History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t12: (iv) Iron-Carbon Alloys
History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t12
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(iv) Iron-Carbon Alloys
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With the discovery of the effect of carbon on the properties of iron has begun the real industrial and cultural revolution in this World. The solid state of Iron-carbon phase diagram has been already shown and the effect of ‘C’ on the proportion of Ferrite and cementite phases in the alloy has been already discussed. Ancient Indian iron craftsmen had learnt about the role of carbon in increasing the strength and hardness of iron even as early as Vedic period if not earlier and by 8th to 12th century A.D. they were capable of producing a variety of Iron- carbon alloys as classified in Fig. 32. Yuktikalpataru a Sanskrit alchemical literature of 11 century A.D. mentions the relative properties of iron-carbon alloys as produced in different regions of India and the resulting properties of the alloy produced either due to minute difference in the smelting practice or presence of some other minor alloying elements. The description given in this literature is quoted below:
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(i) Crounca - iron supposed to be two times better than Samanya (probably Munda Loha).
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(ii) Kalinga (Orissa) - iron 8 times better than Crounca iron.
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(iii) Bhadra iron - 10 times better than Kalinga iron.
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(iv) Vajra - 1000 times better than Bhadra iron.
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(v) Pandi - 100 times better than Bhadra iron.
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(vi) Niranga - 10 times better than Bhadra iron.
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(vii) Kanta - one billion times as good as Niranga iron.
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The Indian blacksmiths had also learnt the art of heat- treatment as discussed later and their product was in great demand throughout the World. Alexander had asked 30 Seers of Indian steel as present from King Porous.
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Once the strength and properties of iron and steel were known the use of non-ferrous metals and alloys were confined only to domestic and other areas of human needs. The Indian metal craft was flourishing during the Mughal period but after the spread of the British Empire and the restrictions imposed by them in the form of production taxes and ban on export this industry died down. This disappearance of the ancient technology during 17th to 19th century was supported by the discovery of new alchemical principles and development of new industrial process of metal production in Europe. In the 20th century the condition has become so worst that the memory of ancient glory remained only in the form of stories narrated by old men and after the independence in 1947 India had to borrow the modern technology from western countries to set up steel plants and other industries.
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*(v) Other Alloys*
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Besides the above mentioned alloys many other binary and multi-component alloy compositions such as *Pañca loha* and *Aṣṭadhātu* were known to Indian craftsmen. These alloys were used for specialised purposes and their production technology were very closely guarded. Alloys or Ag-Cu-Sn etc. Sn-Pb alloy or Sn-Pb-Sb or special zinc alloy were used for producing coins, type metal, tinning alloy and Bidri ware. Amalgam or Hg-Au was used for Gold coating on brass and copper objects. Fine wires of Au, Ag and Au-Ag alloys were drawn to prepare jari thread used in a variety of embroidered silk and brocade. Silver alloy filegree ornament manufacturing craft of Orissa is famous even today.