 to 0.60% carbon for class

B and 0.48 to 0.53% for class A steel.

xxii) A new slag is made by adding calcined lime to attain the basicity of 3 to 3.5,

which is fluid and interactive. Lime to the extent of 1 to 1.25% of charge

weight is added to the bath. At present 200 Kgs of calcined lime is added

xxiii) When lime melts and becomes fluid, reducing slag mixture of Calcined Lime,

Graphite Granules & Ferro-Silicon (50 kg:25kg:10kg) are added to deoxidize

the bath. Aluminum shots of 6 to 10 mm size to the tune of 15 Kgs can also

be added. Bath must be thoroughly rabbled.

xxiv) Take third sample.

xxv) Main reactions during this period are :

a) [Mn]+(FeO)= (MnO)+[Fe]

(MnO)+C = [Mn]+CO

(CaO) + 3C = (CaC2) + CO

3(FeO) + (CaC2) = 3 [Fe] + (CaO) + 2CO

3(MnO) + 3C = 3[Mn] + (CaO) + 2CO

8

b) Note:- There can be two methods of deoxidation

Direct Deoxidation:

- Deoxidising elements Fe-Si, Fe-Mn, Aluminum pieces, Coke are

added directly to steel bath.

- Alloys dissolve into the bath, reduce FeO to Fe, forming

deoxidation products and steel is deoxidized.

- Deoxidation products sometimes do not float to the slag in time,

creating inclusion defects in steel.

Deoxidation by diffusion method:

- Deoxidising elements are added in powder form, uniformly on to

the slag layer.

- They react with FeO content of slag reducing it to Fe and

Deoxidation products are formed in the slag layer.

- FeO from the metal passes to the slag by diffusion to maintain the

equilibrium, thus reducing oxygen content of the metal.

- Deoxidation does not take place in bath. Hence there are no

deoxidation products in the liquid metal. Cleaner metal results

than in direct Deoxidation.

RWF follows the latter method.

c) Desulphurisation:

Sulphur plus Phosphorus is to be aimed at pretap 0.030% preferably.

Sulphur removal is very tedious in single slag basic electric steel making

process. Generally the efficiency is 30% removal of the total Sulphur

burden. Sulphur removal is not a chemical reaction unlike Phosphorus

removal. It is a diffusion process. i.e., Sulphur is absorbed from Metal to

Slag as CaS at the slag metal interface under strongly reducing atmosphere

i.e.,

CaO + 3C = CaC2 + CO

Calcium Carbide (CaC2) reacts with FeO in the slag

9

CaC2 + 3FeO = CaO + 3Fe + 2CO

i.e., FeO is removed (deoxidized) from slag. To maintain equilibrium

more FeO from metal diffuse into slag i.e., O2 potential of the bath is

reduced. Further reactions are ;

CaO + FeS = CaS + FeO

[FeS] + (CaO) + C = [Fe] + (CaS) + CO

MnO + FeS = MnS + FeO

[MnS] + (CaO) + C = [Mn] + (CaS) + CO

If deoxidation is not complete

(CaS) + (FeO) = (CaO) + [FeS]

(CaS) + (MnO) = (CaO) + [MnS]

The continued above reaction at the slag metal interfaces favours Sulphur

removal; being a diffusion reaction at the interface, the reaction rate and

efficiency depend on the contact area i.e. mixing. Hence reducing slag needs

rabbling or raking with metal/slag and is a must. Arcing is continued to raise

temp along with mixing to bring down Sulphur.

c1) Note: - Factors favouring Desulphurisation:

- Highly basic slag. CaO/SiO2 ratio to be 3.0-3.5

- Bath should be in deoxidized state. FeO content of the slag should be

minimum

- Slag should be fluid. Sometime flour spar is added to achieve this.

Higher temp. is needed to dissolve more Cal. Lime. Process takes place in

the temp. range of 1640-16700C.

xxvi) The bath is mixed again and after five minutes fourth sample and fifth

samples (check samples) are taken.

xxvii) Temperature is checked. When the temperature is 1660-16700C, the tap is

changed to 8 or 9.

xxviii) Launder is cleared and the tap hole opened.

