Gather process and analyse information and use the available evidence to relate
the chronology of the Bronze Age, the Iron Age and the modern era and possible
future developments.
The desire to use and improve the technological application of metals is one of the
oldest of the applied sciences. Its history can be traced back to 6000 BC. Admittedly,
its form at that time was rudimentary, but Process Metallurgy has sign posted history
and its documentation has provided insights into the progress of civilization. While
the initial usage of metals was predominately for weaponry and jewellery,
contemporary society is now inventing more practical utilizations ranging from
structural engineering to electronics that define our current stage of technological
advancement. Currently there are 86 known metals. Before the 19th century only 24
of these metals had been discovered and, of these 24 metals, 12 were discovered in
the 18th century. Therefore, from the discovery of the first metals - gold and copper
until the end of the 17th century, some 7700 years, only 12 metals were known. Four
of these metals, arsenic, antimony , zinc and bismuth , were discovered in the
thirteenth and fourteenth centuries, while platinum was discovered in the 16th
century. The other seven metals, known as the Metals of Antiquity, were the metals
upon which civilisation was based. These seven metals were:
(1) Gold (ca) 6000BC
(2) Copper,(ca) 4200BC
(3) Silver,(ca) 4000BC
(4) Lead, (ca) 3500BC
(5) Tin, (ca) 1750BC
(6) Iron,smelted, (ca) 1500BC
(7) Mercury, (ca) 750BC
There are a number of reasons that contribute to the development of the Bronze Age,
the Iron Age and the modern era, and to their chronological order. These explanations
include the chemical activity series of the elements, religious worship, availability,
warfare and civilisation.
The activity series of metals lists in order the reactivity of metals from most to least
reactive as follows:
Li, K, Na, Ba, Ca, Mg, Al, Zn, Cr, Fe, Co, Ni, Sn, Pb, Cu, Ag, Hg, Pt, Au.
This means that Lithium (Li) is the most reactive and Gold (Au) is the least reactive.
Evidence of this is that Gold is found in its elemental state in nature while Lithium is
never found in its pure state being always found in compounds with other elements.
Metals with high reactivity join with other elements to form extremely stable
compounds, which require large amounts of energy to break their bonds, as they
release a large amount of energy when they react. Therefore the more reactive an
element is, the more stable a compound it forms and the harder it is to extract it from
its ore. The main technological achievement that heralded the next age in metal
extraction was the ability to make progressively hotter fires needed to supply the
energy that would break these progressively stronger bonds.
The first metal to ever be extracted from its ore was copper when the smelting of
rocky ores produced a metal referred to as copper ‘globules’. This process was first
discovered by Neolithic people in the near East around approximately 6000BC when
they unintentionally heated this ore with carbon whilst cooking over large fires.
Copper is naturally a soft metal which limited its uses to ornaments and basic utensils.
The Copper Age (3500 – 2300 BC), is also referred to as the Early Bronze Age.
Sumerian documents unearthed in Mesopotamia and dated to circa 3500BC reveal
that the ancient Egyptians had extracted copper from what was believed to be
malachite (a copper hydroxy carbonate, CuCO3.Cu (OH)2 ), an abundant mineral in
Egypt. During their experimentation with the smelting of copper the Egyptians
realised that temperatures exceeding 800oC were needed if the extraction process was
to be effective.
Nevertheless, during this time the casting of copper objects was a complicated process
due to the development of gas bubbles when the metal was being poured and its
susceptibility to shrinking when in the cooling stage. The desired form was shaped by
hammering the copper object till it cooled down which increased the hardness of the
metal. Although a comparatively soft metal, it was more durable and effectively
harder than gold. This allowed Egyptians to produce convenient tools such pins,
fishhooks and fancy jewellery.
Uses of copper:
Copper objects created during the copper age:
Around 3000 BC in the Middle East, metal-smiths came to the realisation that harder
metal alloys could be developed using copper in closed-furnace smelting. The first
bronze alloy made was called arsenic bronze which was an alloy of copper and
arsenic. The arsenic helped to produce a more durable, stronger product which was
favoured over pure copper. Copper was often found contaminated with arsenic, lead,
nickel and bismuth, and through further experimentation, it became evident that tin
produced the most effective alloy with copper. Tin bronzes contained about 10% tin
and were more ductile than arsenic bronzes. Tin metal was extracted from tin ores
such as Cassiterite (SnO2) through the process of smelting. The purified tin was then
melted with copper in a furnace to produce molten bronze. Tin bronzes were more
malleable than copper and were easily sharpened. Cutting tools and weaponry were
then created from tin bronzes. In most cases bronze was utilised for worshipping the
gods, hunting, creating huge statues and ornaments. Significantly kings and emperors
included this metal in the residences and important political settings. Hence the
Bronze Age led to the genesis of the Classical civilisations which unfurled in the
Mesopotamia and Egypt. The availability of superior bronze weapons meant that
nations which possessed bronze technology had an advantage when conquering their
