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Answer any two of the following: (i) Describe the heat treatment process of normalising - Leaving Cert Engineering - Question a - 2014
Question a
Answer any two of the following: (i) Describe the heat treatment process of normalising. (ii) Distinguish between eutectic point and eutectoid point. (iii) Explai... show full transcript
Worked Solution & Example Answer:Answer any two of the following: (i) Describe the heat treatment process of normalising - Leaving Cert Engineering - Question a - 2014
Step 1
Describe the heat treatment process of normalising.
Answer
Normalising is a heat treatment process that involves heating steel to about 40°C above the upper critical temperature, typically around 880-950°C, and then allowing it to cool in air. This process serves to refine the grain structure and relieve internal stresses in the metal. Upon normalising, the microstructure transforms into a more uniform and fine-grained structure, resulting in improved mechanical properties such as toughness and strength.
Step 2
Distinguish between eutectic point and eutectoid point.
Answer
The eutectic point refers to the specific composition and temperature at which a liquid phase solidifies into two distinct solid phases simultaneously. For iron-carbon alloys, this occurs at 1140°C with a composition of 4.3% carbon, leading to the formation of austenite and cementite.
Conversely, the eutectoid point is related to a reaction that occurs entirely in the solid state. It occurs at 723°C where austenite transforms into two solid phases: ferrite and cementite, resulting in a composition of 0.76% carbon.