A simplified portion of the iron-carbon equilibrium diagram is shown - Leaving Cert Engineering - Question b - 2019
Question b
A simplified portion of the iron-carbon equilibrium diagram is shown.
(i) Name the regions A and B.
(ii) Compare the main properties of the metal with 0.2% carbon ... show full transcript
Worked Solution & Example Answer:A simplified portion of the iron-carbon equilibrium diagram is shown - Leaving Cert Engineering - Question b - 2019
Step 1
Name the regions A and B.
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Answer
Region A is called Austenite and Region B is referred to as Pearlite and Cementite.
Step 2
Compare the main properties of the metal with 0.2% carbon at X and the metal with 1.5% carbon at Y.
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Answer
For the metal at X (0.2% carbon):
Lower hardness
Reduced strength
Easily fabricates and cuts well
Can cold form, bend, and press
Tough and ductile
Malleable
Will weld well
For the metal at Y (1.5% carbon):
Higher hardness
Stronger
Can be used after cold forming
Will harden further by heat treatment
More brittle
Poor welding performance
Step 3
Describe the point C in terms of phase change, temperature and composition.
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Answer
Point C is known as the eutectoid point. At this point, the phase change involves solid austenite transforming into solid pearlite. This occurs at a temperature of 723°C and the composition is 0.83% carbon.
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