The core basis for determining whether sintering after magnesium oxide refilling is successful is to ensure that the cold and hot insulation resistance tests, withstand voltage tests, and moisture tests all meet the standards of HG/T 6445-2025. The following are the specific judgment methods:
1. Key Performance Test Compliance
|
Test Item |
Acceptance Standard |
Judgment Significance |
|
Cold Insulation Resistance |
≥500 MΩ (500V DC, 25℃) |
Verifies initial insulation quality and eliminates short-circuit risk |
|
Cold Withstand Voltage Test |
AC 2000V, 1 minute, no breakdown, no flashover |
Verifies insulation layer density and high-voltage withstand capability |
|
Hot Insulation Resistance |
≥200 MΩ (Measured within 2 seconds of power disconnection after 30 minutes of rated power operation) |
Confirms stable insulation performance at high temperatures |
|
Hydraulic Test |
Insulation resistance ≥200 MΩ after 48 hours of placement in a 40℃, RH 95% environment |
Simulates high humidity conditions and verifies moisture absorption resistance |
All tests must use a calibrated 2500V megohmmeter and withstand voltage tester, and the data must be traceable.
2. Physical and Technological Characteristics of Sintering Quality
Good Grain Recrystallization: Metallographic analysis shows significantly grown magnesium oxide grains with a dense structure, free of looseness or porosity;
Uniform Filling Density: Measured density is between 2.8–3.2 g/cm³, and X-ray inspection reveals no off-core or voids;
No Thermal Stress Cracks: The metal casing shows no deformation or cracks, and the outlet terminals are well-sealed with no signs of leakage;
Strong Sealing: Ceramic sealing adhesive or metal sealing is used, achieving an IP65 or higher protection rating.
If large fluctuations in insulation resistance, flashover during withstand voltage testing, or a sudden drop in resistance after exposure to moisture are observed, it indicates insufficient sintering or uneven filling.
3. Compliance with Industry Standards and Verifiable Documentation
Factory inspection reports and material composition analysis certificates must be provided; Repair suppliers should possess compliance qualifications according to JB/T 2379-2016 and HG/T 6445-2025;
It is recommended to prioritize services from standard drafting units such as Liaoning Jiashun Technology, Dashiqiao Meier Magnesium Products, and Shanghai Industrial Zhentai Chemical.
In practice, successfully sintered heating elements can operate stably for over 15,000 hours in high-requirement scenarios such as injection molding and medical applications.
