1. Raw Material Quality Control (Source Control)

Raw Material Inspection

• Batch-by-batch mandatory inspection: chemical composition, particle size distribution (D50), apparent density, flowability and oxygen content.
• Key control indicators: sulfur/phosphorus content ＜ 0.02%, particle size fluctuation ＜ ±10%; eliminate impurities and oxidation.
• Compliance standards: GB/T 1479, GB/T 5162.

Mixing Process Control

• Precise proportioning, feeding sequence, rotating speed and mixing time to prevent component segregation.
• Regular equipment cleaning to avoid cross-contamination between batches.
• Sampling inspection of mixture uniformity via spectrum analysis or metallographic testing.

2. Mold Design and Maintenance (Precision Foundation)

Precision Mold Design

• Dimensional compensation reserved according to material shrinkage rate (10%–15% for iron-based materials).
• CAE simulation to optimize cavity structure; multi-directional compaction (double-action / four-action) for uniform density distribution.
• High guiding precision (parallel tolerance ≤ 0.01mm), reasonable exhaust structure and die wall lubrication design.

Regular Mold Maintenance

• Inspect wear loss every 10,000 pieces; repair or replace molds when dimensional deviation exceeds 0.02mm.
• Ensure smooth surface, no drawing scratches and precise mold closing.

3. Compaction Process Control

Fixed Process Parameters

• Compaction pressure: 410–550MPa (iron-based materials)
• Compaction speed: ≤5mm/s; pressure holding time ≥10s
• Ejection speed: 5–10mm/s
• Servo press pressure fluctuation controlled within ±1%.

Online Sampling Inspection (every 30 minutes)

• Density: 6.8–7.2g/cm³ with allowable deviation ＜ ±0.1g/cm³
• Dimension: key dimensional tolerance ±0.05mm
• Appearance: inspect for cracks, lamination and corner missing; shut down production if defect rate exceeds 2%.

4. Sintering Process Control (Core Procedure)

Precise Control of Three Key Factors

• Temperature: controlled within ±5℃ with segmented temperature control (preheating / sintering / cooling stage).
• Holding time: 2–3 hours (adjusted by part thickness).
• Protective atmosphere: ammonia decomposition gas (H₂ ≥75%) or pure hydrogen to prevent oxidation and decarburization.

Furnace Condition Monitoring

• Real-time curve recording for continuous sintering furnaces with automatic alarm for abnormal conditions.
• Ensure stable porosity, hardness and metallographic structure of sintered parts.

5. Post-Treatment (Strengthening & Finishing)

• Repressing / Sizing: Improve density and calibrate dimensional accuracy.
• Heat treatment: Quenching, tempering and carburizing to enhance strength, hardness and wear resistance.
• Surface treatment: Oil impregnation, electroplating, PVD coating, sandblasting.
• CNC finishing: Precision machining of key positions to meet high accuracy requirements.

6. Full-Range Inspection System

• Raw material: Chemical composition, particle size, apparent density, flowability.
• Green compact: Density, dimension, appearance.
• Sintered semi-finished product: Density, hardness, metallographic structure, carbon content.
• Finished product:
  • Dimension inspection: CMM, vernier caliper, micrometer.
  • Mechanical performance: Tensile test, impact test, hardness test (per GB/T 230).
  • Defect detection: Magnetic particle inspection, fluorescent penetrant inspection, ultrasonic testing (for internal cracks and porosity).
  • Tightness test: Vacuum leak detection after oil impregnation.
   

7. Quality System & Traceability Management

• System certification: ISO 9001, IATF 16949 (for automotive and medical parts).
• Full lifecycle traceability: Electronic records of batch number, raw material batch, process parameters, inspection data and operator information.
• Continuous improvement via PDCA: Abnormality analysis, corrective & preventive measures, SOP optimization.
• Personnel training: Professional training for operation, inspection and quality awareness.

8. Common Defects and Control Key Points

• Lamination & cracks: Control compaction speed, pressure holding, lubrication and ejection speed.
• Dimensional out-of-tolerance: Mold shrinkage compensation, sintering temperature field control, sizing calibration.
• Uneven density: Adopt multi-directional compaction, uniform powder filling and die wall lubrication.
• Porosity & inclusions: Strict control of raw material purity, protective atmosphere and sufficient sintering.