10. Answer the questions based on the following Iron-Carbon diagram.
1) Define the single-phrase region.
2) What is the lowest possible austenitizing temperature for steel?
3) Explain the term "Eutectic point" and "Eutectoid point".
4) What are the characteristics of ferrite and cementite?
5) For a steel with 0.77% carbon, what is the final substance at room temperature?
Answer the questions based on the following Iron-Carbon diagram. Define the single-phrase
region. What is the lowest possible austenitizing temperature for steel? Explain the term
"Eutectic point" and "Eutectoid point". What are the characteristics of ferrite and cementite?
For a steel with 0.77% carbon, what is the final substance at room temperature?
Solution
1) where only one phase exists (alpha,beta,gamma,delta and liquid phase.....in this Fe-C diagram)
2)Its the A1 temperature i.e 1341 F
3) On a phase diagram the intersection of the eutectic temperature and the eutectic composition
gives the eutectic point.
On a phase diagram the intersection of the eutectoid temperature and the eutectoid composition
gives the eutectoid point.
4) Cementite , also known as iron carbide. Fe 3 C (or Fe 2 C:Fe). By weight, it is 6.67% carbon
and 93.3% iron. It has an orthorhombic crystal structure. It is a hard, brittle material, normally
classified as a c eramic in its pure form.It has a flaky structure.It is a metastable compound.
Ferrite , also known as ?-ferrite ( ?-Fe ) or alpha iron.It has a BCC structure. In pure iron,
ferrite is stable below 910