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27. In Encyclopedia Britannica (1967 Edition, Volume 5) "cast iron" is described as follows :

"A wide range of iron-carbon-silicon alloys containing 2% to 4% carbon (much more than ordinary steels) along with varying amounts of silicon, manganese, sulfur and phosphorus. Cast iron, of which pig iron is a crude form, was the first of the ferrous metals to be cast."

28. The main varieties of "cast iron" are given as "gray iron", "white iron", "malleable cast iron" and "ductile iron". It is stated that "gray iron" is the usual form of "cast iron". The essential characteristic of cast iron is that much of the carbon is present as flake graphite, which gives it a gray-coloured fracture when broken and accounts for the name gray cast iron. The strength of gray cast iron is increased by reducing the carbon content and by alloying it with nickel, chromium, copper, molybdenum, vanadium and titanium. The alloy content of ordinary cast iron generally does not exceed 3 per cent to 4 per cent. Special types of corrosion-resistant iron are made with greater alloy contents, for example 11 per cent to 17 per cent silicon, 25 per cent to 30 per cent chromium or 20 per cent to 30 per cent nickel. The silicon content of gray cast iron is normally 1.5 per cent to 3.0 per cent. When the silicon content of gray cast iron is substantially reduced a new type of cast iron which is called white iron is produced. Chilled cast iron is a variety of white iron. Castings made out of chilled iron are used as freight car wheels and brake shoes and plowshares, pulverizer equipment parts and rolls for steel mills. Another variety of cast iron is malleable cast iron. It is used for making a variety of small or thinwalled industrial castings such as automotive, agricultural machinery and railroad equipment parts, electrical and small pipe fittings, hardware and small tools. Another variety of cast iron is ductile iron. Ductile irons are really a whole family of irons and can be heat-treated and alloyed in various ways to produce special mechanical properties and superior corrosion, heat and wear resistance and are widely used in pipe, valves, gears, dies, machinery frames, automotive crankshafts, pump and compressor bodies, metal working rolls, agricultural equipment parts and a host of other products. In Amar Roller Flour Mills v. Collector of Customs [1991] 51 ELT 613 the Customs, Excise and Gold Control Appellate Tribunal, East Regional Bench, Calcutta refers to the American Publication on Metals Hand Book (Ninth Edition, Volume I) wherein it is observed as follows :

30. In the 1974 (15th Edition) of Encyclopedia Britannica, Volume 9, it is stated that cast iron is a generic term describing a family of iron alloys containing 1.8 to 4.5 per cent. carbon and these alloys are usually made into specified shapes for direct use or for further processing by machining or heat treating. It is also stated that gray iron is produced from pig iron and scrap, or from scrap iron alone and that various additives to enhance its properties may be introduced into the cupola, after the iron is molten, or into the ladle, before pouring it into moulds. It is also stated that gray iron has become an important engineering material whose composition, structure, and physical and mechanical properties can be carefully controlled to obtain the best combination of strength and service and that its mechanical properties such as tensile strength can be improved to a moderate extent by natural aging, heat treatment followed by quenching and tempering and that its surface can be hardened by flame or induction heating. It is also stated that white iron with certain additives like chromium can be used in the "as cast" condition.

"A casting of high dimensional accuracy produced by such processes as investment casting, plaster mould, die casting, permanent mould or shell mould."

In Encyclopedia Britannica (1967 Edition, Volume 5) the process of "casting" is described as :

"The process of giving shape to or reproducing an object by pouring its material in liquid form into a mold."

33. The product obtained by the said process is also called "casting" as per the Indian Standard. Such castings can be made out of a variety of metals.