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M3 SS304 Fastener
QS Fastener: M3 SS304 Fastener
Name: M3 SS304 Fastener
Standard: DIN933
Material: SS304
Size: M3
Lenght: 18
Surface: Natural color
Standard: DIN933
Material: SS304
Size: M3
Lenght: 18
Surface: Natural color
Quantity
M3 SS304 Fastener, compliant with DIN933, 18 mm length, natural surface finish, corrosion-resistant and high-temperature-resistant, ideal for precision electronics, medical devices and food machinery. In-stock availability; customized lengths and quantities on request. Global fast delivery helps you reduce cost and increase efficiency.
How to improve the fatigue limit of M3 SS304 Fastener
Eight technological pathways to raise the fatigue limit of M3 SS304 Fastener
(systematic guidance for design, manufacturing, assembly and service)
Eight technological pathways to raise the fatigue limit of M3 SS304 Fastener
(systematic guidance for design, manufacturing, assembly and service)
1. Material and microstructure optimisation
• Grade upgrade: replace conventional A2-70/A4-70 with high-nitrogen austenitic 1.4303N-100 (Rm≈1000 MPa) or duplex S32205-80; the fatigue limit of M3 SS304 Fastener rises by 25–40 %.
• Grain refining: lower solution temperature from 1050 °C to 980 °C, raising grain size from 5 to 8; crack-initiation resistance of Fastener improves by ~15 %.
• Zero surface decarburisation: a 0.03 % drop in surface C reduces the fatigue limit of Fastener by 20 %; protective-atmosphere continuous furnace, carbon potential 1.2 %.
• Grade upgrade: replace conventional A2-70/A4-70 with high-nitrogen austenitic 1.4303N-100 (Rm≈1000 MPa) or duplex S32205-80; the fatigue limit of M3 SS304 Fastener rises by 25–40 %.
• Grain refining: lower solution temperature from 1050 °C to 980 °C, raising grain size from 5 to 8; crack-initiation resistance of Fastener improves by ~15 %.
• Zero surface decarburisation: a 0.03 % drop in surface C reduces the fatigue limit of Fastener by 20 %; protective-atmosphere continuous furnace, carbon potential 1.2 %.
2. Thread manufacturing process
• Rolling instead of cutting: rolled threads generate 150–250 MPa residual compressive stress at the root, lifting the fatigue limit of M3 SS304 Fastener from 200 MPa to 260 MPa (+30 %).
• Rolling parameters: feed 0.6 mm/rev, rolling speed 30 m/min, single pass, root radius R≥0.144P; the stress-concentration factor K_t of Fastener falls by 40 %.
• Rolling instead of cutting: rolled threads generate 150–250 MPa residual compressive stress at the root, lifting the fatigue limit of M3 SS304 Fastener from 200 MPa to 260 MPa (+30 %).
• Rolling parameters: feed 0.6 mm/rev, rolling speed 30 m/min, single pass, root radius R≥0.144P; the stress-concentration factor K_t of Fastener falls by 40 %.
3. Surface strengthening treatments
• Shot peening: 0.3 mm stainless-steel shot, intensity 0.30 mmA, coverage ≥200 %, surface residual stress −800 MPa; fatigue limit of M3 SS304 Fastener gains another 20 %.
• Low-temperature ion nitriding: 480 °C × 6 h, case depth 15–20 µm, surface hardness 1200 HV0.1; fatigue limit of Fastener rises 25–30 %; temperature below sensitisation zone, intergranular corrosion resistance is not impaired.
• Ultrasonic rolling: 30 kHz ultrasonic impact at thread root, surface roughness Ra of M3 SS304 Fastener drops from 0.8 µm to 0.2 µm, fatigue limit improves 10 %.
• Shot peening: 0.3 mm stainless-steel shot, intensity 0.30 mmA, coverage ≥200 %, surface residual stress −800 MPa; fatigue limit of M3 SS304 Fastener gains another 20 %.
• Low-temperature ion nitriding: 480 °C × 6 h, case depth 15–20 µm, surface hardness 1200 HV0.1; fatigue limit of Fastener rises 25–30 %; temperature below sensitisation zone, intergranular corrosion resistance is not impaired.
• Ultrasonic rolling: 30 kHz ultrasonic impact at thread root, surface roughness Ra of M3 SS304 Fastener drops from 0.8 µm to 0.2 µm, fatigue limit improves 10 %.
4. Geometric design improvements
• Head-to-shank fillet: radius enlarged from 0.2 d to 0.4 d; stress-concentration factor of M3 SS304 Fastener falls from 3.2 to 2.1, fatigue life improves 2–3×.
• Relief groove: R1.5 mm under-head groove lowers peak bending stress in Fastener by 30 %.
