Factors Affecting Physical Properties Of Steel

The physical properties of steel such as ductility, elasticity, strength, etc. are greatly influenced by the following three factors:
(1) Carbon content,
(2) Presence of impurities, and
(3) Heat treatment processes.

Each of the above factor will now be briefly described.
(1) Carbon content: The variation in carbon percentage produces steel of different grades. The carbon always assists in increasing the hardness and strength of steel. But at the same time, it decreases the ductility of steel. The mild steel having carbon content of about 0.10 to 0.25 per cent is widely used for structural work.

(2) Presence of impurities: the usual impurities in steel are silicon, sulphur, phosphorus and manganese.

If silicon content is less than 0.20 per cent, it has no appreciable effect on the physical properties of steel. If silicon content is raised to about 0.30 to 0.40 per cent, the elasticity and strength of steel are considerably increased without serious reduction in its ductility.

If sulphur content is between 0.02 to 0.10 per cent, it has no appreciable effect on the ductility or strength of steel. It however decreases malleability and weldability of hot metal. The excess of sulphur decreases strength of steel.

The phosphorus produces detrimental effects on steel. It is desirable to keep its content below 0.12 per cent. It reduces shock resistance ductility and st