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Dr LJ Erasmus

June 2013

History of Iron

Part of the unrecorded history of man

Known as “Metal from heaven”Assyrians – parzilla

Babylonians – barza

Sumerians – barzel

Prehistoric implementsMain source - meteorites

2 – 26% nickel

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Largest meteorite

Hoba

Meteorite

66 tons

Grootfontein

Namibia

84% Fe; 16% Ni

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Willamette Meteorite in Oregon

15 ton,

6th largest

in the world

91% Fe; 9% Ni

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History

First evidence of man made iron (low Ni)

Ur of the Chaldeans (Iraq) 3100 BC – an iron dagger

Egypt 2900 BC– an iron tool between two pyramid stones

Egypt 2600 BC – in a grave in Abydos

Crete 1800 BC – in a grave in Knossos

Greece 1550 BC – an iron finger ring

First known iron working furnaces

Gerar (Palestine) 1200 BC

Hittites are credited with commercialising iron smelting

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The Hittite Empire

Also known as

Chaldeans/Babylonians / Syrians

Bronze Age people

North-central Anatolia

18th century BC

Commercialising iron smelting

Iron artefacts from 14 BC

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Iron

Chalybes tribe in the Hittite Empire

Iron known as Chalybs

Modern city Aleppo

Hittite empire destroyed by the Sea People were

responsible for spreading the knowledge

Ending the bronze age, starting the early iron age

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Primitive furnaces did not

reach temperature

sufficient to melt iron

(1535°C).

Hittites learned that

“carburizing” the iron

substantially reduced its

melting point.

This was done by running

the furnace with a 6-fold

excess of charcoal.

Today, we can understand

this effect from the iron-

carbon phase diagram.

The Empirical Discovery of

the Effect of Carbon

Cast Iron

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The First Recorded Energy Crisis

Carbon-rich iron can be melted and poured at 1130°C

Cast iron or pig iron. But…

It takes about five tons of wood to make one ton of charcoal.

Rapid deforestation.

The availability of wood resulted in an energy crisis.

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Evolution of Iron Know-how

Wrought iron - Oldest iron product

A pure form of iron

First produced ≈ 4000 years ago

– Fibrous structure

– Can be shaped by hammering / rolling

Cast Iron

Alloy of iron and carbon (up to 5% carbon)

First produced commercially ≈14 BC

– Cannot be shaped, is casted in molds

– Grey of white

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Iron alloys

Steel – alloy with various alloying elements

Small quantities in the ore - made accidently

Hardenable upon quenching

Commercialised in the Bessemer process – 1856

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Carbon

This mystery was only solved around 1800 AD

Sven Rinman (Swedish metallurgist)

– The history of iron (1782)

– Special character of steel

• Phlogiston ≡ “anI-oxygen”

We now know that iron exhibits Allotropy

Several temperature dependent crystal structures

with various degrees of carbon solubility

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Iron making in Ancient China

Chinese iron making also initially relied on wood. (Technology transmitted from Hittites)

Some Chinese iron making sites began to use anthracite.

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Iron-making in 14th Century Europe

Carbon saturated metal was produced in a

blast furnace with charcoal

Cast in sand

Solid state re-heat and refined – Wrought iron

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Iron-making in 17th-Century England

English iron-makers used charcoal from oak as the fuel of choice in smelting.

As in the past, the increased demand for iron led to extensive cutting of oak forests.

In this case, there was also a competing application for oak: naval vessels.

War is more important

Introduction of coal Hot shortness making the iron brittleAn advantage if you produce cannon balls

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Oak

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Hot Shortness

With the switch to coal, iron pieces would tear or break apart when being worked at high temperature.

This problem was called hot shortness, or sometimes “hot shorts.”

This is due to precipitation of FeS as the molten Iron solidifies.

FeS segregates in grain boundaries and causes sites of weakness.

Heat treatment of coking coal into cokeCoke became the dominant fuel for iron smelting.

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A short history of Iron production

Iron makingBloomery – sponge iron;

Blast furnace – pig iron

Steelmaking Crucible steel

Tatara furnace

Bessemer converter – to 1868

Basic oxygen processVoest-Alpine in 1952

Mini-millElectric arc furnace

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Bloomery

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Bloomery

Modern replica

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Evolution of The Blast Furnace

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Bessemer converter

1855

Sheffield

Air blown

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Iron Ores

Iron-Carbon-Oxygen equilibrium

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Iron ore reduction with CO is exothermic and

therefore the reaction temperature is relatively

easy to sustain.

Fe2O3 + 3CO → 2Fe + 3CO;

∆H298K = -49.9 kcal/kg Fe

Iron ore reduction

The Blast Furnace

The Blast Furnace Process

500-600°C

600-900°C

900-1100°C

>1100°C

1100°C

1150°C

1450°C

1500 oC

Fe2O3

Fe3O4

FeO

Fe (+ C)

Fe

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Direct Reduced Iron - DRI

Midrex

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Corex

HYL process

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Direct Iron Ore Smelting (DIOS)

Cyclone Converter furnace (CCF)

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High Intensity Smelting (HISMELT)

American Iron and Steel Institute

(AISA)

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Alloystream

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Ess

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