• Flexible shank: turning the plain section to 0.8 d and increasing length by 20 % reduces stiffness of M3 SS304 Fastener, alternating stress amplitude drops 15 %.
• Head-to-shank fillet: radius enlarged from 0.2 d to 0.4 d; stress-concentration factor of M3 SS304 Fastener falls from 3.2 to 2.1, fatigue life improves 2–3×.
• Relief groove: R1.5 mm under-head groove lowers peak bending stress in Fastener by 30 %.
• Flexible shank: turning the plain section to 0.8 d and increasing length by 20 % reduces stiffness of M3 SS304 Fastener, alternating stress amplitude drops 15 %.
5. Precise preload control
• Target preload: F_p = 0.75 × R_p0.2 × A_s; for M3 SS304 Fastener, F_p ≈ 3.1 kN.
• Tightening procedure: two-step torque + 45° angle method, preload scatter of Fastener ≤ ±5 %; ultrasonic axial-force measurement error ≤ ±3 %.
• Lubrication: MoS₂ dry film, friction coefficient 0.08–0.10, torque coefficient K of Fastener stable at 0.18 ± 0.02, preload repeatability improves 25 %.
• Target preload: F_p = 0.75 × R_p0.2 × A_s; for M3 SS304 Fastener, F_p ≈ 3.1 kN.
• Tightening procedure: two-step torque + 45° angle method, preload scatter of Fastener ≤ ±5 %; ultrasonic axial-force measurement error ≤ ±3 %.
• Lubrication: MoS₂ dry film, friction coefficient 0.08–0.10, torque coefficient K of Fastener stable at 0.18 ± 0.02, preload repeatability improves 25 %.
6. Stress-amplitude control
• Lower bolt stiffness: slender or hollow shank reduces alternating stress amplitude of M3 SS304 Fastener by 20 %.
• Raise joint stiffness: switch to high-modulus gaskets or omit spring washers; alternating stress amplitude of Fastener drops 10–15 %.
• Lower bolt stiffness: slender or hollow shank reduces alternating stress amplitude of M3 SS304 Fastener by 20 %.
• Raise joint stiffness: switch to high-modulus gaskets or omit spring washers; alternating stress amplitude of Fastener drops 10–15 %.
7. Environmental protection
• Coating: Zn-Ni (12 %) alloy + transparent sealer, 1000 h salt spray without red rust; friction coefficient of M3 SS304 Fastener stabilises at 0.12–0.15, preventing fretting wear.
• Sealant: PTFE-UV-cured thread sealant isolates M3 SS304 Fastener from corrosive media, extending fatigue life in marine conditions by 50 %.
• Coating: Zn-Ni (12 %) alloy + transparent sealer, 1000 h salt spray without red rust; friction coefficient of M3 SS304 Fastener stabilises at 0.12–0.15, preventing fretting wear.
• Sealant: PTFE-UV-cured thread sealant isolates M3 SS304 Fastener from corrosive media, extending fatigue life in marine conditions by 50 %.
8. Installation and in-service monitoring
• Symmetric tightening: diagonal sequence 30 %→60 %→100 % to avoid misalignment of M3 SS304 Fastener.
• Smart washers: embedded strain gauges monitor axial force of Fastener in real time; alert when loss >15 % for re-tightening.
• Periodic re-tightening: every 5000 km or 6 months in high-vibration service, preload loss of Fastener kept within 10 %.
• Symmetric tightening: diagonal sequence 30 %→60 %→100 % to avoid misalignment of M3 SS304 Fastener.
• Smart washers: embedded strain gauges monitor axial force of Fastener in real time; alert when loss >15 % for re-tightening.
• Periodic re-tightening: every 5000 km or 6 months in high-vibration service, preload loss of Fastener kept within 10 %.
Performance summary
| Combination | Fatigue limit σ₋₁ (MPa) | Gain |
| Original (cut threads) | 160 | — |
| Rolled threads | 200 | +25 % |
| Rolled + shot peening | 240 | +50 % |
| Rolled + shot peening + nitriding | 280 | +75 % |
| Rolled + shot peening + nitriding + flexible design | 320 | +100 % |
Conclusion
By integrating “material upgrade + rolled threads + surface strengthening + geometry optimisation + precise preload”, the fatigue limit of M3 SS304 Fastener can be raised from 160 MPa to over 300 MPa, matching high-strength alloy-steel bolts of the same size while retaining the excellent corrosion resistance of Fastener.
By integrating “material upgrade + rolled threads + surface strengthening + geometry optimisation + precise preload”, the fatigue limit of M3 SS304 Fastener can be raised from 160 MPa to over 300 MPa, matching high-strength alloy-steel bolts of the same size while retaining the excellent corrosion resistance of Fastener.
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