A Brief History of Steel&

The Mysterious Eutectic

Kenneth Newell Ph.D.

Man, Fire & Rocks

Fire Heated Silcrete Stone WeaponsSouth Africa 75,000 BC

South Africa’s Wonderwerk CaveLatest findings show humans controlledfire 1 Million Years Ago

Flint use is well established by 250,000 BC

Kenneth Newell Ph.D.

Limitations of open Fire

• Open air wood fire generally limited to 600oC.

• By 4500 BC, convection fed charcoal pottery kilns could achieve 1100oC to 1150oC

• Copper smelted from malachite was most likely discovered by ancient potters using clay firing kilns

• 4 acres of forest were needed to smelt a 60 lb ingot of copper.

Kenneth Newell Ph.D.

Discovery of Metal Bearing Rocks

Currently there are 86 known metals. Prior to 13th Century, only 7 metals were known:

(1) Gold - 6000BC (2) Copper - 4200BC (3) Silver - 4000BC (4) Lead - 3500BC (5) Tin - 2500BC (6) Iron - 1500BC (7) Mercury - 750BC

Malachite (57%Cu) Chalcocite (80%Cu)

Cassiterite (75%Sn)

Kenneth Newell Ph.D.

Discovery of the Alloy

• 3000 BC, the Sumariansmake the first bronze alloy adding crushed cassiteriteto malachite and charcoal

• At only 1000oC in a pottery kiln, the first molten (castable) metal alloy was produced.

• 10%Sn-90%Cu is still the base Bronze Alloy used today.

• Tensile Strength 45ksi• Charcoal, Tin & Copper

become essential trading commodities.

Kenneth Newell Ph.D.

The First Raw Material Shortages

• By 2000 BC, supplies of alluvial Tin are nearly exhausted,

• Charcoal production completely wipes out Aegean Cyprus forests,

• Bronze production all but stops for 300+ years.

• By 1500 BC, Phoenicians' corner the market on Tin from British Isles and Spain

• Not till 55 BC, Julius Caesar invades British Isles and takes control of Tin supply from Cornwall

The Ancient Tin TradeKenneth Newell Ph.D.

Iron, Armament for the MassesThe transition to the Iron age was critical not because of any property of the metal itself, but rather because iron was infinitely more abundant than copper and tin. This enabled, for the first time in history, true mass-production of weapons.

Kenneth Newell Ph.D.

Discovery of Solid State Iron Bloomery

• About the time of the bronze shortage, 2000 BC, it is believed that either the Persians or the Turks smelted the first Iron ingot from iron ore.

• Using a bellow-driven charcoal kiln fire, an “Iron bloom” was formed at around 1150oC (400oC below Fe melting point 1538oC)

Magnetite (Fe3O4) 73%FeHematite (Fe2O3) 69% FeGeothite (FeO(OH)) 62% Fe

Kenneth Newell Ph.D.

The Critical Role of Charcoal

• Ancient metal smiths were baffled by the Iron-Charcoal interaction.

• Charcoal appeared to make the fire burn hotter and therefore the added heat believed essential for making good iron.

• In reality, hot air and carbon from the charcoal were producing an exothermic reaction.

2 C + O 2 → 2 CO

The resulting carbon monoxide reduced iron oxide to high purity “Wrought Iron”

3 CO + Fe 2 O 3 → 2 Fe + 3 CO 2

• By compacting the bloom into an ingot, metal smiths unknowingly hammered carbon into the wrought iron and produced the first variations of carbon steel.

Kenneth Newell Ph.D.

Iron-Carbon Phase Diagram

Body Center Cubic (BCC)

Face Center Cubic (FCC)

Eutectoid

Eutectic

Kenneth Newell Ph.D.

Interstitial Carbon likes Octahedral Sites

Stable Unstable

Kenneth Newell Ph.D.

Cannons Spark the Industrial Revolution

• In 1543, Henry VIII commissions Cast Iron Cannons rather than the Bronze to mass produce cannons for the Tudor navy.

• The commission for mass production was the first government works program for modernization.

• Over the next 250 years, The British nearlyperfected a Two Step iron making process.

Kenneth Newell Ph.D.

The Two Step ProcessStep 1 – The Blast Furnace smelting to make “Pig Iron”

• The blast furnace is used to melt Iron ore at 1350oC (still 200oC below Fe melting point 1538oC)

• Water power harnessed to drive bellows for forced air.

• Limestone introduced for “slag” removal of silicon dioxides.

• The molten iron is poured into ingots called “Pig Iron”.

• Resulting Iron contains 3.5 – 4.5% Carbon.

• Production rate of 1 ton of cast iron every two hours is possible.

• In 1584, Parliament introduces laws restricting the building of any additional furnaces to slow deforestation in the making of charcoal.

