Photo AI
A simplified portion of the iron-carbon equilibrium diagram is shown - Leaving Cert Engineering - Question b - 2022
Question b
A simplified portion of the iron-carbon equilibrium diagram is shown. (i) Identify the point A, and describe the transformation which occurs at this point. (ii) Id... show full transcript
Worked Solution & Example Answer:A simplified portion of the iron-carbon equilibrium diagram is shown - Leaving Cert Engineering - Question b - 2022
Step 1
Identify the point A, and describe the transformation which occurs at this point.
Answer
The point A on the iron-carbon equilibrium diagram is identified as a Eutectoid point. This is the point where pearlite changes to austenite at 0.83% carbon content and at a temperature of 723°C. The transformation occurring here is a solid to solid transformation, where the microstructure of the steel shifts at these specific conditions.
Step 2
Identify and describe the heat treatment process which occurs when 0.6% carbon steel is cooled very slowly from 1000°C.
Answer
When 0.6% carbon steel is cooled very slowly from 1000°C, the heat treatment process that occurs is known as annealing. This involves heating the steel to 1000°C and maintaining this temperature until the entire workpiece is fully heated through. The subsequent gradual reduction in temperature allows the steel to become 'soft' as it re-crystallizes the grains, thereby enhancing machinability and ductility.
Step 3
Describe one method of accurately measuring furnace temperature when heat treating steel.
Answer
One effective method for measuring furnace temperature while heat treating steel is the optical pyrometer. This device compares the intensity of light emitted from the filament of a lamp with the color of the furnace. The current flow from the lamp can be adjusted via a variable resistor to match the color from the furnace. When the filament seems to 'disappear,' it indicates that the temperature of the filament matches that of the furnace, and thus the temperature can be accurately recorded.