8,311
edits
Changes
Jump to navigation
Jump to search
no edit summary
Line 1:
Line 1:
−
+
+
+
+
+
+
+
+
+
+
+== Types of Ferrous Materials ==+
Iron, called as Ayas (Samskrit: अयस्) heralded a new era in the history of mankind. Iron technology has a special place among the ancient technologies that accelerated the pace of progress and brought prosperity in society. In human history Iron Age succeeded Copper-Bronze Age as iron required a different kind of skill and a higher level of metallurgical expertise. The craftsmen who were adept in working with copper and its alloys and other glittering metals like gold, silver etc., that could be used in their native form at a much lower temperature could not smelt iron with the same technique. India has rich iron ore deposit. The ore is not only widely distributed but also easily accessible in the form of nodules scattered on the earth's surface. This must have facilitated easy hand picking of rich ore nodules by the early or primitive metal workers. However, wide distribution and easy access to the ore were insufficient to produce metallic iron and required skilled metal workers possessing sufficient metallurgical know-how. Archeological researches and archival accounts including foreign records by travelers or historians of ancient India bear that Indian iron and steel had gained significant recognition in the ancient world.<ref name=":0">Vibha Tripathi, ''Aspects of Iron Technology in India'' in Propagation, vol 3-1, 2012</ref> India abounded with vast deposits of many minerals and precious stones, thus [[Mineralogy (धातुशास्त्रम्)|mineralogy]] was an important topic dealt with even in texts such as Rigveda that helped develop and sustain many metal and alloy industries.
+[[File:Properties of Iron Element.png|thumb|334x334px|Courtesy: Encyclopaedia Britannica Inc,]]
+Iron, called as Ayas (Samskrit: अयस्) heralded a new era in the history of mankind. Iron (Fe), chemical element, metal of Group 8 (VIIIb) of the periodic table, is the most-used and cheapest metal found in the earth's crust.<ref name=":9">Britannica, T. Editors of Encyclopaedia. "iron." Encyclopedia Britannica, September 20, 2024. <nowiki>https://www.britannica.com/science/iron-chemical-element</nowiki>.</ref>
+Iron technology has a special place among the ancient technologies that accelerated the pace of progress and brought prosperity in society. In human history Iron Age succeeded Copper-Bronze Age as iron required a different kind of skill and a higher level of metallurgical expertise. The craftsmen who were adept in working with copper and its alloys and other glittering metals like gold, silver etc., that could be used in their native form at a much lower temperature could not smelt iron with the same technique. India has rich iron ore deposit. The ore is not only widely distributed but also easily accessible in the form of nodules scattered on the earth's surface. This must have facilitated easy hand picking of rich ore nodules by the early or primitive metal workers. However, wide distribution and easy access to the ore were insufficient to produce metallic iron and required skilled metal workers possessing sufficient metallurgical know-how. Archeological researches and archival accounts including foreign records by travelers or historians of ancient India bear that Indian iron and steel had gained significant recognition in the ancient world.<ref name=":0">Vibha Tripathi, ''Aspects of Iron Technology in India'' in Propagation, vol 3-1, 2012</ref> India abounded with vast deposits of many minerals and precious stones, thus [[Mineralogy (धातुशास्त्रम्)|mineralogy]] was an important topic dealt with even in texts such as Rigveda that helped develop and sustain many metal and alloy industries.
