Classification of Steels & Alloy Steels with Composition &Uses

Classification of Steels and Alloy Steels

There arc two main classes of steel.


This steel contains iron, carbon and small amounts of other elements. About 95% of the total world, Crude-steel output belongs to this class. It is plain carbon steel is further classified as follows:‑

a)        Low Carbon Steel in which carbon content is bellow 0.2%.

b)       Medium Carbon Steel with carbon content from 0.2 to 0.5%.

c)     High Carbon Steel with carbon content above 0.5%.

The plain carbon steel is used for structural shapes, plates, tube pipes. rods and bars, tools, wheels, axles and rails.


The steel, in which different elements are added to get a desired alloying effect. Is called alloy steel. Some important alloys of steel are:


It has the composition.

Iron = 73 to 79% Chromium = 14 to 18 % Nickel = 7 to 9 %

Stainless steel is a corrosion resistant alloy and is used in making cutlery, automobile Parts, food manufacturing machinery, surgical instruments etc.


The composition of invar is Iron = 64% and Nickel          36 %. It has low co-efficient of expansion and used for making pendulum rods, meter scales, measuring instruments.                                                                                                 •


It has the composition, Iron = 96.5 %, Nickel = 3.5 %. Nickel steel is hard and resistant to corrosion. It is used for making cables, automobiles and aeroplane parts.


The composition of silicon steel is Iron = 96 to 99%, Silicon F 1 to 4%. Silicon steel is hard and highly magnetic and is used in making magnets and transformers.


It has the composition: Iron • = 85 to 88%, Manganese = 12 to 15 %. This alloy steel is extremely hard and tough. It is used for making safes and rock-drilling tools.

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