10

xxix) Slag door should be kept closed always except when necessary for energy

conservation.

xxx) Ladle is lifted from JMP/LPH

- Ladle lift should be so timed that ladle with molten metal arrives JMP just

before the previous heat pouring is completed.

- Ladle lip is prepared at slag off station (SOS).

- Depending on the analysis of check sample Ferro-Silicon, Silico-

Manganese and Graphite granules are added to ladle in metal stream.

Ferro-alloy addition can be guided by the following table:-

For 23.5 MT of Liquid Metal

Item to be added

Element to Increase

Quantity of Ferro Alloy to be added for increase of element

Aim to achieve (Points) (*)

Graphite Granules

Carbon i. Without drain = 2.5 kg for 1 point (0.01%) to increaseii. With drain = 2.3 kg for 1 point (0.01%) to increase* Carbon pick up from LIM by one to two points should be considered while aiming

60-62 for Box-N50-52 for BG Coaching

Ferro Silicon Silicon i. Without drain = 205 to 210 kgii. With drain = 190 to 200 kg* While deciding the above guidelines, Silicon recovery from Silicon Manganese has been considered.

65-68

Silico Manganese

Manganese i. Without drain = 3.8 to3.9 kg for 1 point (0.01%) to increase.ii. With drain =3.4 to 3.5 kg for 1 point (0.01%) to increase.

70-75

Assumption for the above guidance :

i. Total metal = 23.5 t

ii. Drain metal = 2 t

iii. Carbon % in graphite granules = 98%

- Carbon recovery efficiency = 95% of 98% i.e., overall

recovery = 93% of Graphite Granules.

iv. Silicon in Fe Si = 70-75%

11

- Silicon recovery efficiency = 95% of Silicon available

i.e., over all recovery = 65 to 70% of Fe Si

- Silicon pick up from Si Mn has been considered while

providing the guidance value

v. Manganese in Si Mn = 60-65%

- Manganese recovery 95% of Mn available i.e., overall

efficiency = 0.57% to 0.62% of Si Mn

- Silicon in Si Mn = 14 – 17%

To facilitate ferro-alloys addition in metal stream, chute is provided near

furnace launder. After ladle is 1/3rd filled, ferro-alloys are dropped through

the chute.

xxxi) Check the temperature twice before tapping the heat.

xxxii) In the normal conditions, without ladle delay, 1690-16950C temperature is

considered for tapping (when the ladle preparation is over in ten minutes time

and final analysis is received within ten minutes).

xxxiii) O2 is used to open the tap hole from the tap hole side. If the tap hole does not

open in time, oxygen pipe is used for tap hole opening from the slag door side.

xxxiv) While tapping, care is required to see that only metal comes out of the tap hole

initially and not with the slag. This can be achieved by tilting the furnace till

the metal level is above the tap hole.

xxxv) In case of erratic Carbon results, the bath is mixed thoroughly. Five minutes

after the first bath sample, bath is mixed again before taking the second

sample.

xxxvi) In case of viscous slag, one operator must push the slag with the steel rabble

and the second operator must take the sample.

12

E. Preparation of Ladle for Tapping and Pouring:

i) After pouring is over, ladle is covered with dummy cover and kept at JMP

home position till it is removed from the tank to avoid thermal shock to the

bricks and a heavy radiation loss and solidification of liquid metal.

ii) The ladle is lifted from the pit, 12 to 14 minutes before the heat is ready.

Ladle lifting time should be so synchronized that ladle with full metal comes

to JMP as soon as previous heat is just poured. Hence ideally ladle may be

lifted when 17-18th wheel is cast from the previous heat.

iii) The number of wheels poured is checked to assess the quantity of liquid metal

available in the ladle to be used for tapping.

iv) The ladle sidewall should be inspected thoroughly after lowering the ladle at

the SOS. In case of very wide opening in the brick joints at the lower side

wall, ladle should be condemned.

v) Ladle should be centered properly at the tapping station so that the metal

stream strikes the centre of the ladle. Metal stream directed onto side walls

may cause sidewall erosion and sidewall punctures.

vi) After slag off, the lip portion is covered with ramming mass and then with the

raw dolomite.

vii) The slag metal jam below the lip and below the stiffener ring should be

cleaned before the ladle is sent to Moulding Room.

viii) The ladle is centered properly in JMP so that the ladle bail arm is dis-engaged

without problem.

ix) In case of metal/slag spill over to ladle sides, this should be cleared before

sending the ladle to Moulding Room. Cleaning of ladle and bail arms should

not be done once the ladle is inside the tank.

x) One supervisor must be available on the spot when the ladle is lowered and

when it is removed from the John Mohr tank so that he can supervise proper

centering of the ladle and proper dis-engaging of the bail arm.