== Introduction ==
== Introduction ==
Line 13:
Line 16:
Rigveda begins with a prayer to Agni to bless mankind with all worldly pleasures. One of the major contributions of the discovery of fire and pyrotechnology was its use for the extraction of metals from their minerals. Prakash<ref>Prakash, S. (1965) ''Founders of Science in Ancient India'', New Delhi: The Research Institute of Ancient Studies.</ref> postulated and described the havankund (yajnakunda) as the open air laboratory of the Vedic times which may have been responsible for the discovery and development of the many new uses of the thermochemical energy.<ref name=":0" />
Rigveda begins with a prayer to Agni to bless mankind with all worldly pleasures. One of the major contributions of the discovery of fire and pyrotechnology was its use for the extraction of metals from their minerals. Prakash<ref>Prakash, S. (1965) ''Founders of Science in Ancient India'', New Delhi: The Research Institute of Ancient Studies.</ref> postulated and described the havankund (yajnakunda) as the open air laboratory of the Vedic times which may have been responsible for the discovery and development of the many new uses of the thermochemical energy.<ref name=":0" />
−= Historical evidence of Iron in Ancient India =
+== Historical evidence of Iron in Ancient India ==
Rapid developments in iron making and its use took place around 1400 B.C. The history of early iron smelting, practiced by the tribal artisans in different regions of ancient India dates back to 1300 to 1200 B.C. The use of iron was relatively unknown except in areas where iron bearing minerals were abundant. Prakash and Tripathi<ref>Prakash, B., and Tripathi, V., (1986), ''Iron technology in ancient india,'' In Historical Metallurgy, September, pp. 568-579.</ref> have documented the early iron age cultures, which could have been independent of each other, arising in five different zones of India. These five cultures were
Rapid developments in iron making and its use took place around 1400 B.C. The history of early iron smelting, practiced by the tribal artisans in different regions of ancient India dates back to 1300 to 1200 B.C. The use of iron was relatively unknown except in areas where iron bearing minerals were abundant. Prakash and Tripathi<ref>Prakash, B., and Tripathi, V., (1986), ''Iron technology in ancient india,'' In Historical Metallurgy, September, pp. 568-579.</ref> have documented the early iron age cultures, which could have been independent of each other, arising in five different zones of India. These five cultures were
Line 58:
Line 61:
== 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 name=":3">[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>
+{| class="wikitable"
+|+Elemental Properties of Iron<ref name=":9" />
+|'''Atomic number'''
+|26
+|-
+|'''Atomic mass'''
+|55.85 g.mol -1
+|-
+|'''Electronegativity according to Pauling'''
+|1.8
+|-
+|'''Density'''
+|7.8 g.cm-3 at 20°C
+|-
+|'''Melting point'''
+|1536 °C
+|-
+|'''Boiling point'''
+|2861 °C
+|-
+|'''Specific gravity'''
+|7.86 (20 °C)
+|-
+|'''Isotopes'''
+|8
+|-
+|'''Electronic Configuration'''
+|[ Ar ] 3d6 4s2
+|-
+|'''Discovered by'''
+|The ancients
+|}
==== Iron Ores ====
==== Iron Ores ====
Line 94:
Line 129:
==== Products of the Blast furnace ====
==== Products of the Blast furnace ====
−The products obtained from the blast furnace include Pig Iron, Slag and Flue gasses.<ref name=":3" /> Pig iron is the most impure form of iron having impurities. Slag is mostly calcium silicate and some amount of aluminum silicate. Gasses produced in the extraction process are called flue gasses containing CO (carbon monoxide), Nitrogen and hyderogen.
+The products obtained from the blast furnace include Pig Iron, Slag and Flue gasses.<ref name=":3" /> Pig iron is the most impure form of iron having impurities. Slag is mostly calcium silicate and some amount of aluminum silicate. Gasses produced in the extraction process are called flue gasses containing CO (carbon monoxide), Nitrogen and hydrogen.
==== Commercial forms of Iron ====
==== Commercial forms of Iron ====
Line 101:
Line 136:
# '''Cast Iron''' - Pig iron when is remelted in a vertical furnace can be poured into moulds. It is then called cast iron. When the pig iron is suddenly cooled, crystalline cast iron is obtained called as white cast iron. In this form carbon is present combined with iron as iron carbide. However, if the molten pig iron is cooled gradually in sand moulds, a graphite coloured iron is formed called grey cast iron. Major part of cast iron is used to manufacture steel and other heavy machinery.
# '''Cast Iron''' - Pig iron when is remelted in a vertical furnace can be poured into moulds. It is then called cast iron. When the pig iron is suddenly cooled, crystalline cast iron is obtained called as white cast iron. In this form carbon is present combined with iron as iron carbide. However, if the molten pig iron is cooled gradually in sand moulds, a graphite coloured iron is formed called grey cast iron. Major part of cast iron is used to manufacture steel and other heavy machinery.
# '''Wrought or Malleable iron''' – It is the purest form of iron. It contains about 0.2 % carbon.
# '''Wrought or Malleable iron''' – It is the purest form of iron. It contains about 0.2 % carbon.
−# '''Steel''' – It is an alloy of iron with carbon and other elements like manganese, silicon and phosphorus. It is midway between cast and wrought iron as far as impurities are concerned. It contains 0.1 to 1.5 % carbon.
