Introduction to Materials and Human History

• Materials engineer perspective on taking materials for granted
• Human history periods named after materials: Stone Age to Space Age
• Materials significance in everything we build
• Previous coverage of aluminum and silicon
• Focus on Iron Age as most influential period

Early Iron Use and Meteoric Origins

• Earliest iron evidence: 3,500 BC Egypt - iron beads from meteors
• Meteoric iron highly prized due to "heavenly association"
• Tutankhamun buried with meteoric iron dagger
• Meteoric iron only naturally occurring source initially
• Iron reacts readily with oxygen forming iron ore
• No oxygen in space - meteors delivered usable iron to Earth
• Humans lacked technology to extract iron from ore initially

Iron Age Timeline and Regional Variations

• Iron Age began at various points worldwide
• Humans learned to extract iron from ore
• End dates vary between regions
• Britain: Iron Age 800 BC - 43 AD (Roman invasion)
• Roman invasion marked start of Roman age
• Argument: Iron Age lasted until 150 years ago when steel mass-produced

Iron vs Steel Composition and Properties

• Iron Age actually used steel as best materials
• Iron and steel mostly same material
• Main difference: carbon content
• Cast iron: above 2% carbon content
• Higher carbon = harder, less ductile material
• Cast iron: very hard but very brittle
• Rod iron: less than 0.8% carbon
• Rod iron: much better for structural applications, ductile, bends under loads without breaking
• Steel: 0.8-2% carbon content
• Steel: ideal balance between hardness and ductility
• Iron history defined by ability to control carbon content

Iron's Abundance and Corrosion Issues

• Iron: 4th most common metal on Earth surface (below aluminum)
• Reacts readily with oxygen forming iron oxide ores
• Rust = one form of iron oxide
• Constant struggle in structural maintenance
• Eiffel Tower painted 17 times since construction
• Every 7 years: ~60 tons paint applied to Eiffel Tower
• Paint color changes over time:
  • Originally Venetian red
  • Yellowish brown to chestnut brown
  • Current specially mixed "Eiffel Tower Brown" adopted 1968
• Iron doesn't exist on planet surface in usable form due to oxygen reaction

Early Iron Production - Bloomeries

• Mid Bronze Age: first signs of iron production
• Early iron smelted in bloomeries
• Primitive Technology YouTube channel created miniature version
• Process: heat iron ore using charcoal as heat source
• Burning charcoal produces carbon monoxide
• Carbon monoxide reacts with iron oxide forming carbon dioxide + iron
• Bloomery heated above melting point of impurities, below melting point of iron
• Heavier iron consolidates at bottom
• Impurities form molten pool called "slag" - drained away
• "How to Make Everything" YouTube channel covered this process
• Removed iron = porous mixture of impurities and iron
• Worked with hammer to consolidate iron, beat off waste material
• Result: rod iron with very low carbon content
• Bloomeries produced very small quantities of iron
• Water wheel introduction allowed larger bloomeries while maintaining high temperature

Bloomery Impact on Society

• Revolutionized human life beyond military advantages
• Iron ore much more common than copper/tin (Bronze Age materials)
• Iron produced in many areas
• Communities made own tools/weapons without importing materials
• Iron plows: stronger, heavier
• Farmers plow land quicker, grow more food
• Single farmer could feed more people
• More people dedicated to different trades
• Society becoming more stratified
• Trade increasing
• Acceleration continued with better iron refining methods

Blast Furnace Innovation

• Dramatically increased iron production
• Name from heating method: preheated air ~1,000°C blasted through nozzles near base
• Heat iron above melting point with flux materials
• Flux: chemical combining with impurities for easy extraction
• Iron ore mixed with limestone and coke
• Coke: refined coal with very little impurities
• Works similar to charcoal in bloomeries
• Produces carbon monoxide when burned
• Carbon monoxide reacts with oxygen in iron ore
• Heat decomposes limestone into calcium oxide + carbon dioxide
• Calcium oxide reacts with silica impurities forming calcium silicate
• Impurities form liquid slag layer floating on heavy molten iron
• Slag drained away, heavier molten iron tapped lower down
• Allowed vast quantities of ore converted to iron quickly
• Drawback: higher temperatures cause iron to absorb carbon readily
• Result: cast iron with very high carbon content

