The core of optimizing the sintering process after magnesium oxide refilling lies in precise temperature control, ensuring a pure atmosphere, improving filling uniformity, and achieving full process traceability. The following are specific optimization solutions:
1. Upgrade Temperature Control Strategy
Adopt segmented PID temperature control: Set multiple heating curves (e.g., room temperature → 500℃ → 800℃ → 1000℃), with each heating rate ≤ 5℃/min to avoid thermal shock;
Real-time monitoring and automatic correction: Use redundant temperature measurement with dual thermocouples. The system automatically identifies deviations and adjusts to ensure furnace temperature fluctuations ≤ ±10℃;
Dynamically adjust holding time: Fine-tune the holding time according to the batch characteristics of magnesium oxide powder (e.g., particle size, specific surface area) to ensure sufficient recrystallization within 1–2 hours.
It is recommended to equip the furnace with an intelligent sintering furnace with automatic temperature-time curve recording and alarm functions to improve process consistency.
2. Enhanced Atmosphere and Environmental Control
High-purity nitrogen protection (≥99.99%): Oxygen content <100ppm, positive pressure protection throughout to prevent oxidation and carbonization;
Intelligent gas flow regulation: High flow rate (10L/min) to replace air in the initial stage, then reduced to 5L/min to maintain stability during the heat preservation stage;
Cleanroom operation: Operation in a ≤100,000 class cleanroom environment with a constant humidity of RH ≤30% to prevent dust and moisture contamination.
Impure atmosphere is the main cause of failure in the humidity test and must be strictly monitored.
3. Optimized Filling and Compaction Process
Automated Precision Powder Addition: Use a weighing feedback powder adder to ensure the filling density is controlled at 2.8–3.2 g/cm³;
High-Frequency Vibration + Hydraulic Compaction: Vibration frequency 50–60Hz, lasting 5–10 minutes, eliminates micropores;
Online X-ray Inspection: Perform X-ray scanning before sintering to confirm the absence of off-core, voids, or delamination defects.
Practice shows that when the filling density deviation is >0.2 g/cm³, the risk of breakdown increases by more than 40%.
4. Standardized Cooling and Post-processing Procedures
Natural Cooling in Furnace: Forced air cooling or water cooling is strictly prohibited; the cooling rate should be controlled at ≤3℃/min;
Exit Temperature <200℃: Prevent high-temperature exposure from causing aging of the sealing adhesive or stress release in the metal;
Multi-layer Sealing Protection: Adopt a ceramic sealing adhesive + metal sealing ring structure to achieve an IP65 or higher protection level. The cooling process accounts for 60% of the total thermal stress risk and must be controlled throughout.
