steel making process routes

7/31/2019 Steel Making Process Routes

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Steel making routes

1. Primary route of steel making

o BF Bessemer converter LRF Ingot casting rolling mill (old process)

o BF LD converter LRF CCM rolling mill (new/recent process)

2. Secondary route of steel making

o (Scrap + Iron Ore) open hearth process LRF Ingot casting rolling mill (oldprocess)

o (Scrap + DRI + Hotmetal) EAF LRF CCM rolling mill (new process)

o (Scrap + DRI) Induction furnace LRF CCM rolling mill (new process)


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Route: 1 (old process): BF Bessemer converter LRF Ingot casting

Route: 2 (recent process): BF LD converter LRF CCM

Hot liquid metal

4% C, 0.5-2% Si, 0.5% Mn0.1% P, 0.05% S

Bessemer converter

(Air is blown from

bottom for refining)

Blast furnace

C, Si, Mn, P are totally

removed from the metal

At the end of the process

excess oxygen is removed

by adding deoxidizer

Metal is tapped into the ladle

Ladle is brought to LRF unit

Necessary alloying additionsare made here.In case of carbon steel C, Si

and Mn are addedIn case of alloy steel C, Si,

Mn, Cr, Ni, Mo whichever isrequired are added in LRFTemperature required forcasting is achieved

Sulfur is removed

Ingot Casting


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Comparison between Bessemer and LD converter process

Hot liquid metal

4% C, 0.5-2% Si, 0.5% Mn0.1% P, 0.05% S

LD converter

(Pure Oxygen is

blown from top

lance for refining)

Blast furnace








Necessary alloying additions

are made here.In case of carbon steel C, Si

and Mn are addedIn case of alloy steel C, Si,Mn, Cr, Ni, Mo whichever isrequired are added in LRF

Temperature required forcasting is achievedSulfur is removed

CCM


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Bessemer process LD process

- Air is refining medium - Oxygen is refining medium

- Time required is more (45-60 min, even more) - Time required is less (15-20 min)

- In Acid Bessemer process P can not be removed,

P can only be removed in basic Bessemer process

- P can easily be removed in LD process

- Sulfur can not be removed in Bessemer or LD converter, Sulfur can be removed in LRF unit afterdoing alloying additions.

- CCM is continuous casting machine which is new development over ingot casting

- For CCM / rolling purpose always fully killed steel is required

Route: 3 (old process): (Scrap + Iron ore) open hearth process LRF Ingot casting

Route: 4:(new process): (Scrap + DRI + Hot metal) EAF LRF CCM

Scrap generated from primary route is

feed materialIron ore is source or oxygen

Open hearth process

Pig iron or MS Scrap + Iron ore








Necessary alloying additions

are made here.In case of carbon steel C, Siand Mn are addedIn case of alloy steel C, Si,

Mn, Cr, Ni, Mo whichever isrequired are added in LRFTemperature required forcasting is achieved

Sulfur is removed

Ingot casting


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Route: 5:(new process): (Scrap + DRI) Induction furnace LRF CCM

Solid scrap is melted first by ele. energy,liquid metal will have approx1-2% C, 0.5-1% Si, 0.5% Mn 0.1% P, 0.05% S

Electric Arc Furnace

(Electric energy is for heatgeneration and oxygen is

for refining)

Scrap +

DRI from Rotary Kiln +

Hot metal from blast furnace








Necessary alloying additionsare made here.- In case of carbon steel

C, Si and Mn are added- In case of alloy steel C,

Si, Mn, Cr, Ni, Mowhichever is required

are added in LRF- Temperature required

for casting is achieved- Sulfur is removed

CCM


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EAF IF

- Removal of P is possible - Removal of P is not possible

- Removal of S is done in LRF - Removal of S is done in LRF but in general

practice S removal is not carried out and metal

is directly brought to the CCM unit

- Good quality scrap and DRI are used to

maintain P and S in the required range

- We can use pig iron scrap, MS scrap, DRI and

hot metal in wide proportions

- Use of pig iron scrap and hot metal is restricted

- Only DRI and MS scrap are melted

1. Rimmed steel:

% C is maintained below 0.15%

No or very little deoxidation is done by Ferro manganese These ingots are not used for rolling purpose

Oxygen ppm is around 700-800

2. Semi killed steel

%C is maintained between 0.15-0.3%

Halfly deoxidized steel deoxidation is carried out by Fe-Si or Aluminium

These ingots are not used for rolling purpose

Oxygen ppm is around 150-200

Solid scrap is melted first by ele. energy,liquid metal will have chemistry as per ourrequirement of steel

Induction Furnace(Electric energy is for heat

generation, no refining

takes place)

Scrap +

DRI from Rotary Kiln

C, Si, Mn, are totally





Alloying additions are also carried out in furnace then

metal is tapped into the ladle and brought directly to

CCM

CCM


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3. Killed steel

% C is maintained above 0.3%

If grade requirement of carbon is less, Si and Mn are also present which makes it fully killed

Deoxidizers are Fe-Si and Aluminium

Aluminium is used in less amount, its % in steel should not exceed 0.02%

Theoretical Oxygen ppm should be less than 30, generally 50-70 ppm is maintained This ingots are Ok for rolling / This type of liquid metal is always used for CCM

Si = 0.2% and/or Al = 0.02% ensures that the steel is fully killed

steel making process routes

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