less well equipped neighbours thus allowing imperialist expansion to occur.
Bronze objects created during the Bronze Age:
The availability of tin ores increased when Egypt and the Middle East initiated trading
with European countries in which tin was more abundant. An expansive trade network
established between the Middle East & Europe extending from Cornwall and reaching
as far as the Armenian territories. The trade networking also hastened advancement in
the processes of extraction and utilisation since metal smiths of the Middle East began
to cooperate with European bronze smiths. Interestingly, the Bronze Age is not
attributed to a specific time frame since some areas had an earlier Bronze Age than
others, while in different areas this Age lasted for a long period. Some regions did not
even experience a Bronze Age. Bronze was a popular metal due to the reliability and
relative ease of its manufacture once the technology matured & as such was
consistently used until 1500 – 1000 BC. It was at this period in time that iron
appeared, particularly in Asia Minor. Interestingly modern archaeologist have noted
that stories of magical swords such as King Arthur’s “Excalibur” are generally dated
to the early Iron Age for the simple reason that bronze sword manufacture was
comparatively easy in comparison to steel sword manufacture. Hence any blacksmith
who could consistently produce high quality steel swords was feted as a wizard eg
“Merlin”.
Iron was first used by Prehistoric tribes around 4000 BC who discovered the precious
metal in meteorites. Tribes men utilised this native iron, also referred to as meteoric
iron by literally breaking off iron from meteorites and forming tools, weapons and
other convenient instruments because iron was harder than bronze weapons, even
though the native iron was not in abundance or conveniently available.
Further development of furnace technology for the metal purification process
instigated the onset of the Iron Age by permitting metal smiths to create much higher
temperatures in kilns. Because Iron is a harder metal further up the activity series
from copper, it requires temperatures of approximately 1100o C to start extraction.
Some of the first iron-making furnaces were quite shallow and had the schema of
bowl shaped hearths in which metal smiths would heat the iron ore and charcoal. It
would take several hours before the ore would release its oxygen in the hot carbon
which surrounded it and then be transformed into a metal of shiny appearance.
However, this metal was not actually of any use until it was reheated and continually
hammered to squeeze out all the impurities from the metal. This laborious process
was necessary due to the fact that the temperatures achieved were not quite high
enough to truly melt the iron. Around 1400 BC large supplies of iron were produced
by the Hittites in a region now known as Turkey. By 1000 BC, a large number of
civilisations adapted the iron making techniques, thus prescribing this period of time
as definitive of the Iron Age. Needless to say, the processes of smelting and extraction
and moulding were still in the primitive stages. Hand held stones were used to
hammer the iron into shape and iron tongs assisted in holding the piece in place.
Iron objects created during the Iron Age:
The technological breakthrough required for smelting was the invention of the blast
furnace which allowed large scale casting of liquid iron. The Chinese achieved this
first around 100 BC but it would be another 1000 years before the Europeans
discovered this process.
Old Blast Furnace
There were also other problems with the purification process, primarily that iron in its
pure form was not much harder than the earlier bronze counterpart. For this reason,
carburizing was introduced to turn iron into steel. Carburizing was the inclusion of a
small quantity of carbon, from ½% to 2% followed by “quenching” it via sudden
immersion in cold water to turn the iron into a metal which was more suitable for
making weaponry and manufacturing tools. The technology of iron manufacture
drastically evolved societies and their industries. Obviously countries with superior
iron weapons now wielded a significant advantage on the battlefield as demonstrated
by the first western Iron Age Empire belonging to the Romans whose 1st century AD
soldiers were clad in steel “lorica segmentata” armour.
By 700 AD the Europeans had a new process of blowing air into the furnace through
tuyeres which aided in making the fire hotter and which actually improved the quality
of the metal. This was further enhanced when a device called a billows was added to
the process, thus the quality of iron continued to improve. In Catalonia, now referred
to as north-eastern Spain, a more effective hearth furnace was introduced, which
forced air to the bottom by using water power. The Catalan forge could extract
roughly about 150 kilograms of wrought iron in approximately five hours.
With the advent of the blast furnace in Europe around 1300 AD temperatures began
exceeding 1530 0 C which allowed molten iron to be produced. By the 1500’s, Europe
began to flourish economically in part due to the increasing familiarity with methods
of shaping iron in liquid form and utilisation for commercial products. The industrial
revolution of the 18th century resulted in dramatic improvements in the extracting
processes and manufacturing methods of iron and steel.
In the mid 1800’s the genesis of modern steelmaking occurred with the invention of
the Bessemer process which was the first inexpensive industrial process for the massproduction of steel from molten pig iron. The process is named after its inventor,
Henry Bessemer, who took out a patent on the process in 1855. The Process happened
