What are the quality standards for reworked magnesium oxide?

The industry standard HG/T 3928-2012 must be strictly followed when it comes to the quality standards for reworked magnesium oxide. The material purity, structural density, and insulation performance must all be fully met through triple verification using metallographic analysis, thermal testing, and X-ray inspection.

 

1. HG/T 3928-2012-based Chemical Composition Standard

Test Subject

Acceptance Criteria

Test Procedure

Content of Magnesium Oxide (MgO)

95% or higher

Titration of Acid-Base

Content of Active Magnesium Oxide

60% or more

Method of Hydration

Insoluble Matter in Hydrochloric Acid

≤ 0.5%

Weighing, Filtration, and Acid Dissolution

Chloride (Cl⁻)

≤ 0.02%

Titration of Silver Nitrate

Sulphate (SO₄²⁻)

≤ 0.1%

Method of Barium Sulphate Turbidity

Ignition Loss

≤ 5%

Constant Weight Method at 950°C

As the legal foundation for quality release, a CNAS/CMA certified test report must be included with every returned workpiece.

 

2. Standards for Structural and Physical Performance

Verification Method for Table Item Acceptance Criteria

After vibration and compression, the actual filling density was 2.8–3.2 g/cm³.

Grain Recrystallization Dense structure, distinct borders, and significantly enlarged grains Metallographic analysis (gold standard)

Integrity of Internal Structure X-ray inspection revealed no voids, off-center cores, or uneven density (resolution ≥5μm). Any flaw could result in tube rupture at high temperatures or insulation failure.

 

3. Performance Standards for Electrical and Sealing

Standard Test Conditions for Table Test Item Acceptance

Resistance to Cold Insulation ≥ 500 MΩ 500V DC, RH≤30%

Resistance to Hot Insulation ≥ 200 MΩ measured after 30 minutes of operation within two seconds of a power outage.

Withstand Voltage Performance AC 2000V; no malfunction after one minute in a typical setting

Air Tightness: 0.3MPa pressure testing for 30 minutes revealed no leaks. Test of underwater pressure

Hot testing is essential because it can detect hidden flaws like "passing cold but failing hot" with accuracy.

 

4. Standards for Process Control

Stage

Parameters of Control

Temperature of Sintering

1.5 hours of holding period at 900±50°C

Rate of Heating

Segmented temperature control, < 5°C/min

Protective Environment

High-purity nitrogen with less than 100 parts per million of oxygen

Cooling Technique

Forced cooling is strictly forbidden; natural cooling with the furnace is limited to less than 200°C.

To establish process traceability, it is advised to record the entire temperature curve using an intelligent sintering furnace.