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TYPES OF CAST IRON:

 

ALLOY CAST IRON: This term designates castings containing alloying elements such as nickel, chromium, molybdenum, copper, and manganese in sufficient amounts to appreciable change the physical properties. These elements may be added either to increase the strength or to obtain special properties such as higher wear resistance, corrosion resistance, or heat resistance. Alloy cast irons are used extensively for such parts as automotive cylinders, pistons, piston rings, crankcases, brake drums and for certain machine tool castings.

CAST IRON: According to the specifications adopted by the International Association for Testing Materials, cast iron is defined as iron containing so much carbon that it is not malleable at any temperature. To conform to this definition, iron containing more than 2.2 percent of carbon is classified as cast iron. Generally, commercial cast iron, however, has a carbon content of between 3 and 4 percent. This carbon may be present as graphite, in which case the iron is known as gray cast iron.

CHILLED CAST IRON: Many gray iron castings have wear-resisting surfaces of white cast iron. These surfaces are designated by the term "chilled cast iron" since they are produced in molds having metal chills for cooling the molten metal rapidly. This rapid cooling results in the formation of cementite and white cast iron.

CUPOLA MALLEABLE IRON: The production of Cupola Malleable iron involves initially the use of a cupola or a cupola in conjunction with an air furnace. This type of malleable iron, called cupola malleable iron, exhibits good fluidity and will produce sound castings. It is used in making of pipefittings, valves, and similar parts and has the useful property of being well suited to galvanizing.

MALLEABLE-IRON CASTINGS: the annealing or graphitization of white iron castings produces malleable iron. The graphitization in this case produces temper carbon, which is graphite in the form of compact round aggregates.
     Malleable castings are used for many industrial applications where strength, ductility, machinability, and resistance to shock are important factors.

MODULAR CAST IRON (DUCTILE IRON): A distinguishing feature of this type of cast iron, also known as spheroid graphite iron, is that the graphite is present in ball-like form instead of in flakes as in ordinary gray cast iron.
    The special processing produces this spheroid graphite structure and results in a casting of high strength and appreciable ductility. Its toughness is intermediate between that of cast iron and steel and its shock resistance is comparable to ordinary grades of mild carbon steel. It exhibits good pressure tightness under high stress and can be welded and brazed.

PEARLIC MALLEABLE IRON: This type of malleable iron contains some combined carbon in various forms. It may be produced either by stopping the heat treatment of regular malleable iron during the production, before the combined carbon contained therein has all been transformed to graphite or by reheating regular malleable iron above the transformation range.

WHITE CAST IRON: When nearly all of the carbon in a casting is in the combined or cementite form, it is known as white cast iron. It is so named because it has a silvery-white fracture. White cast iron is very hard and also brittle, its ductility is practically zero.  

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