Basics of Steel Making
Transcript of Basics of Steel Making
Customer Technical SymposiumSteelmaking 101
Today’s Topics
Steelmaking Flowline
Blast Furnace
Basic Oxygen Furnace: BOF
Vacuum Degasser
Continuous Casting
Hot Strip Mill
Pickler
Cold Strip Mill
Box Annealing
Temper Mill
Hot Dip Coating Line
Electrogalvanizing Line
Iron Ore
Limestone
Coal
Pellets
Sinter
Crushed
Coke Ovens
Blast Furnace
Slag Molten Iron
Scrap
Lime & Flux
Oxygen
Electric Furnace
Basic Oxygen Furnace
Steelmaking Flowline
Artwork: American Iron and Steel Institute
Steelmaking Flowline
Continuous Casting
Ladle Metallurgy
Temper Rolling
Slab Hot Strip Pickling
Annealing
Cold Strip
Coating
Artwork: American Iron and Steel Institute
Basic Steelmaking Flow
COKE OVENS
BLAST FURNACEBASIC OXYGEN
FURNACECONTINUOUS CASTER
HOT STRIP MILLCOLD STRIP MILL PICKLING
TEMPER MILL COATING LINE
SHIPPING
SHIPPING
ANNEALING
SHIPPING SHIPPING
Recipe
Blast Furnace
IRON ORE +
LIMESTONE +
COKE +
HOT AIR
Blast Furnace Raw Materials
COKE
CRUSHED
SINTER
PELLETS
Blast Furnace
Input• Iron ore, coke, limestone and heated air
Output• Molten Iron (‘Pig Iron’) is cast into Torpedo Cars
• Transferred to Basic Oxygen Furnace (BOF)
Metallurgy • Chemical reactions cause heating, reduction and melting• Impurities separate and float on top of the molten iron as ‘slag’
Blast Furnace
COKE (carbon) + OXYGEN CARBON MONOXIDE + HEAT
C+O2 CO + HEAT
IRON ORE + CARBON MONOXIDE IRON + CARBON DIOXIDE
FeO + CO Fe + CO2
LIMESTONE “SLAG” - LIQUID BLANKET - FLOATS ON IRON BATH
Blast Furnace
Basic Oxygen Furnace: BOF
Input• Molten iron, scrap, and high purity oxygen
Output• Molten steel is tapped into a ladle
• Transferred to the Continuous Caster after chemistry adjustments or vacuum degassing
Metallurgy • Impurities are oxidized and some separate / float on top of the molten steel as slag
OXYGEN + CARBON CO + HEAT
OXYGEN + MANGANESE MnO (SLAG)
OXYGEN + PHOSPHORUS P2O5 (SLAG)
OXYGEN + SILICON SiO2 (SLAG)
Basic Oxygen Furnace: BOF
Basic Oxygen Furnace: BOF
Vacuum Degasser
Input• Molten steel from basic oxygen furnace (BOF)
Metallurgy • Vacuum degasser snorkels inserted into ladle of molten steel
• Argon gas siphons molten steel through a vacuum chamber• Dissolved gases and carbon are removed
Output• Ultra-low carbon steel
• Transferred to the Continuous Caster
To VacuumPump
Ladle
Inert Gas Inlet
Continuous Caster
Input• Molten steel from ladle is transferred into a holding vessel (tundish) on top of the Continuous Caster
• The tundish continuously meters molten steel into a water-cooled, oscillating mold via a Submerged Entry Nozzle (SEN)
Output• Solid slabs are torch-cut
• Slabs transferred to Hot Strip Mill for Rolling
Continuous Caster
Hot Strip Mill
Input• Slabs from the Continuous Caster are reheated and placed on a rolling table
• Six roughing mill stands reduce slab’s thickness to 1.25” - producing a bar
• The bar is sent through seven additional 4-high finishing mill stands to further reduce thickness
Output• Hot bands from <0.1” to 0.375” thick
• Transferred to Pickler or shipped to Customer
Hot Strip Mill
Pickler
Input• Hot bands of steel are processed through a chemical bath to remove surface oxides
Output• Pickled (Oiled) Band - free of
surface rust and scale
• Transferred to Cold Mill or Shipped to Customer.
Cold Strip Mill
Input• Pickled Bands are rolled through five mill stands (4 or 6-High)
Output• Cold Roll ‘Full Hard’ coils with proper thickness and surface finish
• Transferred to Box Annealing, Hot Dip Coating Line or shipped to Customer
Box Annealing
Input• Cold rolled ‘Full Hard’ coils are stacked, covered and a non-oxidizing atmosphere is introduced
• A furnace is lowered over the cover and fired to a prescribed cycle of time and temperature
Output• Annealed steel with improved mechanical properties
• Transferred to Temper Mill
Temper Mill
Input• Annealed coils
Output• Cold Roll steel with continuous yielding, improved flatness and a uniform surface texture
• Thickness typically reduced <1%
• Shipped to Customer or transferred to the Electrogalvanizing Line
Hot Dip Coating Line
Input• Coils are welded together for continuous processing
• Continuous annealing in-line
• Continuous coating on both sides – Zinc or Aluminum
Output• Hot Dip Galvanized, Galvannealed or Aluminized steel
• Shipped to Customer
Electrogalvanized Line
Input• Cold Roll (Box Annealed & Tempered) coils are welded together and continuously processed through the line
• Plating cells use electric current to apply zinc to the steel
Output• Electrogalvanized
steel
• Shipped to
Customer
Electrogalvanized Line
Questions?