The key to improving the purity of reworked magnesium oxide is to use high-purity raw materials (≥99.9%), sinter under nitrogen protection throughout the entire process, and have it tested and verified by a CNAS-certified organization. Contamination or process malfunction at any stage will directly affect the final purity.
1. Strict Control of Raw Material Purity (Source Guarantee)
Use high-purity magnesium oxide powder: Must meet ≥99.9% purity, with key impurities strictly limited:
Fe₂O₃ ≤ 0.05%
CaO ≤ 0.2%
Cl⁻ ≤ 0.02%
SO₄²⁻ ≤ 0.1%
Recommended Suppliers:
Liaoning Jiashun Technology (provides 99.95% high-purity magnesium oxide)
Dashiqiao Meier Magnesium Products (complies with HG/T 3928-2012 standard)
Batch information must be scanned and traced before raw materials enter the warehouse to prevent the mixing of low-purity or damp powders.
2. Optimize Rework Process Contamination Prevention Measures (Process Control)
Step Control Points
Environmental Control: Operate in a cleanroom with RH ≤ 30% to prevent moisture absorption and dust contamination.
Equipment Cleaning: Purge the filling and sintering equipment with high-purity nitrogen before each use.
Protective Atmosphere: Maintain a high-purity nitrogen atmosphere (≥99.99%) throughout the sintering process; oxygen content < 100 ppm.
Powder Transfer: Open-environment operation is strictly prohibited to avoid contamination from airborne moisture and particulate matter.
Nitrogen protection is crucial to prevent oxidation and carbonization reactions; oxygen content must be monitored in real time.
3. Third-Party CNAS Testing and Verification (Result Confirmation): After rework, samples must be sent to a CNAS-accredited third-party organization for authoritative testing to ensure data impartiality and traceability.
Recommended Testing Institutions:
Zhongxi Testing (Supports 22+ impurity tests, nationwide sample submission)
Wuhan Kehai Inspection Co., Ltd. (Localized service, fast report generation)
Guangfen Testing & Certification Co., Ltd. (Wuhan Branch) (Focusing on high-purity material analysis)
Required Test Items:
MgO content ≥95%
Active magnesium oxide ≥60%
Hydrochloric acid insoluble matter ≤0.5%
Loss on ignition ≤5% Test reports must bear the CMA/CNAS mark as the legal basis for quality release.
4. Establish a Full-Process Traceability File
Each batch of returned workpieces will have a unique coded file, linked to:
Raw material batch
Sintering temperature curve
Atmosphere record
Test report
This achieves closed-loop management of the entire lifecycle from raw materials to finished products, facilitating problem traceability and continuous improvement.
