Determining whether reworked magnesium oxide meets standards requires triple verification of chemical composition, physical structure, and electrical properties. The core approach is to base it on the HG/T 3928-2012 standard, combined with third-party CNAS testing and on-site testing for a comprehensive assessment.
1. Chemical Composition Testing (Authoritative Judgment Basis) Samples must be sent to a CNAS-certified institution for chemical analysis. The testing items and qualification standards are as follows:
Testing Item Qualification Standard Testing Method
MgO Content ≥ 95% Acid-Base Titration
Active Magnesium Oxide ≥ 60% Hydration Method
Hydrochloric Acid Insoluble Matter ≤ 0.5% Filtration and Weighing Method
Cl⁻ ≤ 0.02% Silver Nitrate Titration Method
SO₄²⁻ ≤ 0.1% Barium Sulfate Turbidity Method
Loss on Ignition ≤ 5% 950℃ Constant Weight Method
Recommended Institutions: Zhongxi Testing, Wuhan Kehai Inspection Co., Ltd. Reports must bear the CMA/CNAS mark and have legal validity.
2. Physical and Structural Verification (Critical to Process Control)
Item Acceptance Criteria Verification Method
Filling Density 2.8–3.2 g/cm³ Actual measurement after vibration and compaction
Grain Recrystallization Grain growth, clear boundaries, dense structure Metallographic Analysis (Gold Standard)
Internal Structural Integrity No voids, off-center cores, or uneven density X-ray inspection (resolution ≥5μm)
Metallographic analysis is the core method for determining whether sintering is truly achieved, directly reflecting the internal state of the material.
3. Electrical and Sealing Performance Testing (Operational Reliability Assurance)
|
Test Item |
Acceptance Standard |
Test Condition |
|
Cold Insulation Resistance |
≥ 500 MΩ |
500V DC, RH≤30% |
|
Hot Insulation Resistance |
≥ 200 MΩ |
Measured within 2 seconds of power failure after 30 minutes of operation |
|
Withstand Voltage Performance |
AC 2000V, no breakdown after 1 minute |
Normal environment |
|
Air Tightness |
No leakage after 30 minutes of 0.3MPa pressure testing |
Underwater pressure test |
Hot testing is crucial, as it can identify hidden defects such as "passing cold but failing hot."
Comprehensive Judgment Process
First, perform X-ray and density screening → exclude structural anomalies;
Then, perform metallographic analysis → confirm grain recrystallization;
Finally, send for chemical composition testing + complete electrical testing → form a closed-loop verification.
It is recommended to sample at least 3 pieces from each batch, establish a unique coded file, and achieve full lifecycle traceability.
