4.1 Define the term higher critical temperature in the heating of steel - NSC Mechanical Technology Fitting and Machining - Question 4 - 2018 - Paper 1
Question 4
4.1 Define the term higher critical temperature in the heating of steel.
4.2 FIGURE 4.2 below shows a diagram. Answer the questions that follow.
4.2.1 Identify the... show full transcript
Worked Solution & Example Answer:4.1 Define the term higher critical temperature in the heating of steel - NSC Mechanical Technology Fitting and Machining - Question 4 - 2018 - Paper 1
Step 1
Define the term higher critical temperature in the heating of steel.
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Answer
The higher critical temperature is defined as the maximum temperature to which steel can be heated to achieve its greatest hardness. At this temperature, the microstructure of the steel undergoes specific transformations that enhance its hardness properties.
Step 2
Identify the diagram shown in FIGURE 4.2 above.
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Answer
The diagram shown in FIGURE 4.2 is the Iron-Carbon phase diagram, which illustrates the relationships between temperature and carbon content in various phases of steel.
Step 3
Label structures A to G.
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Answer
A - Ferrite + Pearlite
B - Ferrite
C - Ferrite + Austenite
D - Austenite
E - Austenite + Cementite
F - Pearlite + Cementite
G - 100% Pearlite
Step 4
At what temperature should steel, with a carbon content of 1.2%, be heated for hardening?
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Answer
Steel with a carbon content of 1.2% should be heated to a temperature of 900 °C or between 900 °C and 920 °C for hardening.
