3.1 Define tempering of steel - NSC Mechanical Technology Automotive - Question 3 - 2022 - Paper 1
Question 3
3.1 Define tempering of steel.
3.2 Give THREE reasons why the annealing process is conducted on steel.
3.3 At what approximate temperature is steel heated during t... show full transcript
Worked Solution & Example Answer:3.1 Define tempering of steel - NSC Mechanical Technology Automotive - Question 3 - 2022 - Paper 1
Step 1
Define tempering of steel.
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Answer
Tempering is a process generally applied to steel to relieve the strains, brittleness, and improve ductility induced during the hardening process. This treatment helps in stabilizing the microstructure, making the steel more usable in applications by reducing the likelihood of cracking.
Step 2
Give THREE reasons why the annealing process is conducted on steel.
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Answer
To relieve internal stresses that may have been set up during the working of the metal.
To soften steel in order to facilitate the machining process, allowing for easier shaping and forming.
To refine the grain structure of steel to improve its mechanical properties and reduce brittleness.
Step 3
At what approximate temperature is steel heated during the normalising process?
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Answer
Steel is typically heated to a temperature above the higher or upper critical temperature, specifically above the A3 line, which is generally around 800 to 900 °C depending on the carbon content.
Step 4
Identify the type of steel/iron from the spark patterns shown in FIGURES 3.4.1–3.4.3 below.
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FIGURE 3.5 below shows an iron-carbon equilibrium diagram. Label A to D.
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Answer
A: Temperature range / °C
B: AC3 line / Higher/upper critical temperature line
C: AC1 line / Lower critical temperature line
D: Carbon content / % carbon
