Question

Which of the following liquids is used for the formation of slurry in investment casting?

(a) Ammonium hydroxide

(b) Carbon disulfide

(c) Sodium silicate

(d) Glycerin

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Enquiry is from Precision Investment Casting in division Special Casting Techniques of Casting-Forming-Welding I

Answer 1

The correct answer is:

(c) Sodium silicate

Explanation: In investment casting, sodium silicate is commonly used to form the slurry that coats the wax pattern. This slurry, typically a mix of fine refractory material and a binder like sodium silicate, forms a shell around the pattern, which is then hardened. The wax is melted out, leaving a mold cavity for the metal casting. Sodium silicate provides a durable and stable shell structure essential for the precision of the investment casting process.

• Ammonium hydroxide: Not commonly used as a binder for investment casting slurry.
• Carbon disulfide: A toxic and volatile solvent, not suitable for slurry in investment casting.
• Glycerin: Although it has some applications as a plasticizer, it is not used in the slurry formulation for investment casting.

So, sodium silicate is the correct answer for forming the slurry in investment casting.