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Answer any two of the following: (i) Discuss the safety hazards associated with the process of case hardening; (ii) Describe the principle of induction hardening; (iii) What is pearlite? Temperature zones for heat treatment processes are shown: (i) Identify any two of the heat treatment processes at A, B or C - Leaving Cert Engineering - Question Question 1 - 2009
Question Question 1
Answer any two of the following: (i) Discuss the safety hazards associated with the process of case hardening; (ii) Describe the principle of induction hardening; ... show full transcript
Worked Solution & Example Answer:Answer any two of the following: (i) Discuss the safety hazards associated with the process of case hardening; (ii) Describe the principle of induction hardening; (iii) What is pearlite? Temperature zones for heat treatment processes are shown: (i) Identify any two of the heat treatment processes at A, B or C - Leaving Cert Engineering - Question Question 1 - 2009
Step 1
(i) Discuss the safety hazards associated with the process of case hardening;
Answer
In case hardening, there are several safety hazards to consider:
- High Temperatures: The process often involves heating the component to temperatures exceeding 900°C. Prolonged exposure to such high temperatures can lead to burns and other heat-related injuries.
- Fumes and Gases: Case hardening may generate harmful fumes, particularly when certain materials like carbon-rich compounds are used. These fumes can pose inhalation risks and should be managed with proper ventilation.
- Equipment Hazards: The equipment used, such as hot furnaces and gas jets, can be a source of mechanical hazards. It is essential to ensure they are maintained and operated safely.
Step 2
(ii) Describe the principle of induction hardening;
Answer
Induction hardening is a heat treatment process that uses electromagnetic induction to heat a metal workpiece. The component is placed inside a coil carrying a high-frequency alternating current. This generates eddy currents at the surface of the component, causing rapid heating.
As the surface reaches austenitizing temperatures, it transforms into austenite. The depth of this transformation is dependent on both the frequency of the current and the duration of exposure to the heat source. Following heating, the component can be quenched to increase hardness, producing a hard surface suitable for various applications.
Step 3
(iii) What is pearlite?
Answer
Pearlite is a microstructural feature found in steel, consisting of alternating layers of ferrite and cementite. It forms during the slow cooling of austenite and is predominantly found at approximately 0.83% carbon composition. This structure provides a good balance between strength and ductility, making it desirable for many engineering applications.
Step 4
(i) Identify any two of the heat treatment processes at A, B or C.
Answer
Based on the temperature zones shown in the diagram:
- A: Annealing or hardening
- B: Stress relieving or spheroidizing
Both processes are critical in the heat treatment of metals to achieve desired mechanical properties.
Step 5
(ii) Explain allotropy in carbon steel.
Answer
Allotropy in carbon steel refers to the ability of the steel's structure to exist in more than one form. Steel predominantly exhibits two crystalline structures: Body-Centered Cubic (BCC) and Face-Centered Cubic (FCC). BCC exists at lower temperatures, while FCC can form upon heating above the steel's upper critical temperature. This transformation affects the material's properties, including strength and ductility.
Step 6
Step 7
(ii) Outline the principle of operation for this instrument.
Answer
The principle of operation of a thermoelectric pyrometer lies in the measurement of temperature differences using two dissimilar metals joined together at a cold junction. The hot junction, exposed to furnace temperature, generates a voltage proportional to the temperature difference. This voltage is then calibrated in degrees of temperature, enabling accurate temperature readings.