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Line 60: − + − + − + − + − * Chalcopyrites – CuFeS<sub>2</sub> − + + + − Fe<sub>2</sub>O<sub>3</sub>(s)+3C(s)−Δ→2Fe(l)+3CO(g)+ − − Where Fe<sub>2</sub>O<sub>3</sub>(s) stands for Hematite ore (Ferrous Oxide, s = solid), C stands for Carbon (in the form of solid coke), Δ represents the energy requirement for the reaction to take place, Fe stands for Ferrum (elemental Iron, l = liquid) and CO stands for Carbon monoxide (g = gaseous state) − − + + − + Line 95:
Line 94: − + − − − − ''From the ground he gets stones..'' − − ''The fire burns fiercely as the bellows blow.'' − − ''The little hammer clatters, tinning tanang,'' − − ''A shower of sparks flies into her breast'' − − ''He puts it in black'' − − ''He pulls it out red'' − − ''Standing he beats it'' − + − + − + − + − + − + − + − + +
no edit summary
=== Archeological Excavations ===
=== Archeological Excavations ===
[[File:Table of Iron Tools and Implements.png|right|frameless|519x519px]]
[[File:Table of Iron Tools and Implements.png|562x562px|alt=|thumb|Various implements used during the early, middle and late stages of Iron Age in India]]
The following are a few iron artifacts excavated and investigated in Indian archeological sites.<ref name=":1" />
The following are a few iron artifacts excavated and investigated in Indian archeological sites.<ref name=":1" />
* Iron articles such as '''spikes, nails and piece'''s have been unearthed in the monastery at '''Piprahwa''', about 20 km from the ruins at Kapilvastu ('''near Nepal border''').
* Iron articles such as '''spikes, nails and piece'''s have been unearthed in the monastery at '''Piprahwa''', about 20 km from the ruins at Kapilvastu ('''near Nepal border''').
* [[File:Delhi Iron Pillar.png|right|frameless|400x400px|The famous pillar at Mehrauli, near Kutub Minar in Delhi shows that Megalithic Iron-smiths evolved the technique of forging]]The '''famous pillar at Mehrauli, near Kutub Minar''' in Delhi (more than 7 meters in height and about 7 tonnes in weight) was originally erected at Mathura and later on re-erected at Delhi. It shows that Megalithic iron smiths had evolved the technique of forging small blooms into huge iron piece.
* [[File:Delhi Iron Pillar.png|right|frameless|400x400px|The famous pillar at Mehrauli, near Kutub Minar in Delhi shows that Megalithic Iron-smiths evolved the technique of forging]]The '''famous pillar at Mehrauli, near Kutub Minar''' in Delhi (more than 7 meters in height and about 7 tonnes in weight) was originally erected at Mathura and later on re-erected at Delhi. It shows that Megalithic iron smiths had evolved the technique of forging small blooms into huge iron piece.
* The '''Dhar pillar''' is dated to 12th century A.D. It was intact till 1304 A.D. and then broken into three pieces. Its height was more than the double of Delhi pillar.
* The '''Dhar pillar''' is dated to 12th century A.D. It was intact till 1304 A.D. and then broken into three pieces. Its height was more than the double the Delhi pillar.
* The '''pillar''' '''at Mount Abu''' stands at the temple of Achaleswar, which was built in 1412 A.D. It has a trident on its top.
* The '''pillar''' '''at Mount Abu''' stands at the temple of Achaleswar, which was built in 1412 A.D. It has a trident on its top.
* The famous sun temple at '''Konark in Orissa has''' '''wrought iron beams'''. They are dated to 13th century A.D. Several iron beams have been used in the ancient temple of Konark in Orissa which was built in the 9th century.
* The famous sun temple at '''Konark in Orissa has''' '''wrought iron beams'''. They are dated to 13th century A.D. Several iron beams have been used in the ancient temple of Konark in Orissa which was built in the 9th century.
== Pyrometallurgy ==
== Pyrometallurgy ==
The extraction of iron is pyrometallurgy. It is the extractive metallurgy which consists of the thermal treatment given to minerals or ores to recover the metal. The process involves chemical reactions at elevated temperature. The process of extraction of iron is fundamentally very simple as it consists essentially of the reduction of iron oxide by carbon. But as molten iron dissolves carbon and other impurities, iron obtained is impure and is known as pig iron or cast iron. The ore (red haematite or hydrated oxide or carbonate) is calcined in shallow kilns to remove moisture, carbon dioxide etc. The ore thereby becomes porous and is then more easily reduced in the blast furnace.<ref>[https://prog.lmu.edu.ng/colleges_CMS/document/books/MCE329%20-%20Metallurgy%20of%20Iron(329).pdf Metallurgy of Iron] </ref>
The extraction of iron is pyrometallurgy. It is the extractive metallurgy which consists of the thermal treatment given to minerals or ores to recover the metal. The process involves chemical reactions at elevated temperature. The process of extraction of iron is fundamentally very simple as it consists essentially of the reduction of iron oxide by carbon. But as molten iron dissolves carbon and other impurities, iron obtained is impure and is known as pig iron or cast iron. The ore (red haematite or hydrated oxide or carbonate) is calcined in shallow kilns to remove moisture, carbon dioxide etc. The ore thereby becomes porous and is then more easily reduced in the blast furnace.<ref name=":3">[https://prog.lmu.edu.ng/colleges_CMS/document/books/MCE329%20-%20Metallurgy%20of%20Iron(329).pdf Metallurgy of Iron] </ref>
==== Iron Ores ====
==== Iron Ores ====
* Red Hematite - Fe<sub>2</sub>O<sub>3</sub> (Oxide ore), and Brown Hematite - 2 Fe<sub>2</sub>O<sub>3</sub> . H<sub>2</sub>O are widely used.
