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Steel making routes 1. Prim Primar ary y route route of ste steel el mak making ing o BF Bessemer converter LRF Ingot casting rolling mill (old process) o BF LD converter LRF CCM rolling mill (new/recent process) 2. Secon Secondar dary y rout routee of ste steel el maki making ng o (Scrap + Iron Ore) open hearth process LRF Ingot casting rolling mill (old process) proces s) o (Scrap + DRI + Hotmetal) EAF LRF CCM rolling mill (new process) o (Scrap + DRI) Induction furnace LRF CCM rolling mill (new process)
Route: 1 (old process): BF Bessemer converter LRF Ingot casting
Blast furnace Hot liquid metal 4% C, 0.5-2% Si, 0.5% Mn 0.1% P, 0.05% S
Bessemer converter (Air is blown from bottom for refining) 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 additions are made here. In case of carbon steel C, Si and Mn are added In case of alloy steel C, Si, Mn, Cr, Ni, Mo whichever is required are added in LRF Temperature required for casting is achieved Sulfur is removed
Ingot Casting
Route: 2 (recent process): BF LD converter LRF CCM
Blast furnace Hot liquid metal 4% C, 0.5-2% Si, 0.5% Mn 0.1% P, 0.05% S
LD converter (Pure Oxygen is blown from top lance for refining) 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 additions are made here. In case of carbon steel C, Si and Mn are added In case of alloy steel C, Si, Mn, Cr, Ni, Mo whichever is required are added in LRF Temperature required for casting is achieved Sulfur is removed
CCM
Comparison between Bessemer and LD converter process
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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 easily be removed in LD process P can only be removed in basic Bessemer process Sulfur can not be removed in Bessemer or LD converter, Sulfur can be removed in LRF unit after doing 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 Pig iron or MS Scrap + Iron ore Scrap generated from primary route is feed material Iron ore is source or oxygen
Open hearth process 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 additions are made here. In case of carbon steel C, Si and Mn are added In case of alloy steel C, Si, Mn, Cr, Ni, Mo whichever is required are added in LRF Temperature required for casting is achieved Sulfur is removed
Ingot casting Route: 4: (new process): (Scrap + DRI + Hot metal) EAF LRF CCM
Scrap + DRI from Rotary Kiln + Hot metal from blast furnace Electric Arc Furnace (Electric energy is for heat generation and oxygen is for refining) Solid scrap is melted first by ele. energy, liquid metal will have approx 1-2% C, 0.5-1% Si, 0.5% Mn 0.1% P, 0.05% S 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 additions are made here. In case of carbon steel C, Si and Mn are added In case of alloy steel C, Si, Mn, Cr, Ni, Mo whichever is required are added in LRF Temperature required for casting is achieved Sulfur is removed
CCM
Route: 5: (new process): (Scrap + DRI) Induction furnace LRF CCM
Scrap + DRI from Rotary Kiln
Induction Furnace (Electric energy is for heat generation, no refining takes place) Solid scrap is melted first by ele. energy, liquid metal will have chemistry as per our requirement of steel C, Si, Mn, are totally removed from the metal At the end of the process excess oxygen is removed by adding deoxidizer
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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EAF Removal of P is possible Removal of S is done in LRF
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We can use pig iron scrap, MS scrap, DRI and hot metal in wide proportions
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IF Removal of P is not possible 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 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 F e-Si or Aluminium • These ingots are not used for rolling purpose • Oxygen ppm is around 150-200 •
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 •
