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Grading Hardness Standard After Heat Treatment For M0.3-M2 Micro Screws, Low & Non-magnetic Processing Control Specification For Wearable Electronics
Grading Hardness Standard After Heat Treatment For M0.3-M2 Micro Screws, Low & Non-magnetic Processing Control Specification For Wearable Electronics
Ultra-fine micro screws have tiny thread cross-section, heat treatment directly determines service performance: low hardness leads to fast thread wear & slip after repeated disassembly, excessive hardness causes instant fracture during screwdriver tightening. Cold heading & thread rolling of austenitic stainless steel creates lattice magnetization, tiny residual magnetism reduces wireless charging power of smart watches and drifts blood oxygen sensor data, different digital products require distinct magnetism control grades.
1. Heat Treatment Hardness & Residual Magnet Flux Comparison Table Of Three Stainless Micro Screw Materials
| Micro Screw Material | Standard Post-heat-treatment HV Hardness Range | Raw Residual Magnetic Flux After Cold Working | Remaining Flux After Annealing Demagnetization | Applicable Magnetism Control Grade | Matching Wearable Device Types |
| SUS201 Stainless Micro Screw | 280~330HV | High obvious magnetism flux | Medium flux, cannot fully demagnetize | Simple digital goods without magnetism requirement | Low-cost disposable earphones, children toy electronics |
| SUS304 Stainless Micro Screw | 260~300HV | Medium-high flux, severe cold-work magnetization | Tiny trace residual magnetism | Low-magnet standard for regular wearables | Standard smart bands, Bluetooth earphones, household detectors |
| SUS316 Stainless Micro Screw | 250~290HV | Low flux, slight cold-work magnetization | Near zero magnetism | Non-magnetic standard for wireless charging & imaging equipment | High-end smart watches, blood oxygen bands, portable medical endoscopes |
2. Full Process Control For Micro Screw Heat Treatment & Demagnetization
1. Solution annealing hardness control: Cool stainless micro screws with water after 20min holding at 1050℃ to lock HV hardness range and avoid mass thread slip or fracture; 2. Post-cold-working demagnetization rule: SUS304 & SUS316 micro screws must pass alternating magnetic field annealing demagnetization; SUS201 cannot be fully demagnetized and forbidden for high-precision equipment; 3. Polishing & passivation matching: Mirror polishing + chrome-free passivation after demagnetization to remove surface processing stress, prevent later rust and stabilize low-magnet status; 4. Sorting inspection: 100% magnetic flux sampling test per batch for wireless charging micro screws, full batch re-annealing required if flux exceeds limit.
3. Mandatory Magnetism Material Selection Standard For Different Wearable Electronic Products
1. Low-cost toys & disposable earphones: SUS201 micro screws acceptable without magnetism performance requirements; 2. Regular smart bands & wired Bluetooth earphones: Standard SUS304 screws, trace magnetism after annealing does not interfere basic sensors; 3. Wireless charging smart watches & blood oxygen monitors: SUS316 low-magnet micro screws mandatory, zero residual magnetism guarantees charging & sensing precision; 4. Portable MRI supporting micro instruments: Custom low-silicon SUS316L raw material with double annealing demagnetization, delivery relative permeability ≤1.01.