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4.1 State TWO properties of the cementite structure of carbon steel - NSC Mechanical Technology Automotive - Question 4 - 2016 - Paper 1
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4.1 State TWO properties of the cementite structure of carbon steel. 4.2 What is the purpose of case hardening on a camshaft? 4.3 What is the purpose of tempering ... show full transcript
Worked Solution & Example Answer:4.1 State TWO properties of the cementite structure of carbon steel - NSC Mechanical Technology Automotive - Question 4 - 2016 - Paper 1
Step 1
State TWO properties of the cementite structure of carbon steel.
Answer
Cementite is characterized as:
- Hard: Cementite is known for its hardness, making it suitable for applications requiring wear resistance.
- Brittle: While being hard, cementite is also brittle, which can limit its applications in scenarios requiring flexibility.
Step 2
What is the purpose of case hardening on a camshaft?
Answer
The purpose of case hardening a camshaft is to:
- Ensure hardness at the surface: This allows the camshaft to withstand wear and tear during operation.
- Improve resistance against wear: This is crucial for components that experience high friction and stress.
Step 3
What is the purpose of tempering hardened steel?
Answer
Tempering hardened steel serves two main purposes:
- To reduce brittleness: This process helps to enhance the ductility of the steel, making it less likely to fracture under stress.
- To increase toughness: By tempering, the material becomes tougher, allowing it to absorb impacts better.
Step 4
Show, by means of a neat drawing, the following elements on an iron-carbon equilibrium diagram: Carbon content from 0% to 1.4%.
Answer
In the iron-carbon equilibrium diagram, mark the region from 0% to 1.4% carbon along the x-axis. This area will include various phases and transformations relevant to carbon steel, indicating the composition and phase changes.
Step 5
Show, by means of a neat drawing, the following elements on an iron-carbon equilibrium diagram: Temperature of 0 °C to 1 000 °C.
Answer
On the vertical y-axis of the equilibrium diagram, indicate the temperature range from 0 °C to 1 000 °C. This temperature scale will help identify different phases of iron-carbon alloys such as ferrite, cementite, and austenite as the temperature varies.
Step 6
Show, by means of a neat drawing, the following elements on an iron-carbon equilibrium diagram: AC₃-line.
Answer
The AC₃-line represents the upper critical temperature where austenite starts to form. On the diagram, draw a line at the intersection of temperature and carbon content that delineates the phase change from ferrite to austenite.
Step 7
Show, by means of a neat drawing, the following elements on an iron-carbon equilibrium diagram: AC₄-line.
Answer
The AC₄-line indicates the temperature at which austenite transforms to cementite. Ensure this line is clearly marked on the diagram, helping visualize the transformations within these alloy phases.
Step 8
Show, by means of a neat drawing, the following elements on an iron-carbon equilibrium diagram: Austenite structure.
Answer
The austenite region should be shaded or labeled within the temperature range above the AC₃-line. This area indicates where the metal is in the austenitic phase, which is critical for heat treatment processes.
Step 9
Show, by means of a neat drawing, the following elements on an iron-carbon equilibrium diagram: Ferrite structure.
Answer
Mark the ferrite region on the left of the diagram, indicating areas with low carbon content. This phase is known for its softness and ductility, which is important for specific applications.
Step 10
Show, by means of a neat drawing, the following elements on an iron-carbon equilibrium diagram: Pearlite structure.
Answer
The pearlite region should be located between the ferrite and cementite phases, typically around 0.76% carbon content. Indicate this area where the material exhibits a combination of strength and ductility.