Question

The addition of coal dust to the green moulding sand is to improve:

• A. Permeability
• B. Surface finish
• C. Mouldability
• D. Green strength

Hint:

Adding coal dust to moulding sand enhances the surface finish of castings, reducing surface defects.

Answer 1

The Correct Option is B

Coal dust is added to green moulding sand to improve the surface finish of the castings. The primary role of coal dust is to provide a smooth surface for the moulding sand, which helps in obtaining a better surface quality on the final cast product.
- Permeability refers to the ability of air to pass through the sand, and it is not primarily affected by the addition of coal dust.
- Mouldability refers to the ease with which the sand can be shaped, and coal dust has a minimal effect on this property.
- Green strength refers to the strength of the moulding sand in its green (unfired) state, and coal dust does not significantly improve this property.
Thus, the correct answer is the improvement of surface finish due to the addition of coal dust.