+# '''Steel''' – It is an alloy of iron with carbon and other elements like manganese, silicon and phosphorus. It is midway between cast and wrought iron as far as impurities are concerned. It contains 0.1 to 1.5 % carbon.<ref name=":3" />
+== Ferrous Materials - Types and Characteristics ==
+The Rasaratnasamucchaya<ref name=":6" /> and Rasa-jala-nidhi<ref name=":8" /> describe three types of ferrous materials with their characteristics.<blockquote>मुण्डं तीक्ष्णं तथा कान्तं । मुण्डात् तीक्ष्णं ततः कान्तं प्रशस्तं ज्ञायते बुधैः ॥</blockquote>Iron is of three different kinds, namely Munda, Tikshna and Kanta. The second is better than the first and the third is better than the second.
+मुण्डम् (पूतिलौहम्) ।<blockquote>मृदु कुण्ठं कड़ारञ्च त्रिविधं मुण्डमुच्यते । द्रुतद्रावमविस्फोटं चिक्कणं मृदु तच्छुभम् ॥
+हतं यत् प्रसरेद् दुःखात् तत् कुण्ठं मध्यमं स्मृतम् । यद्धतं भज्यते कृष्णां हीनं स्यात्तत् कड़ारकम् ॥</blockquote>(a) Munda or ordinary iron.
+Munda or ordinary iron is of three different kinds, viz. mridu (soft), kuntha/kadara (obdurate), and karara (brittle). Mridu or soft is that which melts quickly and has a smooth and glossy surface. Kuntha or obdurate is that which can be expanded with much difficulty by hammering. Karara or brittle iron is that which breaks easily. Of these, the first is comparatively commendable, the second is of moderate efficacy and the third is the least efficacious for medicinal purposes.<ref name=":8" />
+तीक्ष्णम् ।<blockquote>खरं सारञ्च हृन्नालं तारापट्टञ्च वज्रकम् । काललौहाभिधानञ्च षड्विधं तीक्ष्णमुच्यते ॥</blockquote>(b) Tikshna iron.
+There are six different kinds of tikshna iron, viz. (1) khara (2) sara, (3) hrinnala (4) tarapatta (5) vajraka and (6) kala. Each of them is further described.
+# Khara iron - is that which is coarse, inflexible, and devoid of carved lines on its surface. This iron when broken into pieces, presents sectional surfaces as glazy as mercury.
+# Sara iron - this kind of tikshna iron which breaks into pieces, when hammered, has pogara or carved lines on its surface. It is obtained from ores of yellowish colour.
+# Hrinnala - this is yellowish black in color. It has on its surfaces, pogara or carved lines in the shape of bird's beaks. It presents very coarse sectional surfaces at the places where it is cut into pieces.
+# Tarapatta iron - is obtained from iron ores by a class of smiths who are specialists in the science of ores. This iron is black, smooth, glazy, and has fine pogara on its surface. This is prepared in the shape of a spoon (minus the handle). It is a kind of iron which never rusts, even if it is exposed to the sun, rains, and wind. This is most probably the iron out of which the Iron Pillar of Delhi, the iron beams in the ruins of Konark temple, the cannons of Vishnupur etc., were prepared. The art of preparing this iron is now totally lost.
+# Vajra iron - is that which has on its surface plenty of fine and deep seated lines; straight and carved pogara. It is of the appearance of an electric flash and is of a glossy black color.
+# Kala iron - is heavy and of a deep blue black color. Its surface is glossy, heavy and bright. It can not be broken into pieces by being hammered upon by means of another piece of iron.<ref name=":8" />
+कान्तलौहम् । तस्य लक्षणम् ।<blockquote>पात्रे यस्मिन् प्रसरति जले तैलबिन्दुर्नलिप्तं गन्धं हिंगु त्यजति च तथा तिक्ततां निम्बकल्कः ।
+पाके दुग्धं व्रजति शिखराकारतां नैति भूमिं कृष्णाङ्ग स्यात् सजलचणकः कान्तलौहं तदुक्तम् ॥</blockquote>Kanta iron (an oxide of iron) having the magnetic power of attracting iron. It is of such nature that a drop of oil thrown into water contained in a pot of this iron does not spread over the surface of the water; neither does the oil stick to the inner surface of the pot. Hingu (asafoetida) kept in a pot of this iron loses its smell in course of time. Bark of nimba tree (neem) pestled with water, loses its bitterness if kept for sometime in a pot of this iron. Milk boiled in a pot of this iron will not overflow the borders of this pot.
