2 The continuous cooling curves of an eutectoid plaincarbon

2. The continuous cooling curves of an eutectoid plain-carbon steel is shown below in Fig. 2. Identify and name the final product in each case at points A, B, C, D and E. Describe the variation in the microstructure of the final products and how the microstructure influences their mechanical behavior (strength, hardness and ductility)

Solution

A) Martensite: Needle Like Structure

B) Bainite: Bainite consists of very fine and parallel needles of ferrite that are separated by elongated particles of cementite.

C) Very Fine Pearlite: Buttered Structure

D) Fine Pearlite: Finer Grain Size

E) Coarse Pearlite: Coarse Structure

Strength: A>B>C>D>E

Hardness: A>B>C>D>E

Ductility: A(Very Low)<B<C<D<E