Why hardenability of plain carbon steel is less?

hardness is defined as a resistance to plastic deformation or penatration.Hardness is defined as the ease with which hardness may be attained by quenching . It is also defined as the ability to develop maximum hardness by quenching.It is the process to have a hardened layer of marten site after quenching and also to have high hardness at same given depth.

The material which having low critical cooling rate have high hardenability.The factors which reduce critical cooling rate increase the hardenability.alloy steels have low critical temperature.

In plain carbon steels are contain not more than .5% of silicon and 1.5% of manganese.These steels are strong,tough,ductile and used in expensive materials.Increase in hardness and strength in plain carbon steel is depend upon the presence of carbon content.