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4.1 State TWO properties of the cementite structure of carbon steel - NSC Mechanical Technology Welding and Metalwork - Question 4 - 2016 - Paper 1
Question 4
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 Welding and Metalwork - Question 4 - 2016 - Paper 1
Step 1
State TWO properties of the cementite structure of carbon steel.
Answer
The cementite structure of carbon steel has the following properties:
- Hardness: Cementite is known for its hardness, which contributes to the wear resistance of steel.
- Brittleness: While it is hard, cementite is also brittle, making it less ductile and more susceptible to fracture under stress.
Step 2
What is the purpose of case hardening on a camshaft?
Answer
The purpose of case hardening on a camshaft is twofold:
- To ensure hardness to the surface: This treatment increases the surface hardness, enhancing wear resistance, which is vital for components like camshafts that undergo significant mechanical stress.
- To ensure resistance against wear: By hardening the surface, the camshaft is protected against abrasions and deformation over time.
Step 3
What is the purpose of tempering hardened steel?
Answer
The purpose of tempering hardened steel is:
- To reduce brittleness: Tempering allows for the redistribution of stress within the steel, minimizing the risk of fractures.
- To increase toughness: The process enhances the toughness of the steel, making it better suited for applications that require impact resistance.
Step 4
Show, by means of a neat drawing, the following elements on an iron-carbon equilibrium diagram:
Answer
An iron-carbon equilibrium diagram should include the following elements:
- 4.4.1 Carbon content from 0% to 1.4%: Graphically represent the increase in carbon content along the x-axis.
- 4.4.2 Temperature of 0 °C to 1 000 °C: Display the temperature range on the y-axis.
- 4.4.3 AC1-line: Identify and draw the AC1 line where austenite begins to form.
- 4.4.4 AC3-line: Indicate the AC3 line marking the transformation to austenite at higher carbon content.
- 4.4.5 Austenite structure: Mark the region representing austenite, which exists above the AC1 line.
- 4.4.6 Ferrite structure: Show the ferrite region on the diagram, which exists below the AC1 line.
- 4.4.7 Pearlite structure: Finally, depict the pearlite structure, located between the ferrite and cementite regions.