* '''Oxides''': Red Hematite - Fe<sub>2</sub>O<sub>3</sub> (Oxide ore), and Brown Hematite (Limonite) - 2 Fe<sub>2</sub>O<sub>3</sub> . H<sub>2</sub>O and Magnetite (Fe<sub>3</sub>O<sub>4</sub>)
* Spathic Iron ore or Siderite - FeCO<sub>3</sub> (Carbonate ore) is rarely used.
* '''Carbonates''': Spathic Iron ore or Siderite - FeCO<sub>3</sub> (Carbonate ore) is rarely used.
* Iron pyrites – FeS<sub>2</sub>
* '''Sulphides''': Iron pyrites – FeS<sub>2</sub> and Chalcopyrites – CuFeS<sub>2</sub>
Iron is normally extracted from its oxide ore called haematite and is rarely extracted from carbonate ore called siderite. Iron pyrite is an important source of sulphur and therefore it is not used in the extraction of iron.
Iron is normally extracted from its oxide ore called haematite and magnetite and is rarely extracted from carbonate ore called siderite. Iron pyrite is an important source of sulphur and therefore it is not used in the extraction of iron.<ref name=":3" />
==== Chemical Reaction ====
==== Chemical Reaction ====
The overall reaction for the production of iron in a blast furnace is as follows:
The overall reaction for the production of iron in a blast furnace is as follows:
'''Fe<sub>2</sub>O<sub>3</sub>(s)+3C(s)−Δ→2Fe(l)+3CO(g)'''
Where Fe<sub>2</sub>O<sub>3</sub>(s) stands for Hematite ore (Ferrous Oxide, s = solid), C stands for Carbon (in the form of solid coke), Δ represents the energy requirement for the reaction to take place, Fe stands for Ferrum (elemental Iron, l = liquid) and CO stands for Carbon monoxide (g = gaseous state)[[File:Blast furnace .png|381x381px|Blast Furnace for Converting Iron Oxides to Iron Metal. Courtesy: General Chemistry (Libre Texts)|alt=|thumb]]
Iron compounds in the ores could be reduced by carbon; and for a long time, charcoal was the form of carbon used in the reduction process. Charcoal was replaced by Coke, a form of carbon formed by heating coal in the absence of air to remove impurities, improving the reduction process. As seen in the equation above, the actual reductant is CO, which reduces Fe<sub>2</sub>O<sub>3</sub> to give Fe(l) and CO<sub>2</sub>(g).
Iron compounds in the ores could be reduced by carbon; and for a long time, charcoal was the form of carbon used in the reduction process. Charcoal was replaced by Coke, a form of carbon formed by heating coal in the absence of air to remove impurities, improving the reduction process. As seen in the equation above, the actual reductant is CO, which reduces Fe<sub>2</sub>O<sub>3</sub> to give Fe(l) and CO<sub>2</sub>(g).[[File:Blast furnace .png|right|frameless|325x325px|Blast Furnace for Converting Iron Oxides to Iron Metal. Courtesy: General Chemistry (Libre Texts)]]
==== Steps in the Extraction of Iron ====
==== Steps in the Extraction of Iron ====
The extraction of iron involves following steps.
The extraction of iron involves following steps.
# Collection of raw materials
# Washing and concentration or dressing of the ore
# Washing and concentration or dressing of the ore
# Preliminary roasting and calcinations
# Preliminary roasting and calcinations
# Reduction or smelting in a Blast Furnace
# Reduction or smelting in a Blast Furnace
Collection of raw materials: Iron is the most abundant metal in the earth's crust. Because of its strong affinity to oxygen, it is not found in the elemental state but predominantly in its combined forms such as oxides, and much less as sulphide and carbonate.