+Kanta iron is softer than silver, coarse and black in color. It is directly obtained from the mines. Water boiled in a pot made of this iron smells of hingu. Kanta iron of superior quality is generally found to be in the form of ores covered with silver. Such iron can cure all sorts of diseases, including leprosy. It is of five kinds.
+# Bhramaka iron is that which makes a piece of ordinary iron revolve around it.
+# Chumbaka kanta iron (loadstone) is that which can cling to pieces of ordinary iron.
+# Karshaka kanta iron is that which can attract to it pieces of ordinary iron.
+# Dravaka kanta iron is that at touch of which ordinary iron melts (without any heat being applied).
+# Romakanta is that which causes the growth of fresh hair at that part of the skin which is lightly pierced through by it.
−Of these, Bhramaka is the least efficacious while Dravaka is the most efficacious of all. The kanta iron which has only one or magnetic point is the Ekamukh, and is least efficacious, while that having two (dvimukh) or three (trimukh) points is of moderate efficacy, while that with several points (sarvatomukha) is the most efficacious.
−The Rasaratnasamucchaya describes three types of ferrous materials.
{| class="wikitable"
{| class="wikitable"
−|+Classification of iron and its properties as given in Rasa Ratna Samucchaya<ref name=":6">Prakash, B. ''Ancient Iron Making in India'' in Iron & Steel Heritage of India Ed. S. Ranganathan, ATM 97, Jamshedpur</ref>
+|+Indian Classification of iron and its properties <ref name=":6">Prakash, B. ''Ancient Iron Making in India'' in Iron & Steel Heritage of India Ed. S. Ranganathan, ATM 97, Jamshedpur</ref><ref name=":8">Mookerjee, Bhudeb. (1984 Second Edition) ''Rasa-Jala-Nidhi or Ocean of Indian Chemistry, Medicine and Alchemy'', ''Vol. 3'' Varanasi: Srigokul Mudranalaya</ref>
!Kinds of Iron
!Kinds of Iron
(Loha)
(Loha)
Line 112:
Line 177:
!Properties
!Properties
|-
|-
−| rowspan="5" |Kanta Loha (Soft Iron)
+| rowspan="5" |कान्तम् ॥ Kanta Loha (Soft Iron)
−|Bhramaka
+|भ्रामक (Bhramaka)
|Very soft magnetic iron
|Very soft magnetic iron
|-
|-
−|Chumbaka
+|चुम्बक (Chumbaka)
|Mildly magnetic, sticks to iron pieces
|Mildly magnetic, sticks to iron pieces
|-
|-
−|Karsaka
+|कर्षक (Karsaka)
|It can attract iron objects
|It can attract iron objects
|-
|-
−|Dravaka
+|द्रावक (Dravaka)
|Very strong magnetic iron
|Very strong magnetic iron
|-
|-
−|Romaka
+|रोमकान्तम् (Romakanta)
−|Permanent magnet, develops strong magnetic field around it. Itmay be Ekmukh or sarva mukh
+|A permanent magnet develops a strong magnetic field around it. It may be Ekmukh, dvi or trimukh. Sarvatomukham is the best.