inside the Bessemer Converter, the container in which the steel was made. The
process was independently discovered in 1851 by William Kelly. The process had also
been used outside of Europe for hundreds of years, but not on an industrial scale. The
key principle is removal of impurities from the iron by oxidation through air being
blown through the molten iron. The oxidation also raises the temperature of the iron
mass and keeps it molten. This process was still in use up to the late 1960’s when
further advances finally rendered it obsolete.
The modern era with regard to metal usage has witnessed the application of many
different metals for structural engineering and in the later part of the 20th century,
electronics. However it is most obviously defined by the almost ubiquitous use of
Aluminium on an industrial scale. In fact some commentators have even labeled the
modern era the “Aluminium Age”.
Although aluminium is the most abundant metallic element in the Earth's crust
(believed to be 7.5 to 8.1 percent), it is rare in its free form, occurring in oxygendeficient environments such as volcanic mud, and it was once considered a precious
metal more valuable than gold. Napoleon III, emperor of France, is reputed to have
given a banquet where the most honoured guests were given aluminium utensils,
while the other guests had to make do with gold. At that time, aluminium was more
expensive than silver, gold, or platinum. Aluminium has been produced in
commercial quantities for just over 100 years.
Aluminium is a strongly reactive metal that forms a high-energy chemical bond with
oxygen. Compared to most other metals, it is difficult to extract from ore, such as
bauxite, due to the energy required to reduce aluminium oxide (Al2O3). For example,
direct reduction with carbon, as is used to produce iron, is not chemically possible,
since aluminium is a stronger reducing agent than carbon. Aluminium oxide has a
melting point of about 2,000 °C. Therefore, it must be extracted by electrolysis. In
this process, the aluminium oxide is dissolved in molten cryolite and then reduced to
the pure metal. The operational temperature of the reduction cells is around 950 to
980 °C. Cryolite is found as a mineral in Greenland, but in industrial use it has been
replaced by a synthetic substance. Cryolite is a chemical compound of aluminium,
sodium, and calcium fluorides: (Na3AlF6). The aluminium oxide (a white powder) is
obtained by refining the ore bauxite. Bauxite occurs as a weathering product of low
iron and silica bedrock in tropical climatic conditions.
Aluminium is the most widely used non-ferrous metal. Global production of
aluminium in 2005 was 31.9 million tonnes. It exceeded that of any other metal
except iron (837.5 million tonnes). Relatively pure aluminium is encountered only
when corrosion resistance and/or workability is more important than strength or
hardness. A thin layer of aluminium can be deposited onto a flat surface to form
optical coatings and mirrors. When so deposited, a fresh, pure aluminium film serves
as a good reflector (approximately 92%) of visible light and an excellent reflector (as
much as 98%) of medium and far infrared.
Pure aluminium has a low tensile strength, but when combined with thermomechanical processing, aluminium alloys display a marked improvement in
mechanical properties, especially when tempered. Aluminium alloys form vital
components of aircraft and rockets as a result of their high strength-to-weight ratio.
Aluminium readily forms alloys with many elements such as copper, zinc,
magnesium, manganese and silicon (e.g., duralumin). Today, almost all bulk metal
materials that are referred to loosely as "aluminium," are actually alloys. For example,
the common aluminium foils are alloys of 92% to 99% aluminium.
New light alloys are being developed and employed but with the periodic table being
effectively complete science is now turning increasingly to modern composite
materials such as carbon fibre which are supplanting metals in many areas of
engineering. Hence the future may indeed be labeled the “plastic age”. This
progression in material usage is best illustrated by the example of bicycle technology.
The first practical bicycles became available with the development of tubular steel at
the end of the 19th century. For the next 100 years the main advancements were in the
method of joining the frame together by either lugs or welding. New and stronger
alloys of steel were developed to increase strength. In the 1980’s Aluminium frames
became available due to new manufacturing techniques. With the collapse of the
USSR in the early 1990’s frame builders found the market flooded with ex soviet
stocks of Titanium & Scandium originally intended for the aerospace industry. Today
Carbon fibre frames are supplanting metals in lightweight frames for racing and steel
is making a resurgence for commuting and touring frames where strength is the main
concern before weight.
From this short review of metallurgical developments it can be seen that as the early
metallurgists became more sophisticated their ability to discover and separate all the
metals grew. However in all of their work it was necessary for these basic steps to be
carried out:
1.
2.
3.
4.
the ore had to be identified (usually an oxide of the metal)
separated from gangue
concentrated
Reduced
Reduction of the ore to reveal the pure metal was the major technological hurdle at
the beginning of each new stage. Invention and ingenuity had to be employed to find a
way of supplying the energy required to break the increasing strength of the bonds
formed as mankind worked its way up the reactivity series.
TIMELINE- HISTORY OF METALS

