Roasting method of silica sol casting process

Roasting method ofsilica sol casting process
The quality of silica sol shell roasting directly affects the quality of castings in the casting. If the shell is not burned through and sintered, it will cause the bad high temperature strength variation and shell cracking, also lead to the defect of lack of casting gate,casting blowholes and casting surface cracking,ect. The silica sol casting roasting method is as below:
1,Single shell roasting
Placed in the furnace while die down and the calcination temperature is 900℃～1050℃. Start out pouring after 1 h to 2 h to the temperature preservation. If need to enchase,coming and packing with the temperature less than 450 ℃.

2,Packing roasting
Check mould quality carefully, don’t put into carton if there is the phenomenon of cavity cracking,spalling and peeling,ect.Remove runner flanging and floating sand,form the mouth down,take place around the form, clear ash, sand and dust on the surface of the cavity.With compressed air blowing off the dirt inside the cavity and fly ash on it’s surface. 100% water cleaning the mould cavity, which can reduce internal scum.Pack after gently patting wave form again,with asbestos board covering after filling sand gate with two gap of asbestos board cover sand box, in order to prevent the roasting to medium sand box leather into the shell mould casting process and casting ash.If there is a gate damaged or there is sand appears at the top, we need to stop using and can use again after repairing and inspection qualified. Less than 450 ℃ box, when box-type resistance furnace roasting to 900 ℃,it can cast after 2h insulation.