Fining Process - Reducing Carbon Content

• Extra step needed to decrease carbon content from blast furnace iron
• Process called "fining"
• Multiple methods available:
  • Refinery method: cast iron heated back up, oxidizes carbon, beaten with hammer to remove oxidized carbon, repeated until rod iron produced
  • Crucible steel: mixing rod iron + cast iron in sealed crucible, prevents carbon from air entering, low carbon rod iron + high carbon cast iron = steel
  • Puddling furnace: heating cast iron in furnace separating fuel and iron, heat radiates through furnace liquefying iron, worker stirs to encourage oxidation of impurities
• All methods fuel and labor intensive
• End product too expensive for general industrial use
• Puddling furnace worker average life expectancy: 30 years (toxic fumes)

Railroad Expansion Pressure

• Early 19th century railroad expansion
• Pressure to develop faster, cheaper steel production method
• Modern rail tracks made from high strength steel
• Steel's superior hardness over rod iron resists wear
• Difference shown between worn steel rail vs new one
• Rod iron wear so quick: certain popular line sections needed replacement every 6-8 weeks
• Steel superior strength over rod iron allows carrying more load
• Rail shape helps carry even more load
• Mass production method critically important

Bessemer Process Revolution

• British metallurgist Sir Henry Bessemer designed converter
• Molten iron poured from blast furnace
• Hot air passed through bottom
• Oxygen in air oxidizes impurities in iron
• Carbon reacts forming carbon monoxide (expelled as gas)
• Silicon and manganese oxidize forming slag layer
• Process very fast
• Early problem: removed too much carbon, left too much oxygen
• Solution: added alloy called "spiegeleisen" (iron + carbon + manganese)
• Manganese reacts with oxygen removing it
• Carbon increases carbon content as needed
• Another early problem: didn't remove phosphorus from iron
• High phosphorus concentrations make steel brittle
• Initially only usable with low phosphorus concentration ores (scarce, expensive)
• Problem solved by Welshman Sydney Gilchrist Thomas
• Discovery: adding chemically basic material (limestone) draws phosphorus into slag

Steel's Economic and Industrial Impact

• Cheap steel availability caused explosion in rail industry growth
• Steel vital to daily lives
• Often considered measure of country's economic success
• High steel production = high steel demand = country building infrastructure
• Graph showing China's steel production 1990s-present
• Demonstrates China's rapid rise as global superpower during economic reform
• Without steel: buildings couldn't reach current heights
• Bridges like Golden Gate Bridge wouldn't be possible

Future Topics and Japanese Metallurgy

• More to learn about steel's fascinating history
• Japanese expert blacksmiths creating katana
• Learned to control crystalline structure of steel
• Forged perfect blade
• Topic for another video

Personal Memorial and Charity Appeal

• Video was last for 2016
• Thanks to viewers for incredible year
• Plans for 2017
• Memorial message for cause close to heart
• Two years ago: best friend Tom died in car crash in Malaysia
• Family set up memorial fund for Nepal Youth Foundation
• Nepal: incredibly beautiful country with problems
• One of highest infant mortality rates in world
• Problems: internal conflicts, earthquake, lack of social welfare
• Many orphans in country
• Nepal Youth Foundation: provides shelter, food, medical aid, education to young people
• Recorded conversation with Tom about teaching English in poor countries
• Tom's ambition to make positive impact through education
• Tom never fulfilled ambitions but narrator did
• Donating 2,000 Euro to Nepal Youth Foundation
• Hope for matching donations
• Tom volunteered in Nepal orphanage
• Constantly spoke about caring for Nepal people
• Tom encouraged narrator to pursue dreams
• Positive attitude rubbed off during needed time
• Wouldn't have left job without shock of Tom's death
• Realization: life too short for non-passionate work
• Hope for positive impact on Nepal young people
• Tom had positive impact on every person he met