6000BCE- First time copper was extracted from its ore in Egypt

5000BCE- First Egyptian Artefacts

4000BCE- Egyptians wore beads of meteoric iron.
-

Soldering in Mesopotamia
3000BCE- Stone Age Ends
-
Lead used to join copper in Mesopotamia

3600 BCE- Hard Soldering in Egypt

3200BCE- Copper Age Begins

2600BCE- Hard soldering with silver began
-
Hard soldering in Greece

2500BCE- Oldest Bronze artefacts

2300- Beginning of Bronze Age

1500BCE- Silver and copper first used as a means of exchange

1300 BC- Oldest article of Iron found to be from this era

1000 BCE- Physical properties of Gold first refined
–
Beginning of Iron Age

200- Tin extracted in Egypt

10BCE- Ionians Begin to use Iron

1CE – “Modern” Age begins

1880- Alloy Steels such and Manganese Steel and Tungsten Steel used

1886- Aluminium first extracted from its ore

1890- High Speed steel created
-
Nickel-alloy steels made

1990- Stainless Steels came into use

1904- Vanadium steel used in automobiles and tool manufactory

1935- Magnesium primarily used during WW2

1940- Titanium came into use

1970- Tungsten in pure form used

2000- Silicon used as a semi-conductor in computers
BIBLIOGRAPHY
The World Book Encyclopedia Volume 2; World Book Inc: 1984.
Zronik, J. “Metals (Rocks, Minerals, and Resources)”, Hallmark: 1995
http://www.world-aluminium.org/production/mining/index.html
http://nefertiti.iwebland.com/index.html
http://www.ancientroute.com/#Route
http://www.brass.org/index.htm
http://www.neo-tech.com/index.php
http://www.geology.ucdavis.edu/~cowen/~GEL115/index.html
http://www.mse.uiuc.edu/info/mse182/t41.html
www.encarta.msn.com
By Jackie Galatis