|-
|-
−| rowspan="6" |Tikshna Loha (Carbon steel)
+| rowspan="6" |तीक्ष्ण ॥ Tikshna Loha (Carbon steel)
−|Khara
+|खरं (Khara)
|Develops good cutting edge, breaks on bending
|Develops good cutting edge, breaks on bending
|-
|-
−|Sara
+|सार (Sara)
|Softer iron and it has fibrous fracture
|Softer iron and it has fibrous fracture
|-
|-
−|Hrnnala
+|हृन्नाल (Hrnnala)
|Hard and tough having fibrous fracture
|Hard and tough having fibrous fracture
|-
|-
−|Travaratta
+|तारापट्ट (Tarapatta)
|Develops good cutting edge
|Develops good cutting edge
|-
|-
−|Vajra
+|वज्रकम् (Vajra)
|Has good hardening and tempering property, has bluish color and hard cutting edge
|Has good hardening and tempering property, has bluish color and hard cutting edge
|-
|-
−|Kala
+|काल (Kala)
|Develops hard cutting edge after blue tempering
|Develops hard cutting edge after blue tempering
|-
|-
−| rowspan="3" |Munda Loha (Cast Iron)
+| rowspan="3" |मुण्ड ॥ Munda Loha (Cast Iron)
−|Mrdu
+|मृदु (Mrdu)
|Soft brittle iron may be grey cast iron, has low melting point
|Soft brittle iron may be grey cast iron, has low melting point
|-
|-
−|Kunda
+|Kunda/कुण्ठ (Kuntha)
|Mottled grey iron
|Mottled grey iron
|-
|-
−|Kadara
+|कड़ार (Kandara)/Karara
|White cast iron
|White cast iron
|}
|}
−== 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 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. Iron produced by smelting is of 3 kinds based on its carbon content:
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. Iron produced by smelting is of 3 kinds based on its carbon content:
Line 190:
Line 254:
# '''Drying, firing and operating the furnace''': After the dried furnace and the raw material were ready the furnace was charged with dried wood chips and then filled with charcoal up to the top. A ritual pooja and havan were performed praying for the successful operation of the furnace and then it was ignited using a little of the sacred fire from the havan. This was introduced inside the furnace through the tuyere pipe. When the wood starts burning, the bellows were operated slowly to build the fire inside the furnace. After the yellow flame appeared at the mouth of the furnace the blowing rate was increased to raise the furnace temperature. As the charcoal got consumed, ore was charged and the blowing was continued till a translucent blue flame appeared at the top. Blue flame indicated that the furnace reached a temperature of > 1000<sup>o</sup>C and the charcoal is burning to generate CO gas. At this stage the furnace was charged with alternate layer of ore and charcoal in the ratio 1:2 and the air blowing rate was adjusted and controlled to maintain steady condition. The temperature inside the furnace was visually examined by peeping through the tuyere pipe and after about one hour the first slag was tapped. The fluidity .of the slag, its quantity as well as colour on solidification were indicators of successful operation of the furnace. The slag was either tapped periodically or continuously throughout the furnace operation. When sufficient charges of ore had been made, it was followed by few blank charges of charcoal only, and the air blowing rate was increased to consolidate the reduced iron into a large porous lump and separate it from the FeO rich fayalite (2FeO.SiO<sub>2</sub>) slag. The measured temperature at this stage was found to be 1500°C in front of the tuyere. One round took about 5 to 6 hours and preparation is made to take out the hot iron sponge.
# '''Drying, firing and operating the furnace''': After the dried furnace and the raw material were ready the furnace was charged with dried wood chips and then filled with charcoal up to the top. A ritual pooja and havan were performed praying for the successful operation of the furnace and then it was ignited using a little of the sacred fire from the havan. This was introduced inside the furnace through the tuyere pipe. When the wood starts burning, the bellows were operated slowly to build the fire inside the furnace. After the yellow flame appeared at the mouth of the furnace the blowing rate was increased to raise the furnace temperature. As the charcoal got consumed, ore was charged and the blowing was continued till a translucent blue flame appeared at the top. Blue flame indicated that the furnace reached a temperature of > 1000<sup>o</sup>C and the charcoal is burning to generate CO gas. At this stage the furnace was charged with alternate layer of ore and charcoal in the ratio 1:2 and the air blowing rate was adjusted and controlled to maintain steady condition. The temperature inside the furnace was visually examined by peeping through the tuyere pipe and after about one hour the first slag was tapped. The fluidity .of the slag, its quantity as well as colour on solidification were indicators of successful operation of the furnace. The slag was either tapped periodically or continuously throughout the furnace operation. When sufficient charges of ore had been made, it was followed by few blank charges of charcoal only, and the air blowing rate was increased to consolidate the reduced iron into a large porous lump and separate it from the FeO rich fayalite (2FeO.SiO<sub>2</sub>) slag. The measured temperature at this stage was found to be 1500°C in front of the tuyere. One round took about 5 to 6 hours and preparation is made to take out the hot iron sponge.
# '''Removal of slag and handling of red hot sponge iron bloom''': In case of bowl furnaces, generally the slag was allowed to get collected and solidified at the bottom of the furnace. In the case of other furnaces, it was tapped out through the slag hole known as 'Hagan.' After the smelting period was over, the bellows along with blow pipes were removed and the temporary wall for closing the front opening was removed and the partially melted tuyere was taken out with the help of a tong and a wooden pole. It was placed on a large granite stone anvil and hammered to consolidate and remove the molten slag filled in the pores.
