Question

Match the casting defects in Column I with the characteristic features in Column II. Column I:
P. Misrun
Q. Expansion scab
R. Pin holes
S. Hot tearing
Column II:
1. Penetration of liquid metal behind surface layer of sand moulds
2. Metal solidifies prematurely in the mould and some sections of the casting are not filled
3. Cracking because of restraint to contraction in certain areas during solidification and cooling
4. Evolution of gases during solidification resulting in porosity

• A. P–2, Q–4, R–3, S–1
• B. P–1, Q–3, R–2, S–4
• C. P–1, Q–2, R–4, S–3
• D. P–2, Q–1, R–4, S–3

Hint:

Casting defects can be remembered by keywords: Misrun → mould penetration, Expansion scab → incomplete filling, Pin holes → gases, Hot tearing → cracks due to contraction restraint.

Answer 1

The Correct Option is C

Step 1: Recall each defect.
- Misrun: Occurs when liquid metal penetrates behind the surface of sand mould layers. $\Rightarrow$ (P → 1).
- Expansion scab: Caused by premature solidification where metal does not fill certain mould sections completely. $\Rightarrow$ (Q → 2).
- Pin holes: Tiny cavities due to trapped gases during solidification. $\Rightarrow$ (R → 4).
- Hot tearing: Cracks formed due to restraint against contraction during solidification and cooling. $\Rightarrow$ (S → 3).
Step 2: Match with Column II.
- P → 1, Q → 2, R → 4, S → 3. Step 3: Verify with options.
Option (C) matches correctly. \[ \boxed{\text{Correct Answer = (C)}} \]