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?