# '''Removal of slag and handling of red hot sponge iron bloom''': In case of bowl furnaces, generally the slag was allowed to get collected and solidified at the bottom of the furnace. In the case of other furnaces, it was tapped out through the slag hole known as 'Hagan.' After the smelting period was over, the bellows along with blow pipes were removed and the temporary wall for closing the front opening was removed and the partially melted tuyere was taken out with the help of a tong and a wooden pole. It was placed on a large granite stone anvil and hammered to consolidate and remove the molten slag filled in the pores.
−# '''Secondary refining of the bloom''': This most important and exclusive Indian practice was carried out to remove the slag trapped inside the iron block. For this, the iron bloom was reheated in a smithy forge to almost white hot (>1250°C) condition and silica sand was sprinkled upon it. This reacted with the remaining FeO and helped in forming fluid 2FeO.SiO<sub>2</sub> slag which flowed out of the iron block. The iron block was taken out of the furnace and forged to increase its density. This process was repeated till the bloom was converted into 12 to 15mm square/circular rod. This refined rod containing 0.2 to 0.4% SiO<sub>2</sub> almost free from the slag inclusion was cut into 150 to 180mm long pieces and sold to the blacksmiths or 'Lohars' for reshaping them into useful objects.
+# '''Secondary refining of the bloom''': This most important and exclusive Indian practice was carried out to remove the slag trapped inside the iron block. For this, the iron bloom was reheated in a smithy forge to almost white hot (>1250°C) condition and silica sand was sprinkled upon it. This reacted with the remaining FeO and helped in forming fluid 2FeO.SiO<sub>2</sub> slag which flowed out of the iron block. The iron block was taken out of the furnace and forged to increase its density. This process was repeated till the bloom was converted into 12 to 15mm square/circular rod. This refined rod containing 0.2 to 0.4% SiO<sub>2</sub> almost free from the slag inclusion was cut into 150 to 180mm long pieces and sold to the blacksmiths or 'Lohars' for reshaping them into useful objects.<ref name=":6" />
−National Metallurgical Laboratory, Jamshedpur, in India made great strides in improving the ancient iron making process and made significant contributions to the iron industry.<ref name=":4" />
+==== Quality and Yield ====
+Indigenous method of iron production took advantage of the fact that despite the high melting point (1540°C) iron oxide could be reduced to metal at a low temperature of 800°C. At a temperature of 1100-1150°C, this reduced iron flows together forming a semi-fused porous mass called 'bloom'. The bloom can be easily forged and worked. No use of flux was made in general except in the case where the ore was self-fluxing. The disadvantage was that a large amount of iron oxide passed into the slag but helped remove phosphorus in this process, if present, rendering the slag fusible. The low temperature smelting avoided the reduction of any other metal present in the ore and also diminished the danger of carburization of iron. The product was slag bearing wrought iron. It was fibrous in nature and could be easily welded and forged. Iron metal was very pure with not many other metal contaminations such as manganese and and had low levels of sulphur. However, the yield from best ore rarely exceeded 50% of iron in the ore. Generally, the yields were about 20% and the remaining was lost in slag. Wrought iron resists outside atmospheric influences better than steel as evidenced by the Iron Pillar of Delhi.<ref>Bharadwaj, H. C. ''Development of Iron and steel technology in India during 18th and 19th centuries'' in Indian Journal of History of Science, (1982) 17 (2): 223-233</ref>
+In the 19th century, National Metallurgical Laboratory, Jamshedpur, in India made great strides in improving the ancient iron making process and made significant contributions to the iron industry.<ref name=":4" />
== Wootz Steel ==
== Wootz Steel ==
−Wootz is the anglicized version of 'ukku' in the language of the states of Karnataka and Andhra Pradesh, a term denoting steel. Ample literary references suggest that the steel from southern India was the finest and once exported to Europe, China, Arab countries and the Middle East. Though an ancient material, it fulfills the description of advanced material. It is an ultra-high carbon steel of 1-2% exhibiting properties such as super-plasticity and high impact hardness.<ref name=":7">Srinivasan. S and Ranganathan. S. ''Wootz steel: An advanced material of the ancient world'' in Iron & Steel Heritage of India Ed. S. Ranganathan, ATM 97, Jamshedpur</ref>