Kenneth Newell Ph.D.

Blast Furnace makes Pig Iron•Carbon from charcoal is absorbed by solid state diffusion into FCC Austenitic iron crystal structure.

•At approximately 1% Carbon, a super solidus phase begins and the absorption of carbon accelerates with liquid iron phase.

•Within minutes, without additional heating, all the iron melts at 1.75%C

•Carbon continues to be absorbed at high rate until the temperature falls below 1130oC

Limestone added to molten iron to “slag out” Silicon and Oxygen

Kenneth Newell Ph.D.

The Two Step ProcessStep 2 –Puddling Furnace refining to make “Wrought Iron”

• The Reverberatory Furnace is introduced in the 1670s to melt Bronze using “coke” from coal rather than charcoal.

• By 1768, the Reverberatory furnace is adapted to iron processing and is called the Puddling furnace because the puddling effect of molten iron becoming semi-solid as it is heated.

Eiffel tower was built using 7,300 tonnesof Puddled Iron

Kenneth Newell Ph.D.

Puddling Furnace makes Wrought Iron

• Using Coke to generate heat and produce an oxidizing atmosphere, Pig Iron is melted.

•When the pig iron ingots melt, iron oxide is added and the molten iron boils into a sponge-like puddle as the carbon content decreases.

•The Puddler removes chunks of puddled iron sponge and forges it into a wrought iron plate.

•The making of steel remains an art till 1856.

Iron Oxide addedto molten pig iron

Kenneth Newell Ph.D.

Bessemer’s Cannon• At start of Crimean War, Henry

Bessemer invents a spinning projectile to be fired from smooth bore cannons.

• The projectile causes cast iron cannons to explode.

• Henry recognizes that the addition of iron oxide in the puddle is the same as driving air through the molten pig iron.

• Henry invents the Bessemer Converter which forces air through the molten pig iron enabling the controlled removal of carbon.

• By 1867, together with the recently invented Watts steam engine, the Bessemer Converter made it possible to produce steel quickly, and cheaply

Kenneth Newell Ph.D.

Conversion of Pig Iron to Steel

Kenneth Newell Ph.D.

Steel Rail Changes the World

• 1867, 460,000 tons of wrought iron rails were made and sold for $83/ton, 2550 tons of Bessemer steel rails were sold for $170/ton.

• By 1884, 1.5Million tons of steel rail are sold at $14/ton.

• Rail life increases from 2 yrs to 10 yrs while maximum bearing strength increases from 8 tons to 70 tons

• Today there are 3500 different grades of steel.

• It would now require 1/3 the amount of steel to build the Eiffel Tower.

Kenneth Newell Ph.D.

The Samurai Martensitic Katana• Around 900AD, the Japanese develop a

steel heat treating technique that won’t be fully understood for another 1000 years.

• By rapid quenching a forging from 800oC, austenite is transformed to martensite and is then tempered to a precise hardness.

• Use of clay on the blade produces the wavy “hamon” which focuses the heat treatment only on the cutting edge.

• The sword curves during the heat treatment due to the differential strain between the hard martensite phase and the tough pearlite phase.

Kenneth Newell Ph.D.

Heat Treating Martensite

Rapid Quenching

Tempering

Kenneth Newell Ph.D.

Eng Yeap’s 1640 Samurai Katana

http://www.japaneseswordcollector.com/echsek/echsek.html

Kenneth Newell Ph.D.

The Mystery of Wootz Steel• Around 300BC, India starts exporting

unique hockey-puck sized iron ingots to Syria.

• Damascus blade smiths learned to forge superior swords with a surface pattern of alternating dark & light phases.

• The technology survived over 2000 years and then was lost in the 1800s.

• Only recently using modern analysis was it determined that Wootz Steel was a complex hypereutectoid alloy with an array of alloying elements.

Fe-1.5C-P-Cu-V-Ni-Mn

Wootz Steel Ingots

Bands of cementite Fe3CKenneth Newell Ph.D.

Wootz Steel & NanoTubes

• 2006, University of Dresden using high-resolution transmission electron microscopy prove Damascan Blades contained CementiteNanowires form in situ with Vanadium during cyclic forging.

Kenneth Newell Ph.D.

Damascan Heat Treatment

Kenneth Newell Ph.D.

Steel enables 1 person to feed 1000s

The second agricultural revolution coincided with the Industrial Revolution; it was a revolution that would move agriculture beyond subsistence to generate the kinds of surpluses needed to feed thousands of people working in factories instead of in agricultural fields. Bessemer’s invention of cheap steel was the cornerstone of both revolutions.

Kenneth Newell Ph.D.

How important is Steel?

Kenneth Newell Ph.D.