13

xi) Whenever there is a delay in tapping due to Melting/Moulding problem, the

ladle lip after pouring liquid metal must be cleaned and ladle is kept for pre-

heating.

F. Sample Taking, Cutting and Polishing Operation:

i) First sample should be taken only when 90% of scrap is melt. Otherwise it is

not a representative sample.

ii) Sample should be taken only when the temperature is above 15400C,

preferably between 1540-15600C.

iii) Pre-tap check samples must be taken between 16700C to 16800C only.

iv) Sample should not be taken very close to the electrodes.

v) While taking the samples, the spoon should be dipped as much as possible

inside the metal to get a more homogeneous sample.

vi) While pouring metal inside the sample mould box, sufficient aluminium wire

is fed to avoid blow holes. Sufficient time should be given to ensure

solidification of metal in the mould box.

vii) The sample must be air-cooled till the bright red colour of the sample

becomes dull red colour. This is to avoid internal quenching cracks in the

sample.

viii) Double cutting of the sample should be avoided.

ix) Way surface on cut face should be avoided.

x) A mirror finish should be given to the polished face and the face cleaned

before sending it to the spectrometer analysis.

xi) The sample should be cut on the maximum diameter to get enough surface for

proper sparking at spectrometer.

xii) The bottom face of the sample is ground to have a proper hold in the

spectrometer.

14

G. Aluminium Plunging in Ladle:

Aluminium plunging is done in the ladle when the metal temperature is 16100C. This

is primarily to take care of the residual gases in the liquid metal. To achieve this the

aluminium stars are properly secured with 20 MS rod. Generally two Aluminium stars

of 450 gms. each are plunged. On rare occasion, if metal is dull with slag generation, 3

stars are plunged.

The M.S. Road must be three meters minimum. The ends must be properly bent and

wound to the stars so that they do not get detached half-way through while plunging

inside the metal. For proper assimilation of aluminium, the stars must reach the bottom

of the ladle.

The operator must be swift and not slow. At one stroke, the aluminium stars must reach

the bottom. The rod should be held for a few seconds before it is withdrawn. Once the

rod with aluminium stars touches the bottom, it should not be taken up and down. To

achieve this, the rods must be cut to proper size. Initially, it can be of 5 mtrs length and

can be used till the length comes down to 3 metres. At 3 metres length, the rod must be

discarded. Improper aluminium plunging will give rise to pinholes, slag patches on

wheel surface and fine cracks below the slag patches.

15

Tap Changing Sequence

SlNo

CumulativeTime from Power On

IncomingVoltage

(ON Load)

Taps Remarks

1 0 -1Min T6 Power on T6 for one min. Put off the furnace with all the three electrodes resting on the scrap. Adjust the electrodes to appropriate length.

2 2 to 7 Min T6 Power on for another 5 mins on T6, to ensure that electrodes bore in to the furnace. This is to safeguard the roof from the flaring arcs of the electrodes and to improve the life of roof.

3 7 to 50 Mins

<9KV T1 Change to T1/T2/T3 depending upon incoming voltage. Select the Tap in such a way that with current setting is at 19-20 KAmps, Wattmeter reading should indicate between 8000-9000Kwh (8-9Mwh). This is necessary because 70% of RWF scrap is HMS. With this current and Tap setting, HMS scrap on the sidewall of the furnace will also get heated up and collapses in time and the melt down temp of the bath is around 1530-1540OC. If the current is kept lower than this, melt down will still take place but melt down temp of the bath will be low. Bath boiling and temp raising problems are experienced delaying the heat. If furnace is operated with max current and highest tap, HMS scrap on the sides of furnace will not get heated up in time. Electrodes bore in to the scrap, superheat the bath at the bottom and cause hearth pitting. Scrap sticking, delays in heat and higher power consumption are the consequences. After 20 mins of arcing, insert O2 lancing pipe through the hole in the slag door and introduce 50% O2 for Oxy assisted melting. After 40-45 mins of arcing, start cutting scrap through slagdoor by O2 lancing.

