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A simplified portion of the iron-carbon equilibrium diagram is shown - Leaving Cert Engineering - Question b - 2014
Question b
A simplified portion of the iron-carbon equilibrium diagram is shown. (i) Identify the regions A and B. (ii) Compare the main properties of the steel at X, which h... show full transcript
Worked Solution & Example Answer:A simplified portion of the iron-carbon equilibrium diagram is shown - Leaving Cert Engineering - Question b - 2014
Step 1
Identify the regions A and B.
Answer
Region A corresponds to Austenite, which is a phase of iron and steel that has a face-centered cubic (FCC) structure. It is stable at high temperatures and has a higher solubility for carbon.
Region B includes Pearlite and Cementite. Pearlite is a layered structure of ferrite and cementite that forms during the cooling process of steel, while cementite is a hard and brittle compound formed by the combination of iron and carbon.
Step 2
Compare the main properties of the steel at X, which has 0.3% carbon, and the steel at Y, which has 1.5% carbon.
Answer
The steel at X (0.3% carbon) is categorized as mild steel. It is characterized by the following properties:
- Ductility: More ductile, allowing it to deform under tensile stress without breaking.
- Hardenability: Does not harden significantly when subjected to quenching.
In contrast, the steel at Y (1.5% carbon) is known as high carbon steel. Its main properties include:
- Hardness: Harder compared to mild steel, enhancing its wear resistance.
- Hardenability: Will harden further when quenched, making it suitable for applications requiring increased strength.
- Machinability: Difficult to machine due to its higher carbon content, which increases brittleness.