In the investment casting process, dewaxing and shell baking are also processes that require attention. After wax molding, coating, drying and other processes, the next step is to perform dewaxing and shell baking. Dewaxing is to heat the wax in the mould shell by means of hot water or steam to make the wax flow out of the mould shell.
When dewaxing by hot water, chemical raw materials should be added to the dewaxing water to help the shell to achieve hardening. The water temperature is generally controlled between 95℃ ~ 98℃. The dewaxing time is generally 15 min ~ 20 min.
When dewaxing is carried out by steam, it needs to be carried out in a dedicated dewaxing kettle. The steam pressure is generally controlled between 0.6 Mpa ~ 0.75 Mpa. The dewaxing time is generally 6 min ~ 10 min.
After the dewaxed shell is placed for a period of time, it can be baked. Baking needs to be carried out in a dedicated baking furnace. The working temperature of the baking furnace is generally around 1200°C. The baking temperature of the shell made of different binders is different.
After the shell is baking, the shell needs to be post-treated. These post-processing procedures mainly include: shaking the shell, washing the shell, checking for cracks and other defects. If the shell is found to be defective, the shell needs to be repaired.
After the shell is baked, it can be preheated and poured in the next step.