After refilling, magnesium oxide needs to be sintered and held at the same temperature, then allowed to cool naturally in the furnace to below 200°C before being removed from the furnace. The entire process typically takes 3–5 hours. The specific time depends on the sintering temperature and cooling rate.
Key Stages and Timeline Before Removing from the Furnace
|
Stage Time |
Description |
|
|
Sintering Holding |
1–2 hours |
Maintain at 800–1000°C to ensure sufficient recrystallization of magnesium oxide grains. |
|
Natural Cooling in the Furnace |
1–2 hours |
Forced air cooling or water cooling is strictly prohibited to prevent thermal stress cracking. |
|
Removing Temperature Control |
<200°C |
Removing from the furnace at temperatures above this may cause sealant failure or metal deformation. |
Removal can begin as early as 3 hours after the start of sintering, but it must be confirmed that the furnace temperature has dropped to a safe range and the environment is dry (RH ≤ 30%).
Precautions for unloading from the furnace:
Prohibit rapid cooling: Do not use water cooling, air cooling, or other methods to accelerate cooling, as this may cause micro-cracks between the tube shell and the insulation layer.
Moisture protection: Immediately after unloading, transfer to a drying oven or seal in packaging to prevent moisture absorption.
Subsequent testing: Cold insulation resistance and withstand voltage tests can only be performed after the tube has cooled to room temperature.
Premature unloading or excessively rapid cooling may result in substandard insulation performance, increasing the rework failure rate by over 40%.
