Plain Carbon Steel and Applications

Sere some of the applications shall again be explained after emphasising the manner in which plain carbon steels are classified. Plain carbon steels are those that contain carbon as principal alloying element. These steels might also contain small amounts of such of impurities as, sulphur, phosphorous, manganese, silicon and nickel. The sulphur & phosphorous are mostly undesirable impurities & attempts are built to keep them at as low level as possible. Their levels beyond 0.05% are not permissible.

According to carbon percentage (or microscope structure) the steel is divided into three groups.

Eutectoid Steels

Such steels have ideally 0.83% of carbon and have wholly lamellar peralite structure. In practice completely pearlite structure appears in all of steels containing approx 0.8% carbon. Moreover several alloying elements affect the carbon contents of eutectoid steels. For instance, Mn to the extent of 1% decreases carbon in the eutectoid to 0.7%.

Hypo-Eutectoid Steels

These steels have carbon between 0.08% to just below 0.83%. They have grains of ferrite together with grains of pearlite. The strength enhance with enhancing carbon content due to enhancing proportion of strong pearlite formed but ductility reduce proportionally.

Hyper-Eutectoid Steels

These steels have carbon significantly in excess of 0.8%. The structure has pearlite and cementite. Cementite forms along with the grain boundaries of pearlite as an inter-granular network and enhance brittleness.With respect to range of carbon content the plain carbon steels are divided into following groups. The carbon percentages might overlap in many cases.