Activity Two
Activity Name
Learning Aims
2. Smelting and the Welsh connection
Understand how iron ore was smelted in the 19th century.
Understand how the WSMR was linked to Welsh industry.
Understand why iron ore from the Brendon Hills was special
Links to National
Curriculum
History
Knowledge and understanding of events, people and changes in
the past
Geographical and enquiry skills
Knowledge and understanding of patterns and processest
Science
Materials and their properties
Resources
2a The smelting process; 2b The smelting process worksheet; 2c Iron
recipe card; 2d Film of Ebbw Vale; 2e Transport of iron ore.
Activities
1. Smelting process
Use the illustration of the smelting process as a visual aid for
explaining the smelting process (resource 2a).
Test understanding of the smelting process by putting the
captions in the correct order (resource 2b).
2. Iron recipe card
You are an inventive chef charged with producing an iron recipe card
(resource 2c).
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1
Teacher information
Introduction
The purpose of the West Somerset
Mineral Railway was to transport the
iron ore mined in the Brendon Hills
down to Watchet. Once in Watchet it was
shipped over to Newport, and from
there taken by rail to the smelting
furnaces at Ebbw Vale. Refer to resource
2e for a map of this.
The Ebbw Vale Company
The Ebbw Vale Company was
founded in Wales in 1790.
By 1823 there were six blast furnaces
on the two sites, and together they
produced 20,425 tons of cast iron.
The ‘bar iron’ produced at Ebbw Vale
was usually sold to merchants in
London or Liverpool, but as railway
construction accelerated, Ebbw Vale
supplied rails direct to the railway
companies, such as the Newcastle
and Carlisle Railway.
The demand for steel rails was high in
1870, and although it troughed by
1872 competition with other
countries such as Spain to supply ore
was diminished due to the Spanish
Civil War. The peace was restored in
1876, which meant their more
cheaply worked iron ore was
competing with that from the
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Brendon Hills. In an attempt to cut
costs wages of the miners were cut by
20%. By 1879 the Ebbw Vale
Company’s trade was suffering, and
reported a loss. There was therefore
little need for Brendon Hill ore.
The South Wales iron industry
The iron industry had evolved steadily
up to the Industrial Revolution. By 1830
south Wales made 40% of all iron in
Britain. By 1851 there were more Welsh
people employed in industry than those
in agriculture, giving Wales a claim to be
the first agricultural nation.
Smelting
Smelting is the method of producing
metal from an ore. This includes
extracting iron from iron ore to produce
steel. Other metals such as copper can
also be extracted from their ores.
Smelting uses:
a)
heat (the melting temperature of
iron is 1535° C!) and
b)
a chemical reducing agent.
The reducing agent is commonly a fuel
that is a source of carbon such as coke,
(or in earlier times charcoal), to change
the oxidation state of the metal ore. The
carbon or carbon monoxide derived
from it removes oxygen from the ore to
leave the metal.
Most ores are impure, and limestone is
used to remove the slag (waste product)
from the ore.
Smelting iron ore requires three key
ingredients:
iron ore (mineral)
limestone (flux to remove impurities)
coke (fuel)
1.
The materials were measured
and tipped into the furnace.
2.
They grew very hot as they
settled in the furnace, and at
1,500 ºC they turned into a
molten mass of iron and slag.
3.
The slag was removed
periodically, and the iron was
guided into channels in the sand
floor of a cast house.
4.
It was known as pig iron because
these channels resembled sows
suckling their young. Once the
iron solidified the ‘pigs’ were dug
out.
This process was repeated with new
ingredients a few hours later. It is likely
that in the 1860s as many as 80 ‘pigs’
were made each time.
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The history of smelting
Metallic iron has usually been
manufactured in one of three forms:
1.
wrought iron (containing less
than 0.5% carbon)
2.
steel (containing between 0.5%
to 1.5% carbon)
3.
cast iron (containing more than
2% carbon).
Producing wrought iron before the
Industrial Revolution
Until early in the 18th century most
iron was smelted in Europe by the
‘direct’ process. This involved placing
small pieces of iron ore and fuel
(usually charcoal or occasionally
peat), in a small bowl or clay shaft
furnace. The fuel was fired and
blasted with air from a hand or foot
operated bellows.
The melting temperature of iron is
1535° C, but in early furnaces only
temperatures of between 900°-1100°
C could be achieved. A chemical
reaction meant that the oxygen in the
heated ore combined with the carbon
in the fuel to form carbon dioxide,
reducing the ore to metallic iron,
whilst other impurities combined to
form slag. The iron and slag formed a
soft lump known as a ‘bloom’.
Temporary bloomeries had been used
to make small quantities of iron since
the Iron Age.
By breaking open the furnace the
bloom could be removed and
hammered while hot to expel much
of the slag, leaving a lump of impure
wrought iron.
Cast iron and ‘puddling’
By the 17th century it became possible
to produce molten iron which could
be cast in moulds.
Puddling was invented in 1784 to
remove carbon from iron by forming
a large ball of iron, which was then
hammered.
The metal was then suitable for
beams, bars, or later for railway rails.
Steel and the Bessemer process
Steel has been known as a hard
wearing material for tools and
weapons since the Iron age, but up
until the 19th century it could only be
produced on a small scale.
Henry Bessemer invented a process in
1856 which enabled it to be made by
blowing air though a converter which
removed the carbon from the pig
iron. The process lasted for only
twenty minutes regardless of the size
of the converter.
After two years of producing brittle
steel Bessemer realized that in his
original experiments he had used iron
ore free from phosphorous. By using
spiegeleisen the iron produced was
no longer brittle, and therefore
suitable for producing the steel rails
much in demand in the 1860s.
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The ore found in the Brendon Hills was
low in sulphur and phosphorus, and
rich in manganese, which meant it was
valuable for making Bessemer steel.
Iron production today
A man called Sidney Gilchrist-Thomas
found in 1879 that be changing the
lining of he Bessemer converter from
an acidic to a basic lining, any iron ore
could be smelted.
Today 90% of mining of metallic ores
is for the extraction of iron.
The method of producing iron has
not changed much since the 19th
century.
Answers to resource 2c
1. Choose 3 ingredients needed to
produce iron and label them in the
ovals:
copper ore
limestone
coal
iron ore sandstone wood coke
3. Choose a waste product and label it
in the triangle:
iron ore water gas slag limestone
For more information about the
products of iron smelting please refer to
the All about iron activity in the
Bearland Ventilation Flue Teachers’Pack.
For more information about the
impacts of WSMR mining and modern
mining please refer to the
Environmental impacts activity in the
Introduction to the WSMR Teachers’
Pack.