What happens after the wax is removed from the refractory mould in investment casting?

• A. The refractory mould is heated
• B. The metal is poured immediately
• C. The pattern is reused
• D. The mould is cooled rapidly

Answer: (A)

In investment casting, once the wax pattern has been removed, the next step is to heat the ceramic shell. Heating serves to burn out any remaining wax and moisture and to bring the mould up to the temperature needed for pouring the metal. This preheating helps prevent thermal shock and ensures the metal fills the cavity smoothly, reducing the risk of cracks or other defects in the finished part.

Pouring the metal immediately isn’t correct because wax removal must be completed first. The pattern isn’t reused—the wax pattern is sacrificial—so that’s not applicable. And cooling the mould rapidly isn’t desirable, as rapid cooling can cause cracking or damage to the fragile ceramic shell.