+Wootz is the anglicized version of 'ukku' in the language of the states of Karnataka and Andhra Pradesh, a term denoting steel. Ample literary references suggest that the steel from southern India was the finest and once exported to Europe, China, Arab countries and the Middle East. Though an ancient material, it fulfills the description of advanced material. It is an ultra-high carbon steel of 1-2% exhibiting properties such as super-plasticity and high impact hardness.<ref name=":7">Srinivasan. S and Ranganathan. S. ''Wootz steel: An advanced material of the ancient world'' in Iron & Steel Heritage of India Ed. S. Ranganathan, ATM 97, Jamshedpur</ref>
Wootz steel spurred developments in modern metallographic studies. Indian wootz ingots are believed to have been used to forge Oriental Damascus swords which were reputed to cut even gauze handkerchiefs and silk. Finest swords and artefacts of Damascus steel are seen in museums today.<ref name=":7" />
Wootz steel spurred developments in modern metallographic studies. Indian wootz ingots are believed to have been used to forge Oriental Damascus swords which were reputed to cut even gauze handkerchiefs and silk. Finest swords and artefacts of Damascus steel are seen in museums today.<ref name=":7" />
Although iron and steel had been used for thousands of years, the role of carbon in steel as the dominant element was found only in 1774 by the Swedish chemist, Tobern Bergman, and was due to the efforts of Europeans to unravel the mysteries of wootz. With the aim of reproducing the South Indian wootz steel on an industrial scale, there was a spurt in interest in many European travellers in early 1800's. By 1918 Belaiew made an important finding concerning wootz steel; he was probably the first to attribute the malleability of it to the spheroidized nature of the forged steel and to recognize that this occurs during forging at a temperature of red heat (700-800<sup>o</sup>C).<ref name=":7" />
Although iron and steel had been used for thousands of years, the role of carbon in steel as the dominant element was found only in 1774 by the Swedish chemist, Tobern Bergman, and was due to the efforts of Europeans to unravel the mysteries of wootz. With the aim of reproducing the South Indian wootz steel on an industrial scale, there was a spurt in interest in many European travellers in early 1800's. By 1918 Belaiew made an important finding concerning wootz steel; he was probably the first to attribute the malleability of it to the spheroidized nature of the forged steel and to recognize that this occurs during forging at a temperature of red heat (700-800<sup>o</sup>C).<ref name=":7" />
+
+== Iron In Ayurvedic References ==
+'''Ayurvedic Properties''': Iron is sweet, astringent, and bitter in taste; cold, laxative; heavy, course, preventer of senile decay, improves eyesight, reduces fat, increaser of a little vayu in the system. It pacifies an excess of kapha (phlegm) and pitta (animal heat). It cures toxins, colic, swelling of the body, piles, spleen, anemia, obesity, spermatorrhoea and worms. Iron increases strength and longevity. It cures diseases and is an aphrodisiac. It is one of the best remedies for senility.<ref name=":8" />
+
+Rasajalanidhi,<ref name=":8" /> describes the Doshas of iron as follows
+
+लौहस्य स्वाभाविकदोषाः । natural blemishes of iron <blockquote>गुरुता दृढ़ता क्लेदः कश्मलं दाहकारिता । अश्मदोषो मलग्रहो दोषाः सप्तायसस्य तु ॥
+
+शोधितव्यमतस्तद्धि मारणीयं यथाविधि । अशोधितममारितं लौहं ज्ञेयं महाविषम् ॥</blockquote>The following are the seven natural blemishes of iron :- heaviness, hardness, mixture with foreign matters, power of causing hysteria, power of causing inflammation, evil characteristics of stone, and power of causing constipation. Iron should be properly purified and incinerated, if not done so it is equal to great poison.
+
+द्रुष्टलौहसेवनस्य फलम् । Evil effects of taking impure iron:<blockquote>षण्डत्वकुष्ठामयमृत्युदं भवेद् हृदरोगशूलौ कुरुतेऽश्मरीञ्च ।
+
+नानारुजानाञ्च तथा प्रकोपं करोति हृल्लास मवैधलोहम् ॥</blockquote>Iron, not properly purified and incinerated, gives rise to the following :-impotency, leprosy, death, heart disease, colic, stone disease, hiccough, and even augmentation of many of the diseases the patient has already been suffering from.
+
#
#
== References ==
== References ==
[[Category:Shastras]]
[[Category:Shastras]]