Complete Guide to NdFeB Magnet Performance & Quality Inspection | Standard Acceptance Rules for Purchasing

Known as the king of permanent magnets, NdFeB is widely applied in motors, automation and consumer electronics. Pre-delivery inspection covers magnetic performance test and appearance check to guarantee finished device stability.

1. Core Magnetic Parameters & Test Methods

Four key indicators define intrinsic magnet quality: Remanence (Br), Coercivity (Hcb), Maximum Energy Product ((BH)max).

• Remanence (Br): The remaining magnetic flux density after saturated magnetization. Unit: Gs/T. Gauss meter is available for spot surface test, while B-H tracer delivers precise full data for formal inspection.
• Hcb & Hcj: Hcb is reverse field to reduce B to zero; Hcj determines anti-demagnetization and heat resistance. High-Hcj grades fit high-temperature working conditions.
• (BH)max: Indicator of magnetic energy storage, unit MGOe, the core standard for magnet grade classification.

Note: Gauss meter alone cannot confirm exact magnet grade. Precision orders require full demagnetization curve test via professional B-H measuring equipment. Quick sampling can be done by comparing attraction force with certified standard samples.

2. Five Major Appearance Defect Inspection Standards

Surface flaws damage coating protection and cause early rust failure:

1. Scratches: machining marks and surface abrasion;
2. Surface pits: pinholes, plating bumps and blisters prone to moisture retention;
3. Cracks: invisible inner cracks and full-body splits (rejected directly);
4. Chipped edges: missing corners and edge damage affecting assembly;
5. Coating defects: peeling, discoloration, bare substrate and rust spots. All dimension tolerance including thickness, hole size and special shape shall be checked against production drawings.

3. Curie Temperature Reference

Curie temperature is the critical point where magnetism disappears completely. Grade selection must refer to Curie value for high-temperature applications to avoid permanent demagnetization.

Summary

Systematic inspection effectively controls NdFeB quality. Based on your working temperature, assembly tolerance and application environment, we provide customized grade matching, surface coating solution, prototype and mass production with strict factory QC inspection.