== Extraction Process in Ancient Times ==
== Extraction Process in Ancient Times ==
Iron ores were widely distributed in Indian subcontinent. However they were delayed to smelt Iron. The reason is that the primitive condition of furnace has produced temperature about 1100°C which is required for Copper smelting. But Iron needs a high temperature almost above 1500°C for the ore to smelt into a liquid. Little solid grains of Iron have obtained by low temperature as 800°C. Iron was a soft and spongy material which had to be admixed with carbon in proper proportion to obtain sufficient sharpness and hardness. It was obtained from ores at high temperature. Iron has more impurties than Copper. This impurity has to be removed by using a catalytic flux such as lime to produce the slag (Rao 1970:258). Iron produced by smelting is divided into 3 kinds:
Iron ores were widely distributed in Indian subcontinent. However they were delayed to smelt Iron. The reason is that the primitive condition of furnace has produced temperature about 1100°C which is required for Copper smelting. But Iron needs a high temperature almost above 1500°C for the ore to smelt into a liquid. Little solid grains of Iron have obtained by low temperature as 800°C. Iron is a soft and spongy material which had to be admixed with carbon in proper proportion to obtain sufficient sharpness and hardness. It was obtained from ores at high temperature. Iron has more impurities than Copper. This impurity is removed by using a catalytic flux such as lime to produce the slag (Rao 1970:258). Iron produced by smelting is of 3 kinds:
* wrought iron (Kanta Loha)
* wrought iron (Kanta Loha)
Quenching and tempering was also learned along with steeling of Iron. Quenching consists immersing the red hot metal into water. Metal would become harden by this process. Tempering consists of repeated heating of the metal and allowing it to cool slowly while it is hammered (Banerjee 1965:2).<ref>Saravanan, R. ''Iron:'' ''From Metal to Metallurgy'' Heritage: Journal of Multidisciplinary Studies in Archaeology 5 (2017): 514‐518</ref> Raw iron, wood and carbon are heated in earthen bowls at a temperature of 1535°C and then, slowly cooled over 24 hours. This gives high quality carbon rich steel. A sword made of this steel is so sharp and strong that it even cuts silk smoothly.
Quenching and tempering was also learned along with steeling of Iron. Quenching consists immersing the red hot metal into water. Metal would become harden by this process. Tempering consists of repeated heating of the metal and allowing it to cool slowly while it is hammered (Banerjee 1965:2).<ref>Saravanan, R. ''Iron:'' ''From Metal to Metallurgy'' Heritage: Journal of Multidisciplinary Studies in Archaeology 5 (2017): 514‐518</ref> Raw iron, wood and carbon are heated in earthen bowls at a temperature of 1535°C and then, slowly cooled over 24 hours. This gives high quality carbon rich steel. A sword made of this steel is so sharp and strong that it even cuts silk smoothly.
The ancient process of iron making has been vividly described in the folk songs of `Chokh Agaria' from Lapha. One of these songs as translated by Joshi is as follows:<ref name=":2" /><blockquote>''She presses down the bellows with the strength of her heels.''
The ancient process of iron making has been vividly described in the folk songs of `Chokh Agaria' from Lapha. One of these songs as translated by Joshi is as follows:<ref name=":2" /><blockquote>''She presses down the bellows with the strength of her heels,'' ''He wields the heavy hammer with all his might''
''He wields the heavy hammer with all his might''
''The chokh girl blows the bellows at the forge''
''From the ground he gets stones..The fire burns fiercely as the bellows blow.''
''Like a drum it sounds Datur Thunda'''
''The little hammer clatters, tinning tanang,'' ''A shower of sparks flies into her breast''
''How happy I feel''
''He puts it in black'' ''He pulls it out red,'' ''Standing he beats it''
''The chokh boy beats with the hammer''
''The chokh girl blows the bellows at the forge,'' ''Like a drum it sounds Datur Thunda'''
''The hammer whistle.s as he swings it round''
''How happy I feel,'' ''The chokh boy beats with the hammer''
''And I feel very happy.''</blockquote>As it appears from the above mentioned song the whole operation was a family affair controlled by the headman and his wife and the technology was maintained as a secret, passed on from generation to generation. The younger generation participated in the activities and when by the age of 17 to 20 they were trained in all the skills of the trade, they were permitted to marry and operate their own furnace. The actual practice of iron making can be divided into the following six steps-
''The hammer whistles as he swings it round,'' ''And I feel very happy.''</blockquote>As it appears from the above mentioned song the whole operation was a family affair controlled by the headman and his wife and the technology was maintained as a secret, passed on from generation to generation. The younger generation participated in the activities and when by the age of 17 to 20 they were trained in all the skills of the trade, they were permitted to marry and operate their own furnace. The actual practice of iron making can be divided into the following six steps-
# collection of raw material i.e. iron ore, wood and refractory clay
# '''collection of raw material''' '''i.e. iron ore, wood and refractory clay''': In spite of the abundantly available hematite deposits, ancient smelters preferred to use low grade magnetite ore. The ore was concentrated by panning in the water stream. Ore is calcined to remove moisture and associated organic matter and broken to small pieces. The charcoal used for heating the ore and generating the reducing gas (CO) was produced from a variety of wood depending upon their availability in the region, and generally no basic flux was used to adjust the properties of the FeO rich fayalite (2FeO.SiO<sub>2</sub>) slag formed during smelting. The refractory clay and stiff mud are used for making the furnace.
# construction of the furnace and the tuyere pipe.
# construction of the furnace and the tuyere pipe.
# making and fixing the bellows.
# making and fixing the bellows.
# drying, firing and operating the furnace.
# drying, firing and operating the furnace.
# removal of slag and handling of red hot sponge iron bloom.
# removal of slag and handling of red hot sponge iron bloom.
# secondary refining of the bloom.
# secondary refining of the bloom.
#
== References ==
== References ==
[[Category:Shastras]]
[[Category:Shastras]]