In this article we will discuss about:- 1. Meaning of Carbon Steels 2. Elements Affecting Carbon Steel 3. Uses.

Meaning of Carbon Steels:

Carbon steel is an alloy of iron and carbon with varying quantities of phosphorus and sulphur. To this alloy is added a deoxidiser to remove or minimise the last traces of oxygen. Manganese is added to such an alloy to neutralise sulphur, either alone or in combination with silicon or other deoxidisers.

In carbon steel the maximum content of the following elements does not exceed the limits given against each:

Elements Affecting Carbon Steel:

The effect of these elements in carbon steel is given below:


(i) Carbon:

Carbon content is very important in de­termining the properties of steel. The tensile strength of steel increases with increase in carbon content up to 0.83% and beyond this it drops quickly. Hardness increases as the car­bon content increases. Ductility and weldability decrease with the increase in carbon content.

(ii) Manganese:


Tensile strength and hardness in­crease with the increase in manganese content. Weldability decreases by increase in manganese. Manganese content in steels varies from 0.2 to 0.8%.

(iii) Phosphorus:

Tensile strength and hardness in­crease with increase in phosphorus content. The phosphorus content in steels varies from 0.005 to 0.12% and the maxi­mum content permitted is 0.4%. In low phosphorus steels, phosphorus is dissolved in matrix and in others it appears as phosphide precipitate.

(iv) Sulphur:


Sulphur in steel lowers the toughness and transverse ductility. Sulphur imparts brittleness to chips re­moved in machining operations. The maximum permitted content of sulphur in steel is 0.055%.

(v) Silicon:

It is the principal deoxidiser used in car­bon steel. Presence of silicon in steel promotes increase of grain size and deep hardening properties. Its addition is very useful in making steel adaptable for case carburising. Presence of silicon varies from traces in some cases to 0.1 to 0.35% in other cases.

(vi) Copper:


Though it is not an essential constituent of carbon steel yet it is added upto 0.25% to increase the resistance to atmospheric corrosion. Other elements such as nickel, molybdenum, vanadium, cobalt etc. are present in carbon steels only in residual quantities derived from scraps.

Uses of Carbon Steel with Respect to their Carbon Content:

Uses of Carbon Steel