9 to 10KV

T2

>10 To11KV

T3

>11KV T4

<9KV T1 Continue with the same taps while cutting the scrap through slag door by O 2 lancing. Reduce/Increase the current if necessary, to ensure that the bath temp does not go beyond 1540-1560OC till 90% scrap is melted.

4 50 - 70 Mins

9 to 10KV

T2

>10 To11KV

T3

>11KV T45 70 - 80

MinsT5/T6 First sample S1 is taken at 1540-1560OC. By this time, majority of the scrap will have

collapsed and the sidewalls are exposed. To prevent side wall refractory erosion, shorter arc lengths are preferred. By changing to lower taps, furnace current can be increased, so that arc length is reduced and temp of the bath can be raised faster. Keep full current and start the Carbon boil by injecting O2 through the bath. Slag will become foamy and starts flowing through slag door. Remove oxidising slag thoroughly by C-boil. Max slag has to be removed between 1550-1630OC. This will ensure Phosphorus removal from metal. Second sample S2 is taken at around 1590-1620OC.

6 80 - 95 Mins

Put off the current and cut the remaining scrap by lancing. Recarb/Decarb the bath depending upon S2 reading. Add about 200 Kgs lime to make the second slag .

7 95-100 Mins

T4/T5 Make the slag fluid, add WAP/RSM in to the furnace at around 1640-1650OC. Mix the bath thoroughly

8 100-105 Mins T7/T8/T9

Take the check samples. Ensure bath is uniform before taking check samples

9 105-115/120 Mins

T7/T8/T9

Gradually raise the bath to tapping temp and tap the heat.

16

Tapwise Voltage Details of Furnaces

Tap No

EAF-1 & EAF-2 (Volts)

Remarks EAF-3 (Volts)

Remarks

1 305T/1 is the Highest

Tap. Same power for T/1

to T/4

145

Decreasing power

2 290 163

3 275 180

4 262 197

5 250

Decreasing Power

2076 219 2177 203 2278 188 2379 176 247

10     25711     267 Same power

from T/16 to T/11.

T/16 is the Highest Tap

12     28013     29214     30715     32316     340

17

List of Specifications :

Sl.No. Item PL No. Specification No.

1. Ferro-Silicon 90793201 RWF/M/SPECN-1/004/1987

2. Ferro-Manganese 90790704 RWF/M/SPECN-1/027/1988

3. Silico- Manganese 91210069 RWF/M/SPECN-1/024/1988

4. Graphite Granules 81982896 RWF/M/SPECN-100/2007

5. Aluminium Star 91980021 WAP-M/SPECN-1/058/1994

6. Liquid Oxygen 81040428 IS 309:2005

7. Flour Spar 81980401 RWF/M/SPECN-1/026/1988

18

List of Consumables :

Sl.No. Item PL No. Unit Norms EAR Likely Suppliers1. Ferro-Silicon 90793201 Kg 7.34/MT

of metal1277000 a) Ferromet Marketing

b) RNB Carbidesc) VBC Ferro Alloysd) SNAM Ferro Alloys

2. Ferro Manganese

90790704 Kg 2.5/MT of metal

435000 a) Mython Ferro Alloysb) Impex Ferrotecc) Navabharath Ferro Alloys

3. Silico-Manganese

91210069 Kg 5.34/MT of metal

929000 a) Chattisgarh Electrical Coporation

b) Ferromet Marketingc) Mannet Ispat Alloys

4. Graphite Granules

81982896 Kg 9.11/MT of metal

1587007 a) Graphite Indiab) Jayanthilal & Companyc) Mineral Pulverising Mills Pvt. Ltd., Nagpurd) M/s. HBR Sales Pvt. Ltd.

5. Aluminium Star

91980021 Kg 0.05/MT of metal

8700 a) Century Aluminium

6. Liquid Oxygen 81040428 Nm3 - - a) National Oxygen Limited b) British Oxygen Company c) Prax Air Ltd.

d) Inox Air Producte) Bhoruka Gases Limited

7. Flour Spar 81980401 Kg 0.4/MT of metal

69600 a) Hindustan Produce Company

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