What is cast Iron and How it is produced ?

Cast Iron is Pig Iron re-melted and thereby refined together with definite amount of limestone, steel scrap, and spoiled castings in cupola or other form of re-melting furnace, and poured into the suitable molds required shape. It contains about 2to 4 percent of carbon , a small percentage of silicon, Sulphur, phosphorous and manganese and certain amount of alloying elements, e.g., nickel chromium, molybdenum, copper and vanadium.

Carbon in cast iron usually exists in two forms associated together : (1) as the compound cementite i.e., in a state of chemical combination and the iron is known as white cast iron, and (2) as free carbon , i.e., in a state of mechanical mixture. Carbon in the first form is called "combined carbon" , and in the latter is called grey cast iron. An Intermediate stage between these two varieties of Iron shows patches of grey in the white structure . This Iron is Mottled Iron.

The Quality of cast iron thus depends not upon the absolute amount of carbon it contains, but upon the conditions in which that carbon exists. The varieties of cast Iron in common use are :

1. Grey Cast Iron.

2. White Cast Iron.

3. Malleable cast Iron.

4. Nodular Cast Iron.

5. Chilled cast Iron.

6. Alloy Cast Iron.

7. Meehanite cast Iron.

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Mechinopedia For Mechanical Engineers

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