Class 4 (4th Engineer) MEKG 📅 May 2023

Exam Question

(a) Grain size and inter-crystalline structure determine the properties of the metal. Name the three principal components of the microstructures of plain Carbon Steel and differentiate between them (5)

(b) Discuss the changes in the constituents with the addition of carbon in each case mentioning the percentage at which transformation take place. (5)

(c) Enlist the processes used in order to manufacture machinery components from steel Bots. What is forging and explain the types. (6)

Reference Answer

### (a) Principal Microstructures of Plain Carbon Steel (5 Marks)
The properties of plain carbon steel are determined by its microstructure, which consists of different phases and micro-constituents formed during cooling. The three principal components are Ferrite, Cementite, and Pearlite.
1. **Ferrite (α-Iron)**
* **Structure:** It is essentially pure iron with a Body-Centered Cubic (BCC) crystal structure. It can only dissolve a very small amount of carbon (max 0.022% at 723°C).

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